热处理对D618堆焊层组织和性能的影响

研究了高碳高铬铸铁型硬质合金堆焊层在不同热处理条件下的组织、硬度与耐磨性。研究结果表明D618硬质合金堆焊层经850℃加热后空冷或850℃加热后油冷＋400℃回火，具有较高的硬度和优异的耐磨蚀磨损性能，比35CrMo低合金钢碳氮共渗（850℃油冷＋200℃回火）后的耐腐蚀磨损性能提高3－12倍。     

冷轧15钢的高压热处理研究

对原始组织为马氏体的冷轧15钢在CS-IB型六面顶压机上进行了高压热处理,测量试样的维氏硬度。采用X射线和TEM对其晶体结构和组织形貌进行了分析。实验结果表明:试样在6GPa实验压力下于350℃发生了回复;450￣650℃发生了再结晶;750￣850℃发生了马氏体相变,产物为具有体心立方结构的针状马氏体和具有密排六方结构的网格状马氏体。伴随组织的变化,试样硬度先升高后降低再升高。     

Simulations of the dielectric constant of bonding materials and field emission properties of CNT cathodes

The effect of the dielectric constant (k) of bonding materials in a screen-printed carbon nanotube (CNT) cathode on the field enhancement factor was investigated for high-efficiency CNT cathodes using the ANSYS software. The values obtained by a simulation study were compared to the experimental results obtained for screen-printed CNT cathodes. The field enhancement factor increased as the dielectric constant decreased, reaching a maximum value at a dielectric constant of 1, the value for a vacuum. The findings indicate that the larger sheet resistance of the bonding materials, after the firing process, can be attributed to the larger emission current of the CNT cathode. From these results, it was concluded that the best bonding materials for screen-printed CNT cathodes should have a low dielectric constant and a high sheet resistance. This finding can be used as criteria for selecting bonding materials for use in CNT pastes for highly efficient CNT cathodes.     

Effect of gas composition on cementite decomposition and coke formation on iron

Cementite decomposition and coke formation in the metal dusting process of iron were investigated at 700 °C in CO-H₂-H₂O gas mixtures. The presence of graphite deposited on the surface initiates the decomposition of cementite into iron and graphite. The morphology of the reaction products varies with gas composition. For CO concentrations less than 5 vol%, particles of iron or even closed iron layers have been observed at the cementite/graphite interface. With increasing CO content the amount of iron in the interface decreases. At CO concentrations higher than 30 vol%, iron could not be detected at the interface by optical microscopy. Thermo-gravimetric analysis shows that the rate of carbon take-up increases with increasing CO concentration reaching a maximum at about 60-75 vol%.The morphologies of graphite in the coke layer can be identified as three types: porous graphite clusters with embedded iron-containing particles, compact bulk graphite with a uniform thickness and a columnar layered structure, and filamentous carbon with iron-containing phases at the tip or along its length. For gas mixtures with low CO concentrations, e.g. 5 vol%, porous graphite clusters are the main form of carbon although filamentous carbon can be seen at the early stage of reaction. With increasing CO concentrations to, e.g. 30 vol%, a compact bulk graphite is formed on the top of the surface. Under this compact graphite, there is an inner layer of graphite which is the combination of porous graphite clusters and filaments. These two layers of graphite are clearly distinguishable when CO content reaches more than 75 vol%. In this case, the main form of graphite in the inner layer is filamentous carbon. The compact graphite layer suffers a serious deformation and forms many cracks because of the growth of catalytic filamentous carbon underneath. These filaments grow outside from compact graphite crevices and finally cover the whole surface. The higher the CO content in the gas, the more the tendency of filamentous carbon formation. The interplay between morphologies of carbon formation and metal dusting has been discussed.     

