Friction and wear of partially stabilized zirconia: Basic science and practical applications

The potential of modern ceramics as wear-resistant materials is outlined. The crystal chemistry of zirconia is discussed, with particular reference to the micro structure and physical properties of magnesia-partially stabilized zirconia (magnesia-PSZ): it is suggested that these properties make magnesia-PSZ an attractive tribological material. Results of some laboratory studies of the friction and wear of magnesia-PSZ are noted. Predictions are made from the results and the physical properties of magnesia-PSZ as to its potential role as a wear-resistant material. In the context of these predictions, the results of a number of field trials of magnesia-PSZ components in abrasive or corrosive environments are described.     

Wear and fracture toughness of partially stabilized zirconia ceramics under dry friction against steel

The wear of two ceramic materials containing partially stabilized zirconia is studied under unlubricated friction against steel. The first material, with ZrO₂ and 3 mol % Y₂O₃, was obtained by cold isostatic pressing and sintering. The second material, comprising ZrO₂ and 4 mol % Y₂O₃, was fabricated by additional hot isostatic pressing. The samples of both materials were fabricated with high and low values of fracture toughness. The samples with high fracture toughness are found to wear more intensively. This fact can be explained by surface micro-cracking during braking as a result of phase transformations.     

Determination of paper filler Z-distribution by low-vacuum SEM and EDX

Paper, mainly constituted of cellulose fibres, often contains mineral fillers. These fillers increase some of the properties of the paper (whiteness, printability, etc.) and are cheaper than the cellulose fibres. Nevertheless, the fillers reduce the mechanical properties of the sheet. Paper presents an anisotropy corresponding to three main directions. This anisotropy characterises the sheet mechanical properties, structure and filler distribution. Analyses of the cross section of the paper sheet with a low‐vacuum scanning electron microscope with an energy dispersive spectrometer analysis module can show this distribution. The procedure developed consists in analysing discrete profiles to build the mean profile known as filler Z‐distribution for each of the fillers. To develop this method, problems such as determination of the surface points, the number of points to analyse to define a cross section profile and the time required for the test, have been solved. Paper is sensitive to electron irradiation. In order to avoid deterioration of the material and to obtain satisfactory results, the time span for analyses is restricted to 40 s with a 12 kV electron beam accelerating voltage. Monte Carlo simulations are used to determine the diffusion cloud size and thus to determine the number of points that constitute a profile. The samples are gold sputtered and, with the aid of backscattered imaging, the coated surface allows determination of the sample surface points.     

Preparation,characterization, electrical conductivity and dielectric studies of Na2SO4 and V2O5 composite solid electrolytes

Composite solid electrolytes (1 − x) Na₂SO₄–(x) V₂O₅ were prepared and characterized by various techniques such as XRD, FT-IR, DTA and SEM. AC impedance spectroscopy revealed that the contribution of grain is strong enough over the grain boundary. Arrhenius plot of the Na₂SO₄ shows a sharp increase in conductivity at 523 K due to the structural phase transition (phase V → I). Composites show the enhanced ionic conductivity than the pristine Na₂SO₄ over the entire temperature range. The maximum conductivity σ = 0.003 S cm⁻¹ at 773 K with the lowest activation energy of 0.28 eV was observed for the x = 0.4 sample. The enhanced value of dielectric constant and dielectric loss in the case of composites was obtained because of increase of conductivity, resulted from the increase of space charge polarization and charge motion.     

Effects of focused ion beam milling on electron backscatter diffraction patterns in strontium titanate and stabilized zirconia

This study investigates the effect of focused ion beam (FIB) current and accelerating voltage on electron backscatter diffraction pattern quality of yttria-stabilized zirconia (YSZ) and Nb-doped strontium titanate (STN) to optimize data quality and acquisition time for 3D-EBSD experiments by FIB serial sectioning. Band contrast and band slope were used to describe the pattern quality. The FIB probe currents investigated ranged from 100 to 5000 pA and the accelerating voltage was either 30 or 5 kV. The results show that 30 kV FIB milling induced a significant reduction of the pattern quality of STN samples compared to a mechanically polished surface but yielded a high pattern quality on YSZ. The difference between STN and YSZ pattern quality is thought to be caused by difference in the degree of ion damage as their backscatter coefficients and ion penetration depths are virtually identical. Reducing the FIB probe current from 5000 to 100 pA improved the pattern quality by 20% for STN but only showed a marginal improvement for YSZ. On STN, a conductive coating can help to improve the pattern quality and 5 kV polishing can lead to a 100% improvement of the pattern quality relatively to 30 kV FIB milling. For 3D-EBSD experiments of a material such as STN, it is recommended to combine a high kV FIB milling and low kV polishing for each slice in order to optimize the data quality and acquisition time.     

