45（Ti＋C）＋55Fe（wt－％）的自蔓延燃烧反应过程

采用强制冷却方法使成分为４５（Ｔｉ＋Ｃ）＋５５Ｆｅ（ｗｔ－％）的混合粉压坯在燃烧合成时自行熄灭，得到了保留组织转变过程的产物。对其进行了Ｘ射线衍射分析和扫描电镜观察，计算了燃烧绝热温度Ｔ_（ａｄ），测定了实际燃烧温度Ｔ_ｃ和燃烧波温度轮廓。结果表明，燃烧是以固态反应为主的；固态反应引起了Ｔｉ粉和Ｆｅ粉内燃烧反应的非同步性，ＴｉＣ粒子分别在原Ｔｉ粉和Ｆｅ粉的位置相继形成；固态反应还导致了反应的不完全性，原子固态扩散的较低速率使尺寸较大的Ｆｅ粉内残留少量无ＴｉＣ粒子分布区。     

Effect of particle size of iron on reaction velocity of combustion synthesis of Ti-C-Fe system

Four Ti-C-Fe powder mixtures, with a same molar ratio but different particle sizes of Fe and Ti, were used to measure the reaction velocity of the combustion synthesis. The results show that in the case of the finer Ti powder used, the reaction velocity of mixture with the finer Fe powder is higher than that with the coarser Fe powder. However,in the case of the coarser Ti powder used, the reaction velocity of mixture with the finer Fe powder is lower than that with the coarser Fe powder. The effect of particle size of Fe powder on reaction velocity can be explained with the previously proposed mechanisms of the combustion synthesis of Ti-C-Fe system.     

Ti3AlC2与Fe在高温下的反应行为（英文）

通过TG-DTA、XRD、SEM和EDS的分析,研究Ti3AlC2与Fe在高温下的互相反应。结果表明,当烧结温度在659.9℃以上时,Ti3AlC2与Fe主要以放热反应为主,当烧结温度为760~1045℃时,Ti3AlC2与Fe之间的反应较弱,并开始生成TiC0.625相;随着烧结温度升到1045℃时,Ti3AlC2的衍射峰逐渐消失,烧结产物的衍射峰只有TiC0.625和Fe(Al)固溶体;随着温度的进一步升高,烧结产物的衍射峰基本为TiC0.625和Fe(Al)固溶体不变。采用SEM和EDS分析可知,该反应主要发生了两个过程,其一,Ti3AlC2发生了分解,Ti3AlC2中的Al发生了析出,并固溶到基体的金属相中形成Fe(Al)固溶体,而Ti3AlC2中Ti和C则形成了TiC0.625陶瓷相。其二,Fe原子沿着Ti3AlC2分解形成的Al空位渗入到Ti3AlC2颗粒中,进而导致Ti3AlC2进一步分解成粒径更小颗粒。Ti3AlC2中Al的析出是导致Ti3AlC2在远低于其分解温度下就与Fe发生反应的主要因素。     

Combustion Synthesis of Fe-Cu-TiC Composites under Electric Field

以配料比为15%(Ti+C)-65%Fe-20%Cu (质量分数)（Ti:C化学计量比为1:1）的Fe-Cu-Ti-C体系为研究对象,研究该体系在不同温度下的燃烧合成过程。Fe-Cu-TiC复合材料在759 ℃的点火温度下完成电场辅助燃烧合成,该电场辅助由Gleeble-3500D热模拟机提供。Fe-Cu-Ti-C体系燃烧合成的四步模型被提出,描述了Fe-Cu-TiC复合材料的在电场作用下的燃烧合成过程。它包括 (I) 预热阶段、(II)固相扩散阶段、(III) 燃烧合成阶段、(IV) 后续阶段。从阶段I到阶段II,反应物原子的固相扩散随着温度的增加而增加。从阶段II到阶段III,C原子扩散到Ti原子,直至紧密的与其接触。在III的初始阶段,Ti开始和C在界面处发生反应：Ti(s) + C(s) =TiC(s),并且Ti粒子周围形成一层很薄的固相产物TiC层。在III的后续阶段,C原子穿过固相产物TiC层,扩散到Ti粒子中,继续发生化学反应,直到TiC粒子析出。在第IV阶段,TiC颗粒逐渐的形核和长大,在SEM中可以看出TiC是球形颗粒。     

