COMPOSITES, CERAMICS AND NANOMATERIALS PROCESSING SYMPOSIUM

Nowadays, many kinds of materials were employed as nuclear radiation shielding material, while, the requirements of radiation shielding become more and more strictly. Ionizing radiation is widely used in laboratory, industry and medicine, but poses a significant health hazards. Heavy metal based shielding materials have been commonly used for radiation protection. An attempt was made to prepare a cost effective jute-clay-iron phosphate glass-PP based composite as a potential candidate for radiation protection. Different weight percentages of clay (5%, 10%, 15%, 20%, 25% and 30% clay in clay-PP blend) was blended with polypropylene (PP) bead using extruder to prepare various composition of clay-PP blend and various mechanical properties such as, tensile strength (TS), elongation at break (Eb), tensile modulus (TM), bending strength (BS) and bending modulus (BM) were studied. Optimum clay percentage was selected as 10% clay in PP. Then PP-clay-jute composite (30 wt% jute) was prepared using this blend (10% clay in PP) by compression molding and subjected to various mechanical tests. TS, BS, TM and BM were found to be 45, 56, 620 and 1024 MPa, respectively. Iron phosphate glass (IPG) (compositions: Na2O-CaO-MgO-Fe2O3-P2O5) powder retains a substantial relative shielding efficiency while having a much lower conductivity than bulk phosphate glass. IPG powder (10 wt%) was incorporated onto jute fabrics by hand lay-up technique for shielding purposes and then jute-clay-IPG-PP composites were fabricated. Mechanical properties of both types of composites (jute-clay-PP and jute-clay-IPG-PP) were compared. It was found that the values of TS, BS, TM, BM, and IS of jute-clay-IPG-PP composite improved significantly than that of control (jute-clay-PP) composite. Jute-clay-IPG-PP composite was found 67% increase in TS and 108% increase in BS over that of the control (jute-clay-PP) composite. Water ageing and degradation tests of both types of composites were carried out. The prepared jute-clay-IPG-PP composite will highlight a new dimension to shielding material for its intrinsic properties and economic consideration.

Electrical conductivity measurements were carried out by A. C. Impedance spectroscopy respectively on 8.5 mol% yttira-stabilised zirconia(8.5YSZ) and 6.5 mol% magnesia-stabilized zirconia (6.5MSZ) within 216h annealing duration at 1100℃ in dry air. Electrical conductivities exhibited dramatic degradation with the time. Total conductivities of 8.5YSZ decreased by 44.7% while 7.5MSZ decreased by 68.3%. Grain resistance and grain boundary resistance were investigated by A. C. Impedance spectroscopy. Both grain resistance and grain boundary resistance showed significant magnification, however grain boundary resistance increased faster than grain. XRD performed for possible change in microstructure demonstrated no phase transition and precipitation of impurity. The aging effect of partial stabilised zirconia can be attributed to the transformation of defect associates of dipoles into tripoles during annealing process. The faster increased resistance of grain boundary was interpreted by the different distribution of and in grain and grain boundary.

High temperature brazing is widely applied in industry as a fast and cost-effective method for joining large components used in the aerospace and the chemical industry as well as for power generation, e. G. Compressor impellers or turbine parts. In steam turbines the valve seats and first stage turbine blades are subjected to steam oxidation and heavy particle erosion, especially when the turbine is running at higher steam temperatures in the range of 650 to 720C. However, at higher inlet temperatures the efficiency is increased and CO2 emission is substantially decreased. By CALPHAD modelling the formation of brittle phases at the interface can be predicted, especially after long-time thermal exposure. On this basis we are able to select a tailored coating with improved thermal stability at higher service temperatures. Brazing of diamond for grinding tools is improved by thermodynamic simulations. The interface between diamond and the braze alloy is prepared by Focused Ion Beam Method and analyzed by High Resolution TEM. It is demonstrated that by CALPHAD modelling the activity of Ti can be explained in different braze alloys. Thus the composition of the braze alloy as well as the processing parameters can be optimized in order to increase the life-time of the diamond brazed tools. Brazing at lower temperatures needs less energy. A new approach was applied to decrease the melting point of filler metals. Nano-multilayers of filler metal and a diffusion barrier layer were produced by DC magnetron sputtering. A significant melting point depression of 230C was achieved for a AlSi filler metal.

The method of influence on aluminum alloy structure formation by ceramic nanoparticles affecting the crystallization process was presented. Special rod modifier were prepared from the mixture of ceramic nanoparticles and aluminum powder and added to the molten aluminum alloy. These nanoparticles served as the crystallization centers. Improvement of aluminum structure formation and therefore of the mechanical properties of the alloy was demonstrated. The modification rods containing 0.01-0.1 wt. % nanoparticles, were added to A356 aluminum melt. Finer structure of this aluminum alloy was achieved by the alloying process as the result of direct influence of the nanoparticles on the metal crystallization process. Metal grain morphology, non-metallic inclusion and intermetallic phase formation changed as a result of these processes. Aluminum A356 alloy specimens were fabricated by sand casting process. Macro and micro structures, elemental composition and mechanical properties of the modified casts as compared to the non-modified were analyzed. A pronounced improvement of modified aluminum alloys elongation by 30-60% was observed while Ultimate (UTS) and Yield (YS) strengths remain unchanged.

Silicon nanoparticles have been enormously researched for new applications such as printable electronics. To make silicon nanoparticle function as a semiconducting material, doping concentration is the key factor to determine the electrical properties. Crystalline and amorphous silicon nanoparticles were doped with boron during the formations of nanoparticles using Inductive Coupled Plasma (ICP). Effects of various process conditions on microstructural and electrical properties were investigated. Boron-doped silicon nanoparticles were successively synthesized and doping concentration depends on partial pressures of borane and plasma powers. The maximum doping concentration was 5 x 1019 atoms/cm3 and sheet resistance was 800 mohm/square.

Ceramic and polymer both are considered as excellent dielectric materials. However ceramic materials have high density, rigidity and need very high temperature for forming. Whereas polymers are light weight, relatively flexible and easily processable at much lower temperature. But judicial combination of ceramic and polymer can give rise to excellent dielectric material with controlled dielectric properties which can be formed into any intricate shape more easily. The aim of the present work is to develop graded dielectric material from suitable ceramic- polymer composites. Polymer ceramic composites having controlled dielectric properties were prepared using elastomer like polydimethylsiloxane (PDMS), and ethylene-propylene-diene terpolymer, as matrix and neat titania (TiO2), heat treated titania, doped titania as well as barium titanate(BaTiO3) as fillers. Different mechanical and dielectric properties of these composites were measured. It is found that filler in general reduces the tensile strength and elongation at break. However the addition of these fillers was found to increase tear strength and hardness of composites. Both heat treatment and doping of titania has significant effect on electrical, mechanical and processing properties of these composites. The dielectric properties of these composites can be controlled through adjustment of filler concentration and filler treatment. With the increase in the concentration of different types of titania and barium titanate both dielectric constant and loss increase but resistivity decreases. The effect of poling through application of electric field on dielectric properties of these composites has also been investigated.

Carbon nanotube-based polymer composites are fast growing class of materials since carbon nanotubes exhibit a high aspect ration, unique electrical, mechanical and structural properties which contribute to utilize these characteristics for engineering applications such as actuators, hydrogen storage, chemical sensors and nanoelectronic devices. Several papers have been published utilizing CNTs as the sensing material in pressure, flow, thermal, gas, optical, mass, strain, stress, chemical and biological sensors. Amongst many of its superior electro-mechanical properties, piezoresistive effect in CNTs is attractive for sensor design. When CNTs are subjected to a mechanical strain, a change in its chirality leads to modulation of its conductance. In this paper, a novel carbon nanotube/biopolymer nanocomposite was used to develop a piezoresistive strain bio-nano sensor. A biocompatible polymer matrix has been used to provide good interfacial bonding between carbon nanotubes. MWCNT (d=30-50 nm, purity>95%) have been used for preparation of Poly(Methyl Metacrylate) based nanocomposites, PMMA/MWCNT. The PMMA/MWCNT nanocomposites were prepared via the mixing of the MWCNT and PMMA in a dichloromethane solution for 24 h. Characterization of the PMMA/MWCNTs nanocomposite films was performed by DSC, TGA, WAX, FTIR and SEM, as well as mechanical and electrical measurements. Sensor activity was followed through piezoresistive effect important for designing strain sensors. The work describes variations in CNT/polymer piezo-resistive properties when MWCNT doping concentration is varied. The results indicate that introducing MWCNT into PMMA significantly changes have been find in the properties of the obtained nanocomposites.

