Ti_3SiC_2导电陶瓷材料的制备

本文将单质Ti粉、Si粉和C粉作为反应原料,利用机械合金化-热处理工艺制备高纯度的Ti_3SiC_2陶瓷粉体材料,研究了热处理温度对球磨粉体中Ti_3SiC_2纯度的影响.研究表明:单质混合粉体经过机械合金化可制备出含有TiC、TiSi_2等杂质相的Ti_3SiC_2陶瓷粉体,其中Ti_3SiC_2质量分数为71.5%;对球磨粉体进行热处理真空提纯发现,热处理温度对球磨粉体中的Ti_3SiC_2含量影响较为明显,当热处理温度为950℃时,粉体中Ti_3SiC_2质量分数提升至95%.     

TiC/Ti_3SiC_2泡沫陶瓷的制备和性能

采用聚氨酯泡沫为原始骨架,用高频感应加热反应熔渗制备TiC/Ti_3SiC_2泡沫陶瓷,研究了在制备过程中不同阶段泡沫体的Ti含量对其相组成、微区化学成分、显微组织以及抗压缩性能的影响。结果表明,随着泡沫体中Ti含量的增加,在其骨架中柑继生成TiC、Ti_3SiC_2及少量的Ti_5Si_3.骨架的致密度提高,泡沫材料...     

无压烧结Ti3SiC2/铝基复合材料组织与性能

MAX相具有独特的层状晶体结构,不但具备常用铝基复合材料外加陶瓷颗粒的性能特征,同时具有可与石墨媲美的摩擦性能.本文以Al粉、Si粉和典型MAX相Ti_3SiC_2为原料,采用冷压成型-无压烧结方法制备了Ti_3SiC_2/Al-Si复合材料,并通过金相显微镜、X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪(EDS)等分析手段,研究了烧结温度、Si元素含量对复合材料组织与性能的影响.研究表明:随着烧结温度从500℃提高到700℃,复合材料致密度先上升后下降,摩擦系数先降低后上升,硬度逐渐增大至最大值并基本保持稳定;随着Si质量分数从0增加到20.7%,复合材料的致密度逐渐降低,硬度逐渐增大,摩擦系数先降低后增大,晶粒尺寸随之下降,12.5%Si晶粒最为细小;烧结温度为650℃,Si元素质量分数为12.5%的铝基复合材料具有最低的摩擦系数0.18,相应的硬度为62 HV,致密度为92.12%.XRD物相和扫描电镜组织分析表明,复合材料的主要相组成为Al、Ti_3SiC_2,及由界面反应产生的Al_4C_3和Al的氧化产物Al_2O_3.     

Ti_3SiC_2-Ag复合材料与不同摩擦配副的摩擦磨损性能

采用放电等离子烧结技术制备了Ti3Si C2-Ag复合材料,研究了其在室温下与Si3N4、Al2O3、Si C等摩擦配副对摩时的摩擦磨损性能,并与纯Ti3Si C2材料在相同摩擦配副条件下的摩擦磨损性能进行了对比。运用扫描电子显微镜、X射线光电子能谱仪等对磨损表面的形貌组织和元素价态等进行了表征分析,并探讨了摩擦磨损机理。结果表明:摩擦配副材料的不同对Ti3Si C2-Ag复合材料的摩擦磨损行为有显著影响,Ti3Si C2-Ag复合材料与Si C和Si3N4对摩时,磨损率均较低,尽管存在晶粒拔出等机械磨损,但Ti O2和Si Ox等摩擦氧化膜的形成有效地抑制了晶粒拔出并起到了减摩作用;Ti3Si C2-Ag复合材料与Al2O3对摩时磨损率则较高,以脆性断裂、晶粒拔出为主的机械磨损是该摩擦副的主要磨损机制。Ti3Si C2材料与Si3N4和Al2O3对摩时,包含脆性断裂、晶粒拔出、脱落以及磨粒磨损在内的机械磨损是其主要的磨损机制;Ti3Si C2材料与Si C对摩时,磨损表面的塑性变形和氧化膜起到了抑制晶粒拔出的作用,使得Ti3Si C2的磨损率相对较低。     

SiC晶须对反应合成多孔TiB_2-TiC复合材料的影响

以Ti、B_4C和SiC晶须(SiC_w)为原料,采用自蔓延高温合成法制备了多孔TiB__2-TiC复合材料。讨论了SiC_w含量对TiB__2-TiC复合材料物相、组织形貌、孔隙率和抗压强度的影响。结果表明:不添加SiC_w时,复合材料中主要物相为贫硼相TiB和Ti_3B_4以及TiC和少量TiB__2;在5Ti+B_4C体系中加入SiC_w后,贫硼相TiB和Ti_3B_4逐渐减少直至消失,而出现富硼相TiB__2和TiC的含量增加。随着SiC_w含量的增加,复合材料的孔隙率逐渐增加,由38.46%增加至5_2.78%。当SiC_w含量小于1.0时,随着SiC_w含量的增加,多孔TiB_2-TiC复合材料的抗压强度明显增加,当SiC_w含量为1.0时,复合材料的抗压强度达到最大值56.04MPa。Ti与SiC_w反应会生成TiC、Ti_3SiC_2和TiSi_2等物相,消耗一定量的Ti,使得与B4C反应的Ti量减少,从而促进富硼相TiB_2形成和TiC的增多。并且在SiC_w表面形成颗粒状TiC或者层片状Ti_3SiC_2,增加SiC_w与TiB_2-TiC基体之间的结合,更有利于发挥SiC_w的强化作用。     

