Study and simulation of the growth of solid lubricant MoSe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> coatings during pulsed laser deposition

The chemical composition and tribological properties of the thin-film diselenide molybdenum coatings deposited by pulsed laser deposition in vacuum and a rarefied inert gas (argon) atmosphere are studied. Upon deposition in a gas at a pressure of ∼2 Pa, stoichiometric coatings with improved antifriction properties as compared vacuum-deposited coatings form. However, a too strong increase in the argon pressure (to ∼10 Pa) degrades the tribological properties of the coating. Structure formation in the MoSe _x coatings grown by pulsed laser deposition on an unheated substrate is investigated. Deposition in vacuum or argon at a pressure of 2 Pa leads to formation of rather smooth coatings with a dense amorphous structure containing molybdenum nanoinclusions. Deposition at a high argon pressure results in a developed surface relief and a loose coating structure. A mathematical model is developed using the kinetic Monte Carlo method in order to describe structure formation in the coatings that grow during physical deposition of an atomic flux. A comparative analysis demonstrates satisfactory agreement between the simulated and experimentally studied structures in the coatings created by pulsed laser deposition at various gas pressures.     

Effect of the pulsed laser deposition conditions on the tribological properties of thin-film nanostructured coatings based on molybdenum diselenide and carbon

The structural state and tribological properties of gradient and composite antifriction coatings produced by pulsed laser codeposition from MoSe₂(Ni) and graphite targets are studied. The coatings are deposited onto steel substrates in vacuum and an inert gas, and an antidrop shield is used to prevent the deposition of micron-size particles from a laser jet onto the coating. The deposition of a laser jet from the graphite target and the application of a negative potential to the substrate ensure additional high-energy atom bombardment of growing coatings. Comparative tribological tests performed at a relative air humidity of ∼50% demonstrate that the “drop-free” deposition of a laser-induced atomic flux in the shield shadow significantly improves the antifriction properties of MoSe _x coatings, decreasing the friction coefficient from 0.07 to 0.04. The best tribological properties, which combine a low friction coefficient and high wear resistance, are detected in drop-free MoSe _x coatings additionally alloyed with carbon (up to ∼55 at %) and subjected to effective bombardment by high-energy atoms during growth. Under these conditions, a dense nanocomposite structure containing the self-lubricating MoSe₂ phase and an amorphous carbon phase with a rather high concentration of diamond bonds forms.     

Formation of the chemical composition of transition metal dichalcogenide thin films at pulsed laser deposition

The formation of the chemical composition of dichalcogenide films at pulsed laser deposition in vacuum and in rarefied gases (Ar, H₂) is investigated with MoSe _x thin-film coatings. It is found that deposition in gases increases the selenium concentration and somewhat flattens the composition over the substrate surface. To elucidate the mechanisms underlying the MoSe _x film formation, a computer model is used that simulates the motion of a pulsed laser-initiated atomic flux through a rarefied gaseous medium. Using this model, the energy and angular parameters of atomic Mo and Se fluxes toward the substrate are calculated. It is shown that the expansion dynamics of laser plume components (Mo and Se) and the selective sputtering of selenium are the main factors governing the formation of the chemical composition and its distribution over the substrate. The influence of the sort of gas on the efficiency of atomic flux slowdown and scattering and on material losses during deposition is considered.     

斜角入射沉积法制备渐变折射率薄膜的折射率分析

斜角入射沉积法是一种制备薄膜的新颖方法,它可以用来制备渐变折射率薄膜.本文首先探讨了膜料的沉积入射角为α,薄膜柱状生长倾斜角为β时的薄膜的填充系数;之后利用drude理论,分析研究了斜角入射沉积法制备渐变折射率薄膜的折射率与薄膜的入射角和生长方向的关系. 关键词： 斜角入射沉积 渐变折射率 填充系数     

Influence of reactive gas and temperature on structural properties of magnetron sputtered CrSiN coatings

CrSiN coatings were deposited on stainless steel (Grade: SA304) and silicon Si(1 0 0) substrates, with varying argon-nitrogen gas proportions and deposition temperature, using reactive magnetron sputtering technique in the present work. The influence of sputtering (Ar) and reactive gas proportions (N₂) and temperature on the structural properties of the CrSiN coating was investigated. A small amount of silicon content (3.67 at.% Si) plays a crucial role in addition to the nitrogen content for the formation of different phases in the CrSiN coatings as observed in the present work. For example, the coating with comparatively low nitrogen content, 40% N₂, during deposition, formed a crystalline structure consisting of nano-crystalline CrN which is separated by an amorphous SiN phase, as evident from X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The formation of CrN(1 1 1) and Cr₂N(1 1 1) phases has occurred at 30% N₂ with 3.67% Si content, which transformed in to CrN(1 1 1) and CrN(2 0 0) with increase in N₂ content but with same Si content. The surface topography and morphology of the coatings were analyzed by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM), respectively. A less columnar growth is observed in CrSiN coatings deposited at low argon content, Ar:N₂ (20:80), and with 3.67 at.% Si in the coatings. However, it becomes dense with increase in nitrogen content and temperature. The XRD analysis showed that the intensity of a dominating peak (1 1 1) is decreasing from (80:20) to (60:40) argon:nitrogen environment. With a further increase of nitrogen content, from (60:40), in the sputtering gas mixture, to (40:60) argon-nitrogen, there is a sudden increase in (1 1 1) peak and above (40:60), the peak reduction rate is very slow than the previous one. The (1 1 1) and (2 0 0) peak intensity variations are very limited due to high nitrogen content, above 50%, and considerable amount of Si atoms, 3.67 at.%, present in the CrN coatings.     

The rate of electroless deposition of a four-component Ni-W-P-ZrO2 composite coating from a glycine bath

Four-component Ni-W-P-ZrO₂ composite coatings were electroless deposited. A bath containing aminoacetic acid as the agent complexing nickel ions, and sodium tungstate(VI) as the source of tungstate was used. It has been determined that as the bath's pH increases (from 5 to 6) so does the rate of coating deposition while the phosphorus content in the coating decreases. Both an increase in the aminoacetic acid concentration and an increase in the sodium tungstate cause a reduction in the rate of deposition of the Ni-W-P-ZrO₂ coating. Changes in the concentration of the two components in the bath result in a change in the composition of the coatings. When the concentration of the components is too high the bath loses its stability and a sediment precipitates itself. The ZrO₂ content in the coating depends most on the amount of this powder in the suspension.     

Ti-B-C-N纳米复合薄膜结构及力学性能研究

利用反应磁控溅射方法在单晶硅和高速钢(W18Cr4V)基片上制备出不同C含量Ti-B-C-N纳米复合薄膜. 使用X射线衍射和高分辨透射电子显微镜研究了Ti-B-C-N纳米复合薄膜的组织和微观结构,用纳米压痕仪测试了它们的硬度和弹性模量. 结果表明,利用往真空室通入C₂H₂气体的方法制备得到的Ti-B-C-N纳米复合薄膜中,在所研究成分范围内只发现TiN基的纳米晶. 当C₂H₂流量较小时,C元素的加入可以促进Ti-B-C 关键词： Ti-B-C-N薄膜 磁控溅射 微观结构 力学性能     

Graded index broadband antireflection coating prepared by glancing angle deposition for a high-power laser system

This paper reports that SiO₂ is selected to fabricate broadband antireflection (AR) coatings on fused silica substrate by using glancing angle deposition and physical vapour deposition. Through accurate control of the graded index of the SiO₂ layer, transmittance of the graded broadband AR coating can achieve an average value of 98% across a spectral range of 300--1850~nm. Moreover, a laser-induced damage threshold measurement of the fabricated AR coating is performed by using a one-on-one protocol according to ISO11254-1, resulting in an average damage threshold of 17.2~J/cm$^{2}$.     

Influence of the bilayer thickness of nanostructured multilayer MoN/CrN coating on its microstructure,hardness, and elemental composition

Multilayer nanostructured coatings consisting of alternating MoN and CrN layers were obtained by vacuum cathode evaporation under various conditions of deposition. The transition from micron sizes of bilayers to the nanometer scale in the coatings under investigation leads to an increase in hardness from 15 to 35.5 GPa (with a layer thickness of about 35 nm). At the same time, when the number of bilayers in the coating decreases, the average Vickers hardness increases from 1267 HV_0.05 to 3307 HV_0.05. An increase in the value of the potential supplied to the substrate from–20 to–150 V leads to the formation of growth textures in coating layers with the [100] axis, and to an increase in the intensity of reflections with increasing bilayer thickness. Elemental analysis carried out with the help of Rutherford backscattering, secondary ion mass spectrometry and energy dispersion spectra showed a good separation of the MoN and CrN layers near the surface of the coatings.     

Optimization of plasma parameters for high rate deposition of titanium nitride films as protective coating on bell-metal by reactive sputtering in cylindrical magnetron device

Nano-structured titanium nitride (TiN) thin film coating is deposited by reactive sputtering in cylindrical magnetron device in argon and nitrogen gas mixtures at low temperature. This method of deposition using DC cylindrical magnetron configuration provides high uniform yield of film coating over large substrate area of different shapes desirous for various technological applications. The influence of nitrogen gas on the properties of TiN thin film as suitable surface protective coating on bell-metal has been studied. Structural morphological study of the deposited thin film carried out by employing X-ray diffraction exhibits a strong (2 0 0) lattice texture corresponding to TiN in single phase. The surface morphology of the film coating is studied using scanning electron microscope and atomic force microscope techniques. The optimized condition for the deposition of good quality TiN film coating is found to be at Ar:N₂ gas partial pressure ratio of 1:1. This coating of TiN serves a dual purpose of providing an anti-corrosive and hard protective layer over the bell-metal surface which is used for various commercial applications. The TiN film's radiant golden colour at proper deposition condition makes it a very suitable candidate for decorative applications.     

Stress, absorptance and laser-induced damage threshold properties of 355-nm HR coatings

A number of 355-nm Al₂O₃/MgF₂ high-reflectance (HR) coatings were prepared by electron-beam evaporation. The influences of the number of coating layers and deposition temperature on the 355-nm Al₂O₃/MgF₂ HR coatings were investigated. The stress was measured by viewing the substrate deformation before and after coating deposition using an optical interferometer. The laser-induced damage threshold (LIDT) of the samples was measured by a 355-nm Nd:YAG laser with a pulse width of 8 ns. Transmittance and reflectance of the samples were measured by a Lambda 900 spectrometer. It was found that absorptance was the main reason to result in a low LIDT of 355-nm Al₂O₃/MgF₂ HR coatings. The stress in Al₂O₃/MgF₂ HR coatings played an unimportant role in the LIDT, although MgF₂ is known to have high tensile stress.     

金属表面碳涂层对激光等离子体辐射的影响

 阐述了激光诱导击穿光谱技术的基本原理,分析了金属材料表面光学性质与激光诱导等离子体辐射强度的关系,建立了空气中进行等离子辐射研究的试验装置,测量了不同厚度碳层下激光等离子体的发射光谱强度。实验结果表明：当一束近红外高能量脉冲激光（能量为5 J）作用于覆盖有约18 μm厚度碳层的标钢样品时,激光等离子体的发射光谱强度提高了16%～22%;证明了金属样品表面覆盖碳层能够提高激光等离子体辐射强度。     

Fabrication of coaxial nanowire heterostructures: SiO x nanowires with conformal TiO2 coatings

Silica nanowires, grown via the active oxidation of a silicon substrate, have been coated with TiO₂ using two coating methods: solution-based deposition of Ti-alkoxides and atomic layer deposition. Analysis of as-deposited and annealed films shows that it is possible to produce stable conformal coatings of either the anatase or rutile phases of TiO₂ on nanowires with diameters greater than 100 nm when annealed between 500–600°C and 800–900°C, respectively, with annealing at higher temperatures (1050°C) producing coatings with a highly facetted rutile morphology. The efficacy of the process is shown to depend on nanowire diameter, with nanowires having diameters less than about 100 nm fusing together during solution-based coating and decomposing during TiO₂ atomic layer deposition. The use of a suitable buffer layer is shown to be an effective means of minimizing nanowire decomposition. Finally, annealing coated nanowires under active oxidation conditions (1100°C) is shown to be an effective technique for depositing additional conformal SiO _x coatings, thereby providing a means of fabricating multi-layered coaxial nanostructures.     

溅射压强对TiN/SiNx纳米多层膜微观结构及力学性能的影响

利用磁控溅射方法在不同溅射压强条件下制备了TiN/SiN_x纳米多层膜.多层膜的微观结构及力学性能分别用X射线衍射仪、原子力显微镜及纳米压痕仪来表征.结果表明随着溅射压强的增大,多层膜的界面变模糊,TiN层的择优取向由(200)晶面过渡到(111)晶面.与此同时,多层膜的表面粗糙度增大,硬度和弹性模量随溅射压强的增大而减小.多层膜力学性能的差异主要是由于薄膜的周期性结构及致密度存在差异所致. 关键词： x多层膜')" href="#">TiN/SiN_x多层膜 界面宽度 表面形貌     

反式二丁烯和氢气流量比对辉光放电聚合物热稳定性能的影响

用低压等离子体化学气相沉积法,以T2B和H2为工作气源,改变T2B与H2的流量比例制备了辉光放电聚合物(GDP)涂层。通过GDP碳氢涂层的傅里叶变换红外吸收光谱讨论了流量比例对其内部结构的影响,利用热重曲线表征了GDP碳氢涂层在50~600℃范围内的热失重情况,并且结合其结构讨论了流量比例变化对GDP碳氢涂层的热稳定性的影响,最后探讨了GDP碳氢涂层可能的热裂解过程。结果表明:随着T2B与H2流量比的增大,GDP碳氢涂层中C(sp2)-Hx/C(sp3)-Hx含量逐渐降低,-CH3含量增加,碳链逐渐变短而支链含量增加,其热稳定性逐渐变差。以T2B与H2流量比为0.04时,可以成功制备出ICF物理实验所需的靶丸烧蚀层。     