Continuous carbon fiber reinforced aluminum matrix composites (Cf/Al) have high properties such as high specific strength and stiffness, low coefficient of thermal expansion and high heat conductivity, therefore, they have wide potential application in the fields of avigation and spaceflight. The compressive strength is one of the most important properties of MMCs, especially for the structure components, such as the wings and fuselage of aircrafts. The 6061 Al matrix composite reinforced by M40J graphite fibres which are put along the 0° or 0° and 90° alternately directions were fabricated using pressure permeation casting method. Compressive properties were measured on INSTRON5569 electron tension tester with 1mm/min loading rate. The macro and micro morphologies of failure surfaces were observed by Olimpas microscope and S570 scanning electron microscope. The compressive strength along 0° and 0°/90° directions of two composites with different arranged fibres are 1352MPa and 584MPa, respectively, and the compression modulus are 245GPa and 120GPa, respectively, through compression test. The compressive failure process and mechanism are disscused based on the analysis of failure surfaces. Under the compression load, the fibres parallel to the loading direction are the major bearing body, and the failure models of the single 0° laminated composite and the 0°/90° laminated composite are shear break and bending break, respectively, under compression.

Liquid metallic emulsions is a new type of materials, from which monotectic alloys with dispersed (solidified) droplets can be produced, stabilized by solid particles. The theoretical emulsions stability diagram will be presented. Examples will be given for the 3 phases (two immiscible liquid metals and stabilizing particles) which are able to form stable emulsions. Also, emulsion stabilization will be discussed using in-situ precipitating solid particles / coating on the surface of liquid droplets.

AC impedance method is an important means of investigating electrical properties of solid conductive materials. Its advantages have been unanimously approved by many experts and scholars. However, so far, since without a unified parameter setting standards, test results vary considerably, even for the same sample. In this paper, using solid electrolyte NASICON prepared by sol-gel as subject investigated, two factors were studied by changing the thickness of samples and applied voltage. Results show that applied voltage has a great effect on the part of electrode. The more applied voltage, the larger double layer capacity but, the smaller charge-transfer reaction resistance. The thicker of sample，the smaller the effect of the applied voltage on the grain resistance. In order to obtain the data more accurate and to prevent electrode polarization, the applied voltage should be as smaller as possible. Additionally, the sample thickness should not too thin.

Nowadays, MMCs are widely used in different industries. Al alloys are the appropriate base metals for such applications, because of their low density, environmental resistant and good mechanical properties. In this research, fabrication and properties of A356/SiCp reinforced composite have been studied. A356 is an age hardenable casting alloy. Addition of SiC particles to this alloy improves its mechanical properties. Hence, in this work, the effect of SiC addition on precipitation hardening process was studied. It was found that the addition of SiC particles increased the maximum hardness, as well as the kinetics of precipitation process. Performing the age hardening in 185°C changed the maximum hardness from 88HB in SiC free sample to 95HB in 3% SiC contained sample. At the same time, the time interval during which the maximum hardness was obtained decreased from 9 hours to 5 hours in the presence of 3% volume fraction of SiC . By increasing the particle size of SiC from 1000 to 200 mesh, the maximum hardness value increased to 115HB. While, the time interval to achieve it didn’t change.

The surface quality of a vacuum invest cast nickel-base superalloy IN738LC was investigated after casting in ceramic mold. The casting process variables considered were the pouring temperature, section thickness and gating system. To determine the influence of various parameters visual inspection and scanning electron microscopy were performed. The results showed that with decreasing pouring temperature and section thickness the intensity of reaction decreases. Also compared to conventional top filling, bottom filing reduces surface defects. These results demonstrate that reaction between melt of super alloy and ceramic mold depends on heat concentration strongly and surface quality of investment castings will be determined by controlling the casting variables.

TiO2 substituted nickel ferrite (NiFe2-2xTixO4-x (x≤0.12)) was synthesized by solid reaction method. Scanned electron microscope and X-ray diffraction techniques were used to characterize the surface morphology and structure of NiFe2-2xTixO4-x (x≤0.12). The electrical conductivity at temperature range of 873-1223K and the anodic polarization curve in equimolar molten salt CaCl2-NaCl-0.5%wtCaO at 873K of NiFe2-2xTixO4-x (x≤0.12) were studied respectively by ac impedance and chronoamperometry techniques. Both the electrical conductivity and polarization current vary nonlinearly with TiO2 substituted amount. And NiFe1.86Ti0.07O3.93 shows the maximum polarization current and therefore has the best polarization property. The ac impedance spectra of NiFe1.86Ti0.07O3.93 in molten salt CaCl2-NaCl-0.5%wtCaO at 873-1073K were investigated. The ac impedance spectra were composed of three semicircles and were simulated by the equivalent circuit of R(Q1/R1)(Q2/R2)(C/R3). The study on the ac impedance spectra shows that molten salt CaCl2-NaCl-0.5%wtCaO wets NiFe1.86Ti0.07O3.93 well and the charge transfer process between NiFe1.86Ti0.07O3.93 and the molten salt is easy.

The purpose of the present work is working out of new electrochemical systems for joint electroreduction of tungsten, molybdenum and carbon ions. The lithium carbonate is reduced in tungstenate melts at potential - (1.0-1.3)V. Therefore, for coincidence of carbon, molybdenum and the tungsten deposition potentials for electrochemical synthesis of double molybdenum and tungsten carbides, it is necessary to management the factors influencing for carbon speed deposited. In investigated system such factor is concentration of Li2CO3. At addition a lithium carbonate in tangstenate-molybdate melts Na2WO4-Li2WO4 (20.0 pier. %)-Li2MoO4 (5.0 pier. %) a wave of carbonates-ions reduction is appearance before a wave of joint MoO42 - and WO42 – ions reduction wave. These waves coincide in one deposition wave of joint carbon, molybdenum and tungsten at increasing of lithium carbonate concentration. We carried out the electrochemical synthesis of double tungsten and molybdenum carbides from tungstenate-molybdate-carbonate melts Na2WO4-Li2WO4-Li2MoO4-Li2CO3 on the basis of voltammetry researches of joint tungsten, molybdenum and carbon ions electroreduction. The results of X-Ray analysis of electrolysis products are show the principle possibility of double carbides of molybdenum and tungsten synthesis by electrolysis of melted system Na2WO4-Li2WO4-Li2MoO4-Li2CO3.Thus, in tungstenate-molybdate-carbonate melts carried out the processes of joint electroreduction of tungsten, molybdenum and carbon ions. The structures of cathode deposits are carried out by X-Ray methods. This work is carried out with support by the program FPP «Scientific and scientific-pedagogical personnel of innovative Russia» for 2009-2013 years.

The Aurivillius-type bismuth layer-structure Sr0.84(LiHo)0.08Bi4Ti4O15 (SBT-LiHo) piezoelectric ceramics were synthesized using conventional solid state processing. Phase analysis was performed by X-ray diffraction (XRD). The dielectric, piezoelectric, ferroelectric, and electromechanical properties of SBT-LiHo ceramics were investigated. The piezoelectric activities were found to be significantly enhanced compared to SrBi4Ti4O15 (SBT) ceramics, which can be attributed to the lattice distortion and the presence of bismuth vacancies. The dielectric properties of SBT-LiHo ceramics at elevated temperatures were investigated in detail.

The information reported in this presentation pertains to improving the thermal conductivity of photo and thermally cured poylmeric materials using nanoparticle fillers. Historically, some ceramics and most polymers and rubbers have very low thermal flux capability and small enhancements in that property have been made by incorporating some inorganic or metallic fillers. A specific application that can benefit from the present research is increasing the thermal conductivity of silicone and fluoroelastomer rubbers coated on thermal fusion rollers in copy machines. Fillers examined include several morphologies and sizes of metallic particles, several types of carbon particles, one nitride and one carbide type of particles, for comparison with aluminum oxide. Regardless of filler type, particles must be well dispersed in the pre-cured resins, which property can be improved by coating the filler particles with an interfacial material compatible with the matrix. It will be shown that such core-shell fillers can induce better thermal conductivity than the cores alone.

The mechanical strength, color, porosity and shrinkage are crucial for assessing the quality of the final ceramic. In our study, a performance evaluation after firing, as well as semi-quantitative chemical analysis of two samples of sedimentary kaolin, a known sample A, from a mining area located Ipixuna-PA, and another called sample B showing staining pink, derived from outcrops roadblock in Paragominas-PA in order to characterize ceramics obtained from such clays. For each kaolin sample we made test specimens which underwent three sintering temperatures: 1050 °, 1150 ° and 1250 ° C. The sample A had a higher clearance, varying in color from pale cream to white at the higher temperatures. The linear shrinkage in this sample was higher than that obtained with sample B, however this sample B proved to possess a higher bending strength. Regarding to the color, sample B showed a gradual lightening tending to white, as well as the sample A. Therefore both kaolin samples can be applied to the formulations of white ceramics.

