铝对3Ti/SiC/C体系自蔓延高温合成Ti_3SiC_2的影响

采用3Ti/SiC/C粉体为原料,通过自蔓延高温合成技术制备了Ti3SiC2材料。探讨Al助剂对制备Ti3SiC2的作用。研究结果发现C-SiC-3Ti粉体能够产生SHS反应,产品由TiC、Ti5Si3和Ti3SiC2三相组成,Ti3SiC2含量约46%。添适当Al可显著促成Ti3SiC2相合成。选用3Ti/SiC/C/0.3Al粉体作原材料,产物中Ti3SiC2含量高达92.5wt%。     

不同原料体系对无压烧结合成Ti3SiC2的影响及其腐蚀行为

通过液相磁力搅拌混合原料粉末,压片后无压烧结合成了三元Ti3SiC2,研究不同原料配比Ti/Si/C,Ti/SiC/C/和TiC/Si/Ti对合成Ti3SiC2的影响,同时为了比较,在相同条件下加入少量Al或Sn,研究其对Ti3SiC2的合成过程及最终产物的影响,并探讨Ti3SiC2的合成机理.结果表明:3Ti/1.2Si/2C/0.1Al在1400 ℃无压烧结合成了较高纯度的Ti3SiC2,Al粉的加入可以降低混合粉末的起始反应温度,有利于三元层状化合物Ti3SiC2的合成和纯度的提高,其合成机制为,在铝粉形成的熔池中,经形核钛和硅反应生成钛硅金属间化合物,钛与石墨反应生成碳化钛,随后扩散,长大,随着温度的升高,反应生成三元层状Ti3SiC2.而以TiC或SiC为Ti或Si源制备的Ti3SiC2含杂质较多,不适用于无压烧结合成Ti3SiC2.合成的Ti3SiC2在HF溶液中经200 ℃溶剂热反应后,产物主要为两种不同晶型的SiC和AlF3立方体,且随着反应时间的延长,AlF3的含量增加,结晶更完善.     

原料体系对Ti3SiC2合成过程中相组成和显微结构演变的影响

分别以粉末钛粉、硅粉、石墨和钛粉、碳化硅、石墨为原料,采用热压烧结法制备了Ti3SiC2材料,借助XRD和SEM手段研究了原料体系和烧成温度对试样相组成、致密化程度和显微结构的影响,并分析了反应烧结机理。结果表明:(1)随着温度的升高,钛粉-硅粉-石墨体系较钛粉-碳化硅-石墨体系合成出的Ti3SiC2块体材料纯度更高;(2)钛粉-硅粉-石墨体系在烧结温度低于1300℃时,主要以Ti5Si3、TiC和残余的硅粉、石墨反应生成Ti3SiC2,在烧结温度为1300～1600℃时,主要以形成的液相Ti-Si(L)与TiC反应生成了Ti3SiC2;钛粉-碳化硅-石墨体系在1485℃液相出现之后,颗粒经历重排和溶解再析出的过程,在液相中生成Ti3SiC2。     

添加铝对机械活化辅助合成Ti_3SiC_2粉末的影响(英文)

以Ti,Si,TiC并添加Al的混合粉末为原料,采用机械活化辅助自蔓延合成法制备了Ti3SiC2粉末。研究表明,机械活化过程可将原料的粒度尺寸细化至10μm以下,反应物活性提高,并能激发自蔓延合成反应生成Ti-Si,SiC,TiCx等中间相。在上述条件下,合成单相Ti3SiC2粉末的温度可降至1350℃。反应机理为:Al作为脱氧剂通过抑制其它元素的氧化来促进主相的生成,且在反应物中优先熔化形成局部微小熔池,加速了反应物的扩散并生成TiCx和Ti5Si3中间相,从而促进Ti3SiC2粉末的生成。     

稀释剂含量对自蔓延高温合成Si3N4-SiC-TiN陶瓷的影响

以TiSi2和SiC为原料,利用自蔓延高温合成(self-propagation high-temperature synthesis,SHS)方法合成直径为24mm的Si3N4-SiC-TiN陶瓷.通过理论计算和实验研究了不同孔隙率压坯中稀释剂SiC含量对反应物TiSi2转化率的影响.结果表明:SiC在一定范围内增加有利于TiSi2的氮化,且含40%(质量分数,下同)SiC和50%SiC的压坯在燃烧合成过程中发生了SiC的氮化反应.压坯孔隙率为50%(体积分数,下同)时,反应物TiSi2氮化充分,最终产物为Si3N4-SiC-TiN.孔隙率为45%,含量为30%SiC和40%SiC压坯的合成产物中残留游离Si,50%SiC压坯的合成产物中未发现游离Si.在稀释剂含量为35%SiC,氮气压力为150 MPa条件下,所得的Si3N4-SiC-TiN复相陶瓷抗弯强度达430 MPa,断裂韧性为3.6MPa·m1/2.     

