C/C-ZrB2-ZrC-SiC超高温复相陶瓷基复合材料的性能

以聚合有机锆烷、聚合有机硼氮锆烷与聚碳硅烷组成的共溶前驱体为原料,采用化学气相渗透和聚合物浸渍裂解工艺制备了C/C-ZrB2-ZrC-SiC超高温陶瓷基复合材料,对其物相组成、微观结构、力学性能和抗烧蚀性能进行了研究. 结果表明,所制材料基体由ZrB2和ZrC纳米颗粒均匀弥散分布于连续的SiC相中构成. 随热解炭含量增加,材料的弯曲强度和断裂韧性皆呈先上升再下降的趋势,其含量为22.3%(j)的材料的力学性能最优,弯曲强度和断裂韧性分别为127.9 MPa和6.23 MPa×m1/2,且具有假塑性断裂特性. 材料在1800~2200℃等离子弧中1000 s的线烧蚀率小于1.67 mm/s,质量烧蚀率小于1.66 mg/s.     

纳米炭粉改性炭布/苯并噁嗪复合材料性能研究

研究了纳米炭粉对炭布/苯并噁嗪复合材料层间性能和烧蚀性能的影响.结果表明,当纳米炭粉含量为5%时,发布/苯并噁嗪复合材料的层间剪切强度提高26%达到30.3MPa,氧-乙炔线烧蚀率降低23%为0.0154mm/s.700℃高温处理后.改性后的复合材料有着较高的强度保留率.     

先驱体浸渗裂解法制备C/C-SiC复合材料的烧蚀性能

用先驱体浸渗裂解法制备了碳纤维增强碳(carbon fiber reinforced carbon,C/C)-SiC复合材料,用H2-D2火焰法检测其烧蚀性能.结果表明:C/C-SiC复合材料的烧蚀率随复合材料中的Si含量的增加而呈下降趋势;经过5次浸渍,C/C-SiC复合材料的密度从1.46 g/cm3增加到1.75 g/cm3,Si含量从5.06%增加到13.8%,线烧蚀率和质量烧蚀率分别下降474%和34.5%.密度为1.75g/cm3的C/C-SiC复合材料,其线烧蚀率和质量烧蚀率分别为2.22 μm/s和1.289 mg/s,其线烧蚀率和质量烧蚀率分别为密度1.78 g/cm3的C/C复合材料的21.7%和78.6%.基体中SiC的引入明显提高了C/C复合材料的抗氧化烧蚀性能.     

C/C–ZrB_2–SiC复合材料的制备及其性能

结合化学气相渗透工艺(chemical vapor infiltration)与前驱体浸渍裂解(precursor infiltration and pyrolysis,PIP)工艺,制备了C/C–Zr B_2–Si C复合材料,并对材料的力学性能和烧蚀性能进行了分析。结果表明:PIP工艺制备的C/C–Zr B_2–Si C复合材料的拉伸、弯曲及剪切强度分别为91.2、214和35.8 MPa,优于通过浆料浸渍工艺制备的复合材料。同时,热流3 200 k W/m~2,时间600 s的氧乙炔火焰试验表明,PIP工艺制备的C/C–Zr B_2–Si C复合材料具有良好的抗氧化烧蚀性能,其线烧蚀率和质量烧蚀率分别为0.002 mm/s和0.7 mg/s。     

碳/碳复合材料SiC–HfSi_2–TaSi_2抗烧蚀复合涂层

采用包埋技术在碳纤维增强碳(carbon fiber reinforced carbon,C/C)复合材料表面制备了碳化硅-硅化铪-硅化钽(SiC-HfSi2-TaSi2)抗烧蚀复合涂层.采用氧已炔火焰烧蚀试验评价了. C/C复合材料样品的抗烧蚀性能.通过X射线衍射分析、扫描电镜观察及能谱分析研究了SiC-HfSi-TaSi2作为 C/C复合材料抗烧蚀涂层的表面和断面相组成、元素分布及形貌.结果表明:由于烧蚀过程中生成的Hf02,Ta205具有高温稳定性,使得该涂层表现 出良好的抗烧蚀性能,在3 000℃下烧蚀20s后,线烧蚀率为0.009 mm/s,质量烧蚀率为0.003 85 g/s.     