This paper offers an insight into the microstructural evolution of a cubic Boron Nitride based cutting tool material (50% polycrystalline cubic boron nitride in a TiCN matrix ) by using advanced analytical transmission electron microscopy methods. Owing to newly developed high resolution spectrometers and detectors, electron energy loss- spectra acquired in scanning TEM mode as a spectrum image (EELS SI), offers the possibility to find answers to increasingly thorny questions. This method produces full data sets, containing the complete spectroscopic signature with both high spatial and energy resolution. By using more sophisticated off-line processing, subnanometer localized information which may promote the understanding of the nucleation and/or elemental enrichment of different phases, can be extracted. EELS spectrum images, acquired in DualEELS mode, by using the prototype of a Gatan Quantum spectrometer mounted on a monochromated Tecnai F20 microscope, have been processed from a commercial polycrystalline cubic Boron Nitride (PCBN) sample provided by Chalmers Technical University and Sandvik Tooling, Sweden. This analytical method combined with a multiple linear least square fitting procedure enables the calculation of elemental maps containing areal and/or volumetric densities of each element bounded in different phases. Therefore, EELS fine structure and absolute edge energy information have been involved to unambiguously chart the aluminum, boron, carbon, nitrogen, titan and oxygen bounded in c-BN, TiC0.7N0.3, TiC0.5N0.5 , TiB2, Al2O3 and oxidized AlN. Moreover the oxygen present as surface oxidation of TiCN phases has been evaluated.

Bulk nanocrystalline materials have shown significant improvement in mechanical behavior as compared to microcrystalline materials of similar compositions. The enhanced properties are attributed to the strengthening from the grain refinement and from the introduction of a secondary reinforcement into the matrix. The extent of strengthening from the secondary reinforcement is greatly dependent on the dispersion of the reinforcement within the matrix and the strength of the interfacial bonding, which allows for effective load transfer from the matrix to the reinforcement, leading to improved stiffness, strength, and ductility. A two-step approach is used to produce bulk nanocrystalline materials. First, a top down approach such as high energy milling is used to fabricate nanostructured composite powders. This mechanical alloying process allows one to homogeneously disperse a reinforcement phase within the matrix while simultaneously creating a super saturated nano-grained microstructure and a clean metallurgical interface between the reinforcement and the matrix. The nanostructured powders are then consolidated by a variety of techniques, including Hot Isostatic Press (HIP) uniquely equipped with a high temperature eddy current sensor to monitor in real-time the densification of the composite powder, Microwave Sintering, and Field Assisted Sintering Technology (FAST). These novel consolidation techniques serve to minimize the exposure of the nanocrystalline composite powder to deleterious combinations of high temperatures and long soak times, thus preventing excessive grain growth and preserving the engineered nanostructure of the starting powders. We have successfully fabricated a variety of fully dense metal matrix composites with an aluminum matrix reinforced with either B4C or carbon nanotubes (CNT). The compressive strength of the Al5083-B4C composite reached 900 MPa. Metallographic and mechanical characterization has shown a good dispersion of CNTs in the final composite. The addition of 1 wt% CNT results in a 10% increase in tensile strength as compared to a pure Al baseline. This paper will discuss the effects of composition on the consolidation behavior and mechanical properties of these nanostructured lightweight composites.

The universe of dental materials has recently been expanded, especially materials cured by light. In this case high efficiency is very important. Translucent fiber post has a significant influence on the adhesive resistance values in dental procedure. Therefore high efficiency in translucent post is very important because its shows the ability to transmit light at a depth sufficient to cure resin cements. In this study, there was a quantitative assessment of luminous energy transmitted through translucent fiber posts used in dental procedure. We have obtained a high efficiency in the development and review of this whole process. After embedding the glass fiber under resin, the blocks were sectioned on a sequential machine precision at depths of 17 mm and thickness 1.4 mm, 1.6mm and 2.00 mm and were assessed for light transmission with a digital photometer. The quantitative analysis showed significant differences between the different posts. Fiber reinforced composite depends not only on the properties of fibers, but also the load on the resin matrix phase. In this case the thickness and spatial position of elements of resin drove this pathway. The values obtained revealed that the quantity of luminous energy transmitted depends on the type of post and, that for all of them, there was a significant reduction of the amount of light transmitted as the thickness decrease. It was an indicative that spatial position of resin and structure of material is very important totransmit light. Therefore, the new material created may be used to solve the cure by light because it's transmit light to depths sufficient for cure resin cements

Commercially pure titanium (cp Ti) and its alloys are classified as biologically inert biomaterials or bioinert and cannot directly bond with bone in some clinical situations. The aim of this study is investigate the bone bonding ability of a carbon-coated oxide gradient Ti implant, i. E., C-ODTi, by means of transcortical push-out tests in a 3 month experiment using a rabbit model. The pure Ti implant rods were cleaned ultrasonically in ethanol and distilled water and then a poly(vinyl alcohol) (PVA) was coated on its surface. The C-ODTi was obtained by treating PVA-coated Ti rods at 700°C for 1 h in argon. Japanese white rabbits were used and anaesthetized. Each C-ODTi was press-fitted into the prepared holes into the bone marrow. The increase in the interface shear strength reached a maximum after 24 weeks of implantation for all the evaluated materials. These results suggested that there was increased bone formation around the fabricated C-ODTi; That is, the coating of a carbon layer on the implant surface enhanced osseointegration between the bone and the implant. In summary, the fabricated C-ODTi was found to be a promising biomaterial capable of accelerating the bone formation and improving the osseointegration of cortical bone implants.

Wettability studies of the ceramic by the liquid metal are essential to the design and manufacture of metal matrix composites, MMCs. In this work, the effect of aluminum alloy composition on the variability of the surface tension using SiC-SiO2 substrates was investigated. Circular plates (Φ = 3.2cm and h=1cm) of compacted α-SiC powders coated with SiO2 were used as substrates. Four aluminum alloys – with Si/Mg molar ratios: 0.116, 0.192, 0.895 and 1.049 – were used in sessile drop tests at 1100°C, with change in the atmosphere from Ar → N2 at 1000°C. The surface tension was determined using menisci’s digital photographs, and Dorsey´s equation. The metal/ceramic interface and the drop surface were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results show that during the heating stage there is a decrease in the surface tension that ranges from 197.2 to 315.98 mN/m, and that during the holding stage a reduction as large as 513.25 mN/m can be attained. This notable outcome is attributed to the drop silicon enrichment by the dissolution of Mg2Si. And despite the low surface tension, non-wetting contact angles – ascribed to the presence of MgAl2O4 and MgO (in addition to AlN and Mg2Si) on the wrinkled drop surface – were observed.

Samples of the composite superconducting system YBCO- TeO2 were prepared using solid state reaction technique. Different weight percentages of TeO2 were added to the main mixture component for YBCO formation. The weight percentages of TeO2 is ranged from 0.0 to 4 wt% for finally prepare the composite system [YBa2Cu3O7-y]1-x(TeO2)x. The samples were cooled down from 940 oC to room temperature by two different cooling procedures: 1- slow cooling (1- 2 oC/min), and 2- direct quenching in oxygen gas in about 45 seconds. XRD analysis and temperature-resistivity measurements showed that the addition of TeO2 caused a rapid phase transformation from tetragonal to orthorhombic in a very short time upon quenching to room temperature. All quenched samples showed a phase difference between the sample outer surface (Orthorhombic) and its interior (Tetragonal). On the other hand, the slowly cooled samples did not show such a phase difference. It is mainly composed of one single orthorhombic phase. Doping the material YBCO with TeO2 led to the formation of secondary phases that co-exist with the 123 parent phase without affecting its crystal structure. Those inter-granular secondary phases led to a semi-conducting behavior in normal state and caused a gradual decrease in the samples Tc- values with increasing Te-content. It also increased the bulk densities of the samples and reduced their degree of degradation in moisture environment.

In this paper, data concerning the effect of pH towards the synthesis of dispersed Ag-TiO2 nanoparticles is reported. TiO2 nanoparticles prepared by sol gel method were coated with Ag by photo deposition under UV light. UV-Vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and N2 adsorption/desorption method at liquid nitrogen temperature (-196 C) from Brunauer–Emmett–Teller equation (BET) measurements were used to characterize the as-prepared nanocomposite particles. Ag loading of 1.25 wt% on TiO2 was achieved at different pH values ranging from 1 to 10. TEM micrographs revealed that Ag-coated TiO2 nanoparticles showed a higher degree of agglomeration at alkaline pH values. The diameter of the titania particles were in the range of 2 to 11 nm as deduced from XRD and confirmed by microscopy. A maxima in the BET surface area was achieved for the Ag-TiO2 nanoparticles at a pH of 5. Some important applications of the nanoocomposite materials will be presented.

