Chemical Composition Of Coatings Research Articles

Influences of Reaction Parameters and Ce Contents on Structure and Properties of Nano-scale Ce-HA Powders

Ce-incorporated apatite (Ce-HA) nano-scale particles with different Ce percentage contents (atomic ratio of Ce to Ce + Ca is 5%, 10% and 20%, respectively) were synthesized via a simple wet chemical method in this study. The crystal structure, chemical groups, thermal stability, crystal morphologies and crystal sizes of the Ce-HA nano-particles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The influences of reaction temperature, reaction time, pH value, and the atomic ratio of Ce to Ce + Ca on the structure and performance of Ce-HA particles were studied. The results show that the lattice constants, particle sizes, crystallinity and thermal stability of Ce-HA vary with the doped Ce contents. With the increase of Ce content, the lattice constants of the Ce-HA nano-particles remarkably increase but the particle size, crystallinity and thermal stability gradually decrease. The reaction temperature as well as the reaction time has no significant effect on the properties of the final products, while the pH value has a direct relationship with their final chemical composition. The obtained Ce-HA nano-size particles possess potential application in preparing artificial bone implants, bone tissue engineering scaffold and other bioactive coatings.

Effect of supplementing finishing pigs with different sources of chromium on performance and meat quality

The objective was to evaluate the dietary supplementation of different sources of chromium (inorganic: chromium sulfate and chelated: chromium-methionine) during the finishing period of pigs to obtain improvements in the animal performance, and carcass and meat quality. The statistical design was randomized blocks, where 44 barrows, with an initial weight 60.49±5.12 kg, were divided into four blocks (heavier, heavy, light and lighter) according to initial weight. The experimental diets were isoenergetic and isonutrient, except for the chromium level. The treatments were divided as follows: control (without chromium), control + 200 ppb of inorganic chromium (chromium sulfate), and control + 200 ppb of chelated chromium (chromium-methionine). In the performance measures, the stall was considered the experimental unit and in the blood parameters, carcass and meat evaluations each animal constituted the experimental unit. Animals were slaughtered when they reached the final average weight of 107.23±5.23 kg. Blood samples were collected and tested for blood parameters (cholesterol, triglycerides and glucose) as well as carcass quality (hot and cold weights, yield, loin-eye area, muscle depth and backfat thickness) and meat quality (initial and final pH, drip loss, color, chemical composition and lipid oxidation) parameters. Chromium-methionine supplementation provides a greater daily weight gain only compared with the animals that are not supplemented with chromium, because feed conversion is better as compared with the other treatments. After 24 hours of storage, the meat from pigs supplemented either with chromium-methionine or with chromium sulfate presents lower lipid oxidation than that from non-supplemented animals. However, after three days of storage, only chromim-methionine is effective in reducing lipid oxidation.

Effect of activation volume on the defect-induced anomalous electronic transport in Rb $$_{0.8}$$ 0.8 Fe $$_2$$ 2 Se $$_2$$ 2

We adopted an absolute-reaction model which is considering the hole(defect)-induced charged frictionless transport to explain the unusual experiment: Two single crystalline samples of the same nominal composition Rb $$_{0.8}$$ Fe $$_2$$ Se $$_2$$ were prepared using the self-flux technique via two different precursor routes. Although the difference in the final chemical composition falls within a narrow range, one was superconducting with a $$T_c \sim 31$$ K, while the other behaves like a narrow gap semiconductor.

Electrophoretic deposition of zinc-substituted hydroxyapatite coatings

Zinc-substituted hydroxyapatite nanoparticles synthesized by the co-precipitation method were used to coat stainless steel plates by electrophoretic deposition in n-butanol with triethanolamine as a dispersant. The effect of zinc concentration in the synthesis on the morphology and microstructure of coatings was investigated. It is found that the deposition current densities significantly increase with the increasing zinc concentration. The zinc-substituted hydroxyapatite coatings were analyzed by X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. It is inferred that hydroxyapatite and triethanolamine predominate in the chemical composition of coatings. With the increasing Zn/Ca ratios, the contents of triethanolamine decrease in the final products. The triethanolamine can be burnt out by heat treatment. The tests of adhesive strength have confirmed good adhesion between the coatings and substrates. The formation of new apatite layer on the coatings has been observed after 7days of immersion in a simulated body fluid. In summary, the results show that dense, uniform zinc-substituted hydroxyapatite coatings are obtained by electrophoretic deposition when the Zn/Ca ratio reaches 5%.