TiC-Al金属陶瓷自蔓延高温合成中的显微组织转变

用燃烧波淬熄法研究了TiC-Al金属陶瓷自蔓延高温合成中显微组织的转变,淬熄试样中保留了未反应区、反应区及反应完成区.用扫描电子显微镜观察了燃烧反应中的显微组织转变过程,用能谱仪分析了各微区的成分变化,测量了燃烧温度和燃烧波蔓延速度,并用XRD分析了反应产物相的组成.结果表明,Ti-C-Al系燃烧反应起始于铝粉熔化后与固态钛粉反应生成Al3Ti,并随着反应温度的升高,TiC颗粒从溶有钛和碳的铝熔体中析出;当Al3Ti熔化后,从熔体中也析出TiC颗粒,最终产物组织中除大量的TiC颗粒分布于铝基体中外,还发现有少量的Al3Ti存在,可能与使用的钛粉和铝粉的原料颗粒较粗有关.     

TiB_2－xAl复合材料的结构形成分析

研究了Ｔｉ和Ｂ颗粒尺寸的变化对自蔓延高温合成（ＳＨＳ）ＴｉＢ_２—ｘＡｌ金属基复合材料的燃烧温度和燃烧波速度的影响。结果表明，Ａｌ颗粒不直接参与化学反应，其尺寸变化对ＳＨＳ过程的影响要小得多，但是反应过程中形成的熔融Ａｌ能阻止ＴｉＢ_２晶粒的长大，因而可以控制ＳＨＳ产物的结构。通过燃烧波峰淬熄（ＣＦＱ）法，对该复合材料的ＳＨＳ过程结构形成机理进行了分析。     

Self-propagating high-temperature synthesis in Ti-W-C system

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Effects of C particle size on the ignition and combustion characteristics of the SHS reaction in the 20 wt.% Ni–Ti–C system

C particle size plays an important role in the ignition and combustion characteristics of the SHS reaction in the 20 wt.% Ni–Ti–C system. When coarse C particles (38 and 75 μm) are used, the SHS reactions consist of two different combustion stages with different brightness intensity of the combustion wave; XRD results indicate that the first and second combustion stages mainly correspond to the formation of Ni–Ti compounds and TiC ceramics, respectively. However, the final reaction is incomplete with a few Ni–Ti compounds and unreacted C. In contrast, when the fine C particle (1 μm) is used, the SHS reaction consists of only one combustion stage with high brightness intensity of the combustion wave; XRD result indicates that final products consist of TiC and Ni, without any intermediate phase. With the decrease of C particle size, the wave velocities increase, and the ignition time becomes shorter. In addition, the morphology of TiC particulate changes to near-spherical, as C particle size decreases.     

Local reactions of KCl particles with iron,nickel and chromium surfaces

Corrosion of superheaters caused by the deposition and subsequent reaction of alkali chloride containing ashes is one of the main material problems by combustion of biomass for energy conversion. The alkali chloride particles are formed during combustion and transported as aerosol or in the vapor phase within the combustion gas, subsequently sticking on the surface of the metallic tube. The initial reaction between the tube surface and the salt particle plays a major role in the initiation of the corrosion process and, therefore, are studied in detail in this work. The salt particles were locally deposited by means of thermophoresis within an aerosol generator, available at MPIE. Studies on the reaction of KCl particles with iron surfaces showed that a reaction takes place already at 300 °C. In N₂‐O₂ atmospheres, the attack was very local, whereas the addition of 0.05 vol.% HCl to the reaction gas led to complete coverage of the iron surface with chloride. In contrast, reactions of KCl with nickel and chromium surfaces start to be significant only at 500 °C and higher. The paper summarizes the reaction behavior of Fe, Ni and Cr after thermophoretic deposition of KCl particles and subsequent reaction at elevated temperatures.     

