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.