X-ray Mapping Techniques Research Articles

CaTiO3 perovskite /g-C3N4 heterojunction-based composite photocatalyst, part II: Synthesis, characterization and the boosted photocatalytic activity towards Gemifloxacin

BackgroundDue to the potential ecosystem protection and management applications, searching to achieve highly optimized semiconductor-based photocatalysts utilizing solar energy is still a significant challenge. MethodsThus, CaTiO3/g-C3N4 heterostructures synthesis via in-situ calcination method was synthesized here, and its structure was investigated by different characterization techniques such as FT-IR, XRD, SEM, EDX, X-ray mapping, cyclic voltammetry (CV), EIS, and DRS techniques. Significant findingsThe average crystallite size of the composite sample was estimated at 3.8 nm and 3.5 nm, respectively, according to the Scherrer and Williamson-Hall using XRD results. pHpzc values were approximately 8.6, 5.5, and 6.5 for CaTiO3, g-C3N4, and CaTiO3/g-C3N4 samples. Based on the DRS data, the evaluated band gap energy for the g-C3N4, CaTiO3, and CaTiO3/g-C3N4 were 2.76, 3.5, and 2.6 eV, respectively. EIS and CV data confirmed better charge carriers' transfer in the composite. The proposed CaTiO3/g-C3N4 composite showed a synergistic effect in the photodegradation of Gemifloxacin in an aqueous solution under both UV and Vis light illumination. Changes in the CaTiO3:g-C3N4 ratio varied the photocatalytic activity of the obtained catalyst.

Ultrasound-enhanced dispersive solid phase extraction of Cd (II), Co (II), and Ni (II) using magnetic Pinus pinea

A new ultrasound assisted dispersive solid phase extraction (DSPE) technique has been combined with flame atomic absorption spectrometry (FAAS) to enable the simultaneous preconcentration, determination and removal of cadmium, cobalt and nickel ions from aqueous samples. In this procedure, a magnetic Pinus pinea bio-adsorbent was synthesized and used as bio-adsorbent. The parameters such as solution pH, ultrasound time, analyte concentration and interfering ions were successfully optimized. All three metal ions were extracted within a mere 120 s at pH 6 and the extraction recovery values of the all three analytes were quantitative (˃95%) under the optimal conditions. The adsorption processes of the metal ions were analyzed and adsorption of the metal ions were identified by Energy Dispersive X-Ray Mapping technique. A certified reference material was analyzed for the accuracy of the method. Finally, the developed method was applied for preconcentration and determination of the analytes in real water samples including natural spring water, natural mineral water and factory process water.

Enhancement in wear-resistance of 30MNCRB5 boron steel-substrate using HVOF thermal sprayed WC–10%Co–4%Cr coatings: a comprehensive research on microstructural, tribological, and morphological analysis

The rotavator blade, a part of an agricultural equipment rotavator, is used for the soil bed preparation. These blades have direct interaction with soil in agricultural land. Bad, rocky, gravel, sandy, and high rough-hard texture of soil are the main factor to damage the surface of the rotavator blade and a high wear rate is observed. This causes to decrease in the overall life of a rotavator blade. It also changes the geometry of the rotavator blade after a few operations, and that all effects the performance capability of this blade. Hence HVOF (High-velocity oxy-fuel) is used to modify the surface that improved wear resistance of the rotavator blade's surface. Feedstock powder used for the coating is WC–10%Co–4%Cr with Ni–20%Cr as a bond coat on 30MNCRB5 steel substrate (Rotavator blade's material). Six samples are prepared to test it on the Pin-On-Disc wear testing apparatus to determine the wear rate, weight loss, cumulative volume loss and linear wear rate, three bare 30MNCRB5 steel and three WC–10%Co–4%Cr coated samples are prepared with 8 mm diameter and 30 mm length in a cylindrical pin shape. Coated samples are characterized using the XRD (X-ray diffraction), SEM (Scanning electron microscope) with EDAX (Energy-dispersive spectroscopy), and X-ray mapping techniques. Worn out surfaces of bare 30MNCRB5 steel and WC–10%Co–4%Cr coated samples are investigated using the SEM (Scanning electron microscope) to study the microstructure of worn surface that helped out to identify the wear behavior. The HVOF (High-velocity oxy-fuel) spray coating drastically improved the surface to defend it from wear, and very less weight loss was seen in the WC–10%Co–4%Cr coated samples as compared to bare 30MNCRB5 steel material. Weight loss determined by the bare (30MNCRB5) material at 40N, 50N, 60N loads are 2.996 × 10−3 Kgm, 3.003 × 10−3 Kgm, 3.123 × 10−3 Kgm, and coated (WC–10%Co–4%Cr) sample at 40N, 50N, 60N loads are 0.006 × 10−3 Kgm, 0.030 × 10−3 Kgm, 0.038 × 10−3 Kgm respectively.

