Al2O3/Cr3 C2/Ti(C,N)复合材料摩擦磨损性能研究

采用热压烧结技术制备了Al2O3/Cr3 C2/Ti(C,N)复合陶瓷材料,对其力学性能、摩擦磨损性能进行测试,用扫描电镜(SEM)对其磨损表面进行观察.结果表明:Al2O3/Cr3 C2/Ti(C,N)复合陶瓷材料具有良好的综合力学性能,在与硬质合金YG8环块摩擦中表现出较高的减摩抗磨性能,摩擦系数与磨损率较单相Al2O3降低近一半.对其磨损机理研究认为,磨粒磨损为主要磨损机制,高的强度和韧性是其具有良好耐磨性能的主要原因.     

添加MWCNTs陶瓷拉拔模具材料的摩擦特性研究

通过真空热压烧结方法制备了添加多壁碳纳米管(MWCNTs)的Al2 O3/TiC/MWCNTs陶瓷拉拔模具材料,研究了其摩擦磨损性能、机械性能,并对其磨损机理进行了分析.研究表明:MWCNTs能够减小Al2O3/TiC陶瓷拉拔模具材料的摩擦系数,当MWCNTs含量为5;时,Al2O3/TiC/MWCNTs陶瓷的摩擦系数最小;随着MWCNTs含量的增加,磨损量呈现先下降后上升趋势,当MWCNTs含量为4;时,Al2O3/TiC/MWCNTs陶瓷的磨损量最小.摩擦过程中,MWCNTs被拖覆到摩擦表面,具有自润滑效果,起到减摩抗磨作用.     

层数对梯度自润滑陶瓷刀具材料Al2O3/TiC/CaF2残余应力的影响

针对陶瓷减摩性能与耐磨性能不能在自润滑刀具中合理兼顾的难题,本研究将梯度功能材料设计思想引入Al2O3/TiC/CaF2自润滑陶瓷刀具材料的设计和制造中,并建立了该梯度自润滑陶瓷刀具材料的物理模型、组成分布模型和物性参数模型.采用有限元方法计算分析了层数对对称型梯度自润滑陶瓷刀具残余应力的影响,确定了最佳层数为7层.以本设计模型和有限元分析结果为基础,制备了分布指数为1.8的7层梯度自润滑陶瓷刀具材料Al2O3/TiC/CaF2.试验结果表明:所制备的梯度自润滑陶瓷刀具材料具有良好的力学性能.     

A12O3／Cr3C2／Ti（C，N）复合材料摩擦磨损性能研究

采用热压烧结技术制备了A12O3／Cr3C2／Ti（C,N）复合陶瓷材料,对其力学性能、摩擦磨损性能进行测试,用扫描电镜（SEM）对其磨损表面进行观察。结果表明：A12O3／Cr3C2／Ti（C,N）复合陶瓷材料具有良好的综合力学性能,在与硬质合金YG8环块摩擦中表现出较高的减摩抗磨性能,摩擦系数与磨损率较单相Al2O3降低近一半。对其磨损机理研究认为,磨粒磨损为主要磨损机制,高的强度和韧性是其具有良好耐磨性能的主要原因。     

添加纳米固体润滑剂的自润滑陶瓷材料高温摩擦磨损性能研究

采用真空热压烧结工艺制备了一种添加纳米固体润滑剂CaF2的自润滑陶瓷材料,研究其在室温25℃到600℃环境下与40Cr钢销干摩擦时的摩擦磨损性能.结果表明:自润滑陶瓷材料的摩擦系数与磨损率随环境温度的升高而逐渐降低,600℃时摩擦系数降低到0.21,磨损率降低到2.4×10-6 mm3/N·m.常温下自润滑陶瓷材料的磨损机理是磨粒磨损,高温环境同时存在磨粒磨损和粘着磨损.高温环境下摩擦表面纳米CaF2含量的增加和固体润滑膜的形成是摩擦磨损性能改善的主要原因.     

热物性参数对Al2O3/(W,Ti)C/CaF2梯度自润滑陶瓷刀具材料残余应力的影响

基于功能梯度材料的设计思想,设计并制造了Al2O3/(W,Ti) C/CaF2梯度自润滑陶瓷刀具材料.利用有限元法计算分析了梯度自润滑陶瓷刀具材料层间热膨胀系数差值、分布指数和弹性模量对其残余应力的影响,并给出了径向应力和Von Mises等效应力的分布图,为梯度自润滑陶瓷刀具的研制开发提供了理论基础.以此为基础,采用真空热压工艺制备了Al2O3/(W,Ti) C/CaF2梯度自润滑陶瓷刀具材料.结果表明:据此制备的梯度自润滑陶瓷刀具材料具有良好的力学性能.     