反应火焰喷涂TiC/Fe复合涂层组织及形成机理

以TiFe粉和碳的前驱体（石油沥青）为原料通过前驱体碳化复合技术制备了Ti-Fe-C系反应喷涂复合粉末,并用普通火焰喷涂技术制备了TiC/Fe陶瓷金属复合涂层.观测了喷涂粉末、淬熄实验获取的飞行粒子以及涂层的形态、相和组织结构.结果表明：前驱体碳化复合Ti-Fe-C系喷涂粉末有非常紧密的结构;可有效的解决反应喷涂过程中原料粉末分离的问题.在反应火焰喷涂过程中,每一个喷涂粉末颗粒构成独立的微小反应单元,原料之间反应充分.在整个喷涂过程中喷涂粉末经历了熔化扩散、物相形成、碰撞后快速凝固三个阶段.所得涂层由TiC和Ti2O3共生聚集片层和细小TiC颗粒弥散分布于金属基体所形成的内晶型复合强化片层交替叠加而成.     

Structure of titanium-doped goethite rust

To investigate the influence of titanium addition on the formation and structure of goethite (α-FeOOH) rust which is one of main corrosion products of weathering steel, the artificially synthesized α-FeOOH rusts were prepared by hydrolysis of aqueous solutions of Fe(III) containing Ti(IV) at different atomic ratios (Ti/Fe) in the range 0-0.1. The obtained rusts particles were observed by TEM. Characterization by XRD, N₂ absorption, Mössbauer spectroscopy was also done. TEM observation revealed that the α-FeOOH rust particle size increased with the increase of Ti/Fe, and that Ti-enriched poorly crystalline particles were formed around the rust particles. XRD confirmed that the crystallite size increased with the increase of Ti/Fe, while the XRD peaks decreased in intensity. Specific surface area obtained by N₂ absorption increased with the increase of Ti/Fe. It is deduced from the obtained results that the addition of Ti(IV) increases the crystallite size of α-FeOOH, and produces double domain particles consisting of the particle core and a porous poorly crystalline shell. It is thought that such unique rust structure produced by titanium addition contributes to the protective properties of rust layer of the weathering steel.     

原位合成(Ti,W)C增强高铬铸铁复合材料的形成过程及三体磨损性能

通过原位生成法与铸造法相结合制备(Ti, W)C颗粒增强高铬铸铁复合材料,采用XRD、EDS、SEM等检测方法研究复合材料的反应过程、组织结构及抗三体磨损性能。研究结果表明:增强相(Ti, W)C的反应过程存在反应-融化-析出机制以及反应-固溶机制。(Ti, W)C颗粒与基体的界面为冶金结合。复合材料的抗磨损性能是其基体高铬铸铁的1.4倍,磨损机制为磨粒磨损-粘着磨损。     

Combustion synthesis of VC/Fe composites under the action of an electric field

Composites of VC/Fe have been synthesized from reactant mixtures of graphite, iron, and ferrovanadium by a field-assisted combustion synthesis method in a Gleeble thermal simulation instrument. With the aid of a high electric current, a relatively low onset temperature for the combustion reaction, between 691 °C and 813 °C, could be achieved. The ignition temperature and ignition delay time of the reaction decreased with the increase of the reactant V content and the preset heating rate of the process, and the decrease of ferrovanadium particle size. These technologic parameters also affected the final phase and grain size of vanadium carbide particles in the products.     

TiC-Ti复合材料自蔓延高温合成中的组织转变

用燃烧波淬熄法研究了TiC-Ti金属陶瓷自蔓延高温合成（SHS法）中的组织转变和反应机理。淬熄试样中保留了未反应区、反应区及已反应区。用扫描电子显微镜观察了燃烧反应中的显微组织转变过程，用能谱仪分析了各微区的成分变化，测量了燃烧温度Tc，并用XRD分析了反应产物的相组成。实验结果表明：TiC-Ti复合材料的自蔓延高温合成机理可以用溶解-析出机制来描述：Ti首先部分熔化，C溶解在Ti液中，并和Ti发生反应生成TiCx，随着温度的升高，TiCx熔化，形成Ti-C熔体，在降温过程中，细小的TiC大量从Ti-C熔体中析出并聚集，最终形成TiC增强Ti基复合材料。     

Microstructure and Wear Behavior of (Ti,V)C Reinforced Ferrous Composite

A (Ti,V)C/Fe composite was produced by a process which combines in situ synthesis with powder metallurgy technique using Ti, Fe, FeV and carbon powder. The microstructure of the Fe-(Ti,V)C composite was studied by scanning electron microscope and x-ray diffraction. The results show that the production of an iron matrix composite reinforced by (Ti,V)C particulates using the process is feasible. Fine (Ti,V)C particles are uniformly dispersed in the pearlite. The Fe-(Ti,V)C composite possesses excellent wear-resistance under the condition of dry sliding with heavy loads.     