Synergistic photocatalytic activity of PbS/clinoptilolite in ciprofloxacin photodegradation: An experimental design study

PbS was loaded in clinoptilolite nanoparticles (NCP) through the ion exchange and precipitation processes (PbS- NCP). XRD, FTIR, SEM-EDX, X-ray mapping, and DRS techniques were then used to identify the samples. The pHpzc of PbS- NCP was estimated at 7.1. The boosted photocatalytic activity of PbS- NCP was observed toward ciprofloxacin (CPX). The influencing variables' simultaneous interaction effects were then studied by experimental design via response surface methodology (RSM). The optimal RSM condition run included pH 7, a catalyst dose of 1/5 g/L, and 4/75 mg/L of CPX at an irradiation time of 17 min. After four reusing runs, the catalyst reused and retained about 76% of its initial activity.

Simple synthesis of the novel Cu-CYA coordination polymer and its application as a green and recoverable catalyst for the asymmetric Hantzsch synthesis of polyhydroquinoline derivatives

This study designed and fabricated a novel, Cu-containing coordination polymer system via a hydrothermal reaction of copper salt with cyanuric acid as a tridentate ligand. The prepared coordination polymer was investigated by XRD, BET, SEM, EDS, FT-IR, and X-ray mapping techniques. The prepared Cu-CYA coordination polymer exhibits good catalytic activity in the synthesis of polyhydroquinolines under gentle reaction conditions in short reaction times. Furthermore, this nanostructure afforded a few benefits, which include excessive yields, short reaction times, stability, easy methodology, easy workup, and greener situations. Furthermore, the activity of the recycled catalyst was examined for at least five cycles with a negligible loss of its activity.

Economical and efficient dye sensitized solar cells using single wall carbon nanotube-titanium dioxide nanocomposites as photoanode and SWCNT as Pt-free counter electrode

Economical and efficient dye sensitized solar cells (DSSC) were fabricated using single wall carbon nanotube and titanium dioxide [SWCNT-TiO2] nanocomposite as photoanode and SWCNT as Platinum free (Pt-free) counter electrode (CE). By physical mixing, precise amounts (0.006 wt%, 0.018 wt%, 0.03 wt%, and 0.06 wt%) of SWCNT was mixed in TiO2 nano particles paste to obtain nanocomposite paste [nSWCNT-TiO2] for the anodes. Attachment and distribution of SWCNT within/among the TiO2 components has been confirmed using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and X-ray mapping techniques. The catalytic activity and stability of the SWCNT as catalyst in the CE of fabricated DSSCs have been appraised using cyclic voltammetry (CV), Tafel, and chronoamperometry characterizations. Finally, the fabricated solar cells have been evaluated by current–voltage characteristics (IV) and electrochemical impendence spectroscopy (EIS). The optimized cell containing 0.018 wt% of SWCNTs mixed in TiO2 paste i.e. [0.018 %SWCNT-TiO2] for anode preparation and SWCNT as Pt-free CE i.e. [0.018 %SWCNT-TiO2/N3/SWCNT] showed an overall efficiency of 8.05 %, which is about 44 % higher than the conventional [TiO2/N3/Pt] based solar cell fabricated under the same conditions. This improvement in the overall power conversion efficiency (PCE) can be ascribed to the improved electron collection at photo-anode i.e. reduced charge recombination, efficient electron transport, good catalytic activity of the SWCNT at CE, and enhanced light harvesting efficiency due to the more dye adsorption.

