Applied Mechanics and Materials Vol. 577

Abstract: Vulcanization methods of conductive silicon rubber are described in this paper. Several common vulcanization agents are also be introduced. The conductivity and mechanical properties of the conductive silicon rubber composite materials are effected by vulcanization systems. The influence degree is introduced by respectively using different vulcanization method, vulcanizing time and vulcanizing temperature. The research progress of vulcanization system of conductive polymer composites is elaborated.

Abstract: Ground source heat pumps (GSHP) have been widely used in recent years. The heat transfer between borehole heat exchanger (BHE) and earth is the key factor impacting on the performance of GSHP. However, in order to setup BHE, a large amount of area of land is necessary, since the heat capacity of earth is limited. In this paper, phase change materials (PCMs) are used as grout instead of common materials. Thus, the heat capacity of soil has been improved, but the heat transfer characteristic of BHE has also changed. To prove its feasibility, the 3-dimensional numerical heat transfer simulation has been carried for three models which grout are respectively soil, PCMs, and PCMs with heat transfer enhancement measures. The characteristics of heat transfer and the land areas used of the three models are compared. The results show that the land area can be reduced effectively with PCMs as backfilling, while heat transfer enhancements must be adopted because the conductivity of PCM is small.

Abstract: As a specific morphology, the porous carbon fiber was prepared through carbonization of polyacrylonitrile/polymethyl methacrylate (PAN/PMMA) blend fiber with the PAN weight of 70%. The morphology and crystalline structure of the obtained porous carbon fibers were investigated by SEM, XRD, and Raman. The obtained porous carbon fiber produced at carbonization temperature of 1000-1400°C as well as the solid carbon fiber were cut into millimeter size and used as fillers to add to epoxy in order to make composite with the weight of 6%. The complex permittivity of these composites was measured using a network analyzer. The results reveal that the cross section of obtained carbon fiber from PAN/PMMA (70/30) is full of pores with size of 0.1-1um. The graphite crystalline degree becomes high with increasing the carbonization temperature. The composite filled by the porous carbon fiber shows better microwave absorption than that filled by the solid carbon fiber, the lowest reflection loss is-24.5dB and the band width with reflection loss below-10dB is 1.9GHz as the porous carbon fiber is the filler. Among three carbonization temperature: 1000°C, 1200°C, 1400°C, the porous carbon fiber prepared at 1200°C gives the best microwave absorbing performance.

Abstract: Sulfonated poly (arylene ether sulfone) s (SPAESs) exhibit good proton conductivity, thermal and mechanical properties, could act as candidates of proton exchange membranes for fuel cells. At the same time, the poor oxidative stability and excessive swelling ratio of SPAESs bring limitations for its further use. In this article, PAN was employed to mix with SPAES, and then SPAES/PAN blend membranes were prepared from the blend solution by casting. The water uptake, dimensional and oxidative stability, proton conductivity were measured with respect to the addition content of PAN, the phase morphology of the resultant SPAES/PAN were also observed by SEM. The results explained that the corporation of PAN into SPAES could reduce the water uptake and improve the oxidative stability of the obtained membranes compared with the pristine SPAES membrane. That the PAN phase distributed as separated domains in SPAES matrix was found, the interaction between SPAES and PAN may be present, which is responsible for the improvement of dimensional and oxidative stability. Although the proton conductivity of the blend membranes became reduced with increase of PAN content in the SPAES/PAN blend, the conductivity of 0.0265S/cm at 30°C could still be reached, satisfying the requirement for proton exchange membrane Fuel Cell

Abstract: Polybenzoxazole (PBO) fiber membranes with submicron-scale diameter were fabricated from the polyhydroxyamide (PHA) precursor by electrospinning and thermal cyclization processes. In order to improve the strength of the membrane MWCNTs was blended with PHA in the mixture solvent of dimethylacetamide (DMAc) and THF. The morphology, thermal stability, mechanical properties and dielectric constant of MWCNTs / PHA and MWCNTs / PBO membranes were characterized. For MWCNTs/PBO membranes, improved mechanical property and low dielectric constant could be achieved.

Abstract: The microstructure of rare earth NiCrMoY alloy manufactured by atomization and oxygen-acetylene flame spray and high frequency induction remelting technique is investigated by a combination of scanning electron microscopy (SEM), energy spectrum, X-ray diffraction meter (XRD). The results indicate that Microstructure of NiCrMoY alloy coatings are finer and bulk-and needle-like hard Metallograph are precipitated, a new phase MoB is produced.

Abstract: In order to effectively use Magnetically Controlled Shape Memory Alloy (MSMA) for vibration control in civil engineering structure, the deformation mechanism and dynamic characteristics of the MSMA were studied; research methods apply to the constitutive relation of vibration control in civil engineering structure is given. Based on the study about MSMA vibration controller and its application in structural vibration control in engineering, MSMA in structure vibration control application prospect and development direction are introduced. At the same time, for the difficulties existing in the application are discussed in this paper. The results prove that MSMA materials in structural vibration control are of important value.

Abstract: Co-gasification of biomass and coal is increasingly considered as a promising technology for sustainable utilization of coal and large-scale use of biomass. Co-gasification characteristic and kinetic analysis are the basic and essential information for the application of this technology. In this paper, co-gasification behavior of a typical bituminous coal from western China and spent mushroom compost (SMC) was investigated through thermogravimetric analyzer. The temperature interval was from ambient temperature to 1000 ○C with various heating rates (10, 20, 40 ○C•min^-1) under carbon dioxide atmosphere. Kinetic parameter was solved through Distribution Activation Energy Model (DAEM). The results indicated that he maximum decomposition rates of the mixture and SMC were higher than that of coal except 25% SMC. Slightly synergistic effect during the co-gasification was found. The average values of the activation energy were 25.07 kJ•mol^-1 for bituminous coal, 204.47 kJ•mol^-1 for 25% SMC, 123.14 kJ•mol^-1 for 50% SMC, 144.05 kJ•mol^-1 for 75% SMC and 227.50 kJ•mol^-1 for SMC, respectively.

Abstract: The effect of TMCP parameters on the microstructure and mechanical properties of cargo oil tanks (COT) steel is investigated. The microstructure characteristics are performed by optical microscope, and the mechanical properties are researched by tensile test at ambient temperature and impact test at different temperatures (-20°C, -40°C). The results show that the microstructures of COT steel are a mixed microstructure consisting of ferrite, granular bainite and pearlite, which are resulted from the special TMCP parameters. The COT steel has good comprehensive mechanical properties by analyzing the experimental data, satisfying the international standard. Furthermore, impact fracture surfaces appear small dimples and a few of large ones, most of the dimple with a certain direction, and the inclusion with the fracture is mainly composed of MnS, CaS and Al₂O₃ composite product.

Abstract: The effect of the different sizes and densities of He bubble on the mechanical properties of CLAM alloy was studied by milt-scale simulation method. It is found that with the increasing of helium bubble size and density, the yield strength and yield strain of CLAM alloys reduced, and the yield strength and yield elongation are predicted to be consistent with the experimental results.