工艺参数对反应烧结碳化硅结构的影响

文中列出了利用岩相Ｘ射线结构分析、化学分析及光谱分析方法，对采用碳化硅颗粒及其与石油焦混合物压制成型的坯体。在硅硅烷融物及硅蒸气中通过反应烧结制成的碳化硅材料的结构及石油焦的配比，碳化硅颗粒及碳素颗粒的粒度、压制成型坯体的密度及反应烧结温度等，便可调节反应烧结碳化硅材料的结构和组成，实验证明，在石油焦与硅发生反应烧结事成致密的碳化硅骨架，而残余的气孔被未化合的硅所充填。单相材料采用此种方法可以制成     

莫来石-氧化锆-硅-碳系统的合成和性能

以不同比例的碳化硅合成物为基础的莫来石-氧化锆-碳化硅,由像锆粉末、硅线石粉末、氢氧化铝凝胶、铝粉和碳化硅颗粒初级粒子材料相互作用生产而成。这些材料混练后成型,在1450℃、1550℃和 1650℃的温度下烧结。观察了烧结收缩、体积密度、显气孔率和比重。通过扫描式电子显微镜和X射线检验来研究烧结物的显徽结构和桕的发展。人们发现莫来石结晶的相关比例和生长与碳化硅含量和烧结温度有关。     

反应烧结碳化硅高温性能的研究进展

反应烧结碳化硅具有优良的力学性能、抗侵蚀性能和抗氧化性能等优点,是一种高致密度、低成本和净尺寸成型的材料.但由于反应烧结法的特殊工艺,反应烧结碳化硅中常含有较多游离硅,严重损害了材料的高温性能.主要阐述了反应烧结碳化硅高温力学性能、抗氧化性能、导热性能和抗热震性能的研究现状,并总结了近年来降低游离硅含量、提高反应烧结碳...     

金刚石与硅烧结制备金刚石/碳化硅复合材料

采用硅粉和金刚石微粉为原料,在氩气保护的管式气氛炉中烧结制备得到金刚石/碳化硅(Diamond/SiC)陶瓷复合材料。结果表明:硅粉与金刚石的混合料,在1410℃进行气氛烧结后,物相图谱中并未有SiC的特征峰出现;烧结温度为1450℃时,在金刚石表面会有SiC物相生成,且随温度提高,金刚石/碳化硅(Diamond/SiC)陶瓷复合材料产物中碳化硅的含量也会相应增加。在硅粉与金刚石微粉的混合料中,添加适量的铝粉(7wt%),然后在1300℃、1350℃和1410℃氩气保护气氛条件下进行烧结,均有SiC物相生成;与未添加铝粉的混合料烧结产物相比,铝粉的添加促进碳化硅在低于硅熔点(1410℃)的气氛烧结下生成,且添加铝粉的混合料烧结产物中碳化硅含量普遍提高,在烧结温度为1410℃时,SiC含量最高达55.7wt%,生成的碳化硅完整地包覆在金刚石表面。     

原料体系对Ti3SiC2合成过程中相组成和显微结构演变的影响

分别以粉末钛粉、硅粉、石墨和钛粉、碳化硅、石墨为原料,采用热压烧结法制备了Ti3SiC2材料,借助XRD和SEM手段研究了原料体系和烧成温度对试样相组成、致密化程度和显微结构的影响,并分析了反应烧结机理。结果表明:(1)随着温度的升高,钛粉-硅粉-石墨体系较钛粉-碳化硅-石墨体系合成出的Ti3SiC2块体材料纯度更高;(2)钛粉-硅粉-石墨体系在烧结温度低于1300℃时,主要以Ti5Si3、TiC和残余的硅粉、石墨反应生成Ti3SiC2,在烧结温度为1300～1600℃时,主要以形成的液相Ti-Si(L)与TiC反应生成了Ti3SiC2;钛粉-碳化硅-石墨体系在1485℃液相出现之后,颗粒经历重排和溶解再析出的过程,在液相中生成Ti3SiC2。     

锂辉石对碳化硅基复相陶瓷热膨胀及显微结构的影响

采用近零膨胀材料β-锂辉石作为高温结合剂，通过常压烧结制备碳化硅基复相陶瓷材料，研究β-锂辉石质量分数为25%～40%、烧结温度为1 500～1 600℃复相陶瓷的致密性、显微结构和热膨胀系数。结果表明：β-锂辉石高温熔融产生液相能包裹碳化硅颗粒，烧结过程中锂辉石的相变在一定程度提高了材料致密性。复相陶瓷中玻璃相含量是引起热膨胀系数升高的主要原因。当β-锂辉石添加比为35%时，在1 600℃烧结下的复相陶瓷的热膨胀系数低于1 550℃,且杨氏模量有小幅增加。     

反应烧结碳化硅的显微组织及其导电性的研究

研究了液态硅参与下的反应烧结碳化硅的工艺参数、显微组织对其电阻率的影响.随着烧结气氛压力和成型压力增加,反应烧结碳化硅中游离硅量减少,电阻率增加.其烧结机理以碳的溶解及碳化硅的淀析过程为主.     

