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Machining of hard to cut materials such as austenitic stainless steel presents a challenge due the thermo-mechanical properties of this material, which contribute to intensive buildup edge formation and negatively affect tool life. CVD TiCN + Al 2 O 3 and PVD AlTiN coatings deposited on cemented carbide substrates are generally recommended for machining austenitic stainless steel. These coatings were deposited by two different methods: (i) PVD AlTiN was deposited on the same substrate material at two different thicknesses (2.5 and 5 μm); (ii) CVD TiCN + Al 2 O 3 was deposited with the same thickness (5 μm) on two different substrates. A new approach to applying various PVD and CVD (coating + substrate) integrated systems is introduced in this study for austenitic stainless steel machining. The relationship between the coating and substrate characteristics of these material systems and tool performance was assessed. The characteristics of the coating/carbide substrate design were evaluated in terms of chemical, phase composition, architecture, mechanical properties in relation to the tribological and wear performance. The obtained results demonstrate an improvement in tool wear performance and tool life brought about by the surface engineered layer/carbide material with an optimal combination of coating/substrate properties. Based on these findings, a guideline is proposed for further study of the cutting tool life and wear performance of CVD and PVD coated cemented carbide inserts. [ABSTRACT FROM AUTHOR]

Ti(C,N)-based cermets with a CoCrFeMnNi high-entropy alloy (HEA) binder phase were coated via chemical vapor deposition (CVD). The influence of the HEA-bonded cermet substrate on the microstructure, orientation, adhesion, and high temperature frictional wear performance of the CVD coating was investigated. The results indicate that the HEA binder phase inhibits the growth of cermet grains and provides more nucleation sites for the coating. Thus, the coating on the HEA-bonded cermet has a smaller grain size. The substitution of HEA for the Ni binder phase increases the entropy value of the cermet system, resulting in a decrease in free energy. In the early stage of CVD, the gas atoms adsorbed on the solid surface with low free energy are in a more stable thermodynamic state, which enhances the adhesion strength between the coating and substrate. During high temperature frictional wear, the friction coefficient of the coating on Ni-bonded cermet is less than that of the coating on HEA-bonded cermet because of iron oxide lubricating films. However, the wear rate exhibits a reverse trend. The coating on the HEA-bonded cermet has the best wear resistance due to small grain size, superior hardness and excellent adhesion strength. The wear forms present in the CVD coatings are abrasive wear, adhesive wear and oxidation wear. [ABSTRACT FROM AUTHOR]

Abstract HfC nanowire-toughened HfC ablation resistant coating was prepared on carbon/carbon composites by two steps of chemical vapor deposition. Effects of HfC nanowires on the growth behavior, microstructure and ablation resistance of the HfC coating were researched. Due to the incorporation of HfC nanowires, the deposition rate of the HfC coating was improved, the HfC coating was composed of particle-stacked crystals. After incorporating HfC nanowires, the bonding strength and fracture toughness of the HfC coating increased. HfC nanowires could restrain the crack propagation of HfC coating during ablation, contributing to improving the ablation resistance of HfC coating. After ablation for 60 s, the mass ablation rate of the HfC-coated C/C sample reduced from 0.44 to 0.26 mg/s because of the incorporation of HfC nanowires. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Both (1 × 2) and (2 × 1) reconstructed Si(1 0 0):As surfaces can be prepared by MOCVD. • In situ RAS enables detailed process control even at elevated temperatures. • Si:As surface reactions strongly depend on the Si(1 0 0) substrate misorientation. • Atomically flat low-offcut Si(1 0 0):As-(1 × 2) surfaces with regular double-layer steps. • Arsenic atoms are considered to replace Si atoms during the adsorption process. Abstract Low-defect III-V integration on Si(1 0 0) requires atomically well-ordered heterointerfaces. To this end, we study the interaction of As with Si(1 0 0) surfaces and the formation of dimerized Si(1 0 0):As surfaces in situ with reflection anisotropy spectroscopy during metalorganic chemical vapor deposition (MOCVD). Control of surface processes allows us to intentionally 'rotate' the dimer orientation and choose between predominantly (1 × 2) and (2 × 1) reconstructed Si(1 0 0):As surfaces both for low and higher surface misorientation. We also verify that the (2 × 1) surface reconstruction becomes energetically more favorable for vicinal Si(1 0 0):As surfaces. We explain the preparation of Si(1 0 0):As surfaces displaying an almost single-domain, (1 × 2) reconstructed surface with an RMS roughness ≤1 Å and exhibiting broad, atomically flat terraces as well as regular double-layer steps. This surface is highly suitable for subsequent low-defect III-V integration. [ABSTRACT FROM AUTHOR]

Abstract The development of new coated cemented carbide tool grades, based on grain refining and the unidirectional orientation of crystals in the coating layer, allows this material to withstand the severe tribological conditions imposed in hard turning. Previously, this was only possible using PCBN or oxide ceramic tool materials. The aim of this research was to determine the limiting conditions for two coated cemented carbide grades (with MT CVD and PVD coatings) aimed at allowing them to withstand at least a machining time of 15 min in the turning of hardened steels, considering the cutting parameters usually adopted for PCBN tools. Turning experiments were performed on AISI 4340, AISI 52100 and AISI D2 hardened steels, and the worn cutting edges were analyzed using focus variation microscopy (FVM) applying the three-dimensional wear parameters. The use of the PVD-coated cemented carbide grade was feasible in the case of AISI 4340 steel with a level of hardness up to 55 HRC, allowing a machining time longer than 30 min. For AISI 52100 and D2 steels, feasibility was only observed with hardness levels up to 50 and 45 HRC, respectively. Interestingly, in these cases, longer machining times were achieved using the MT CVD-coated cemented carbide grade. Wear and consequent coating layer deterioration were found to be the limiting factors for tool life, and the three-dimensional wear parameters allowed these to be identified. The results indicated the appropriate limiting conditions for the application of coated cemented carbide grades in hard turning as a function of the steel microstructure and level of hardness. Highlights • Application of coated cemented carbide tools grades in turning of hardened steels. • Application of focus variation microscope (FVM) and volumetric wear parameters. • Criterion for tool life based on volumetric wear parameter. • Tool life is strongly associated with tools coating deterioration. • Coating deposition technique and steel microstructure influence the tool life. [ABSTRACT FROM AUTHOR]

