Structural aspects of European and American diesel engine piston deposits

The formation of carbonaceous deposits on upper lands and ring grooves of diesel pistons is believed to be at least partially responsible for excessive cylinder bore wear and loss of oil control in field service. A properly formulated diesel lubricant has, among other performance characteristics, the ability to control piston deposits, thereby improving overall engine performance.     

Tribochemistry of Fluorinated Fluids Hydroxyl Groups on Steel and Aluminum Surfaces

This paper describes products of tribochemical reactions of Z-Dol 2500 and 1H,1H,2H,2H-tetra-fluorooctanol, produced on steel and aluminum surfaces. The fluorooctanol was used as a model compound to study the reactions of hydroxyl groups. Tribochemical reactions were initiated by friction in the steel/steel and steel/Al contacts, using an Optimol SRV (Schwingung Reibung Verschleiβ) reciprocating sliding tester. The products of these reactions, deposited in the wear scars on steel and Al discs, were studied using reflective FTIR spectrometry (microscopy and grazing angle) and X-Ray photoelectron spectroscopy (XPS). Under boundary lubrication conditions on metal surfaces, fluorinated compounds containing hydroxyl groups formed carboxylic and alkoxyl salts. FTIR spectra indicate that Fe and Al carboxylic salts occur mainly in bidentate configuration.     

Additive Mechanism Investigation of Perfluoropolyether Lubricants with a Phosphazene Additive

The tribological characteristics of magnetic thin film media coated with perfluoropolyether (PFPE) lubricants (ZDOL and AM300J) and a phosphazene additive (X-IP) were investigated in this study. The drag test results show that under ambient and hot/wet conditions the media coated with AM300J lubricant have higher retention on the test track than those coated with ZDOL 2000 PFPE lubricant. The phosphazene additive X-IP was observed to strongly anchored to the surface and was not as easily removed as PFPE lubricants alone. The retention characteristics of X-IP are independent of either AM or ZDOL. Secondary Ion Mass Spectroscopy (SIMS) depth profile data and Angle-Resolved X-Ray Photo-electron Spectroscopy (XPS) reveal that X-IP molecules were distributed near the disk surface in the X-IP and PFPE lubricants mixed layer, indicating a strong bonding/adhesion of X-IP to the disk surface. Together with the drag testing data, the authors conclude that the preferential distribution of X-IP close to the disk surface in the mixed layer helps to improve lubricant retention performance at the head-disk interface.     

Effect of Deaeration and Controlled Environments on the Performance of Lubricants

The effect of oxygen in lubricants on the wear of camshaft lobes and followers was investigated under air and either argon or nitrogen environments. The motored valve train wear tester was used as a wear tester. White oil, white oil containing Zinc Dithiophosphate (ZDP), and REO 200 were used as lubricants. Hydroperoxide was used as a contaminant for the tests conducted with REO 200.

The results showed that the wear of camshaft lobes and cam followers decreased after deaeration. The tests conducted under argon showed a further decrease in wear. The specimens tested with white oil and white oil with ZDP were analyzed by Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The operation of abrasive wear and oxidational wear was observed. A decrease in the hydroperoxide number under argon atmospheres was observed.     

The Additive Action of Some Organic Chlorides and Sulfides in the Four-Ball Lubricant Test

When tested by the four-ball extreme-pressure procedure, oil solutions of t-octyl chloride at the 2 percent chlorine level rated approximately equal to oil solutions of di-t-octyl disulfide at the 2 percent sulfur level, and both of these additive blends rated better than n-octyl chloride in oil at the 2 percent chlorine level or di-n-octyl disulfide in oil at the 2 percent sulfur level. n-Octyl chloride and di-n-octyl disulfide in oil at corresponding concentrations of active element were approximately equivalent in additive action. t-Octyl chloride was almost as good at the 1 percent as at the 2 percent chlorine level. Mixtures of di-t-octyl disulfide and t-octyl chloride in oil at the level 1 percent S-1 percent Cl rated approximately twice as well as di-t-octyl disulfide (2 percent S) or t-octyl chloride (2 percent Cl). Some finer points of the action of these additives were investigated by studying time-connected behavior at 50-kg and 100-kg loads. The action of the additives cannot be explained on the basis of their chemical structures only; interactions with the rubbing process in the four-ball machine also must be considered.     

