Steel surface processing by a continuous optical discharge plasma

The influence of a continuous optical discharge (COD) plasma generated in flowing argon and argon-nitrogen mixture on alloy and carbon steel surfaces has been investigated. Changes in the structure, element composition, and microhardness of steel surface layers under the action of a COD plasma and laser beam were observed. In the presence of a COD plasma the microhardness distribution in hardened zone reaches its maximum at the metal surface and is different from that measured for samples processed by laser beam only.     

Laser surface treatment of high‐speed tool steel (AISI M2)

High‐speed tool steel (AISI M2) surface is pre‐prepared to form a thin carbon film containing 5% B₄C particles prior to laser treatment process. Morphological and metallurgical changes are examined in the treated layer using electron microscope, energy dispersive spectroscopy, and X‐ray diffraction. The microhardness and the residual stress formed at the treated surfaces are measured for samples with and without B₄C particles. It is found that the micro‐stresses formed in the neighborhood of B₄C particles at the treated surface contributed to the microhardness enhancement at the surface. This is associated with the mismatch of thermal expansion coefficients between B₄C particles and the base alloy. The nitride phases are formed at the treated surface, which also contribute to the microhardness increase at the surface. Copyright © 2012 John Wiley & Sons, Ltd.     

Surface and interface analysis of titanium nitride diffusion barriers

Titanium nitride films were produced on silicon substrate by ion beam assisted deposition in the alternate mode: first, thin titanium layers were deposited by electron beam evaporation and then titanium nitride was formed by nitrogen implantation at room temperature; this cycle was then iterated many times in order to obtain thicker titanium nitride layers. The obtained films were characterized with respect to atomic composition by Rutherford backscattering spectrometry and nuclear reaction analysis techniques, while chemical bonding was investigated by Auger line-shape analysis. We observe that nitrogen implantation, along with the production of titanium nitride, induces silicon migration into the film. Silicon transport is connected to point defects produced by ion implantation as well as by chemical driving forces associated with silicides formation.     

An overview of boron nitride based polymer nanocomposites

Recently, boron nitride (BN) based materials have received significant attention in both academic and industrial sectors due to its interesting properties like large energy band gap, good resistance to oxidation, excellent thermal conductivity, thermal stability, chemical inertness, significant mechanical property and widespread applications. This review article deals with the preparation and properties of boron nitride and its nanocomposites with various polymers. Diverse polymers have been explored for the preparation of boron nitride filled polymer nanocomposites by adopting different mixing methods. Properties of the resulting polymer nanocomposites mainly depend up on filler size and dispersion, mixing conditions and type of interaction between polymer matrix and the filler. Herein, the structure, preparation and properties of various boron nitride based polymer nanocomposites are reviewed in detail along with a brief overview of different classes of BN nanomaterials.     

Oxide and nitride protective layers on stainless steel studied by AES,WDS and XPS

Protective surface layers on AISI 321 stainless steel were prepared by thermal treatments at two different temperatures in air and two controlled atmospheres. Different oxide and/or nitride layers were formed. Surface morphology of the layers was investigated by scanning electron microscopy (SEM). Auger electron spectroscopy (AES) depth profiling of the samples was performed. Since depth profiling suggested layer thicknesses of the order of hundreds of nanometres, an attempt was made to obtain some fast, averaged information about the layer compositions using wavelength dispersive spectroscopy (WDS) at two different beam energies to obtain probing depths best suited to the layer thickness. X‐ray photoelectron spectroscopy (XPS) profiling of one layer was also performed to obtain information about the chemical states of the elements inside the layer. The analysed samples showed considerable differences with respect to their surface morphology, oxide/nitride layer thicknesses, compositions and layer–metal interface thickness. Copyright © 2007 John Wiley & Sons, Ltd.     

Implantation assisted deposition of hard carbon coatings on steel substrates

Summary Rutherford backscattering in combination with ¹²C(d,p_o) ¹³C nuclear reaction has been applied to understand the high wear resistance of tool steel after implantation of carbon ions. Slant deuteron incidence and glancing proton detection enables the called nuclear reaction for carbon depth profiling within a 200 nm thick near surface layer structure. Carbon ion beam assisted deposition of carbon together with carbon/substrate ion beam mixing was observed.     

The chemical state plot for beryllium compounds

Herein, we report the construction of a Wagner chemical state plot for beryllium containing the following: metallic, oxide, nitride and carbide forms of beryllium by combining electron beam‐induced AES and XPS data. AES and XPS values were collected from metallic beryllium mechanically abraded in vacuum, bulk and native beryllium oxide and homogeneous secondary‐phase beryllium nitride and beryllium carbide inclusions. XPS data for beryllium nitride and carbide were obtained from the literature. Copyright © 2015 John Wiley & Sons, Ltd.     