Preliminary Results on the Influence of Carbonic Snow Addition during the Olive Processing: Oil Extraction Yield and Elemental Profile

The compositional profile of olive oil is strictly connected to the raw material characteristics, nevertheless technological processes utilized to extract the oil fraction can deeply impact on its final chemical composition. Trace quantities of elements are naturally present in olive oil. To make objective and measurable food quality and traceability, it is necessary to develop analytical methods useful to detect contaminants potentially coming from any phases of the supply chain and define characteristic markers and patterns for the authenticity verification and origin demonstration. The objective of the paper is twofold: a) to verify the influence of the addition of cryogen (CO2,s), directly to olives during pre-milling phase, on the yield of the oil production; b) to develop specific analytical methods for evaluating the elemental profile of olive oil and to collect some preliminary data about the possibility to use these methods in order to put in evidence the possible influence of different process conditions on the olive oil elemental profile. The experimental evidences show as the addition of cryogen directly to the olives during pre-milling phase seem induce a general increase in the oil extraction yield, ranging from 2 to 12,4%. While preliminary results show a rather homogeneous elemental content among all the analyzed samples of olive oil, samples of olive oil obtained by the “traditional” process showed - in general - a higher content of Ca, Cr, Mg, Si and Zn, compared to those obtained by the addition of “carbonic snow”. The analytical methods for evaluating the olive oil elemental profile by ICP-AES and ICP-MS were set up and the methodologies for data processing and statistical analysis were developed, so they could be applied during the next crop season to study in depth the influence of different process conditions on the olive oil elemental profile.

Synthesis, crystal structure, characterization and luminescent properties of KBaTbB2O6

Novel rare-earth borate KBaTbB2O6 was synthesized using a conventional solid-state reaction method. The crystal structure of KBaTbB2O6 has been determined by the Rietveld analysis, which demonstrates that the final chemical composition is K0.46Ba0.54Tb0.49BO3 and KBaTbB2O6 is isomorphous with KBaY(BO3)2 and crystallizes in the planar trigonal [BO3]3− group R-3m with lattice parameters of a=5.4562(4) Å, c=17.8629(2) Å, and Z=3. Tunable emission in red wavelength range was realized by doping and controlling Eu3+ ions content into KBaTbB2O6. The critical energy transfer distance calculated by the concentration quenching theory was 6.64Å and the energy transfer from Tb3+ to Eu3+ took place via a resonance-type mechanism.

Electrochemical behavior of plasma electrolytic oxide coatings on rare earth element containing Mg alloys

In this work, ceramic-like oxide coatings were produced on rare earth element containing Elektron21 (E21) and WE43 Mg alloys using plasma electrolytic oxidation (PEO) process, and in addition to these alloys, AZ31B Mg alloy was used for comparison studies. Surface morphology and chemical composition of coatings were determined using scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer (EDS). Phase analysis of coatings was carried out by X-ray diffraction (XRD). Electrochemical corrosion tests were undertaken by means of potentiodynamic polarization and electrochemical impedance spectroscopy techniques in 3.5% NaCl solution at ambient temperature. SEM results showed that the coatings have two layered microstructure with a porous top layer and a dense barrier layer. The SEM images of E21 and WE43 indicated that intermetallic compounds contributed into the coating structure during PEO processing. Electrochemical corrosion test results showed that the corrosion rates of PEO-coated substrates greatly decreased when compared to that of bare Mg alloys. However, bare rare-earth containing alloys showed increased corrosion resistance compared to bare AZ31B alloy.

Comparative experimental study of laser-induced transitions in crystalline silicon by femtosecond, picosecond, and millisecond laser ablation

In order to study laser-induced transitions of the crystalline silicon, comparative ablation experiments by femtosecond-, picosecond-, and millisecond-pulsed laser were carried out on<111>crystalline silicon wafers in this study. For each laser ablating process, final chemical composition and microstructural state of ablated material on sample surface were analyzed by X-ray photoelectron spectroscopy and transmission electron microscopy, respectively. Then the influences of laser pulse duration variation on the composition and microstructure of ablated material were also discussed. Therefore, the experimental results were considered to provide more completed and further understandings of laser-induced transitions of crystalline silicon, which may have some contribution to the development of laser-semiconductors micromachining.

