用Ti／Ni／Ti多层中间进行Si3N4陶瓷的部分瞬间液相连接

在１３２３Ｋ和０．１ＭＰａ压应力下用Ｔｉ／Ｎｉ／Ｔｉ多层中间层进行Ｓｉ３Ｎ４陶瓷的部分瞬间液相连接。     

陶瓷/陶瓷(金属)部分瞬间液相连接

根据Ｓｉ３Ｎ４／Ｔｉ／Ｎｉ／Ｔｉ／Ｓｉ３Ｎ４和Ａｌ２Ｏ３／Ｔｉ／Ｃｕ部分瞬间相连接的实验结果,提出了描述部分瞬间液相连接过程和选择连接参数的模型以制备高强耐热接头,并对模型的应用进行了阐述,选择最佳连接参数的方法;（１）确定最佳反应层厚度;（２）选择靠近陶瓷中间层厚度;（３）决定连接时间。     

利用Ti／Ni共晶反应连接Si3N4／Ni的连接强度

本文用Ｔｉ箔在１３２３Ｋ直接进行Ｓｉ３Ｎ４／Ｎｉ的真空连接。结果表明,通过Ｎｉ、Ｔｉ之间的相互扩散形成的液体合金与Ｓｉ３Ｎ４发生界面反应,形成Ｓｉ３Ｎ４／ＴｉＮ／Ｔｉ５Ｓｉ４＋Ｎｉ３Ｓｉ（混合层）的接合界面,ＴｉＮ层和混合层的生长均 物线规律生长因子分别为１．３×１０＾－８ｍｓ＾－１／２和７．４×１０６－８ｍｓ＾１／２。接头弯曲强度随连接时间的增加,即Ｓｉ３Ｎ４／ＴｉＮ界面的连续和致密化而显著提高     

N+注入Ti/Si3N4的摩擦行为研究

研究了Ｓｉ３Ｎ４陶瓷材料及镀膜Ｔｉ／Ｓｉ３Ｎ４材料当Ｎ＾＋注入前后的摩擦学行为,考察了样品表面划痕轨迹的ＳＥＭ形貌,结合Ｘ射线衍射,对离子注入改性机理和摩擦学性能刊物了探讨,在Ｔｉ和Ｓｉ３Ｎ４界面上离子的混合及形成Ｔｉ２Ｎ相使Ｔｉ膜的附着力增加。     

等离子喷涂Al2O3+TiO2复合陶瓷涂层的组织结构

利用ＳＥＭ,ＴＥＭ,ＥＤＡＸ及Ｘ射线等手段研究了Ａｌ２Ｏ３＋ＴｉＯ２／ＮｉＣｒＡｌＹ复合陶瓷等离子喷涂层的组织结构,涂层呈片层状,Ａｌ２Ｏ３＋ＴｉＯ２陶瓷涂层由γ－Ａｌ２Ｏ３,ＴｉＯ２及少量的α－Ａｌ２Ｏ３组成,由于喷涂层温度比较高,部分熔化的Ａｌ２Ｏ３和大部分熔化的ＴｉＯ２发生了一定程度的互熔,形成了Ａｌ２Ｏ３＋ＴｉＯ２共晶组织。片层内由Ｎｉ基固溶体及弥散分布其上的γ相（Ｎｉ３Ａｌ）组成,片间为     

（Nb，Ti）C－Ni金属陶瓷中包裹结构的形成机理及其化学键研究

利用ＳＥＭ，ＥＰＭＡ，ＴＥＭ／ＥＤＡＸ等测试手段对（Ｎｂ，Ｔｉ）Ｃ－Ｎｉ金属陶瓷中的包裹结构形成机理作了研究。结果表明：它是由于该金属陶瓷在烧结时，细小的（Ｎ５，Ｔｉ）Ｃ粒溶解在熔融态的Ｎｉ中，当Ｔｉ，Ｎｂ及Ｃ的浓度达到大颗粒的饱和浓度时，在大颗粒表面沉淀，继而Ｎｉ向其扩散而形成的。用离散变分──Ｘ＿α方法计算表明：包裹层的金属键程度要比包裹结构中心的高。     

Si3N4陶瓷材料的氧化行为及其抗氧化研究

研究了Ｓｉ３Ｎ４陶瓷材料的氧化行为,同时探讨了通过表面处理使Ｓｉ３Ｎ４陶瓷材料表面形成一层Ｓｉ２Ｎ２Ｏ对其抗氧化性能的影响。实验结果表明,Ｓｉ３Ｎ４陶瓷材料在空气中的氧化行为服从抛物线规律。另外,用Ｘ射线衍射分析（ＸＲＤ）和Ｘ光电子能谱（ＸＰＳ）分析验证了Ｓｉ２Ｎ２Ｏ层的存在。由于形成了Ｓｉ２Ｎ２Ｏ层,Ｓi３Ｎ４陶瓷材 在１３００℃下氧化１００h后,氧化增重从原来的０．４２ｍｇ／ｃｍ＾２降低到０．２     

