Effects of Ag layers on the microstructure and magnetic properties of CoPt/BN multilayer films

Ag/[BN/CoPt]5/Ag and [BN/Ag/CoPt]5/Ag thin films were deposited on glass substrates by magnetron sputtering and then annealed in vacuum at 600 ℃ for 30 min.The structures and magnetic properties of CoPt/BN multilayer films were investigated as a function of Ag layer thickness.It was found that the face-centered tetragonal (fct) (001) texture of CoPt was improved greatly by introducing the Ag toplayer or sublayer together with an Ag underlayer.Good (001)-oriented growth,low intergrain interactions as well as...     

Properties of nanostructured cubic boron nitride films prepared by the short-pulse laser plasma deposition techniques

Nanostructured cubic boron nitride (BN) films were synthesized on molybdenum substrates by using the short-pulse laser plasma deposition techniques. The surface morphologies, chemical compositions, bond structures, and mechanical properties of the obtained BN thin films have been investigated by scanning electron microscopy, Raman scattering, Fourier transform infrared spectroscopy (FTIR), energy dispersive spectra, and hardness measurements. High power density laser deposition yielded boron-rich BN nanorod arrays where tBN component dominates. Reducing power density down to 8 × 10⁷ W/cm² during laser plasma deposition produced flat cBN thin films. Typical TO and LO bands in the Raman and FTIR spectra of the cBN samples were identified. The cBN sample with hardness up to 40 GPa was obtained.     

Microstructure and mechanical property evaluation of pulsed DC magnetron sputtered Cr–B and Cr–B–N films

CrB₂ and four Cr–B–N films with high Cr/B ratio and various nitrogen contents were deposited by a co-sputtering process using a bipolar asymmetric pulsed DC reactive magnetron sputtering system. The structures and BN bonding nature of the thin films were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), respectively. The surface and cross sectional morphologies of the thin films were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The surface roughness of the thin films was explored by atomic force microscopy (AFM). Nanoindentation, microscratch and ball-on-disk wear techniques were used to evaluate the hardness, and tribological properties of the thin films, respectively.The microstructure of the Cr–B–N thin films changed from a coarse columnar structure to a glassy and featureless morphology as the nitrogen content increased from 15.2 at.% to 54.5 at.%, whereas the corresponding structure developed from an amorphous state to a nanocomposite structure consisting of CrN nanograins and amorphous BN phases. It was found that high hardness, good tribological and brittle properties were obtained for the CrB₂ coating. The hardness and elastic modulus of the Cr–B–N thin films decreased with increasing nitrogen content until the nanocomposite structure of nanocrystalline CrN grains and an amorphous BN matrix was formed. However, the hardening effect induced by the nanocomposite structure was limited due to the fact that the small CrN nanograins were surrounded by a thick intergranular soft amorphous BN layer. On the other hand, the fracture toughness and resistance against elastic strain to failure of the Cr–B–N coatings were effectively enhanced by the addition of nitrogen.     

High purity boron nitride thin films prepared by the PDCs route

Hexagonal boron nitride (h-BN) thin films (< 10 μm) were successfully obtained on various substrates (graphite-standard and HOPG, quartz and SiC) using the preceramic polymer route. Thin films were formed using precursor solutions of poly(2,4,6-trimethylamino)borazine (polyMAB) as a source of BN. Various preparation conditions were used (i.e. solvent, precursor nature and concentration, substrate and deposition method) and their impact on final BN film quality measured. Surface morphology was observed by Scanning Electronic Microscopy (SEM) and Atomic Force Microscopy (AFM). Presence of BN material was confirmed by infrared and Raman spectroscopies and the structure observed by High Resolution Transmission Electronic Microscopy (HRTEM). The chemical composition of samples analyzed by X-ray Photoelectron Spectroscopy (XPS) gives a B/N ratio close to 1. Boron nitride films were also prepared using borazine (B₃N₃H₆) as precursor. Initial results are presented and compared with those obtained from polyMAB solutions.     

