铝热还原法合成TiN/刚玉复合陶瓷的研究

以金属铝粉和钛白粉为原料,在流动氮气和匣钵埋碳保护气氛下采用铝热还原氮化法制备了TiN/刚玉复合陶瓷.采用XRD,SEM和TEM等分析手段,研究了铝热还原氮化法制备TiN/刚玉复合陶瓷在不同气氛和温度下的物相组成、晶格常数、显微结构.研究结果表明:在流动氮气和埋碳气氛下铝热还原法均可以制备TiN/刚玉复合陶瓷;处理温度和气氛明显影响着铝热反应的程度及产物的形貌,在埋碳条件下处理后的产物中TiN含量、晶粒大小、晶格常数明显低于流动氮气氛下处理产物中上述各项值.热力学计算发现埋碳条件下铝除参与铝热还原反应外,还与碳粉床中氧发生反应,导致参与铝热反应的金属铝不足,造成产物中有剩余的金红石存在.     

生物形态多孔氮化钛陶瓷的碳热氮化法制备

研究了以生物模板(木炭)浸渍TiO2溶胶,高温碳热-氮化制备TiN陶瓷的工艺过程.应用热力学原理计算了经溶胶浸渍后形成的TiO2/C复合体系的氮化条件,确定了N2,CO分压对氮化温度的影响.采用碳热氮化法,在高浓度的氮气压力下反应烧结制备了具有生物形貌的多孔TiN/C陶瓷.结果表明在1400℃,4 h,0.5 MPa氮气压力下,得到了具有立方晶体结构的TiN/C多孔陶瓷,并保留了木材模板的显微结构.     

生物形态多孔氮化钛陶瓷的碳热氮化法制备

研究了以生物模板(木炭)浸渍TiO2溶胶,高温碳热-氮化制备TiN陶瓷的工艺过程.应用热力学原理计算了经溶胶浸渍后形成的TiO2/C复合体系的氮化条件,确定了N2,CO分压对氮化温度的影响.采用碳热氮化法,在高浓度的氮气压力下反应烧结制备了具有生物形貌的多孔TiN/C陶瓷.结果表明:在1400℃,4 h,0.5 MPa氮气压力下,得到了具有立方晶体结构的TiN/C多孔陶瓷,并保留了木材模板的显微结构.     

铝碳复合还原氮化制备矾土基β-SiAlON

分别以复合还原剂铝碳,单一还原剂铝、碳还原氮化铝土矿(Al2O3含量为68%)(文中含量均为质量分数)制备β-SiAlON。利用XRD、SEM和EDS等检测手段和试样在1 100～1 550℃温度范围的质量变化率,研究了制备β-SiAlON的相变过程和铝碳复合还原剂对生成β-SiAlON的含量和显微结构的影响。结果表明:1 100℃时,铝粉氮化形成AlN,同时铝粉还原二氧化硅生成Si;1 200℃时,Si和氮气反应生成Si3N4;1 300～1 350℃,还原剂碳参与还原反应,β-SiAlON开始生成;1 400～1 550℃时,进入固溶阶段,β-SiAlON量增多,1 550℃时含量达到最高。与单一还原剂相比,铝碳复合还原剂制备的β-SiAlON的晶体截面形态呈长柱状,结晶发育较好。     

沉淀前驱物制备AIN陶瓷粉末

以硝酸铝和碳黑为原料，利用化学沉淀法制备出混合均匀的Al2O3＋C前驱物，并以该前驱物为原料采用碳热还原法制备了AIN粉末。研究了氮化反应温度、pH值、表面活性剂、溶液浓度、氮气流量和碳铝比等工艺参数对氮化反应的影响，得出的最佳工艺参数分别为：以0．4mol／L的硝酸铝溶液和比表面积为156m^2／g的碳黑为原料，控制原料中碳铝比为3：1，添加适量的硬脂酸（SA）和聚乙二醇（PEG）作为表面活性剂，控制沉淀过程中pH=9，通过共沉淀工艺得到分散性好、团聚程度小的前驱物，并将此前驱物在常压和氮气流量为5L／min的条件下于1550℃煅烧4h，最后将反应产物在650℃的空气中除碳4h，制备出氮含量为33．20％，氧含量为0．98％，比表面积为4．26m^2／g的AIN粉末。     

低Al2O3矾土碳热还原氮化合成复相Sialon的研究

利用低品位铝矾土经碳热还原氮化合成得到复相Sialon。采用XRD、SEM和EDS等研究了合成温度（分别为1300、1400、1500、1600℃），碳含量（分别为理论量、过量10％、过量50％和过量100％）对合成产物的影响。结果表明：以低品位铝矾土为原料，碳黑为还原剂，碳加入量为理论量，在0．9MPa流动氮气下经1600℃，3h碳热还原氮化反应合成出了α-Sialon和β-Sialon，其中α-Sialon晶体呈六方柱状结构。     

