Low temperature solid-phase sintering of sintered metal fibrous media with high specific surface area

A procedure of low temperature solid-phase sintering（LTSS） was carried out to fabricate sintered metal fibrous media（SMFM） with high specific surface area.Stainless steel fibers which were produced by cutting process were first plated with a coarse copper coating layer by electroless plating process.A low-temperature sintering process was then completed at about 800 °C for 1 h under the protection of hydrogen atmosphere.The results show that a novel SMFM with complex surface morphology and high specific surface area（0.2 m2/g） can be obtained in this way.The effect of sintering temperature on the surface morphology and specific surface area of SMFM was studied by means of scanning electron microscopy and Brunauer-Emmett-Teller.The damage of micro-structure during the sintering process mainly contributed to the loss of specific surface area of SMFM and the optimal sintering temperature was 800 °C.

电泳共沉积超细金刚石/玻璃复合涂层的研究

通过电泳共沉积技术制备超细金刚石/玻璃复合涂层,主要探讨了电泳沉积工艺及固化烧结条件对涂层的影响。超细金刚石粉体在乙醇溶液中荷负电,为阳极沉积。通过电流变化和形貌观察研究涂层沉积质量,结果表明:电压为30～50 V时,可以形成均匀平整的复合涂层。添加质量分数为0.05%～0.10%的金属阳离子能实现阴极沉积,避免了阳极腐蚀,有利于基板的选择。复合涂层最优固化烧结温度为450°C,反应时间为3 h,烧结后的涂层光滑致密且实现了金刚石在黏结相中的均匀分布。

耐温防重腐蚀涂装材料

成果简介、性能、指标: 该新型耐温防重腐蚀涂料是以多种高性能有机高分子聚合物的共混体为基体,涂装于普通金属材料(如低碳钢)表面经低温烧结固化(300～400℃)形成致密的防腐涂层,它具有优异的耐腐蚀性能,经高温静态。

Densification mechanism of stereolithographical dense Si_(3)N_(4) ceramics with CeO_(2) as sintering additive by field assisted sintering

Combining sintering additive with field assisted sintering,stereolithographical dense Si3N4 ceramics was successfully fabricated.Owing to a large amount of polymer during the stereolithography,the green parts have the characteristics of low powder loading and high porosity.Adjusting the process parameters such as sintering temperature and soaking time can effectively improve the density of the specimens.The stress exponent n of all specimens is in a range of 1 and 2,which is derived from a modified sintering kinetics model.The apparent activation energy Qd of stereolithographic Si_(3)N_(4) ceramics sintered with applied pressures of 30 MPa,40 MPa,and 50 MPa is 384.75,276.61 and 193.95 kJ/mol,respectively,suggesting that the densification dynamic process is strengthened by raising applied pressure.The grain boundary slipping plays a dominating role in the densification of stereolithographic Si3N4 ceramics.The Vickers hardness and fracture toughness of stereolithographic Si3N4 ceramics are HV10/10(1347.9±2.4)and(6.57±0.07)MPaAbstract:Combining sintering additive with field assisted sintering,stereolithographical dense Si3N4 ceramics was successfully fabricated.Owing to a large amount of polymer during the stereolithography,the green parts have the characteristics of low powder loading and high porosity.Adjusting the process parameters such as sintering temperature and soaking time can effectively improve the density of the specimens.The stress exponent n of all specimens is in a range of 1 and 2,which is derived from a modified sintering kinetics model.The apparent activation energy Qd of stereolithographic Si3N4 ceramics sintered with applied pressures of 30 MPa,40 MPa,and 50 MPa is 384.75,276.61 and 193.95 kJ/mol,respectively,suggesting that the densification dynamic process is strengthened by raising applied pressure.The grain boundary slipping plays a dominating role in the densification of stereolithographic Si3N4 ceramics.The Vickers hardness and fracture toughness of stereolithographic Si3N4 ceramics are HV10/10(1347.9±2.4)and(6.57±0.07)MPa·m^(1/2),respectively.

Application of FTIR to analysis chemical structure of soot aerosol emitted from lump-coal combustion in fixed bed

The objectives of this work are to study the primary chemical structure of soot aerosol derived from lump-coal combustion in different experimental conditions in fixed bed. A laboratory-scale movable fixed bed, water-cooled soot aerosol collection system, and electric reactor have been designed and used in the process. Three kinds of coals, sized at 3-5 ram, have been heated in the experiments. Fourier Transform Infrared Spectroscopy （FTlR） has been employed to test functional groups of soot aerosol samples. Infrared spectra from 400 to 4000 cm^ -1 and semiquantitative analysis have been employed. The results of experiments show that contents of hydrogen-bonded are increased, contents of unsaturated hydrocarbons are increased, and contents of aromatic hydrocarbons are decreased with temperature increase; contents of hydrogen-bonded and unsaturated hydrocarbons are increased first and decreased late, and contents of aromatic hydrocarbons are decreased with gases residence time extension; the contents of hydrogen bonded and unsaturated hydrocarbons derived from soot aerosol samples are higher than those from original coal samples in lower-volatile coals, and the contents of aromatic hydrocarbons derived from soot aerosol samples are lower than those from original coals; and contents of hydrogen-bonded are decreased, contents of unsaturated hydrocarbons are increased, and contents of aromatic hydrocarbons are decreased with a increase.

基于五轴联动曲面3D打印设备的纳米银导电材料固化工艺研究

利用自主研发的五轴联动曲面3D打印设备,在曲面上打印导电图形。以纳米银导电墨水为实验材料,探究了烧结功率、扫描速度、扫描间隔对导电图形制品表面质量、烧结制品线条宽度、电导率等的影响。结果表明:在烧结功率为2 W、扫描速度为4 mm/s、扫描间隔为0.3 mm的条件下,导电图形表面光滑,烧结制品线条宽度合适,电导率最高。

Solid-State 13C Nuclear Magnetic Resonance Spectroscopic Characterization of Soil Organic Matter Fractions in a Forest Ecosystem Subjected to Prescribed Burning and Thinning

Forest management practices such as prescribed burning and thinning in forest ecosystems may alter the properties of soil organic matter （SOM）. In this study, surface softs from field plots in the Bankhead National Forest, Alabama, USA, were used to investigate possible SOM transformations induced by thinning and burning. Elemental analysis and solid-state 13C cross polarization magic angle spinning nuclear magnetic resonance （13C CPMAS NMR） spectroscopy were used to characterize SOM fractions in whole soils, humic substances, and density fractions. Our data revealed that the changes in SOM fractions due to the repeated burning carried out in the forest ecosystem studied were involved mainly with alkyl C, O-alkyl C, and carbohydrate functional groups, implying that most prominent reactions that occurred involved dehydrogenation, de-oxygenation, and decarboxylation. In addition, burning and thinning might have also affected the distribution and composition of free and occluded particulate SOM fractions. The limited structural changes in SOM fractions suggested that low-intensity prescribed fire in the forest ecosystem studied will not create major structural changes in SOM fractions.