微氧化对反应烧结碳化硅结构与性能的影响（英文）

以短切碳纤维为增强体,采用注浆成型和熔融硅渗透法制备了短纤维增强反应烧结碳化硅陶瓷,研究了微氧化对反应烧结碳化硅复合材料结构与性能的影响。结果表明:1 100℃微氧化处理,使反应烧结碳化硅复合材料表面形成了致密氧化硅薄膜,表面游离硅升华,同时,短纤维体积明显增加。微氧化处理使二氧化硅薄膜晶化产生方石英相,且方石英相含量随短纤维含量的增加而减少。微氧化产生的氧化硅薄膜能弥合材料表面微缺陷,当短纤维体积分数为30%时,反应烧结碳化硅的断裂韧性增加到5.8 MPa·m~(0.5)。     

信息集锦

滑石对细粉和粗粒两种Al2O3液相烧结的影响添加滑石后,细粉Al2O3（平均颗粒尺寸0.31μm）和粗粒Al2O3(平均颗粒尺寸4.49μm)液相烧结时有不同的致密化行为,微观结构的演变也有差别。滑石加入量为0wt%,5wt%,10wt%,在不同温度下烧结2小时。实验结果表明粗粒Al2O3中加入5wt%滑石时,在高于液相形成温度下,由于液相中晶粒的重排促进了致密化的快速进行;而当加入10wt%的滑石时,由于液相比例的增加极大地促进了致密化过程。对于细粉Al2O3来说,由于颗粒相对微细,有较高的活性,并有较大的烧结驱动力,适合低于液相形成温度致密化,而在…     

专利信息

纯碳粉水基分散一步法制造反应烧结碳化硅陶瓷材料的方法一种用水为分散剂,以纯碳粉取代碳化硅粉制造高性能反应烧结碳化硅陶瓷的方法,采用添加外加剂的方法制成高分散的水基泥浆(料),采用注浆、挤塑、凝胶注成型的方法制成生坯,用控制粉料粒径以及烧蚀剂、填充剂加入量的方法,调整生(素)坯的孔径分布和单位体积碳含量,生坯经干燥后,经1550～1650℃真空下或1850～2050℃氩气气氛下渗硅烧结2h,制得反应烧结碳化硅陶瓷材料。一种泡沫剂及其制备方法本发明公开了一种泡沫剂及其制备方法,其主要组成及含量为(重量百分比):骨胶1.55%～1.65%,松香3…     

Growth of Alumina/Metal Composites into Porous Ceramics by the Oxidation of Aluminum

Alumina/metal composites were grown into the pores of porous alumina, porous aluminosilicate, and porous silicon carbide substrates through the oxidation of Al–Si (5 wt%) powder compacts coated with magnesia powder (11 mg/ cm²). The thickness of the resulting composite increased with oxidation time and temperature, and was proportional to (pore size)^0.5 on using porous alumina. The composite thickness was more than 2 times larger in the silicon carbide and about 4 times larger in the aluminosilicate than in the alumina at 1523 K for 1 h. The products using these three types of substrates consisted of alumina, aluminum, and silicon, except that a silicon carbide phase occurred when using the silicon carbide substrate. Silica and mullite in the aluminosilicate substrate changed to silicon and alumina, and silica in the silicon carbide substrate changed to silicon because of the reduction by aluminum.     

铝粉对刚玉-氮化硅复合材料微观结构和性能的影响

借鉴"过渡塑性相工艺"思想,在刚玉-氮化砖复合材料中引入12.5%(质量分数)的铝粉,研究了铝粉对刚玉-氮化硅复合材料成型性能以及1 600℃空气中烧成后样品的体积密度、显气孔率和耐压强度的影响:利用X射线衍射仪和扫描电镜对材料的物相和微观结构进行了分析.结果表明:在刚玉-氮化硅复合材料中引入铝粉,有利于成型过程中孔隙...     

Preparation of aluminum/silicon carbide metal matrix composites using centrifugal atomization

This paper describes the development of a new technique to produce metal matrix composites (MMCs) by injecting silicon carbide particles into molten aluminum just prior to centrifugal atomization. A centrifugal atomization apparatus has been constructed for this study. Silicon carbide particles are injected during atomization of 6061 aluminum alloy to form metal matrix composite powder. The prepared aluminum/silicon carbide powder contains 18 vol.% of SiC particles and 1.2 vol.% of voids. The particle grain size is almost independent from the particle size.     

复合抗氧化剂对Al2O3-SiC-C砖性能的影响

以均化矾土、板状刚玉、碳化硅、石墨为主要原料,利用酚醛树脂作为结合剂,研究了复合抗氧化剂(硅粉、铝粉、碳化硼)的引入形式及加入量对Al2O3-SiC-C砖的性能影响.结果表明:添加复合抗氧化剂可提高Al2O3-SiC-C砖的高温抗折强度,随铝含量的增加,对提高高温抗折强度的提高越明显;抗氧化效果从强到弱依次为:添加碳化硼的复合抗氧化剂>复合铝硅抗氧化剂>金属铝>金属硅;在复合抗氧化剂中引入碳化硼能够有效的提高Al2O3-SiC-C砖的抗渣侵蚀性能及热震稳定性.     