Study of formation behavior of TiC in the Fe-Ti-C system during combustion synthesis

TiC particles were prepared in situ by self-propagating high-temperature synthesis (SHS) reaction in the Fe-Ti-C elemental powder mixture. The reaction behavior and formation route of synthesizing TiC in the Fe-Ti-C system were investigated. With Fe contents increasing, the adiabatic temperatures, reaction temperatures and TiC particles sizes obviously decreased. The addition of Fe promotes the reaction between Ti and C through a “bridging” effect. Fe plays an important role in controlling the reaction behavior and morphology of products, serving not only as a diluent to inhibit the TiC particles from growing, but also as an intermediate reactant to promote the reaction.     

Al_3Ti和Al_2O_3增强铝基复合材料的XD合成

通过XD(ExothermicDispersion)法原位反应生成Al2 O3 与Al3Ti复合增强的铝基复合材料 ,结果表明Al/TiO2 经充分混合、挤压成坯后 ,在真空炉中以一定的升温速率加热至 10 73K左右时发生剧烈的化学反应。由SEM ,XRD及能谱分析可知 :生成物Al2 O3 呈等轴颗粒状 ,Al3Ti呈棒状。主要分析了反应过程的热力学并简要说明了影响XD合成的主要因素     

锆,铝颗粒活化能尺寸效应的理论模型

提出了一个通过金属颗粒着火温度计算活化能的理论模型,着火温度的临界条件为燃烧反应产热率与对周围环境放热率达到热平衡。放热率由Knudsen数控制,铝颗粒燃烧产热率通过Arrhenius形式的模型计算,锆颗粒燃烧产热率由扩散模型计算,通过迭代计算,得到金属颗粒着火温度对应的活化能。结果表明,铝颗粒、锆颗粒的活化能随粒径增大而增大,与粒径的对数呈线性关系。在纳米至微米的更大尺寸范围内,单一理论模型不足以描述金属颗粒活化能的尺寸效应,而基于数据拟合的多项式模型更具有普适性。     

自蔓延反应火焰喷涂TiC-TiB2复相陶瓷涂层的水淬熄试验

用水淬熄法研究了Ti-B4C-C系自蔓延高温合成（SHS）反应火焰喷涂TiC-TiB2复相陶瓷涂层的反应过程与机理.结果表明,在喷涂过程中喷涂团聚颗粒各组元间、各组元与环境间存在多种反应的竞争,团聚颗粒飞行距离不同,反应得到的产物不同.喷涂的最佳距离为180mm,此处获得的球形粒子（陶瓷液滴）数量最多,团聚粉熔融最充分,获得的球形陶瓷液滴数量最多,形成的目标产物最理想.陶瓷液滴的形成始于钛粉的熔化,并通过扩散和毛细管作用向B4C和C颗粒渗透和浸润,经过自蔓延反应能量积累,最后SHS爆燃完成.当陶瓷液滴遇水淬熄后将以柱状方式结晶成毛线团状,可以用熔渣正规离子溶液模型描述液滴的结构.     

TiC颗粒增强钢基表面复合材料的组织均匀性

为了优化自生TiC颗粒增强钢基表面复合材料的工艺参数,利用真空实型铸渗方法制备了自生TiC颗粒增强钢基表面复合材料,重点研究了自生TiC颗粒增强钢基表面复合材料的组织均匀性。结果表明,从基材和复合层间的界面到复合层表面,TiC颗粒尺寸逐渐增大,圆整度逐渐变差,其中Ti-C-20wt%Fe体系复合层中TiC颗粒的尺寸增长量(由1μm增长到2～3μm)明显小于Ti-C体系(由1～2μm增长到约10μm)。与Ti-C体系相比,Ti-C-20wt%Fe体系制备得到的复合层中元素分布、硬度和TiC颗粒的体积分数较均匀,在复合层相同位置上TiC颗粒较小,圆整度较好。