利用表面形成Si_2N_2O层提高Si_3N_4陶瓷材料抗氧化性能

根据对Ｓｉ－Ｎ－Ｏ系统相图的分析，首次在Ｓｉ３Ｎ４陶瓷材料表面形成Ｓｉ２Ｎ２Ｏ抗氧化层。其方法是利用Ｓｏｌ－Ｇｅｌ在Ｓｉ３Ｎ４陶瓷的表面涂上一层ＳｉＯ２（其中含有１０％的Ａｉ２Ｏ３）涂层后，在Ｎ２气氛中，并有Ｓｉ３Ｎ４粉末和ＳｉＯ２粉末存在的条件下，于１２７３～１６７３Ｋ的温度下进行热处理。用ＸＲＤ和ＸＰＳ分析验证了Ｓｉ２Ｎ２Ｏ（和／或Ｏ’－Ｓｉａｌｏｎ）层的存在。由于形成了Ｓｉ２Ｎ２Ｏ（和／或Ｏ’－Ｓｉａｌｏｎ）层，Ｓｉ３Ｎ４陶瓷材料在１５７３Ｋ的温度下氧化１００ｈ后，氧化增量从原来的０．４２ｍｇ／ｃｍ２降低到０．２４ｍｇ／ｃｍ２。     

α相和β相氮化硅的形成机理与动力

使用气流磨粉碎的硅粉（Ｓｉ）（Ｓｉ９９．３％，ｄｐ＝５．１μｍ，Ｓｇ＝３．２ｍ＾２／ｇ）和氮气（Ｎ２）（纯度９９．９９９８％）为反应物，在１３００～１３６７℃下反应形成β－Ｓｉ３Ｎ４，其反应机理与动力学参数被研究。反应产物由ＸＲＤ进行定量分析，相形成的机理和它们的形态用扫描电镜（ＳＥＭ）确定，我们发现α相和β相的形成机理不同，β－Ｓｉ３Ｎ４在１３００℃的实验数据适合于界面化学反应控制的动力学模型，     

新型高效催化剂气相聚合制备聚乙烯

综合报道了新型乙烯气相聚合ＭＧ型催化剂的制备及其聚合反应性能。研究了采用浸渍反应法制备含ＴｉＣｌ４／ＭｇＣｌ２／ＺｎＣｌ２／ＳｉＯ２醇／Ａｌ（ｉ－Ｂｕ）３的ＭＧ－４型高效催化剂。在压力１．０ＭＰａ下,乙烯聚合催化效率高达４４５￣８８４ｋｇＰＥ／ｇＴｉ,制得了表观密度≥ｇ／０．３７／ｃｍ＾３、重均颗粒分布（２０￣２００目）≥９７．７％、颗粒状态良好的聚乙烯。用ＤＳＣ、ＳＥＭ、ＷＡＸＤ对聚合产物进行了     

Partial transient liquid phase diffusion bonding of ZrC-SiC and 304 stainless steel by Ti/Ni interlayer: Microstructure and properties

The ZrC-SiC ceramic (ZS) was joined to 304 stainless steel (304SS) by using Ti/Ni interlayer. The joining process involves a transient liquid phase bonding at the ZS interface and a diffusion bonding at the 304SS interface. It is found TiC_x grew fast on ZS interface or precipitated as particles in certain region of transient liquid, and its distribution and morphology were controlled by Ti gradient. Small amount of Si dissolved into liquid and then precipitated as Ti₃Ni₂Si with similar lattice structure to Ti₂Ni. During solid-state diffusion, the TiNi reaction layer quickly transformed to refractory TiNi₃ layer with a small number of Kirkendall pores and Ni₅Zr phase at the TiNi₃/Ni boundary. The underlying mechanism of interfacial reactions and microstructure evolution were proposed. The maximum shear strength of 97 ± 10 MPa was achieved when joining at 960 °C for 3 h. The failure mainly occurred along TiNi₃/Ni boundary due to the presence of Kirkendall pores.     

