Borax Salt Research Articles

Thermodynamics and Kinetics of Borochromized Coatings Prepared on 5CrNiMo Steel by Thermo-Reactive Diffusion

Borochromized coatings on 5CrNiMo steel were prepared by thermo-reactive diffusion in a molten borax salt bath at 1173 K, 1223 K, and 1273 K for 0.5–6 h. The cross-sectional observation of optical microscopy (OM) revealed that the as-obtained coatings possessing a comb-like or needle-like microstructure with 21.4–84.7 µm thickness were smooth, compact, and homogeneous. X-ray diffractometry (XRD) results expressed that the borochromized coatings mainly consisted of FeB, Fe2B, Cr5B3, and a small amount of M7C3 (M–Cr, Fe) and α-Fe(Cr). B4C, as a boron-donating agent, first reacted with NaF (activator) to produce active boron atoms and then reduced Cr2O3 (chromium-donating agent) to generate active chromium atoms, whereas borax was only used as the base salt or heating medium in the present experiment. The activation energy of the as-prepared borochromized coating on 5CrNiMo steel was calculated as 161 kJ/mol.

Brightly Luminescent Cu-Zn-In-S/ZnS Core/Shell Quantum Dots in Salt Matrices

Abstract In the past decades cadmium-free quantum dots (QDs), among which are quaternary colloidal Cu-Zn-In-S/ZnS (CZIS/ZnS) core/shell nanocrystals (NCs), have attracted great scientific interest. Particularly, their low toxicity and the possibility to tune their photoluminescence (PL) properties by varying the composition in the multicomponent system make them highly attractive for applications in light-emitting diodes (LEDs). Thus, the demands for high quality CZIS/ZnS QDs and methods to process them into bulk materials stimulate investigations of these nanomaterials. Herein, we demonstrate the synthesis of CZIS/ZnS core/shell NCs via a surfactant induced nucleation process, which emit in various colors covering the range from 520 nm to 620 nm possessing high photoluminescence quantum yields (PLQYs) up to 47%. Furthermore, the as synthesized NCs were successfully integrated into two different salt matrices [Na2B4O7 (Borax) and LiCl] using two different approaches. The commonly used incorporation of the NCs into Borax salt led to salt crystals emitting from 540 nm to 600 nm with PLQYs up to 24%. By encapsulating the QDs into LiCl, brightly emitting NCs-in-LiCl powders with the PL covering a range from 520 nm to 650 nm with PLQYs of up to 14% were obtained. As a proof of concept, the fabrication of a color conversion LED using NCs encapsulated into LiCl demonstrated the applicability of the encapsulated NCs.

Epsomite as flame retardant treatment for wood: Preliminary study

The effect of epsomite as flame retardant for wood has been investigated and compared with a commercial boron salt. Both flame retardants have been introduced into wood samples by vacuum impregnation. Epsomite is a hydrated sulphate salt with a water solubility of 731gL−1 at room temperature. Thanks to this high solubility it was possible to obtain elevated epsomite loadings in comparison with the borax salt. Flame retardancy was evaluated by means of the limiting oxygen index, the dripping test and the exposition to a direct flame (Bunsen test). The results showed that the addition of epsomite increases the limiting oxygen index, delays the time to ignition and the evolution of the temperatures trough the wood.

Evaluation of Some Plant Extracts for the Control of Bacterial Soft Rot of Tubers

The use of protective chemicals on ware tubers can render it unfit for consumption as tubers undergo little processes before consumption. Hitherto, there is no effective control measure to manage this disease (Pectobactrium ssp); therefore, selection of some plant extracts for the management the disease will be the preferred option. The objective of the study therefore was to evaluate some plant materials for the management of tuber soft rot bacteria induced by pectobacterium ssp . Aqueous extracts of neem ( Azadirachta indica A. Juss), Eucalyptus leaves ( Eucalyptus citrodorus (L )), Lemon grass ( Cymbopogon citratus (Stapf)), Garlic bulb ( Allium sativum (linn)), Ginger ( Zingiber officinale ) (Roscoe)) and Aloe vera were evaluated for the management of bacterial soft rot of some tubers (cocoyam, Irish potato, sweet cassava, sweet potato and white) induced by Erwinia spp. Two methods involving in vitro and tuber assays were used. Lemon grass, garlic, Aloe vera , neem extracts and borax salt had the greatest inhibitory effect on Pectobacterium spp., and therefore recommended for the management of tuber soft rot bacteria.

Characterization of vanadium carbide coating deposited by borax salt bath process

Thermal reactive diffusion coating of vanadium carbide on DIN 2714 steel substrate was performed in a molten borax bath at <TEX>$950-1050^{\circ}C$</TEX>. The coating formed on the surface of the substrate had uniform thickness (<TEX>$1-12{\mu}m$</TEX>) all over the surface and the coating layer was hard (2430-2700 HV), dense, smooth and compact. The influence of the kinetics parameters, temperature and time, has been investigated. Vanadium carbide coating was characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX) and X-ray diffraction analysis (XRD). The corrosion resistance of the coating was evaluated by potentiodynamic polarization in 3.5% NaCl solution. The results obtained showed that decrease of coating microhardness following increasing time and temperature is owing to the coarsening of carbides and coating grain size.

