二次氮化法制备γ‘—Fe4N超细粉末

以ＦｅＣｌ２．ｎＨ２Ｏ和ＮＨ３为原料，采用一步气相合成法制备了Ｆｅ／Ｎ超细粉末，并研究了二次氮化法制备化铁超细粉末的工艺技术，通过比较实验，证实二次氮化法能够制备单相的γ－Ｆｅ４Ｎ粉末。利用ＸＲＤ、ＴＥＭ、ＸＰＳ和ＶＳＭ实验手段对Ｆｅ／Ｎ和γ’－Ｆｅ４Ｎ粉末的晶态、物相、形貌、成分、粒度和磁性进行了初步表征。     

AlN／SiCw（Y2O3＋SiO2）复合材料热处理增强研究

研究了热处理对ＡｌＮ／ＳｉＣｗ（Ｙ２Ｏ３＋ＳｉＯ２）复合材料机械性能的影响。结果表明，该材料经热处理后的强度提高，当添加剂Ｙ２Ｏ３／ＳｉＯ２＝１／２．５摩尔比时，提高幅度最大。经ＸＲＤ，ＳＥＭ，ＴＥＭ／ＥＤＡＸ和ＨＲＥＭ分析，热处理增强的机理主要是粒界玻璃相在高温氧化气氛中和ＡｌＮ颗粒表层作用，生成的纤维２Ｈ＾δＳｉａｌｏｎ相和ＳｉＣｗ形成空间交错结构。     

CALIXE［4］ARENE AS A TEMPLATE FOR CONTROLLING REGIOCHEMISTRY OF PHOTODIMERIZATION OF 9－SUBSTITUTED AN

ＣＡＬＩＸＥ［４］ＡＲＥＮＥＡＳＡＴＥＭＰＬＡＴＥＦＯＲＣＯＮＴＲＯＬＬＩＮＧＲＥＧＩＯＣＨＥＭＩＳＴＲＹＯＦＰＨＯＴＯＤＩＭＥＲＩＺＡＴＩＯＮＯＦ９－ＳＵＢＳＴＩＴＵＴＥＤＡＮＴＨＲＡＣＥＮＥＬＩＹＩ；ＴＯＮＧＺＨＥＮ－ＨＥ（ＣＨＥＮ－ＨＯＴＵＮＧ...     

1—2折流换热器流体温度沿程变化及其LMTD的计算

１－２折流换热器流体温度沿程变化及其ＬＭＴＤ的计算梁日忠ＴＨＥＶＡＲＩＡＴＩＯＮＯＦＦＬＵＩＤＴＥＭＰＥＲＡＴＵＲＥＡＬＯＮＧＳＩＤＰＡＳＳＡＮＤＴＨＥＣＡＬＵＡＴＩＯＮＯＦＬＭＴＤＩＮ１－２ＢＡＦＦＬＥＨＥＡＴＥＸＣＨＡＮＧＥＲ１前言换热器设计中，...     

溶胶—凝胶法合成了BaAl2Si2O8超细粉末的研究

以Ｂａ（ＯＨ）２．８Ｈ２Ｏ，Ａｌ（ＮＯ３）３．９Ｈ２Ｏ，ＴＥＯＳ为原料，采用溶胶－凝胶法制备ＢａＯ－Ａｌ２Ｏ３－ＳｉＯ２三元系粉末，研究了不同因素对生成稳定溶胶和胶化时间的影响，用ＴＧ－ＤＴＡ，ＸＲＤ研究了溶胶－凝胶的热处理过程，用ＴＥＭ观察了粉体的粒径。     

EXPERIMENTAL INVESTIGATION OF KINETIC AND TRANSPORT PARAMETERS IN A WALL－COOLED FIXED－BED REACTOR

ＥＸＰＥＲＩＭＥＮＴＡＬＩＮＶＥＳＴＩＧＡＴＩＯＮＯＦＫＩＮＥＴＩＣＡＮＤＴＲＡＮＳＰＯＲＴＰＡＲＡＭＥＴＥＲＳＩＮＡＷＡＬＬ－ＣＯＯＬＥＤＦＩＸＥＤ－ＢＥＤＲＥＡＣＴＯＲＺｈｅｎ－ＭｉｎＣＨＥＮＧａｎｄＷｅｉ－ＫａｎｇＹＵＡＮ（ＵＮＩＬＡＢＲｅｓｅ...     