Part I: Nanocrystalline titanium dioxide (TiO2) and nanostructured titania-based compounds with high specific surface area have a widespread range of new applications in various industries. These materials can be obtained by different wet chemistry. In particular, sol-gel techniques offer important advantages due to a low cost simple synthetic route, excellent compositional control, feasibility of producing thin films on large and complex shapes and, the most significant one, low crystallisation temperature. In the present work, an aqueous particulate sol-gel route (an environmentally friendly processing) is introduced for preparation of these compounds such as pure TiO2, TiO2-Ga2O3, TiO2-Er2O3, TiO2-Ta2O5, TiO2-CeO2, TiO2-ZrO2, TiO2-Fe2O3, NiTiO3, CdTiO3, BaTiO3, Li2TiO3, ZnTiO3, SrTiO3, barium strontium titanates and neodymium titanates. The present method is capable to tailor the crystal structure, phase composition, microstructure, crystallite size, specific surface area, packing and ordering of the products by controlling the processing parameters. It was also shown that, TiO2 nanorods can be grown into the track-etched polycarbonate membrane by a combination of this sol-gel process and electrophoretic deposition method (i. E, sol-electrophoretic method). Some of these nanomaterials were studied for gas sensing application and exhibited a remarkable response towards low concentrations of CO and NO2 gases at low operating temperature. Part II: Nanostructured II–VI semiconducting materials, including CdS, CdTe and CdSe have received great research attention because of their unique optical and electronic properties as well as their wide technological applications in solar cells. It is known that the crystal structure, phase composition and morphology of these compounds have great influence on their optical and electronic properties. In the present work, tailoring of morphology and crystal structure of these compounds by controlling solvothermal/hydrothermal processing parameters such as nature of solvent and precursor, surfactant, reaction temperature and process time is discussed. These compounds were prepared in the forms of nanoparticles, nanowires, nanorods and tetrapod crystals and were studied for solar cell application.

Transition metal-modified microporous zeolitic materials (silicate- and phosphate-based) are attractive catalysts due to their hydrothermal stability and high catalytic activity and selectivity. Metal-modified mesoporous materials with larger pore openings have been developed for catalytic processes where larger molecules are involved. The inclusion of nanosized particles of zeolitic microporous materials with larger external surface areas and high surface activity into mesoporous matrices, i. E. The preparation of microporous/mesoporous composites, substantially enhances the catalytic activity of mesoporous materials. The important feature of nanoporous solids based on a various metal oxides is also their ability to form thin films with nanometer-scale thickness. Examples of successful preparation and/or functionalisation of new nanoporous solids encompass microporous and mesoporous silicates (MnS-1, MnMCM-41, MnTUD-1), microporous and mesoporous aluminophosphates (FeAPO-36, FeHMA), microporous/mesoporous silicate composites ((Ti, Al)-Beta/MCM-41, (Ti, Al)-Beta/MCM-48, Ti-Beta/SBA-15) as well as cubic mesoporous aluminophosphate thin films. Studies of structure-property relations of new solids have included X-ray diffraction, spectroscopic (XAS, NMR) and electron microscopy characterisation techniques.

The chemical vapor infiltration using the so-called Hybrid System Chemical Vapor Deposition process (HYSYCVD) allows the synthesis and deposition of fibers, whiskers and powders at submicron- and nano-scales within the interstices of porous ceramic structures. The aforementioned process is based on the thermal decomposition of solid precursors at relatively low temperatures. The products of the decomposition react with a gas precursor such as nitrogen N2, giving place to new phases. In this work authors investigate the effect of temperature and time on the microstructural characteristics of the ZrN infiltrated and deposited within silicon carbide (SiC) porous performs. The solid-gas precursors are K2ZrF6 and N2, respectively.

The effect of two major elements – Si and Mg –, on the wettability and the resulting microstructure of Al/SiC composites has been discussed extensively in previous literature. Of prime importance is the beneficial role of silicon in enhancing wetting and preventing the attack of SiC by liquid aluminum. The latter effect, however, has been obtained by the use of SiO2 instead of elemental Si. Intense research work has shown recently that rice-hull ash (RHA) can be used as a means for supplying silicon to the system and that the MgAl2O4 phase is produced with Mg containing aluminum alloys. Nonetheless, variations in the content of Si and Mg in the Al alloy, can lead to alteration of the microstructure, and consequently, to variations in physical and mechanical properties. In this work, a study on the effect of Si and Mg content on the microstructure and mechanical properties of Al/SiCp composites prepared with RHA has been carried out. SiCp/RHA preforms were infiltrated with Al alloys with varying amounts of Si and Mg. The results show that although density is not significantly affected, the hardness of the composites increases while the magnitude of the elastic modulus (E) decreases with augment in the Si/Mg molar ratio. This result is ascribed to the residual porosity in the composites.

In recent years, the concept of “composite materials” has been revolving around a number of research projects and technological developments. This is because many scientists and technologists have recognized the essentials and the benefits behind this seminal concept. Accordingly, a countless number of research articles in the fields of metals and ceramics involve the term “composite”. And although it has to be recognized that there has been significant progress in many areas by the development of new composite materials, in many respects the concept has been exploited only partially or even more, used erroneously, because sometimes a simple mixture of materials has been referred to as a composite. The problem is not in making the mixture, but in the lack of distinguishing the matrix from the reinforcement or reinforcements, or in demonstrating what phase reinforces what other phase. Furthermore, with the advent of the field of nanoscience and nanotechnology, both terms have been combined to give place to a new class of materials named “nanocomposites”. The aim of this contribution is to review the essentials behind the concept of composite materials and highlight the recent developments in the processing and characterization of metal and ceramic matrix composites going from the macro- to the nanometric-scale. The goal is to consider materials for both, structural and functional applications, and a broad range of processing routes embracing solid, semi-solid, liquid and gas state routes, and including from the traditional to the most recent and advanced methods like powder metallurgy, stir casting, CVD/CVI, sol-gel, etc. Future perspectives for some of them are also outlined.

The effect of anode microstructure and its corresponding electrochemical performance is investigated. Two distinctive anode microstructures were fabricated by using inkjet printing. One has conventional microstructure made by printing suspension inks of CGO/NiO (50wt%:50wt%), whereas the other one has fine CGO coating dispersed evenly on the surface of NiO. The latter microstructure was made by printing CGO Sol based ink on a pre-deposited NiO (700nm powder, 10µm in thickness) functional layer. AC impedance test were conductive on a symmetrical cell under hydrogen. The result reveal fine CGO coated anode has much lower polarisation due to a larger triple phase boundary per volume. The result shows inkjet printing technique provides a cost effective route for SOFC processing.

There is a great interest in oxygen production according this fact that oxygen is an important common-used in chemical industry. Currently, oxygen is usually produced by cryogenic distillation or pressure swing adsorption, which is a very costly method. Perovskite ceramic membrane technology is good alternative which is more economical. In addition, the technology is compact and modular, and thus allows use in remote places. The general structure of the perovskite mineral is ABO3 (where A is rare and alkaline earth metal cation and B is a transition metal cation) which can be mixed oxygen ionic and electronic conductors (MIEC). In the ceramic membrane process , when a gradient of oxygen chemical potential is imposed across these dense membranes at high temperatures, oxygen is transported in the form of oxygen ions from the high partial pressure side to the low partial pressure side and released downstream without the need of electrodes and external electrical loadings, which makes the system very simple. In this work a tubular perovskite membrane was prepared which posses more effective area in comparison to the disk type and is industrial applicable. BSCFO powder was synthesized by an EDTA-citric acid process and formed to the tubular shape via gelcasting method. Gelcasting is a method with a short forming time, high yields, high green capacity and low-cost machining, and has been used to prepare high-quality and complex-shaped dense/porous ceramic parts. Oxygen permeation through these membranes was studied by the GC method using a high-temperature permeation cell. This membrane was used successfully for oxygen separation at high temperatures. High permeation fluxes were achieved. The oxygen permeation flux was determined at different oxygen partial pressures of upstream and different temperatures between 750 and 950oC. The effects of air flow rate and sweeping helium flow rate on the oxygen permeation were also investigated.

Introduction: Teeth hypersensitivity is a common condition amongst large population worldwide. It is a lifestyle related condition, resulting from the progressive loss of mineral phase from enamel surface. Unlike bone, enamel cannot regenerate itself and, therefore, the softer underlying tissues dentin can be easily removed and modified by abrasion and acid erosion, respectively. Progressive erosion of enamel eventually exposes dentinal tubules to the external stimuli in the oral environment, causing movement of the fluid within these tubules stimulating the nerves in the pulp, which is the origin of pain. Treatments can be achieved by sealing the tubules using calcium hydroxide, laser and commercial brands of toothpaste such those containing hydroxyapatite, however, current treatments are neither permanent nor ubiquitous in terms of providing a solution for the dental condition as recurrence of sensitivity is commonly reported. Proposed novel concept: The project focuses on a novel concept of photo activation of calcium phosphate minerals, using both CW and pulsed laser for developing a clinical methodology for the treatment of sensitive teeth. In my PhD research, I am engineering photoactive calcium phosphate minerals, which can be applied in vitro onto hypersensitive mimicked teeth surfaces and then superficially sintered by controlled laser irradiations to form a new layer of minerals (hydroxyapatite) to completely occlude and seal dentinal tubules. The thermal load from a chosen laser is expected to induce phase transition and densify the new mineral phase over dentin surface with acid resistant material permanently, and therefore, preventing further erosion and subsequently hypersensitivity. Experimental work: Photoactive calcium phosphate powders were synthesized at room temperature by the chemical precipitation method, via the addition of Er2O3 and Tm2O3, while AlPO4 and CaF2 were added in attempt to improve the thermal stability and acid resistance. Undoped calcium phosphate powders were also prepared as control samples. Calcium phosphate particles/alcohol suspensions were prepared for in vitro teeth cross sections coating trials using clinically extracted human molar teeth, which were followed by laser irradiation trials. Pellets of calcium phosphate powders and treated teeth cross sections were characterized using scanning electron microscopy (SEM), X-Ray diffraction (XRD), thermogravimetric (TG) and micro-hardness analyses techniques. Results and conclusions: XRD patterns of undoped calcium phosphate show a pure monetite phase in good agreement with JCPDS card number 01-089-5969, while doped calcium phosphates show a modified monetite phase, possibly with shifted peaks as well as new peaks. XRD of AlPO4 doped calcium phosphate show peak intensities reduction and the emerging of new peaks as well as the presence of an amorphous phase compared to undoped calcium phosphate. On the other hand, Er2O3 - AlPO4 doped calcium phosphate show the modification of the major peaks in the monetite phase with a significant peak intensities increase and peak shifting. Changes in the monetite structure observed by XRD were confirmed by SEM, which show the change in the morphology of the monetite particles. The occlusion of dentin surfaces with all powders was satisfactory as the post laser irradiation should form new phase layer and seal the tubules as proposed. The addition of rare earth compounds seems to be a promising route for producing photoactive calcium phosphate minerals, which was demonstrated by the initial laser irradiation trials and resulted in a sintered area and morphology change of particles. AlPO4.Er2O3.CaF2 doped Calcium phosphate, shows a rosette particles growth and the occlusion of a large area of dentin surface. In addition, all doped calcium phosphates showed better thermal stability and increased harness of teeth sections.