Flyability and Durability Test of Dynamic Fly-Height Sliders at 1-nm Clearance

The requirement of higher storage density in hard disk drives is pushing the head-to-media spacing(HMS) to become ever smaller. Currently, thermal protrusion at the transducer that is realized by the heating element in dynamic fly-height(DFH) sliders can be used to control the HMS by applying controllable electrical power. Thus, just how low the slider can fly stably and reliably using the DFH technology is a major concern for the hard-drive industry. This article describes a test for evaluating the flyability and durability of the head–disk interface(HDI) at desired and ultrasmall clearance using DFH sliders. Through such a test, the HDI flyability and durability at 1-nm clearance were examined using commercial DFH sliders with two specially designed air-bearing surfaces(ABSs). The possibility of stable and durable on-track flying at 1-nm clearance for optimized DFH sliders was demonstrated in an ambient environment.     

激光重熔等离子喷涂复合润滑涂层的组织与性能研究

探索选取不同的激光重熔工艺,对NiCr合金基复合涂层以及ZrO2基复合涂层进行激光重熔处理,对重熔处理前后涂层的硬度、减摩性、耐磨性进行测试对比分析,并通过扫描电镜观察熔覆带形貌,对熔覆层的形成机理,偏聚区的形成作初步探讨。     

Promotion of Anti-Wear Property of Sodium Stearate by Oxygen and Surface Active Agents

The anti-wear properties of a water-based lubricant were studied using a newly designed friction tester which enabled the rubbing with nascent surface under controlled atmospheres. Sodium stearate considerably reduced the wear of steel in oxygen rich atmospheres.

Supplementary adsorption tests were performed to identify the anti-wear film formed on the rubbed surface. Surface analysis by Fourier transform infrared spectroscopy (FTIR) revealed that metal stearate film was heavily formed on the rubbed surface in oxygen rich atmospheres. The measurement of metal elements in the protective film by atomic absorption spectroscopy clarified that the main constituent of the film was iron stearate. These results of adsorption tests could support that iron stearate might prevent the wear of steel in the wear test.

It was observed that a surface active agent prevented the formation of lubricative oxide film, but when used with sodium stearate, it synergistically promoted the anti-wear property of sodium stearate. This was attributed to the fact that the surface active agent improved the permeability of recrystallized sodium stearate to the rubbing area.     

Analysis and Assessment of Agrimonia Pilosa Ledeb from Different Sources Using FT-IR Spectroscopy

To get the IR spectrums of Agrimonia Pilosa Ledeb (APL) from China and Japan areas,and to find out the characters of IR spectrums through the content of different chemical constituents,to provide a fast and effective analysis method monitor the inherent qualities of traditional Chinese medicine-APL.Fourier Transform Infrared Spectroscopy(FT-IR) was applied to detect sample of APL from China and Japan areas.This study showed that the IR spectra of APL from China and Japan areas have their unique IR fingerprint features.The contents of tannin and calcium phosphate in APL from China is different APL from Japan.So FT-IR is a very quick,effective and well repetitive method for monitoring and distinguishing the traditional Chinese medicine.     

Observations on fretting damage transition to cracking; state of the art and preliminary observations

Interrupted fretting fatigue experiments were performed on 7075-T6 aluminum alloy and fretting damage characterized by confocal and scanning electron microscopy. Strain, induced by specimen fatigue, produces a small amplitude oscillatory motion between the fatigue specimen and the fretting pad. A fretting fatigue damage threshold exists in this material. Hundred percent fretting fatigue was defined as the average total cycles to fracture based on specimens 1–5 (both axial and normal forces were applied). Specimens had fretting damage induced at 100%, 80%, 60%, 40%, and 20% of the maximum fretting fatigue cycles to fracture. A positive correlation was not found between the depth of fretting damage and crack formation, but there appeared to be a stronger relationship between the fretting damaged surface areas, proximity of pits and crack nucleation sites.     

EFFECT OF MICROWAVE TREATMENT ON WC INSERTS FOR DRILLING OF GFRP COMPOSITES

Due to excellent properties such as high specific strength, high specific modulus, and corrosion resistance, Glass Fiber Reinforced Plastics (GFRP) find wide applications particularly in the aerospace and automotive industries. In order to fabricate structural components of GFRP to near-nett shape, machining of GFRP composites is necessary. Drilling is the most common machining operation for GFRP composites. The fiber pull-out, cracking of matrix during the entry and exit of drill, rapid tool wear, and hole shrinkage are problems associated with machining of GFRP. The present study attempts an innovative idea of improving the cutting performance of Tungsten carbide (WC) inserts (K-20) by post-sintering using microwave irradiation.     