二次氮化法制备γ′－Fe_4N超细粉末

以ＦｅＣｌ＿２·ｎＨ＿２Ｏ和ＮＨ＿３为原料，采用一步气相合成法制备了Ｆｅ／Ｎ超细粉末，并研究了二次氮化法制备氮化铁超细粉末的工艺技术。通过比较实验，证实二次氮化法能够制备单相的γ′－Ｆｅ＿４Ｎ粉末。利用ＸＲＤ、ＴＥＭ、ＸＰＳ和ＶＳＭ等实验手段对Ｆｅ／Ｎ和γ′－Ｆｅ＿４Ｎ粉末的晶态、物相、形貌、成分、粒度和磁性进行了初步表征。实验结果表明，二次氮化法制得的γ′－Ｆｅ＿４Ｎ为高纯、超细、单相的粉末，并且粉末的饱和磁化率σ＿３和矫顽力Ｈｃ值均优于田中隆夫等人的同类研究结果。     

激光诱导二甲基二乙氧基硅烷气相合成碳化硅超细粉

本工作首次采用有机硅试剂二甲基二乙氧基硅烷为反应物，进行了激光导气相反应，制备出平均粒径为４０ｎｍ的非晶ＳｉＣ粉末，粉末中Ｃ／Ｓｉ比随反应气流量的变化而变化。非晶ＳｉＣ粉末在１８７３Ｋ，氮气中退火１ｈ后转变为β－ＳｉＣ及α－ＳｉＣ，同时，粉末中部分氧杂质及自由碳脱出粉末。     

晶须表面涂层对SiCw／TZP陶瓷复合材料力学性能和界面结构的影响

研究了在ＳｉＣ晶须表面涂覆１０～１００ｎｍ厚的氧化铝或莫来石对１５％（ｖｏｌ）ＳｉＣｗ／２．５Ｙ－ＴＺＰ陶瓷复合材料力学性能的影响。结果表明：涂层可显改善复合材料的力学性能，其中涂覆莫来石效果最佳，室温σ１＝１４５０ＭＰａ，Ｋ１ｃ＝１７ＭＰａ·ｍ＾１／２，１０００℃下σｆ＝５２０ＭＰａ，比无涂层的复合材料力学性能分别提高了８０％，１００％和４５％。ＳＥＭ，ＴＥＭ和ＨＲＥＭ观察表明：ＳｉＣｗ表面涂     

纳米Si3N4-SiC(Y2O3)复合粉末的氨解溶胶-凝胶法合成

以硅溶胶、尿素和碳黑为原料,经氨解溶胶－凝胶、碳热还原法合成了纳米Ｓｉ３ｎ４－ＳｉＣ复合粉末。通过在硅溶胶中引入Ｙ（ＮＯ３）３,合成了Ｓｉ３ｎ４－ＳｉＣ－Ｙ２Ｏ３超细复合粉末,Ｙ２Ｏ３的加入有助于降低Ｓｉ３Ｎ４－ＳｉＣ的合成温度。采用ＸＰＳ和ＸＲＤ分析复合粉末中Ｙ的存在状态表明：一部分Ｙ固溶在Ｓｉ３Ｎ４－ＳｉＣ中,加有一部分以Ｙ２Ｏ３形式存在,Ｓｉ３Ｎ４－ＳｉＣ－Ｙ２Ｏ３复合粉末的烧结性能良好。     

Laser Synthesis of Si/C/N Powders from 1,1,1,3,3,3-Hexamethyldisilazane

Laser-driven pyrolysis of the organosilicon compound 1,1,1,3,3,3-hexamethyldisilazane ((Me₃Si)₂NH) yields amorphous fine powders (0.1 μm) containing Si, C, and N. Reactant Si and N retentions are 100% and 90%, respectively. The C content of the powder can be varied by changing the pyrolysis temperature, and the N content can be varied by adding NH₃ to the reactant gas. Upon firing, SiC is produced, with unusually facile loss of nitrogen from the powder.     