Deposition of wear resistant coatings based on diamond like carbon by unbalanced magnetron sputtering

Amorphous hydrogenerated carbon films containing a small amount of metal (Me:C-H) have been deposited by closed field unbalanced magnetron sputter ion plating. The films have graded film compositions to optimise the adhesion to the substrates, and multilayer TiC/Ti:C-H films have also been deposited. The films have excellent properties: very high measured microhardness (more than 4000 H_v), excellent adhesion (L_c 115–125 N), coefficients of friction against WC of less than 0.2, and volumetric wear rates one fifth that of titanium nitride. The coating procedure is ideally suited to the system used, and many applications for the films are already realised.     

Synthesis and characterization of cubic boron nitride thin films using the ME-ARE method

Cubic boron nitride (cBN) films were deposited by a magnetically enhanced activated reactive evaporation (ME-ARE) technique. Pulsed DC instead of r.f. power was used to bias the substrate. The effect of deposition parameters such as substrate bias voltage, plasma discharge current and gas flow ratio on the formation of cBN was investigated. BN films were characterized by FTIR and TEM. CBN films with a high content of cubic phase were successfully synthesized. It was found that formation of cBN film requires the bombardment of ions with both high flux and high energy. TEM observation showed that the cBN film had grain sizes of 15-50 nm and that a non-cubic phase BN, 10-15 nm was initially grown.     

High temperature dependence of the cubic phase content and optical properties of BN thin films

The temperature dependence of the cubic phase content and optical properties of Boron nitrogen (BN) thin films was studied in this paper. The BN thin films were deposited on fused silica and Si substrates by radio frequency bias magnetron sputtering. The BN film properties before and after annealing were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and UV-visible transmittance and reflection spectra. The results indicate that annealing temperature has a significant effect on the optical absorption edge, optical absorption coefficient α, refractive index n, and optical conductivity σ of BN films. The optical absorption edge shift to the high energy with annealing temperature increase indicates that the film optical band gap E_g becomes large. The change in the optical absorption properties results from the stress relaxation and phase transformation owing to the high temperature annealings. The dependence of α on the photon energy is fitted by the Urbach tail model in order to determine the Urbach energy E₀. In addition, it is found that refractive index n exists clearly different dependences on temperature in visible and ultraviolet regions, and the optical conductivity σ threshold moves to high energy with increasing annealing temperatures in the threshold region.     

Laser ablation synthesis and characterization of nitride coatings

Thin film nitride coatings were deposited on Si (100) substrates by the pulsed laser deposition (PLD) technique. The PLD method is a unique process for depositing high quality thin films with novel microstructure and properties. Boron nitride (BN) films deposited on Si (100) substrates have a higher percentage of c-BN phases when processed in higher nitrogen partial pressure. Titanium nitride films deposited on Si (100) substrates at a higher temperature (600 °C) have better quality crystallinity and higher hardness and Young’s modulus values than films deposited at lower temperatures. Nanoindentation technique was used to measure the mechanical properties of thin films. The film orientation was determined by x-ray diffraction. Atomic force microscopy (AFM) technique was used to understand the growth structure of the films.     

Formation of BN films on carbon fibers by dip-coating

Turbostratic boron nitride (BN) films (amorphous with some microcrystallinity) were successfully deposited onto carbon fibers and graphite substrates by dip-coating in methanolic boric acid and urea solutions, followed by nitriding in an ammonia flow at 1000 °C. BN coatings exhibited an orange-peel or pebble-like structure. Surface morphology results indicated that the sizes of the grain-like particles increased with the concentration of the dipping solution. The thickness of the BN film exhibited parabolic relationships with the viscosity of the dipping solution and the withdrawal speed. With the homogeneous surface, the thickness of the BN film increased with the concentration of the reactant in the solution. However, stripping and cracking at the surface have been observed while the reactant concentration was higher than 0.9 M. The yield of BN increased with the nitriding temperature. The increasing trend was slowed down at 800 °C and attained a maximum at 1000 °C.     

