Using the molecular electronegativity distance vector descriptors derived directly from the molecular topological structures, the relative retention time （RRT） of polybrominated diphenyl ethers （PBDEs） were predic...
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Using the molecular electronegativity distance vector descriptors derived directly from the molecular topological structures, the relative retention time （RRT） of polybrominated diphenyl ethers （PBDEs） were predicted. A four-variable regression model （M30） with the correlation coefficient of 0.9816 and the root mean square errors of 0.061 was developed using a training set including 30 PBDEs. The correlation coefficient of 0.9841 and the root mean square errors of 0.054 between the values of RRT predicted by M30 and the RRT observed for 16 external PBDEs show a good predictive potential of M30. The descriptors included in the M30 represent four interactions between four pairs of atom types, i.e., atom -C= and -C=, -C= and 〉C=, 〉C= and 〉C=, -C= and -Br.
A new organic-inorganic hybrid compound （dienHs）2（P2Mo5O23） （1） [dien=NH（CH2CH2NH2）2] has been hydrothermally synthesized and characterized by elemental analyses, IR spectrum, thermogravimetric analysis, and t...
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A new organic-inorganic hybrid compound （dienHs）2（P2Mo5O23） （1） [dien=NH（CH2CH2NH2）2] has been hydrothermally synthesized and characterized by elemental analyses, IR spectrum, thermogravimetric analysis, and the single crystal X-ray diffraction technique. Compound 1 crystallizes in the triclinic system with space group P1 and a=0.9790（2） nm, b=0.9922（2） nm, c= 1.4644（3） nm, α=95.510（10）°, β=98.860（10）°, γ=95.700（10）°, V=1.3895（5） nm^3, Z=2, R=0.0465. The results show that the compound consists of dienH3^3＋＋ and P2Mo5O23^6-, and the heteropoly anion P2Mo5O23^6- is connected to a 1-D chain structure with the protonated dien by hydrogen bonds.
The high-temperature mechanical properties were very important to structural materials, especially structural ceramics. Hence, the strength, elastic modulus, stress relaxation and creep behavior of the multilayer mate...
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The high-temperature mechanical properties were very important to structural materials, especially structural ceramics. Hence, the strength, elastic modulus, stress relaxation and creep behavior of the multilayer materials at elevated temperature were studied in this paper. According to the curves of mechanical properties varieties with temperature risen from room-temperature to 1300°C, the multilayer materials could remain relatively high mechanical properties until 1150°C. Otherwise, the creep function of the multilayer composites was also determined, in which the stress exponent was 1.4 and activation energy was 204kJ/mol. By contrasting to the monolithic ceramics of Al2O3 and Ti3SiC2, the main creep mechanisms include: interface diffusion creep (in Al 2O3 layers), dislocation movement creep, grain delamination and sliding (in Ti3SiC2 layers).
In order to improve water resistance of phosphors and the stability of particles in aqueous suspensions, the phosphor particles were coated with varying amounts of silica via the hydrolysis of tetraethyl orthosilicate...
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In order to improve water resistance of phosphors and the stability of particles in aqueous suspensions, the phosphor particles were coated with varying amounts of silica via the hydrolysis of tetraethyl orthosilicate. The composite particles were characterized by transmission electron spectroscopy, BET N2 gas adsorption, sedimentation time studies and fluorescent spectrometer. The specific surface area of the silica-coated phosphor particles showed a non-systematic increase. In comparison to the uncoated phosphor (3.65m2/g), silica coatings of 13, 25, 50, 75wt% yielded specific surface areas of 15.19, 14.29, 37.90 and 226.12 m2/g respectively. This behavior can be explained based on a heterocoagulation coating mechanism in which silica clusters adsorb onto the phosphor particles surface. The sedimentation data display the stability of the coated particles improved as the silica content increased. The excitation and emission spectra show that the luminescent properties of the phosphors are unimpaired or even better. The optimum luminescent properties obtained when coating 50wt% silica after calcining at 400°C.
Effect of Li+ and Mn2+ doping on the electrical properties of SrTiO3-based varistor ceramics was investigated. The results showed that the varistor ceramics cannot possess ideal electrical properties when only Li+ or ...
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Effect of Li+ and Mn2+ doping on the electrical properties of SrTiO3-based varistor ceramics was investigated. The results showed that the varistor ceramics cannot possess ideal electrical properties when only Li+ or Mn2+ was doped. However, when Li+ and Mn2+ were properly doped together, the samples acquired excellent electrical properties: V1mA=(5.7 ∼ 11.7)V/mm;α = 6.8 ∼ 11.0;Ετ = (2.4 ∼ 4.4) × 105;tanδ= (7.1 ∼ 10.4)%. When the contents of Li2CO3 and MnCO3 were 1.00 mol% and 0.05 mol% respectively, the nonlinear coefficient a reached the largest value of 11.0. Compared with only Mn 2+ doping, the addition of Li+ increases the a value significantly.