Ni interlayer induced strengthening effect in alumina/alumina joint bonded with Ti/Cu/Ni/Cu/Ti composite foils

In this work, alumina ceramic was bonded to itself with composite foils (Ti/Cu/Ni/Cu/Ti). The thermodynamics analysis indicates that Ti-Cu liquid firstly formed and reacted with alumina to produce Ti₃Cu₃O reaction layer. Meanwhile, the consumption of element Ti within the Ti-Cu liquid by Ni interlayer optimized the microstructure of the joint. By thickening Ni interlayer from 0 µm to 100 µm at 1020 ℃, the joints' strength could be significantly improved by 130.6%. While the joints' strength decreased with the decomposition of reaction layer at the brazing temperature higher than 1020 ℃. The FE simulations show that the high-level stress concentration within the reaction layer could be ameliorated by Ni interlayer effectively, which was in accordance with the corresponding fracture characteristics. Although the joint's strength could be improved to 203.9 MPa by using 300 µm Ni interlayer, its improvement rate was limited with Ni interlayer constantly thickening.     

Microstructure and mechanical property of SiC whisker coating modified C/C composite/Ti2AlNb alloy dissimilar joints prepared by transient liquid phase diffusion bonding

SiC whisker coating was prepared on the surface of C/C composite successfully by CVD, and transient liquid phase (TLP) diffusion bonding was employed to realize the joining of SiC whisker coating modified C/C composite and Ti₂AlNb alloy using Ti–Ni–Nb foils as interlayer. The microstructure, shear strength and fracture behavior were investigated by scanning electron microscopy (SEM) with energy dispersive X-ray spectrometer (EDS), X-ray diffraction (XRD) and universal testing machine. The results show that SiC has good compatibility with C/C composite, and gradient interface formed between SiC-modified C/C composite and Ti₂AlNb alloy. When the bonding experiment was carried out under bonding temperature of 1040 °C and holding time of 30min with 5 MPa pressure in vacuum, the joints formed well and no obvious defects can be observed. The typical microstructure of joints is C/C composite/SiC + TiC/Ti–Ni compounds + Ti–Ni–Nb solid solutions/residual Nb/diffusion reaction layer/Ti₂AlNb alloy. With the increasing of bonding temperature, the thickness of joining area increased due to sufficient element diffusion. However, when bonding temperature is elevated to 1060 °C, some defects such as cracks and slag inclusions exist in the interface layer between interlayer and Ti₂AlNb. The joints with maximum average shear strength of 32.06 MPa are bonded at 1040 °C for 30min. C, SiC and TiC can be found on the fracture surface of joints bonded at 1040 °C which indicated that fracture occurred at the interface layer adjacent SiC layer.     

Influence of metallic properties on the fracture characteristics of Al2O3/Ti/Ni-laminated composites

The mutual confinement of ceramics and metals in laminated composites tends to change the original properties of ceramics and metals. In this study, two kinds of laminated composites, Al₂O₃/Ti and Al₂O₃/Ti/Ni, were prepared. Three-point bending experiments revealed that Al₂O₃/Ti underwent brittle fracture after elastic deformation. The fracture morphology analysis revealed that the Ti in Al₂O₃/Ti became brittle due to the formation of columnar crystals. The temperature gradient perpendicular to the direction of laminations during preparation was responsible for the formation of columnar crystals. The force–displacement curves of the Al₂O₃/Ti/Ni combine the properties of elastic deformation of ceramics and plastic deformation of metals. The reason why the Al₂O₃/Ti/Ni did not fracture completely in the bending experiments is that Ni maintained the toughness, and there is a good interfacial bond among Al₂O₃, Ti, and Ni. The indentation crack analysis revealed that cracks have long transverse propagation and short longitudinal propagation in both laminated composites. Finite element analysis revealed that this was due to compressive stress in the Al₂O₃ layer and tensile stress in the metal layer. This compressive stress consumes the crack energy in the longitudinal direction and stops the crack in the metal layer. The brittle to ductile gradient transition among Al₂O₃, Ti, and Ni, combined with the guidance of crack propagation direction by the interfacial layer, enhances the ability of Al₂O₃/Ti/Ni to resist damage.     

Microstructure and mechanical characterization of Si3N4/nickel-based superalloy joints with Ti/Au/Ni interlayers

The Si₃N₄ ceramic was joined to nickel-based superalloy via partial transient liquid phase bonding with Ti/Au/Ni interlayers. The interfacial microstructure and strength of joints were examined by methods of scanning electron microscopy, transmission electron microscopy, X-ray diffraction and a three-point flexural test. The results revealed the joint between Si₃N₄ and Ni interlayer consisted of TiN layer, Au-rich phase, Ni-rich phase and tiny TiO phase. The highest flexural strength of 211?MPa was achieved at room temperature, and the high-temperature strength of joints reached up to 117?MPa when testing at 1073?K. Post-bonding treatment indicated the joint strength of 120?MPa was obtained after annealing in air at 1073?K for 100?h, which exhibited superior oxidation resistant.     