Machinability of BN free-machining steel in turning

In the past few years, extensive researches have been done to improve the machinability of work materials in order to increase productivity and reduce the effect on the environment. To satisfy these demands, various free-machining steels have been researched and developed. One of them is BN free-machining steel that contains hexagonal boron nitride (h-BN). However, the machinability was not stable. In this study, machining tests were carried out to clarify the machinability of steels and appropriate chemical composition of work material and tool material to achieve high efficient machining. Tested work materials were plane carbon steel JIS S45C and BN free-machining steels. The JIS S45C was used as the standard. The tool wear in turning BN free-machining steel was smaller than that in turning standard steel. In case of turning BN1 with P30 at 200, 300 m/min, the wear progress rate of flank wear and crater depth were about half as much as that in turning standard steel. BN free-machining steel showed slightly lower cutting temperature and smaller cutting force in comparison with standard steel at the tested cutting speeds. Al and N were detected as a layer at the tool wear region of P grade carbide tools after turning BN free-machining steel at high cutting speed. It is thought that one of the main reasons of outstanding machinability of BN free-machining steel is that the deposited layer containing Al and N acts as diffusion barrier at the tool–chip interface. In turning larger Al content BN-added steel with higher Ti content cutting tools, a larger wear reduction was observed. Therefore, it is said that not only added BN but also appropriate Al is necessary in work material.     

Deposition of BN films on metal substrates from a fluorine-containing plasma

Boron nitride (BN) films were deposited on Mo, W, Ni, Ti and Zr substrates by DC arc jet chemical vapor deposition using a gas mixture of Ar-N₂-BF₃-H₂ at 50 Torr, a substrate temperature of 850-1150 °C, and a − 85 V substrate bias. Cubic BN (c-BN) films showing clear c-BN Raman peaks were obtained on Mo and W, but they did not adhere well to the substrates. Hexagonal or turbostratic BN was deposited predominantly on Ni substrates, which is similar to the preferable deposition of graphitic carbons in diamond CVD. High quality c-BN films with good adhesion were obtained on Ti and Zr. The reasons for these differences among metal substrates are discussed.     

射频负偏压与放电电流对c-BN薄膜形成的影响

用ＡＲＥ（Ａｃｔｉｖｅ Ｒｅａｃｔｉｏｎ Ｅｖａｐｏｒａｔｉｏｎ） 装置, 在Ｎ２／Ａｒ 混合等离子体弧光放电气氛下, 通过电子束蒸镀纯硼, 同时伴以一定能量的正离子轰击生长的膜表面的方法, 在单晶硅（１００） 基片上成功地合成了立方氮化硼（Ｃｕｂｉｃ Ｂｏｒｏｎ Ｎｉｔｒｉｄｅ , 简称ｃＢＮ） 薄膜, 并对基片射频自偏压和等离子体弧光放电电流对ｃＢＮ 膜形成的影响进行了研究。用富立叶变换红外（ＦＴＩＲ） 透射谱和ＡＥＳ对沉积的膜进行相结构和化学成分分析。ＦＴＩＲ 透射谱表明, 在波数约１ ０６０ｃｍ － １ 处, 存在很强的ｃＢＮ 的吸收峰。随基片所加射频负偏压及等离子体弧光放电电流的增大, 膜中的ｃＢＮ 含量增大; 当射频偏压为－ ２００ Ｖ, 放电电流为１５ Ａ 时, 沉积的膜为单相ｃＢＮ 膜。ＡＥＳ 的成分深度分布表明,ｃＢＮ 膜中的Ｂ, Ｎ 接近等原子比     

