Addition Of Sodium Tungstate Research Articles

Сomposition, structure and functional properties of silver-tungsten composition electrochemistry coatings formed with the help of ultrasound

Influence of electrolyte composition and deposition parameters on the composition, structure, physicalmechanical and functional properties of composite silver-tungsten coatings was studied. It was shown that addition of sodium tungstate in electrolyte and application of ultrasound at the electroplating leads to formation of silver layers that contains tungsten oxides and demonstrates lower crystalline nucleus. Application of ultrasound vibration at the electrochemical deposition increases ability for plating process control and allows to optimize electrophysical and functional properties of composite electrochemical coatings, to make dense fine crystalline thin layers. Obtained layers demonstrate increased microhardness (by 10–50 %), wear resistance (1,5–2 times), corrosion resistance and improved contact electrical resistance. It is shown that application of ultrasound effect to electrodeposition allows increased level of permissible current density and provides.

Synthesis of NiWP coated diamonds particles with enhanced mechanical and anti-corrosion property for diamond wires of the sawing process

In this study, NiWP ternary shell layer on diamond powder was synthesized by electroless deposition method. The characteristics of thin films with different deposition parameters such as bath compositions, temperature, and pH were studied. The composition of tungsten in NiWP thin films could be varied by the concentration of sodium tungstate, and it was saturated as ~24 wt%. With the decrease of phosphorous content, crystal structure was changed from amorphous to polycrystalline by the addition of sodium tungstate in the electrolyte. The incorporation of tungsten into NiP films could improve the hardness and the corrosion resistivity, which is critical for utilizing the diamond powders as a sawing applications. From systematic investigations, the optimal electroless deposition of NiWP on the diamond powders was obtained at 70 °C with pH 9.

The Validity of Protein in Australian Honey as an Internal Standard for C4 Sugar Adulteration

Recent media reports claimed that a large proportion of honey sold in Australian supermarkets was adulterated, although no specific details of the nature of the adulteration were made public. To investigate the basis of these claims, the current study was conducted with samples of Australian honey obtained from supermarkets or direct from beekeepers/small-scale producers. Without evidence to the contrary, it was assumed that the beekeeper honey would be unadulterated. Analysis of these samples using the official AOAC method (998.12) found that a proportion of both supermarket and beekeeper honeys had apparent C4 sugar contents greater than 7% and this proportion was similar to the failure rates reported by popular media. The AOAC test measures the difference in carbon isotopic composition between the honey (mostly sugar) and protein precipitated from the honey and relies on the assumption that nectar (the source of sugar) comes from the same plant species as pollen (the source of protein). Initial results found that most Australian honey failed the AOAC test because the protein was depleted in 13C with respect to the sugar although the sugar was in the normal range (δ13C more negative than – 24‰). A series of experiments investigated the nature of the precipitate obtained from Australian honey and found the weight of precipitate was greater than the amount of protein measured in the honey and the precipitate contained non-protein material. Based on these findings, a modification to the AOAC method is proposed whereby samples, after addition of sodium tungstate and acid, are left unheated for 48 h for a floc to form. This procedure produced a precipitate that was mostly comprised of protein. It is also recommended that the acceptance criteria for Australian honey are increased from 1 to 2‰ difference between the carbon isotopic composition of the honey and the precipitate. Using the modified method and acceptance criteria, the failure rate for Australian honey was no more than 8%, compared to 37% using the official method.

Influence of cathodic duty cycle on the properties of tungsten containing Al2O3/TiO2 PEO nano-composite coatings

Current waveforms with different cathodic duty cycles of 0, 20 and 40% were applied to coat 7075 aluminum alloy in a silicate based electrolyte containing titania nano-particles. Using a constant current mode, the recorded voltage-time response showed that the required voltage for PEO coating process is lower in the presence of sodium tungstate as additive. By increasing the cathodic duty cycle, pancake surface morphology was converted to crater-like. Phase and chemical composition of the coatings were investigated by using grazing angle XRD and SEM/EDS. The tungsten concentration decreased linearly with the increase of cathodic duty cycle, which is dissimilar to the titania content. It was proposed that physical entrapping has been associated with electrophoretic incorporation of titania nano-particles, while the adsorption mechanism of tungstate anions is purely electrophoretic. Corrosion performance of the coatings was evaluated by potentiodynamic polarization and EIS measurements. Addition of sodium tungstate was detrimental for corrosion performance of the coating in the case of unipolar waveform while the corrosion resistance was improved when bipolar waveforms were used. Long-term corrosion behavior of the coatings was investigated by EIS up to 16 weeks. The results showed remarkable difference between corrosion performance of the coatings produced by unipolar and bipolar waveforms, but the difference was negligible for the coatings produced by the bipolar waveforms with different cathodic duty ratios.

The genetic characteristics in cytology and plant physiology of two wheat (Triticum aestivum) near isogenic lines with different freezing tolerances.

