Controlled Al doped Si3N4 single-crystal nanobelts were synthesized by catalyst-assisted pyrolysis of polymeric precursors. The Al-doping levels can be tailored by varying the Al concentration in the polymeric precurs...
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Controlled Al doped Si3N4 single-crystal nanobelts were synthesized by catalyst-assisted pyrolysis of polymeric precursors. The Al-doping levels can be tailored by varying the Al concentration in the polymeric precursors. The as-synthesized nanobelts were characterized by SEM, XRD, EDS, TEM and HRTEM. The single-crystal belts had perfect crystal structures with few defects such as dislocations and stacking faults. The nanobelts obtained are several tens nanometers in thickness, several hundreds nanometers in width. The growth direction of the Al doped α-Si3N4 nanobelts was [011]. The growth mechanisms of α-Si3N4 nanobelts were proposed to be solid-liquid-gas-sold (SLGS). The optical properties of Al doping Si3N4 nanobelts were measured. Current results suggested that the optical properties of the nanomaterials can be controlled by adjusting Al doping contents.
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.
To reuse roller waste as a raw material of high performance green ceramic balls,three kinds of white alumina ceramic balls whose wear resistance were 2-3 times of the best high alumina ceramic ball with90% Al2O3 were ...
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To reuse roller waste as a raw material of high performance green ceramic balls,three kinds of white alumina ceramic balls whose wear resistance were 2-3 times of the best high alumina ceramic ball with90% Al2O3 were prepared,and the Al2O3 content of the prepared balls was 75%.It is found that the effect of calcia and magnesia on the wear resistance of ceramic balls is contrast to the accepted one: the wear rate of the ceramic balls prepared in CaO-Al2O3-SiO2 system is the lowest and the wear rate of the ceramic balls prepared in MgO-Al2O3-SiO2 is the *** main crystal phase of the ceramic ball is mullite and *** ceramic ball granular is uniform and fine with 4-5 um average *** pore diameter is about 2 *** wear way of the ceramic balls is mainly transcrystalline fracture.
This paper discusses the present status of, and future perspectives on nano Traditional Chinese medicine (TCM) by describing the concept, its methodologies, preservation, drug effect and pharmacological study. The exp...
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