Characterisation and modelling of mixing processes in groundwaters of a potential geological repository for nuclear wastes in crystalline rocks of Sweden

This paper presents the mixing modelling results for the hydrogeochemical characterisation of groundwaters in the Laxemar area (Sweden). This area is one of the two sites that have been investigated, under the financial patronage of the Swedish Nuclear Waste and Management Co. (SKB), as possible candidates for hosting the proposed repository for the long-term storage of spent nuclear fuel. The classical geochemical modelling, interpreted in the light of the palaeohydrogeological history of the system, has shown that the driving process in the geochemical evolution of this groundwater system is the mixing between four end-member waters: a deep and old saline water, a glacial meltwater, an old marine water, and a meteoric water. In this paper we put the focus on mixing and its effects on the final chemical composition of the groundwaters using a comprehensive methodology that combines principal component analysis with mass balance calculations. This methodology allows us to test several combinations of end member waters and several combinations of compositional variables in order to find optimal solutions in terms of mixing proportions. We have applied this methodology to a dataset of 287 groundwater samples from the Laxemar area collected and analysed by SKB. The best model found uses four conservative elements (Cl, Br, oxygen-18 and deuterium), and computes mixing proportions with respect to three end member waters (saline, glacial and meteoric). Once the first order effect of mixing has been taken into account, water–rock interaction can be used to explain the remaining variability. In this way, the chemistry of each water sample can be obtained by using the mixing proportions for the conservative elements, only affected by mixing, or combining the mixing proportions and the chemical reactions for the non-conservative elements in the system, establishing the basis for predictive calculations.

Effects of processing parameters on immersion vacuum cooling time and physico-chemical properties of pork hams

The effects of agitation (1002rpm), different pressure reduction rates (60 and 100mbar/min), as well as employing cold water with different initial temperatures (IWT: 7 and 20°C) on immersion vacuum cooling (IVC) of cooked pork hams were experimentally investigated. Final pork ham core temperature, cooling time, cooling loss, texture properties, colour and chemical composition were evaluated. The application for the first time of agitation during IVC substantially reduced the cooling time (47.39%) to 4.6°C, compared to IVC without agitation. For the different pressure drop rates, there was a trend that shorter IVC cooling times were achieved with lower cooling rate, although results were not statistically significant (P>0.05). For both IWTs tested, the same trend was observed: shorter cooling time and lower cooling loss were obtained under lower linear pressure drop rate of 60mbar/min (not statistically significant, P>0.05). Compared to the reference cooling method (air blast cooling), IVC achieved higher cooling rates and better meat quality.

Effect of Helmholtz Oscillation on Auto-shroud for APS Tungsten Carbide Coating

The atmospheric-pressure plasma spray (APS) of tungsten coating was performed using tungsten carbide (WC) powder by means of DC plasma torch equipped with a stepped anode nozzle as a potential method of W coating on graphite plasma-facing component of fusion reactors. This nozzle configuration allows Helmholtz oscillation mode dominating in APS arc fluctuation, and the variation of auto-shroud effect with Helmholtz oscillation characteristics can be investigated. Tungsten coating made from WC powder has lower porosity and higher tungsten purity than that made from pure tungsten powder. The porosity and chemical composition of coatings were investigated by mercury intrusion porosimetry and x-ray photoelectron spectroscopy, respectively. The purity of tungsten coating layer is increased with the increasing frequency of Helmholtz oscillation and the increasing arc current. The modulation of Helmholtz oscillation frequency and magnitude may enhance the decarburization of WC to deposit tungsten coating without W-C and W-O bond from WC powder.

Effect of Precursor on Speciation and Nanostructure of SiBCN Polymer‐Derived Ceramics

A comparative structural study of silicon borocarbonitride polymer‐derived ceramics synthesized using polyborosilylcarbodiimide and polyborosilazane precursors is carried out using high‐resolution, multinuclear, one‐ and two‐ dimensional NMR spectroscopy. The polyborosilylcarbodiimide‐derived ceramics contain relatively pure Si3N4 and C nanodomains with the BN domains being present predominantly at the interface such that the bonding at the interface consists of Si–N–B, Si–N–C, and B–N–C linkages. In contrast, the structure of the polyborosilazane‐derived ceramics consists of significant amount of mixed bonding in the nearest‐neighbor coordination environments of Si and B atoms leading to the formation of SiCxN4−x (0 ≤ x ≤ 4) tetrahedral units and BCN2 triangular units. The interfacial region between the SiCN and C nanodomains is occupied by the BCN phase. These results demonstrate that the chemistry of the polymeric precursors exerts major influence on the microstructure and bonding in their derived ceramics even when the final chemical compositions of the latter are similar.