Comparison of Si/C/N pre-ceramics obtained by laser pyrolysis or furnace thermolysis

This paper reports a comparison between two different methods used for the synthesis of amorphous Si/C/N pre-ceramics: the laser pyrolysis method, coupled with an aerosol generator, and thermolysis in a furnace in an inert gas atmosphere. The same precursor, liquid oligomethylvinylsilazane (OMVS, [−(CH₃)Si(HCCH₂)NH−]_n) has been chosen to establish this comparison. Laser spray pyrolysis of OMVS produces nano-sized powder particles with a specific surface area of about 120 m²/g. The characteristics of the as-formed Si/C/N nanopowders (chemical composition, local order, structural evolution...) are compared to those of pre-ceramic samples obtained by thermolysis in a furnace (at 800 and 1050 °C). The amorphous network of the as-pyrolysed materials mainly consists of SiC_xN_4−x (x=0,1,2) units and amorphous or sp²-hybridized carbon. The carbon and hydrogen contents are higher in samples obtained by laser spray pyrolysis. Heat-treatment experiments at temperatures up to 1550 °C were performed to investigate the high temperature behaviour of the various samples. Decomposition was observed at about 1500 °C.     

原位燃烧合成Si3N4/Ti(C,N)/SiC复相陶瓷热力学分析

研究了用ＴｉＣ作添加剂时Ｓｉ粉坯在高压氮气中的燃烧行为,结果表明：ＴｉＣ加入量对燃烧合成产物的相组成有重要影响,原因在于ＴｉＣ加入量直接影响燃烧过程中氮气向反应前沿的渗透性,从而影响试样中不同部位氮气分压的变化,适当调整工艺参数,可以合成Ｓｉ３Ｎ４／Ｔｉ（Ｃ,Ｎ）／ＳｉＣ复相陶瓷,并从热力学角度对实验结果进行了合理的解释。     

Characterization of Silicon Carbide–Silicon Nitride Composite Ultrafine Particles Synthesized Using a CO2 Laser by Silicon-29 Magic Angle Spinning NMR and ESR

The structure of silicon carbide–silicon nitride (SiC–Si₃N₄) composite particles synthesized using a CO₂ laser was studied by magic angle spinning nuclear magnetic resonance (MAS-NMR) and electron spin resonance (ESR). The structure around Si atoms changed by introducing N. C atoms around Si were substituted by N atoms, and N-rich configurations around Si atoms increased stepwise as the N content increased. The low N content composite particles consisted of mainly SiC phase containing dissolved N. N atoms were partly present in β-SiC microcrystal and partly in the grain boundary layer in the particle. N atoms were tetrahedrally surrounded by four Si atoms in β-SiC microcrystal and were trivalent state bonded to three Si atoms in the grain boundary layer. The high N content particles consisted of SiC, Si₃N₄, and amorphous phases, whose amount depended on N content.     

Additive-Assisted Nitridation to Synthesize Si3N4 Nanomaterials at a Low Temperature

Starting from Si powder, NaN₃ and different additives such as N -aminothiourea, iodine, or both, Si₃N₄ nanomaterials were synthesized through the nitridation of silicon powder in autoclaves at 60°–190°C. As the additive was only N -aminothiourea, β-Si₃N₄ nanorods and α-Si₃N₄ nanoparticles were prepared at 170°C. If the additive was only iodine, α-Si₃N₄ dendrites with β-Si₃N₄ nanorods were obtained at 190°C. However, when both N -aminothiourea and iodine were added to the system of Si and NaN₃, the products composed of β-Si₃N₄ nanorods and α, β-Si₃N₄ nanoparticles could be prepared at 60°C.     