Biocompatible and biodegradable polymers became very important and gained a lot of attention from both biomedical and ecological outlook in the past decade(1). Among most popular and important biodegradable polymers are aliphatic polyesters (2,3) such as poly(3-hydroxybutyrate), poly (ε - caprolactone), poly(glycolic acid) and poly(lactic acid) (PLA), whereby PLA received the most attention due to its renewable resources, biodegradation, biocompatibility as well as excellent thermal and mechanical properties. In this work PLA/ZnO nanoparticle composites were studied as a function of the ZnO weight percentage (1,2 and 5 wt%) in relation to the use of PLA. The resulting composites were characterized by DSC, TGA measurements, and FTIR spectroscopy. The morphology of the PLA/ZnO nanocomposite films and the distribution of the ZnO nanoparticles were also characterized. The antibacterial activity of the PLA/ZnO films were examined against Gram-negative and Gram positive bacteria.

The preparation and property of liquid gallium based temperature sensitive functional fluid dispersing silica-coated FeMB (M = Nb, V) nanoparticles were discussed. The composition, morphology and magnetization of FeMB nanocrystalline prepared by chemical method were investigated. The nanoparticles were in the size range of 30 - 50 nm and the 0.74T saturation magnetization at 293K. A shell of SiO2 that was a thickness of about 10 nm on particles was observed by coating of tetraethyl orthosilicate (TEOS). The magnetization of the synthesized particles and fluid shows a temperature dependency within the testing temperature range of 293 - 353 K, which indicated their application potential in energy exchange devices. Silica coated iron alloy particles were dispersed into liquid gallium in the solid fraction of 0.3 mass %. The prepared fluid magnetically responded on temperature and was well heat convection fluid. The movement of gallium based fluid under the influence of the magnetic field with a magnetic field gradient was observed at various temperatures. The velocity of fluid flows in the pipe at 318K of heater temperature was at about 10mm/s and the Reynolds number was estimated as a laminar flow.

In this work, Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) was synthesized by solid state reaction method, and the investigation for using it as cathode material for protonic ceramic fuel cells (PCFCs) with Y-doped BaZrO3 as electrolyte was performed. The structure of the samples was identified by X-ray diffraction analysis. The morphology was evaluated by scanning electron microscope. The results revealed that BSCF single phase was obtained after being synthesized at 900 oC and 1000 oC from binary oxides, and carbonates. BSCF powder with appropriate particle size about 2 μm for cathode application was obtained after ball-milling and a subsequent decantation. Referring to the compatibility between BSCF and BZY20, when the firing temperature was lower than 900 oC, no formation of other phase was observed. A PCFC cell with electroless-plated Pd as anode, and BSCF as cathode was also fabricated. By evaluating the fuel cell performance, open circuit voltage of 0.981 V, and peak power density of 4.7 mW cm-2 were obtained. Our trial for complex oxides just started to develop cathode in PCFCs. Better performance will be presented in the symposium with detailed analysis of the electrode resistance.

Fuel cells can produce electricity from hydrogen, “and” produce hydrogen from electricity using the same devices. Therefore, once a hydrogen network in each town is established in the near future, hydrogen will work as the energy-storing medium. For such a scheme, we believe that fuel cells using high temperature proton-conducting oxide, called in the literature PCFC (Protonic Ceramic Fuel Cell), is the best choice among the reported various fuel cells because (1) it can be operated in an intermediate temperature range of 400 to 600 C, and (2) at steam electrolysis and fuel cell operation, the hydrogen generation (or consuming at fuel cell) electrode and steam feeding (or generation) electrode are different. The former feature may allow to the use of inexpensive catalysts and common structural materials, such as stainless steel. The latter is the advantage over SOFC (solid oxide fuel cell), which uses an oxide ion conductor. We are now investigating on trivalent cation-doped barium zirconate, which is a typical proton-conducting ceramics. We review the electrolyte properties and state of art on the electrode material.

Influence of different rare-earth oxide sintering additives (La2O3, Nd2O3, Y2O3, Yb2O3 and Lu2O3) on the microstructure and mechanical properties of hot-pressed silicon nitride/silicon carbide micro/nano-composites has been investigated. The results were subsequently compared to those obtained on the Si3N4 monoliths sintered with the same rare-earth oxide additives. The bimodal character of microstructures was observed in all studied materials where elongated β-Si3N4 grains were embedded in the matrix of much finer Si3N4 grains. The fracture toughness values increased with decreasing ionic radius of rare-earth elements in both monolithic and composite systems. Similarly, the hardness and bending strength values increased with decreasing ionic radius of rare-earth elements. The composite materials exibited lower fracture toughness due to their finer microstructure. The positive influence of finer microstructure of the composites on strength was not observed due to the present defects in the form of SiC clusters and non-reacted carbon zones. Wear resistance at room temperature also increased with decreasing ionic radius of rare-earth element in both kind of materials. Mechanical wear (micro-fracture) and tribochemical reaction were found as the main wear mechanisms in all investigated materials. Significantly improved creep and oxidation resistance were observed in the case of composite materials and/or materials with smaller radius of RE3+.

This paper investigates the role of nanocrystalline grain size and effect of Zr addition in the oxidation resistance of Fe-based alloys. Nanocrystalline (nc) Fe-xCr-5Ni-2Zr and Fe-xCr-5Ni {x = 2, 4, 7, 10} alloy pellets, with grain size 50-60 nm, have been synthesized by mechanical alloying route. A novel multi-step hot-compaction process has been investigated for the consolidation into close to 100% dense nc pellets that were found to have a high hardness (8 GPa) and reasonable ductility under shear stress condition. The addition of 2% Zr improves the grain size stability upto a temperature as high as 1000^oC, which can be attributed to particle pinning as well as reduction in grain boundary energy due to Zr segregation. The high temperature oxidation resistance of these alloys has been studied vis-a-vis conventional mc stainless steel alloy at 500^oC for 100 hours. The kinetics of oxidation was found to be parabolic in nature. The oxide layer, as characterized by SIMS depth profiling and FIB/SEM, was found to be 0.8-1.2 μm in thickness, consisting primarily of Cr₂O₃ in case of both mc and nc Fe-Cr-Ni alloys. However, in case of the Fe-Cr-Ni-Zr alloys, the oxide layer comprised of Cr₂O₃ as well as Zr₂O₃ resulting in an improved oxidation resistance of Zr containing alloys.

Influence of different rare-earth oxide sintering additives (La2O3, Nd2O3, Y2O3, Yb2O3 and Lu2O3) on the microstructure and mechanical properties of hot-pressed silicon nitride/silicon carbide micro/nano-composites has been investigated. The results were subsequently compared to those obtained on the Si3N4 monoliths sintered with the same rare-earth oxide additives. The bimodal character of microstructures was observed in all studied materials where elongated β-Si3N4 grains were embedded in the matrix of much finer Si3N4 grains. The fracture toughness values increased with decreasing ionic radius of rare-earth elements in both monolithic and composite systems. Similarly, the hardness and bending strength values increased with decreasing ionic radius of rare-earth elements. The composite materials exibited lower fracture toughness due to their finer microstructure. The positive influence of finer microstructure of the composites on strength was not observed due to the present defects in the form of SiC clusters and non-reacted carbon zones. Wear resistance at room temperature also increased with decreasing ionic radius of rare-earth element in both kind of materials. Mechanical wear (micro-fracture) and tribochemical reaction were found as the main wear mechanisms in all investigated materials. Significantly improved creep and oxidation resistance were observed in the case of composite materials and/or materials with smaller radius of RE3+.