Heterogeneous and multiphase formation pathways of gypsum in the atmosphere

Gypsum is a major sulphur-containing component of atmospheric particulate matter. To date, however, its formation pathways in the atmosphere are still not well known. In this study, several potentially important formation pathways of gypsum in atmospheric aerosols are proposed. We found that gypsum was formed in the humidifying-dehumidifying process of mixed sulphate and calcium salts. A deliquescent layer is crucial for the formation of gypsum from Ca(2+) and SO4(2-) ions. In particular, the presence of hygroscopic components, such as (NH4)2SO4 and Ca(NO3)2, is necessary for the conversion of calcium carbonate (CaCO3) upon heterogeneous reaction of either SO2 + O3 or SO2 + NO2 as well as anhydrous calcium sulphate (CaSO4) to form gypsum (CaSO4·2H2O) under ambient conditions. This study provides definitive evidence that synergistic effects in the physical and chemical processing of aerosol particles have a significant effect on their final chemical composition, mixing state and hygroscopic behaviour which dictates the environmental and climate impacts of the resulting aerosol.

Binary Effects on Supernovae

AbstractHere we review how binary interactions affect the final pre-supernova structure of massive stars and the resulting supernova explosions. (1) Binary-induced mass loss and mass accretion determine the final envelope structure, the mass, radius and chemical composition, which are mainly responsible for the supernova appearance and supernova (sub-)type. (2) Mass loss can also drastically change the core evolution and hence the final fate of a star; specifically, around 10 M⊙, it determines whether a star explodes in a supernova or forms a white dwarf, while for larger masses it can dramatically increase the minimum main-sequence mass above which a star is expected to collapse to a black hole. (3) Mass loss before the supernova directly affects the circumstellar medium (CSM) which can affect the supernova spectrum (e.g. account for the IIn phenomenon), produce powerful radio emission and, in extreme cases, lead to a strong interaction with the supernova ejecta and thus strongly modify the lightcurve shape; it may even be responsible for some of the superluminous supernovae that have recently been discovered.

Thermal and chemical treatments of montmorillonite clay

Abstract Montmorillonite clay from a natural deposit was processed to remove impurities and later submitted for thermal and chemical treatments. The sample was first subjected to a thermal treatment at 400 °C, for 1 h, to remove organic components. The chemical treatment was conducted first by using an acid attack with nitric acid and sulfuric acid, then, adding sodium acetate in ethylene glycol clay dispersion, and finally the clay was dispersed in xylene with subsequent addition of silane, N-(b-aminoethyl)-g-aminopropyiltrimethylsilane. The combined thermal and chemical treatment was found to have a significant effect on the final chemical composition of the nanoclay. X-ray diffraction patterns suggested that the combined thermal and chemical treatment resulted in increased interplanar distances, thus favoring exfoliation of the clay lamellae, which was also confirmed by SEM images. Fourier transform infrared (FTIR) spectroscopy analysis suggested that the combined thermal and chemical treatment resulted in removal of water from the montmorillonite, without any modification or destruction of the clay structure. Thus, the combination of thermal and chemical treatments proposed in this work may be a promising approach to process montmorillonite intended for the production of advanced materials.

Atmosphere Effect on Sintering Behaviour of Astaloy CrM and Astaloy CrL Höganäs Powders with Manganese and Carbon Additions / Wpływ Atmosfery Na Spiekalność Komercyjnych Proszków Höganäs Astaloy CrM I Astaloy CrL Z Dodatkami Manganu I Węgla

Dilatometric data for Astaloy CrM (3% Cr-0.5% Mo) and Astaloy CrL (1.5% Cr-0.2% Mo) powders with additions of 0.3% carbon and 3.0% manganese during sintering cycles up to 1120 and 1250°C in different atmospheres are reported. For comparison, also Astaloy CrM and Astaloy CrL powders were investigated. Starting with green densities of approx. 6.8 g/cm3, the final density of sintered compacts was influenced mainly by the sintering temperature, while the results showed the only minor effect of the sintering atmosphere on the final dimensional changes. However, the sintering atmosphere influences the sintering behaviour, microstructure and the final chemical composition of sintered compacts. In sintered and in the dilatometer cooled Mn-Cr-Mo-C steels predominantly bainitic structures were obtained.

Effects of temperature on growth, survival and body composition in larvae of barbel, Barbus barbus (L.)