TiSiN-Ag磁控溅射薄膜的微结构和性能

为了研究Ag元素对Ti Si N薄膜结构及性能的影响,通过磁控溅射法制备了不同Ag含量的Ti Si N-Ag薄膜,采用EDS,XRD,XPS,TEM,CSM纳米压痕仪,UMT-2摩擦磨损仪和BRUKER三维形貌仪对薄膜的成分、微结构、力学性能和摩擦磨损性能进行了研究。结果表明:Ti Si N-Ag薄膜是由面心立方Ti N相、非晶Si3N4相和面心立方单质Ag相组成,单质Ag相的存在阻碍Ti N晶粒的生长;随Ag原子分数的增加,单质Ag相增加,导致Ti Si NAg薄膜的硬度和弹性模量逐渐下降;单质Ag相具有润滑作用,使薄膜硬度降低,磨痕中的硬质颗粒减少,摩擦系数从0.70降至0.39,磨损率也逐渐降低。     

激光熔覆原位自生碳化物增强自润滑耐磨复合涂层的高温摩擦学性能

利用激光熔覆技术在TC11合金表面成功制备NiCrBSi-Ti_3SiC_2-CaF_2-WC耐磨自润滑涂层。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)分析熔覆层的物相及微观组织;利用显微硬度仪对其硬度进行了测量。分别在室温(25℃),300℃和600℃条件下对涂层进行干滑动摩擦磨损实验,并分析其磨损机理。结果表明:涂层主要由γ-Ni共晶相,M_(23)C_6,TiC,(Ti,W)C,Ti_5Si_3硬质相以及少量的Ti_3SiC_2,CaF_2,TiF_3润滑相组成。激光熔覆层的显微硬度大幅度提高,显微硬度平均值为863.63HV_(0.2),约为基体的2.46倍,熔覆层总体摩擦因数和磨损率明显低于基体,在300℃条件下,涂层具有最低的摩擦因数(0.275)和磨损率(4.8×10~(-5)mm~3·N~(-1)·m~(-1))。     

TiC,Co 及添加剂对 Si_3N_4陶瓷显微结构和力学性能的影响

用扫描电镜、透射电镜和 X 射线衍射研究了 Si_3N_4-TiC-Co 系复合材料的相组成、显微结构和力学性能。发现 TiC 以 TiC 和 TiN 形式存在,Co 以 CoSi 形式存在。加入 TiC 和 Co 后,复合材料的力学性能得到明显改善,断裂韧性达到7.2MPa·m~(1/m),并且用 Y_2O_3作为助烧剂时,Si_3N_4晶粒成纤维状。     

Fe基超微晶合金的XRD研究

用XRD测定了退火Fe73.5Cu1M3Si13.5B9(M=Nb,Mo)合金中晶化相－－α-Fe(Si）和非晶相的结构，讨论了添加元素M＝Nb,Mo对Fe73.5Cu1m3Si13.5B9合金起始磁导率影响的原因，结果表明，添加Nb的Fe73.5Cu1Nb3Si13.5B9合金其α-Fe(Si）的尺寸小，Si含量高，且非晶相的铁磁性强，从而获得了较高的起始磁导率。     

Ti_2AlC-TiB_2对TiAl基复合材料组织及力学性能的影响

以Ti、Al和B4C为原料,采用真空电弧熔炼的方法制备了含Ti_2AlC-TiB_2增强相的TiAl基复合材料;分析了添加不同含量的Ti_2AlC-TiB_2对复合材料的物相组成、组织结构及力学性能的影响,并探讨了微观组织结构的形成机制。结果表明:Ti_2AlC-TiB_2/TiAl复合材料主要由TiAl、Ti3Al、TiB_2和Ti_2AlC等物相组成,TiB_2和Ti_2AlC分布在层片状的TiAl+Ti3Al基体中;随着原料中B4C含量的增多,复合材料组织中Ti_2AlC-TiB_2含量增多,且TiAl基体的晶粒被明显细化,TiB_2和Ti_2AlC分布于基体晶界或晶内。Ti_2AlC主要为层片状和板条状,尺寸5~15μm,而TiB_2颗粒形态与其含量有关,当Ti_2AlC-TiB_2含量小于20wt%时,TiB_2颗粒呈针棒状,尺寸为0.5~5μm,当Ti_2AlC-TiB_2含量增加到30wt%时,TiB_2颗粒主要呈块状,尺寸为5~20μm。Ti_2AlC由TiC与Ti-Al熔体发生包晶反应生成,Ti_2AlC和TiB_2的形成提高了Ti_2AlC-TiB_2/TiAl复合材料的硬度、塑性和抗压强度。当4Ti+Al+B4C的加入量为10wt%时,复合材料的变形量比纯TiAl提高14%,而抗压强度达到最高值1 591 MPa。Ti_2AlC和TiB_2通过裂纹偏转、颗粒钉扎、拔出等机制对Ti_2AlC-TiB_2/TiAl复合材料起到增强增塑的作用。     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Study on Bond Ability of Arc-Spraying Coatings with Different Surface Pretreatment on Cast-Iron

Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.     

Evaluation of fatigue life of steel using steel grain size

The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase.