Electrodeposition of Ni-P composite coatings: a review

Ni-P coatings produced by electrodeposition have important mechanical, tribological and electrochemical properties. They can also exhibit catalytic activity and beneficial magnetic behaviour. With subsequent thermal treatment, the hardness of such Ni-P coatings can approach or exceed that of hard Cr coatings. Electrochemical codeposition of homogeneously dispersed second phase particles within the Ni-P matrix can enhance deposit properties and meet the challenging demands on modern engineering coatings. A general overview of research work on the electrodeposition of Ni-P composite coatings containing included ceramic or polymeric particles is provided. Advances in research into Ni-P composite layers reinforced by SiC, B4C, WC, Al2O3, SiO2, TiO2, CeO2, MWCNT, MoS2, WS2, TiN, hexagonal BN, PTFE and their combinations are considered. Major models proposed for the codeposition of particles, the influence of bath hydrodynamics and control of operational parameters are illustrated by examples. Important trends are highlighted and opportunities for future R & D are summarised

Electrodeposition of Ni-P alloy coatings: a review

Ni[sbnd]P coatings are extensively employed in engineering, owing to their mechanical and tribological properties which confer protection against corrosion and wear. Classically, such deposits can have a thickness of &lt;500 μm, although there is a trend to thinner coatings to achieve faster deposition and lower costs. Depending on their composition and structure, as-plated deposits demonstrate good mechanical, tribological and electrochemical features, catalytic activity but also beneficial magnetic characteristics. Following thermal treatment, the hardness of Ni[sbnd]P metal deposits can approach or exceed that of hard Cr coatings. This paper provides a general survey of research on the electrodeposition of Ni[sbnd]P binary alloy coatings. Proposed phosphorus incorporation mechanisms, Ni[sbnd]P alloy microstructure before and after thermal treatment. Mechanical, tribological, corrosion, catalytic and magnetic properties are considered, as are the key process variables influencing the phosphorus content of deposits and the roles of the major electrolytic bath constituents. The merits of employing pulse plating and fabrication of newer (layered and functionally graded)structures are concisely explored. Interaction of four aspects: substrate state, electrolyte composition, process conditions and deposit properties is seen to be important during electrodeposition of Ni[sbnd]P alloys; areas deserving further study are identified.</p

Advanced data pre−processing for Comprehensive two−dimensional Gas Chromatography with Vacuum Ultraviolet Spectroscopy detection

International audienceComprehensive two−dimensional Gas Chromatography with Vacuum Ultraviolet detection (GC×GC/VUV) results in sizable data for which noise and baseline drift ought to be corrected. As GC×GC/VUV signal is acquired from multiple channels, these pre−processing steps have to be applied to data from all channels while being robust and rather fast with respect to significant size of the GC×GC/VUV data. In this study, we describe advanced GC×GC/VUV data pre−processing techniques for noise and baseline correction that are not available in commercial softwares. Noise reduction was performed on both the spectral and the time dimension. For baseline correction, a morphological approach based on iterated convolutions and rectifier operations is proposed. On the spectral dimension, much less noisy and reliable spectra are obtained. From a quantitative point of view, mentioned pre−processing steps significantly improve signal to noise ratio for analyte detection and hence improve their limit of detection (circa 6 times in this study). These pre−processing methods were integrated into plug im! platform (https://www.plugim.fr/)

Quantitative performance of forward fill/flush differential flow modulation for comprehensive two-dimensional gas chromatography

International audienceGC × GC is an advanced separation technique allowing to achieve quantitative and qualitative characterization of complex samples. In order to perform two-dimensional separation, the system must provide suitable peak modulation which will direct short impulses of first column flow towards the second column. Forward fill/ flush differential flow modulation is a cost effective and no cryogen requiring approach which allows modulation over a wide range of analytes with very different boiling points. However, optimization of the flow modulation process can be difficult to understand and quantification performance might be compromised if the parameters of the modulation process are not properly set. Modulated peak shape can be a good indication of the efficiency of the modulation process, however it is not sufficient to guarantee good quantification. Different average velocities in the beginning and the end of the thermally programmed GC run may cause different efficiency of the modulation process in various parts of the chromatogram. The purpose of this work is to investigate quantitative performance of the forward/fill flush modulation and delineate parameters that determine the effectiveness of the modulation process and its ability to properly reflect the quantitative composition of the investigated sample

