Abstract In this study, we have employed infrared (IR) absorption spectroscopy, visible Raman spe... more Abstract In this study, we have employed infrared (IR) absorption spectroscopy, visible Raman spectroscopy, and x-ray absorption near edge structure (XANES) to quantify the hydrogen (H) content in hydrogenated amorphous carbon (aC: H) films. aC: H films with a hydrogen content varying from 29 to 47 at.% have been synthesized by electron cyclotron resonance chemical vapor deposition at low substrate temperatures (≪ 120 C) applying a wide range of bias voltage, V b,(-300 V≪ V b≪+ 100 V).
Poly (vinylidene fluoride) (PVDF) composites with different types of nanodiamond (ND) particles w... more Poly (vinylidene fluoride) (PVDF) composites with different types of nanodiamond (ND) particles were produced by solvent casting. The variations of the morphological, structural, optical, thermal and electrical properties of the composites were studied as a function of nanofiller type (without and with air oxidation treatment) and concentration (in the range 0.1–1 wt%). No noticeable differences were found in the polymer crystallization process, the processing conditions and the filler determining the morphology and structure of the polymer. Nevertheless, ND nanofillers were useful for the tailoring of the optical properties, and also slightly contributed to the thermodynamic stability of the samples. An increase in the dielectric constant (∼2) of the ND composites, while maintaining constant the dielectric losses, was observed, independently of the filler concentration. On the other hand, solvent casted porous composites crystallize mainly in the electroactive γ-phase of PVDF. Those composite membranes were evaluated with pre-osteoblast culture tests and these revealed that the inclusion of ND nanoparticles does not induce cytotoxicity on the samples. Taking advantage of the properties of the polymer for cell culture and with the potential of the ND filler for protein functionalization and drug delivery, it is concluded that NDs/PVDF composites are a suitable platform for biomedical applications.
This is a pioneering study on the synthesis and application of composites based on micro- and nan... more This is a pioneering study on the synthesis and application of composites based on micro- and nanodiamonds for the photocatalytic degradation of environmental water pollutants. Micro- and nanodiamond powders (with particle sizes of 1–3 μm and 2–10 nm, respectively) were combined with TiO2, by varying the carbon-phase content, and tested as composite photocatalysts for the degradation of diphenhydramine, which is a pharmaceutical water pollutant, under near-UV/Vis irradiation. These composites exhibited higher photocatalytic activity than the respective bare materials. In addition, composites prepared with pristine nanodiamonds were always more active than those prepared with microdiamonds of the same carbon content. A significant enhancement in the photocatalytic performance was observed on preparation of the composite with 15 wt % of nanodiamonds oxidised in air at 703 K; these oxidised nanodiamonds contained mainly carboxylic anhydrides, lactones, phenols and, to a lesser extent, carbonyl/quinone groups on their surface.
ABSTRACT Nitriding behaviour of pure chromium in an NH3–H2 atmosphere is discussed. Chromium samp... more ABSTRACT Nitriding behaviour of pure chromium in an NH3–H2 atmosphere is discussed. Chromium samples were nitrided for various times (1, 4, 24, 48, 72, 120 and 142 h) at 800 °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 Cr2N, 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 Cr2N phases, the fraction of CrN is much higher in the surface layer. Nitridation of Cr2N 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.
The analytical performance of the newly proposed laser-based photoacoustic spectroscopy (PAS) and... more 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
... 1, each corner of sample PD1 has a large spot, which is actually a very big multi-twinned cry... more ... 1, each corner of sample PD1 has a large spot, which is actually a very big multi-twinned crystal of mm range size. As an example, Fig. 2b shows the much bigger multi-twinned crystal grown in the left corner as compared to the relatively smaller crystals grown along the edges. ...
