Advanced Materials Research Vols. 1120-1121

Abstract: TiNi/Al shape memory alloy (SMA) composite was fabricated by a vacuum hot-pressing method to investigate the phase , microstructure and mechanical properties. Phase analysis was conducted by XRD . Interface bonding between TiNi wire and Al matrix was observed by using SEM and EDS. Quasi-static and dynamic compressive mechanical properties of the composite were investigated by using electronic universal testing machine (INSTRON5985) and Split-Hopkinson Pressure Bar (SHPB),respectively. The experiment results show that new phases Ni₄Ti₃ and Ti₂Ni precipitined from TiNi wire. Interfacial reactions occurred at the bonding between matrix and TiNi wire, creating a diffusion layer about 2μm thick. Both quasi-static and dynamic compressive mechanical properties are anisotropic , and the degree of the anisotropy increased with the increase of TiNi volume fraction.

Abstract: The La_0.7Sr_xCa_0.3-xMnO₃ (x=0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3) were prepared by combining sol-gel method and high temperature sintering. The effects of Sr doping content on the structure and morphologies of the La_0.7Sr_xCa_0.3-xMnO₃ finally sintered at 1050°C/1250°C were investigated based on the analyses of X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). The results show that the La_0.7Sr_xCa_0.3-xMnO₃ exhibit single perovskite phase and the change of Sr doping content can result in phase structure transition. The La_0.7Sr_xCa_0.3-xMnO₃ samples are rhombohedra structure in the range of 0.15≤x≤0.3. When x is no more than 0.1, the La_0.7Sr_xCa_0.3-xMnO₃ samples sintered at 1050°C present distorted cubic structure. The microstructure of La_0.7Sr_xCa_0.3-xMnO₃ sintered at 1050°C for 5h becomes more and more looser and its grains tend to refinement with the increase of Sr doping content when x is no less than 0.05. Increasing the final sintering temperature can improve the density and promote the grain growth of La_0.7Sr_xCa_0.3-xMnO₃. In order to gain a dense microstructure, the final sintering temperature of La_0.7Sr_xCa_0.3-xMnO₃ should be higher than 1050°C and should be suitably increased with the increase of Sr doping content.

Abstract: In the present work, mechanical properties of prepreg carbon composites are studied. Five types of composite samples with different number of layers and prepreg material corresponding to material composition used for carbon rims are manufactured by compression molding. Prepared composites are tested and compared with respect to flexural strength and modulus. Furthermore, impact performance using Charpy impact test is also evaluated.

Abstract: Phenolic resin modified with methylvinylcyclosilazanes (MVSZ) were prepared and their flame-retardant properties were investigated, and results exhibited that the Limited Oxygen Index (LOI) values increased with the content increasing of MVSZ, and the LOI reach to 40.8, when the content of MVSZ was 26.0%. The flame-retardant and mechanical properties of polyester fabrics reinforced phenolic resin modified with silazanes (PFMS) composites were measured, the results indicated that the LOI and flexural strength were enhanced compared with those of phenolic resins composites.

Abstract: Thermal insulation materials are the most crucial composition in the external wall insulation technology. For the poor fireproofing of organic thermal insulation material, the inorganic/organic composite foamed thermal insulation material is prepared by optimizing inorganic foaming reaction. Inorganic polymer cross-linking system is used as the skeletal structure of foamed composite material and the modified urea-formaldehyde resin with excellent fire resistance is used as toughening material. The analysis results indicate that the composite structure with metal phosphate as skeleton and modified urea-formaldehyde resin as toughened-membrane is formed during the preparation process of the composite foamed material. The property test shows that the thermal conductivity is 0.0389W/m·K, the compressive strength is 180kPa, temperature rise in furnace is less than 20°C and the mass-loss rate is less than 50%. What is more there is no obvious flame appeared in the building materials incombustibility test. Therefore the composite foamed material can be judged to be A-grade incombustible thermal insulation material.

