Advanced Materials Research Vols. 631-632

Abstract: Based on the experimental data of entropy change varying with temperature, the regenerative Brayton refrigeration cycle using Gd_0.94Er_0.06 as the working substance is set up for magnetic field changes with 0-1T and 0-2T. By using thermodynamic analysis method, some parameters such as the non-perfect regeneration, net cooling quantity, coefficient of performance (COP), and so on, are analyzed and calculated. The effects of temperature of the heat reservoir, regeneration and external magnetic field are also discussed. The results obtained in the present paper show that the refrigeration cycle operating in T_C=T₀, T_H= T₀+7_K and 0-2T magnetic field change has not only maximum cooling quantity but also maximum COP in all the established magnetic refrigeration cycles, and can provide some new guide for the optimal design of real room-temperature magnetic refrigerators.

Abstract: Based on the experimental characteristics of iso-field entropy varying with temperature for the room-temperature magnetic refrigeration material La(Fe_0.88Si_0.12)₁₃H₁ or Gd, the regenerative Ericsson refrigeration cycle using La(Fe_0.88Si_0.12)₁₃H₁ or Gd as the working substance is established and their thermodynamic performances are evaluated and analyzed. By means of numerical calculation, the influence of non-perfect regeneration on the main thermodynamic performances of the cycle is revealed and discussed. Furthermore, the coefficient of performance (COP), non-perfect regenerative heat quantity, and net cooling quantity of the Ericsson refrigeration cycle using La(Fe_0.88Si_0.12)₁₃H₁ or Gd as the working substance are compared. The results obtained show that it is beneficial to the cooling quantity of the cycles using La(Fe_0.88Si_0.12)₁₃H₁ or Gd as the working substance to operate in the region of T_cold >T₀ and, at the condition of a same temperature span, the cooling quantity for La(Fe_0.88Si_0.12)₁₃H₁ is larger than that for Gd.

Abstract: Comparing with Ti₅₀Ni₄₇Fe₃ alloys, the influences of Cr on the mechanical and shape memory properties of Ti₅₀Ni₄₇Fe₃ alloys are investigated by study on phase transformation and microstructure analysis. The results show that Ti₅₀Ni₄₇Fe₃ and Ti₅₀Ni_46.75Fe₃Cr_0.25 shape memory alloys exhibit two-stage martensitic transformation. The transformation temperatures decrease with the addition of Cr. The microstructure of the Ti₅₀Ni₄₇Fe₃ and Ti₅₀Ni_46.75Fe₃Cr_0.25 alloys consists of TiNi matrix, Ti2Ni phase. Fe element prefers to substitute for Ni in the matrix than black particles. Cr all substitute for Ni in the matrix and not be analyzed in the Ti₂Ni phase. The mechanical property of Ti₅₀Ni_46.75Fe₃Cr_0.25 alloy is better than Ti₅₀Ni₄₇Fe₃ alloy.

Abstract: GATo propellant with different storage life was obtained by aging test. The stabilizers content and methyl violet test burst time of the samples were measured by GC and methyl violet test instrument. The relationships of t_b vs. t_a, t_b vs. R and R vs. t_a were determined. The results show that the variation regularities of t_b with t_a and Res content with t_a are very similar, and the variation regularity of t_b with Res content is linear relationship. In addition, the Scattering field of methyl violet test burst times is very small. So, it is feasible that the stability evaluation of GATo propellant with methyl-violet burst time.

Abstract: In this paper, based on the parameters of cumulative residual strain(CRS), the effects of different contents of Mg and Si elements in Al matrix on the dimensional stability of SiCp/Al composites was investigated and analyzed in the temperature interval of 25～400°C. Results show that，with the increasing of Si content in Al matrix, the CRS fluctuates only in a small range of strain, adding Si in Al matrix is beneficial to the dimensional stability of the composites, which can be improved through pre-thermal cycling; with the increasing of Mg content in Al matrix, the absolute value of negative CRS of the composites becomes smaller at the beginning and then turns positive, adding Mg in Al matrix causes the composites expand after several thermal cycling, it is not good to the dimensional stability of the composites and is quite impossible to be improved by pre-thermal cycling. Besides, the CRS in thermal cycling is mainly caused by the plastic relaxation, which results in the irreversible dimensional variation of about 10^-5~10^-4.

