Tribological Behaviors of W/Mo Films under Lubrication of Zinc Dithiophosphates—Understanding Their Roles in Tribochemical Reactions

Surface treatment is an effective factor in determining tribological performance, particularly for the condition of oil lubrication. Tungsten (W), molybdenum (Mo), and tungsten–molybdenum alloy (W-Mo) films were prepared on AISI 316L steel by ion beam–assisted deposition (IBAD). Tribological tests of the three modified surfaces using zinc dithiophosphate (ZDDP) lubrication were conducted on an SRV-2 tester and the tribochemical properties of different surfaces were analyzed. Surface analysis tools such as scanning electron microscopy (SEM), X-ray diffractometry (XRD), nano-indentation, and X-ray photoelectron spectroscopy (XPS) were used to study the microstructure, hardness, and chemical characteristics of the tribofilms generated on the worn surfaces. The results showed that these three modified films had better antiwear and antifriction properties than the AISI 316L substrate using both poly-α-olefin (PAO) and ZDDP-containing PAO lubrication, and they had different tribochemical reactions with ZDDP that determined their tribological behaviors.     

The Effect of Steel Hardness on the Performance of ZDDP Antiwear Films: A Multi-Technique Approach

X-ray absorption near-edge structure (XANES) analysis has been used to characterize the chemistry of antiwear films formed in a mineral base oil containing a zinc dialkyl dithiophosphate (ZDDP) additive. These films were formed by rubbing the AISI 1095 steel samples under a reciprocating boundary contact. The steel samples were tempered to produce different Vickers hardness values. The phosphorus L-edge XANES spectra show that these films differ slightly in their chemical nature, with longer chain polyphosphates being formed on samples with higher hardness value. The surface morphology of the films was investigated using Atomic force microscopy (AFM) and the film thickness was probed by Focussed ion beam and Scanning electron microscopy (FIB/SEM) techniques. Furthermore, the nanomechanical properties of these antiwear films were investigated by nanoindentation methods. Tribological measurements of the coefficient of friction (μ) and wear scar width (WSW) indicate that the poorest antiwear film was formed on the softest substrate, which exhibited the largest WSW and the highest average μ. FIB/SEM images show that the thicknesses of the antiwear pads and the degree of damage on the substrates both change with the hardness value of the samples.     

Studies on ZDDP Thermal Film Formation by XANES Spectroscopy, Atomic Force Microscopy, FIB/SEM and 31P NMR

X-ray absorption near edge structure (XANES) spectroscopy has been used to characterize the chemistry of thermal films on steel samples, which were generated from a mineral base oil containing a zinc dialkyl dithiophosphate (ZDDP) additive. These films were formed at 150 °C by immersing steel coupons in ZDDP oil solutions. The phosphorus L-edge XANES spectra show that these films are composed of polyphosphates, unreacted ZDDP and other thiophosphate intermediates. Phosphorus K-edge FY XANES was used to monitor the thickness of these films, and the data are consistent with thickness derived by focussed ion beam (FIB) milling and SEM imaging. The sulphur K-edge TEY and FY XANES spectra show that these films are composed of different sulphur components, which depend upon the formation times. The surface morphology of these films was investigated using atomic force microscopy (AFM). These images show that the surface morphology of the thermal films changes with the formation time. 31P NMR spectra show that both primary and secondary ZDDP decomposes gradually at 150 °C.     

Studies on ZDDP Anti-Wear Films Formed Under Different Conditions by XANES Spectroscopy,Atomic Force Microscopy and 31P NMR

Antiwear (AW) films, generated from a mineral base oil containing a zinc dialkyl dithiophosphate (ZDDP) additive, were studied as a function of formation temperature, load and rubbing time. The surface morphology of these films was investigated using atomic force microscopy (AFM), and surface roughness calculated for the observed differing surface morphologies. The morphology of the films is heterogeneous for all the tested conditions, but the surface roughness is dependent on the rubbing condition. X-ray absorption near edge structure (XANES) spectroscopy has been used to characterize the chemistry of these films, and the intensity of the phosphorus K-edge was also used to monitor their thickness. The thickness of these films is in the range of 10–90 nm depending on the running conditions. Phosphorus L-edge spectra show that these films have a similar chemical nature with variable polyphosphate chain-lengths. 31P NMR was used to study the decomposition of ZDDP in the residual oils. The spectra show that the primary and secondary ZDDP react differently under the various conditions. The tribological characteristics of these AW films were probed by measuring the coefficients of friction (μ) and the wear scar width (WSW) of the counter faces. μ is highly related to the applied load and the results of WSW measurements show that the wear performance is related to all the tested parameters, temperature, load and rubbing time.     

