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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]

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]

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]

The nanocrystalline diamond films (coatings) were prepared using the plasma enhanced chemical vapor deposition (PECVD) technique. In this method, direct current (DC) glow discharge in the crossed E/H fields was used to activate the gas phase. The diamond coatings were deposited from the working gas mixture CH4/H2 with addition of nitrogen in various concentrations. It was ascertained that addition of N2 to the working gas mixture leads to reduction in the sizes of diamond grains as well as to the substantial decrease in the resistivity of the studied films. The electrophysical data are in good agreement with the changes induced by varying the N2 content in the Raman scattering spectra. The increase in the N2 concentration causes significant lowering of the crystalline diamond related peak and increase in the intensity of the peaks related to the sp2-bonded carbon. These changes in the spectra indicate significant disordering of the structure of prepared films and its uniformity in the nanodiamond film volume. With the great possibility, it is associated with a decrease in the sizes of diamond crystalline grains and tendency of NCD film to amorphization. [ABSTRACT FROM AUTHOR]

Steel is the most widely used material in engineering for its cost/performance ratio and coatings are routinely applied on its surface to further improve its properties. Diamond coated steel parts are an option for many demanding industrial applications through prolonging the lifetime of steel parts, enhancement of tool performance as well as the reduction of wear rates. Direct deposition of diamond on steel using conventional chemical vapour deposition (CVD) processes is known to give poor results due to the preferential formation of amorphous carbon on iron, nickel and other elements as well as stresses induced from the significant difference in the thermal expansion coefficients of those materials. This article reports a novel approach of deposition of nanocrystalline diamond coatings on high-speed steel (M42) substrates using a multi-structured molybdenum (Mo) - tungsten (W) interlayer to form steel/Mo/Mo-W/W/diamond sandwich structures which overcome the adhesion problem related to direct magnetron sputtering deposition of pure tungsten. Surface, interface and tribology properties were evaluated to understand the role of such an interlayer structure. The multi-structured Mo-W interlayer has been proven to improve the adhesion between diamond films and steel substrates by acting as an effective diffusion barrier during the CVD diamond deposition [ABSTRACT FROM AUTHOR]

Abstract: Diamond coatings on hardmetal tools are well-established and CVD-diamond coatings can significantly prolong the lifetime of tools used for cutting and milling of non-ferrous materials, e.g. Al(Si) alloys, graphite and plastics. A general problem is the reproducibility of diamond coatings with sufficient adhesion on the substrate surface, which is affected by the Co binder phase of the hardmetal. As a result some of the coatings fail due to delamination during heavy duty machining. To overcome this adhesion problem diamond was deposited on various CVD interlayers with a rough surface, i.e. Ti(C,N), (Al,Ti)N, Ti(C,N)/TiC and Ti(C,N)/SiC. Due to the roughness of the interlayers the adhesion of the diamond coatings on the substrate surface is improved. Furthermore, the deposition was varied from well-facetted crystalline diamond to nano-crystalline diamond (NCD) by adding argon to the reaction gas. Some of the diamond coatings show a sufficient adhesion and cutting tests for industrial applications are in process. [Copyright &y& Elsevier]

Abstract: In the present study, adopting the optimized deposition parameters determined by orthogonal simulations, high-quality boron-doped and undoped composite diamond (BD–UCD) films with uniform thickness are deposited on both the inner hole and conical surfaces of the SiC nozzles used in the spray drying equipment. The erosion behavior of the novel diamond film is firstly evaluated in an air–sand erosion rig, with single-layer boron-doped diamond (BDD) and undoped diamond films as comparisons. Thereafter, the erosive wear performance of the BD–UCD coated nozzles is further studied under the industrial condition. The results show that the BD–UCD film exhibits an apparent increase in the erosion resistance over the other two types of diamond films. The mechanism responsible is found to be that the surface undoped diamond layer in the BD–UCD film has outstanding hardness, and boron doping can improve the adhesion between the underlying BDD layer and the substrate. Moreover, under the industrial condition, the ethylene catalytic cracking catalyzers produced with the BD–UCD coated nozzles have much more stable quality than those produced with the uncoated nozzles owing to the aperture stability of the inner hole, further proving the high erosion resistance of the BD–UCD protecting coatings. [Copyright &y& Elsevier]

