C/C-SiC梯度基复合材料氧化行为研究

研究比较了Ｃ／Ｃ－ＳｉＣ梯度基复合材料和Ｃ／Ｃ复合材料的氧化行为．实验结果表明：ＳｉＣ通过占据表面活性点提高了共沉积基体的氧化起始温度;由于减少了碳与氧的接触面积,阻挡氧化凹坑的扩展,降低了材料的氧化质量损失速率．利用ＳＥＭ观察了梯度基复合材料微观氧化过程     

加压焙烧法制备短纤维增强C/C复合材料

采用加压焙烧工艺制备了短纤维增强C／C复合材料，研究了基体材料配比及纤维含量对其力学性能的影响，结果发现，基体材料中粘接剂沥青的最佳含量为30w%，当炭纤维含量小于8．3vol%时，随着炭纤维含量的增加，复合材料的抗折强度逐渐升高，之后，随着炭纤维的体积含量的增加，复合材料的抗折强度有所下降。     

B4C／C复合材料高温氧化过程中的结构变化模型的研究

在用混合磨碎法制备Ｂ４Ｃ／Ｃ复合材料的基础上,考察了不同条件对复合材料氧化失重速率的影响,然后讨论了上述各因素对复合材料抗氧化性能的影响机制,并对复合材料结构与其自愈合功能的性进行了分析,在此基础上建立了复合材料高温氧化过程的结构变化模型。     

C—B4C—SiC复合材料抗氧化性能的研究

对碳／陶瓷复合材料（Ｃ－Ｂ４Ｃ－ＳｉＣ）的抗氧化性能进行了研究。结果表明：Ｃ－Ｂ４Ｃ－ＳｉＣ复合材料抗氧化性能比碳素材料大大提高，而且烧结助剂对Ｃ－Ｂ４ＣＳｉＣ复合材料的抗氧化性能影响很大。在复合材料中分别加入了Ａｌ，Ａｌ２Ｏ３，Ｎｉ，Ｔｉ，ＴｉＣ，Ｓｉ等不同烧结助剂，发现添加Ｎｉ的材料抗氧化性能最佳，经１０００℃氧化１５ｈ后，氧化度小于０．５％；加入Ｔｉ，Ｓｉ和ＴｉＣ的次之，不加烧结助剂的又次之     

剑麻短纤维补强环氧化天然橡胶/PVC复合材料的性能研究

研究了剑麻短纤维用量和环氧化天然橡胶（ＥＮＲ）／ＰＶＣ共混比对剑麻短纤维补强ＥＮＲ／ＦＶＣ复合材料性能的影响。结果表明,该复合材料具有同的硬度和纵向拉伸强度、较低的扯断伸长率和扯断永外变形、良好的耐油和耐老化性能。剑麻短纤维的用量宜为３０份,ＥＮＲ／ＰＶＣ的共混比宜为７０／３０。     

自烧结C,TiC／C和SiC—B4C／C材料的热处理行为

本文研究了自烧结Ｃ，ＴｉＣ／Ｃ和ＳｉＣ－Ｂ４Ｃ／Ｃ材料高处理后的行为变化，实验发现随着处理温度的升高，各类材料的收缩率和重量损失随之增加，自烧结Ｃ和ＴｉＣ／Ｃ材料的弯曲强度逐渐下降，而ＳｉＣ－Ｂ４Ｃ／Ｃ复合材料的弯曲强度在２２７３Ｋ时达到一个最高值。     

氧化气氛对B4C-SiC/C复合材料自愈合抗氧化性的影响

考察了氧化气氛对Ｂ４Ｃ－ＳｉＣ／Ｃ复合材料自愈合抗氧化性的影响,对复合材料的恒温氧化行为进行了实验研究。结果发现：在某个临界值以下,空气流量的增加主要是加速氧气向材料内部扩散。     

氧化作用对B4C／C复合材料结构和性能的影响

考察了Ｂ４Ｃ／Ｃ复合材料在８００℃、２Ｌ／ｍｉｎ干燥空气注量的氧化环境下其性能参数如重量,体积,密度,电阻率、抗压强度的变化情况。并从材料表层结构的变化解释了这些参数的变化规律。     