Hot corrosion and air oxidation behavior of pulsed current gas tungsten arc welded and CO2 laser beam welded SMO 254 at 800 °C

This research aims to investigate the hot corrosion behaviour of SMO 254 steel samples after PCGTA and CO2 laser beam welding, as well as air oxidation. A salt mixture simulated the waste incinerator environment involving 40 wt. % Na2SO4 + 40 wt. % K2SO4 + 10 wt. % NaCl + 10 wt. % KCl are employed. The hot corrosion tests were carried out for 103.33 h at 800 °C, with a thermogravimetric investigation availed to calculate the impact of corrosion. The weight gain rate for PCGTAW molten salt corroded specimens is greater (33.45 mg/cm2) than the weight gain rate for CO2 Laser molten salt corroded specimens, which is 67.55% higher. The weight of the hot corroded sample rises in the molten salt surroundings due to the creation of compounds including CrS, FeMo2S4, Na2S, Fe2O3, K2S3, Cl4CrNa2. CO2 LBW air oxidation has the lowest rate of corrosion due to the synthesis of beneficial oxides, such as NiCr2O4, NiO, and Cr2O3. Optical microscopy and SEM/EDS were employed on both surface and cross-sectional surfaces to get microstructure at the interface of the fusion region, parent metal, and fusion region using point mapping, line mapping, and X-ray mapping techniques. The corrosion products produced during corrosion were studied using XRD.

Improvements on hot corrosion behaviour of HVOF coated CO2 laser beam and pulsed gas tungsten arc weldments in 2.5% sulphur gas plus molten salt in industrial waste incinerator environment

This research article discusses in detail how the‌ ‌rate‌ ‌of‌ ‌corrosion‌ ‌increases‌ for the Alloy 254 in the ‌molten‌ ‌salt‌ ‌mixture‌ ‌of‌ ‌10‌ ‌wt%‌ ‌NaCl‌ ‌+ 40‌ ‌wt%‌ ‌K‌2‌SO‌4‌ + 40‌ ‌wt%‌ ‌Na‌2‌SO‌4‌ ‌+‌ ‌10‌ ‌wt%‌ ‌KCl‌ ‌and‌ ‌corrosive‌ ‌gas‌ combination of ‌ ‌2.5‌%‌ ‌SO‌2‌ ‌+‌ ‌3‌%‌ ‌O‌2‌ ‌+‌ ‌25‌%‌ ‌CO‌2‌ ‌+‌ ‌69.5‌%‌ ‌N‌2 in simulated municipal‌ ‌solid‌ ‌waste‌ ‌‌incinerator environment at 700 °C and 800 °C.‌ ‌In addition, the article shows rate of ‌thermal corrosion abridged due to the addition‌ ‌of‌ ‌80‌ ‌Ni-‌ ‌20‌ ‌Cr‌ ‌-‌High-velocity oxygen fuel ‌coating‌ ‌on‌ ‌the‌ ‌SMO‌ ‌254‌ ‌specimen. Thermogravimetric analysis is adapted to analyze the corrosion rate. A‌ ‌higher‌ ‌hardness‌ ‌was‌ ‌obtained‌ ‌for‌ ‌the‌ ‌High-velocity oxygen fuel coated‌ ‌specimen‌ ‌than‌ ‌that‌ ‌of‌ ‌base‌ ‌metal.‌ ‌Surface‌ ‌roughness‌ ‌was‌ ‌measured‌ ‌on‌ ‌the‌ ‌thermal‌ ‌barrier‌ ‌coated‌ ‌surface.‌ As a result of the impact of molten salt and corrosive gas, hot corrosion by-products such as ‌sulphides, chlorides‌ ‌and‌ ‌Na‌ are produced, which are observed to increase the severity of corrosion rate. ‌‌ The study provides a detailed analysis of the metallurgical changes along the cross-section on the hot corroded samples by optical and Scanning electron microstructural image analysis. X-ray diffraction analysis was used to know about the corrosion products formed during corrosion. Formation‌ of the major protective oxide phases such as NiCr2O4, Cr2O3, NiO and CrMnO4 provide better corrosion resistance to the substrate in the coated samples. The diffusion of the corrosive elements along the cross-section of the weld interface, weld zone, and base metal zone was analyzed in detail using Electron dispersive spectroscopy‌ ‌data in the point scan, line scan, and x-ray mapping techniques. Thermal spray coatings were found to be effective to prevent the hot corrosion, however, a higher weight gain (17.75 mg cm−2) was observed on the pulse current gas tungsten arc weldment sample in the simulated environment compared to a weight gain (2.66 mg cm−2) base metal specimen at 700 °C. Spallation of coated surface occurred at 800 °C, and it could be concluded that the coating has found to be effective in preventing the hot corrosion and safe to operate at a temperature of 700 °C for Alloy 254 in this aggressive simulated environment.