Barbel larvae were reared for 21 days at 21.0, 24.1, 27.2 or 30.0 °C and fed ad libitum live Artemia nauplii for 16 h a day. The final survival rates exceeded 99 %. The highest mean daily growth rates, amounting to 0.97 mm total length (TL) and 17.3 % body weight (BW), were found at 27.2 °C. The optimum temperature calculated for the growth of larvae was 26.9 °C for TL and 26.5 °C for BW. An increase in water temperature accelerated the development rate to a larger degree than the growth rate. Temperature significantly influenced the final fish body chemical composition. The lowest dry matter content (19.1 %) was found at 24.1 °C. The highest values of ash content were determined for 27.2 and 30.0 °C and were 11.3 and 11.0 % of dry matter, respectively. The fish body caloric value was the highest at 30.0 °C (30.0 J mg−1). The analysis of changes in the fish body chemical features against the effective day-degrees age scale did not reveal significant influence of temperature. Therefore, the effects of temperature on larval body composition seem to be related mainly to differences in barbel developmental progress at particular temperatures.

Oxidation behavior of Ni-based coatings deposited by PTA on gray cast iron

The aim of this investigation was to study the effect of PTA current (100 and 128 A) on the oxidation behavior of nickel-based hardfacing coatings deposited on gray cast iron. The oxidation behavior of coatings held at 800 and 900°C for 2h in air was studied by thermogravimetry (TGA). The surface, as well as the cross‐section, of the coatings was characterized by scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM/EDS) and X-ray diffraction (XRD). TGA results indicate that the coating produced with lower arc current exhibits more effective oxidation resistance than that produced with higher current. This behavior could be correlated with the dilution promoted by the PTA process, which changes the chemical composition of coatings. As a consequence, different kinds of oxide scales were detected in each coating after isothermal oxidation. In the specimen produced with a lower arc current and lower dilution a protective layer of Si–O is formed, while in the specimen produced with a higher current two layers could be identified: an external one of Fe2O3, with small features of Fe3O4 and NiFe2O4 spinel rich phases, and an internal one of Fe3O4 with small amount of a dark phase evenly distributed rich in silicon, nickel and iron. The isothermal oxidation curve at 900°C of the coating with higher dilution showed two stages: at an early stage, the weight increase over time is almost linear whereas, in a second stage, a parabolic law could be fitted to the experimental data. The other specimens followed only a parabolic law.

The nature of shock-induced calcite (CaCO3) devolatilization in an open system investigated using a two-stage light gas gun

The shock-induced decarbonation of non-porous calcite was investigated in an open system over a wide range of peak shock pressures using a two-stage light gas gun and a quadrupole mass spectrometer. We developed a new experimental technique that avoids chemical contamination from the acceleration gas used in the gun. High-speed imaging and spectroscopic observations were conducted simultaneously to investigate the validity of the experimental procedure. The decarbonation efficiency along the Hugoniot curve changed at around 50GPa—the approximate incipient decarbonation pressure predicted by the previous theoretical studies. Decarbonation, albeit at a low efficiency, was detected at pressures below the 50GPa threshold, as observed in previous experimental studies, possibly as a result of energy localization due to a process like shear banding. A simple theoretical model for shock-induced decarbonation during isentropic release was constructed based on the entropy method and the lever rule, assuming the experimental conditions. The predicted amount of released CO2 as a function of the peak shock pressure agreed well with the experimental results at pressures exceeding 50GPa, strongly suggesting that the amount of shock-induced CO2 gas was determined only by the shock-induced entropy gain and by the entropies for incipient and complete decarbonation at the ambient pressure. In future experiments, the new method will be used for quantitative measurements of the chemical composition of impact-induced gases derived from other solid materials. The proposed method is useful in determining the peak shock pressure required for vaporization/devolatilization of geologic materials and for estimating the final chemical composition of impact-induced vapor clouds.

On assessment of processing variables on copper–tin functionally graded alloys produced by incremental melting and solidification process

The present work is concerned with the ability of the incremental melting and solidification process to be used in a controlled way to produce functionally graded materials in industrial environments. For this purpose, the influence of the main process parameters, namely relative mould/coil rate and melt temperature, is evaluated in relation to the obtained final component chemical composition gradient. Several graded components of Cu–Sn alloys were produced. The effect of the process parameters on the final component gradient was quantified. It was verified that both the melt temperature and the relative mould/coil rate play a similar role in final component chemical composition gradient. Predictive equations for the gradient, namely the extension of chemical composition gradient zones, are proposed based on the two studied variables.