刚玉–Ti2O3共存物相在氧化气氛下的相变与形貌演变

刚玉-Ti₂O₃共存物相是通过调整低钛铁的冶炼工艺得到的一种冶金副产品，其中Al₂O₃和Ti₂O₃两相独立存在，可以作为耐火材料原料使用。通过热重–差热结合热力学分析得知原料中的Ti₂O₃在700℃左右开始氧化反应，Al₂O₃和TiO₂在1 263℃左右开始反应，将原料在不同温度空气气氛下保温3 h烧成，由XRD结合SEM结果可知在800℃左右Ti₂O₃完成氧化反应，在1 300℃受钛酸铝分解反应的影响，只有部分TiO₂和Al₂O₃在刚玉交界处反应生成片状Al₂Ti O₅。随着烧成温度升高至1 400℃和1 500℃，Al₂O₃和TiO₂     

Ti3AlC2在750℃下的氧化行为和腐蚀行为的研究

Ti₃AlC₂属于三元层状化合物MAX相，兼具金属的韧性和陶瓷的耐高温、耐氧化、耐腐蚀的综合性能，可用作高温结构材料。本工作研究了Ti₃AlC₂MAX相块材的抗高温氧化和耐热盐腐蚀性能。结果表明，750℃时，Ti₃AlC₂样品的氧化168 h,氧化产物主要是α-Al₂O₃, TiO₂-Rutile和TiO₂-Anatase,氧化增重为2.4 mg/cm²;在伴有NaCl和水的条件下腐蚀240 h,腐蚀产物主要是α-Al₂O₃, TiO₂-Rutile, TiO₂-Anatase和Na₂TiO₃腐蚀增重为4.4 mg/cm²。Ti₃AlC₂的氧化和腐蚀动力...     

低成本大比表面积γ-Al2O3的制备

以廉价无机铝盐硫酸铝为原料,氨水为沉淀剂,十二烷基硫酸钠为添加剂,采用简单沉淀法制备得到较大比表面积γ-Al₂O₃。通过N₂低温物理吸附-脱附、X射线衍射、红外光谱、热重、元素分析、扫描及透射电镜等,研究制备过程中沉淀温度、溶液pH值和添加剂用量对产物γ-Al₂O₃及其前驱体的晶相结构、形貌织构等性质的影响。结果表明,在沉淀温度75 ℃、硫酸铝浓度0.25 mol·L^-1、溶液pH=9.0、老化时间12 h和n(十二烷基硫酸钠)∶n[Al₂(SO₄)₃]=0.375∶1条件下,所得前驱体(拟薄水铝石)经600 ℃焙烧后,可获得大比表面积(416.65 m²·g^-1)γ-Al₂O₃,并且样品中因十二烷基硫酸钠添加,引入的S及Na等杂质含量极少。     

磷石膏快速干法稳定化的矿物特征研究

新鲜磷石膏中的主要污染物种类为氟化物和磷化物,添加石灰能有效降低氟和磷的浸出水平,并且添加状态和比例对稳定化效果影响较大。通过添加不同石灰比例来稳定磷石膏的处理方式,研究其污染物的浸出水平,并采用扫描电镜及能谱对其进行表征。研究发现石灰与磷石膏拌混比例是污染物浸出水平的重要影响因素,在m（生石灰）∶m（新鲜磷石膏）为1∶50~1∶100时稳定化效果最好。由扫描电镜和能谱表征发现新鲜磷石膏为片层状结构堆叠,随着石灰添加量增多,表面微观结构也相应增多。在m（生石灰）∶m（新鲜磷石膏）为1∶100时,磷石膏的片层状结构表面会形成棒状结构,棒状间隙存在微球状颗粒。根据表征结果推测片层状结构除CaSO₄外,还含有一定量的Ca₃（PO₄）₂,棒状结构为Al₂O₃和AlPO₄,微球颗粒为CaF₂。在新鲜磷石膏表面形成的这类微观结构,使得含氟和磷的污染物稳定化从而降低了浸出水平。     