热处理对锂离子电池硅/石墨/炭负极电化学性能的影响

将天然石墨、酚醛树脂和微米级硅粉进行球磨处理制备复合材料前驱物,再于N2气氛下700℃炭化得到硅/石墨/炭(Si/G/C)复合电极材料,采用X射线衍射仪、扫描电镜和透射电镜及电化学循环充放电对其形貌、结构及其电化学性能进行表征.结果表明,Si/G/C作为锂离子电池负极材料具有高于900 mA·h/g的可逆比容量,40次循环后保持在550 mA·h/g.对电极进行热处理后,其循环性能显著提高,40次循环后比容量保持在700 mA· h/g.扫描电镜分析结果显示,热处理后集流体上电极材料分布更均匀,因涂抹不均形成的空隙不复存在.热处理后电极结构更致密、内部黏结强度增大使其结构稳定性明显提升,是电极循环性能提高的主要原因.     

Si3N4／Al反应烧结制备AIN／Al复合材料

研究了采用Si，N4与Al的混合粉，经压制、烧结制备AIN／Al-Si复合材料的技术方法。试验结果表明：AIN的反应生成机制属于一种连续渐进式反应形成过程，即于高温下液相Al中的Al原予渗入Si3N4的晶体点阵取代Si原予而逐渐使之向AIN晶体点阵转化的过程。被取代的Si原予从固相Si3N4中析出，扩散溶入液相Al中，冷却后形成Al-Si舍金固溶体，一般呈网状分布于AIN晶体相的周围。新生成的AIN与Al-Si合金相之间表现出很好的界面亲和性。     

Si3N4/Al反应烧结制备AlN/Al复合材料

研究了采用Si3N4与Al的混合粉,经压制、烧结制备AlN/Al-Si复合材料的技术方法.试验结果表明:AlN的反应生成机制属于一种连续渐进式反应形成过程,即于高温下液相Al中的Al原子渗入Si3N4的晶体点阵取代Si原子而逐渐使之向AlN晶体点阵转化的过程.被取代的Si原子从固相Si3N4中析出,扩散溶入液相Al中,冷却后形成Al-Si合金固溶体,一般呈网状分布于AlN晶体相的周围.新生成的AlN与Al-Si合金相之间表现出很好的界面亲和性.     

激光法合成SiC超细粉末物理化学过程的研究——Ⅰ.实验规律及粉末特性

用50W连续波CO_2激光器为热源,诱发SiH_4和C_2H_4反应,合成SiC超细粉末。实验确定了反应腔体内压力p、气源中的C/Si原子比、喷嘴内径2r以及激光功率密度与粉末特性之间的关系,并对合成的产物进行物理、化学表征。     

聚苯硫醚/纳米Si3N4复合材料的制备及性能研究

表面改性处理的纳米Si3N4粉体与聚苯硫醚（PPS）熔融共混挤出制成PPS/纳米Si3N4复合材料,通过拉伸、冲击实验及动态力学性能测试考察了纳米粉体加入量对复合体系各项性能的影响。结果表明,纳米Si3N4填充PPS基复合材料的力学性能明显优于纯PPS。随粉体添加量的增加,复合材料的拉伸强度增大,当添加量为0.8 %时,拉伸强度提高了22 %。随粉体添加量的增加,复合体系冲击强度增大,当粉体添加量为1.2 %时,冲击强度和缺口冲击强度出现最大值,分别比纯PPS增加了33 %和41 %。动态力学性能测试表明,随粉体添加量的增加,PPS分子链段松弛所需能量增加,松弛过程增长,体系储能模量降低,损耗模量增加。