无压烧结制备Ti–Al–C系三元层状陶瓷

以TiC粉、Al粉、Ti粉为原料,采用无压烧结工艺制备高纯Ti–Al–C三元层状陶瓷,探究了烧结温度、烧结时间、烧结助剂等对Ti–Al–C系三元层状陶瓷制备的影响。结果表明:在一定范围内提高烧结温度和烧结时间能减少杂质相的产生,不添加助剂情况下在1 400℃下保温3 h能得到80%(质量分数)以上的Ti–Al–C系三元层状陶瓷,该条件下掺入少量Si粉或Sn粉能得到高纯Ti–Al–C系三元层状陶瓷。TiC、Al、Ti和Si质量比为2.0:1.2:1.0:0.1的原料粉末在1 400℃保温3 h能得到纯度99%以上的Ti_3AlC_2陶瓷,TiC、Al、Ti和Sn质量比为2.0:1.2:1.0:0.1与TiC、Al、Ti和Sn质量比为1.0:1.2:1.0:0.1的原料粉末在1 400℃保温3 h均能制备出纯度99%的以Ti_3AlC_2为主晶相的Ti_3AlC_2/Ti_2AlC复相陶瓷。     

利用多晶硅切割废料燃烧合成SiC基复相材料

利用多晶硅切割废料,采用燃烧合成的方法成功制备了SiC/Si2N2O及SiC/SiAlON复相粉体材料,并以该粉体为辐射基料制备出高温红外发射涂料。研究了原料配比对产物物相组成和微观形貌的影响,讨论了掺入C粉和Al粉的燃烧反应机理。实验结果表明,当反应剂中SiC∶Si∶C=68∶56∶0(质量比)时,合成产物中的Si2N2O含量最大;当反应剂中SiC∶Si∶C∶Al=68∶53∶24∶21时,合成产物中的SiAlON含量最高,配制成的高温红外涂料的红外发射率数值最高,在2.5～23.5μm波段范围内达到了0.92。     

Combution Synthesis of SiC-based Composite Materials from Kerr Loss Silicon

利用多晶硅切割废料,采用燃烧合成的方法成功制备了SiC/Si2N2O及SiC/SiAlON复相粉体材料,并以该粉体为辐射基料制备出高温红外发射涂料.研究了原料配比对产物物相组成和微观形貌的影响,讨论了掺人C粉和Al粉的燃烧反应机理.实验结果表明,当反应剂中SiC∶ Si∶C =68∶ 56∶0(质量比)时,合成产物中的Si2N2O含量最大;当反应剂中SiC∶ Si∶C∶Al =68∶ 53∶ 24∶21时,合成产物中的SiAlON含量最高,配制成的高温红外涂料的红外发射率数值最高,在2.5 ～23.5 μm波段范围内达到了0.92.     

Ti3SiC2陶瓷粉末的制备

新型层状陶瓷材料Ti3SiC2集金属和陶瓷的优良性能于一身,如低密度、高熔点、良好的导电导热性、高弹性模量、高断裂韧性、耐氧化、耐热震、易加工且有良好的自润滑性。在高温结构陶瓷、电刷和电极材料、可加工陶瓷材料、自润滑材料等领域有着广泛的应用前景。本文综合介绍了Ti3SiC2粉求制备的研究进展。最近,作者以Ti／Si／C／Al元素粉为原料,采用无压烧结的方法制备出纯度较高的Ti3SiC2陶瓷粉末。为Ti3SiC2基复合材料的发展开辟了一条新途径。     

自蔓延高温合成Ni-Zn铁氧体反应机制的研究

采用“气窒法”实现燃烧波的“淬熄”，获得了自蔓延高温合成Ni-Zn铁氧体中不同阶段的燃烧产物，对燃烧产物进行XRD分析，并结合热力学和TG－DTA分析，探讨了自蔓延高温合成Ni-Zn铁氧体的反应机制，研究结果表明，Fe粉在高压氧气下被氧化生成Fe2O3并放出大量的热，使自蔓延反应进行，同时Fe2O3与ZnO,NiO接触，以溶解析出和扩散机制形成Ni-Zn铁氧体。     