Abstract: The results of corrosion-resistance analysis for tungsten-based coatings obtained by means of low-temperature chemical-vapor deposition from fluorine-containing media in alkaline solution are presented in this article. The study was carried out in the pH region where, according to the Pourbaix diagram, tungsten undergoes corrosion by the active dissolution mechanism. It is shown that, in alkaline solutions, the rate of general corrosion of a tungsten coating in solutions of natural aeration reaches values of 20-25 μm/year. An analysis of the electrochemical behavior of the coatings confirmed that the mode of corrosion dissolution is active, but it was noted that, in the region of high anodic polarization values, the growth of the anode current appears to be limited, which may be due to the formation of oxide layers that hinder the kinetics of anodic dissolution. [ABSTRACT FROM AUTHOR]

Abstract A flexible freestanding Si/Carbon nanofibers composite membrane with high mechanical strength is prepared by electrospinning and chemical vapor deposition techniques. The physical characteristics of Si/Carbon nanofibers are characterized by scanning electron microscopy, thermo-gravimetric analysis, X-ray diffraction and transmission electron microscopy. The electrochemical performances are investigated by galvanostatic charge-discharge tests and cyclic voltammograms. Carbon nanofibers matrix shows uniform diameter, smooth surface and three dimensional network structures. Si shell with a thickness of 50 nm is uniformly deposited on the surface of carbon nanofibers. The as-synthesized Si/Carbon nanofibers anode delivers 1310 mAh g−1 at 2nd cycle and the loss rate of capacity per cycle is as lower as 0.0703% from 2nd to 480th cycles, which exhibits excellent electrochemical performance. It demonstrates that the structure of three dimensional network membrane that has played an important role in alleviating volume expansion-contraction of Si-based anodes during charge-discharge process. Highlights • The composite membrane is obtained by electrospinning and chemical vapor deposition. • The novel composite membrane is prepared for the flexible anode in LIBs. • High capacity and good cyclability are achieved as the novel composite anode. [ABSTRACT FROM AUTHOR]

The fabrication of gravimetric gas sensors based on Nano Electro Mechanical System (NEMS) requires the use of a chemical sensitive layer that is uniformly deposited by a solvent-free deposition technique. In this work, we show than an organosilicate layer deposited by Filament-Assisted Chemical Vapor Deposition using methyltriethoxysilane presents very high affinity toward hydrocarbon gas. High partition coefficients toward toluene and pentane were obtained on Quartz Crystal Microbalance sensors after being annealed at 400 °C. It is shown that the hydrophobic nature of this material composed of a Si O Si backbone with methyl groups bonded to silicon, combined with the presence of isolated ethoxy groups and microporosity, allow a very high sensibility in comparison to others SiOCH. Furthermore, the functionalization of NEMS-based gas sensors was demonstrated. This material, deposited using a CMOS compatible technique, constitutes a promising solution for the development of a complete and portable multi-gas analysis system. [ABSTRACT FROM AUTHOR]

Abstract: Oxidation protective SiC nanowires‐reinforced SiC (SiCNWs‐SiC) coating was prepared on pack cementation (PC) SiC‐coated carbon/carbon (C/C) composites by a simple chemical vapor deposition (CVD) process. This double‐layer SiCNWs‐SiC/PC SiC‐coating system on C/C composites not only has the advantages of SiC buffer layer but also has the toughening effects of SiCNWs. The microstructure and phase composition of the nanowires and the coatings were examined by SEM, TEM, and XRD. The single‐crystalline β‐SiC nanowires with twins and stacking faults were deposited uniformly and oriented randomly with diameter of 50‐200 nm and length ranging from several to tens micrometers. The dense SiCNWs‐SiC coating with some closed pores was obtained by SiC nanocrystals stacked tightly with each other on the surface of SiCNWs. After introducing SiCNWs in the coating system, the oxidation resistance is effectively improved. The oxidation test results showed that the weight loss of the SiCNWs‐SiC/PC SiC‐coated samples was 4.91% and 1.61% after oxidation at 1073 K for 8 hours and at 1473 K for 276 hours, respectively. No matter oxidation at which temperature, the SiCNWs‐SiC/PC SiC‐coating system has better anti‐oxidation property than the single‐layer PC SiC coating or the double‐layer CVD SiC/PC SiC coating without SiCNWs. [ABSTRACT FROM AUTHOR]

Micro-mechanical properties of Ti(C,N) and Zr(C,N) coatings deposited by chemical vapor deposition on a WC-Co cemented carbide substrate were examined by micro-compression testing using a nanoindenter equipped with a flat punch. Scanning Electron Microscopy, Focused Ion Beam, Electron Backscattered Diffraction and Finite Element Modeling were combined to analyze the deformation mechanisms of the carbonitride layers at room temperature. The results revealed that Ti(C,N) undergoes a pure intergranular crack propagation and grain decohesion under uniaxial compression; whereas the fracture mode of Zr(C,N) was observed to be inter/transgranular failure with unexpected plastic deformation at room temperature. [ABSTRACT FROM AUTHOR]

Thermogravimetric analysis (TGA) and mass spectrometry (MS) of initial steam oxidation at 650 °C in Ar + 40% H2O for 150 h of the P92 steel with and without aluminum‐silicon‐CVD coating were investigated. We deposited Al‐Si coating on ferritic/martensitic (F/M) P92 steel using the chemical vapor deposition in a fluidized bed reactor (CVD‐FBR) at 580 °C for 2 h and subsequently heat‐treated in Ar at 700 °C for 2 h. The thermodynamic software Thermo‐Calc was used for theoretical simulations in equilibrium under similar experimental oxidation conditions from 500 to 900 °C. TGA verified that the P92 steel coated with Al‐Si had not gained weight compared to the uncoated oxidized P92 steel that gained 5.25 mg/cm2. The coated sample, with protective oxide layers, i.e., silica (SiO2) and alumina (Al2O3) on the diffusion zone, was better protected during steam oxidation. Al‐Si‐CVD‐FBR coating helped to delay catastrophic oxidation and avoid loss of chromium from steel through volatilization. SEM: EBSD/EDAX and XRD were used to study morphology/composition and structure of the samples. [ABSTRACT FROM AUTHOR]

In this work, we present the results of electrochemical, Raman, FE-SEM/EDS, and XPS studies of graphene coatings deposited by chemical vapour deposition at atmospheric pressure on Mo foil and Pt-coated Mo foil as catalysts. The results showed that the graphene coating synthesized on Pt-coated molybdenum foil was bi-layer and had fewer defects, while the graphene coating on Mo foil was few-layer with more defects. The corrosion studies indicated that both graphene coatings on bare Mo and Pt-coated Mo exhibited good protective properties and can act as a barrier against corrosion in 0.1 M NaCl. [ABSTRACT FROM AUTHOR]

We investigate the effect of the chemical and physical defects on the humidity sensitivity of graphene. For this we apply reactive ion etching for physical defects and the poly(methyl methacrylate) (PMMA) coating for chemical defects to the CVD graphene. The tendency of humidity sensing is hardly found by the physical defects while the distinct changes are observed with chemical defects by control of the thickness and the coverage area of the PMMA on the graphene surface. The graphenes covered with thinner or smaller area of PMMA show an enhanced humidity sensitivity, indicating the possibility of H 2 O sensing. [ABSTRACT FROM AUTHOR]

The CVD diamond film with favorable adhesion and relatively thinner thickness is essential facing for its application on drills for machining carbon fiber reinforced plastics (CFRP), with regard to either the tool lifetime or the machining quality. A 500-nm-thick CrN layer was deposited by the cathode arc technique on slight chemical etched WC-Co 6wt.% drill, and nano-crystalline diamond (NCD) is subsequently deposited by the hot filament chemical vapor deposition (HFCVD) technique. The same NCD film is also deposited on the drills pretreated only by the slight chemical etching or the CrN interlayer, which are adopted as comparisons in the present study. The nucleation and growth of diamond film and the cutting performance of the coated drills are systematically studied. The results show that the drill pretreated by the slight chemical etching and CrN interlayer can acquire highest nucleation density (ND) compared to the other pretreatment methods as it sufficiently prevents the Co diffusion. The diamond-coated drill with deep chemical etching was used for comparison to study the machining quality when drilling CFRP. During machining the CFRP, the failure mode of the diamond-coated drill is mainly the delamination and peeling off of the diamond film at areas with stress concentration, while the diamond-coated drill pretreated by slight chemical etching CrN interlayer can retard such failure. The exit hole quality of CRFP machined by drill pretreated with slight chemical etching CrN interlayer is better than that by drill pretreated with deep chemical etching, which is ascribed to the different cutting edges of the drills. [ABSTRACT FROM AUTHOR]

Achieving high drug loading capacity and controlling drug delivery are two main challenges related to drug carriers. In this study, polymeric macroporous sponges with very high pore volume and large porosity are introduced as a new-type of drug carrier. Due to the high pore volume (285 and 166 cm³/g for the sponges with densities of 3.5 and 6.0 mg/cm³, respectively), the sponges exhibit very high drug loading capacities with average values of 1870 ± 114 and 2697 ± 73 mg/g in the present study, which is much higher than the meso and microporous drug carriers (<1500 mg/g). In order to control the release profiles, an additional poly(p-xylylene) (PPX) coating was deposited by chemical vapor deposition on the drug loaded sponge. Consequently, Artemisone (ART) release in the aqueous medium could be retarded, depending on the density of the sponge and the thickness of the coating. In future, the new 3D polymeric sponges would be highly beneficial as drug carriers for the programmed release of drugs for treatment of chronic diseases. [ABSTRACT FROM AUTHOR]

In this work, machining of the superduplex stainless steel was investigated using cemented carbide turning inserts with chemical vapor deposited (CVD) TiCN + AlO as well as physical vapor deposited (PVD) TiCN and AlTiN coatings. These three coating system were tested during finish turning operation of superduplex stainless steel. It has been found that unfavorable friction and wear conditions were observed when TiCN- and TiCN + AlO-coated tools were used. On the other hand, the AlTiN-coated tool showed a self-adaptive behavior through the formation of tribo-film of aluminum oxide that improves frictional conditions and, consequently, wear resistance during machining of SDSS. This behavior shows that the tool life for inserts coated with PVD AlTiN was approximately two times higher than CVD TiCN + AlO. Another important result that can be observed in this work is related with the surface integrity that was improved when machined with cutting inserts coated with PVD AlTiN. [ABSTRACT FROM AUTHOR]

Multiple layers of graphene thin films with micro-crystalline orientation and vertical graphene nano-sheets were grown on different substrates (i.e., polycrystalline nickel foil, Ni(111), highly oriented pyrolytic graphite) using a single-step process based on low-pressure remote Plasma-Enhanced Chemical Vapor Deposition (rPE-CVD). In contrast to previous studies, a novel basic approach to this technique including a new remote inductively coupled RF plasma source has been used to (i) minimize the orientational effect of the plasma electrical fields during the catalyst-free growth of graphene nano-sheets, (ii) warrant for a low graphene defect density via low plasma kinetics, (iii) decouple the dissociation process of the gas from the growth process of graphene on the substrate, (iv) tune the feedstock gas chemistry in view of improving the graphene growth, and (v) reduce the growth temperature as compared to conventional chemical vapor deposition (CVD). In order to study the various aspects of the rPE-CVD graphene growth modes and to assess the characteristics of the resulting graphene layers, Raman spectroscopy, XPS, SEM, and STM were used. The results give evidence for the successful performance of this new rPE-CVD plasma deposition source, that can be combined with in situ UHV-based processess for the production of, e. g., hybrid metal ferromagnet/graphene systems. [ABSTRACT FROM AUTHOR]

Polycrystalline diamond coatings have been grown on cemented carbide WC-6% Co substrates with different aspect ratios by microwave plasma CVD in CH 4 /H 2 gas mixtures. Special plateholder with holes for group growth has been used to protect the edges of the substrates from non-uniform heating due to the plasma edge effect. The difference in heights Δh of the substrates and plateholder, and its influence on the diamond film mean grain size, growth rate, phase composition and stress was investigated. Diamond growth rate of 0.3–1 μm/h and compressive stress of 2.2–2.5 GPa, respectively were determined in the optimal Δh region. The substrate temperature range of 740–760 °C, within which uniform diamond films are produced with good adhesion, is determined. The diamond-coated samples produced at optimized process conditions exhibited a reduction of cutting force and wear resistance by a factor of two, and increase of cutting path length up to 8150 m or by 4.3 times upon turning А390 Al-Si alloy as compared to performance of uncoated tools. Prime novelty Polycrystalline diamond coatings with uniform structure and thickness distribution are grown by microwave plasma CVD (MPCVD) on WC-6% Co substrates using an optimized pocket-type substrate holder. Edge effect during MPCVD on high substrates (height/diameter > 0.1) was suppressed. Influence of distance between the substrate holder and substrate surface on deposition temperature and other parameters was investigated. Cutting force and wear rate of the coated samples upon cutting of Si-Al abrasive alloy were twice less than that of uncoated WC-6% Co. [ABSTRACT FROM AUTHOR]

The tribological behavior of tenfold micro/nanocrystalline CVD diamond multilayers is here investigated in self–mated configuration using ball-on-plate reciprocating wear testing. The effects of relative humidity (RH) and temperature (T) on friction and wear coefficients are assessed. The strongest effect of humidity was found on the value of the critical load (no delamination) that triples from 40 N at 10%RH to 120 N at 90%RH. Evaluation of the wear coefficients of the plates was only possible with the use of 3D optical profilometry. A valley-shaped evolution is observed for the wear coefficient of the plates, within the 10% to 90% RH range, with a minimum of about 1.7x10 -7 mm 3 N -1 .m -1 , indicative of a mild wear regime, whereas the balls have lower values in the very mild wear regime of k ~ 10 -8 mm 3 N -1 .m -1 . The clearest difference between the RH and temperature experiments is observed for the critical loads, limited to the range 40-55 N at 50-100°C, while at room temperature a value of 120 N was reached. However, the critical loads at high temperature are similar to those attained under dry conditions (≤ 25% RH) highlighting the absence of water as the load bearing medium. [ABSTRACT FROM AUTHOR]

We report the fast growth of high-quality millimeter-size monolayer MoSe2 crystals on molten glass using an ambient pressure CVD system. We found that the isotropic surface of molten glass suppresses nucleation events and greatly improves the growth of large crystalline domains. Triangular monolayer MoSe2 crystals with sizes reaching ~2.5 mm, and with a room-temperature carrier mobility up to ~95 cm2/(Vos), can be synthesized in 5 min. The method can also be used to synthesize millimeter-size monolayer MoS2 crystals. Our results demonstrate that "liquid-state" glass is a highly promising substrate for the low-cost growth of high-quality large-size 2D transition metal dichalcogenides (TMDs). [ABSTRACT FROM AUTHOR]

Due to health concerns surrounding the use of cobalt as a binder for tungsten carbide in cemented carbides there is a drive to find an alternative binder. Although there are many publications on cemented carbides with alternative binders very few consider the possibility to coat these materials. In this work four different binder compositions containing iron-nickel or iron-nickel-cobalt and a pure cobalt reference are investigated with respect to coating ability. It is shown that it is possible to coat these cemented carbides with alternative binders through the same chemical vapor deposition process that is commonly used for cobalt based inserts and get similar coating structure. It is further shown that it can be done without the formation of η-phase and with comparable scratch test adhesion. [ABSTRACT FROM AUTHOR]

Since the technical means for the preparation and examination of nanostructured materials have been provided, a new generation of wear resistant coatings with grain sizes and structural effects in the nano-scale has emerged. In this contribution the authors will present a short summit of the state of the art in the field of nanostructured coatings and will then emphasise on the most recent developments in preparing CVD AlTiN. [ABSTRACT FROM AUTHOR]

Diamond coating with sufficient adhesion on WC-Co cutting tools is expected to significantly increase their cutting performance. In order to enhance the coating-substrate interfacial adhesion, Al 2 O 3 and Ta mono-interlayer, Al-Al 2 O 3 , Al-AlN and Al-Ta duplex interlayer systems have been developed in this study. These interlayer materials were prepared using a magnetron sputtering method, and diamond coating were deposited on them using microwave plasma enhanced chemical vapor deposition. Grazing incident X-ray diffraction was carried out to determine the phase components in the Al-Al 2 O 3 and Al-AlN interlayers. Raman spectroscopy and scanning electron microscopy were used to evaluate the quality, morphology and microstructure of the deposited diamond coatings. Rockwell C indentation testing was performed to evaluate the adhesion of the coatings. To elucidate the coating failure mechanism, the compositions around the delaminated spots of diamond coatings after indentation were identified by Energy-dispersive X-ray spectroscopy. The results show that continuous diamond coatings were achieved on Al 2 O 3 , Al-Al 2 O 3 , Al-AlN and Al-Ta interlayered substrates, whereas a graphite layer was still formed with the Ta monolayer accompanied by an easy spallation of diamond coatings. The Al interlayer has played an important role in obtaining high purity diamond by in-situ forming an alumina barrier layer. Especially, the diamond coating deposited with an Al-AlN interlayer demonstrates superior interfacial adhesion in comparison with all the other interlayers. [ABSTRACT FROM AUTHOR]

Material transfer from the work materials to the tools strongly influences machining performance and tool life. The influence of Si and Al additions to carbon steel on the material transfer and coating wear in turning with CVD coated carbide tools is investigated. Three model steels are specifically designed to separately study the effects of the individual alloying elements: one reference steel with C as the only alloying element (Base steel), and two steels alloyed also with 1 mass% Si or Al. In the region around the depth of cut on the rake face, where the outside edge of the chip passes over the tool surface, the coating is worn mainly by abrasion when cutting the Base steel. When cutting the Si alloyed steel, an almost pure Si–O transfer layer covers the coating surface, which protects it from wear. When cutting the Al alloyed steel, an almost pure Al–O transfer layer forms on the coating. This layer promotes steel transfer and associated adhesive wear of the coating, which rapidly results in coating detachment and eventually causes notch wear. In the crater region, only the Al alloyed steel results in a transfer layer, an AlN layer that reduces the crater wear. [ABSTRACT FROM AUTHOR]