ABSTRACT In this study, the use of thin Si interlayers (35–150 nm) for promoting diamond depositi... more ABSTRACT In this study, the use of thin Si interlayers (35–150 nm) for promoting diamond deposition onto steel is investigated. The diamond films are deposited by hot filament CVD onto AISI type 316 stainless and high-speed steels. Single stage deposition at substrate temperatures ranging from as low as 475 to 750 °C is found to result only in non-continuous films with low number densities of diamond crystallites. A composite film of diamond and carbides is formed at intermediate temperatures of about 650 °C. It is believed that the formation of iron silicide phases at the exposed steel substrate surfaces leads to diffusion barriers for free iron from the steel matrix, so that graphitic soot formation is significantly avoided.Utilizing a two-stage deposition process, the density and uniformity of the deposited diamond films areincreased and a nearly continuous cauliflower shaped diamond film is obtained. Micro-Raman spectros-copy, scanning electron microscopy and X-ray diffraction techniques are employed to study the phases, morphology, composition, quality and residual stresses of the grown diamond layers.
Both ex situ and in situ atomic force microscopy have been applied to study the {111} and {100} s... more Both ex situ and in situ atomic force microscopy have been applied to study the {111} and {100} 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 {100} and
In this study the morphology and growth mechanism of AgX (X=Cl, Br) needle crystals will be revea... more 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
Abstract In this study, we have employed infrared (IR) absorption spectroscopy, visible Raman spe... more Abstract In this study, we have employed infrared (IR) absorption spectroscopy, visible Raman spectroscopy, and x-ray absorption near edge structure (XANES) to quantify the hydrogen (H) content in hydrogenated amorphous carbon (aC: H) films. aC: H films with a hydrogen content varying from 29 to 47 at.% have been synthesized by electron cyclotron resonance chemical vapor deposition at low substrate temperatures (≪ 120 C) applying a wide range of bias voltage, V b,(-300 V≪ V b≪+ 100 V).
Poly (vinylidene fluoride) (PVDF) composites with different types of nanodiamond (ND) particles w... more Poly (vinylidene fluoride) (PVDF) composites with different types of nanodiamond (ND) particles were produced by solvent casting. The variations of the morphological, structural, optical, thermal and electrical properties of the composites were studied as a function of nanofiller type (without and with air oxidation treatment) and concentration (in the range 0.1–1 wt%). No noticeable differences were found in the polymer crystallization process, the processing conditions and the filler determining the morphology and structure of the polymer. Nevertheless, ND nanofillers were useful for the tailoring of the optical properties, and also slightly contributed to the thermodynamic stability of the samples. An increase in the dielectric constant (∼2) of the ND composites, while maintaining constant the dielectric losses, was observed, independently of the filler concentration. On the other hand, solvent casted porous composites crystallize mainly in the electroactive γ-phase of PVDF. Those composite membranes were evaluated with pre-osteoblast culture tests and these revealed that the inclusion of ND nanoparticles does not induce cytotoxicity on the samples. Taking advantage of the properties of the polymer for cell culture and with the potential of the ND filler for protein functionalization and drug delivery, it is concluded that NDs/PVDF composites are a suitable platform for biomedical applications.
This is a pioneering study on the synthesis and application of composites based on micro- and nan... more This is a pioneering study on the synthesis and application of composites based on micro- and nanodiamonds for the photocatalytic degradation of environmental water pollutants. Micro- and nanodiamond powders (with particle sizes of 1–3 μm and 2–10 nm, respectively) were combined with TiO2, by varying the carbon-phase content, and tested as composite photocatalysts for the degradation of diphenhydramine, which is a pharmaceutical water pollutant, under near-UV/Vis irradiation. These composites exhibited higher photocatalytic activity than the respective bare materials. In addition, composites prepared with pristine nanodiamonds were always more active than those prepared with microdiamonds of the same carbon content. A significant enhancement in the photocatalytic performance was observed on preparation of the composite with 15 wt % of nanodiamonds oxidised in air at 703 K; these oxidised nanodiamonds contained mainly carboxylic anhydrides, lactones, phenols and, to a lesser extent, carbonyl/quinone groups on their surface.