硼化锆基碳化硅复相陶瓷

以钇铝石榴石(yttrium aluminum garnet,YAG)为烧结助剂,通过无压烧结工艺制备了ZrB2-SiC复相陶瓷.研究了复相陶瓷的相组成、抗烧蚀性能以及烧结助剂含量、烧结温度对复相陶瓷力学性能和显微结构的影响.结果表明:复相陶瓷的物相组成主要为ZrB2,SiC和少量玻璃相;添加YAG或提高烧结温度能使材料的晶粒显著长大,并显著提高材料的相对密度和力学性能.当YAG含量为9%(质量分数),烧结温度为1 800℃时陶瓷的相对密度为97.1%、Rockwell硬度HRa为88、弯曲强度为296MPa、断裂韧性为5.6MPa·m1/2.复相陶瓷具有优异的超高温抗烧蚀性能,在2800℃烧蚀30min,烧蚀率仅为0.001 mm/s,烧蚀后的显微结构呈现复杂的多层结构.     

醋酸锆改性酚醛树脂复合材料的性能研究

以玻璃纤维(GF)为增强材料,制备了玻纤/醋酸锆改性酚醛树脂(GF/ZPF)复合材料,考察了树脂中锆含量对复合材料弯曲强度、线烧蚀率的影响以及复合材料线烧蚀率和烧蚀形貌随烧蚀时间的变化。结果表明,ZPF在1000℃的残炭率为68.7%,相比纯酚醛树脂(PF)提高了21.7%;当树脂中锆含量为14%时,GF/ZPF复合材料的弯曲强度达到最高值642MPa;当锆含量由10%增加到15%时,GF/ZPF复合材料的线烧蚀率由0.0305mm/s降低到0.0208mm/s;随着烧蚀时间的延长,GF/ZPF复合材料的线烧蚀率基本没有变化,表明GF/ZPF复合材料具有优异的耐烧蚀性能。     

碳/碳复合材料SiC-HfSi_2抗烧蚀复合涂层(英文)

为改善碳/碳(C/C)复合材料的抗烧蚀性能,采用包埋技术在C/C复合材料表面制备了碳化硅-硅化铪(SiC-HfSi2)抗烧蚀复合涂层。采用氧乙炔火焰烧蚀试验评价了C/C复合材料样品的抗烧蚀性能。通过扫描电镜观察、能谱分析及X射线衍射分析研究了烧蚀前后C/C复合材料抗烧蚀涂层的表面和断面形貌、元素分布和相组成。结果表明:涂层C/C复合材料在烧蚀后其表面出现了丛生的氧化硅纳米线。同时,与未涂层C/C复合材料相比,SiC-HfSi2涂层使C/C复合材料的质量烧蚀率下降了85.6%。     

石英纤维增强可瓷化硼酚醛耐烧蚀复合材料研究

以硼酚醛树脂为基体,石英纤维为增强体,氧化硅、石墨及云母为陶瓷填料制备了可瓷化复合材料。通过1 400℃下烧结前后材料的力学性能测试、氧-乙炔焰(2 100℃)烧蚀性能测试,扫描电镜、热重分析及X射线衍射分析研究了不同含量陶瓷填料对石英纤维增强可瓷化硼酚醛树脂复合材料性能的影响。结果表明,常温下石英纤维增强可瓷化硼酚醛树脂复合材料的弯曲强度随着陶瓷填料含量的增加呈先升高后降低的趋势,最高可达到220.62 MPa,经过1 400℃马弗炉烧蚀后,弯曲强度最高可达19.10 MPa。随着陶瓷填料含量的增加,复合材料的耐烧蚀性能提高,质量烧蚀率和线烧蚀率最低可分别达到0.050 g/s和0.0187 mm/s。陶瓷填料经1 400℃高温处理后在一定程度下可生成SiC,使材料转变为含碳化硅的陶瓷基复合材料,提高了复合材料的弯曲强度、耐烧蚀性和耐高温性。与通常碳化硅陶瓷复合材料相比,该制备工艺简单,可大规模生产,实现了陶瓷基复合材料的低成本化。     

