Josephus Gerardus Buijnsters

CVD diamond deposition on steel using arc-plated chromium nitride interlayers

This paper reports on hot filament CVD diamond deposition onto steel using arc-plated chromium nitride (CrN) as the interlayer. Direct deposition of diamond onto steel leads to the formation of a non-adhering layer of graphitic soot covered by poor-quality diamond. However, if arc-plated CrN coatings with a thickness of 2.5 μm are used, diamond formation takes place. Adherent and good-quality diamond coatings are obtained after several hours of deposition at a substrate temperature as low as 650 °C. Micro-Raman spectroscopy, scanning electron microscopy, X-ray diffraction and EDAX analysis have been employed to study the phases, morphology, composition, quality and residual stresses of the grown diamond layers and the modified substrate interlayers. The Scotch tape test is used to assess the adhesion of the diamond coatings.

Diffusion-modified boride interlayers for chemical vapour deposition of low-residual-stress diamond films on steel substrates

The feasibility of using a boriding pretreatment for the chemical vapour deposition (CVD) of adherent, low-residual-stress diamond films on ferritic tool and AISI type 316 austenitic stainless steels was investigated. The steel samples were borided by means of a pack cementation process at a temperature of 950 8C using an interrupted thermal cycling process. Boriding of the alloy steels results in a very high surface hardness of approximately 3780 VHN due to the precipitation of alloy borides such as chromium boride in the predominantly FeBand yor Fe Bcase. The boriding conditions, and hence the microstructural state of the 2 as-borided steels, was found to have a strong influence on the diamond film characteristics, particularly on the adherence. Detailed characterisation of the as-borided steels, as well as the deposited diamond films and interlayer modification during the CVD process, is discussed based on scanning electron microscopy, X-ray diffraction and micro-Raman spectroscopy investigations. Under optimised conditions, adherent and continuous diamond films of good quality have been obtained on both the ferritic tool and austenitic stainless steels. In the case of borided surface structures without the presence of a FeBphase, diffusion-modified gradient microstructures were found to accommodate efficiently the high thermal stress expected between the steel substrate and the diamond film, resulting in low-residual-stress films. 2003 Elsevier Science B.V. All rights reserved.

Correlation of trans-Lycopene Measurements by the HPLC Method with the Optothermal and Photoacoustic Signals and the Color Readings of Fresh Tomato Homogenates

The trans-lycopene content of fresh tomato homogenates was assessed by means of the laser photoacoustic spectroscopy, the laser optothermal window, micro-Raman spectroscopy, and colorimetry; none of these methods require the extraction from the product matrix prior to the analysis. The wet chemistry method (high-performance liquid chromatography) was used as the absolute quantitative method. Analytical figures of merit for all methods were compared statistically; best linear correlation was achieved for the chromaticity index a* and chroma C*.

Morphology and growth mechanism of multiply twinned AgBr and AgCl needle crystals

Abstract In this study the morphology and growth mechanism of AgX (X=Cl, Br) needle crystals will be revealed. The silver halide needles are grown by two different techniques. AgBr needles are grown with an extractive crystallization in a dimethylsulfoxide–water mixture and AgCl needles are grown from the vapor phase. All needles contain nonparallel twin planes. The morphology of the AgBr needles grown from dimethylsulfoxide is the same as the needles grown in the industrial precipitation process in water. The side faces of these solution grown needles are built up of relatively slowly growing {1xa01xa01} faces. Both needle tops are composed of three relatively fast growing {1xa00xa00} faces making a ridge structure. The vapor-grown needles have two different morphologies. For both types the side faces consist of four {1xa01xa01} and two {1xa00xa00} faces. All {1xa01xa01} faces are linked via twin planes to a fast growing {1xa00xa00} face. The preferential unidirectional growth of all needles is caused by cross-twinning. The preferential growth occurs along the intersection line of the twin planes. Between the twin planes a rough growing face appears on the needle top. This face is capable of increasing the growth rate of the other top faces owing to the substep mechanism.

Gas nitriding of chromium in NH3-H2 atmosphere

Abstract Nitriding behaviour of pure chromium in an NH 3 –H 2 atmosphere is discussed. Chromium samples were nitrided for various times (1, 4, 24, 48, 72, 120 and 142 h) at 800xa0°C. The nitridation is accompanied by an increase in surface porosity, which leads to an enlarged surface brittleness. Vickers microhardness measurements along the direction of nitrogen diffusion show an overall increase in hardness as a result of the nitriding process resulting in a surface hardness as high as about 1200–1400 Vickers. X-ray diffraction studies reveal the formation of Cr 2 N, CrN and Cr(N) phases upon nitriding. Scanning electron microscopy and energy dispersive X-ray analysis (EDAX) show an increasing fraction of the CrN phase formed at the surface with increasing nitriding times. EDAX line profile analysis of the specimen nitrided for 120 h shows a three-layered structure. Though the surface layer and the second layer adjacent to it, both consist of a mixture of CrN and Cr 2 N phases, the fraction of CrN is much higher in the surface layer. Nitridation of Cr 2 N is suggested as the possible mechanism for CrN formation at the surface with increasing nitriding times, for the nitriding parameters chosen in the present study.