We report on a convenient CVD fabrication of the uniform, compact and reproducible g-C 3 N 4 solid films on indium-tin oxide substrates. It is found that mixing quantitative thiourea into melamine as co-precursor prompts the deposition of greenish-yellow, transparent and smooth g-C 3 N 4 thin films. The thiourea apparently affects the crystalline, the surface morphologies and the energy band structures of g-C 3 N 4 films by modulating the polymerization process of the precursors, and simultaneously introduces S dopants into the g-C 3 N 4 films. Due to these roles of thiourea, the obtained S-doped g-C 3 N 4 films as a photoelectrode show a high and stable visible-light-driven photocurrent response. To further improve the photocurrent, the construction of three heterojunction structure types based on g-C 3 N 4 films is proposed and the corresponding charge transfer mechanisms are well discussed. The successful fabrication of high quality g-C 3 N 4 films in this work provides a footstone to construct the heterojunction film structures based on the carbon nitrides for the photoelectrochemical overall water splitting. [ABSTRACT FROM AUTHOR]

CVD-SiC coated and uncoated ceramic matrix composites (C f /SiC and SiC f /SiC) were joined to their counterparts with a pre-sintered Ti 3 SiC 2 foil using Spark Plasma Sintering. For the first time pre-sintered Ti 3 SiC 2 foil was used as a joining filler. The joining parameters were carefully selected to avoid the decomposition of Ti 3 SiC 2 and the reaction between the joining filler and the CVD-SiC coating, which would have deteriorated the oxidation protective function of the coating. Conformal behaviour of the Ti 3 SiC 2 foil during the diffusion joining and the infiltration of the joining filler into the surface cracks in the CVD β-SiC coating allowed the filler to be more integrated with the matrix material. While diffusion bonding occurred during joining of the coated composites, a combination of both solid-state reaction and diffusion bonding was observed for the uncoated C f /SiC composites. This produced the lower shear strength (19.1 MPa) when compared to the diffusion bonded CVD-SiC coated C f /SiC (31.1 MPa). [ABSTRACT FROM AUTHOR]

The aim of this paper is to present the results of the prediction of the properties of PVD/CVD coatings with the use of finite element method (FEM) analysis. The possibility of employing the FEM in the evaluation of stress distribution in multilayer Ti/Ti(C,N)/CrN, Ti/Ti(C,N)/(Ti,Al)N, Ti/(Ti,Si)N/(Ti,Si)N, and Ti/DLC/DLC coatings by taking into account their deposition conditions on magnesium alloys has been discussed in the paper. The difference in internal stresses in the zone between the coating and the substrate is caused by, first of all, the difference between the mechanical and thermal properties of the substrate and the coating, and also by the structural changes that occur in these materials during the fabrication process, especially during the cooling process following PVD and CVD treatment. The experimental values of stresses were determined based on X-ray diffraction patterns that correspond to the modelled values, which in turn can be used to confirm the correctness of the accepted mathematical model for testing the problem. An FEM model was established for the purpose of building a computer simulation of the internal stresses in the coatings. The accuracy of the FEM model was verified by comparing the results of the computer simulation of the stresses with experimental results. A computer simulation of the stresses was carried out in the ANSYS environment using the FEM method. Structure observations, chemical composition measurements, and mechanical property characterisations of the investigated materials has been carried out to give a background for the discussion of the results that were recorded during the modelling process. [ABSTRACT FROM AUTHOR]

The tungsten single crystal has many excellent properties, namely a high melting point, high anti-creeping strength. Chemical vapor transportation deposition (CVTD) is a possible approach to achieve large-sized W single crystals for high-temperature application such as the cathode of a thermionic energy converter. In this work, CVTD W coatings were deposited on the monocrystalline molybdenum substrate (a tube with < 111 > axial crystalline orientation) using WCl 6 as a transport medium. The microstructures of the coatings were investigated by a scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The as-deposited coatings are hexagonal prisms—rough surfaces perpendicular to < 110 > with alternating hill-like bulges and pits at the side edges of the prisms, and flat surfaces perpendicular to < 112 > with arc-shaped terraces at the side faces. This can be explained by two-dimensional nucleation -mediated lateral growth model. Some parts of the coatings contain hillocks of an exotic morphology (noted as “abnormal growth”). The authors hypothesize that the abnormal growth is likely caused by the defects of the Mo substrate, which facilitate W nucleation sites, cause orientation difference, and may even form boundaries in the coatings. A dislocation density of 10 6 to 10 7 (counts/cm 2 ) was revealed by an etch-pit method and synchrotron X-ray diffraction. As the depositing temperature rises, the dislocation density decreases, and no sub-boundaries are found on samples deposited over 1300 °C, as a result of atom diffusion and dislocation climbing. [ABSTRACT FROM AUTHOR]

Titanium alloy (Ti6Al4V) substrates were deposited with smooth multilayer coatings, by hot filament chemical vapour deposition technique. The effect of boron doping on lattice parameter, residual stresses, hardness and coefficient of friction in multilayer-diamond coating system was studied. The frictional behaviour of the coatings was studied using a ball-on-disc micro-tribometer by sliding the coated samples of titanium alloy (Ti6Al4V) substrates against alumina (AlO) balls, and increasing normal load from 1 to 10 N. The average friction coefficient decreased from 0.36 to 0.29 for undoped multilayer-diamond coating system and from 0.33 to 0.18 for boron- doped (BD) multilayer-diamond coating system. The average indentation depths for undoped and BD multilayer- diamond coating systems were found to be equal to ∼>58 and ∼65 nm, respectively, and their hardness values were 60 and 55 GPa, respectively. [ABSTRACT FROM AUTHOR]

This report is the first describing experimental evaluation of Fano factor for diamond detectors. High-quality self-standing chemical vapor deposited diamond samples were produced using lift-off method. Alpha-particle induced charge measurements were taken for three samples. A 13.1 ±0.07 eV of the average electron-hole pair creation energy and excellent energy resolution of approximately 0.3% were found for 5.486 MeV alpha particles from an 241Am radioactive source. The best Fano factor for 5.486 MeV alpha particles, calculated from experimentally obtained epsilon values and the detector intrinsic energy resolution, was 0.382 ± 0.007. [ABSTRACT FROM AUTHOR]

SiC coatings were prepared on carbon/carbon composites by pack cementation (PC) and chemical vapor deposition (CVD). The PC coating was composed of hexagonal platelets of α-SiC, while the CVD coating consisted of spherical particles of β-SiC. Their oxidation behaviors were investigated at 1173 K, 1473 K and 1773 K. Compared with the CVD-SiC coating, bubbles appeared in the PC-SiC coating at lower oxidation temperature and the oxide layer was thicker, which might be ascribed to the formation of aluminosilicate glass in the PC-SiC coating. With the increasing temperature, the oxidation behavior of the PC-SiC coating transformed from linear to parabolic with dramatically improved oxidation resistance, which might be attributed to the decreased viscosity of SiO 2 -rich glass and the good healing effect for cracks. The oxidation protective ability of the CVD-SiC coating was worse than that of the PC-SiC coating, because of the higher viscosity of pure SiO 2 glass and the inferior interface adhesion between the coating and the substrate. [ABSTRACT FROM AUTHOR]

This article discusses influence of the annealing temperature on the structural, optical and electrical properties of indium oxide thin films which are prepared on glass substrate heated at 150 °C by ultrasonic spray technique using indium chloride as precursor solution. The deposited samples annealed at 300 °C and 500 °C for 1 h. Structural analysis of these films suggest that the films are polycrystalline with a preferred grain orientation along the (222) plane, and the crystalline state of these films improve with the increase in the annealing temperature from 300 °C to 500 °C. The optical band gap is varied in the range of 3.64–3.73 ev. UV–vis spectroscopy show that the average transmittance is about 85% in the visible region, and the optical transmittance decrease with the increase of the annealing temperature. The electrical resistivity decreases from 80 Ω cm to 9.8 × 10 −3 Ω cm with the increase of the annealing temperature from 300 °C to 500 °C. [ABSTRACT FROM AUTHOR]

A chemical vapor deposited (CVD) aluminizing process had been employed to deposit platinum modified aluminide coatings on the nickel-based single-crystal superalloys. The kinetics behavior, phase evolution, microstructure and chemical composition of the (Ni, Pt)Al coatings after oxidation and hot corrosion tests were studied in detail. After isothermal oxidation test, a protective α-Al 2 O 3 scale is formed on the coating surface and, two new phases of (Ni, Pt) 3 Al 4 and γ′-(Ni, Pt) 3 Al due to phase transformation reactions occur in the aluminide layer. The inward diffusion of Al element toward the substrate and, formation of micro-pores in the interface of aluminide layer and interdiffusion zone are probably the main degradation modes of the coating. Corrosive medium including of mixed of aviation fuels and artificial seawater has not serious deterioration of the coating after hot corrosion and furthermore a network of grain boundary ridges is still co-existed on the coating surface, although large of micro-pores and some of grain boundaries are appeared within the aluminide layer. [ABSTRACT FROM AUTHOR]

Direct growth of a monolayer graphene film on a quartz substrate by a hot filament chemical vapor deposition technique is reported. The monolayer graphene film prepared was characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), selected area electron diffraction (SAED), and atomic force microscopy (AFM). The optical properties were studied by spectroscopic elliposmetry. The experimental data were fitted by the Forouhi-Bloomer model to estimate the extinction coefficient and the refractive index of the monolayer graphene film. The refractive index spectrum in the visible region was studied based on the harmonic oscillator model. The lattice dielectric constant, real and imaginary dielectric constants and the ratio of the charge carrier number to the effective mass were determined. The surface and volume energy loss parameters were also found and showed that the value of the surface energy loss is greater than the volume energy loss. The determination of these optical constants will open new avenue for novel applications of graphene films in the field of wave plates, light modulators, ultrahigh-frequency signal processing and LCDs. [ABSTRACT FROM AUTHOR]

Diamond single-crystal Schottky barrier mip-structures (metal-intrinsic diamond-p-doped diamond) with dimensions of 3 × 3 and 4.1 × 4.28 mm are fabricated on the basis of HTHP p-diamond and CVD i-diamond. The betavoltaic characteristics of the diamond structures are studied using a wide-aperture electron beam with an initial energy of 110 keV, partially scattered on the way to a converter by a 14-μm-thick aluminum layer and a 17-mm-thick air layer. The maximum generated power reached 2.18 mW (41 mW/cm2) with a conversion efficiency of 2-3%. [ABSTRACT FROM AUTHOR]

Dense multi-walled carbon nanotubes (CNTs) have been successfully fabricated on expanded perlite particles by the pyrolysis of a camphor–ferrocene mixture at 800 °C. Scanning electron microscopy images show that the CNTs’ growth is strongly affected by the specific surface area of perlite samples and it is more efficient in the case of perlite particles with a coarse surface and a high value of specific surface, likely due to the homogeneous dispersion of the catalyst. The optimum synthesized nanotubes have uniform outer diameters ranging between 25 and 50 nm, and a length of ∼40 μm. Transmission electron microscopy reveals a typical hollow nanotube structure with the majority of catalytic Fe particles located at the nanotube tips suggesting a tip-growth mechanism. HR-TEM images of individual nanotubes show that their external walls consist of about 50 carbon sheets. Finally, the synthesized CNTs were separated from the substrate, and the dielectric permittivity of a low density powder of nanotubes was measured at various temperatures and frequencies using the cavity perturbation method. [ABSTRACT FROM AUTHOR]

