利用融盐热析出反应进行陶瓷材料表面改性的研究

本文系统地研究了利用融盐热析出反应进行陶瓷材料表面改性及制备复合材料的机理和工艺。利用热析出反应在氮化硅、氮化铝表面上成功的制备了２￣８μｍ厚度的钛、锆金属膜、该金属膜与陶瓷基体结合牢固。与金属有良好的浸润性。本文还系统的研究了反应温度，反应物浓度、反应物浓度、反应时间对陶瓷表面金属膜厚度的影响，研究了反应动力学机理，及表面层的组成。     

利用热歧化反应进行氮化铝陶瓷表面钛金属化工艺及正交实验研究

利用熔盐热岐化反应法成功地进行了氮化铝陶瓷表面钛金属化。利用正交实验法就反应温度、反应时间、K2TiF6浓度3个因素对制备工艺进行探讨，研究各工艺参数对金属化膜厚度的影响。利用XRD、SEM对金属化膜的组成和陶瓷与金属化膜之间的界面进行了分析和观察，并对利用该法进行氮化铝陶瓷表面金属化的反应机理进行了初步探讨。     

铝锂合金微弧氧化陶瓷膜层特性的研究

采用先恒流、后恒压的微弧氧化方法,在铝锂合金(添加微量稀土元素Ce)表面制备陶瓷化膜层.研究了氧化时间和脉冲频率对膜层生长过程和表面形貌的影响.结果表明:膜层厚度随着反应时间的延长而增加,在更高频率的高能脉冲作用下(＞600 Hz)生长速率更快;膜层表面多孔、起伏不平,延长反应时间或提高脉冲频率会导致烧蚀留下的坑洞变大,表面粗糙度亦随之增大;膜层与基体结合良好,由内部致密层和外部疏松层组成,总厚度可达50 μm;EDS分析表明,膜层由Al、O、Si构成,Si元素的摄入认为是NaOH-Na2SiO3电解液体系中的SiO32-参与反应进入膜层.     

Si3N4陶瓷表面镀锆的融盐热析出反应研究

研究了Si3N4陶瓷表面镀锆的融盐热析出反应,以X射线衍射仪分析了镀膜物相,以电镜(SEM)对镀件进行了显微观察.结果表明:(1)镀膜的单位面积沉积量随反应温度的升高以及反应时间的延长而增加;镀膜的单位面积沉积速率随反应温度的升高而增加,随反应时间的延长而减小;单位面积镀膜增重随K2ZrF6初始浓度的逐渐增大,先呈上升趋势,达到最大值后又逐渐下降,K2ZrF6初始质量分数为60%时,单位面积镀膜增重最大;(2)镀膜物相为ZrN,Zr5Si3,Zr3O;(3)镀膜表面光滑,呈银白色金属光泽;膜层与Si3N4陶瓷基体结合紧密;镀膜为层状结构,界面结构为Si3N4/ZrN/ Zr5Si3/Zr3O;Zr5Si3晶粒粗大,ZrN晶粒细小,Zr3O呈不均匀地附着在Zr5Si3的表面;(4)单位面积增重(△W/△S)与 t1/2呈良好的直线关系;(5)反应活化能约为126kJ/mol.     

2090铝-锂合金微弧氧化陶瓷膜层特性的研究

在NaOH-Na2SiO3溶液中采用先恒流后恒压的微弧氧化工艺,可在2090A1-Li合金表面制备陶瓷化膜层.研究了微孤氧化反应时间和微弧氧化电源脉冲频率对陶瓷膜层生长过程和膜层形貌的影响.研究结果表明:氧化膜层的厚度随着反应时间的延长而增加,在更高频率电脉冲作用下(600H2),膜层的生长速率更快,但是膜层表面烧蚀坑大,表面粗糙,陶瓷膜与基体结合良好.膜层由内部致密层和外部疏松层组成.对膜层的元素分析结果表明:外层由Si、Al、0构成,而内层Si含量减少.     