Abstract: In the present work, mechanical properties and bending stiffness of composite structures with ribs are studied. The aim of this work was making ribbed composite structures in one step, where the ribs are inserted between glass reinforcement of composite system. In practice, the ribs on the composite structure (final products) are glued, but where there is a lower strength (according to the type of surface, the surface treatment, suitable bonding technology, the type of glue) and the adhesives are relatively expensive. The production of samples was used technology of vacuum infusion under flexible foil.

Abstract: The fire retardancy of coextruded wood-plastic composites (WPCs) containing melamine, ammonium polyphosphate (APP), natural graphite, expandable graphite and carbon nanotubes (CNTs) in the shell layer was characterized with a cone calorimeter test. A coextruded composite manufactured without any fire retardant (FR) in the shell layer was used as a reference. The incorporation of different combinations of FRs in the shell layers of WPCs reduced the peak heat release rate by 3-43%, depending on the FR combination. Other studied parameters, such as ignition time, total heat release and mass loss rate were improved after FR systems loading. The best improvement of flammability characteristics was observed with melamine/natural graphite combinations, whereas the melamine/expandable graphite system resulted only in slight improvement of the studied parameters. However, it should be noted that the amount of expandable graphite loading was 2-4 times lower than the amount of natural graphite loadings. Incorporation of 2 wt.% CNTs in the shell layer did not show any significant improvement in the studied parameters. The total smoke release and carbon monoxide production were increased with melamine/APP loading in the shell layer.

Abstract: When offshore oil field has been completed and put into production, the new subsea pipelines and cable will need to be established. Cable protection pipe clamp is used to fix cable protection pipe on the jacket. In order to avoid the problem of traditional steel structure clamps which was difficult to joint, align and fasten when it installed cable protection pipe underwater, reduce the risk and workload underwater, This paper will study a new type of portable connecting riser clamp made of resin matrix composites which can solve the installation problem which is difficult to install cable protection pipes underwater. The main structure of pipe clamps made of resin matrix composites used three divided-plates type of structure. The load characteristic of clamps was determined by Morison equation which is a classical theory and clamps underwater mechanics analysis model was established. The results show that the strength of the base of clamps meet the requirements after strength analysis with finite element analysis method, stability and strength experiments, which means the clamps made of resin matrix composite is feasible.

Abstract: Borazine-silicon-containing arylacetylene (PBZSA) resin was a novel organic inorganic hybrid polymer and prepared through condensation reaction among B,B’,B’’-trichloroborazine, dichlorosilane and arylacetylene Grignard reagent. The chemical structure of PBZSA resin was characterized by FT-IR and ¹H NMR. The thermal stability and dielectric properties of cured PBZSA were investigated by TGA and broadband dielectric spectrometer. The results indicated that cured PBZSA showed high thermal stability with char yield up to 87.1% at 1000°C and at decompose temperature (T_d5) 580°C, and low dielectric constant (2.8-2.9) and dielectric loss (<0.005).

Abstract: In this work, spherical LiFePO₄/C composite had been synthesized by co-precipitation and spray drying method. The structure, morphology and electrochemical properties of the samples were characterized by X-ray diffraction (XRD), scanning electron micrograph (SEM), transmission electron microscope (TEM), constant current charge-discharge tests and electrochemical impedance spectroscopy (EIS) tests. The spherical LiFePO₄/C particles consisted of a number of smaller grains. The results showed that the morphology of LiFePO₄/C particles seriously affected the Li-ion diffusion coefficient and electrochemical properties of lithium ion batteries. Electrochemical tests revealed the spherical LiFePO₄/C composite had excellent Li-ion diffusion coefficient which was calculated to be 1.065×10^-11 cm²/s and discharge capacity of 149 (0.1 C), 139 (0.2 C), 133 (0.5 C), 129 (1 C) and 124 mAhg^-1(2 C). After 50 cycles, the capacity retention rate was still 93.5%.