Papers by Keyword: Thermal Expansion

Abstract: This study was designed to evaluate mechanical properties and the marginal fitness of glass infiltrated alumina core fabricated from aqueous alumina tape. Utilizing the automatic Dr. Blade model (DP-150 of Japan JinChungjungGi manufacturer) fabricated the slurry into 0.5 ㎜ thickness aqueous-based alumina tape. The coefficient of thermal expansion and biaxial flexural strength of alumina composite produced from alumina tape were investigated. Three upper central resin incisors were prepared with 90o, 110o, 135o shoulder margin for all-ceramic crown. Individual tooth model’s impressions were taken 15times each to make epoxy resin die. Cores were made of alumina tape to each and every dies. Crown setting was done on the epoxy resin dies. The specimens were evaluated for measuring for marginal gaps of glass infiltrated alumina core fabricated from aqueous alumina tapes under 180 magnifications with Kan Scope(Sometech Vision, Korea) was done. The retained measurements were analyzed with Turkey’s Studentized Range Test for marginal fitness of each specimen. Coefficient of thermal expansion of alumina tape was 7.5x10-6/°C, and biaxial flexural strength was observed to be 498±32MPa. The marginal fits of alumina cores made of alumina tapes showed the least marginal gap of 41.5 ㎛ in the 110o shoulder margin, and increasingly with 135o, 90o shoulder margin. Marginal fitness should be better in angles larger than 90o.

Abstract: The iron and zinc calcium oxysulfides Ca3Fe4S3O6, CaFeSO and CaZnSO are synthesized by reacting mixtures of CaO and FeS or of CaO and ZnS in an inert atmosphere. Their elemental compositions and lattice parameters are determined by X-ray microanalysis and X-ray diffraction. From the temperature-dependent lattice parameters of oxysulfides (measured up to 1170K) their thermal expansion coefficients are evaluated. Oxidation Ca3Fe4S3O6 and CaZnSO are studied by thermogravimetric analysis when air heated. Oxidation speed temperature coefficients showing that process limiting stage is diffusion are determined.

Abstract: Tensile residual stress happen by difference of coefficients of thermal expansion between fiber and matrix is one of the serious problems in metal matrix composite (MMC). TiNi alloy fiber was used to solve the problem of the tensile residual stress as the reinforced material. TiNi alloy fiber improves the tensile strength of composite by occurring compressive residual stress using shape memory effect in the matrix. A hot press method was used to create the optimal condition for the fabrication of shape memory alloy (SMA) composite. The bonding effect between the matrix and the reinforcement within the SMA composite was strengthened by the cold rolling. The fabricated composite by these processes can be applied as a part of the aircraft, and this part is operated under severe flying condition such as low temperature and high pressure. In this study, an acoustic emission technique was used to quantify the microscopic damage behavior of cold rolled TiNi/Al6061 SMA composite at low temperature condition. The results showed that the tensile strength of the TiNi/Al6061 SMA composite increased with the TiNi reinforcement at low temperature condition, but the strength for the specimen subjected to the cold rolling decreased. AE parameters of AE counts, amplitude and energy were useful to evaluate the microscopic damage behavior of the composite.

Abstract: Burning or transmutation of minor actinides (MA: Np, Am, Cm) as well as plutonium is an option for the future nuclear fuel cycle. For the transmutation of MA, research and development of MA-bearing fuels that are quite different from the current UO2 and (U,Pu)O2 fuels have to be made. Among various fuel types, nitride is one of the attractive fuels to the MA-bearing fuel. The thermochemical and thermophysical properties of nitride fuels available in literature, such as the thermal expansion, specific heat capacity, thermal conductivity, thermal creep, vaporization behavior, etc., are briefly reviewed and the new data obtained on actinide nitrides are presented. The thermal expansion was measured by high-temperature X-ray diffraction, the thermal diffusivity by laser-flash method, the thermal creep by compression method, Young’s modulus by pulse echo method, and the hardness by indentation method.

Abstract: Multicomponent Al-Si based casting alloys are used for a variety of engineering applications. The presence of additional elements in the Al-Si alloy system allows many complex intermetallic phases to form, which make characterisation non-trivial due to the fact that some of the phases have either similar crystal structures or only subtle changes in their chemistries. A combination of electron backscatter diffraction (EBSD) and energy dispersive X-ray analysis (EDX) have therefore been used for discrimination between the various phases. It is shown that this is a powerful technique for microstructure characterisation and provides detailed information which can be related to microstructure evolution during initial casting and subsequent heat treatment. The mechanical properties of different intermetallic phases have been investigated as a function of temperature using the nanoindentation technique. In particular, the hardness and modulus of a number of phases have been established for a range of alloy compositions. Physical properties of some of the intermetallic phases are also discussed. Phase identity, composition, physical and mechanical properties are set in context to inform alloy design strategies.

Abstract: In the article a continuous method for measurement of wear under conditions of technically dry friction of tribological kinematic pairs of the type pin–on–disk of T–11 tester, as an example is presented. Also taken up was a test of an evolved simple method for evaluation of correction on the participation of thermal expansion in size change of a frictional kinematic pair. The analysis of obtained results showed the existence of correlation between total experimental wear and analytical value of total wear (decrease of linear dimension of pin).

Abstract: The effects of interfacial thickness and temperature on thermal conductivity and CTEs of Al/SiC packaging materials were investigated. The interfacial thermal conductivity and thickness have significant influence on the thermal conductivity of the Al/SiC packaging materials, while the SiC size has slight influence on that of the Al/SiC packaging materials. The experiment results of thermal conductivity are similar to Hassleman model and simulation results. Schapery model can be used to calculate the CTEs of composites when temperatures are lower(50~100°C) and Kerner model can be used when temperatures are higher(300~450°C). The CTEs of composites will increase more quickly than that by three models when temperatures are between 100°C and 300°C.

Abstract: In this paper, we describe our recent work on metal matrix composites (MMCs) with submicron-size TiB2 and Al2O3 particulates that are synthesized in situ from Al-rich Al-Ti-B and Al-TiO2- B powder reactants by reactive sintering. Reaction sequences examined in the two different reactant systems are summarized, and some experimental results on elevated-temperature properties, i.e. thermal expansion, temperature dependence of dynamic tensile modulus and creep behavior, are shown and discussed from micromechanics-based viewpoints.

Abstract: Single crystals of (Mo0.8Nb0.2)5Si3, (Mo0.85W0.15)5Si3 and Mo5Si3 were grown and their thermal expansion along the a- and c-axes and single crystalline elastic property were investigated. An anisotropy ratio of coefficient of thermal expansion (ac/aa) is lower for (Mo0.8Nb0.2)5Si3, and higher for (Mo0.85W0.15)5Si3 at RT than that for Mo5Si3. However, the ac/aa for (Mo0.8Nb0.2)5Si3 increases with increasing temperature and the ac/aa of the three compounds is similar at 800°C. The values of isotropic average Young’s (E), bulk (K) and shear (G) moduli for (Mo0.8Nb0.2)5Si3 is the lowest and those for (Mo0.85W0.15)5Si3 is the highest in the three compounds. On the other hand, the difference of E between [100] and [001] increases when partial substitution of Mo by Nb occurs and it decreases when partial substitution of Mo by W occurs. Simply compared with the results of thermal expansion anisotropy, the result shows opposite tendency.