纤维含量对C／C复合材料力学性能的影响

研究了炭纤维含量对C/C复合材料力学性能的影响,用扫描电镜（SEM）对材料的断口进行分析,结果表明：当炭纤维的体积分数小于8.3%时,随着炭纤维体积分数的增加,复合材料的抗折强度逐渐升高;之后,随着炭纤维的体积分数的增加,复合材料的抗折强度逐渐下降,短纤维增强C/C复合材料的断口特征为大量纤维拔出,其断裂过程为界面破坏所控制。     

C/C复合刹车材料及防氧化技术研究进展

介绍了Ｃ／Ｃ复合刹车材料的发展进程,国际上主要的飞机刹车机轮公司Ｃ／Ｃ复合材料及防氧化涂料的生产技术和工艺特点,Ｃ／Ｃ复合刹车材料的特性以及国内Ｃ／Ｃ复合刹车材料制备和防氧化技术的部分情况。     

Etherification of C5- and C8-Alkenes with C1- to C4-Alcohols

Etherification of two alkenes, 2-methyl-1-butene and 2,4,4-trimethyl-1-pentene, was studied with seven different C₁- to C₄-alcohols. Although etherification was of primary interest, the isomerisation of the alkenes was the main reaction to occur. For the primary alcohols the etherification and isomerisation rates correlated well with the properties of the alcohols. Both rates increased with decreasing polarity and with increasing carbon number, acidity and Mulliken charge of the oxygen atom of the alcohol. It is difficult to distinguish the effect of each property separately, and probably the differences in the reactivities are not due to any one property alone but rather the synergy of the properties affects the reactivities. The secondary alcohols behaved in a different way than the primary ones: the etherification was almost negligible. The effect of alcohol on the isomerisation of alkenes was notable even though alcohol does not directly react in the reaction, which was concluded to be due to the stronger adsorption of the more polar alcohols which hinders the reactions of other components.     

Hydrogenation of C=C and C=O groups on ruthenium-tin catalysts

The effect of addition of tin on the catalytic activity of Ru/C catalysts has been investigated in the liquid phase hydrogenation of -methylstyrene and hydrocinnamaldehyde. On increasing the Sn content, the amount of CO chemisorbed decreases, indicating a decrease in the number of Ru surface atoms. In the hydrogenation of -methylstyrene the specific activity of Ru (calculated per Ru surface atom) remains constant regardless of the Sn/Ru ratio. An increase of specific activity is however observed in the hydrogenation of hydrocinnamaldehyde. It is suggested that tin, present mainly as Sn ions, enhances the reactivity of the C=O group.     

Electrical properties of C/C and C/C-SiC ceramic fibre composites

The electrical properties of carbon/carbon (C/C) and carbon/carbon-silicon carbide (C/C-SiC) ceramic composites were measured. The results show that the capacitance decreases rapidly with an increase in frequency and it becomes constant above a frequency of 500 kHz, whereas the dissipation factor increases with increasing frequency. C/C-SiC composites give higher value than C/C composites due to the presence of microcracks.     

Phosphorus-Containing Surfactants - Sodium Alkylphosphinates with Alkyl Chain C10, C12, C14 and C16

A group of not well known anionic phosphorus-containing surfactants have been obtained. In these surfactants the hydrophobic chain is directly linked to the phosphorus atom through a P-C bond. These products are alkylphosphinates with C10, C12, C14 and C16 alkylic chains. The products have been prepared by direct reaction between sodium hydrophosphite and the corresponding α-olefin, using tert-butyl perbenzoate as reaction initiator. Surfactants properties such as surface tension, foaming power and wetting power of the sodium and ammonium salts of all these alkylphosphinates have been measured.     