Abstract: The two flux approximation model is usually used to calculate the heat transfer of radiation for porous materials. In this paper, the parameters identification method of the extinction coefficient and the albedo of scattering in the two flux model is set up by using the identification theory according to the data of the back temperature. The simulated process shows that the convergence rate is fast and the results by the parameters identification are very close to the origin values.

Abstract: With graphite, 45 steel and copper as substrates respectively, Ti(C,N)-TiB₂ composite ceramic preforms with micro/nanometric grains were prepared by self-reactive sprayed forming technology. The cooling rate of spray particles deposited on different substrates was calculated by finite element method. The influence of cooling rate on morphology of micro/nanometric grains of Ti(C,N)-TiB₂ composite ceramic preforms was studied by means of SEM, XRD and EDS. The results showed that the average cooling rates of particles deposited on the three kinds of substrates were 7.0×10⁷°C/s, 8.1×10⁷°C/s and 10.7×107°C/s respectively. The extremely quick cooling rate was the essential reason why the spray formed preforms were composed of micro/nanometric grains. The TiC_0.3N_0.7 grains in preforms deposited on three kinds of substrates all took on anomalous equiaxed grains. Quicker the cooling rates of the deposited particles were, smaller the grains were. The grain size of them was all less than 3μm. Whereas the influence of cooling rate on the morphology of the TiB₂ grains was great. When with graphite as substrate, TiB₂ took on rod-like grains with big length to diameter ratio. When with 45 steel as substrate, it took on near equiaxed grains. And when with copper as substrate, it took on lamina grains with thickness of about 100nm due to the extremely quick cooling rate and the extremely large degree of supercooling. That’s because with the change of the cooling rates, the remaining time of the liquid phases is different, so as to the growing time of the grains along the habit plane is also very different.

Abstract: It was compared AH32 opened plate using new techology in the mechanical properties. Results showed: the mechanical properties of AH32 opened plate are the same at the classification plate. The transverse tensile stength and yield strength of AH32 opened plate have an advantage over it’s longitudinal. The transverse elongation of AH32 opened plate is below the longitudinal. It is different the mechanical properties that is made of the deformation variance of AH32 opened plate in the transverse and the longitudinal.

Abstract: Polymethyl methacrylate (PMMA) has shown some excellent performances. However the humidity environment affects mechanical properties of PMMA seriously. In this work, the digital phase-shifting photoelasticity is used to test the humidity stress of the boundary according to which we concluded that the boundary stress decreases gradually from the boundary to the inner. The mathematical model of the boundary stress distribution is established based on the distribution law of the boundary stress. This mathematical model can be used to predict the effect of the humidity environment to the boundary stress, and guide PMMA to use safely.

Abstract: Using calcium alginate medical film to explore the preventive measures of bone cement leakage in PVP.60 fresh vertebral bones were dissected from pigs(10 months old with average weight 152.5±7.5kg), and randomly divided into the blank group, the control group and the experimental group, 20 vertebral bones for a group. Eliminated the extra muscles and ligaments and the upper and lower endplates were completely retained. The models of vertebral compression fractures with fissures in front of vertebra were prepared by drilling two holes with a 3.2mm electric drill from lateral of the junction of the halfway point of parapophysis and the vertical of superior articular process to anterior vertebra along the direction of pedicles of vertebral archs by angle 10 and 15 degree and downward sloping 5 degree with the sagittal planes. Only bone cement was injected to the blank group, while the control group were injected with bone cement after injected medical fibrin glue. And the experimental group were injected with bone cement after injected sodium alginate glue and solidified by saturated calcium chloride. The injection dose of bone cement was recorded when bone cement leaked. The injection dose of bone cement in experimental group was significantly higher than the blank group and the control group when bone cement leaked (P<0.01).Calcium alginate medical film can effectively prevent the leakage of bone cement in PVP.