SEM‐EDX and microftir studies on evaluation of protection capacity of some thin phosphate layers

This article presents the SEM‐EDX and microFTIR study and the corrosion behavior of new five types of phosphated coatings obtained by coprecipitation in acid aqueous medium of some metal cations, pursuing the influence of the addition of other cations and a moderator of precipitation, on the uniformity and compactness of the layers and on the morphology of dendritic structure of Zn(II) and Fe(II) phosphates. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

Inorganic composition and filler particles morphology of conventional and self-adhesive resin cements by SEM/EDX

The purpose of this study was to characterize the inorganic components and morphology of filler particles of conventional and self‐adhesive, dual‐curing, resin luting cements. The main components were identified by energy dispersive X‐ray spectroscopy microanalysis (EDX), and filler particles were morphologically analyzed by scanning electron microscopy (SEM). Four resin cements were used in this study: two conventional resin cements (RelyX ARC/3M ESPE and Clearfil Esthetic Cement/Kuraray Medical) and two self‐adhesive resin cements (RelyX Unicem/3M ESPE and Clearfil SA Luting/Kuraray Medical). The materials (n = 5) were manipulated according to manufacturers' instructions, immersed in organic solvents to eliminate the organic phase and observed under SEM/EDX. Although EDX measurements showed high amount of silicon for all cements, differences in elemental composition of materials tested were identified. RelyX ARC showed spherical and irregular particles, whereas other cements presented only irregular filler shape. In general, self‐adhesive cements contained higher filler size than conventional resin luting cements. The differences in inorganic components and filler particles were observed between categories of luting material and among them. All resin cements contain silicon, however, other components varied among them. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

EDX measurements and SEM examination of surface of some imported woods inoculated by three mold fungi

Wood samples of Pinus rigida, Juglans nigra, and Fagus sylvatica were superficially inoculated with three mold fungi (Penicillium selerotigenum, Paecilomyces variotii, and Aspergillus niger). The changes in wood surfaces and the elemental composition were observed by scan electron microscope (SEM) and the electron dispersive X-ray spectroscopy (EDX), respectively. Wood elemental composition was an indication of the growth of mold fungi, in which P. selerotigenum, and A. niger have consumed high amount of carbon (C) of F. sylvatica wood compared to control treatment. Also, P. selerotigenum consumed high amount of C of J. nigra wood compared to the control. While, the three mold fungi showed little changes in C content in P. rigida wood. The nitrogen element in the studied woods was completely consumed by the three mold fungi. Cl element increased in the three woods as inoculated by the three fungi compared to untreated woods. Other elements such as S, Si, Ca, Zn, Cu, and Fe varied in their content in accordance to the interaction among wood species and fungi. The growth of the three mold fungi showed distribution and structures of spores and hyphae covering deteriorated wood surfaces. The study suggests that the three mold fungi metabolize the carbon-rich constituents of the investigated wood species in a proportional manner and produce large fruiting structures that release vast numbers of spores in nature.     

Characterization and solid particle erosion behavior of plasma sprayed alumina and calcia-stabilized zirconia coatings on Al-6061 substrate

Repeated impact by solid particles causes erosion and degradation of engineering components. In internal combustion engines, during combustion, hot gases are generated in large quantity which causes erosion of cylinder, combustion chamber, exhaust system, etc. In this work, two types of plasma sprayed coating systems were developed on Al-6061 substrate. For each system, a systematic microstructural study was carried out to understand changes occurred after spraying. Mechanical properties like density, adhesion strength and hardness of coatings were determined. A solid particle erosion test was conducted on coating systems according to ASTM G-76-02 and results were correlated with the microstructural and subsequent mechanical property change. It was observed that volume erosion is more at 45° angle of impact and shows that behavior is in between ductile and brittle. This work also discusses the mechanism involved in erosion wear of plasma sprayed coating systems.     