XJF-200C/150C/120C三复合挤出生产线的调试

本文介绍了北京首创轮胎公司新建工厂三复合冷喂料挤出生产线的调试情况,对三复合冷喂料挤出机基本结构、工艺特点做了概述,并且通过生产线出型胎面调试过程中遇到的问题,采取相应措施进行解决做了详细说明,通过近两年来的运行情况,总结出本生产线的使用优势。     

Pt/C,Pd/C,Pd-Bi/C催化剂的应用研究

采用浸渍法制备 Pt/C,Pd/C和 Pd- Bi/C催化剂。将三种催化剂对葡萄糖的脱氢和加氧氧化两种反应的催化效果作对比研究 ,发现三种催化剂对这两个反应有着完全相反的催化顺序 :催化脱氢时 Pt/C效率最高 ,而加氧反应中 Pd- Bi/C却具有绝对优势。为解释此结果 ,结合催化剂的表征 [2 ] ,尝试提出了催化加氧和脱氢的机理 ,并确定了 Pd- Bi/C催化剂中的最佳 Bi/Pd比和两种催化反应的最佳工艺条件。实验结论 :Pt/C用于葡萄糖催化脱氢为可行的工业化途径 ,而 Pd- Bi/C对葡萄糖的催化加氧则具有挑战酶催化过程的能力 ,有一定的市场应用前景     

炭/炭复合材料航空电刷的制备

分别用厚度为2cm的炭毡和1k炭布(2D)叠层加纵向穿刺作预制体,用软化点为140℃的中温沥青作浸渍剂,经过160℃、0.3MPa浸渍、900℃碳化、2100℃石墨化和460℃、20MPa超高压致密化等工艺的循环处理,制备了纤维体积分数为45%,体积密度为1.85～1.73g·cm-3的炭/炭复合材料航空电刷。其电学性能与优质石墨电刷相当;力学性能和摩擦性能远优于优质石墨电刷,且炭毡作预制体更优于炭布作预制体。     

Biosynthesis of Epimers C2 and C2a in the Gentamicin C Complex

Gentamicin is a broad‐spectrum aminoglycoside antibiotic widely used to treat life‐threatening bacterial infections. The gentamicin C complex consists of gentamicin C1, gentamicin C1a, and epimers gentamicin C2 and gentamicin C2a. At present there is a generally accepted pathway of gentamicin biosynthesis, except for detailed understanding of the epimerization process involving gentamicins C2 and C2a. Here we have investigated the biosynthesis of these epimers. JI‐20B—an intermediate in the gentamicin biosynthetic pathway—and its epimer JI‐20Ba were generated by in‐frame deletion within genP, which encodes a phosphotransferase that catalyzes the first step of 3′,4′‐bisdehydroxylation in gentamicin biosynthesis. GenB1 and GenB2 are aminotransferases with different substrate specificities and enantioselectivities. JI‐20Ba, containing a 6′S chiral amine, a precursor of gentamicin C2a, was synthesized from G418 by GenQ/GenB1 through sequential oxidation/transamination at C‐6′. GenQ/GenB2 catalyzed the synthesis of JI‐20B, containing a 6′R chiral amine, a precursor of gentamicin C2, from G418. GenB2 catalyzed the epimerization of JI‐20Ba/JI‐20B and of gentamicins C2a/C2.     

C／C镜筒复合材料的性能研究

镜筒是高分辨率光学望远镜中的重要零件,其选材和加工质量的好坏及刚度直接决定着最终产品的性能。本试验研究了所研制C／C镜筒复合材料的力学、热学性能,分析了体积密度、炭纤维角度变化以及最终工艺状态对c／c复合材料热膨胀系数的影响。研制的C／C复合材料试验件环向拉伸强度≥160MPa,-40E～60℃线膨胀系数仅为-0．09×10^-6 ／K,在满足各项性能指标要求的基础上,成功通过正弦、脉冲振动、动力冲击、真空出气性、光反射等一系列试验考核。     

高性能C/C复合材料制备工艺研究

对制备C/C复合材料的化学气相渗透工艺进行了系统的实验研究,着重分析了热解碳的沉积过程。研究表明,在化学气相渗透的初始阶段,热解碳主要在碳纤维表面沉积,并与碳纤维之间形成了界面结合;随后,热解碳的沉积继续填充碳纤维预制体内部的气孔。这一过程有助于缓解纤维与陶瓷基体之间的界面应力。研究表明,通过调节热解碳的沉积时间可以得到具有一定密度梯度的C/C复合材料。