载气对CVI C/C材料密度和热解炭结构分布的影响

采用定向流动热梯度CVI工艺,以丙烯作炭源气,以针刺炭纤维整体毡作预制体分别研究了加氢气和氮气作载气对C/C复合材料密度和热解炭结构分布的影响。结果表明,载气对热梯度CVI C/C材料密度和热解炭结构沿径向分布的均匀性有重要影响。当其它工艺条件相同时,经过400 h的沉积,采用N2作载气时所得炭盘的平均体密度为1.54 g/cm3,炭盘密度沿径向分布的偏差Δρ为0.24 g/cm3,在炭盘的外侧易形成SL结构热解炭;而采用H2作载气时,可以得到平均体密度为1.67 g/cm3、热解炭结构分布高度均匀的全RL结构PyC基C/C复合材料,且炭盘密度沿径向分布的偏差Δρ仅为0.11 g/cm3,密度分布均匀性提高一倍以上。不管是采用N2还是H2作载气,炭盘的密度沿周向分布都十分均匀(Δρ≤0.02 g/cm3),且炭盘的较低密度部位均位于中间偏内侧。     

碳含量对Ti(CN)基金属陶瓷力学性能的影响

研究了Ti(CN)基金属陶瓷的碳含量对其物理力学性能的影响。结果表明 ,在一定范围内 ,随着碳含量的减少 ,Ti(CN)基金属陶瓷的矫顽磁力、钴磁和硬度降低 ;而抗弯强度则明显增高。     

碳钢在流动3%氯化钠溶液中的腐蚀机理的探讨

本文利用自行设计的模拟流动状态的装置,研究了碳钢在流动3%NaCl溶液中的腐蚀规律及施加阴极电流后对腐蚀的影响。结果表明:随着相对流速的增大,碳钢的腐蚀随之加剧,并发现存在一个临界相对流速值。当相对流速小于此值时,腐蚀主要受电化学因素影响。而相对流速大于此值时,流体力学因素开始明显起主导作用,并与电化学因素间的协同效应增强,导致腐蚀速度急剧上升。施加阴极电流后,不仅抑制了电化学因素引起的腐蚀,而且大幅度地削弱了电化学因素与流体力学因素间的协同效应,从而使腐蚀速度大大降低。     

Li2O-MgO-Al2O3-SiO2系高温低膨胀釉的制备及性能研究

以焦炉炉门堇青石衬砖的使用情况为依据，得出适合堇青石衬砖高温低膨胀釉的体系为Li2O-MgO-Al2O3-SiO2系。釉料在合理的化学组成范围内生成堇青石与口．锂辉石固溶体晶体。试验成功的研制出适用于堇青石衬砖的高温低膨胀釉，釉料在1350℃与堇青石砖共同烧成，釉层能均匀光滑的铺展在堇青石衬砖表面，它能在1200℃下使用而不融化，它的热膨胀系数为2．85×10^-4，在20℃～1000℃并且还有待于进一步降低。釉与堇青石衬砖热膨胀相匹配，因此釉层经五次热震（1100℃，水冷）后的没有裂纹出现。XRD物相分析得出釉有堇青石与口．锂辉石固溶体晶体相生成。釉能填充堇青石衬砖表面的气孔并以自身的高致密性防止了有害物质向砖内部渗透，起保护层作用。     

氯离子和电偶腐蚀对碳钢在热钾碱溶液中腐蚀的影响

研究了Cl-对碳钢和不锈钢在(K2CO3+KHCO3+ V2O5)溶液中腐蚀的影响,结果表明Cl-对阳极钝化曲线所示的腐蚀电位、钝化区间、过钝化电位和析氧过程无明显影响,未见试样有孔蚀的迹象.但随着Cl-离子浓度增大,其维钝电流密度也增大.90℃时,不锈钢-碳钢在此溶液中构成电偶腐蚀时,测得碳钢腐蚀速率为0.064 mm/a,比未成偶对时碳钢的腐蚀速率大一倍.90℃时,将已钝化的不锈钢-碳钢在(K2CO3+KHCO3)溶液中构成电偶腐蚀时,测得碳钢腐蚀速率为4.0 mm/a,比含有V2O5溶液中碳钢的腐蚀速率大64倍.     

我国化工石墨设备生产技术状况和进展综述

综述我国化工石墨设备“十一五”前后在生产技术方面的变化，并阐述同国外的质量比较，以及对石墨材料、合成树脂和产品价格等的差异误区和改进目标。