超重力下燃烧合成高硬(Ti,W)C基复合陶瓷

用超重力下燃烧合成(combustion synthesis under high gravity)法制备了(Ti,W)C基复合陶瓷。用X射线衍射仪、场发射扫描电镜及能谱仪研究了陶瓷产品的物相组成与微观形貌。对陶瓷的形成机理进行了分析,同时对陶瓷的性能进行了测试。结果表明:(Ti,W)C陶瓷基体主要由TiC与(Ti0.55W0.45)C0.51组成;其形成机理主要分为两个阶段,首先在超重力下燃烧反应快速进行,生成液态氧化物位于上部、Ti-W-Fe-C-B合金液位于下部的分层熔体结构,最后由于C原子相对于B原子具有更高的浓度与更快的扩散速率,TiC在合金液相冷却过程中优先成核、析出,随即,(Ti0.55W0.45)C0.51依附于TiC而析出。力学性能测试表明,(Ti,W)C基复合陶瓷相对密度、Vickers硬度、弯曲强度及断裂韧性分别为99.3%,25.6GPa,1060MPa与8.5MPa·m1/2。     

Graphene nanoplatelets reinforced AgCuTi composite filler for brazing SiC ceramic

Graphene nanoplatelets (GNPs) were used as reinforcement in AgCuTi filler for brazing SiC ceramic. Ti from the filler reacted with SiC ceramic to form TiC and Ti₅Si₃ adjacent to the SiC ceramic. According to the TEM and HRTEM results, TiC layer exhibited good lattice matching with SiC substrate. TiC particles synthesized by the reaction between Ti and GNPs in situ promoted the heterogeneous nucleation of TiCu and Cu(s,s), and contributed to the refinement of microstructure. Shear tests results indicated that the adoption of GNPs affected the joint property significantly. The TiC particles and an appropriate TiC + Ti₅Si₃ layer thickness both relieved the residual stress of the brazed joint and thereby increased the joint strength. The shear strength of the joint reached the maximum value of 38 MPa when using AgCuTi/GNPs (GNPs reinforced AgCuTi) composite filler containing 1% GNPs, which was ～139% higher than that of the joint brazed with AgCuTi filler.     

Microstructural development during spark plasma sintering of ZrB2–SiC–Ti composite

The present study investigates the effect of Ti addition on the microstructure development and phase evolution during spark plasma sintering of ZrB₂–SiC ceramic composite. A ZrB₂–20?vol% SiC sample with 15?wt% Ti was prepared by high-energy milling and spark plasma sintering at 2000?°C for 7?min under 50?MPa. The X-ray diffraction test, microstructural studies and thermodynamic assessments indicated the in-situ formation of several compounds due to the chemical reactions of Ti with ZrB₂ and SiC. The Ti additive was completely consumed during the sintering process and converted to the ceramic compounds of TiC, TiB and TiSi₂. In addition, another refractory phase of ZrC was also formed as a result of sidelong reaction of ZrB₂ and SiC with the Ti additive.     

硅液相浸渍反应制备TiC/SiC和TiN/SiC复相陶瓷

以滤纸、酚醛树脂和氧化钛为原料,经过模压成型、固化、碳化及不同条件下渗硅制备了TiC/SiC和TiN/SiC复相陶瓷。通过X射线衍射和扫描电子显微镜研究了TiC/SiC和TiN/SiC复相陶瓷的微观结构和物相组成,测量了复相陶瓷的弯曲强度和断裂韧性。结果表明:真空条件下液态渗硅获得的TiC/SiC复相陶瓷具有多孔的微观结构,其弯曲强度和断裂韧性较小。氮气气氛下液态渗硅制备的TiN/SiC复相陶瓷结构致密,有较高的弯曲强度和断裂韧性。不同反应生成的TiC,TiN陶瓷颗粒对液态硅的润湿性不同,使得生成的复相陶瓷具有不同的微观结构。TiN/SiC复相陶瓷中TiN颗粒的引入,在基体与第二相颗粒间的界面上产生拉应力和压应力,使达到这一区域的裂纹偏转,从而获得增韧效果。     