包覆型BN-AIN复合粉体研究

利用包覆法，首先通过将AIN粉体均匀分散到硼酸（H3BO3）和尿素（CO（NH2）2）的无水乙醇溶液中，制备出与硼酸和尿素均匀混合的AIN粉体。然后在氮气氛下，经过氮化处理来制备BN-AIN的复合粉体。DTA／TG分析显示，氮化反应从800℃开始，到1100℃时结束。XRD和TEM分析发现，复合粉体是由非晶态的BN均匀包覆AIN的复合颗粒组成。     

用耐火粘土废砖粉制备Al2O3／SiC复相陶瓷材料的研究

以耐火粘土废砖粉为原料，无烟煤为还原剂，研究了碳热还原反应制备Al2O3／SiC复相陶瓷材料的反应过程，探索了其工艺参数对其反应的影响。结果表明，在适当的碳和氧化硅摩尔比，不低于1600℃时可以合成Al2O3／SiC复相陶瓷。随着还原反应温度的升高，保温时间的延长，碳含量的适量增加，原料粒度越细，都可以有效的促进反应进行。催化剂的加入对碳热还原反应有一定的影响。SEM观察表明Al2O3／SiC复相陶瓷中，SiC交错分布在刚玉之间。     

原位直接氮化法制备片状AlN粉体

片状AlN粉体作为热界面材料的填料应用前景广阔，但制备工艺难度大、成本高限制了其实际应用。本文以球磨处理后得到的片状Al粉为铝源，在氮气气氛中通过原位直接氮化法成功制备出由等轴状微米颗粒结合而成的片状AlN粉体，并研究了球磨处理、氮化温度和升温速率对产物物相组成及显微形貌的影响。结果表明，球磨处理可增强Al粉的反应活性、提升氮化速率。升高氮化温度可提升Al粉的氮化率，但过高的氮化温度则会导致产物无法保持片状形貌；提高升温速率会增大等轴状微米颗粒的粒径。当氮化温度为640℃、升温速率为5℃/min时，制备的片状AlN粉体表面最为致密、平整，有望作为热界面材料的填料使用。     

含钛高炉渣合成（Ca，Mg）α′-Sialon-AIN-TiN粉末

在热力学分析的基础上，以含钛高炉渣为主要原料，采用碳热还原氮化法合成了(Ca，Mg)α′-Sialon-AIN-TiN粉。确定了合成过程的最佳工艺参数：反应温度1480℃，保温10h，配碳量为理论值的1．5倍，氮气流量400mL／min。采用X射线衍射仪和扫描电镜研究了合成产物的相组成和显微结构。结果表明：产物中除有主要物相α′-Sialon、AIN和TiN外，还有少量β-SiC，15R和β-CaSiO3等杂质相。其中，(Ca，Mg)α′-Sialon多以片状而AIN多以球形或短柱状形式存在。EDS分析结果表明，Ca^2 、Mg^2 都进入了α′-Sialon晶格中，但Ca^2 的固溶量远高于Mg^2 。     

Synthesis of Al2O3／WC powder by aluminothermic reduction and carbonization method

Al2O3/WC powder was synthesized by means of aluminothermic reduction-carbonization with metallic Al powder, yellow tungsten oxide and carbon black or graphite as raw materials under the protection of coke granules.The effects of Al2O3 content, temperature, C/WO3 molar ratio, and atmosphere on the synthesis of Al2O3/WC powder were studied. The results show that the relative content of WC and W2C is strongly influenced by the factors mentioned-above. Carbon black has higher reactivity than graphite. Al2O3-WC composite is easier to obtain under the protection of coke granules than under argon atmosphere. The CO in the coke layer can easily react witht ungsten to form WC and to transfer from W2C to WC.     

复相Al2O3/SiCw陶瓷与不锈钢钎焊接头的界面反应和反应产物

采用氩气保护下活性金属钎焊法对碳化硅晶须增韧氧化铝陶瓷（Al2O3/SiCw）与不锈钢（1Cr18Ni9Ti)进行了钎焊，所用钎料为Ag-Cu-Ti3活性钎料，通过X－射线衍射仪（XRD）对界面的反应产物进行了物相分析，并用能谱仪（EDAX）分析了界面元素组成，结果表明，钎焊接头界面的反应十分复杂，反应产物多种多样，主要有TiO,Ti2O,TiC,Fe2Ti4O,Ni3Ti,AlTi等物质，界面反应层按Al2O3 SiC/TiO AlTi TiC/TiO2 Fe2Ti4O/Ag-Cu的规律过渡。     

反烧结Si3N4复合陶瓷抗氧化性能研究

以TiSi2、SiC和Mo粉为原料通过反应烧结方法制备Si3N4基陶瓷,并测试其抗氧化性能.结果表明：Si3N4-TiN-SiC陶瓷的质量增量随着氧化时间的延长而增加,氧化质量增量随时间的变化基本服从抛物线规律,同时质量增量随着氧化温度的升高而增加.而Si3N4-TiN-MoSi2-SiC复合陶瓷质量增量在低温下随着时间延长而增加,在高温下质量增量随着时间延长而减少.XRD和SEM结果表明Si3N4-TiN-SiC陶瓷的氧化产物主要是TiO2、Si02和Si2N20,而Si3N4-TiN-MoSi2-SiC陶瓷则是Ti02、Si02、Si2N2O和Mo03.     

