Mo_5Si_3-Al_2O_3复合材料的微观结构与摩擦磨损性能

采用机械化学还原法结合热压烧结制备Mo_5Si_3-Al_2O_3复合材料,采用XRD、SEM等对复合材料的相组成、微观结构及磨损机理进行分析。结果表明:复合材料主要物相为Mo_5Si_3、Al_2O_3和Mo_3Si,其组织均匀细小,晶粒尺寸在1~5μm之间。Mo_5Si_3-Al_2O_3复合材料具有优异的抗摩擦磨损性能。随载荷增加,其摩擦因数和磨损率降低。载荷为10 N时,其摩擦因数和磨损率分别为0.176和6.23×10~(–6) mm~3/(N·m)。与对磨件GCr15钢球相比,其磨损率降低近1个数量级。Mo_5Si_3-Al_2O_3复合材料主要的磨损机理为氧化磨损和从低载荷下的粘着-剥落磨损过渡到高载荷下的磨粒磨损。     

热压法制备Mo_5Si_3-Al_2O_3复合材料及力学性能研究

以MoO_3粉、Mo粉、Si粉和Al粉为原料,采用机械合金化结合热压烧结法制备了Mo5Si3-Al_2O_3复合材料,研究了Al_2O_3含量对Mo5Si3-Al_2O_3复合材料微观结构和力学性能的影响。结果表明:复合材料的主要物相组成为Mo5Si3、Al_2O_3和Mo3Si,其平均晶粒尺寸在51~99 nm之间,具有纳米晶结构。Al_2O_3的引入细化了晶粒,提高了复合材料的致密度和力学性能。Mo5Si3-30%Al_2O_3复合材料的致密度、硬度、抗弯强度和断裂韧性分别为99.6%、13.2 GPa、322 MPa和6.43 MPa·m1/2。     

放电等离子烧结原位制备MoSi_2陶瓷的显微组织与力学性能

以Mo、Si混合粉末为原料,采用放电等离子烧结技术原位制备MoSi_2陶瓷。利用X射线衍射仪、扫描电镜、维氏硬度计、电子万能材料试验机等,研究1 300,1 400和1 500℃下烧结的MoSi_2陶瓷物相组成、微观结构及力学性能。结果表明:MoSi_2陶瓷由MoSi_2和少量Mo_5Si_3/Mo_(4.8)Si_3C_(0.6)及SiO_2组成;随烧结温度升高,第二相Mo_5Si_3/Mo_(4.8)Si_3C_(0.6)含量增多,并发生Mo_5Si_3向Mo_(4.8)Si_3C_(0.6)的相转变;第二相Mo_5Si_3/Mo_(4.8)Si_3C_(0.6)含量增多可细化基体组织,材料沿晶断裂的比例增加,具有一定的强韧化作用;1 500℃烧结的MoSi_2陶瓷综合性能最佳,其致密度为99.5%,维氏硬度为9.8 GPa,抗弯强度和断裂韧性分别为313 MPa和2.9 MPa·m~(1/2)。     

MoSi_2-Mo_5Si_3复合材料的烧结工艺

系统研究了MoSi2 -Mo5Si3复合材料的烧结工艺。结果表明 ,MoSi2 -Mo5Si3复合材料理想的烧结温度为 1 40 0～ 1 50 0℃ ,保温时间为 1 .0～ 1 .5h ,当Mo5Si3含量为 1 6%时 ,MoSi2 -Mo5Si3复合材料具有最大的相对密度和硬度。     

球磨参数对机械合金化制备Al_2O_3/Mo_5Si_3复合粉体特性的影响

以MoO3粉、Mo粉、Si粉及Al粉为原料,采用机械化学还原法制备了Al2O3/Mo5Si3复合粉体。利用XRD、SEM等对复合粉体在球磨过程中的物相转变和形貌进行表征,并对球磨参数对机械合金化过程的影响进行探讨。结果表明,原料粉体球磨10 h后转变为Al2O3/Mo5Si3复合粉体,反应较完全。随球磨时间延长,复合粉体细小均化,粉体粒度较小,球磨20h后粉体粒度在3~5μm之间,随球磨转速的提高,球磨时间延长,球磨提供能量提高,反应开始时间变短。     