TiO2-Al2O3复合粉体的制备及光催化性能

Al₂O₃陶瓷膜在过滤染料废水过程中容易被染料大分子堵塞,导致Al₂O₃陶瓷膜水通量下降。以钛酸丁酯、异丙醇铝为前驱体,采用溶胶-凝胶法制备Ti(OH)₄-AlOOH复合溶胶,经450 ℃烧成获得TiO₂-Al₂O₃复合粉体。以SEM、纳米粒度/电位仪作为主要表征手段,研究了不同Ti(OH)₄和AlOOH摩尔比对复合溶胶粒径分布的影响,进而探究TiO₂-Al₂O₃复合粉体的光催化性能。结果表明,Ti(OH)₄和AlOOH摩尔比为0~0.4时,随着Ti(OH)₄和AlOOH摩尔比的增大,胶粒的平均粒径从67.5 nm减小到34.0 nm,Ti(OH)₄-AlOOH复合溶胶的电位从43 mV升高至53 mV。当Ti(OH)₄和AlOOH摩尔比为0.4时,复合粉体对结晶紫的去除率高达79.3%,反应速率常数增大到了0.018 min^-1。TiO₂-Al₂O₃复合粉体制备的陶瓷膜能有效降解表面沉积的大分子,解决了陶瓷膜堵塞的问题。     

片状氧化铝的熔盐法制备关键参数

高径厚比片状Al₂O₃在高端珠光颜料片状基材应用方面潜力巨大,但是其制备技术为国外所垄断,开发片状Al₂O₃商用生产技术迫在眉睫。熔盐法是制备片状Al₂O₃的理想方法,目前尚无系统研究熔盐法关键工艺参数对片状Al₂O₃影响规律的报道。本文通过片状Al₂O₃的形成机理,系统研究了TiO₂添加剂、Na₃P₃O₉添加剂、煅烧温度和熔盐用量4种关键工艺参数对制备片状Al₂O₃的影响规律,并进一步优化制备工艺,提出最优工艺参数。利用扫描电子显微镜和X射线衍射仪分析Al₂O₃的形貌、粒度和物相。结果表明：采用熔融盐（Na₂SO₄-K₂SO₄）添加NaCO₃为凝胶剂,再加入质量分数分别为3.0%的Na₃P₃O₉和2.0%的TiO₂为添加剂,在煅烧温度为1200℃、保温时间5h时,所制得的六角片状Al₂O₃粉体具有优异的品质,其平均粒径约为4μm,厚度为50～200nm,径厚比为20～80。     

机械和超声波分散对纳米Al2O3颗粒在聚酯树脂中的分散及涂层性能的影响

将纳米Al₂O₃颗粒分别通过机械和超声波分散工艺分散到聚酯树脂中，研究了机械分散转速和分散方式对纳米Al₂O₃/聚酯树脂复合涂层性能及纳米Al₂O₃在聚酯树脂中的分散性的影响；通过研究复合涂层的耐盐雾性、硬度、耐磨性等，确定了最佳分散工艺。结果表明：纳米Al₂O₃颗粒可在1 500 r/min的机械分散下形成均匀分散体系，再用超声波分散可进一步提升分散效果和涂料的稳定性，有效减少纳米Al₂O₃在水性聚酯树脂中的团聚，在提高所得复合涂层硬度、耐磨性的同时，增强其耐腐蚀性。     

纳米Al2O3/SBR复合改性沥青高温性能研究

本文为研究纳米Al₂O₃的掺入对纳米Al₂O₃/SBR(丁苯橡胶)复合改性沥青高温性能的作用，通过针入度、延度、软化点三大基本指标与动态剪切流变(DSR)试验进行分析，试验结果表明：纳米Al₂O₃的掺入改变了沥青的三大指标，DSR试验中，相同高温下纳米Al₂O₃/SBR复合改性沥青较基质沥青及SBR改性沥青的车辙因子有明显的提升。所以，通过掺入纳米Al₂O₃改善沥青高温性能是可行的。     