分析温室气体及CO2碳同位素比值的傅里叶变换红外光谱仪

改进了傅里叶变换红外分析仪（FTIR）的硬件设计以实现温室气体及CO₂碳同位素比值的多组分、高精度、连续自动测量。首先,对FTIR分析仪测量系统进行了设计和理论分析,引入了温度和压力监控系统以及全密封气路干燥系统。然后,讨论了光谱的定量分析过程。最后,设计了标准气体对比测量实验。实验结果表明：分析仪测量CH₄,CO,CO₂和δ¹³CO₂值的标准偏差分别为0.01×10^-6,0.011×10^-6,0.239×10^-6和0.572‰,与常规FTIR测量系统相比,其检测的标准不确定度分别提高了6.3,8.45,10.54和14.73倍,其系统误差分别提高了2.88,1.93,4.67和4.66倍;对比分析仪与同位素质谱仪对δ¹³CO₂值的测量结果,标准偏差分别为0.572‰和0.171‰,二者测量的标准不确定度相近。所设计的温室气体及CO₂碳同位素比值FTIR分析仪能够满足多组分、高精度、连续自动测量的需要。     

Frequency domain image analysis for the characterization of porous products

Many pharmaceutical products are obtained via freeze-drying of liquid solutions to obtain stable long lasting preparations. The freeze-dry process produces porous cakes whose structure strongly depends on the freezing phase, so that monitoring and optimizing this phase can help both reducing the product cost and insuring its constant quality. Nowadays the optimization is usually performed by determining the cake mass transfer coefficient via a costly process in pilot plants, while the quality is assured only by controlling the process conditions. This paper describes an alternative way of approximately estimating the mass transfer coefficient, which is based on the observation of the product structure by a simple electron microscope followed by a frequency domain imaging process. While the process has been designed and characterized specifically for pharmaceutical products, the proposed approach can be used in several other fields where the characteristics of porous material have to be monitored.     

基于小波变换的STM图像处理的研究

根据扫描隧道显微镜(STM)的特点,将小波变换应用于扫描隧道显微镜的降噪、增强及融合方法进行了阐述.对于不同仪器和不同扫描样品的图像,选用不同的小波基函数和分解层数进行分解和重构,结果表明,利用小波变换对扫描隧道显微镜图像进行处理是有效的、可行的,图像质量得到明显提高.     

真伪天麻二维相关红外光谱法的鉴别研究

本文采用红外光谱法并结合二维相关(Two-Dimensional Correlation Spectroscopy)分析技术,对药用天麻和伪品天麻(芭蕉芋)进行了无损快速鉴别研究。天麻和芭蕉芋在外观上很相似,都是成椭圆或扁卵圆形的块茎,皱缩而稍弯曲,并且在一维谱图上差别很细微,而在二维谱图上显示出较大的差别。在800～1500cm~(-1)波段范围内,天麻在同步图上有二个较强的自动峰,分别在1237cm~(-1)和1415cm~(-1)附近,而芭蕉芋有四个较强的自动峰,在1024、1055、1194、1225cm~(-1)附近,1400cm~(-1)处也有相关峰,但是较微弱,二维相关谱可以提高谱图的分辨率,增加谱图的识别能力,可用于药材真伪品的鉴别。该法快速、准确,为客观评价中药材的来源提供了一种新的方法和手段。     

Micro cutting of tungsten carbides with sem direct observation method

This paper describes the micro cutting of wear resistant tungsten carbides using PCD (Poly-Crystalline Diamond) cutting tools in performance with SEM (Scanning Electron Microscope) direct observation method. Turning experiments were also carried out on this alloy (V50) using a PCD cutting tool. One of the purposes of this study is to describe clearly the cutting mechanism of tungsten carbides and the behavior of WC particles in the deformation zone in orthogonal micro cutting. Other purposes are to achieve a systematic understanding of machining characteristics and the effects of machining parameters on cutting force, machined surface and tool wear rates by the outer turning of this alloy carried out using the PCD cutting tool during these various cutting conditions. A summary of the results are as follows : (1) From the SEM direct observation in cutting the tungsten carbide, WC particles are broken and come into contact with the tool edge directly. This causes tool wear in which portions scrape the tool in a strong manner. (2) There are two chip formation types. One is where the shear angle is comparatively small and the crack of the shear plane becomes wide. The other is a type where the shear angle is above 45 degrees and the crack of the shear plane does not widen. These differences are caused by the stress condition which gives rise to the friction at the shear plane. (3) The thrust cutting forces tend to increase more rapidly than the principal forces, as the depth of cut and the cutting speed are increased preferably in the orthogonal micro cutting. (4) The tool wear on the flank face was larger than that on the rake face in the orthogonal micro cutting. (5) Three components of cutting force in the conventional turning experiments were different in balance from ordinary cutting such as the cutting of steel or cast iron. Those expressed a large value of thrust force, principal force, and feed force. (6) From the viewpoint of high efficient cutting found within this research, a proper cutting speed was 15 m/min and a proper feed rate was 0.1 mm/rev. In this case, it was found that the tool life of a PCD tool was limited to a distance of approximately 230 m. (7) When the depth of cut was 0.1 mm, there was no influence of the feed rate on the feed force. The feed force tended to decrease, as the cutting distance was long, because the tool was worn and the tool edge retreated. (8) The main tool wear of a PCD tool in this research was due to the flank wear within the maximum value of V_max being about 260 μ.     