X-Ray Absorption Spectroscopy and Morphology Study on Antiwear Films Derived from ZDDP Under Different Sliding Frequencies

X-ray absorption near-edge structure (XANES) spectroscopy has been used to characterize the chemistry of antiwear (AW) films generated from mineral base oil containing a zinc dialkyl dithiophosphate additive. These films were formed on rubbed steel surfaces with a reciprocating boundary contact using different sliding frequencies. The phosphorus L-edge XANES spectra show that these films have slightly different chemical natures. Longer chain polyphosphates were present on the steel surface prepared at the higher sliding frequencies. The surface morphology of these films was investigated using atomic force microscopy. These images show that the surface morphology of the AW films changes with the sliding frequency. Round and bigger antiwear pads were formed at a lower frequency while higher frequencies resulted in thinner films and flattened surfaces. Nanomechanical properties of these antiwear films were investigated by nanoindentation measurement and the elastic moduli extracted from force–displacement (f–d) curves are similar for all antiwear films, 100 ± 10 GPa.     

Rippling on Wear Scar Surfaces of Nanocrystalline Diamond Films After Reciprocating Sliding Against Ceramic Balls

The formation of nanoscopic ripple patterns on top of material surfaces has been reported for different materials and processes, such as sliding against polymers, high-force scanning in atomic force microscopy (AFM), and surface treatment by ion beam sputtering. In this work, we show that such periodic ripples can also be obtained in prolonged reciprocating sliding against nanocrystalline diamond (NCD) films. NCD films with a thickness of 0.8 µm were grown on top of silicon wafer substrates by hot-filament chemical vapor deposition using a mixture of methane and hydrogen. The chemical structure, surface morphology, and surface wear were characterized by Raman spectroscopy, scanning electron microscopy (SEM), and AFM. The tribological properties of the NCD films were evaluated by reciprocating sliding tests against Al₂O₃, Si₃N₄, and ZrO₂ counter balls. Independent of the counter body material, clear ripple patterns with typical heights of about 30 nm induced during the sliding test are observed by means of AFM and SEM on the NCD wear scar surfaces. Although the underlying mechanisms of ripple formation are not yet fully understood, these surface corrugations could be attributed to the different wear phenomena, including a stress-induced micro-fracture and plastic deformation, a surface smoothening, and a surface rehybridization from diamond bonding to an sp ² configuration. The similarity between ripples observed in the present study and ripples reported after repeated AFM tip scanning indicates that ripple formation is a rather universal phenomenon occurring in moving tribological contacts of different materials.     

Fabrication of porous nanostructured TiO2 particles by an aerosol templating method

An aerosol templating method was applied to fabricate the spherical nanostructured TiO(2) particles containing both mesopores and macropores using two kinds of colloidal mixture such as polystyrene latex (PSL) particles and TiO(2) nanoparticles (P25), and PSL and a titanium hydroxybislactato (TC315). As the weight ratio of PSL/P25 increased from 0 to 1.30, morphology of the as-prepared particles changed from mesoporous particles to particles containing mesopores and macropores. As the furnace temperature decreased from 800 to 600 degrees C at the fixed process conditions, the increase of mesopore volume and specific surface area were determined. The TiO(2) particles fabricated from a mixture of TC315 and PSL were composed of lots of mesopores and a few macropores. The width of UV-absorption spectra of the porous particles synthesized from two colloidal mixtures decreased a little with respect to the increase of the weight ratio. The complete decomposition of p-xylene of 97.9ppm was accomplished within 2h under the illumination of UV-light by all the porous particles.     