Y-Ce-ZrO_2-TiC-Al_2O_3复合陶瓷材料的制备及其摩擦磨损特性研究

从提高陶瓷材料的力学性能出发,采用真空热压工艺,制备了混合稀土氧化物稳定的Y-Ce-ZrO2-TiC-Al2O3复合陶瓷材料。对复合陶瓷材料进行了摩擦磨损性能实验研究,采用扫描电镜对其磨损表面形貌进行了观察,对磨损表面物相进行了X射线衍射分析。并与单相ZrO2陶瓷作对比,探讨了复合陶瓷材料的磨损机理。研究表明,该复合陶瓷材料具有较高的综合力学性能,在法向载荷为140 N、转速为200 r/min干摩擦条件下,Y-Ce-ZrO2-TiC-Al2O3复合陶瓷摩擦系数为0.65,磨损率为2.88×10-7mm3/N.m,明显低于单相ZrO2陶瓷,其磨损机理为机械冷焊和粘着磨损。     

Y-Ce-ZrO2-TiC-A12O3复合陶瓷材料的制备及其摩擦磨损特性研究

从提高陶瓷材料的力学性能出发,采用真空热压工艺,制备了混合稀土氧化物稳定的Y-Ce-ZrO2-TiC-A12O3复合陶瓷材料.对复合陶瓷材料进行了摩擦磨损性能实验研究,采用扫描电镜对其磨损表面形貌进行了观察,对磨损表面物相进行了X射线衍射分析.并与单相ZrO2陶瓷作对比,探讨了复合陶瓷材料的磨损机理.研究表明,该复合陶瓷材料具有较高的综合力学性能,在法向载荷为140 N、转速为200 r/m.in干摩擦条件下,Y-Ce-ZrO2-TiC-A12O3复合陶瓷摩擦系数为O.65,磨损率为2.88×10-mm3/N·m,明显低于单相ZrO2陶瓷,其磨损机理为机械冷焊和粘着磨损.     

Y2O3/ZrO2复合泡沫陶瓷烧结的初步研究

本文采用有机泡沫浸渍法制备了Y2O3/ZrO2双层复合、Y2O3/Y2O3-ZrO2/ZrO2三层复合及Y2O3和ZrO2单相泡沫陶瓷,分析了两种复合泡沫陶瓷层间的结合及各层显微结构随烧结温度的变化,并与单相氧化物陶瓷进行了对比。结果表明:双层复合陶瓷层间有较大缝隙,这是因为两种氧化物陶瓷烧结不同步造成的。三层复合陶瓷中Y2O3-ZrO2混合中间层的存在减弱了Y2O3、ZrO2烧结不同步引起的层间应力,层间结合明显改善,并大大减少了泡沫陶瓷表面宏观裂纹。两种复合陶瓷的ZrO2内层的烧结程度都低于单相ZrO2,这主要是因为先于ZrO2烧结的Y2O3外层阻碍了内部气体的排出从而阻碍ZrO2的烧结所致。     

Co包覆Al2O3/TiC复合材料的烧结及性能

采用Co包覆Al2O3/TiC微米级、纳米级粉料进行了不同Co含量、不同烧结温度的热压烧结实验.综合分析和对比了两种不同粒径包覆粉体的烧结结果,结果发现纳米级的粉体烧结效果优于微米级粉体的烧结效果.综合力学性能最佳的纳米级复相陶瓷材料的硬度为HRA92.7,抗弯强度σf为782 Mpa,断裂韧性KIC为7.81 Mpa·M1/2.利用SEM观察采取综合力学性能最佳的ATC纳米复合材料制备工艺制备的Al2O3、Al2O3/TiC和ATC的断口,可以看出Al2O3、Al2O3/TiC主要以沿晶断裂为主,而ATC为沿晶与穿晶混合断口,并从ATC断口,发现形成了晶内型结构,观察到了裂纹曲折的扩展路径以及裂纹的分叉、偏转、桥联这些有助于材料强度和韧性提高的现象.     

Ionic conduction in As2S3---Ag2S, GeS2---GeS---Ag2S and P2S5---Ag2S glasses

The glass-forming region in the system P---S---Ag was determined and density, thermal expansion, dc conductivity and the transport number of Ag ions were measured for P₂S₅---Ag₂S glasses found in the P---S---Ag system. The results for the transport number measurement show that P₂S₅---Ag₂S glasses are purely ionic conductors owing to the Ag ion migration, like most of the As₂S₃---Ag₂S and GeS₂---GeS---Ag₂S glasses reported previously. Glass structure and ionic conduction processes in As₂S₃---Ag₂S, GeS₂---GeS---Ag₂S and P₂S₅---Ag₂S glasses are discussed, based on their ionic conductivity and density data. The structural concept of -Ag₂S was applied to these glasses, which suggests that the Ag ions in the glasses are distributed in the available Ag ion sites in the non-conducting framework composed of both S anions and As, Ge or P cations. In each system the ionic conductivity increases linearly with increasing Ag⁺/total cation (%) in glass composition, the determining factor being the activation energy for ionic conduction alone. Thus, the activation energy in these glasses depends predominantly upon the molar ratio of Ag ions to total cation in the glass, irrespective of the kind of system. Small differences in the activation energy among the three systems can be interpreted as arising from differences in the field strength of As, Ge and P cations.     