低碳钢基体中离子注入镍和钼的电催化活性

离子注入不受相律和化学平衡的限制,也不受离子源和基体种类的约束,注入离子的能量和剂量精确可控,因而它是实现材料表面改性最有效的方法之一.自Grenness等发现注铂的钨电极,对H~+还原的电催化性能与纯铂接近之后,Wolf等将注入的Pt/RuO_2、Pt/C、Pt/WC电极用于H~+、O_2的电化学还原及甲酸的电化学氧化,其催化活性和稳定性均优于光滑的纯铂电极、Thompson等在钛基上注铂,用于催化析氢也得到类似的效果。近期文献报导,用热处理或电沉积方法制备的Ni-Mo、Ni-Mo-V 合金电极有很低的析氢超     

New laser plasma process to obtain solid coatings and their structural characteristics

Carbon nitride coatings are synthesized in the new laser plasma of powerful optical pulsating discharge using acetonitrile as a precursor. A high-pressure and -temperature C₃N₄ cubic phase with a spinel structure type is obtained. The microhardness of coatings of this structure type is ~45 gPa. The chemical composition and structure of the coatings are characterized by a complex of spectroscopic (IR, Raman, EDS) techniques as well as microscopic (AFM and XRD) techniques.     

New mixed alkaline-earth nitridomolybdate(VI) nitride oxides with anion-ordered sub-structures

New molybdenum(VI) nitride oxides were synthesised by the reaction of strontium nitride and calcium nitride with molybdenum foil at high temperature in sealed stainless steel crucibles. The reactions yielded single crystalline products determined by X-ray diffraction to form complex structures in the triclinic space group P1(no. 2). The mixed alkaline earth compounds with composition Ca38Sr13[MoN4]12N8O3 and Ca36Sr15[MoN4]12N8O3 are isostructural with the quaternary nitride oxides Sr51[WN4]12N8O3 and Ca51[WN4]12N8O3. The structures contain isolated [MoN4](6-) tetrahedra, partially disordered alkaline earth cations and an ordered sublattice of N(3-) and O(2-) anions. Oxide anions are coordinated only to the alkaline earth metals. The title compounds are the first mixed alkaline earth metal nitride oxides.     

X-ray diffraction analysis of microregions of a cumulative coating on titanium

Quantitative X-ray diffraction analysis of different parts of the coating on titanium obtained by cumulative explosion is performed. The examination of microregions of the coating sized from 1 mm to 0.1 mm reveals that the phase based on the cubic cell of titanium nitride dominates in the upper layers. The predominance of this phase in some regions of the coating provides their increased microhardness. Crystal chemical and EDX analyses indicate the development of non-stoichiometric phases of complex composition. The problem of site occupation factors of light atoms arising in the full-profile refinement of powder X-ray patterns is discussed.     

Auger microprobe-surface analysis of sub-μm nitrides and carbonitrides in steel

Analytical and Bioanalytical Chemistry - The application properties of steel can be improved considerably by alloying with nitrogen which may present both as dissolved nitrogen and as nitride...     

Ni-Mo氮化物催化剂:合成及其丙烷氨氧化催化性能简

分别采用溶胶-凝胶法、旋转蒸发微波干燥法、共沉淀法、浸渍法和机械混合法制备Ni-Mo氧化物前驱体. 以H₂和N₂的混合气为氮化气体,采用程序升温氮化法合成了镍钼氮化物催化剂. 利用X射线衍射、总氮含量分析、X射线光电子能谱及H₂程序升温还原对Ni-Mo氧化物前体及氮化物催化剂进行了表征. 将上述Ni-Mo氮化物催化剂用于丙烷氨氧化反应中. 结果表明,Ni-Mo氧化物前驱体的制备方法影响其氮化物催化剂上丙烷氨氧化反应性能. Ni-Mo氮化物催化剂中氮物种的移动性及反应性对产物丙烯腈选择性的影响较大,共沉淀法制备的催化剂存在大量的活性氮物种,因而具有良好的催化丙烷氨氧化反应活性.     

Electrochemical Behavior of TiN Coatings on Stainless Steel and Titanium Nickelide Articles for Medical Purposes

Russian Journal of Electrochemistry - Titanium nitride (TiN) coatings which were fabricated by ion-plasma deposition on medical alloys—titanium nickelide (TiNi) and stainless steel were the...     

Cathodoluminescence analysis of nonmetallic inclusions of nitrides in steel

Identification of nitride inclusions such as boron nitride (BN) and aluminum nitride (AlN) is important in the steelmaking industry because BN inclusions deteriorate the creep strength of ferritic heat-resistant steel, and AlN inclusions cause transverse cracking in twin-induced-plasticity steel. The conventional method employed for the analysis of such inclusions in steel comprises both optical microscopy and electron probe microanalysis (EPMA), which is the time-consuming. The aim of this study is to investigate the application of cathodoluminescence (CL) analysis (both images and spectra) to the rapid identification of BN and AlN inclusions. Measurement samples were prepared by heating mixtures of 99 mass% Fe and 1 mass% B or Al powders at 1550°C in a nitrogen atmosphere. BN inclusions larger than 5 μm and AlN inclusions 20 μm in size were identified within 1 second on the basis of their luminescence color (blue-violet for BN and blue for AlN) in the CL images. We demonstrated that BN, AlN, and alumina inclusions could be identified from their CL spectra without the conventional method of EPMA. Capturing a CL image can provide a means of rapidly identifying BN and AlN inclusions in steel. We also carried out CL analysis on a sample containing TiN inclusions which can trigger cleavage fracture in low-carbon steels. No luminescence was detected in the CL image, and there were no CL spectral peaks, indicating that it is difficult to apply CL analysis to the identification of TiN inclusions.     

