The morphology, mechanical properties of unsaturated polyester（UP） resin modified with TDI were studied via dynamic FT-1R spectra, SEM, DMA and mechanical property testing. Results show that companying with the cure...
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The morphology, mechanical properties of unsaturated polyester（UP） resin modified with TDI were studied via dynamic FT-1R spectra, SEM, DMA and mechanical property testing. Results show that companying with the cured cross-linking reaction of UP resin, TDI can firstly react with UP and produce polyurethane（PU）, and then UP and PU form the cross-linking nets together. The impact fracture section morphology of modified UP resin manifested the typical sea- islands structure. Testing of mechanical properties showes that for introducing of PU, the TDI has an obvious effect on the toughness and strength of UP resin. When the ratio of TDI/UP （w/w） was 7.5%, the modified UP resin exhibited the best mechanical properties with flexural strength of 125 MPa, impact strength of 18 kJ·m^-2 and tensile strength of 72 MPa.
Mg2Si is a kind of narrow-band-gap n-type semiconductor, which is a promising environmental friendly thermoelectric material for its high electrical conductivity, low thermal conductivity, as well as non-toxicity and ...
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ISBN:
(纸本)9788880800842
Mg2Si is a kind of narrow-band-gap n-type semiconductor, which is a promising environmental friendly thermoelectric material for its high electrical conductivity, low thermal conductivity, as well as non-toxicity and non-pollution. In the present study, the fabrication process of Mg2Si thermoelectric material is systematically explored by spark plasma sintering technique (SPS) from Mg and Si raw powders. The density, phase and microstructure of the specimen are analyzed by XRD and FE-SEM. The results suggest that the complete reaction temperature for Mg and Si is 550°C, and the excessive content of Mg is helpful for obtaining the high purity Mg2Si. The relative density can reach 97% when the sample is prepared under the condition of 550°C-250MPa-10min, but crack is observed on the sample surface. Therefore, Mg and Si powder firstly react at 550°C-20MPa-30min, followed by sintering at 750°C-20MPa-5min. The sintered sample contains only Mg2Si phase with a high relative density near 100% and Mg2Si grains are fine and homogeneous.
The dynamic compressive behavior of Al2O3 (10% vol.) / TiB2 ceramic composite had been tested by using a split Hopkinson pressure bar in this paper. The results show that the main failure modes of the ceramic composit...
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The dynamic compressive behavior of Al2O3 (10% vol.) / TiB2 ceramic composite had been tested by using a split Hopkinson pressure bar in this paper. The results show that the main failure modes of the ceramic composite include crushed failure and split fracture along the loading direction. The former is the typical compressive failure of brittle materials. The later is tensile failure along the flaws produced during the composite manufacturing. The numerical simulation was also used to study the effect of the diameter/length ratio of the samples on the experimental results. The effect of the deformation in the bars' ends, which contacted with the samples, was also studied in the numerical models.
A series of B-C ceramics was simultaneously synthesized and densified from boron and carbon elements by using a Spark Plasma Sintering (SPS) method. A high relative density (>95%) was successfully obtained at 1900 ...
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ISBN:
(纸本)9788880800842
A series of B-C ceramics was simultaneously synthesized and densified from boron and carbon elements by using a Spark Plasma Sintering (SPS) method. A high relative density (>95%) was successfully obtained at 1900 °C. The main phases of the B-C ceramics were proved to be B4C and B13C2 with a small amount of unreacted free-C, and the grain size was ~500 nm. B/C ratios in the ceramics were measured by chemical analysis and the B/C ratio could be well controlled.
The electrostatic self-assembly of polymer on proton exchange membrane was studied by calorimetric tech-nique. The titration of poly diallyldimethylammonium chloride (PDDA) into Nation membrane was designed and perfor...
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The electrostatic self-assembly of polymer on proton exchange membrane was studied by calorimetric tech-nique. The titration of poly diallyldimethylammonium chloride (PDDA) into Nation membrane was designed and performed to determine the thermodynamic parameters. The enthalpy change △rH(○)m and binding constant K in the process of self-assembly were obtained from data analysis with the help of Origin. According to the calculated thermodynamic parameters, the electrostatic self-assembly of PDDA on the proton exchange membrane is an 'en-thalpy-driven' reaction. The released heat indicates decrease of energy, which is helpful for the occurrence of the self-assembly process, and the degree of disorder is reduced, which went against the adsorption process. As to everyion bond, the value of △rH(○)m of DDA is beyond PDDA because a small molecule can bind itself to the membranewithout steric hindrance.
Transparent Fe-doped In2O3 thin film was prepared by sol-gel method on (general) glass substrate. The structure, morphologies, transmission and magnetic properties of the sample have been characterized by X-ray diffra...
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Transparent Fe-doped In2O3 thin film was prepared by sol-gel method on (general) glass substrate. The structure, morphologies, transmission and magnetic properties of the sample have been characterized by X-ray diffraction, field emission scanning electron microscopy, UV-Vis spectroscopy and vibrating sample magnetometer. XRD result indicated that the sample was single cubic In2O3 phase. FE-SEM clearly showed that the film was homogenous and composed of refining grain with an average size of 14 nm. UV-Vis spectrum indicated that the transmittance of the film was higher than 80% in the visible light, and the Fe-doped In2O3 film arose the optical absorption spectrum red shift. VSM demonstrated the sample was (room temperature ferromagnetic.
The transition-metal carbide cemented by metal has excellent combined properties. In this study, cermets were prepared by vacuum sintering from carbide-metal composite powders. The transition- metal oxides (Cr 2O3, Mo...
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The transition-metal carbide cemented by metal has excellent combined properties. In this study, cermets were prepared by vacuum sintering from carbide-metal composite powders. The transition- metal oxides (Cr 2O3, MoO3, V2O5, Nb 2O5 and TiO2), cementing-metal oxides (Co 3O4 and NiO), and carbon black were used as raw materials to pre-synthesize composite powders such as Cr3C2-Co, Mo2C-Co, VC-Co, NbC-Co and TiC-Ni, by a direct reduction and carburization process in vacuum. Results show that the participation of Co 3O4 and NiO as well as the vacuum circumstance were greatly propitious to the carburization of transition-metal oxides into carbides. The carbothermal condition was greatly improved by the direct reduction and carburization process.
A series of samples of hexagonal boron nitride-aluminum nitride (10-90, 15-85, 20-80, 25-75, 30-70wt.%) ceramic composites were prepared by spark plasma sintering in a nitrogen atmosphere at 1650°C-1800°C fo...
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A series of samples of hexagonal boron nitride-aluminum nitride (10-90, 15-85, 20-80, 25-75, 30-70wt.%) ceramic composites were prepared by spark plasma sintering in a nitrogen atmosphere at 1650°C-1800°C for 5min. Different amounts of CaF2 were added as sintering aids. The effects of CaF2 and sintering temperature on densification and dielectric properties were discussed. The addition of CaF2 enhances relative dielectric constant and loss tangent of the samples. The increase in sintering temperature promotes the densification and decreases the dielectric loss tangent. When being sintered at 1700°C, the relative density, dielectric constant and dielectric loss tangent of the sample with 15wt.%BN are 98.04%, 7.15 and 6.31×10-4 respectively.
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