合金反应熔渗法制备C/C-HfC复合材料微观结构及抗烧蚀性能

发展了一种Hf C改性C/C复合材料的快速低成本合金反应熔渗制备技术,采用反应熔渗铪基合金制备了性能优异的C/C-Hf C复合材料。XRD分析表明C/C-Hf C复合材料由C、Hf C、Zr C和Si C相组成。合金反应熔渗过程中,合金熔体与热解碳反应形成了层状的基体显微组织。采用激光烧蚀法测试了C/C-Hf C复合材料的抗烧蚀性能,烧蚀60 s后C/C-Hf C复合材料的线烧蚀率为0.008 mm/s,明显低于C/C复合材料预制体的线烧蚀率0.024 mm/s。激光烧蚀后复合材料烧蚀表面形成了一层Ta2O5和Hf O2相组成的抗烧蚀层,有效减小了C/C-Hf C复合材料进一步的烧蚀破坏,大大提高了C/C-Hf C复合材料的抗烧蚀性能。     

ZrB2质与TiB2质耐火材料

介绍了ZrB2 与TiB2 以及其他一些非氧化物高温材料的性质 ;ZrB2 与TiB2 在高温工业中的应用与预期发展 ;ZrB2 与TiB2 原料与制品的生产 ,包括自蔓延高温合成ZrB2 与TiB2 ;ZrB2 质与TiB2 质复合材料 ,如ZrB2 -SiC ,TiB2-SiC ,ZrB2 -BN ,TiB2 -BN ,ZrB2 -MoSi2 ,TiB2 -MoSi2 ,ZrB2-C ,TiB2 -C ,ZrB2 -B4C ,TiB2 -B4C等。     

Electronic Structure and Properties of the O2+2, SO2+ and S2+2 Diatomic Dications

Multiply charged ions show novel energetic features which can potentially have useful photophysical properties. In order to investigate these interesting type systems, energy interaction curves for the ground and excited electronic states of O²⁺₂, SO²⁺, and S²⁺₂ have been generated by the ab initio complete active space multiconfiguration self-consistent field (CAS-MCSCF) method. The calculations were carried out in a triple-zeta sp plus double-zeta d Gaussian function basis set using compact effective potentials to replace the core electrons. In order to gauge the accuracy of the results, analogous calculations were carried out on the valence isoelectronic N₂ and NO⁺ systems for which experimental information is available for comparison of geometric and spectroscopic properties. Diverse high energy spectroscopy experiments on O²⁺₂ are interpreted and reconciled using the calculated ground and excited state energy interaction curves. Special attention is paid to the ₃Σ₊^u state, whose location and character have been particularly puzzling. Almost all the dication molecular states studied show the characteristic avoided crossing of diabatic states which gives a trapped equilibrium structure and a barrier to dissociation. These features make the dication kinetically stable, but thermodynamically unstable with an exothermic dissociation energy. The spectroscopy experiments on O²⁺₂ show that these states are experimentally attainable.     

Eu~(2+)掺杂SrSi_2O_2N_2和Sr_(0.37)Ba_(0.60)Si_2O_2N_2荧光粉的发光性能及应用

采用高温固相法合成Sr_(0.97)Eu_(0.03)Si_2O_2N_2和Sr_(0.37)Ba_(0.60)Eu_(0.03)Si_2O_2N_2荧光粉,通过X射线衍射、激发光谱、发射光谱及转换后LED器件的性能等研究了荧光粉的结构、发光性能和稳定性。结果表明:在稀土Eu2+掺杂的Sr Si2O2N2荧光粉中,当部分Sr2+被Ba2+取代后,形成三斜晶系的Sr_(0.37)Ba_(0.60)Eu_(0.03)Si_2O_2N_2荧光粉,激发和发射光谱红移,在近紫外-蓝光区具有更高的激发效率。将2种荧光粉与Ga(N)In芯片封装,Sr0.37Ba0.60Eu0.03Si2O2N2荧光粉转换的白光LED器件,在光效、显色指数和光效维持特性方面均高于Sr_(0.97)Eu_(0.03)Si_2O_2N_2转换的LED器件。     