PCBN刀具断续干式切削ADI时切削力与寿命的研究

选用DBW85、DBC50、BN250、BN700四种牌号的PCBN复合片刀具断续干式车削等温淬火球墨铸铁(ADI),测定了在相同几何参数下的切削力和在不同速度下的刀具寿命。试验结果表明:(1)在所选用四种牌号PCBN刀具中,高CBN含量的BN700和DBW85断续加工ADI的性能,要优于低CBN含量的BN250和DBC50,其中DBW85性能最好。(2)高CBN含量的BN700和DBW85加工ADI时,切削速度可选择偏高一些,一般要大于130m/min,低CBN含量PCBN刀具加工ADI时,切削速度要选择偏低一些,在100m/min左右。(3)黏结剂中添加W元素可以有效抑制PCBN刀具切削ADI时的化学磨损,改善刀具韧性,有利于ADI的断续切削。     

Structure and tribological properties of carbon nitride films obtained by the reactive ionized cluster beam method

Carbon nitride thin films were synthesized by the reactive ionized cluster beam (RICB) deposition. Raman scattering analysis shows the existence of a characteristic peak due to covalent C---N single bonds. This is consistent with the results of Fourier transform infrared (FTIR) transmission measurements. Rutherford backscattering (RBS) measurements show that the composition ratio, N/C, as high as 0.67, can be obtained. The films deposited under the optimized experimental conditions exhibit an extremely high hardness of 61 GPa. The friction and wear behavior of these films without any lubrication were measured by a reciprocating-motion ball-on-disk tribometer. It is noted that the deposited films have low initial and a steady-state friction coefficients less than 0.08. The wear factor of carbon nitride films is significantly lower than that of carbon thin films prepared by the same deposition system and evaluated under similar test conditions. These results are very encouraging for the tribological applications of carbon nitride films.     

Vapor phase polymerization of poly (3,4-ethylenedioxythiophene) on flexible substrates for enhanced transparent electrodes

Recently, conducting polymer thin films have been investigated as transparent electrodes in photovoltaic devices and organic light emitting diodes. Due to its relatively high conductivity and excellent transmission in the visible region, poly (3, 4-ethyelenedioxythiophene) (PEDOT) has been shown to be a viable option for such applications. Herein described is a method for the vapor phase polymerization (VPP) of transparent PEDOT thin film electrodes on flexible polyethylene naphthalate (PEN) substrates and the comparison of this VPP method with two current approaches to PEDOT deposition: solution-based in situ polymerization and spin coating a dispersion of PEDOT:PSS. Electrical conductivities and UV–vis transmittances were measured for films produced by each of these methods, with VPP PEDOT showing both the highest conductivity (approx. 600 S/cm) and transmittance (>94% at 550 nm). The surface morphologies of the films were compared using AFM and SEM imaging. The stability of these PEDOT films, stored under ambient conditions, was investigated by monitoring the conductivity and transmittance of the thin films over time.     

Electrodeposition of DLC films on carbon steel from acetic acid solutions

In this paper the electrodeposition of DLC films on carbon steel from aqueous acetic acid solutions and their structural and mechanical characterization are reported. The process is performed at room temperature at relatively low cell voltages (from ?8 to ?20 V) with entirely environmentally friendly chemicals. Qualitative and quantitative evaluation of C hybridisation type have been performed by Raman spectroscopy. Microhardness and adhesion of the supported electrodeposited films have been measured by micro-indentation and scratch-testing. Notably, ductile failure was found to correspondence to a wide range of film growth conditions. The corrosion resistance of DLC-coated steel has been assessed by electrochemical impedance spectrometry in a neutral chloride solution. Optimal electrodeposition conditions were identified for the formation of high-quality DLC films ca. 270 nm thick with a high content of diamond-coordinated carbon and an ideal combination of hardness and adhesion; films formed under these conditions also confer some degree of corrosion protection to the steel substrate.     

Growth and transport properties of oriented bismuth telluride films

Oriented n-type bismuth telluride thin films with various layered nanostructures have been fabricated by radio-frequency (RF) magnetron sputtering. The crystal structures and microstructures of the films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The transport properties including carrier concentration, mobility, Seebeck coefficient and in-plane electrical conductivity were measured, which showed strong microstructure-dependent behaviors. The relationship between morphologies and transport properties of the films was explored. The optimal morphology and transport properties of films were obtained at the substrate temperature of 350 °C under the pressure of 1.0 Pa with oriented layered structure. Based on these results, a formation mechanism of these nanostructures is proposed and discussed. The interfaces and grain boundaries formed in these layered structures are beneficial to the reduction in thermal conductivity, which could result in potential TE films with high ZT value.     