铌掺杂钛酸钡的制备及性能研究

采用熔盐法制备掺杂Nb₂O₅的Ba Ti O₃粉体及陶瓷并对产物进行表征与性能分析,探究了不同烧结温度、不同熔盐比、不同掺杂(Nb₂O₅)物质的量下掺杂Nb₂O₅的Ba Ti O₃粉体,利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、拉曼光谱(Raman)等设备分析掺杂Nb₂O₅的Ba Ti O₃粉体相结构、微观相貌及拉曼分析,并探究掺杂Nb₂O₅对于Ba Ti O₃陶瓷铁电性及介电性的影响。结果表明,当烧结温度为1000℃、熔盐比为n_{Na Cl}∶n_KCl=5∶5、掺杂Nb₂O₅物质的量为0.10mol时,制备出的Ba Ti O₃陶瓷性能最优,此时,陶瓷样品的铁电性能达...     

聚吡咯修饰氧化铁纳米片改善锂硫电池性能

采用酸刻蚀诱导的原位生长法在α-Fe₂O₃纳米片表面修饰聚吡咯,其中对甲苯磺酸起到刻蚀与掺杂的作用,Fe₂O₃纳米片表面被刻蚀出的Fe³⁺作为氧化剂,使得吡咯在Fe₂O₃纳米片表面聚合生长,对甲苯磺酸根作为对阴离子掺杂于聚吡咯分子结构中,得到Fe₂O₃@PPy复合纳米片。通过调节刻蚀环境与Fe₂O₃纳米片的投料量控制聚吡咯的修饰量,制得系列Fe₂O₃@PPy复合纳米片。当对甲苯磺酸和Fe₂O₃摩尔比为12:1时,Fe₂O₃@PPy复合纳米片获得优异的电化学性能。1 C下的初始容量为468.7 mA·h·g^-1,循环500次后仍保持414.5 mA·h·g^-1的容量,容量保持率...     

Synthesis of single-phase Ti3SiC2 powder

In this study, free 2Ti/2Si/3TiC powder mixture was heated at high temperatures in vacuum, in order to reveal the possibility for the synthesis of high Ti₃SiC₂ content powder. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for the evaluation of phase identities and the morphology of the powder after different treatments. Results showed that almost single phase Ti₃SiC₂ powder (99.3 wt.%) can be synthesized by heat treatment with free 2Ti/2Si/3TiC powders in vacuum at 1210°C for about 3 h. The nucleation and growth of Ti₃SiC₂ within TiC particles was observed. The typical appearance of the formed Ti₃SiC₂ is equiaxed with particle size of 2–4 μm. Effects of temperature and heating time on the morphology and the particle sizes of the synthesized Ti₃SiC₂ powders are not obvious.     

Effect of Al addition on the synthesis of Ti3SiC2 bulk material by pulse discharge sintering process

Ti₃SiC₂ bulk materials were synthesized from the starting powders of 1Ti/1Si/2TiC–xAl and 3Ti/1SiC/1C–xAl (molar ratios, x ranges from 0.05 to 0.15) at temperatures between 1100 and 1400 °C for 15 min by pulse discharge sintering technique. X-ray diffraction and scanning electron microscopy were used to characterize the synthesized materials. It was found that the addition of Al decreases the content of TiC in the sintered samples and expands the optimal temperature range for the synthesis of Ti₃SiC₂ bulk materials. By addition of Al, Ti₃SiC₂ bulk materials of high phase-purity have been synthesized at 1100 and 1200 °C from 1Ti/1Si/2TiC and 3Ti/1SiC/1C starting powders, respectively.     