Elevated temperature erosive wear behavior of superalloy coatings deposited using cold spray technology

The boiler tube components in thermal power plants and steam generating systems suffer from erosion and corrosion problems and are even today posturing a grave threat to industries, resulting in forced outages. Unrelenting efforts to decrease the components’ maintenance costs have been made by protecting with coatings. Among the various coating methodologies are thermal spray, chemical vapour deposition (CVD), physical vapour deposition (PVD), etc., in vogue. However, recently, the additive manufacturing-based cold spray technique is gaining interest among material scientists, incorporating high-velocity impacts associated with the low-temperature regime. Nickel-based superalloy Inconel 625 has been chosen and cold sprayed on The American Society of Mechanical Engineers (ASME) T11 and T22 boiler steels. The coated surface is characterized by scanning electron microscopy and energy dispersive X-ray analysis (EDAX), X-ray diffraction, micro-hardness, and elemental X-ray mapping techniques. The solid particle erosion studies have been carried out both at room and an elevated temperature of 700 °C as per American Society for Testing and Materials (ASTM) standard for 30°C and 90 °C impact angles. An optical profilometer has been used to evaluate the erosion volume loss. The results showed that the coated samples exhibit superior erosion resistance than the uncoated samples at both room and elevated temperatures. The erosion data obtained have been substantiated using scanning electron microscopy by analyzing the damage features and correlating with the erosion data.

Lead biosorption by magnetic Pisum sativum peel biocomposite using experimental design

ABSTRACT The Pisum sativum has been used as a magnetic biocomposite biosorbent for the removal of lead ions from aqueous solutions. These biocomposites were prepared with encapsulated alginate beads into calcium chloride solution, Pisum sativum peel powder and iron (II–III) oxide. Properties of surface and the possible binding sites of the material were evaluated by instrumental analysis using Fourier transform infrared spectroscopy-attenuated total reflection, scanning electron microscope, and X-ray diffraction. Scanning electron microscopy–energy-dispersive X-ray spectroscopy and mapping techniques are also used for evaluation of process. Optimisation of biosorption procedure was done by Plackett–Burman factorial design including parameters such as biocomposite amount, pH, temperature and extraction time. The analytical performance of the biosorption method, application to industrial effluent, the reusability and stability of biosorbent were also investigated. The Pisum sativum magnetic biocomposite adsorbed 90 ± 4% of lead at the optimum pH value 4 and 125 mg biocomposite amount. The best-fitting isotherm model is Freundlich and theoretical capacity of biosorbent was calculated as 74.05 mg/g. The report of magnetic Pisum sativum biocomposite as a biosorbent may be used as natural renewable resources and reduces the adverse effects on water contaminated for lead.

Boron- and nitrogen-doped graphene quantum dots with enhanced supercapacitance

Graphene quantum dots (GQDs) with their very large specific surface area and numerous edges can offer promising novel features as metal-free and inexpensive electrodes of supercapacitors. Here, we investigated the effect of boron and nitrogen doping in GQDs on their electrochemical energy storage properties. The GQDs as well as B-GQDs and N-GQDs were synthesized by a facile hydrothermal method and characterized by X-ray diffractometry, UV-Vis absorption spectrophotometry, transmission electron microscopy, and energy-dispersive X-ray mapping techniques. Electrochemical properties of the nanoparticles were investigated in a three-electrode setup using cyclic voltammetry and galvanostatic charge/discharge techniques in KOH electrolyte. The N-GQDs electrode showed the highest specific capacitance of 283 F/g at 1 A/g as compared to the GQDs and B-GQDs electrodes. The N-GQDs electrode exhibited the specific energy and specific power of 6.2 Wh/Kg and 108 W/Kg, respectively. The N-GQDs electrode showed also better cycling stability (80% capacity retention) than the GQDs and B-GQDs electrodes.