Cu/Mo_5Si_(3p)复合材料的摩擦磨损性能研究

采用销—盘式摩擦磨损试验机研究了液相烧结制备Mo5Si3颗粒弥散强化铜合金在滑动干摩擦条件下的摩擦磨损行为。结果表明:Cu/Mo5Si3p复合材料具有优良的摩擦磨损性能。随着Mo5Si3含量的增加Cu/Mo5Si3p复合材料的硬度增加,摩擦系数和磨损失重量降低。Mo5Si3含量低时,Cu/Mo5Si3p复合材料的磨损机制为犁沟变形和粘着磨损为主,而Mo5Si3含量高时则为犁沟变形磨损为主。     

La_2O_3增强增韧(Mo_(0.7),W_(0.3))Si_2复合材料的作用机理

通过多组元自蔓延反应及热压烧结方法制备了(Mo0.7,W0.3)Si2材料及掺杂1.5.%(质量分数)La2O3的(Mo0.7,W0.3)Si2复合材料。采用X射线衍射(XRD)、扫描电镜(SEM)、电子探针(EPMA)、透射电镜(TEM)及物理机械性能测试方法对复合材料组织性能进行了表征,并深入探讨了其强韧化机理。结果表明:La2O3掺杂的(Mo0.7,W0.3)Si2复合材料由(Mo,W)Si2、(Mo,W)5Si3、硅酸镧构成。掺杂La2O3后,La2O3与脆性相Si O2形成硅酸镧化合物,与未掺杂La2O3的(Mo0.7,W0.3)Si2相比,复合材料的晶粒明显细化,强度和韧性均明显提高,其强化原因有细晶强化及颗粒弥散强化;韧化原因有晶粒细化、Si O2的减少、位错缠结、颗粒的拔出、裂纹偏转及微裂纹产生。     

可低温烧结的微波介电陶瓷La_7Nb_3Mo_4O_(30)及其制备方法

<正>专利申请号:CN201310478109.1公开号:CN103553614A申请日:2013.10.14公开日:2014.02.05申请人:桂林理工大学本发明公开了一种可低温烧结的微波介电陶瓷La7Nb3Mo4O30微波及其制备方法。可低温烧结的微波介电陶瓷的组成为La_7Nb_3Mo_4O_(30)。(1)将纯度为99.9%以上的La_2O_3、Nb_2O_5和MoO_3的原始粉末按     

等离子喷涂制备Mo-Si-B复合涂层的高温抗氧化行为研究

本文采用等离子喷涂法在钼电极表面制备了Mo-Si-B复合涂层,利用SEM观察涂层的显微形貌,通过XRD分析涂层的物相组成,通过DSC-TGA考察了涂层钼电极在空气环境中的抗氧化行为。结果表明:当Mo∶B∶Si添加比例达3∶1∶1时,钼电极的涂层由MoSi_2相和MoB相组成,涂层的内部致密,与基体钼电极结合紧密;在抗氧化过程中,涂层经历了氧化增重、平稳运行、再次增重3个阶段;涂层物相最终转化为MoSi_2相、Mo_5Si_3相、B_2O_3相和Si O2相。     

含Ti的Mo-12Si-8.5B合金在不同烧结温度下的微观组织和力学性能

采用放电等离子烧结技术在不同温度下制备Mo-12Si-8.5B和Mo-12Si-8.5B-8Ti合金,比较了两种合金的微观组织和室温力学性能。研究结果表明,Mo-12Si-8.5B由Mo_(ss),Mo_3Si和Mo_5SiB_2组成;Mo-12Si-8.5B-8Ti合金由(Mo,Ti)_(ss),(Mo,Ti)_3Si和(Mo,Ti)_5SiB_2构成,Ti在三个相中均产生了固溶。两种合金的密度、维氏硬度和抗弯强度在1 400～1 600℃烧结时增加较快,在1 600～1 700℃烧结时无明显变化。与Mo-12Si-8.5B相比,1 700℃下烧结的Mo-12Si-8.5B-8Ti合金的硬度和抗弯强度分别提高了10.2%和15.1%,即Ti的添加提高了Mo-12Si-8.5B合金的室温力学性能,这归因于Mo-12Si-8.5B-8Ti合金微观组织孔洞的减少和Ti在(Mo,Ti)_(ss),(Mo,Ti)_3Si和(Mo,Ti)_5SiB_2中的固溶强化效应。     

Recycling of High Ferrous Bauxite Reducing Slag for Synthesis of CaAl2 Si2 O8-Al2 O3-CaAl12 O19 Composite