Phase diagram models of system CaO-Al203-SIO2 sometimes may contain essential deformations, including the disruption of diagram topological structure, in accordance with the applied tasks solving. In particular, the immiscibility surface and four liquidus surfaces (3CaO*SiO2, 3CaO*2SiO2, 3CaO*Al2O3, CaO*6Al2O3) are absent in V. Danek's model . The model calculated by the thermodynamics software CaTCalc doesn't include three liquidus surfaces (3CaO*SiO2, 3CaO*2SiO2, 5CaO*3Al2O3). Our model, containing all geometrical elements (15 liquidus surfaces, immiscibility surface, 80 ruled surfaces, 16 horizontal complexes at the temperature of invariant points and 16 vertical planes of triangulation) and taking into consideration the peculiarities of liquidus surfaces structure, makes possible to consider all concentration fields and phase regions structures, to calculate the phases trajectories during solidification, to design the microstructures for any mass center at the given temperature and so on. The kinematical method of phase regions boundaries description on the experimental and calculation data is used for phase diagram model simulation. An initial data are defined by the coordinates of binary and ternary points, liquidus surfaces contours and curvatures. Considered system is characterized by 16 invariant transformations (nine – quasiperitectic ones, six – eutectic ones and one transition with the regrouping of two polymorphic modifications) and includes 33 two-phase and 46 three-phase regions. Obtained model may demonstrate the results of melt solidification within 117 two-dimensional, 163 one-dimensional and 45 zero-dimensional concentration fields. Compare: No more then 10 crystallization paths have been considered in the traditional tutorials and handbooks on materials science for the system СaО-Аl2О3-SiО2 . The computer model using allows to analyze the crystallization path for any concentration field. The crystallization stage also can be illustrated on the material balance diagrams: Vertical - for the given composition, and horizontal – as isothermal states of isopleth.

The analysis of 1-octanol–, cyclohexane– and chloroform (CHCl3)–water partition coefficients Po–ch–cf allows calculating molecular lipophilicity patterns (MLPs), which show that for a given atom logP is sensitive to functional groups. Program CDHI cannot properly differentiate between non-equivalent atoms. The most abundant single-wall carbon nanotube (SWNT), (10,10), presents consistency between a relatively small aqueous solubility and large elementary polarizability, Po–ch–cf and kinetic stability. A class of non-hydrogen-bonding Lewis bases with good solubility is found. The SWNTs in some organic solvents are cationic while in water/Triton X-100 (TX) are anionic. A group of eight new solvents, two superacids and nitric acid (HNO3) behaves as best solvents. Categorized solubility is semiquantitatively correlated with solvent parameters. Solvochromic term b correlates positively while permittivity and volume correlate negatively. The electron affinity of D-glucopyranoses (D-Glcpn) suggests aqueous colloids of anionic SWNTs. Dipole moment for D-Glcpn-linear increases until n = 4 in agreement with an 18-fold helix. The Inz– and SWNT– form inclusion complexes with cyclodextrin (CD) and amylose (Amy). Starch, D-Glcp, CD and Amy are co-solvents of SWNTs. Unperturbed guests–hosts expand the central channel. Composites and conducting/antistatic coatings are some of the most sought-after applications of nanotubes. Homogeneous, stable and spontaneously formed solutions of unmodified nanotubes should be a welcome starting material. Poly(vinyl alcohol) composite films present improved mechanical properties when compared to the pristine polymer. Another development is the possibility to functionalize selective and stoichiometrically the nanotube walls, in the same way as in the early days of C60 chemistry where C60Rn molecules could be selectively obtained from C60n– solutions. Adjusting the charge on the nanotubes one could precisely monitor the amount of attached functional groups on them. The results place nanotube processing onto a solid scientific ground and encourage the engineering of macroscopic nanotube materials.

Currently there is a sharp increase in hafnium oxide demand due to its growing consumption in several branches of modern technology. HfO2 has important technological applications as catalyst support, gate dielectric in metaloxide semiconductor devices, oxygen detectors, high temperature fuel cell electrolytes and optical fibers. One of widely used methods of hafnium oxide synthesis comprises precipitation of hydrated hafnium hydroxide from aqueous solutions and subsequent thermal treatment. However, the mechanism of the process was never studied in detail, and the data concerning the phase composition and the transformation temperatures are contradictive. In the present work the results of complex studies of the processes taking place during hafnium oxide preparation are described. The experiments included thermal and phase analysis, vibration spectroscopy and determining specific surface area. Thermogravimetric (with on-line mass-spectroscopy analysis of the gas phase) and simultaneous differential thermal analysis (SDTA) of hydrated hafnium hydroxide samples was carried out with the heating rate of 10 °С/min and air flowing through the furnace. The total sample weight decrease was 85 %, with 99 % of water removed up to 250 oC. There were two endothermic effects (maxima at 131 and 235 °С) and one intense exothermic peak (at 555 °С). The endothermic effects were accompanied by water and carbon dioxide evolution. The heat effects of the endothermic processes (145.7 and 21.9 J/g) and the exothermic transformation (95.7 J/g) were determined using differential scanning calorimetry. The nature of water and carbonate-species present in the samples was determined using high temperature infra-red spectroscopy measurements. It was shown, that the non-structural water evaporates at the first stage resulting in the formation of HfO(OH)2 (or Hf4O4(OH)8) after 200 °С. Further heating leads to HfO2. Changes of the phase composition upon heating were studied using high temperature X-ray powder diffraction analysis in the temperature range from 20°С to 950 °С with heating rate of 10 °С/min. At 540-560 °С the formation of a metastable tetragonal hafnium oxide phase was noticed. The temperature of its formation agrees well with results of SDTA and DSC measurements. Increasing temperature to 730-750 °С led to the appearance of monoclinic HfO2. Further raising the temperature resulted in gradual increasing the amount of monoclinic phase and decreasing the fraction of the tetragonal phase. Cooling heated samples of monoclinic HfO2 did not produce any tetragonal phase, the phase transformation is irreversible. Thus, the following stages of hafnium oxide formation were determined: Two step dehydration of hydrated Hf(OH)4 (removal of structural water and decomposition of HfO(OH)2), crystallization of metastable tetragonal HfO2 and its irreversible transformation to the monoclinic phase.

Most forestry activities result in large amounts of by-product, which are often treated as waste and sent to landfill. For example, in Australia the eucalyptus and pine tree silviculture industries generate as much as 150 cubic meters of empty pinecones, on an annual basis. These by products are under-used, often found in Christmas decorations, garden mulching or otherwise incinerated, as their disposal in landfill is prohibitive, through sheer volume. The focus of this research is to find the most suitable forestry by-products, adhesives and technologies in Australia to develop sustainable materials for making furniture. These by-products are perfectly suited to the manufacture of panels, as they come clean and dry after processing, and present excellent physical properties when exposed to high humidity environments, particularly when compared to softwood. This makes them particularly suited to applications such as panel furniture in high moisture environments, including kitchen and bathroom sink countertops or drawers where dimensional, swelling and adhesive problems are often an issue. This paper presents results of research into panels made from forestry by-products in Australia, identified as being particularly abundant and underused. The matrices of these composite materials have been chosen from recycled, non-toxic and organic bonding agents, being castor oil and polypropylene adhesives. The main physical properties of the panels are measured and compared with mixes already available in the market. The results show that these new materials compare very well with commercially available counterparts, exceeding their performance in several cases, particularly with respect to water absorption and thickness swelling. These new panels have the potential to become a sustainable replacement option for high-humidity environment furniture panels, made with waste resources.

Colloidal systems offer opportunities for synthesizing a wide variety of morphologies, structure and compositions of inorganic materials, such as oxides, with novel physical and chemical properties. Using examples methods of synthesising and the resulting properties are discussed. Synthesis of TiO2 nanoparticles from a colloidal system as a function of pH followed by crystallization of anatase, rutile and brookite crystal structures are discussed with respect to the critical nuclei size and coalescence [1,2]. As demonstrated for the bismuth titanate family, morphologies can be varied from nanospheres, nanoplates, nanorods, nanowires and nanowires to coalesced chop-sticks, microflowers and microspheres by controlling the colloidal processes that can be used in piezoelectric, sensing or photovoltaic applications[3-6]. It is shown that colloidal CdSe nanocrystals attain a magic closed-shell structure at a radius of 1.8 nm, the growth rate at that nano-size deviate from the classical growth theory. Using thermodynamic and kinetic approach, we have explored methods for making truly single or multiple monosized nano-crystals of CdSe from colloidal systems [7-9].