Spectroscopic properties of Er-doped Na2O-Sb2O3-B2O3-SiO2 glasses

Spectroscopic properties of Er³⁺-doped Na₂O-Sb₂O₃-B₂O₃-SiO₂ glasses have been investigated for developing 1.5-μm broadband fiber amplifiers. An intense 1.5-μm near infrared emission with a broad full width at half maximum (FWHM) of 88 nm has been obtained for Er³⁺-doped 5Na₂O-20Sb₂O₃-35B₂O₃-40SiO₂ glass upon excitation with a 980 nm laser diode. The obtained emission cross-section of the ⁴I_13/2 → ⁴I_15/2 transition and the lifetime of the ⁴I_13/2 level of Er³⁺ ions are 6.8 × 10⁻²¹ cm² and 0.36 ms, respectively. It is noted that the product of the emission cross-section and the FWHM of the glass, σ_e × FWHM, is as great as 598.4 × 10⁻²¹ cm² nm, which is comparable or higher than that of Er³⁺-doped bismuth-based and tellurite-based glasses. These special optical properties encourage in identifying them as important materials for potential applications in high performance optics and optical communication networks.     

Phase separation and crystallization in the system SiO2-Al2O3-P2O5-B2O3-Na2O glasses

The phase separation and crystallization behavior in the system (80 − X)SiO₂ · X(Al₂O₃ + P₂O₅) · 5B₂O₃ · 15Na₂O (mol%) glasses was investigated. Glasses with X = 20 and 30 phase separated into two phases, one of which is rich in Al₂O₃-P₂O₅-SiO₂ and forms a continuous phase. Glasses containing a larger amount of Al₂O₃-P₂O₅ (X = 40 and 50) readily crystallize and precipitates tridymite type AlPO₄ crystals. It is estimated that the phase separation occurs forming continuous Al₂O₃-P₂O₅-SiO₂ phase at first, and then tridymite type AlPO₄ crystals precipitate and grow in this phase. Highly transparent glass-ceramics comparable to glass can be successfully obtained by controlling heat treatment precisely. The crystal size and percent crystallinity of these transparent glass-ceramics are 20-30 nm and about 50%, respectively.     

Growth of single crystals of NaH2PO4 (NaDP), NaH2PO4 · H2O (NaDP · H2O), and NaH2PO4 · 2H2O (NaDP · 2H2O) sodium dihydrogenphosphate based on the analysis of the Na2O-P2O5-H2O phase diagram

The crystallization conditions for the NaH₂PO₄, NaH₂PO₄ · H₂O, and NaH₂PO₄ · 2H₂O solid phases have been established from the analysis of the phase diagram of solubility of the ternary Na₂O-P₂O₅-H₂O system in the temperature range from 0 to 100°C. Based on these data, the methods for growing sodium dihydrogenphosphate single crystals of the above compositions are developed. The initial components for preparing mother solutions were H₃PO₄ and NaOH solutions taken in certain weight ratios. For the first time, NaDP, NaDP · H₂O, and NaDP · 2H₂O single crystals were grown on a seed by the method of temperature decrease. The habits of the NaDP and NaDP · H₂O single crystals are determined. __________ Translated from Kristallografiya, Vol. 47, No. 5, 2002, pp. 937–944. Original Russian Text Copyright ? 2002 by Soboleva, Voloshin.     

Thermo-optic properties of B2O3 doped Li2O-Al2O3-SiO2 glass-ceramics

Reduction in the temperature coefficient of the optical path length, dS/dT of Li₂O-Al₂O₃-SiO₂ glass-ceramics with near-zero thermal expansion coefficient was attempted using control of the temperature coefficient of electronic polarizability, ?, and the thermal expansion coefficient, α. The dS/dT value of 2.6 mol% B₂O₃-doped glass-ceramic was 12.5  × 10⁻⁶/°C, which was 0.9 ×  10⁻⁶/°C smaller than that of B₂O₃-free glass-ceramic. On the other hand, reduction in dS/dT through B₂O₃ doping was not confirmed in precursor glasses. Results showed that reduction in dS/dT of the glass-ceramic through B₂O₃ doping is caused by the reduction in ?. The reduction in ? from B₂O₃ doping was probably attributable to numerical reduction in non-bridging oxide ions with larger ? value by the concentration of boron ions in the residual glass phase. In addition, application of hydrostatic pressure during crystallization was effective to inhibit precipitation of β-spodumene solid solution, which thereby decreases dS/dT. The dS/dT value of B₂O₃-doped glass-ceramic crystallized under 196 MPa was 11.7 ×  10⁻⁶/°C. That value was slightly larger than that of silica glass. The α value of this glass-ceramic was smaller than that of silica glass.     