添加离子强度对LBL聚电解质多层膜组装的影响

应用层层自组装技术(LBL)构筑聚电解质多层膜的过程中,组装溶液的离子强度对组装过程有特殊影响。采用紫外分光光度计与椭偏仪同时监测聚电解质沉积时间,聚阳离子(PDDA)浓度,特别是添加氯化钠(NaCl)对聚电解质成膜的影响。聚电解质分别沉积在石英基底和硅基底上,聚电解质膜厚度与聚电解质层数呈现良好的线性关系;随着聚电解质沉积时间的增加,聚电解质膜厚度逐渐增加,沉积时间为10min时聚电解质膜厚度最大;聚电解质膜的厚度随着PDDA浓度的增加呈现增长趋势;聚电解质溶液中加入NaCl,组装层数不大于10层时,聚电解质膜厚度随着NaCl浓度的增加而呈现线性增长。     

化学镀法制备钯膜工艺

以多孔Al2O3陶瓷管为载体,采用化学镀法制备了钯膜。考察了化学镀温度及载体孔径对制备钯膜的影响,并利用扫描电镜对钯膜形貌结构进行了表征。研究表明,化学镀15min,钯沉积速率较快;反应时间延长至120min,钯沉积量增加,但是沉积速率降低。随着化学镀温度的升高,钯沉积量增加;但是温度过高,会导致钯利用率降低;温度为318K,化学镀钯膜较适宜。在孔径为0.2μm的Al2O3陶瓷管表面制备的钯膜平整、致密,其二次镀钯膜N2渗透速率为1.7×10-9mol/(m2·s·Pa)。     

邻苯二酚和KH560共沉积用于PTFE平板膜的亲水改性研究

采用邻苯二酚(CA)和γ-缩水甘油醚氧丙基三甲氧基硅烷(KH560)共沉积的方法对聚四氟乙烯(PTFE)平板膜进行亲水改性,通过SEM、ATR-FTIR和XPS对平板膜表面进行了表征,并对反应条件进行了优化,同时考察了膜的抗污染和耐水洗性能。结果表明,发现共沉积改性后的PTFE膜纤维变粗,表面出现了新的元素O和Si;随着KH560含量的增加,交联速度加快、亲水层变厚、膜表面的接触角减小,纯水通量先增加后减小;适当增加反应时间和升高温度能使反应更为充分;当KH560的质量浓度为2 g/L,反应时间为6 h、温度为35℃时,膜的性能最优。改性PTFE平板膜具有良好的抗蛋白质吸附能力,亲水层稳定性。     

纳米陶瓷铝合金硼酸-硫酸阳极氧化工艺性能的研究

本次通过硼酸-硫酸阳极氧化工艺在纳米陶瓷铝合金表面制备氧化膜层,结果表明：经过硼酸-硫酸阳极氧化后,纳米陶瓷铝合金基体表面形成了一层连续且耐蚀的氧化膜,厚度1.51μm,氧化膜层经过336 h的盐雾试验后,腐蚀点点数小于5个,阳极氧化后表面亲水性变好,氧化膜层与水性底漆具有良好的结合力,油漆附着力测试达到合格。     

交流阻抗谱研究钙磷陶瓷电沉积层的结构

用交流阻抗技术研究了不同电沉积时间的钙磷陶瓷沉积层。结果表明，沉积时间不同的陶瓷沉积层的交流阻抗谱存在显著的差别。采用双层结构物理模型，对不同沉积时间陶瓷沉积层的交流阻抗谱进行计算机拟合，得到的等效电路各元件拟合值显示：电极表面钙磷陶瓷为内密外疏型梯度沉积层。在陶瓷电沉积过程中，钙磷晶粒同时沉积于距电极表面不同距离的部位，沉积层厚度增加的同时内层密度也在逐渐增加，整个 只层的梯度结构处于动态变化之中。     

Ultrathin GaN film and AlGaN/GaN heterostructure grown on thick AlN buffer by MOCVD

High-quality AlGaN/GaN/AlN heterostructures with thin GaN channel and thick AlN buffer layer were grown by metal organic chemical vapor deposition (MOCVD) on SiC substrate. By analyzing growth modes of GaN films on AlN buffer layers with different thicknesses, it is revealed that film-forming point of GaN grown on AlN buffer increases with the increase in AlN buffer thickness. Accordingly, new growth model of GaN on AlN buffer was proposed, which shows that there is an optimal matching value between Ga source flow rate and AlN thickness when GaN is grown on AlN buffer of different thicknesses. Under optimal conditions, AlGaN/GaN/AlN heterostructures with 120 nm thin GaN channel layer and thick AlN buffer show excellent carrier-limited domain, high crystalline quality, and good transport properties. Results in this work would be useful for preparing high-quality heterostructures on AlN buffer and high electron mobility transistor (HEMT) devices. Moreover, these findings can also be applied to the growth of other hyperfine structures (quantum wells, superlattices, and digital alloys) in the future.     

Interfacial Reaction between Titanium Thin Films and Aluminum Nitride Substrates

Interdiffusion and reaction at the interface between titanium thin films and AlN have been studied by using Rutherford backscattering spectrometry and transmission electron microscopy. Ti₂AlN is formed as a result of reaction with titanium and AlN at temperatures of 800°-950°C. The activation energy for Ti₂AlN formation in the temperature range of 800°-850°C is 224 kJ/mol, which is similar to that of nitrogen diffusion in titanium. Therefore, the formation of Ti₂AlN is believed to be controlled by the diffusion of nitrogen in titanium.     

Preparation of a titanium carbide coating on carbon fibre using a molten salt method

A method for preparing protective titanium carbide (TiC) coatings on carbon fibres has been developed using a molten salt synthesis method. The TiC coatings were formed on the surface of carbon fibres in a reaction medium consisting of Ti powder in a mixture of molten LiCl-KCl-KF salts under an argon atmosphere at 900 and 950 °C. The structure and morphology of the TiC coatings were characterized by XRD, SEM and energy dispersive X-ray (EDX) analyses. The coatings consisted of homogeneous single phase cubic TiC with thicknesses in the range of 60-800 nm. Variation of the synthesis time and reaction mixture was found to significantly affect the thickness and integrity of the TiC coating although variation of the reaction temperature had little effect. The coating thickness was closely related to the composition of the molten salts and to the molar ratio between the carbon fibre and titanium.     

Resistive switching characteristics of sputtered AlN thin films

AlN thin films were deposited on Pt/Ti/SiO₂/Si substrates using a radio-frequency magnetron sputtering technique. The effect on the switch current–voltage characteristics of four different materials in the electrode fabricated on top of the AlN film was investigated. The deposition time and nitrogen content in the sputtering atmosphere were changed to adjust the thickness and composition of the AlN thin films, respectively. The influence of film thickness and content on the resistive switching behavior was discussed. The possible mechanism of resistive switching was examined via analyses of the electrical resistive switching characteristics, forming voltage, and on/off current ratio.     

Using Simultaneous Deposition and Rapid Growth to Produce Nanostructured Composite Films of AIN/TiN by Chemical Vapor Deposition

Brittleness has been the major obstacle in using ceramics. Previous research has shown, however, that ceramic materials that have small grain size show plasticity. We therefore propose two methods to produce nanostructured ceramic films by chemical vapor deposition (CVD): (1) high-speed deposition and (2) simultaneous deposition of insoluble materials (contained in a mixture of insoluble solids). These methods were successfully applied to aluminum nitride/ titanium nitride (AlN/TiN) films produced by CVD. The AlN/TiN nanostructured composite films were synthesized by atmospheric-pressure CVD (APCVD), using aluminum chloride (AlC1₃), titanium chloride (TiCl₄), and ammonia (NH₃) as reactant gases at temperatures ranging from 923 to 1123 K in a horizontal tubular reactor. For the highspeed deposition strategy, we obtained growth rates as high as 1.2 mm/h. Using either method, we were able to attain AlN/TiN composite films that had a grain size of 8 nm (AlN crystals) and 6 nm (TIN crystals), showing that these methods are effective in producing nanostructured composite films by CVD. Measurements of the fracture toughness of the prepared materials indicated that these strategies can be used to improve the ductility of ceramics.     