Niodimium hafnate Nd2Hf2O7 with the pyrochlore structure is the promising component of high temperature ceramics that may be used for the modern thermobarier coatings owing to the high melting temperature and the phase stability in the wide temperature range. In the present study the superfine Nd2Hf2O7 with the pyrochlore structure was prepared by the self-propagating high temperature synthesis. The composition and purity of the sample obtained was confirmed by laser mass spectrometric method with the identification of the phase composition. Microstructure of the superfine Nd2Hf2O7 was studied by scanning and transmission microscopy. The specific surface values of the sample were found using the BET method. The thermal stability of material was studied by TGA/DSC/DTA methods up to the temperature 1473 K. The kinetics of the sintering process of the Nd2Hf2O7 sample prepared was investigated at the various temperatures. The Knudsen effusion mass spectrometric method was used to study of the vaporization processes and thermodynamic properties of Nd2Hf2O7 in the temperature range 2400-2600 K. Vaporization of Nd2Hf2O7 was done from the tungsten effusion cells using mass-spectrometer MS 1301 developed for the high temperature thermodynamic studies of the low volatile inorganic substances. The NdO, Nd and oxygen vapour species were identified over sample studied in the temperature range indicated. The partial pressures of these vapour species were obtained using the ion current comparison method. The vaporization dynamics of the NdO, Nd and oxygen vapour species over Nd2Hf2O7 as the functions of time and temperature was illustrated. The Nd2O3 activities in the Nd2Hf2O7 compound were found by the comparison method using vaporization from the double effusion cell: One cell was for the investigation of the compound under consideration and second was for the corresponding individual oxide. The enthalpies of sublimation of the main vapour species over Nd2Hf2O7 were obtained as well as the equations of the temperatures dependencies of the partial pressures of these species were presented. The question on the deviations from the ideality of Nd2O in the Nd2Hf2O7 compound at high temperatures was discussed.

Neodymium hafnate Nd2Hf2O7 with the pyrochlore structure is the promising component of high temperature ceramics that may be used for the modern thermobarier coatings owing to the high melting temperature and the phase stability in the wide temperature range. In the present study the superfine Nd2Hf2O7 with the pyrochlore structure was prepared by the self-propagating high temperature synthesis. The composition and purity of the sample obtained was confirmed by laser mass spectrometric method with the identification of the phase composition. Microstructure of the superfine Nd2Hf2O7 was studied by scanning and transmission microscopy. The specific surface values of the sample were found using the BET method. The thermal stability of material was studied by TGA/DSC/DTA methods up to the temperature 1473 K. The kinetics of the sintering process of the Nd2Hf2O7 sample prepared was investigated at the various temperatures. The Knudsen effusion mass spectrometric method was used to study of the vaporization processes and thermodynamic properties of Nd2Hf2O7 in the temperature range 2400-2600 K. Vaporization of Nd2Hf2O7 was done from the tungsten effusion cells using mass-spectrometer MS 1301 developed for the high temperature thermodynamic studies of the low volatile inorganic substances. The NdO, Nd and oxygen vapour species were identified over sample studied in the temperature range indicated. The partial pressures of these vapour species were obtained using the ion current comparison method. The vaporization dynamics of the NdO, Nd and oxygen vapour species over Nd2Hf2O7 as the functions of time and temperature was illustrated. The Nd2O3 activities in the Nd2Hf2O7 compound were found by the comparison method using vaporization from the double effusion cell: One cell was for the investigation of the compound under consideration and second was for the corresponding individual oxide. The enthalpies of sublimation of the main vapour species over Nd2Hf2O7 were obtained as well as the equations of the temperatures dependencies of the partial pressures of these species were presented. The question on the deviations from the ideality of Nd2O in the Nd2Hf2O7 compound at high temperatures was discussed.

Ti3SiC2 and Ti3AlC2 ceramics in the form of polycrystalline bulks or powders were synthesized by pressureless reactive sintering. The synthesis of Ti3XC2 (X = Si or Al) was carried out in argon by the sintering of well mixed powder blends of 2TiC/1.2X/Ti at 1200-1450 °C for Ti3SiC2 or 1310-1370 °C for Ti3AlC2 over various reaction times. Combined characterization techniques including XRD, SEM-EDS, and EPMA were applied to study reaction kinetics and formation mechanisms of Ti3XC2. This study revealed that the sintering temperature had a more profound effect on the reaction kinetics than the time. The mechanisms of formation of Ti3XC2 are proposed. Moreover, Ti3SixAl(1-x)C2 solid solutions (0 < x < 1) were also synthesized at 1370 °C from 3TiC/xSi/(1-x)Al/Ti powder blends directly and the prepared Ti3SiC2 and Ti3AlC2 powders. The lattice parameters of a unit cell of the synthesized Ti3SixAl(1-x)C2 solid solutions were measured and compared with available reported data.

Ti3SiC2 and Ti3AlC2 ceramics in the form of polycrystalline bulks or powders were synthesized by pressureless reactive sintering. The synthesis of Ti3XC2 (X = Si or Al) was carried out in argon by the sintering of well mixed powder blends of 2TiC/1.2X/Ti at 1200-1450 °C for Ti3SiC2 or 1310-1370 °C for Ti3AlC2 over various reaction times. Combined characterization techniques including XRD, SEM-EDS, and EPMA were applied to study reaction kinetics and formation mechanisms of Ti3XC2. This study revealed that the sintering temperature had a more profound effect on the reaction kinetics than the time. The mechanisms of formation of Ti3XC2 are proposed. Moreover, Ti3SixAl(1-x)C2 solid solutions (0 < x < 1) were also synthesized at 1370 °C from 3TiC/xSi/(1-x)Al/Ti powder blends directly and the prepared Ti3SiC2 and Ti3AlC2 powders. The lattice parameters of a unit cell of the synthesized Ti3SixAl(1-x)C2 solid solutions were measured and compared with available reported data.

Ceramic thermal barrier coatings (TBC) is a widely accepted technical solution for protection at heat shock and temperature of so-called "hot parts" utilized in aerospace, energy, metallurgy industries, etc. This is because their main quality of being able to operate at high temperatures, based on small differences in coefficients of expansion obtained between the metal support and ceramic layer.

Ceramic thermal barrier coatings (TBC) is a widely accepted technical solution for protection at heat shock and temperature of so-called "hot parts" utilized in aerospace, energy, metallurgy industries, etc. This is because their main quality of being able to operate at high temperatures, based on small differences in coefficients of expansion obtained between the metal support and ceramic layer. To achieve TBC structures were utilized ZrO2Y2O3 type powders with micron-and nanoscale structures, which were obtained by Air Plasma Spray techniques (APS) and High Velocity Oxygen Fuel (HVOF). The dinamics cycles of surfaces deterioration, the structural changes induced by heat shock initiated at heating-cooling rates up to 100°C / s as well as the comparative study of bonding layers made with nanoscale or micron particles, but also and the study the layers sustainability, were made as a result of tests performed on a facility's own design, versatile, equipped with single azis robots for handling samples and monitoring systems, data acquisition and processing program with multiple interface types Virtual Instrumentation Engineering Workbench Laboratory (Lab). The study of such intermediate structures thermal growth oxide (TGO) type at the interface support-bonding layer - TBC ceramic layer is important for revealing the mechanism of delamination of these types of materials. The study highlights the positive effect of utilising nanometric powders in comparison with micrometer with reference to layer ceramic / metalic support adherence, ceramic layer porosity, the formation of micron vertical cracks relaxing extreme thermal stresses. The study includes evaluation by the tribology light of wear factors associated to the turbo engines of cogeneration systems and tries to highlight the disruptive effect of rapid heating-cooling rates, respectively of thermal shock in relation with corrosive or erosive –adhesive wear utilising scanning electron microscopy by association ( SEM), combined with X-ray diffraction (XRD), transmission electron microscopy (TEM) phase analysis after the furnace cyclic oxidation.

Dual-phase ferrite/martensite steels with different volume fraction of ferrite were produced by heating a 4340 steel bar for 1h at 900°C and intercritical annealing at 738°C for different durations and a final oil quenching. Samples were then 3% pre-strained at temperature range of 150-450°C. Room temperature tensile test was performed on strained and unstrained samples. It was found that both yield stress and ultimate tensile strength have a maximum value at temperature range of 250-300°C. This anomalous behavior was attributed to dynamic strain aging effects. Data obtained from tensile tests were analyzed in terms of Hollomon equation and it was seen that work hardening of this steel can be described in two separate stages. Peaks observed in diagrams of Hollomon equation parameters at intermediate values of pre-strain temperature have been found as a mark of occurrence of dynamic strain aging as well as ones observed for YS and UTS at that temperature regime.

The control of grain structure is an important task in the manufacture of gas turbines blades. This research focuses on the effects of inoculant on the grain structure, microporosity and secondary denderite arm spacing (SDAS) in these blades. Sample blades were prepared by vacuum investment casting of superalloy IN738LC, which is used in the first and second stage of most gas turbines. Inoculation was achieved by applying 0-10% wt cobalt aluminate particles onto the mould as a coating. Using inoculant up to 6% resulted a significant reduction in grain size and increasing the amount of that seems to have no considerable effect on the structure.