The tribological response of multilayer micro/nanocrystalline diamond coatings grown by the hot filament CVD technique is investigated. These multigrade systems were tailored to comprise a starting microcrystalline diamond (MCD) layer with high adhesion to a silicon nitride (Si3N4) ceramic substrate, and a top nanocrystalline diamond (NCD) layer with reduced surface roughness. Tribological tests were carried out with a reciprocating sliding configuration without lubrication. Such composite coatings exhibit a superior critical load before delamination (130–200N), when compared to the mono- (60–100N) and bilayer coatings (110N), considering ∼10µm thick films. Regarding the friction behaviour, a short-lived initial high friction coefficient was followed by low friction regimes (friction coefficients between 0.02 and 0.09) as a result of the polished surfaces tailored by the tribological solicitation. Very mild to mild wear regimes (wear coefficient values between 4.1×10−8 and 7.7×10−7 mm3 N−1 m−1) governed the wear performance of the self-mated multilayer coatings when subjected to high-load short-term tests (60–200N; 2h; 86m) and medium-load endurance tests (60N; 16h; 691m). [ABSTRACT FROM AUTHOR]

Abstract: Conditioning of polishing pads during chemical mechanical planarization (CMP) of wafers is a critical process for maintaining productivity and quality control in the semiconductor industry. This investigation aims at developing a CMP diamond conditioner of a new concept and hence improving the conditioning performance. The novel diamond conditioner was fabricated by coating diamond films on a Si3N4 substrate with regularly patterned protrusions. Thanks to the uniform distribution and constant height of protrusions, the novel conditioner exhibited superior performance and durability over the current conditioner, which contains bonded diamond grits of various sizes and shapes with unequal heights. Characterization of the developed novel diamond CVD conditioner has also been made. [Copyright &y& Elsevier]

Abstract: Water lubricated tribological systems involving chemical vapour deposited (CVD) diamond coatings are appealing to many practical situations, namely in metalworking and fluid handling applications. The motivation behind the present study lies in insufficient knowledge on the behaviour of these water-based lubricated tribosystems especially under high loads. The microwave plasma chemical vapour deposition technique was used to coat dense Si3N4 substrates from CH4–H2 gas mixtures, setting adequate deposition parameters during 2.5h, resulting in a film thickness around 15μm. Self-mated planar reciprocating sliding ball-on-flat wear tests were performed up to 16h (690m of sliding distance) with normal applied load ranging from 70N to 160N. SEM and AFM characterisation techniques were used to identify the prevailing wear mechanisms. The worn surfaces exhibit a polished appearance resulting from diamond asperities abrasion on the counterface combined with the action of nanometric debris. Some longitudinal wear grooves along the sliding direction are the result of two-body abrasive action of larger debris spawn from the truncation of aggregates of crystals in the first steps of sliding. A steady-state sliding regime sets for almost the test full duration, with a very low friction coefficient in the range 0.04–0.05 and a wear coefficient of about 10−8 mm3 N−1 m−1. Partial film wear-out was found at a threshold load of 160N, however without seriously affecting the tribosystem performance. [Copyright &y& Elsevier]

The machining of advanced materials is challenging the tooling technology. To cope this, new cutting materials and geometries are developed. In this case, four types of silicon nitride based ceramics are investigated after coating with CVD-diamond for the use as ceramic end mills. To assess the wear resistance, model wear tests and damage evaluation were carried out and evaluated. After subsequent summary of the results, ceramic and cemented carbide substrate were selected for milling of glass and carbon fiber reinforced plastic (GFRP/CFRP) The determined force distribution and wear properties of the tools are presented and discussed. The diamond coated substrates are qualified by their wear profile and the measured constant cutting forces for use in the machining of GFRP/CFRP. Finally, the crack formation progress for diamond coated silicon nitrides when machining glass and carbon fiber reinforced plastics was demonstrated. [ABSTRACT FROM AUTHOR]

The wear of the AFM tips has significant implications on the accuracy and throughput of the tip-based nanomanufacturing processes. Ultrananocrystalline diamond (UNCD) atomic force microscopy (AFM) tips that exhibit significantly lower wear rates compared to silicon and silicon nitride tips during the AFM application carry a strong potential to be effectively used during tip-based nanomanufacturing. In this paper, we present an experimental analysis of the wear of UNCD AFM tips during rotating tip-based mechanical nanomanufacturing (nanomilling). The diamond AFM tips are used as the nanotools to mechanically remove material from silicon and copper surfaces. The geometry of the tips is directly measured through non-contact AFM at various time points of the process. The acquired AFM images are then processed to quantify the progression of the tip wear in terms of wear volume, wear area, and change in tip radius and in tip height. The results of the analysis showed that the tips undergo two-phase wear process that consists of an early rapid break-in phase followed by a gradual steady-state phase. The wear rates experienced during nanomilling of silicon are shown to be more than an order of magnitude higher than those of copper. The analysis of the repeatability of the tip wear indicates that, for nominally identical process conditions and tip geometries, the tips could exhibit considerable variation in wear rates, particularly during the break-in phase. Without making any attempt on optimizing the process conditions, a cutting length of more than 240 mm is nanomilled at a constant depth of 150 nm on copper surfaces, within the life of a single nanotool. [ABSTRACT FROM AUTHOR]