Characterising the surface and interior chemistry of core-shell nanoparticles using scanning transmission electron microscopy

A method for extracting core and shell spectra from core-shell particles with varying core to shell volume fractions is described. The method extracts the information from a single EELS spectrum image of the particle. The distribution of O and N was correctly reproduced for a nanoparticle with a TiN core and Ti-oxide shell. In addition, the O distribution from a nanoparticle with a Cu core and a Cu-oxide shell was obtained, and the extracted Cu L_2,3-core and shell spectra showed the required change in EELS near edge fine structure. The extracted spectra can be used for multiple linear least squares fitting to the raw data in the spectrum image. The effect of certain approximations on numerical accuracy, such as treating the nanoparticle as a perfect sphere, as well as the intrinsic detection limits of the technique have also been explored. The technique is most suitable for qualitative, rather than quantitative, work.     

低截获概率雷达信号检测方法的优化及应用

针对利用循环谱理论检测低截获概率(LPI)雷达信号存在计算量大的问题,提出了一种优化的快速傅里叶变换(FFT)累积算法来更新信号处理设备的软件程序。分析了原软件中信号处理的过程,提出了采用并行流水型结构的优化方法;利用前一个滑动窗口内采样信号的FFT,推导出下一时刻采样信号序列的FFT;通过减少重复采样点,减少计算量。然后,利用循环谱检测中4个象限的循环谱的对称性,减少计算象限数,并采用一维搜索进行峰值检测,从而进一步减少计算量。理论推导显示,改进方法减少了计算复杂度和计算量。最后,利用提出的方法对常用的线性调频(LFM)和二进制相移键控(BPSK)信号进行了分析。结果表明,在相同条件下,利用改进的算法及一维搜索,计算时间可缩短为原算法的1/25左右。另外,算法改进后检测信号的幅度值仅减小了不到10%,不影响后续处理对循环谱参数的估计。     

Tribological evaluation and analysis of the head/disk interface with perfluoropolyether and X1-P phosphazene mixed lubricants

The retention characteristics of magnetic thin film media coated with perfluoropolyether (PFPE) lubricants and a phosphazene additive, X-1P, were investigated in this study. The retention performance was evaluated by a drag test with a waffle head sliding against the disk that was designed to mechanically wear out the lubricant layer. An IR beam was aligned on the test track to directly measure the amount of PFPE lubricants and X-1P left on the media surfaces for determining the retention characteristics of the lubricants. The drag test results show that under ambient and hot/wet conditions the media coated with AM3001 PFPE lubricant have higher retention ratio on the test track than those coated with ZDOL 2000 PFPE lubricant. The phosphazene additive X-1P was observed to strongly anchor on the surface and not easily removed as PFPE lubricants (ZDOL and AM3001). The retention characteristics of X-1P are independent of lube combination, either AM or ZDOL lubricants. It is demonstrated that X1-P exhibits a good antiwear property and excellent retention performance. This revised version was published online in July 2006 with corrections to the Cover Date.     

Adsorption properties of aqueous methylene blue on mesocellular foam silica: Equilibrium,kinetic, isotherm,and thermodynamic characterization

Abstract

Mesocellular foam silica was prepared by a hydrothermal synthesis protocol. The surface and pore structure of mesocellular foam silica were characterized by low temperature nitrogen adsorption isotherms, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared (FT-IR) spectroscopy. The methylene blue was adsorbed by the synthetic mesocellular foam silica; the optimized adsorption conditions were evaluated and the maximum adsorption capacity of methylene blue by mesocellular foam silica was determined to be 215.5?mg g^?1. The kinetics of the adsorption of methylene blue by mesocellular foam silica were in accordance with a quasi-second-order kinetic equation. The results were analyzed by Langmuir and Freundlich adsorption isotherm models. The adsorption of methylene blue on mesocellular foam silica was shown to follow the Freundlich adsorption isotherm model. The Gibbs free energy change during adsorption showed that this process was spontaneous. The enthalpy change in the process was –28.868?J·mol^?1 K^?1, indicating that the adsorption is exothermic. The negative value of entropy –49.296?J·mol^?1 K^-1 shows that the system disorder decreases due to adsorption.