Direct photothermal techniques for rapid quantification of total anthocyanin content in sour cherry cultivars

The analytical performance of the newly proposed laser-based photoacoustic spectroscopy (PAS) and of optothermal window (OW) method for quantification of total anthocyanin concentration (TAC) in five sour cherry varieties is compared to that of the spectrophotometry (SP). High performance liquid chromatography (HPLC) was used to identify and quantify specific anthocyanins. Both, PAS and OW are direct methods that unlike SP and HPLC obviate the need for the extraction of analyte. The outcome of the study leads to the conclusion that PAS and OW are both suitable for quick screening of TAC in sour cherries. The correlation between the two methods and SP is linear with R(2)=0.9887 for PAS and R(2)=0.9918 for OW, respectively. Both methods are capable of the rapid determination of TAC in sour cherries without a need for a laborious sample pretreatment.

Atomic force microscopy studies on the surface morphology of {1 1 1} tabular AgBr crystals

Abstract Both ex situ and in situ atomic force microscopy have been applied to study the {1xa01xa01} and {1xa00xa00} surfaces of tabular silver bromide crystals grown from dimethyl sulphoxide–water solutions. This resulted in observations of monosteps, macrosteps, etch pits, pinning of steps and nucleated crystals showing twin planes. These examinations indicate that the growth and dissolution of both the {1xa00xa00} and the polar {1xa01xa01} faces occur via steps in many configurations. The registered 40-nm distance between the parallel twin planes of the nucleated crystals agrees with transmission electron microscopy measurements done on tabular crystals grown by the industrial double-jet precipitation method.

Diamond deposition on modified silicon substrates: Making diamond atomic force microscopy tips for nanofriction experiments

Fine-crystalline diamond particles are grown on standard Si atomic force microscopy tips, using hot filament-assisted chemical vapor deposition. To optimize the conditions for diamond deposition, first a series of experiments is carried out using silicon substrates covered by point-topped pyramids as obtained by wet chemical etching. The apexes and the edges of the silicon pyramids provide favorable sites for diamond nucleation and growth. The investigation of the deposited polycrystallites is done by means of optical microscopy, scanning electron microscopy and micro-Raman spectroscopy. The resulting diamond-terminated tips are tested in ultra high vacuum using contact-mode atomic force microscope on a stepped surface of sapphire showing high stability, sharpness, and hardness.

Chemical and physical sputtering effects on the surface morphology of carbon films grown by plasma chemical vapor deposition

We have studied the influence of chemical and physical sputtering on the surface morphology of hydrogenated carbon films deposited on silicon substrates by bias-enhanced electron cyclotron resonance chemical vapor deposition. Atomic force microscopy based power spectrum density (PSD) and roughness analysis have been used to investigate the film morphology. This study has been possible due to the appropriate choice of the experimental variables, in particular, gas mixture, resulting in either nitrogen-free (a-C:H) or nitrogenated carbon (a-CN:H) films, and substrate bias (Vb). Under these conditions, chemical sputtering is present for a-CN:H deposition but it is negligible for a-C:H film growth, while physical sputtering processes appear for both systems for Vb≤−85u2002V. When physical sputtering does not operate, the film growth with simultaneous chemical sputtering leads to a characteristic a-CN:H granular surface morphology. Furthermore, PSD analysis reveals that a spatial correlation of the a-CN:H film sur...

The effect of nitrogen addition during flame deposition of diamond as studied by solid-state techniques

Abstract The influence of nitrogen addition on the properties of oxyacetylene flame-deposited diamond has been studied by means of X-ray diffraction (XRD), micro-Raman spectroscopy and cathodoluminescence spectroscopy (CL). A morphological transition reported in earlier work was found to have a major influence on the diamond properties. XRD indicated the presence of a molybdenum carbide layer in between the diamond film and the molybdenum substrate. Thermal stress proved to be the dominant source of layer stress, which in turn was found to be the main cause for the width of the diamond Raman line. In the fraction of the Raman signal that is not due to the diamond Raman peak a drop was observed that can be ascribed to a decrease in the sp2 carbon-related luminescence. The CL measurements showed that, for the present series of samples, blue band A luminescence is stronger from {111} than from {001} facets. Diamond film with the optimal combination of fast growth rate, good surface coverage, high crystalline quality, rather good 〈001〉 texture and zero net stress was grown with 10 sccm of nitrogen.