Si-based high-temperature ceramics are attractive materials for power microelectromechanical systems (power MEMS), such as microscale gas turbines, micro-combustors and micro-reactors. This presentation introduces a n...
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Si-based high-temperature ceramics are attractive materials for power microelectromechanical systems (power MEMS), such as microscale gas turbines, micro-combustors and micro-reactors. This presentation introduces a novel process for the microfabrication of Si3N4 ceramics, which mainly consists of pre-sintering of Si powder compacts, micromachining of pre-sintered Si preforms and reaction sintering of the micromachined Si preforms. The present process has its high potential for Si3N 4 3-dimensional microfabrication because it combines the machinablity of pre-sintered Si powder compacts and near-net shaping characteristic of S3N4 reaction sintering. Si3N4 micro-components such as micro nozzle arrays and micro-rotor were fabricated by using the present process.
The TiB2/(TiB2+AlN)/AlN/(AlN+Cu)/Cu functionally graded materials were successfully fabricated via spark plasma sintering (SPS) method, in which a temperature gradient was achieved by using a specially designed mold a...
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The TiB2/(TiB2+AlN)/AlN/(AlN+Cu)/Cu functionally graded materials were successfully fabricated via spark plasma sintering (SPS) method, in which a temperature gradient was achieved by using a specially designed mold and different sintering sequences were carried out. XRD analysis and SEM observations were respectively performed upon the TiB2/AlN/Cu composites. The results show that no new phases were introduced into the composites after mechanically milling or SPS process. The layered composites were found to have a dense microstructure, which changes gradually along a composition gradient. The present FGMs are developed as electrode materials of a solar thermoelectric module.
In 2003, a joint research project entitled "Nano and graded thermoelectric materials/Photovoltaic-thermoelectric-wind power generation" is established in cooperation among research institutes from Japan and ...
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ISBN:
(纸本)0878499709
In 2003, a joint research project entitled "Nano and graded thermoelectric materials/Photovoltaic-thermoelectric-wind power generation" is established in cooperation among research institutes from Japan and China. The major research institutes include statekeylaboratory of advancedtechnology for materials Synthesis and processing (Wuhan University of technology, China), Shanghai Institute of Ceramics (Chinese Academy of Sciences, China), statekeylaboratory of new Ceramics and Fine processing (Tsinghua University, China), Japan Aerospace Exploration Agency (JAXA, Japan) and Foundation for Promotion of Japanese Aerospace technology (JAST, Japan). The main aim of this project is to develop a photovoltaic-thermoelectric-wind power generation system with high efficiency solar energy conversion. The key works of the project include: (1) fabrication of high efficiency nano thermoelectric materials with a maximum figure of merit Z≥ 1.3;(2) design and fabrication of nano graded thermoelectric material/component with efficiency conversion larger than 12% for wide temperature range and (3) design and construction of photovoltaic- thermoelectric coupled power generation system. The recent progress about the joint research project is reported in this paper. Emphasis is put on the mechanism, design and fabrication of high efficiency nano graded thermoelectric materials. The future research plan is also mentioned in brief.
CeO2-MgO (CeM), Dy2O3-MgO (DyM), Yb 2O3-MgO (YbM) and Y2O3-MgO (YM) were added into the α-Si3N4 raw powder respectively, Upon dry pressed, isostatic cool pressed and sintered with normal pressure process at the tempe...
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CeO2-MgO (CeM), Dy2O3-MgO (DyM), Yb 2O3-MgO (YbM) and Y2O3-MgO (YM) were added into the α-Si3N4 raw powder respectively, Upon dry pressed, isostatic cool pressed and sintered with normal pressure process at the temperature of 1900°C for 4 hours, the effect of sintering additives on the thermal conductivity of the silicon nitride ceramics was studied. The results show that, compared with the sample added with YM sintering additive, the sample added with DyM sintering additive has lower thermal conductivity;the sample added with CeM sintering additive exhibits the highest thermal conductivity with a value of 85.4W/m·K;the sample added with YbM sintering additive also exhibits high thermal conductivity but low bulk resistivity. The samples added with different sintering additives have similar microstructures but different grain boundary phases. Dy2Si 3N4O3, Yb2S3N 2O4 and Y2Si3N3O 4 phases are found respectively in the samples added with DyM, YbM and YM additives. Of the four sintering additives, CeM is the optimal one that helps silicon nitride ceramics obtain to higher thermal conductivity and better electrical properties.
TiO2 codoped with antimony and chromium was prepared by coprecipitation method. The different washing methods were adopted while the codoping levels were same. The results show several factors such as surface area, cr...
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TiO2 codoped with antimony and chromium was prepared by coprecipitation method. The different washing methods were adopted while the codoping levels were same. The results show several factors such as surface area, crystallinity and doping Cl- influence photocatalytic activity. Doping Cl- reduces surface area but depress the rate of electron-hole recombination and improve the photocatalytic activity. The photocatalysis by organic solvent treatment obtains higher activity because of higher surface area.
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