Morphology and amine accessibility of (3-aminopropyl) triethoxysilane films on glass surfaces

3-Aminopropyl) triethoxysilane (APTES) is commonly used to functionalize glass substrates because it can form an amine-reactive film that is tightly attached to the surface. In this study, we investigated the morphology and chemical reactivity of APTES films prepared on glass substrates using common deposition techniques. Films were prepared using concentrated vapor-phase deposition, dilute vapor-phase deposition, anhydrous organic-phase deposition and aqueous-phase deposition. All films were annealed, or cured, at 150 degrees C. The morphology of the films was quantified by fluorescence and by atomic force microscopy (AFM). The optical equivalent of the AFM images was computed and then used to directly compare optical and AFM images. Reactive amine density was determined by a picric acid assay and by a method that employed N-succinimidyl 3-[2-pyridyldithio]-propionamido (SPDP) cross-linked rhodamine. Fluorescence and AFM images showed that silane films prepared from dilute vapor-phase and aqueous-phase deposition were more uniform and had fewer domains than those deposited by the other methods. The ratio of picric acid-accessible amino groups to SPDP cross-linked rhodamine-accessible groups varied with the preparation method, suggesting reactant size-dependent difference in amine accessibility. We found a larger number of accessible amino groups on films prepared by vapor-phase deposition than on those prepared from solution deposition. The dilute vapor-phase deposition technique produced relatively few domains, and it should be a good choice for bioconjugation applications. There were appreciable differences in the films produced by each method. We suggest that these differences originate from differences in film rearrangement during annealing.     

常压下用金属有机化学气相沉积法在HP40钢表面制备纳米氧化铝薄膜及表征

常压下用金属有机化学气相沉积法(MOCVD),以仲丁醇铝(ATSB)为前驱体、氮气为载气在HP40钢表面制备了纳米氧化铝薄膜;用光学显微镜、扫描电子显微镜及能谱仪、X射线衍射仪、原子力显微镜等研究了沉积温度等参数对氧化铝薄膜沉积速率的影响,并对其形貌进行了观察。结果表明:随着沉积温度从503K升高到713K,薄膜沉积速率从0.1mg·cm~(-2)·h~(-1)增加到0.82mg·cm~(-2)·h~(-1);当沉积温度在593～653K范围内,可获得晶粒尺寸为10～15nm的纳米氧化铝薄膜;反应的表观活化能随氮气与ATSB蒸气混合气流速增加而降低,不同的混合气流速有不同的反应级数,ATSB的反应级为0.7±0.02。     

Sol-gel Derived TiO2-Bioactive glass-Hydroxyapatite Bioactive Coating on Titanium Alloy Substrate

Coating the hydroxyapatite (HA) on the titanium alloy surface can obtain a bioactive implant with high mechanical properties.However,the bonding force between the titanium alloy and the HA was low due to their different coefficient of thermal expansion (CET).Preparing the multi-layer coating with alleviated thermal stress on titanium alloy substrate is few reported.Fabrication of a TiO2-bioactive glass (BG)-HA bioaetive coating was proposed to solve this problem.A particular TiO2 surface was prepared on the titanium alloy substrate by micro-arc oxidation treatment.The BG and HA coating were coated onto the TiO2 surface in turn by using a sol-gel method.The microstructure,surface morphology and phase composition of the coatings were analyzed.The bonding force of coatings was investigated by the nick apparatus.In vitro dissolution was performed by soaking the TiO2-BG-HA coated samples into the simulated body fluid for various periods.Micro-structural observations indicated that no delamination and crack occurred at the interface of HA/BG and BG/TiO2.The bonding between the substrate and coating consists of the mechanical interaction and the chemical bonding.The bonding force could reach about 45 N.The TiO2-BG-HA coating displayed the excellent forming ability of bone-like apatite when it was soaked into the simulated body fluid.This work suggests an innovative way to reduce the internal stress among coatings through varying BG composition to adjust its CTE,so as to enhance the bonding force.     