Development of magnesium oxychloride cement with enhanced water resistance by adding silica fume and hybrid fly ash-silica fume

In this paper, a water-resistant magnesium oxychloride cement (MOC), an environment friendly cementitious material, was developed by incorporating silica fume and the hybrid of silica fume and fly ash. The effects of these admixtures on the water repellence of MOC were investigated via comprehensive macroscopic physical and mechanical tests and micro-scale studies. A formula design of MOC blended with 15% silica fume and 15% fly ash retained the compressive strength as high as 100% and 95% after 28 days' and 56 days’ immersion in water, respectively. Micro-scale studies, including XRD, FTIR, SEM, MIP, TG/DSC and XRM, were conducted to discover the mechanism of the enhanced water resistance of the new MOC. Besides, a clear and precise distribution of the hydration products in well-cured MOC specimens was demonstrated with the X-ray mapping (XRM) technique. It was found that adding silica fume or the hybrid of silica fume and fly ash optimised the porous structure of MOC and thereby increased the density and compressive strength leading to the enhanced water resistance. The filling effect of fine silica fume and fly ash particles, as well as the formation of Mg–Cl–Si–H gel, was found to be the main reason for the densified microstructure of MOC. The fractional contribution of phase 5, i.e. the main phase of MOC, decreased with the combined silica fume and fly ash, and this helped to relieve the internal stress and improve the stability of MOC, leading to enhanced water repellence.

Mesoporous SBA-15@n-Pr-THAM-ZrO organic–inorganic hybrid: as a highly efficient reusable nanocatalyst for the synthesis of polyhydroquinolines and 2,3-dihydroquinazolin-4 (1h)-ones

In this work, tris(hydroxymethyl)aminomethane-Zirconium complex supported on modified SBA-15 (SBA-15@n-Pr-THMAM-ZrO) prepared as a novel mesoporous catalyst. The structure of this porous compound was characterized by XRD, nitroge adsorption–desorption, TEM, TGA, EDS, ICP, X-ray mapping, and SEM techniques. The catalytic activity of SBA-15@n-Pr-THMAM-Zr has been investigated for the multicomponent synthesis of polyhydroquinoline and 2,3-dihydroquinazolin-4(1H)-one derivaives.

Extending the luminescence properties of zinc gallogermanate via co-doping with cost-effective metals ions (Cr3+/Mg2+, Cr3+/Ca2+, and Cr3+/Sr2+)

The huge applications of red-light-emitting materials paying the research attention to reduce the cost of production and raw materials. Therefore, abundant cations of alkaline-earth metals, e.g., Mg2+, Ca2+, and Sr2+ were successfully incorporated with Cr3+: Zn3Ga2Ge2O10 (Cr-ZGGO) as co-activators via simple solid-state method. The X-ray diffraction results of all samples confirmed the formation of zinc gallogermanate superstructure with two cubic phases ZnGa2O4 and Zn2GeO4. The particle imaging of Cr-ZGGO and Ca@Cr-ZGGO via field emission scanning electron microscopy reveals a significant change in morphology and particle size by Ca2+ co-doping. Meanwhile, the energy dispersive X-ray spectroscopic analysis and mapping techniques elucidate the exact chemical composition of the calculated stoichiometric substitution and illustrate the equal distribution of all elements over the whole sample. Optical bandgap energy of Mg2+, Ca2+, and Sr2+ co-doped phosphors are lower than Cr-ZGGO. The Sr@Cr-ZGGO displays the most intense photoluminescence peak and the broadest emission in the near-infrared region as a result of increasing light traps and generation of new paths between the energy levels of trapping centers.