退火对AlTiN多层薄膜结构及力学性能影响

使用TiAl合金靶,利用中频反应磁控溅射系统,通过交替改变氮气流量的方法,在高速钢(W18Cr4V)基体上沉积了一组氮含量周期性改变的AlTiN多层薄膜,并分别在600,700和800 ℃下真空退火热处理. 利用X射线衍射仪、场发射扫描电镜和高分辨透射电镜等方法研究了沉积态和退火态AlTiN多层薄膜组织和微观结构;AlTiN多层薄膜的力学和膜基结合性能用纳米压痕硬度仪、摩擦磨损仪以及划痕试验仪得到. 研究表明,采用沉积过程中周期改变氮气流量的方法,可以制备出稳定的、力学性能良好的AlTiN多层薄膜. 80 关键词： AlTiN多层薄膜 退火 微观结构 力学性能     

Influence of substrate hardness transition on built-up of nanostructured WC-12Co by cold spraying

The ability of cold spray process to retain the feedstock microstructure into coating makes it possible to deposit nanostructured WC-Co coatings. In the present study, the deposition behavior of nanostructured WC-12Co coating was examined through the surface morphology and cross-sectional structure of the deposited single WC-12Co particle impacting on the substrates with different hardness using a nanostructured WC-12Co powder. Substrates included stainless steel, nickel-based self-fluxing alloy coatings with different hardness. It was observed from the top surface and cross-section of individual WC-12Co particles that the penetration leading to particle deposition depends on substrate hardness. When the substrate surface is covered by WC-12Co particles, the hardness of the newly formed substrate, i.e. the coating, increases greatly. The significant increase of the surface hardness leads to the rebounding off of impacting particles and erosion of the deposited particles, which prohibits effective built-up of coating. However, it was found that with spray jet fixed, a deposit with a thickness up to over 700 μm can be built-up. A model involving in substrate hardness transition during deposition is proposed to explain such phenomenon, which can be employed to optimize the conditions to build up a uniform nanostructured WC-12Co coating.     

Formation and study of electrospark coatings based on titanium aluminides

Coatings containing Ti-Al intermetallics are fabricated by the electrospark deposition of titanium on aluminum and aluminum on titanium. The microstructure and composition of the grown coatings is studied by scanning electron microscopy, X-ray diffraction, and S-ray microanalysis. It is found that the surface layer formed in argon mostly contains the α-TiAl₃ intermetallic independent of the duration and frequency of discharge pulses. The γ-TiAl and α₂-Ti₃Al phases can be obtained by aluminum deposition on titanium followed by the subsequent deposition of a second titanium layer. Aluminum oxide and titanium nitride are additionally formed during the deposition of electrospark coatings in air.     

Structure of Al2O3 thin layers synthesized on the silicon surface by atomic layer deposition

The distribution of the phase and chemical composition at an Al₂O₃/Si interface is studied by depth-resolved ultrasoft x-ray emission spectroscopy. The interface is formed by atomic layer deposition of Al₂O₃ films of various thicknesses (from several to several nanometers to several hundreds of nanometers) on the Si(100) surface (c-Si) or on a 50-nm-thick SiO₂ buffer layer on Si. L _2,3 bands of Al and Si are used for analysis. It is found that the properties of coatings and Al₂O₃/Si interfaces substantially depend on the thickness of the Al₂O₃ layer, which is explained by the complicated character of the process kinetics. At a small thickness of coatings (up to 10–30 nm), the Al₂O₃ layer contains inclusions of oxidized Si atoms, whose concentration increases as the interface is approached. As the thickness increases, a layer containing inclusions of metallic Al clusters forms. A thin interlayer of Si atoms occurring in an unconventional chemical state is found. When the SiO₂ buffer layer is used (Al₂O₃/SiO₂/Si), the structure of the interface and the coating becomes more perfect. The Al₂O₃ layer does not contain inclusions of metallic aluminum, does not vary with the sample thickness, and has a distinguished boundary with silicon.     

Activation of fullerene coatings on field emitters by potassium atom and ion fluxes

The activation of tip field emitters with a fullerene coating by the atomic and ionic fluxes of potassium is studied. The deposition of atomic potassium decreases characteristic voltage U ₁ generating fixed fieldemission current I by a factor of 3.5–4.0. However, field emitters activated by potassium atoms are rapidly deactivated and the resulting decrease in U ₁ after storage in a vacuum does not exceed 25–30%. A stable approximately twofold decrease in the characteristic voltage can be reached if the fullerene coating is exposed to a potassium ion flux. The enhanced efficiency of emitter activation by a potassium ion flux is explained by the formation of KC ₆₀ endohedral and/or C₆₀ K exohedral molecules in the fullerene coating.