分光光度法（硫脲还原法）测定矿石及冶金渣中钼含量

M o5＋与硫氰化物作用,生成红色的络合物,颜色深浅与M o5＋含量呈线性正相关,借此进行钼的比色测定。Cu2＋和Fe3＋同时存在,对钼的硫氰化物生成有催化作用。此时,Cu2＋与硫脲生成无色络合物,Fe3＋在Cu2＋的催化下,被硫脲还原为Fe2＋,Fe3＋和Cu2＋对钼的红色络合物无干扰。方法用于矿石和冶金废渣样品分析,测定值的相对标准偏差（n＝6）在0.19％～8.6％之间,回收率在95％～105％之间。实验结果表明该方法具有灵敏度高、定性和定量准确等特点,解决了 Fe3＋和 Cu2＋在分析比色时干扰问题。此方法的原理为2M oO42－＋2CS （NH2）2＋10CNS－＋10H＋＝2[MoO（CNS）5]2 －＋2CS（N2 H3）＋6H2 O     

Yield locus studies of oriented polycarbonate An anisotropic and pressure-dependent solid

Uniaxial and biaxial stress states were employed so as to investigate the yield behavior of oriented polycarbonate. These experimental results are compared with a theoretical yield locus based upon a yield criterion proposed for solids that are both anisotropic and pressure dependent in regard to macroscopic yield behavior. A good correlation between theory and experiment was found.     

High-pressure x-ray diffraction studies on the structure of liquid silicate using a Paris-Edinburgh type large volume press

An experimental setup for high-pressure liquid structure studies with synchrotron x-ray diffraction using the Paris-Edinburgh press has been installed at station 16-BM-B (HPCAT) of the Advanced Photon Source, Argonne National Laboratory. By collecting energy-dispersive data with a synchrotron white beam at various 2θ angles, the present device allows us to obtain the structure factor, S(Q), over a wide range of Q ( = 4πsinθ∕λ) owing to the excellent angular accessibility up to 37° in 2θ and high energy photons well beyond 100 keV. We have successfully collected XRD data on silicate (albite, NaAlSi(3)O(8)) liquids with Q up to ～22 A?(-1) and pressure up to 5.3 GPa and temperature 1873 K, and obtained the radial distribution function, G(r), with a reasonable resolution. The T-O bond length (where T = Al, Si), which is a fundamental measure of local structure for aluminous silicate consisting of SiO(n) and AlO(n) polyhedra (tetrahedra at 1 atm condition), was found to be slightly shortened to 1.626 A? compared to that of glass at 1 atm. The T-O-T bound angle, which is the linkage of the above polyhedra, is the most responsible for densification. The T-O-T peak in G(r) splits into two peaks, suggesting a differentiation of the bond angle at high-pressure. The present technical development demonstrates that the Paris-Edinburgh press is suitable for studies of silicate liquids under high-pressure conditions.     

火焰原子吸收法测定硅酸盐材料中的钙和镁

本文采用氢氧化钠熔融硅酸盐样品,通过加入适当的干扰释放剂,用原子吸收法测定了硅酸盐样品中钙、镁的含量,方法具有操作简单快速和较高的精密度和准确度。     

A theoretical study of the determination of the depth of a dislocation by combined use of EBIC and CL technique

We propose a method for the determination of the depth of a macroscopical lattice defect, e.g., a dislocation, in a semiconductor diode using EBIC and CL contrast measurements from the same defect. The method requires restrictions neither with respect to the value of the bulk diffusion length nor with respect to the shape of the generation region of electron-hole pairs.     

Further studies of the oblique impact of a hard sphere against a ductile solid

The impact of hardened steel spheres against ductile mild steel targets has been studied both theoretically and experimentally. It is shown that a relatively simple computer model based on the assumptions that the sphere is rigid and the target an ideal rigid-plastic solid provides a surprisingly successful explanation of the observed variation of crater volume and projectile energy loss with impact angle and velocity. This model also explains satisfactorily the measured rebound velocity for oblique impact, but cannot account for the finite rebound velocity observed under normal impact conditions. Rebound angles also are under-estimated.     

基于伺服控制的焊管内保护气托与熔池同步系统

介绍了在不锈钢焊管生产中,需要在工件背面进行充氩保护,使用背保护气托是一种经济有效的方法。背保护气托需要与熔池同步移动,针对同步的要求,提出了一种利用伺服电机实现该同步的方法,该方法简单易行,工作可靠,同步效果良好。