Homogeneous Coatings of Titanium Dioxide Nanoparticles on Corona-Treated Cotton Fabric for Enhanced Self-Cleaning and Antibacterial Properties

Abstract This study discusses the effect of corona pretreatment and subsequent loading of titanium dioxide nanoparticles on self-cleaning and antibacterial properties of cellulosic fabric. The corona-pretreated cellulosic fabrics were characterized by field emission scanning electron microscopy, and X-ray mapping techniques revealed that layers of the titania deposited on cellulose fibers were more uniform than the sample without pre-corona treatment. The self-cleaning property of treated fabrics was evaluated through discoloring dye stain under sunlight irradiation. The antibacterial activities of the samples against two common pathogenic bacteria including Escherichia coli and Staphylococcus aureus were also assessed. The results indicated that self-cleaning and antibacterial properties of the corona-pretreated fabrics were superior compared to the sample treated with TiO2 alone. Moreover, using corona pretreatment leads to samples with good washing fastness.

In situ integrated 2D reduced graphene oxide nanosheets with MoSSe for hydrogen evolution reaction and supercapacitor application

The electrochemical hydrogen evolution reaction (HER) and supercapacitor are regarded as promising tools to meet the existing energy demand around the world. The non-noble metals such as Mo, W based dichalcogenide electrocatalysts are considered as highly catalytic active materials due to its chemical stability, active edge sites and tunable electronic structure. Here, we have prepared different Mo and W based dichalcogenides such as molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2), molybdenum sulfoselenide (MoSSe), tungsten disulfide (WS2), tungsten diselenide (WSe2) and tungsten sulfoselenide (WSSe) nanostructures as a bifunctional electrode material for HER and supercapacitor application. Further the incorporation of two dimensional (2D) nanosheets such as reduced graphene oxide (rGO) into MoSSe (MoSSe/rGO) or WSSe (WSSe/rGO) has altered the electrically conducting active edge sites to ease out the adsorption of hydrogen. Moreover the obtained composite materials were prepared by simple one pot hydrothermal method and characterized by X-ray diffraction analysis (XRD), Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) mapping techniques. In HER activity studies, MoSSe/rGO shows a minimum overpotential of 285 mV at 10 mA cm−2 current density with the Tafel slope of 98 mV dec−1. Besides, good cyclic stability property upto 1000 cycles was observed. In supercapacitor studies, MoSSe/rGO composite shows the specific capacitance of 373 Fg−1 at 1 Ag−1 current density. The synergistic effect between MoSSe and rGO nanosheets via electrostatic interaction makes the composite material as strong. As a result, during the cyclic study, among different Mo and W based dichalcogenides, MoSSe/rGO composite electrode shows high stability towards HER and supercapacitor.

N2O decomposition properties of Ru catalysts supported on various oxide materials and SnO2

Nitrous oxide (N2O) is a stratospheric ozone depleting greenhouse gas that has global warming potential. As the catalytic decomposition of N2O is one of the most promising techniques for N2O emissions abatement, in this study, for this purpose the properties of Ru supported on various oxide materials were investigated under excess O2 conditions, and the identities of the N2O adsorption species on the catalysts were confirmed. To clarify the correlation between the catalytic properties and N2O decomposition activity, the supported Ru catalysts were characterised by means of powder X-ray diffraction, X-ray fluorescence measurements, energy-dispersive X-ray mapping and several gas sorption techniques. The results showed that the redox properties for Ru (RuO2) at low temperature are closely associated with N2O decomposition activity. The local structures, optimal Ru loading and N2O adsorption species of the novel Ru/SnO2 catalysts were studied and they showed high activity for N2O decomposition.

(Invited) Evaluation of 2" Power-Grade GaN Substrates Produced By the Near Equilibrium Ammonothermal (NEAT) Method