Fractal features and surface micromorphology of diamond nanocrystals

This paper analyses the three‐dimensional (3‐D) surface texture of growing diamond nanocrystals on Au thin films as catalyst on p‐type Si substrate using hot filament chemical vapour deposition (HFCVD). Rutherford backscattering spectrometry (RBS), atomic force microscopy (AFM), Raman, X‐ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were applied also to characterize the 3‐D surface texture data in connection with the statistical, and fractal analyses. This type of 3‐D morphology allows a deeper understanding of structure/property relationships and surface defects in prepared samples. Our results indicate a promising way for preparing high‐quality diamond nanocrystals on Au thin films as catalyst on p‐type Si substrate via HFCVD method.     

Friction property study of the surface of ZDDP and MoDTC antiwear additive films using AFM/LFM and force curve methods

The friction properties and material differences of the surface of ZDDP and MoDTC antiwear additive films, which give clear evidence of different friction coefficients in a pin-on-disc test, have been studied using atomic force microscopy (AFM)/lateral force microscopy (LFM) and force curve methods. The AFM/LFM observations show that the friction force on the surface of MoDTC additive films over the sliding area of a steel disc is lower and the friction force of ZDDP additive films is higher than that of afilmless area. Lateral force scope-trace evaluations reveal that the ratio of the friction forces on the surface of the ZDDP film, the filmless area, and the MoDTC film under the same normal force is approximately 1.5:1.0:0.7. Force curve measurements indicate that the surface materials of the ZDDP film, thefilmless area, and the MoDTC film differ according to their attractive forces, that is 29 nN for the ZDDP film, 22 nN for the filmless area, and 12 nN for the MoDTC film. These results correspond to the friction behaviour in the pin-on-disc test and also agree with the idea of the formation of solid MoS₂ lubricant from MoDTC additives on the surface of the antiwear film.     

Multifractal analysis of Mg-doped ZnO thin films deposited by sol–gel spin coating method

A multifractal analysis has been performed on the 3D (three-dimensional) surface microtexture of magnesium-doped zinc oxide (ZnO:Mg) thin films with doping concentration of 0, 2, 4, and 5%. Thin films were deposited onto the glass substrates via the sol–gel spin coating method. The effect of magnesium doping, on the crystal structure, morphology, and band gap for ZnO:Mg thin films has been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV–Vis spectroscopy. It has been observed that the surface of ZnO thin films is multifractal in nature. However, multifractality and complexity observed to decrease with increasing content of Mg in ZnO thin films due to formation of islands on the surface in accordance with Volmer–Weber growth mechanism. The investigations revealed that crystallinity, microtexture, morphology, and optical properties of the thin films can be tuned by controlling the Mg content within the ZnO lattice. In particular, their optical band gap energies were 3.27, 3.31, 3.34, and 3.33 eV at 0, 2, 4, and 5%, respectively. The prepared thin films of ZnO:Mg with tuned characteristics would have promising applications in optoelectronic devices.     

FIB/SEM characterization of carbon-based fibers

The aim of this paper is to show how a focused ion beam combined with a scanning electron microscope (FIB/SEM machine) can be adopted to characterize composite fibers with different electrical behavior and to gain information about their production and modification. This comparative morphology investigation is carried out on polyacrylonitrile (PAN) carbon fibers and their chemical precursor (the oxidized PAN or oxypan) which has different electrical properties. Fibers are imaged by electron and ion beams and sectioned by the focused ion beam (FIB). A sample of oxypan fibers processed by a radio frequency (RF) plasma is also investigated and the role of the conductive carbon layer around their unmodified, insulating bulk is discussed. A suitable developed edge detection technique (EDT) on electron, ion images, and after the FIB sectioning, provides quantitative information about the thickness of the created layer.     

烧结制度对稀土掺杂TiO2光催化抗菌材料抗菌性能的影响

采用溶胶-凝胶法并结合旋转涂膜法制备了稀土掺杂（Ce、Pr、Gd、Dy、Y、Eu）薄膜型光催化抗菌材料，利用TG—DSC综合热分析仪研究了烧结方式、烧结温度以及烧结时间等烧结制度对稀土掺杂TiO2光催化抗菌材料抗菌性能的影响。结果表明，各因素对材料的光催化抗菌性能均存在一最佳值，稀土元素掺杂对TiO2的晶型结构产生了一定的影响；薄膜中除Ce掺杂TiO2薄膜含有极少量金红石型TiO2外，其余全部由单一锐钛矿型TiO2构成，相比稀土掺杂TiO2薄膜对大肠杆菌的杀菌率可达93．38％，较纯TiO2（杀菌率为37．14％）杀菌效果提高了60．23％。该材料经反复使用仍具有很高的杀菌率和稳定性，极具实用价值和应用前景。     