Electron diffraction RDF analysis of amorphous As2Se3,AAs2Se2Te,As2SeTe2 and As2Te3 films

The local order in amorphous films of As₂Se₃, As₂Se₂Te, As₂SeTe₂, and As₂Te₃ has been examined by scanning electron diffraction with direct recording of the intensity of the elastically scattered electrons. The radial distribution functions indicate that there is a systematic increase in mean nearest neighbor distance as the Te concentration is increased, butthe mean coordination number increases slightly around 2.4. Pair function calculation of models shows that the 3-aand 2-fold coordinations of arsenic and chalcogens are retained in these glasses and the interatomic distances are close to those predicted from the Pauling covalent atomic radii of the constituent atomic species. The short range order appears to be similar in amorphous and crystalline As₂Se₃, but different in the case of As₂Te₃ as found by previous workers on bulk materials.     

Thin SiO2---TiO2---ZrO2 films from alkoxide solutions

Different solutions containing alkoxides of silicon, titanium, and zirconium have been prepared. Some of their properties like the time dependent viscosity and the gelling time have been measured and are reported here for different H₂O, HCl, ethanol and/or formamide contents. Microscope slides have been dip coated in these solutions. After baking, film thickness and chemical durability have been determined.

In order to get good SiO₂---TiO₂---ZrO₂ glass coatings, the withdrawal speed should not exceed 5 cm/min unless the viscosities of the solutions are reduced by the addition of ethanol. By such a dilution, the film thickness could also be reduced, while the addition of formamide caused a delayed increase of the viscosity and increased gelling times. For this reason, solutions containing formamide can be used for longer periods. The chemical durability of the substrates against boiling NaOH solution is enhanced by the SiO₂---TiO₂---ZrO₂ glass coatings.     

Precipitation of In2O3 nano-crystallites from glasses in the system Na2O/B2O3/Al2O3/In2O3

Glasses in the system Na₂O/B₂O₃/Al₂O₃/In₂O₃ were melted and subsequently tempered in the range from 500 to 700 °C. Depending on the chemical composition, various crystalline phases were observed. From samples without Al₂O₃, In₂O₃ could not be crystallized from homogeneous glasses, because either spontaneous In₂O₃ crystallization occurred during cooling, or other phases such as NaInO₂ were formed during tempering. The addition of alumina, however, controlled the crystallization of In₂O₃. Depending on the crystallization temperature applied, the crystallite sizes were in the range from 13 to 53 nm. The glass matrix can be dissolved by soaking the powdered glass in water. This procedure can be used to prepare nano-crystalline In₂O₃-powders.     

The effect of composition on UV-vis-NIR spectra of iron doped glasses in the systems Na2O/MgO/SiO2 and Na2O/MgO/Al2O3/SiO2

Glasses with the compositions xNa₂O · 10MgO · (90 − x)SiO₂, 10Na₂O · xMgO · (90 − x)SiO₂, 5Na₂O · 15MgO · xAl₂O₃ · (80 − x)SiO₂, xNa₂O · 10MgO · 10Al₂O₃ · (80 − x)SiO₂, 10Na₂O · 10MgO · xAl₂O₃ · (80 − x)SiO₂, 10Na₂O · 5MgO · 10Al₂O₃ · (80 − x)SiO₂ were melted and studied using UV-vis-NIR spectroscopy in the wavenumber range from 5000 to 30 000 cm⁻¹. At [Al₂O₃] > [Na₂O], the UV-cut off is strongly shifted to smaller wavenumbers and the NIR peak at around 10 000 cm⁻¹ attributed to Fe²⁺ in sixfold coordination gets narrower. Furthermore, the intensity of the NIR peak at 5500 cm⁻¹ increases. This is explained by the incorporation of iron in the respective glass structures.     

一种新型紫外非线性光学材料Ba2Be2B2O7

利用高温固相反应合成了一种新的非线性光学材料Ba2Be2B2O7（简称TBO）,利用顶部熔盐籽晶法生长出了可供初步性能测试的TBO晶体,结构分析表明,TBO晶体的基本结构单元与SBBO（Sr2Be2B2O7)相同,并且均含有对非线性光学效应起主要作用的[BO3]基团,TBO的粉末倍频效应大约为KDP（KH2PO4）的2倍,TBO晶体的物理化学性质稳定,不吸潮,硬度适中,并且易于加工。