沉淀法白炭黑与纳米级二氧化硅

依据二氧化硅粒子的形成过程，指出传统沉淀法白炭黑并不具有科学意义上的纳米实质，研究重点侧重于改进其分散性能，同时也简介了纳米二氧化硅的制备方法及用途。     

多卤代吡啶选择性合成醚类的反应

以KOH为碱,DMSO为溶剂,在空气中,温度为50℃的条件下,多卤代吡啶和苯酚类化合物反应,形成相应的醚类化合物,该反应具有很好的收率以及区域选择性,是一种有效构建C-O键的方法;以K_2CO_3为碱,DMSO和H_2O为溶剂,在空气中,室温下,多卤代吡啶和苯硫酚类化合物反应,形成相应的的吡啶硫醚化合物,该反应也具有很好的收率以及区域选择性,是一种有效构建C-S键的方法。     

Separation and purification of aflatoxins B1, B2, G1 and G2, and comparison of semi-synthetic aflatoxins B2 and G2 with naturally-occurring aflatoxins B2 and G2

A method is described for the isolation of highly purified aflatoxins B₁, B₂, G₁ and G₂ from extracts ofAspergillus flavus. The four aflatoxins, isolated from background impurities by rapid passage of the extracts through an acid alumina column, are separated from each other by chromatography on a silica gel column. Aflatoxins B₂ and G₂ are prepared by hydrogenation of the mixture of aflatoxins B₁, B₂, G₁ and G₂ and then separated by elution from a silica gel column with chloroform containing 0.7% ethanol. A comparison of semi-synthetic aflatoxins B₂ and G₂ with naturally-occurring aflatoxins B₂ and G₂ shows no significant difference in physical properties. Presented at the AOCS-AACC Meeting, Washington, D.C. April, 1968.     

氢氧直接合成法制过氧化氢技术进展

氢气和氧气直接合成过氧化氢是典型的原子经济性反应，因过程简单、产品清洁、生产成本低而成为催化领域研究开发的一个热点。总结了该法近年来在催化剂活性组分的选取及载体方面的进展；详细介绍了溶剂的选取和反应机理；讨论了各种反应器的安全性。指出今后的研究重点是提高氢气利用率、开发新型的反应器、提高过程的安全性。     

Solubility and microstructural development of TiO2-containing 3Al2O3·2SiO2 and 2Al2O3·SiO2 mullites obtained from single-phase gels

The interdependence of the titanium oxide amount and the anisotropic growth of mullites prepared from single-phase gels were investigated. Gels with stoichiometries 3(Al_2−xTi_xO₃)·2(SiO₂) and 2(Al_2−xTi_xO₃)·(SiO₂), with 0 ≤ x ≤ 0.15 were prepared by the semialkoxide method. Gels and specimens heated at temperatures between 1200 and 1600 °C were characterized by using infrared spectroscopy (IR), X-ray diffraction (XRD) and transmission and field emission scanning electron microscopies (TEM and FESEM). Al₂TiO₅ as minor impurity was detected in both series of mullites for gel precursor compositions x = 0.10 and x = 0.15, obtained at temperatures between 1200 and 1600 °C. Variations of lattice parameters of mullite, processed at temperatures from the range between 1400 and 1600 °C, with the starting nominal amount of titanium oxide indicated that the solubility limit of titanium oxide was in ranges 3.8–4.1 and 4.1–4.4 wt% TiO₂ for 3:2 and 2:1 mullites series, respectively. The anisotropic growth of titanium-doped mullite crystalline grains was significant only when the nominal amount of titanium oxide exceeded the limit of solubility into the mullite structure (for both mullite series). Stronger anisotropy occurred for the 3:2 series specimens, i.e. for the SiO₂-richer mullites. In both series of mullites, the anisotropic grain growth was observed for the process temperatures higher than 1400 °C; the crystalline grains of mullites processed at lower temperatures were equiaxials and of almost the same size.     

生产乙炔对电石的要求及乙炔清净

目前国内外乙炔大部分仍是由电石制得。然而由于工业电石除CaC2 外还含有很多杂质 ,所以生产乙炔不仅要求电石的纯度、粒度 ,还要求水温。一般电石的块度采用 8～ 2 5mm ,发生器温度控制在 85± 5℃ ,乙炔气体中含H2 S、H3 P、NH3 等气体会使氯乙烯合成氯化催化剂活性下降。因此 ,必须对乙炔气体进行清洁。采用次氯酸钠液体的氧化性将乙炔中的杂质氧化成酸性物质而除去。