Effect of the aluminum content on the mechanochemical behavior in ternary system Al–B2O3–C

The effect of aluminum content on the mechanochemical behavior of ternary system Al–B₂O₃–C to fabricate Al₂O₃/B₄C composite was investigated. A mixture of boron oxide powders along with different amounts of aluminum and graphite was activated in a ball mill. The value of Al content varied from 2 mol to 7 mol compared to the stoichiometric mole ratios (4 mol). Thermodynamics evaluation indicates that the value of Al content in the mixture plays a key role and overall reaction enthalpy and adiabatic temperature altered by variation of aluminum and carbon content. Experimental findings revealed that at low aluminum content (2 mol Al), aluminothermic reaction proceeded in gradual mode and no carbothermal reduction took place. Increase in Al content up to 3 mol led to a change in the mode of aluminothermic reaction to MSR (mechanically induced self-propagating reaction) and gradual occurrence of carbothermic reaction. By increasing the amount of Al (10/3–4 mol Al), aluminothermic reaction provided sufficient heat for activating endothermic carbothermic reduction; hence, both reducing reactions happened simultaneously. Further increase in Al content (7 mol Al) led to gradual aluminothermic reaction and excess Al acted as inert matrix.     

Effect of carbon content on microstructure of in-situ Al_2O_(3p)-TiC_p/Al composites

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Study on the effect of laser post-treatment on the properties of nanostructured Al2O3-TiB2-TiN based coatings developed by combined SHS and laser surface alloying

A nanostructured, hard and wear resistant composite coating of Al2O3, TiB2 and TiN isformed on low carbon steel (AISI 1025) substrate by combined self-propagating high-temperaturesynthesis (SHS) and laser surface alloying (LSA). A precursor powder mixture of Al, TiO2 and hBNpreplaced on the substrate surface undergoes self-propagating high-temperature synthesis (SHS) atthe high temperatures induced by the incidence of laser. The products of SHS are subsequently laseralloyed onto the substrate to form the coating. The high power laser beam is again made to pass overthe coating with a view to remelt the coating top layer. This laser post-treatment causes distinct enhancements in microhardness and tribological performance by the modification of themicrostructure of top portion of the coating.     

Co-Al2O3金属陶瓷的制备与燃烧合成反应控制

应用燃烧合成法制备Co-Al2O3金属陶瓷,通过添加稀释剂Al2O3和反应性添加物TiO2控制燃烧合成反应,并探讨了其对金属陶瓷组织结构的影响。利用Al-Fe2O3助燃体系控制热爆反应的起始温度,使热爆反应在1050K左右进行,制备了Co-Al2O3金属陶瓷的中空件,并获得了金属相细小、均匀分布于陶瓷基体中的Co-Al2O3金属陶瓷。     

Ti-Al-TiO_2体系的热力学分析及合成反应过程研究

以Ti、Al和Ti02混合粉的原位反应制备Al203颗粒增强TiAl基复合材料.利用热力学机理分析了制备该种材料的可行性;用扫描电镜观察了合成产物的组织形态;借助差热变化曲线,对Ti-Al-Ti02体系的反应过程进行了初步研究.结果表明,Ti-Al-Ti02体系的反应能够原位生成Al203颗粒增强的TiAl基复合材料;Al203颗粒分布在基体晶界处,随其含量增大,基体晶粒逐渐细化;铝熔化后首先开始了TiAl3的生成反应,由于Ti02的稀释作用,使它的放热峰与Ti-Al体系的主放热峰相比有所滞后,紧接着发生了Al-Ti02的还原反应,由于其激活能低而速度较快,因此较早完成;若Al-Ti02的还原反应未进行彻底,部分TiAl3将分解以提供铝液;最后发生了TiAl3向TiAl和TiAl相转变的过程.     

Reaction procedure of a graphite fiber reinforced Ti-Al composite produced by squeeze casting-in situ reaction

The in situ reaction procedure and microstructure evolution of a graphite fiber reinforced Ti-Al composite (Grf/Ti-Al) was investigated, and the stability of TiAl3 at high temperature was discussed. As-cast material was prepared by pressing molten pure aluminum into a preform, which was composed of titanium particles and graphite fibers. The in situ reaction procedure of the as-cast material was investigated by differential scanning calorimetry (DSC), and phases in the products were detected by X-ray diffraction (XRD). Experimental results showed that TiAl3 was formed first. With an increase in temperature, TiC and Al4C3 were observed, but TiAl3 decreased. In the final product, Al2O3 and TiO2 were observed. It was considered that the previous forming TiAl3 decomposed, then TiC precipitated, and subsequently, oxidation resulted in the formation of Al2O3 and TiO2.     

INTERFACIAL REACTION BEHAVIOUR AND JOINT STRENGTH OF TiCp/Si3N4 COMPOSITE BONDED WITH Al FOIL

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