Gas chromatography vacuum ultraviolet spectroscopy: A review

RMN+ECI2D+ALL:CLO:CGEInternational audienceAccelerated technological progress and increased complexity of interrogated matrices imposes a demand for fast, powerful, and resolutive analysis techniques. Gas chromatography has been for a long time a ‘go‐to’ technique for the analysis of mixtures of volatile and semi‐volatile compounds. Coupling of the several dimensions of gas chromatography separation has allowed to access a realm of improved separations in the terms of increased separation power and detection sensitivity. Especially comprehensive separations offer an insight into detailed sample composition for complex samples. Combining these advanced separation techniques with an informative detection system such as vacuum ultraviolet spectroscopy is therefore of great interest. Almost all molecules absorb the vacuum ultraviolet radiation and have distinct spectral features with compound classes exhibiting spectral signature similarities. Spectral information can be ‘filtered’ to extract the response in the most informative spectral ranges. Developed algorithms allow spectral mixture estimation of coeluting species. Vacuum ultraviolet detector follows Beer–Lambert law, with the possibility of calibrationless quantitation. The purpose of this article is to provide an overview of the features and specificities of gas chromatography–vacuum ultraviolet spectroscopy coupling which has gained interest since the recent introduction of a commercial vacuum ultraviolet detector. Potentials and limitations, relevant theoretical considerations, recent advances and applications are explored

Quantitative analysis of hydrocarbons in gas oils by two-dimensional comprehensive gas chromatography with vacuum ultraviolet detection.

International audienceGas oils (GOs) analysis is essential for production process control, in order to meet quality standards, to render these products safer for the environment, and to support research for alternative fuels. GOs quantitative analysis can be commonly achieved by employing two-dimensional comprehensive gas chromatography with flame ionization detection (GC × GC-FID) in combination with identification templates. However, in order to perform quantification for families which coelute in GC × GC analysis (e.g., naphthenes/olefins or polynaphthenes/monoaromatics), prefractionation of gas oil before GC × GC analysis is necessary. Recent introduction of the vacuum ultraviolet (VUV) detector has offered new possibilities in GOs analysis, as this detector can discern between the majority of hydrocarbon families thus possibly rendering the gas oil prefractionation unnecessary. Additionally, it can perform quantification according to Beer–Lambert’s law provided that VUV relative response factors (RRFs) are known. The purpose of this work is to report, for the first time, VUV RRFs for numerous hydrocarbons in GOs (∼160) according to their family and their carbon number, permitting to perform their direct quantification without the necessity of GO prefractionation. VUV RRFs were measured by using a GC × GC-VUV/FID dual detection setup in which FID was employed as a quantitative reference. In order to obtain VUV RRFs representative for any gas oil, a set of 14 GOs with different origins was employed. Both VUV RRFs averaged in the 125–240 nm range and spectral VUV RRFs (reference spectra) were obtained. It was demonstrated that VUV RRFs were similar between employed GOs allowing their universal use. Obtained RRFs were used to perform hydrocarbons quantification for a light cycle oil (LCO) by GC × GC-VUV, with olefins and naphthenes being quantified through spectral decomposition. Good comparability with results obtained by prefractionation was observed demonstrating the great interest of the GC × GC-VUV approach for the detailed and rapid analysis of hydrocarbons in gas oils

Determination of vacuum ultraviolet detector response factors by hyphenation with two-dimensional comprehensive gas chromatography with flame ionization detection

fffInternational audienceTwo-dimensional comprehensive gas chromatography is an established technique, employed for the characterization of complex samples. Broadband vacuum ultraviolet absorption spectroscopy detection has recently attracted a lot of attention as it is a universal detection technique characterized by good selectivity but also ease of use and amenability to coupling with two-dimensional comprehensive gas chromatography. Vacuum ultraviolet spectroscopy is particularly interesting due to the possibility of performing spectral decomposition for species that coelute in gas chromatography analysis. This detector has quantitative capabilities, however not all species absorb vacuum ultraviolet radiation the same. Unfortunately, vacuum ultraviolet relative response factors for compounds are not always available. Methods to rapidly measure vacuum ultraviolet relative response factors and generate a large database that would allow calibration free quantitative analysis of complex mixtures are therefore of great interest. In this work, a universal methodology that permits rapid measurement of vacuum ultraviolet relative response factors is reported. It involves flow modulated two-dimensional comprehensive gas chromatography with dual vacuum ultraviolet and flame ionization detection. In this set-up, flame ionization detection is employed as a quantitative reference allowing to scale vacuum ultraviolet responses of investigated compounds. This approach was validated by flow measurements and by comparing relative response factors obtained for model compounds with literature data