The MAX phases – layered ternary carbides and nitrides with the general formula Mn+1AXn (MAX), where n=1, 2, or 3, M is an early transition metal, A is an A-group element (mostly IIIA and IVA), and X is either C or N – represent a new class of solids that posses an unusual, and sometimes unique, combination of properties that makes them good candidate materials for high temperature applications. Like ceramics, they are elastically stiff, have relatively low thermal expansion coefficients, good thermal and electrical conductivities, and are resistant to chemical attack. However, mechanically they cannot be more different: They are relatively soft (Vickers hardness 2–8 GPa) and most readily machinable, thermal shock resistant, and damage tolerant. Moreover, some are fatigue and creep, and oxidation resistant. This talk summarizes over 14 years of research and our current understanding of the mechanical properties of the MAX phases in general, and Ti3SiC2 and Ti2AlC in particular as two of the most studied MAX phases. At higher temperatures, they go through a brittle-to-plastic transition. At room temperature, they can be compressed to stresses as high as 1 GPa and fully recover upon removal of the load, while dissipating 25% of the mechanical energy. Special emphasis will be given to their non-linear kinking behavior and underling incipient kink band (IKB) mechanism. Since the MAX phases are potentially good candidate materials for high temperature structural applications, their elastic, stress-strain and creep behavior at elevated temperatures (up to 1400 oC) will also be reviewed.

It is a general perception that cement-based materials as concrete and reinforced concrete are relatively simple and as such are considered "low-tech" materials, or at least are ranked as far less complex if compared to bio-engineered materials or fuel cells for example. However, concrete has never been a "simple" material. The development of the required mechanical properties and further the necessary engineering performance starts on the nano/micro level of a hydrating cement matrix. Concrete is the material with highest level of consumption (second after water) and is essential in each aspect of our life. Concrete is a durable material, however, it surely has weaknesses and a more or less determined service life, since environmental factors affect to a large extent the life cycle of our structures. Further, when it comes to reinforced concrete, both materials, i. E. Steel and concrete, have to be considered and their material performance taken into account within service life. To this end, corrosion of steel in reinforced concrete is a major concern, since it affects the global performance of a structure and can have detrimental influence in short terms. In order to control (minimize or stop) the corrosion related issues, various methods, techniques and applications are well known and available. Novel solutions and smart materials are, however, currently demanded by the engineering practice. Damage initiation (e. G. Due to corrosion) or the development of the cement-based matrix, start on nano/micro level. Therefore, the purpose of our study is to influence the material properties (both steel and concrete) on the nano/micro level and thus to control eventual deterioration mechanisms (as corrosion) or achieve superior properties of the cement-based matrix (e. G. Uniform distribution of hydration products, reduced permeability etc.). Nano-aggregates (PEO-b-PS micelles) and/or hybrid composite aggregates (CaO particles, covered with a multi-layer of poly-electrolytes PDADMAC/PAA) were admixed in mortar and reinforced mortar in very low concentrations (0.006 wt. % per mortar weight). Some of the main results refer to achieved superior properties of the bulk matrix: Significantly reduced porosity (at least 2 times) and water permeability (3 orders of magnitude) in the presence of micelles. Further, the presence of hybrid aggregates increases the corrosion resistance of steel, compared to the control, micelles and hybrid aggregates-free mixtures. The paper will further discuss the mechanisms, related to the influence of these "complex" formations on cement hydration mechanisms and the phenomena within their performance at the steel/cement paste interface, resulting in increased corrosion resistance of modified reinforced mortar.

Interfacial reactions between liquid metals and ceramics are of technological importance in many fields of materials engineering such as joining of ceramics by brazing alloys, manufacturing of metal/ceramic composites, casting of metals, etc. In non-reactive metal-ceramic systems non-wetting is usually observed. In these systems, wetting can be significantly improved by certain alloying elements which form continuous layers of compounds at the interface, by reaction with the ceramic substrate. Such reactions are used in practice to promote wetting, especially for joining of ceramics by brazing alloys. As this reactivity can affect the physical properties of the interface and especially the mechanical behaviour of the system, it is important to control the nature, morphology and microstructure of the reaction product. The purpose of this presentation is to focus on the fundamental issues of metal/ceramic interfacial reactions and to analyse the main thermodynamic and kinetic factors governing these reactions. In particular, some physicochemical aspects which can affect, or even control, the morphological evolution of the interfacial region will be discussed by using and analysing different examples of interactions between oxide or non-oxide ceramics and reactive liquid alloys.

Na(Co1-xCux)2O4 (0≦x≦0.2) nano-sized powders were synthesized by solution combustion process. The process was highly effective in synthesizing high-quality Na(Co1-xCux)2O4 nanopowders. The effect of thermoelectric properties for the Na(Co1-xCux)2O4 was studied, considering the Cu content. The density and grain size were increased by adding Cu for Co in NaCo2O4. The electrical conductivity (σ) of the Na(Co1-xCux)2O4 decreased with temperature, indicating a metallic behavior. The Seebeck coefficient (α) slowly increased with temperature and its sign was positive, i. E., p-type conduction. The power factor gradually increased up to 800 ℃. The partial substitution of Cu for Co in NaCo2O4 led to a significant increase in the power factor (σα2). We believe that the partial substitution of Cu is considered to be favorable for improving the thermoelectric properties of NaCo2O4.

Prof. Dr. Kamarudin HussinMohd Mustafa Al Bakri AbdullahChe Mohd Ruzaidi GhazaliCheng YongLiew Yun MingCentre of Excellence Geopolymer System Research, School of Material EngineeringUniversiti Malaysia Perlis (UniMAP), 01000, P.O Box 77, D/A Pejabat Pos Besar, Kangar, Perlis, Malaysia E-mail: kamarudin@unimap.edu.myMalaysian government has committed the nation to a voluntary 40% carbon intensity reduction by the year 2020. Undoubtedly the ambitious target is still a realistic goal, should the widespread adoption of green technology be realized in the country. Green technology is the development and application of products that are infused with innovation and sustainable solutions, which minimizes the negative impact of human activities. Geopolymer system significantly reduced greenhouse emissions with added advantages in wide range of applications. The Centre of Excellence Geopolymer System Research is hence established to steer and enhance geopolymer research in the country.From building and construction, automobile engineering, sport and leisure goods to packaging industry, the trend is moving towards the use of high performance light weight materials. All of these can be achieved by utilizing lightweight geopolymer materials. For example, cities heated by sunlight retain their high temperature up to midnight, as the ground surface is covered by artificial pavement materials and many large buildings. Hence, porous geopolymer materials can be used as water retention parking lots, sidewalk, and roof top to serve as a cooling system which reduces the temperature efficiently. Porous geopolymers can also be utilized as adhesive refractory materials. Moreover, unless something drastic and different is done, the world’s atmosphere will continue to be damaged by the production of Portland cement. In this case, geopolymers can suppress greenhouse gas up to 80-90% during its manufacturing process while providing comparable performance. Geopolymer cement concretes are also studied to serve as anti-corrosion field in order to solve the corrosion problem in seaside construction. In addition, nanoclay geopolymers can be investigated to enhance fire, mechanical and barrier properties.In conclusion, geopolymer is a diverse field of study. Currently, studies are conducted in major research clusters to cater to the current needs in the country via green technologies which at the same time aiming eco-efficiency while minimizing adverse environmental impacts.

Nanocrystalline Ca2Gd8Si6O26 (CGS): Sm3+ and CGS: Tb3+/Sm3+ phosphors were prepared by solvothermal reaction method for light emitting diode (LED) and field emission display (FED) applications. The XRD patterns of these phosphors confirmed their oxyapatite structure in the hexagonal lattice. The visible luminescence properties of these phosphors were investigated by exciting with ultraviolet (UV) or near-UV light and low voltage electron beam. The photoluminescence (PL) properties of Ca2Gd8Si6O26 (CGS): Sm3+ and CGS: Tb3+/Sm3+ phosphors were investigated as a function of Sm3+ concentration. Cathodoluminescence (CL) properties had also been examined by changing the acceleration voltage. The CGS: Sm3+ showed the dominant orange emission due to the 4G5/2→6H7/2 transition. The CGS: Tb3+/Sm3+ phosphor showed the green, orange and white emissions when excited with 275, 378, and 405 nm wavelengths, respectively. The chromaticity coordinates of these phosphors were comparable to or better than those of standard phosphors for LED or FED devices.

The hybrid system chemical vapor deposition (HYSYCVD) process is used in this work in order to synthesize zirconium nitride species (ZrNx) by means of the thermal decomposition of a solid precursor (potassium hexafluorozirconate, K2ZrF6) in a nitrogen N2 atmosphere. The synthesis of the zirconium nitrides is carried out in a deposition reactor designed and built at the University of Colima, Mexico. These nitrides ZrNx are deposited at the surface of low-carbon steels with the purpose to increase their surface mechanical properties. The zirconium nitrides are also microstructurally characterized by scanning electron microscopy, atomic force microscopy and by X ray diffraction, while the hardness is determined by Vickers microindentation test. The HYSYCVD process is an alternative process to common CVD processes due to the fact that it is possible to synthesize different transition metal nitrides utilizing solid-gas precursors at the same time.

« Back To Technical Program