Application of pulse discharge sintering (PDS) technique to rapid synthesis of Ti3SiC2 from Ti/Si/C powders

To synthesize Ti₃SiC₂ samples, pulse discharge sintering (PDS) technique was utilized to sinter elemental powders of Ti/Si/C with stoichiometric and off-stoichiometric ratios in a temperature range of 1200–1500 °C. The results showed that high purity Ti₃SiC₂ could not be obtained from the Ti/Si/C powder with molar ratio of 3:1:2, and Ti₃SiC₂ preferred to form at relatively low sintering temperature for a short time. When 5Ti/2Si/3C and 3Ti/1.5Si/2C powders were sintered for 15 min, the TiC content was respectively decreased to 6.4 and 10 wt.% at 1250–1300 °C. The corresponding relative density of the samples sintered from 5Ti/2Si/3C powder was calculated to be as high as 99% at the temperature above 1300 °C. It is suggested that low-temperature rapid synthesis of Ti₃SiC₂ would be possible through the PDS technique, provided that the composition of the starting powders should be adjusted to be off-stoichiometric ratio from 3:1:2.     

Surface strengthening of Ti3SiC2 through magnetron sputtering Cu and subsequent annealing

Magnetron sputtering deposition Cu and subsequent annealing in the temperature range of 900–1100 °C for 30–60 min were conducted with the motivation to modify the surface hardness of Ti₃SiC₂. Owing to the formation of TiC following the reaction Ti₃SiC₂ + 3Cu → 3TiC_0.67 + Cu₃Si, the surface hardness was enhanced from 5.08 GPa to a maximum 9.65 GPa. In addition, the surface hardness was dependent on the relative amount of TiC, which was related to Cu film thickness, heat treatment temperatures and durations of annealing. Furthermore, after annealing at 1000 °C for 30 min the Cu-coated Ti₃SiC₂ has lower wear rate and lower COF at the running-in stage compared with Ti₃SiC₂ substrate. The reaction was triggered by the inward diffusion of Cu along the grain boundaries and defects of Ti₃SiC₂. At low temperature and short annealing time, i.e. 900 or 1000 °C for 30 min, Cu diffused inward Ti₃SiC₂ and accumulated at the trigonal junctions first. At higher temperature of 1100 °C or prolonging the annealing time to 60 min, considerable amount of Cu diffused to Ti₃SiC₂ and filled up the grain boundaries leaving a mesh structure.     

Hot corrosion and protection of Ti2AlC against Na2SO4 salt in air

The hot corrosion behavior of Na₂SO₄-coated Ti₂AlC was investigated by means of thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy/energy dispersive spectroscopy. This carbide displays good hot corrosion resistance below the melting point of Na₂SO₄ while the corrosion attacks become virulent when the salt is molten. A protectively continuous Al₂O₃ layer forms and imparts good corrosion resistance, and consequently, the corrosion kinetics is generally parabolic at 850 °C. However, porous oxide scales fail to protect the Ti₂AlC substrate at 900 and 1000 °C. The segregation of sulfur at the corrosion scale/substrate interface accelerates the corrosion of Ti₂AlC. Furthermore, a convenient and efficient pre-oxidation method is proposed to improve the high-temperature hot corrosion resistance of Ti₂AlC. An Al₂O₃ scale formed during pre-oxidation treatment can remarkably restrain the infiltration of the molten salt into the substrate and prevent the substrate from severe corrosion attacks.     

一步法合成二维Ti3C2及其电化学性能研究

二维过渡金属碳/氮化物（MXene）是一种新型二维材料,可通过从MAX相前体中选择性刻蚀 A 原子层获得。在传统制备MXene的方法中,常用的刻蚀剂是氢氟酸。然而高浓度氢氟酸的使用,不可避免会带来安全问题,甚至破坏MXene的晶体结构,从而限制本征物理化学性能。从典型的碳化物前体Ti₃AlC₂出发,使用 NH₄BF₄作为刻蚀剂,有效降低体系中酸的使用量;在反应过程中,刻蚀 A 层的同时,\mathrm{N}{\mathrm{H}}_{\mathrm{4}}^{+}进入堆垛层间,扩大层间距,弱化层间作用力。因此,仅通过简单手摇就可以实现高效剥离,得到具有完整晶体结构的二维Ti₃C₂。进一步测试了Ti₃C₂的电化学性能,结果显示,所得的Ti₃C₂具有优异的性能（扫描速率为5 mV?s^-1时为503 F?g^-1）和循环稳定性（在5 A?g^-1下循环10⁴次后电容保持率为95.8%）。本文为Ti₃C₂纳米片的合成及应用提供了新的思路。     