The demand for better tools for machining printed circuit boards (PCBs) is increasing due to the extensive usage of these boards in digital electronic products. This paper is aimed at optimizing coating type on micro drills in order to extend their lifetime in PCB machining. First, the tribotests involving micro crystalline diamond (MCD), nano crystalline diamond (NCD) and bare tungsten carbide (WC-Co) against PCBs show that NCD-PCB tribopair exhibits the lowest friction coefficient (0.35) due to the unique nano structure and low surface roughness of NCD films. Thereafter, the dry machining performance of the MCD- and NCD-coated micro drills on PCBs is systematically studied, using diamond-like coating (DLC) and TiAlN-coated micro drills as comparison. The experiments show that the working lives of these micro drills can be ranked as: NCDTiAlNDLCMCDbare WC-Co. The superior cutting performance of NCD-coated micro drills in terms of the lowest flank wear growth rate, no tool degradation (e.g. chipping, tool tipping) appearance, the best hole quality as well as the lowest feed force may come from the excellent wear resistance, lower friction coefficient against PCB as well as the high adhesive strength on the underneath substrate of NCD films. [ABSTRACT FROM AUTHOR]

In this paper, CVD diamond coatings are deposited on cemented carbides with 10 wt.% Co using amorphous SiO 2 and amorphous SiC interlayers. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Raman spectrum and X-ray diffraction (XRD) are carried out to characterize the microstructure and composition of as-deposited films. Moreover, the adhesion and cutting performance of as-fabricated diamond coatings are studied. Indentation tests show that the amorphous ceramic interlayers can enhance the adhesion between diamond films and WC–Co substrates. The cutting tests against zirconia indicate that the tools with amorphous ceramic interlayered diamond coatings exhibit improved cutting performance. The amorphous ceramic interlayers can improve the adhesive strength and wear endurance of diamond coatings on WC–10 wt.% Co substrates, which provide a viable way for adherent diamond coatings on cemented carbide tools with high cobalt content. [ABSTRACT FROM AUTHOR]

We report on the growth of high Mg content, high quality, wurtzite Mg x Zn 1− x O (MgZnO) epitaxial films using a pulsed metal organic chemical vapor deposition (PMOCVD) method. Series of MgZnO films with variable Mg concentration were deposited on bare and AlN coated sapphire substrates. The band gap of the films estimated using UV–visible transmission spectra ranges from 3.24 eV to 4.49 eV, corresponding to fraction of Mg between x =0.0 and x =0.51, as determined by Rutherford backscattering spectroscopy. The cathodoluminescence (CL) measurement has shown a blue-shift in the peak position of MgZnO with an increasing Mg content. No multi-absorption edges and CL band splitting were observed, suggesting the absence of phase segregation in the as grown films. The crystal structure and phase purity of the films were also confirmed by XRD analysis. Hall effect measurement in van der Pauw configuration was employed to evaluate the electrical properties of the films. With a rise in Mg incorporation into the ZnO lattice, the films became very resistive, consistent with the widening of the band gap. The AFM measurement on the films has shown a decreasing surface roughness with an Mg content. To the best of our knowledge, the current result shows the highest Mg content ( x =0.51), high quality, wurtzite MgZnO epitaxial film ever grown by MOCVD. The high Mg incorporation without phase separation is believed to be due to the non-equilibrium behavior of the PMOCVD in which the kinetic processes dominate the thermodynamic one. [ABSTRACT FROM AUTHOR]

ZnTe nanowires were grown in a large scale by tellurization of zinc sheets in a chemical vapor deposition (CVD) set-up. The zinc sheets were placed in three temperature zones in a tube furnace. Scanning electron microscope (SEM) images showed that, the ZnTe nanowires were grown with bigger diameter in the higher temperature. The phase and composition of the product were identified by X-ray diffraction (XRD) pattern and X-ray photoelectron spectra (XPS). The XPS results showed that, the Te concentration was higher for the sample that was placed in the higher temperature. In addition, these nanowires produced a strong photoluminescence (PL) emission peak in the green region and a weak peak in the red region of the electromagnetic spectrum. Furthermore, a comparison study between the XPS and PL was carried out to understand origin of the defect emission of ZnTe nanowires. [ABSTRACT FROM AUTHOR]

Three dimensional (3D) graphene foams have potential applications in high performance energy storage devices such as lithium-ion batteries and super capacitors. In this study, microcellular 3D graphene foams were fabricated via ambient pressure chemical vapor deposition (APCVD) with electroless plated nickel (Ni) foam templates. The microcellular Ni foam templates exhibit sufficient thermal stability for few layer graphene (FLG) growth in the APCVD process, yielding graphene foams with a pore size less than 100 µm, density of 0.0020 g cm −3 , and pore wall thickness of about 5 nm. The 3D graphene foam has a cellular morphology with a surface-to-volume ratio of 2.5×10 5 m 2 m −3 . [ABSTRACT FROM AUTHOR]

Background: Conductive biomaterials are an ideal biosubstrate for modifying cellular behaviors by conducting either internal or external electrical signals. In this study, based on a simple-preparation graphite exfoliation method in organic reagent, a nonfunctionalized graphene nanosheet film (NGNF) with high conductivity and large size was simply fabricated through spraying coating. The biocompatibility of the NGNF was carefully tested with primary cortical neuron cells, and its biocompatibility properties were compared with a chemical vapor deposition (CVD) graphene film. Methods: Nonfunctionalized graphene nanosheet (NGN) was first exfoliated from graphite with a flat-tip ultrasonicator probe, and then spray-coated onto glass slide substrate to form the film. The morphology of NGNF was observed with light microscopy and SEM. The morphology and neuronal network formation of primary cortical neuron cells onto NGNF, as shown by DAPI and Alexa Fluor® 488 staining, were observed with fluorescent microscopy. Cell viability and proliferation were measured with MTT. Results: NGNF had better cell biocompatibility than CVD graphene film. MTT test showed that NGNF exhibited no cytotoxicity. According to neuronal network formation at 7 days of cell culture, primary neuron cells aggregated into 50-µm "nuclei"; the average neurite number and length were 3 and 100 µm, respectively. However, these values were almost doubled after 14 days of cell culture. Conclusions: These results may improve the use of NGNF as a conductive scaffold for nerve regeneration. [ABSTRACT FROM AUTHOR]