Fe2O3—TiO2薄膜表面Au修饰对CO敏感特性的影响

以Fe(CO)_6和TiCl_4为原料,用PECVD技术制备了Fe_2O_3-TiO_2双层超微粒薄膜.对双层薄膜的组成和形貌进行了XRD及SEM分析.同时对双层薄膜以化学镀方式进行贵金属Au的表面修饰,并对薄膜样品进行气敏特性测试,发现对CO具有很高的灵敏度与选择性.     

Morphologic and cathodoluminescence studies of diamond films by scanning electron microscopy

Using recent papers on scanning electron microscopy (SEM) of chemical vapor deposition (CVD) diamond films, two analytical applications of the SEM are discussed: the morphologic investigations (secondary electron emission mode) and the recognition of impurities and defects [cathodoluminescence (CL) mode]. Studies of CVD diamond films by SEM demonstrate that the morphologies of these films are affected by synthesis conditions, especially by substrate temperature, methane concentration, and total pressure in the reactor. CL spectra and images are useful tools for clarifying the relationship between emission centers and different types of defects generated during the process of diamond crystal growth. The paper shows that the investigations of the morphology, crystallinity, local CL emission, as well as the surface distribution of CL spectra on CVD diamond films by SEM led to the correlative information for quality estimation of films in comparison with natural diamond.     

Measurement on the structural,morphological, electrical and optical properties of PANI-CSA nanofilms

Camphorsulfonic acid doped polyaniline (PANI-CSA) prepared by chemical oxidative polymerization is spin coated on glass plates with four different PANI:CSA weight ratios (1:1, 1:2, 1:4 and 1:8) and measurements on the structural and optical properties are done. Thickness of the films measured <100 nm are termed as nanofilms. Fourier transform infrared spectroscopy indicated the presence of dopant and an increase in degree of polymerization with increase in dopant ratio. X-ray diffraction studies revealed the change of amorphous nature of the film to crystalline nature with increase in CSA dopant ratio. Scanning electron microscopy showed the change of very smooth morphology of the film to rough root-like morphology with increase in CSA dopant ratio. Hall-effect analysis showed that the increase in CSA weight ratio appreciably increases the conductivity of PANI-CSA films due to increase in carrier concentration and it also represents the semiconductivity (P-type) nature in all the films. UV–visible absorption studies reveal the broadening of absorption spectrum in visible region with maximum CSA dopant ratio (1:8). Photoluminescence spectra of PANI-CSA films excited using 300 nm, revealed that the change in intensity and position of emission peaks are due to transition of semiconducting nature of the film to conducting nature with an increase in CSA dopant ratio from 1:1 to 1:8.     

Vacuum insulation of the high energy negative ion source for fusion application

Vacuum insulation on a large size negative ion accelerator with multiple extraction apertures and acceleration grids for fusion application was experimentally examined and designed. In the experiment, vacuum insulation characteristics were investigated in the JT-60 negative ion source with >1000 apertures on the grid with the surface area of ～2 m(2). The sustainable voltages varied with a square root of the gap lengths between the grids, and decreased with number of the apertures and with the surface area of the grids. Based on the obtained results, the JT-60SA (super advanced) negative ion source is designed to produce 22 A, 500 keV D(-) ion beams for 100 s.     

纳米TiO2/ATP复合光催化剂的合成及其表征

以凹凸棒石黏土（Attapulgite，缩写为ATP）为载体，通过酸性溶胶法制备纳米Tio2／ATP前驱体，再经过高温煅烧得到其复合体。利用X射线衍射（XRD）、扫描电镜（SEM）、差热（DTA-TG）手段对其组成、尺寸、结构等进行分析和表征。结果表明，该复合光催化剂中的纳米TiO2在凹凸棒石黏土表面分布均匀，TiO2纳米颗粒间不发生团聚，TiO2粒径比相同工艺获得的纯TiO2小。