Microstructures and mechanical property of ZrCx joints diffusion bonded using Ti/Ta/Ti as the interlayer

In present study, homogeneous joint of ZrC_x ceramic was achieved by diffusion bonding using Ti/Ta/Ti as the interlayer. The effect of bonding temperature and time on the microstructure and mechanical property of the joints was uncovered. The homogeneous joints can be formed at 1400 °C for 2 h and at 1500 °C for 1 h, respectively. The Ti/Ta/Ti interlayer prefers to form Ti-Ta solid solutions rather than to form carbides with ZrC_x ceramic during the bonding process, which is more readily to be dissolved with the base ceramic, thus contributing to the formation of the homogeneous joints. The mechanical property of the homogeneous joints can be comparable to that of the base ceramics due to the similar composition of the joint with the base ceramics. The unique microstructure feature and mechanical property of the homogeneous joints illustrate the great potential of our method for joining transition metal carbides.     

The influence of Ti: Si3N4 ratio on the microstructure evolution of Ti–Si3N4 reaction in Cu melts

In this work, through the study of the obtained Cu–Ti–Si–N intermediate products by controlling the reaction degree of Ti and Si₃N₄ powder in Cu melts at 1250～1300 °C, the effects of different Ti: Si₃N₄ mass ratios on the microstructure evolution of Ti–Si₃N₄ reaction in Cu melts were verified. When the mass ratio of Ti: Si₃N₄ is higher, such as 3.09:1, TiN will cooperate with Ti₅Si₃ and depend on each other to nucleate and grow to form TiN/Ti₅Si₃ composites. The formed TiN are spherical and wetted by Ti₅Si₃ to uniformly disperse in Cu melts. As a result, the TiN–Ti₅Si₃ hybrid reinforced Cu matrix composites will be formed. However, when the mass ratio of Ti: Si₃N₄ is lower, such as 1.37:1, Ti and Si₃N₄ will firstly react to form TiN and Ti–Si liquid. The formed TiN are irregularly polygonal and connect with each other. The Ti–Si liquid will combine with Cu melts to form Cu–Ti–Si liquid and finally form δCu₄Si, ηCu₃Si and τ₁-CuSiTi phases during the colling stage. In this case, TiN are difficult to be wetted, and the Ti–Si₃N₄ compact will keep its original shape and not spread in Cu melts.     

SiC陶瓷/SiC陶瓷及SiC陶瓷/Ni基高温合金SHS焊接中的界面反应及微观结构研究

采用加压自蔓延高温合成（ＳＨＳ） 焊接工艺,连接ＳｉＣ陶瓷／ＳｉＣ陶瓷以及ＳｉＣ陶瓷／Ｎｉ 基高温合金． 为了得到牢固的界面结合,实验了多种焊料配方． 而且基于润湿性、亲合性、ＳＨＳ起爆温度及界面反应的可能性等多方面的考虑,设计并实验了多层焊料配方． 微观结构显示,液相反应产物对ＳｉＣ 陶瓷的润湿性很好． 液相能够渗入陶瓷的表面开孔之中,而且界面结合很好． 成分分析证实,界面处发生了界面扩散,这有助于界面结合强度的提高．     

Effect of Ti–Si–Fe alloys on microstructure and properties of nitride/oxynitride bonded SiC ceramics sintered under CO/N2 atmosphere

Ti–Si–Fe alloys extracted from high-titanium blast furnace slag were utilized to replace part of the silicon powders, and then nitride/oxynitride bonded SiC ceramics were prepared by reactive sintering in graphite bed. Ti–Si–Fe alloys could react with CO/N₂ at a low temperature (1200 °C), and the addition of Ti–Si–Fe alloys could reduce the nitriding temperature of Si. Density functional theory calculations suggested that Ti–Si–Fe alloys enhanced reaction activity via weakening the strength of CO and NN bonds. The regional equilibrium phase diagrams of Si–C–N–O and Ti–Si–C–N–O under CO/N₂ atmosphere were calculated by thermodynamics. The change of whiskers morphology was observed by scanning electron microscope. Furthermore, the bulk density, the cold modulus of rupture, and the cold compressive strength improved with Ti–Si–Fe alloys content. The results showed that the addition of Ti–Si–Fe alloys not only significantly promoted nitriding of Si and formation of Si₃N₄ whiskers, but also improved the mechanical properties of the samples.