Freezing tolerance in taft plants relied more upon an ABA-independent- than an ABA-dependent antifreeze signaling pathway. Two wheat (Triticum aestivum) near isogenic lines (NIL) named tafs (freezing sensitivity) and taft (freezing tolerance) were isolated in the laboratory and their various cytological and physiological characteristics under freezing conditions were studied. Proplastid, cell membrane, and mitochondrial ultrastructure were less damaged by freezing treatment in taft than tafs plants. Chlorophyll, ATP, and thylakoid membrane protein contents were significantly higher, but malondialdehyde content was significantly lower in taft than tafs plants under freezing condition. Antioxidant capacity, as indicated by reactive oxygen species accumulation and antioxidant enzyme activity, and the relative gene expression were significantly greater in taft than tafs plants. Soluble sugars and abscisic acid (ABA) contents were significantly higher in taft plants than in tafs plants under both normal and freezing conditions. The upregulated expression levels of certain freezing tolerance-related genes were greater in taft than tafs plants under freezing treatment. The addition of sodium tungstate, an ABA synthesis inhibitor, led to only partial freezing tolerance inhibition in taft plants and the down-regulated expression of some ABA-dependent genes. Thus, both ABA-dependent and ABA-independent signaling pathways are involved in the freezing tolerance of taft plants. At the same time, freezing tolerance in taft plants relied more upon an ABA-independent- than an ABA-dependent antifreeze signaling pathway.

Sulphated silica tungstic acid as a highly efficient and recyclable solid acid catalyst for the synthesis of tetrahydropyrimidines and dihydropyrimidines

For the first time sulphated silica tungstic acid (SSTA) has been synthesized and used as an acidic catalyst in organic synthesis. The catalyst was prepared by a simple method based on the reaction of silica with SOCl2 followed by addition of sodium tungstate and then functionalization with chlorosulfonic acid. The three-component Biginelli-like condensation of different heteroaldehydes, urea and ethyl cyanoacetate or phenyl acetic acid catalyzed by SSTA under solvent-free conditions afforded novel tetrahydropyrimidines in high yields. The catalyst tolerated different heteroaldehydes and also catalyzed the synthesis of Biginelli compounds efficiently giving excellent yield of products. The catalyst was characterized by FT-IR, XRD and SEM-EDX analyses. The stability of the catalyst was evaluated by DSC and TG analyses. The major advantages of the present method are high yields, short reaction times, and solvent-free reaction conditions. The activity and simple recyclability without losing catalytic activity make this catalyst a good replacement to literature methods.

The influence of sodium tungstate concentration and anodizing conditions on microarc oxidation (MAO) coatings for aluminum alloy

Microarc oxidation (MAO) coatings on 5052 aluminum alloy are prepared in silicate–hypophosphite electrolytes with sodium tungstate. The effects of sodium tungstate concentrations and current density on the surface morphology, phase composition and properties of the coatings are investigated. With the addition of sodium tungstate in the electrolyte and increase of current density, the final voltage at the microarc discharge process increases. The results also show that the MAO coatings are composed mainly of α-Al2O3 and γ-Al2O3 and the proportion of α-Al2O3 and γ-Al2O3, pore size, surface roughness as well as thickness of the coatings strongly depend on the sodium tungstate concentration and current density. Thus, the hardness, friction coefficient and corrosion resistance of the coatings are significantly influenced by the magnitude of the current density and sodium tungstate concentration. These oxide films on aluminum were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thickness gage, and polarization curves, respectively.

Effects of sodium tungstate on properties of micro-arc coatings on magnesium alloys

Anodic coatings were prepared by micro-arc oxidation on AZ91HP magnesium alloys in a base solution containing 10 g/L NaOH and 12 g/L phytic acid with addition of 0–8 g/L sodium tungstate. The effects of sodium tungstate on the coating thickness, mass gain, surface morphology and corrosion resistance were studied by eddy current instrument, electronic scales, scanning electron microscope and immersion tester. With the addition of sodium tungstate, the electrolytic conductivity increases and the final voltage decreases. The sodium tungstate has a minor effect on the coating thickness, but lightens the coating color. With increasing sodium tungstate concentration, the size of micropores on the coatings is enlarged and the corrosion resistance of the anodized samples decreases.

Simultaneous Determination of Amoxicillin and Ampicillin in Bovine Milk by HPLC with Fluorescence Detection

A sensitive liquid chromatographic analytical method using fluorescence detection was developed for the simultaneous determination of amoxicillin and ampicillin residues in raw and processed bovine milk. Aliquots of raw or processed milk (5 mL) were diluted to 40 mL with 0.01 M KH2PO4 (pH 4.5) buffer, and the soluble proteins were precipitated with the addition of sodium tungstate and sulfuric acid followed by centrifugation. The drug residues were concentrated by passing the supernatant through a C18 solid phase extraction cartridge. Amoxicillin and ampicillin were eluted from the cartridge and reacted with salicylaldehyde to form fluorescent derivatives, which were then analyzed with liquid chromatography and fluorescence detection. Average recoveries of spiked amoxicillin and ampicillin at 5, 10, and 20 ng/mL were >80%, with coefficients of variation (CV) <5%. The limit of detection (LOD) and limit of quantitation (LOQ) for amoxicillin were 1.1 and 2.4 ng/mL, respectively. The LOD and LOQ for ampicilli...