熔盐高效分解含钛高炉渣制备纳米二氧化钛

采用熔盐法对含钛高炉渣进行高效分解并提取含钛组分,利用含钛滤液为原料制备了纳米二氧化钛粉体。对熔盐分解含钛高炉渣进行了热力学分析,并研究了碱渣比、熔盐反应温度及熔盐反应时间对钛组分浸出率的影响和pH及水解温度对二氧化钛产品纯度的影响。实验结果表明高炉钛渣在氢氧化钠熔盐中反应生成钛酸钠在热力学上是可行的。确定了最佳的碱渣比为3:1,最佳熔盐反应温度为500℃,最佳反应时间为3 h,在此条件下钛元素的浸出率为99.8%。得出较佳的水解pH范围为0.1～0.2,最佳水解温度为100℃。实验中制备的纳米二氧化钛粒子球形度好,粒度大小均匀且分散性好,颗粒直径为100 nm左右。     

Nucleation and growth behavior of aluminum nitride film using thermal atomic layer deposition

Aluminum nitride (AlN) film possesses wide band gap energy (~6.2 eV) and a high dielectric constant (~9.2), and is resilient to thermal and chemical stimuli. It also exhibits several functionalities, such as piezoelectricity and pyroelectricity. Therefore, AlN film has been used for electronic and optoelectronic devices and micro-electromechanical systems (MEMSs). Among the various methods of AlN thin film growth, atomic layer deposition (ALD) can control film thickness at the nanoscale. Uniform and conformal film growth is possible at temperatures lower than that of chemical vapor deposition or molecular beam epitaxy. Because the ALD process relies on surface chemical reactions, it shows substrate dependency. To control film uniformity from the beginning, an understanding of nucleation and growth behavior on the substrate is necessary. Therefore, the nature of nucleation and growth behaviors on different substrates is investigated. In this study, AlN films are grown on bare Si and TiN substrates at 295–342 °C by thermal ALD using trimethyl aluminum (TMA) and ammonia. Facile nucleation and linear growth on the TiN substrate, and substrate-inhibited nucleation on the Si substrate, are observed. NH₃ pretreatment may enhance the growth rate at the nucleation stage. Therefore, the dissociation of NH₃ on the substrate is crucial to making uniform nuclei for the subsequent growth of AlN film.     

The electro-deoxidation of porous titanium dioxide precursors in molten calcium chloride under cathodic potential control

A study on the electro-deoxidation of porous titanium dioxide precursors in molten calcium chloride is reported. Experiments were performed with a three-terminal electrochemical cell, comprising a molten salt electrolyte of calcium chloride with additions of calcium oxide, a cathode of compact titanium dioxide with a significant degree of open porosity, as well as a graphite anode and a graphite pseudo-reference electrode. Reductions were carried out under cathodic potential control and at different applied potentials. The results reveal that the formation of titanium metal occurs at electrode potentials significantly more positive than that of calcium deposition, whilst the realisation of very low residual oxygen contents requires potentials around that of calcium deposition. It is demonstrated that oxygen contents in the titanium metal prepared of below 5000 ppm by mass may be achieved reproducibly within processing times of 16 h and at current efficiencies between 10 and 40%. The kinetic pathway is investigated, by analysing the compositions of samples prepared at different cathode potentials, and compared against the results from foregoing studies. It is found that the presence of calcium oxide in the calcium chloride accelerates the overall rate of electro-deoxidation, and that the temporary occurrence in the cathode of the calcium-containing compounds calcium titanate, CaTiO₃, and calcium titanite, CaTi₂O₄, are inherent features of the reaction path. The overpotential at the anode is shown to be of significant magnitude.     

介质阻挡放电常压低温等离子体转化甲烷制C2及高碳烃的研究

对介质阻挡放电(DBD)反应器用于甲烷常压低温等离子体转化过程,分别就停留时间、输入功率、内电极材料及温度、介质厚度等对反应的影响进行了研究。实验结果表明,甲烷转化率随停留时间、输入功率的增加而增加,但增加的幅度逐渐减小。内电极材料对反应积炭有很大的影响。紫铜和紫铜(镀银)材料能够有效地抑制积炭的产生,从而可以增加反应寿命,还对甲烷转化率有很大的影响。较低的内电极温度可以抑制积炭,但是甲烷转化率有所降低,同时液态高碳烃选择性增加。在甲烷流量较低时介质厚度对反应的影响很小,但随着甲烷流量的提高会逐渐增大,并且介质厚度越小,甲烷转化率越高。