CaAl_2 Si_2 O_8-Al_2O_3-CaAl_(12) O_(19)( CAS_2-Al_2O_3-CA_6) composite was synthesized through reaction sintering alumina and bauxite reducing slag.The CAS_2-Al_2O_3-CA_6 composite was mainly composed of α-Al_2O_3,CAS_2,and CA_6.Gehlenite( Ca_2Al_2 SiO_7,C_2AS) phase was effectively transformed to CAS_2 and CA_6through high-temperature reaction sintering under weak oxidizing atmosphere at 1400 ℃ for 4h.SEM( scanning electron microscopy) and EDS( energy dispersive spectroscopy) analysis indicated that black and needle-shaped Al_2O_3,rhombic or irregular polygonal-shaped Fe Al_2O_4,and glassy phase Ca_2Al_2 SiO_7disappeared after the reaction sintering.The light gray and flaky hexagon crystals of Ca Al_(12)O_(19)(10μm) and the grainy particles of Al_2O_3( 2-7μm) were observed in the CAS_2-Al_2O_3-CA_6 composite.The gray crystals of CAS_2 act as the binding phase and are distributed around CA_6 and Al_2O_3.CAS_2-Al_2O_3-CA_6 composite exhibits high refractoriness and service temperature,which are 1650 ℃ and 1450 ℃,respectively.Reaction sintering of alumina and bauxite reducing slag is a feasible method for the synthesis of CAS_2-Al_2O_3-CA_6 composite.     

CaO-SiO2-Al2O3-Fe2O3渣系脱磷行为

利用Factsage软件计算了Al2O3含量对CaO-SiO2-Al2O3-Fe2O3四元渣系熔点和黏度的影响,并通过实验研究了在1 400℃时,CaO-SiO2-Al2O3-Fe2O3四元渣系对高磷铁水脱磷行为的影响.结果表明:渣中Al2O3的质量分数在3％～6％之间时,随着A12O3含量的增加,渣系的熔化温度迅速降低,进一步增加渣中的A12O3含量,渣系的熔化温度逐渐增加;Al2O3对CaO-SiO2-Al2O3-Fe2O3渣系的黏度影响不大;渣中Al2O3的质量分数在3％～6％之间变化时,渣系脱磷能力变化不是很大,脱磷率维持在91％左右,进一步增加渣系中A12O3的量,脱磷率逐渐下降;Al2O3对脱磷率产生影响可能是其改变了炉渣中液相所占比例,进而影响磷从铁水中向液相渣的传质过程.     

MoSi2-Mo5 Si3复合材料的低温氧化研究

通过热重量分析、X射线衍射仪描电镜研究了MoSi2-Mo5Si3复合材料的低温氧化行为,指出材料低温氧化时,随Mo5Si量增多,材料氧化加剧,当Mo5Si3含量（质量分数）超过16％时发生“PEST”现象,由于MoO3晶须的大量存在,所形成的SiO2不能均匀连续地分布于材料表面,从而加剧了氧化。     

Oxidation of Al2O3-30%TiCN-0.2%Y2O3 Composite

Thecuttingtoolmaterialshavegoodoxidationre sistance ,buttheyareoxidizedathightemperature(about 10 0 0℃ )duringoperation .Themechanicalpropertyofthecuttingtoolmaterialswillbechange d[1,2 ] .Therefore ,researchonoxidationbehaviorofcuttingtoolsmaterialsathi…     

Al2O3-Y2O3 Nano- and Micro-Composite Coatings on Fe-9Cr-Mo Alloy

Al2O3-Y2O3 nano- and micro-composite coatings were deposited on Fe-9Cr-Mo substrates by using sol-gel composite coating technology. The processing includes dipping samples in a sol-gel solution dispersed with fine ceramic powders, which are prepared by high-energy ball milling. High-resolution microscopy （FE-SEM） analyses show that the coating is composed of composite particle clusters with an average diameter of 1μm, and the coating is relatively dense without cracking during drying and sintering stages. XRD analyses show that the oxide coating is mainly composed of α-Al2O3 and γ-Al2O3. The oxidation tests performed at 600℃ in air show that the coatings are provided with much improved resistance against high temperature oxidation and scale spallation. It is indicated that nano-structured composite particles and reactive elements are integrated into the coatings, which plays an important role in preventing agglomeration of nano-particles and initiation of cracks.     