Kinetics of V(N,C) and Nb(N,C) coatings produced by V–Nb–RE deposition technique

A duplex surface treatment on AISI H13 steel has been developed involving nitrocarburizing and followed by vanadium niobium and rare earths (V–Nb–RE) thermo-reactive deposition (TRD) techniques. The TRD process was performed in molten borax salt bath at 1223, 1283 and 1343K for 1–4h, respectively. The process formed a thickness of 6 to 35μm of vanadium carbonitride and niobium carbonitride coatings on a hardened diffusion zone. Characterization of the coatings by means of scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) indicates that the compact and dense coatings mainly consist of V8C7, NbC, NbN and VN phases. The value of Vickers hardness of the coatings was up to 1350 HV0.1 after tempering at 848K for 2h. All the growth processes of the vanadium carbonitride and niobium carbonitride coatings obtained by V–Nb–RE deposition technique followed a parabolic kinetics. Activation energy (Q) for the process was estimated to be 215.68kJ/mol of vanadium carbonitride coating, and 134.32kJ/mol of niobium carbonitride coating. Under certain conditions, the values of Q were greater than single vanadizing and deposition niobium. However, growth rate constant (K) was very similar among pairs of them.

Composition variation of borax salt during the process of vanadizing by thermal diffusion

Vanadium pentoxide, borax, boron carbide and sodium fl uoride were used to grow vanadium carbide coating on surface of Cr12 steel at 950 °C by TD process. The coating of vanadium carbide (VC) extended the serve-life period of Cr12 steel as punching die. Kinetics of vanadium carbide coating growth was brought forward and verified by comparison of the mathematical model with the experimental results. The thickness of coating was illustrated by SEM. The chemical constituent of coating and remnants were tested by X-ray diffraction (XRD) and X-ray energy dispersive spectroscopy (EDS). To increase the thickness, rare earth silicon powder (FeSiRe23) was added to the borax salt bath. The analysis of XRD revealed that FeSiRe23 increased the depth of vanadium car-bide coating as reducing agent and catalysis.

Effect of Salt Bath Composition on the Chromium Diffusion on Plain Carbon Steels by TRD Process

The thermo-reactive diffusion (TRD) process is used for diffusing an element to the metallic steel substrate. TRD is carried out by using either salt bath or fluidized bed methods. In this research, the molten salt bath method is used. Ferro chromium was dissolved in the molten borax as the source of chromium in the salt. Samples of cylindrical shape of plain carbon steel with 10 mm diameter and 20 mm height were treated at 1000°C for 14 hours in different baths including either low carbon ferro chromium (LCFC) or high carbon ferro chromium (HCFC) powder. The purpose of this research is to investigate the effect of the salt bath composition on the diffusion of chromium and formation of chromium compound layer on plain carbon steel by using the salt bath method. The coating thickness layers were measured by SEM. The different phases formed on the samples, due to different amounts of carbon in treating salt bath, were determined by X-ray diffraction. It was found that in molten borax salt with high carbon content (high carbon ferro chromium) very few amount of chromium diffused into the plain carbon steel. The thickness of the diffused chromium layer in low and high carbon content ferro chromium in molten borax, is around 32±8 µm and 6.8±1.2 µm, respectively. A number of tests were conducted to address this effect.

Vanadium carbide coating growth on die steel substrate in borax salt bath

Vanadium pentoxide, borax, boron carbide and sodium fluoride were used to grow vanadium carbide coating on die steel(Cr12, Cr12MoV) surface at 950 °C by TD process, which extended the life period of Cr12 and Cr12MoV as punching die. Kinetics of vanadium carbide coating growth was brought forward and verified by comparison of the mathematical model with the experimental results. The thickness of coating was illustrated by SEM. The chemical constituent of coating and remnants were tested by XRD. To increase the thickness, rare earths (FeSiRe23) were added to the borax salt bath. The electronic probe microanalysis (EPMA) revealed that the addition of rare earths could decrease carbon concentration in the coating and increase the depth of vanadium carbide coating.

Effects of rare earths in borax salt bath immersion vanadium carbide coating process on steel substrate

Various amounts of FeSiRe23, which were used as reducing agents, were added into typical borax salt bath used in thermal diffusion (TD) process to explore the effects of rare earths on borax salt bath vanadizing process and microstructure and properties of vanadium carbide coating. The effect results of rare earths on coating thicknesses at different process conditions showed that the right amount of rare earths could greatly accelerate vanadizing rate and that the accelerating effect worked mainly at the initial stage of TD process and decreased with increasing thickness of vanadium carbide layer. Moreover, the comparison of diffusion activation energies at various temperatures revealed that rare earths have optimal accelerating effect at 950 °C or so. The effect results of rare earths on coating microstructure and properties showed that the addition of rare earths into the borax salt bath can decrease grain size and improve fragility of vanadium carbide coating but decrease coating microhardness. And the electron probe microanalysis (EPMA) revealed that the addition of rare earths could decrease carbon concentration in the coating.