In order to provide with novel composites with high specific surface area for hydrogen storage, FeNiCr-carbon composites were prepared by an alcohol chemical vapor deposition (ACCVD) method with methanol as a carbon source, wherein the abbreviation FeNiCr denoted powdery mixture of hydrogenated Fe, Ni and Cr. After the ACCVD synthesis, the composites were optionally ground to expose inner sorption sites. The peak temperature of hydrogen desorption from as-prepared FeNiCr-carbon composite hydrogenated at 653 K under 1.1 MPa of hydrogen was 723 K, as recorded by temperature programmed desorption (TPD). The peak temperature of hydrogen desorption from ground FeNiCr-carbon composite hydrogenated under the same conditions was as low as 423 K. HD molecules were detected by TPD, after the ground FeNiCr-carbon composite was similarly hydrogenated at 653 K under mixed H 2 plus D 2 gas. Such was also the case, after the ground composite was hydrogenated at room temperature. It was evidenced that atomic hydrogen took part in hydrogen sorption by the ground composite. The maximum hydrogen concentrations of the FeNiCr-carbon composites were 0.59 mass% and 1.16 mass%, before and after grinding, respectively, at 77 K under 0.77 MPa of hydrogen. [ABSTRACT FROM AUTHOR]

A modified fluidized bed reactor is developed to homogenously coat micrometer-sized particles with reactive polymer films using CVD. This technique is found to be rapid (~30min per batch) and scalable (up to 1g particles), and can create homogenous coatings on microparticles down to 10 mm in diameter. By tuning critical variables, such as working pressure and the carrier gas flow rate, full coverage of a reactive polymer film can be realized. Janus particles are synthesized and can be visualized via fluorescence microscopy. [ABSTRACT FROM AUTHOR]

We demonstrate high-performance field-effect transistors consisting of hybrid graphene/fluoropolymer films by investigating the molecular interaction with strong carbon–fluorine dipoles and hydrophobic surface characteristics. A simple and reproducible solution-coating method on a chemical vapor deposition grown monolayer graphene was employed with fluoropolymer, amorphous CYTOP, and polycrystalline poly(vinylidene fluoride-co-trifluoroethylene) as an interacting layer. All of the key device metrics, including field-effect mobility, Dirac voltage, residual carrier concentration, ON–OFF current ratio, and electron–hole transport symmetry, were substantially improved. Significantly, the Dirac voltage shifted in both directions toward zero, regardless of its initial positions of the Dirac voltage after molecular encapsulation with fluoropolymers. We also demonstrate the improved stability of hybrid graphene/fluoropolymer films that possesses a hydrophobic surface through repelling hydroxyl (–OH) functional groups from the graphene surface. [ABSTRACT FROM PUBLISHER]

Rotor–stator mechanisms, which are the key components in flotation cells, serve to mix the slurry and the air bubbles. The optimization of rotor–stator mechanisms improves the metallurgical performance and decreases the energy consumption of a flotation cell. The angle of the impeller blades, which is an important aspect of the design of rotor–stator mechanisms, significantly impacts the pumping and power consumption of a flotation cell. The flow pattern of a flotation cell with different impellers was investigated by combining PIV measurements and CFD simulation. PIV and CFD also revealed the flow field characteristics of the test cross-section under the impeller. The PIV measurement results agree with the CFD prediction results, and the backward impeller, radial impeller and forward impeller all produce similar flow patterns with upper and lower circulations. The velocity-area method, which integrates the axial velocity in the area of the selected section using CFD simulation, can be used to calculate the impeller circulation volume. The circulation volumes of the backward impeller and radial impeller are almost identical and are approximately 7% larger than that of the forward impeller. Thus, the backward impeller and radial impeller are better choices when large-volume circulation is needed. Based on the CFD simulation, the power consumption of the backward impeller is 13% less than that of the radial impeller and 19% less than that of the forward impeller. The backward impeller was shown to save more energy than the other two impellers, and it can decrease the operation cost for concentrators. This study aids the structural design of impellers for KYF flotation cells. [ABSTRACT FROM AUTHOR]

Low-energy ion scattering (LEIS)is known for its extreme surfacesensitivity, as it yields a quantitative analysis of the outermostsurface as well as highly resolved in-depth information for ultrathinsurface layers. Hence, it could have been generally considered tobe a suitable technique for the analysis of graphene samples. However,due to the low scattering cross section for light elements such ascarbon, LEIS has not become a common technique for the characterizationof graphene. In the present study we use a high-sensitivity LEIS instrumentwith parallel energy analysis for the characterization of CVD graphenetransferred to thermal silica/silicon substrates. Thanks to its highsensitivity and the exceptional depth resolution typical of LEIS,the graphene layer closure was verified, and different kinds of contaminantswere detected, quantified, and localized within the graphene structure.Utilizing the extraordinarily strong neutralization of helium by carbonatoms in graphene, LEIS experiments performed at several primary ionenergies permit us to distinguish carbon in graphene from that innongraphitic forms (e.g., the remains of a resist). Furthermore, metalimpurities such as Fe, Sn, and Na located at the graphene–silicainterface (intercalated) are detected, and the coverages of Fe andSn are determined. Hence, high-resolution LEIS is capable of bothchecking the purity of graphene surfaces and detecting impuritiesincorporated into graphene layers or their interfaces. Thus, it isa suitable method for monitoring the quality of the whole fabricationprocess of graphene, including its transfer on various substrates. [ABSTRACT FROM AUTHOR]

Evolution of residual stress and its components with increasing temperature in chemical vapor deposited (CVD) diamond films has a crucial impact on their high temperature applications. In this work we investigated temperature dependence of stress in CVD diamond film deposited on Si(100) substrate in the temperature range of 30 °C to 480 °C by Raman mapping measurement. Raman shift of the characteristic diamond band peaked at 1332 cm-1 was studied to evaluate the residual stress distribution at the diamond surface. A new approach was applied to calculate thermal stress evolution with increasing tempera­ture by using two commonly known equations. Comparison of the residts obtained from the two methods was presented. The intrinsic stress component was calculated from the difference between average values of residual and thermal stress and then its temperature dependence was discussed. [ABSTRACT FROM AUTHOR]