The effect of carbon source and molar ratio in Fe–Ti–C system on the microstructure and mechanical properties of in situ TiC/Fe composites

The size, distribution, and morphology of TiC particle in Fe–Ti–C system have a great influence on the mechanical properties of TiC/Fe composites. In this work, TiC/Fe composites were fabricated in the Fe–Ti–C system with different carbon source and molar ratio by combustion synthesis and hot-pressing method. Morphology and size of ceramic particles, as well as microstructure, interface bonding and mechanical properties of composites were compared. The results showed that the size of TiC particles decreased with increase of Fe content of Fe–Ti–C systems fabricated by the same carbon source, while the particles change from spherical shapes to cubic shapes which can reduce stress concentration between ceramic particles and matrix. Furthermore, TiC/Fe composites fabricated by 5Fe–Ti-carbon blacks (CBs) system exhibited superior yield strength (1523 MPa) compressive strength (2203 MPa) and microhardness (691.5 HV), caused by the high interface bonding strength and lamellar pearlite matrix which can commendably limit the dislocation slip. By comparison, TiC/Fe composites fabricated by 21Fe–Ti-carbon nanotubes (CNTs) system showed higher fracture strain (25.85%) on account of the ferrite matrix with favorable plastic. This work reveals the influence of carbon source and molar ratio of Fe–Ti–C system on TiC/Fe composites, which is helpful to further improve the properties of TiC/Fe composites.     

Design,fabrication and properties of layered SiC/TiC ceramic with graded thermal residual stress

The finite element method (FEM) was used to design a symmetrical layered SiC/TiC ceramic with gradual thermal residual stress distribution. In the final model ceramic, the sequence of layers, from surface to inside, was SiC, SiC+2 wt.% TiC (S2T), SiC+4 wt.% TiC (S4T), SiC+6 wt.% TiC (S6T), SiC+8 wt.% TiC (S8T), and SiC+10 wt.% TiC (S10T); the thickness ratio of SiC:S2T:S4T:S6T:S8T:S10T was 1:1:1:1:1:10. After the model ceramic had been cooled from assumed sintering temperature 1850–20 °C in FEM calculation, gradual thermal residual stress, varying from surface compressive stress to inner tensile stress, was introduced. The designed ceramic then was fabricated by aqueous tape casting, stacking and hot-press sintering at 1850 °C, under 35 MPa pressure, for 30 min. The surface stress conditions of the sintered ceramic were tested by X-ray stress analysis, and those results were very close to the results from the FEM calculations. Compared with pure SiC and S10T ceramics fabricated by the same process, the designed ceramic showed excellent mechanical properties. The tested strength was close to the theoretical value. The strengthening and toughening mechanisms of the ceramic were ascribed to surface compressive residual stress.     

Ti3SiC2/Al2O3复合材料的制备与性能研究

以TiC／TiO2/Si／Al／Ti等为主要原料，采用热压法原位合成Ti2SiC2／Al2O3复合材料，分别探讨了Al掺入量和工艺制度对Ti3SiC2/Al2O3复合材料物相、显微结构以及性能的影响。结果表明：原位合成制备的Ti3SiC2/Al2O3复合材料与传统方法合成制备的纯Ti3SiC2材料相比，材料的硬度和致密度均有很大的提高。     

Brazing SiC ceramic using novel B4C reinforced Ag–Cu–Ti composite filler

The development of new composite fillers is crucial for joining ceramics or ceramics to metals because the composite fillers exhibit more advantages than traditional brazing filler metal. In this research, novel B₄C reinforced Ag–Cu–Ti composite filler was developed to braze SiC ceramics. The interfacial microstructure of the joints was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effect of B₄C addition and brazing temperature on the microstructure evolution and mechanical properties of the joints was analyzed. The results revealed that TiB whisker and TiC particles were simultaneously synthesized in the Ag-based solid solution and Cu-based solid solution due to the addition of B₄C particles. As the brazing temperature increased, the thickness of Ti₃SiC₂+Ti₅Si₃ layers adjacent to SiC ceramic increased. Desirable microstructure similar to the metal matrix reinforced by TiB whisker and TiC particles could be obtained at brazing temperature of 950 °C. The maximum bending strength of 140 MPa was reached when the joints brazed at 950 °C for 10 min, which was 48 MPa (~52%) higher than that of the joints brazed using Ag–Cu–Ti filler.