This paper provides evaluation of 2" GaN substrates produced by the near equilibrium ammonothermal (NEAT) method. Ammonothermal growth is a proven method of producing low-dislocation GaN crystals with practical productivity. [1, 2] By choosing a near-equilibrium growth condition, consistent growth with maintained crystal quality has been achieved. [3] Several tens of bulk GaN crystals were grown simultaneously, yielding many 2" GaN substrates in one growth batch. Figure 1 is an example of bulk GaN crystals after shaping and Figure 2 is an example of 2" GaN wafer.We have developed an X-ray mapping technique which presents the distribution of full width half maximums (FWHMs) of rocking curves from 002 and 201 diffractions over a 2" wafer. The X-ray mapping revealed superior microstructure quality of NEAT GaN substrates. NEAT GaN substrates typically show an average full width half maximum (FWHM) of the 002 X-ray rocking curve of 30 arcsec or better, as shown in Figure 3.The X-ray mapping data were compared with other characterization techniques, including X-ray topography. X-ray topography confirmed that a dislocation density of typical NEAT GaN substrate was about 2 x 105 cm-2. Wide area X-ray topography also revealed flatter lattice of a NEAT GaN substrate compared with a GaN substrate fabricated by hydride vapor phase epitaxy (HVPE).Additionally, recent progress in oxygen reduction yielded NEAT GaN substrates with reduced residual donors, coloration and optical absorption. The oxygen concentration was about 2 x 1018 cm-2. An absorption coefficient of 1.3 cm-1 was obtained at 450 nm.The usability of NEAT GaN substrates was also confirmed through device fabrication. Multiple collaborators successfully fabricated high-power diodes with breakdown voltage over 1000V.

Evaluation of hot corrosion performance of HVOF coatings on PCGTA welded Fe-based alloy A-286 in Na2SO4%-7.5%NaVO3%-5%NaCl environment

This research article investigated the hot corrosion behaviour of the pulsed current gas tungsten arc (PCGTA) welded Fe-based alloy A-286. PCGTA welding is employed to obtain a similar joint of 6 mm plates of A-286 alloy using ER-320LR filler material. A high-velocity oxy-fuel (HVOF) coating is carried out to deposit Cr3C2-25%NiCr and Ni-20%Cr coating on the PCGTA weldments. The microstructure and elemental analysis of the surface and cross-sections of the coatings were examined by Scanning electron microscope (SEM) combined with energy dispersive spectroscopy (EDS). Hot corrosion study is carried out on bare, and HVOF coated PCGTA weldments in Na2SO4-7.5%NaVO3-5%NaCl environment at 850 °C. The corrosion frate of the weldments was determined by thermogravimetric analysis. The reaction products present in the weldments were characterized by SEM and x-ray diffraction (XRD) analysis. Depths of corrosion attack and elemental distribution on the weldments at cross-section are analyzed using EDS with the x-ray mapping technique. The Cr3C2-25%NiCr coated weldment exhibits the superior corrosion resistance than bare and the Ni-20%Cr coating due to the development of chromium oxide (Cr2O3) scales. The chromium carbide coating has a reduced weight gain of 56% and 25% compared to uncoated, and Ni-20%Cr coated specimens.

Effect Of Magnesium Perchlorate Content on the Mechanical, Thermal Stability, and Dielectric Properties of Plasticized PMMA/PVC-g-PMMA Electrolytes

In this study, new types of gel polymer blend electrolytes (GPBEs) were prepared with the synthesized PVC-g-PMMA graft copolymer, PMMA, plasticizers (propylene carbonate (PC), dioctyl phthalate (DOP)), and different loadings of Mg(ClO4)2 via the solution casting method using tetrahydrofuran as solvent. Fourier transform infrared (FTIR) spectra of the electrolytes showed mutual molecular interactions between Mg(ClO4)2 and organic moieties. The scanning electron microscopy images of the GPBEs showed their wrinkled surface morphology due to their low elastic modulus and high flexibility. Energy-dispersive X-ray (EDX) spectroscopy and mapping technique revealed the regular distributions of all atomic elements such as Cl, Mg, O, and C in the doped GPBEs. With increasing the Mg salt concentration, Young’s modulus and tensile strength of the GPBEs strongly decreased. Interestingly, the elongation at break of the GPBEs was higher than that of neat (undoped) GPBE and achieved the highest value of 215% at the salt content of 20 wt.%. The AC conductivity and ionic conductivity, as well as dielectric permittivity of plasticized PMMA/PVC-g-PMMA/Mg(ClO4)2 GPBE,s increased with frequency and Mg(ClO4)2 doping content. Ionic conductivity of the doped GPBEs can be achieved from 5.51 × 10 − 5 to 4.42 × 10 − 4 (S.cm-1) using Mg(ClO4)2 contents in the range from 10 to 40 wt.%. The doped GPBEs are thermally stable up to 100°C with very low weight losses. The GPBE doped with 20 wt.% of Mg(ClO4)2 can be used as a new type of electrolyte for developing Mg batteries.