Ni/Y_2O3-Al2O3 catalysts for hydrogen production from steam reforming of ethanol at low temperature

Y2O3-Al2O3 with different mole ratios of Y:Al were prepared by co-precipitation method. Catalysts Ni/Y2O3, Ni/Al2O3 and Ni/ Y2O3-Al2O3 were prepared by impregnation method. The result of BET showed that Al2O3 with relative high surface area was in favor of Ni distribution, whilst the TPR test demonstrated that composite support had appropriate synergistic effect between active constituent and sup-port, and NiO could be reduced more easily than loaded on the single support. H2-TPD test indicated that the catalyst NYA11 had lots of ac-tivity sites where H could be desorbed easily, which led to hydrogen-rich production over the catalyst. Composite support catalysts exhibited high activity for ethanol steam reforming (SRE), and the supported catalyst with composite of 1:1 mole ratio of Y:Al exhibited the optimum catalytic properties for SRE. Ethanol could be completely converted over catalyst NYA11 even at 450 °C, and there had no inactivation after 60 h continuous reaction, hydrogen yield appeared maximum 35.9% at 400 °C, and tended to increase with increasing H2O/EtOH molar ratio and feed flow rate.     

Microstructure and properties of Al2O3-Al(Si) and Al2O3-Al(Si)-Si composites formed byin situ reaction of Al with aluminosilicate ceramics

Al₂O₃-Al(Si) and Al₂O₃-Al(Si)-Si composites have been formed byin situ reaction of molten Al with aluminosilicate ceramics. This reactive metal penetration (RMP) process is driven by a strongly negative Gibbs energy for reaction. In the Al/mullite system, Al reduces mullite to produce α-Al₂O₃ and elemental Si. With excess Al (i.e., x > 0), a composite of α-Al₂O₃, Al(Si) alloy, and Si can be formed. Ceramic-metal composites containing up to 30 vol pct Al(Si) were prepared by reacting molten Al with dense, aluminosilicate ceramic preforms or by reactively hot pressing Al and mullite powder mixtures. Both reactive metal-forming techniques produce ceramic composite bodies consisting of a fine-grained alumina skeleton with an interpenetrating Al(Si) metal phase. The rigid alumina ceramic skeletal structure dominates composite physical properties such as the Young’s modulus, hardness, and the coefficient of thermal expansion, while the interpenetrating ductile Al(Si) metal phase contributes to composite fracture toughness. Microstructural analysis of composite fracture surfaces shows evidence of ductile metal failure of Al(Si) ligaments. Al₂O₃-Al(Si) and Al₂O₃-Al(Si)-Si composites produced byin situ reaction of aluminum with mullite have improved mechanical properties and increased stiffness relative to dense mullite, and composite fracture toughness increases with increasing Al(Si) content. This article is based on a presentation made in the “In Situ Reactions for Synthesis of Composites, Ceramics, and Intermetallics” symposium, held February 12–16, 1995, at the TMS Annual Meeting in Las Vegas, Nevada, under the auspices of SMD and ASM-MSD (the ASM/TMS Composites and TMS Powder Materials Committees).     

Al_2O_3La_2O_3Y_2O_3/Cu复合材料的电弧侵蚀特性研究

采用喷射沉积和内氧化法制备出Al2O3La2O3Y2O3/Cu复合材料,研究该材料在直流20 V/20 A的工作条件下触点的电弧侵蚀特性,并与Al2O3/Cu材料进行了对比分析.利用电子天平、扫描电镜等方法分析电弧侵蚀后触点的质量变化和表面微观结构.结果表明,通过添加Y2O3、La2O3稀土氧化物颗粒,可有效降低触头材料的材料转移量.Al2O3La2O3Y2O3/Cu材料的抗熔焊性和抗烧损性优于Al2O3/Cu材料的性能.在直流阻性负载条件下Al2O3La2O3Y2O3/Cu阳极触头表面形成凹坑,阴极触头表面形成凸起,触点表面显示出浆糊状凝固物和喷发坑等电弧侵蚀形貌特征.     

疲劳性能不合格的38Si7弹簧钢夹杂物分析

  针对工业生产38Si7弹簧钢疲劳强度不合格的问题,借助光学显微镜和扫描电镜,并结合数学理论模型,从夹杂物的角度分析38Si7弹簧钢疲劳强度不合格的原因。研究结果表明：工业生产38Si7弹簧钢中的夹杂物主要组成为CaO(MgO) Al2O3 SiO2三元复合夹杂物,而且圆截面上中心区域复合夹杂物中Al2O3的含量明显低于外层复合夹杂物中Al2O3的含量;根据夹杂物等效投影面积模型得出,当疲劳失效为内部起裂时,临界夹杂物尺寸大约为6.5μm,当疲劳失效为表面起裂时,临界夹杂物尺寸大约为5.5μm。当弹簧钢中的夹杂物尺寸大于临界夹杂物尺寸时,容易造成疲劳强度失效。