沉钒废水除硅制备冶金级氢氧化铬研究

研究了以石灰为脱硅剂,采用石灰+片碱（氢氧化钠）沉淀法脱除沉钒废水中的硅,以除硅液为原料制备冶金级氢氧化铬。结果表明,先用石灰调节pH为7.5~8.0,再用片碱调节pH为9.5以上,除硅温度为55~65 ℃,除硅时间为20~30 min,在此条件下除硅率达到67.9%。沉钒废水用石灰除硅后制备的氢氧化铬硅含量低,以二氧化硅质量分数计达到4.2%,可用于冶炼焊剂用、铝剂用金属铬的原料。     

纳米氮化铝的氨热合成及其光致发光

采用金属铝为前驱物,在450℃的氨热条件下,获得了高质量的氮化铝纳米粉体,测量了合成粉末的X射线衍射谱、光致发光谱和高分辨透射电子显微镜（HRTEM）,发现合成的粉末是平均粒度为32nm的纤锌矿结构的氮化铝,此AlN中存在蓝光发光带,另外,讨论了AlN在高压釜内的低温氨热合成机制。     

Polymer/metal interpenetrating phase composites prepared via γ‐ray initiated in‐situ emulsion polymerization

The poly(methylmethacrylate)/metal and poly(butylacrylate‐co‐styrene)/metal interpenetrating phase composites (IPCs) were prepared via γ‐ray irradiation in‐situ bulk and emulsion polymerization, respectively. The monomers were first introduced into open‐cell aluminum foam and aluminum alloy foam and were in‐situ polymerized by γ‐ray irradiation at room temperature. The characterization and compressive test results showed that this method expands the variety of the polymer component resulting in a useful range of physical properties of the IPCs, such as density and porosity. The PMMA/metal IPC has a high polymer filling ratio, modulus and exhibits a similar compressive behavior to that of PMMA. On the other hand, the P(BA‐co‐St)/metal IPC has a relatively low polymer filling ratio and its compressive behavior is similar to that of metal foam matrix, but it has wider plastic plateau than the component metal foams, like the case of metal foam filled with rubber. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Synthesis of Glass-like Cordierite from Metal Alkoxides and Characterization by 27Al and 29Si MASNMR

A sol-gel process for the preparation of glass-like cordierite and ceramic oxide powder is described. Metal alkoxide precursors were dissolved in 2-methoxyethanol and the metal cations were complexed using 2,4-pentanedione to overcome different hydrolysis rates of metal alkoxides which lead to microscopic inhomogeneities during gelation. Heating the gel in an aerated furnace resulted in ultrafine cordierite powder of stoichiometric composition at a relatively low temperature. Cordierite gel and glass were also prepared by other methods and compared with the above gel. The environments of aluminum and silicon in the glass and gels heated at various temperatures were studied using ²⁷Al and ²⁹Si magic angle spinning nuclear magnetic resonance (MASNMR) spectroscopy. Most of the heated gels and the glass showed resonances due to pentacoordinated aluminum along with 4- and 6-coordinated aluminum. The homogeneities of the resulting gels and glass are compared using the MASNMR data.     

Formation of Reaction-Bonded Silicon Nitride Using Microwave Heating

Rod-shaped silicon compacts were nitrided in a microwave applicator using a minimum of insulation in order to maximize the temperature gradients to effect an inside-out reaction. These specimens exhibited very nonuniform conversion to Si₃N₄, and fully nitrided areas had poor microstructures consisting of alternating regions of high and low density. The key factor was found to be sintering of the silicon powder during initial heating which caused the specimens to be electrically conducting during the early stages of the reaction and led to large changes in the microwave heating behavior of the specimens as they nitrided. The temperature and composition profiles in the specimens were simulated using a numerical model. The results of the model indicated that the observed microstructures were caused by high temperatures and temperature gradients in the areas of maximum nitridation rate which caused silicon vapor to diffuse within the specimens. Some compacts were made from a mixture of silicon powder and silicon nitride powder to avoid sintering of the silicon particles. These specimens nitrided uniformly with inside-out composition profiles, indicating that microwave heating would be beneficial for the nitridation of pure silicon powder compacts if sintering could be avoided.     

冶金法制备太阳能硅过程的湿法除硼研究

湿法提纯作为冶金法路线制备太阳能级硅前处理工序,可去除大部分铁铝等碱金属及硼杂质,提高最终产品收率。实验考察了湿法除硼过程主要工艺因素:浸出剂浓度、温度、时间、搅拌等对产品纯度的影响,采用SEM对产品进行表征。当工艺条件为c(HNO3)=6.5 mol/L,c(H2SO4)=6 mol/L,温度120℃、时间4 h,处理后产品中杂质质量分数为3.574×10-6,湿法过程单元的去除率为44.58%。实验结果为高等级太阳能级硅制备工业化开发大幅度降低成本提供了技术基础。