静态条件下合成纳米片层ZSM-5分子筛

采用具有双功能导向作用的长碳链双季铵盐作为模板剂,原料配比为n(Na_2O)∶n(Al_2O_3)∶n(SiO_2)∶n(C_(22-6)-6Br_2)∶n(H_2SO_4)∶n(H_2O)=30∶1∶100∶10∶18∶4 000,静态条件下合成有序纳米片层ZSM-5分子筛,并采用XRD、N2吸附-脱附、SEM和TEM等对其进行表征。研究部分晶化条件对合成过程的影响。结果表明,增大填充度至50%,可以提高晶化压强,从而提高分子筛结晶度;随着凝胶碱度的增加,纳米片层分子筛结晶度先增大后降低,多片层有序性也发生同样变化;晶化时间对合成过程的前期影响较大,晶化时间6天,分子筛达到较高结晶度,样品形貌均一,介孔孔径分布集中。     

电泳沉积法制备高能量密度的非对称平面微型超级电容器

首先采用光刻、蒸镀金的方法制备叉指电极,随后把合成的具有赝电容特性的二维MnO2和Ti3C2纳米片分别电泳沉积到叉指电极上,构建了非对称平面超级电容器.其中MnO2为正极,Ti3C2为负极,滴涂凝胶为电解质,并利用透明的聚二甲基硅氧烷薄膜封装成器件.通过能量色散X射线光谱(EDS)、傅里叶变换红外光谱(FT-IR)、扫...     

Fe掺杂SUZ-4催化剂制备及其SCR反应活性

在添加晶种和有机模板剂条件下,采用两步溶胶-凝胶法,酸环境下共水解正硅酸乙酯和金属盐,合成得到骨架Fe-SUZ-4分子筛。通过紫外可见漫反射表征证明Fe成功嵌入分子筛的四配位骨架上。Fe-SUZ-4分子筛催化剂在NH_3-SCR脱硝反应中表现出优异的催化性能,其催化活性显著高于离子交换法和浸渍法制备的含Fe分子筛催化剂。结果表明,凝胶配比为n(TEAOH)∶n(KOH)∶n(Al_2O_3)∶n(SiO_2)∶n(H2O)=1.0∶10∶1∶22.5∶500,晶种质量分数为1%,n(Fe)∶n(Si)=0.005~0.02,随着Fe含量的增加,Fe-SUZ-4分子筛晶化时间略有延长,且结晶度略降。NH_3-SCR脱硝反应中,Fe-SUZ-4分子筛催化剂最适宜的金属含量为n(Fe)∶n(Si)=物质的量比0.01,反应温度约350℃时,NO转化率达到100%。而通过离子交换法和浸渍法合成得到的含Fe分子筛催化剂用于SCR反应,NO转化率达到100%时,反应温度均有提高。     

Microstructural Evolution of Titanium Carbide–Chromium Carbide (TiC–Cr3C2) Composites Produced via Combustion Synthesis

A microstructural analysis of compounds produced by combustion synthesis coupled with hot pressing, for reactions between titanium, chromium, and carbon, was conducted. The reactions were aimed to produce composites of Cr₃C₂ and TiC at three different volume fractions of each carbide (25/75, 50/50, and 75/25). Large amounts of chromium and carbon were found to be in solution in the B1 rock-salt structure of TiC. The materials with 25 and 50 vol% of Cr₃C₂ consisted of 100% (Ti,Cr)C_ss solid solution, while the composition with 75 vol% Cr₃C₂ was formed by Cr₃C₂+ (Ti,Cr)C_ss. Some precipitation of Cr₃C₂ was achieved by annealing, but a minimum of 20 wt% was always in solution. The 50 vol% Cr₃C₂–50 vol% TiC composition was the most affected by the heat treatments. Discontinuous and general precipitation were observed, depending on the annealing conditions. A TTT-type diagram was plotted for this material.