Parametric study of the decomposition of NH3 for an induction plasma reactor design

The present paper reports a study of the gas mixing and chemical transformation in an induction plasma reactor under atmospheric pressure, and its dependence on the plasma operating conditions. For this purpose, the thermal dissociation of ammonia into nitrogen and hydrogen was chosen because of the relative simplicity of the reactions involved and its use in a number of studies on plasma synthesis of ultrafine nitride ceramic powders using ammonia as nitriding agent. A hot-wall reactor configuration is investigated in which ammonia is injected radially through multiple orifices into the gases at the exit nozzle of an induction plasma torch. Concentration mapping in the mixing zone was carried out, using a VG-Micromass-PC 300 D quadrupole mass spectrometer, for different plasma power levels, in the range 13–24 kW. A 3-point injection mode is used with the injection ports oriented upstream at 45° to the torch axis. This allows uniform mixing of the injected gas in the plasma jet. A systematic study of the effects of plate power and ammonia and plasma gas flow rates on the mixing and dissociation of NH₃ in the reactor is reported. The results are analyzed and discussed from the viewpoint of their use for optimizing the design of induction plasma reactors, to he applied to the vapor-phase synthesis of ultrafine silicon nitride powders.     

Cobalt boron nitride: A novel heterogeneous catalyst for the synthesis of medicinally important α-amino quinoline phosphonates

A novel cobalt supported on boron nitride (CoBNT) heterogeneous catalyst for the synthesis of α-amino quinoline phosphonates (AQPs) is reported in the present work. The CoBNT was synthesised by simply mixing boron nitride in a solution of cobalt acetate, under an inert atmosphere for 7 d followed by filtration; the yield was 94%. It exhibited excellent catalytic properties for the synthesis of 16 novel AQPs in a one pot mixture containing 2-methoxy 3-formyl quinoline, aniline derivatives and diethyl phosphite. Reactions were rapid, products were easily worked-up and were obtained in more than 90% yield. The CoBNT also exhibited higher catalytic activity than conventional catalysts and was re-used five times without significant decrease in catalytic activity.     

Determination of the stoichiometry of vanadium nitride films by proton back-scattering

Vanadium nitride films were grown on stainless steel and silicon, with different nitrogen concentrations by varying the partial pressures of nitrogen in a DC magnetron sputtering set up. These films were characterized for their composition by proton back-scattering and their micro hardness values were correlated with their N/V ratio.     

Structure,hydrophilicity and corrosion resistance of sol–gel derived Ag-containing TiO2 film on plasma nitrided 316L stainless steel

Pure and Ag-containing TiO₂ films (Ag/Ti = 3.3 at.%) are coated on plasma nitrided 316L stainless steel by sol–gel method for biomedical applications. The addition of Ag does not cause obvious change in TG–DSC curves of the dried gels. The rough surface generated by plasma nitriding and the addition of Ag improve structural integrity of the TiO₂ films. X-ray diffraction reveals N loss and oxidation of the nitride layer during calcination treatment, and peaks of Ag or its oxides are not detected. X-ray photoelectron spectroscopy analysis indicates that Ag presents as metallic state in the film. Water contact angles of the coating samples decrease with UV irradiation treatment. The potentiodynamic polarization tests in a Ca-free Hank’s balanced salt solution show that the TiO₂ coated samples have decreased corrosion resistance due to N loss and oxidation of the nitride layer. The methods for crystallization of TiO₂ gel layers with minimized or avoided structural changes of the nitride layer will be tried in order to improve corrosion resistance of the duplex treated 316L stainless steel.     

Very high thermal conductivity obtained by boron nitride-filled polybenzoxazine

A thermal conductivity of 32.5 W/mK is achieved for a boron nitride-filled polybenzoxazine at its maximum filler loading of 78.5% by volume (88% by weight). The extraordinarily high conductivity value results from outstanding properties of the polybenzoxazine matrix and the boron nitride filler. The bisphenol-A–methylamine-based polybenzoxazine possesses very low A-stage viscosity which aids in filler wetting and mixing. The filler particles with an average size of ca. 225 μm are large aggregates of boron nitride flake-like crystals. It has bimodal particle size distribution which assists in increasing the particle packing density. This filler–matrix system provides a highly thermally conductive composite due to the capability of forming conductive networks with low thermal resistance along the conductive paths. The SEM picture of the composite fracture surface reveals good interfacial adhesion between the boron nitride filler and polybenzoxazine matrix. Water absorption of the filled systems at 24 h is <0.1% and decreases with increasing filler content.