ABSTRACT Nitriding behaviour of pure chromium in an NH3–H2 atmosphere is discussed. Chromium samp... more ABSTRACT Nitriding behaviour of pure chromium in an NH3–H2 atmosphere is discussed. Chromium samples were nitrided for various times (1, 4, 24, 48, 72, 120 and 142 h) at 800 °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 Cr2N, 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 Cr2N phases, the fraction of CrN is much higher in the surface layer. Nitridation of Cr2N 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.
The analytical performance of the newly proposed laser-based photoacoustic spectroscopy (PAS) and... more 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
... 1, each corner of sample PD1 has a large spot, which is actually a very big multi-twinned cry... more ... 1, each corner of sample PD1 has a large spot, which is actually a very big multi-twinned crystal of mm range size. As an example, Fig. 2b shows the much bigger multi-twinned crystal grown in the left corner as compared to the relatively smaller crystals grown along the edges. ...
ABSTRACT In this study, the use of thin Si interlayers (35–150 nm) for promoting diamond depositi... more ABSTRACT In this study, the use of thin Si interlayers (35–150 nm) for promoting diamond deposition onto steel is investigated. The diamond films are deposited by hot filament CVD onto AISI type 316 stainless and high-speed steels. Single stage deposition at substrate temperatures ranging from as low as 475 to 750 °C is found to result only in non-continuous films with low number densities of diamond crystallites. A composite film of diamond and carbides is formed at intermediate temperatures of about 650 °C. It is believed that the formation of iron silicide phases at the exposed steel substrate surfaces leads to diffusion barriers for free iron from the steel matrix, so that graphitic soot formation is significantly avoided.Utilizing a two-stage deposition process, the density and uniformity of the deposited diamond films areincreased and a nearly continuous cauliflower shaped diamond film is obtained. Micro-Raman spectros-copy, scanning electron microscopy and X-ray diffraction techniques are employed to study the phases, morphology, composition, quality and residual stresses of the grown diamond layers.
Both ex situ and in situ atomic force microscopy have been applied to study the {111} and {100} s... more Both ex situ and in situ atomic force microscopy have been applied to study the {111} and {100} 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 {100} and
In this study the morphology and growth mechanism of AgX (X=Cl, Br) needle crystals will be revea... more 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
Poly(vinylidene fluoride) (PVDF) composites with different carbonaceous nanofillers, prepared by ... more Poly(vinylidene fluoride) (PVDF) composites with different carbonaceous nanofillers, prepared by solution casting, were studied their chemical, mechanical, electrical and electro-mechanical properties evaluated. Few-layer graphene (FLG) nanoplatelets (G-NPL), graphene oxide (GO) and reduced graphene oxide (rGO) and single-walled carbon nanohorns (SWCNH)) were found to have a strong influence in the overall properties of the composites prepared with up to 5 wt% nanofiller contents. The mechanical strain of carbonaceous nanofillers/PVDF composites decreases from 15% to near 5% of maximum strain. The electrical percolation threshold depends on the nanofiller type, being below 1 wt% for rGO and near 2 wt% for the remaining nanofillers. The electrical conductivity shows a maximum increase of nine orders of magnitude, from s z 5 Â 10 À11 S/m of pure PVDF to s z 1 Â 10 À2 S/m for rGO/PVDF composites with 5 wt% nanofillers. The conduction mechanism being related to hopping between the carbonaceous nanofillers for concentrations higher than the percolation threshold. Furthermore, the composites show electro-mechanical properties, except for G-NPL materials, with rGO/PVDF composites with 5 wt% nanofiller content showing higher Gauge factor (GF) values, reaching GFz 11 for deformations between 0.5 and 2 mm in 4-point bending experiments. These results demonstrate the suitability of the composites for strain sensing applications.
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Papers by J.G. Buijnsters