CARBON NITRIDE FILMS PREPARED AT DIFFERENT N2／Ar RATIOS BY CLOSED FIELD UNBALANCED REACTIVE MAGNETRON SPUTTERING

Carbon nitride ( CNx thin films have been deposited onto Si(100) (for structural and mechanical analyses) and M42 high-speed-steel (for tribological measurements) substrates at room temperature by closed-field unbalanced magnetron sputtering. The mechanical and tribological properties of these films were highly dependent on the N/C concentration ratio that was adjusted by the F(N2)/F(Ar) flow-rate ratio at fixed substrate biasing of -60V during deposition. The films were characterized by employing scanning electron microscopy (SEM), atomic force microscopy (AFM), nano-indentation measurements, X-ray photoelectron spectroscopy (XPS), Raman scattering and Fourier transform infrared (FTIR) spectroscopy, pin-on-disc tribometer, scratch tester, and Rockwell-C tester. The results showed that the N content in the films increased with the N2 pressure. However, the maximum N/C ratio obtained was 0.25. The nanohardness was measured to be in the range of 11.7-20.8 GPa depending on the N/C ratios. The XPS N 1s spectra showed the existence of both N-C sp^2 and N-C sp^3 bonds in films. Raman and FTIR spectra exhibited that N-C bonds were fewer when compared to other N-C bonds. The friction coefficient of the film deposited onto steel substrate with N/C=0.26 was measured to be -0.08 and for film with N/C=0.22 a high critical load of 70N was obtained. The tribological data also showed that the wear rates of these films were in the range of -10^-16m^3/Nm, indicating excellent wear resistance for CNx films.     

Effect of heat treatment on the stress and structure evolution of plasma deposited boron nitride thin films

Boron nitride (BN) thin films are deposited at 573 K by plasma enhanced chemical vapor deposition (PECVD) with ammonia (NH₃) and hydrogen diluted diborane (15% B₂H₆ in H₂) source gases. UV-visible and Fourier transform infrared (FTIR) spectroscopies together with surface profilometry are used for the film characterization. These films are hydrogenated (BN:H) whose hydrogen content is pursued following the 1.5 h annealing process at 748 K, 923 K and 1073 K under nitrogen atmosphere. Hydrogen escape with the rising annealing temperature is observed together with increases of the compressive stress, band gap and Urbach energies. Films are composed of the hexagonal BN (h-BN) clusters that grow dominantly parallel to the substrate surface with some non-parallel planes at the edges of the clusters, which are embedded in an amorphous tissue (the so-called turbostratic structure, t-BN). Annealing seems to promote non-parallel planes, thus creating more stressful and distorted network. Most of hydrogen atoms are removed from the film annealed at 1073 K and wurtzite BN (w-BN) phase is formed with volume fraction of 57%. As a consequence or in parallel of hydrogen reduction, high compressive stress causes the cracking of the films.     

原位反应渗透法制备石墨／AlN涂层材料

采用喷射法在石墨基体表面形成BN薄层，利用Al与BN原位渗透反应并渗入石墨基体，在基体获得AlN涂层来增强石墨的抗腐蚀能力。采用DTA、XRD分析方法，对原位反应过程进行分析，并探索了热处理工艺条件对反应物相结构的影响，确定了的最佳热处理工艺条件。采用SEM分析方法，对喷射工艺参数以及AlN涂层／石墨微观结构进行分析；采用EPMA对合成AlN涂层／石墨进行元素分布分析。结果表明：采用原位合成工艺可获得致密结构的AlN涂层，同时在石墨基体与涂层之间形成致密的结合界面。