X-ray Diffraction Research Articles

Poly(allyl alcohol-co-vinyl acetate)-grafted Concrete Waste for Adsorptive Removal of As(III)

This study focused on the synthesis of concrete waste grafted with a polymer of allyl alcohol and vinyl acetate as a novel nano adsorbent and the investigation of its ability in the adsorptive removal of Arsenic (As(III)) from aqueous solutions. The prepared nano adsorbent was characterized using X-ray diffraction, thermogravimetric analysis, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy. Various parameters were optimized by response surface methodology and central composite design model to achieve the highest As(III) removal efficiency, including the solution's temperature, contact time, and pH. The model predicted a maximum removal efficiency of 92% under the optimal conditions (temperature = 25 °C, contact time = 24 min, and pH = 7), resulting in a sorption capacity of 6.81 mg g-1. The zero point of charge for the nano adsorbent was obtained at about 6.5. The experimental data for As(III) sorption onto the nano adsorbent was well-fitted by the Freundlich isotherm and pseudo-1st-order kinetic models. This suggests that the adsorption process involves the formation of a multilayer of As(III) on the adsorbent surface, and it occurs through physical interactions rather than chemical reactions. The reusability of the nano adsorbent was evaluated, demonstrating a removal efficiency exceeding 72% even after seven recycling cycles. The presence of interfering cations influenced the removal efficiency in the following order: Pb2+>Mn2+>Cu2+>Zn2+>Ni2+. The prepared nano adsorbent showed significant efficiency in removing As(III) from well water and river water samples, with a repeatability range of 1.09-2.51%.

Tuning of structure, surface morphology and optical properties of spray-coated nickel tin oxide thin films by heat treatment

In this work, nickel tin oxide (NiSnO3) in a 1:1 ratio was synthesized using a simple spray pyrolysis technique followed by annealing at 450°C for different time durations. The X-ray diffraction (XRD) revealed the polycrystalline nature with perovskite structure of NiSnO3 without the formation of any secondary phases. Annealing improved the crystallinity of the films. The annealed films exhibited a preference for orientation along the (310) plane. The largest crystallite size was obtained for 4 hours of annealed film. The scanning electron microscopy (SEM) images of the films distinctly illustrate enhanced crystallinity following the annealing process. Energy-dispersive X-ray spectroscopy (EDS or EDX) indicates that the film possesses a near-stoichiometric composition. All the films resulted in more than 70% transmittance in the visible region except for 8 hours annealed. The gradual reduction of energy bandgap was observed for the sample. The four peaks at 358 nm, 415 nm, 436 nm, and 460 nm were observed in photoluminescence (PL) spectra corresponding to near band emission and defects related emissions respectively. The determined optical parameters from the present study indicate that the 4-hour annealed film holds promise as a favourable option for optoelectronic and photonic devices.

Eco-friendly solid waste-based cementitious material containing a large amount of phosphogypsum: performance optimization, micro-mechanisms, and environmental properties

Reusing phosphogypsum (PG) waste to manufacture eco-cementitious materials is sustainable. However, PG faces the challenge of high stacking volume and low utilization rate, and the low-content PG in eco-cementitious materials currently limits its large-scale potential application. This study provides a solution to use high-content PG to fabricate eco-friendly solid waste-based cementitious material (PBC), associated with ground granulated blast furnace slag (GGBS), fly ash (FA), and hydrated lime. Respond surface methodology (RSM) was undertaken to optimize and discuss the influence of independent design factors of GGBS, FA, and hydrated lime content on the unconfined compressive strength (UCS). Besides, the micro-mechanisms and environmental properties of PBC were also investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and the leachate test. The results indicated that the optimal raw material contents were (by mass): 50.57% PG, 28% GGBS, 20% FA, and 1.43% hydrated lime. The UCS of the optimal PBC mixture is 23.57 MPa at 28 days, which was confirmed via experimental verification (24.65 MPa). Hence, the RSM is an effective method for optimizing PBC's UCS. The micro-mechanisms analysis shows that the ettringite is the primary hydration product within the reaction system of PBC, which is attributed to the substantial amount of PG. The leachate test results indicate that the fluoride ion concentration of the leaching solution of PBC remains below the PG, and the pH value falls within the range of 6–9. The leaching test results meet the Chinese environmental standard of GB 8978-1996. The cost and CO2 emission of the optimal PBC mixture could achieve a reduction of 71.25% and 99.98%, respectively, compared to Ordinary Portland cement (OPC). The findings of this study could serve as a theoretical foundation for the practical implementation of large-scale and efficient utilization of PG waste. The developed eco-friendly PBC has excellent potential to partially substitute conventional OPC binders and reduce engineering project costs.

Fundamental structural study of hexagonal boron nitride (h-BN) and boron nitride nanotube (BNNT) at low and high temperatures

The molecular structure stability at low and high temperature is important for an industrial application. The boron nitride-based materials, such as hexagonal boron nitride (h-BN) and boron nitride nanotubes (BNNTs), have been interested due to their high oxidation resistance and thermal stability. In this study, ex-situ and in-situ characterization techniques (e.g., Raman spectroscopy, X-ray Diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR)) were applied to investigate the structural change of BNNT and h-BN at high (up to 800 °C) and low (down to -50 °C) temperatures. The Raman spectroscopy results showed that at high temperatures (800 °C), h-BN exhibited a significant red shift under both inert and oxidizing conditions, while BNNT showed no peak shift, indicating its more stable structural resistance compared to h-BN. Both h-BN and BNNT showed no peak shift after cooling to low temperatures (-50 °C). Stability of h-BN and BNNT up to a high temperature of 800 °C was revealed from the thermogravimetric analysis (TGA) and FTIR spectroscopy results. The FTIR results also indicate that under oxidizing conditions, heating h-BN results in the formation of more hydroxyl groups compared to BNNT. The in-situ XRD results showed a greater magnitude of lower 2θ shift with increasing temperatures for h-BN compared to BNNT. Additionally, there was a more significant increase in FWHM values with respect to temperatures for h-BN than BNNT regardless of the sample under inert or oxidizing conditions. The characterization results from this study indicate that BN-based materials, especially BNNT, are suitable candidates for high temperature chemical reaction applications.

The Nd-Fe-Rh system: Phase relations determination at 600 ℃ and magnetic property measurement of related compounds

The isothermal section of the Nd-Fe-Rh system at 600 ℃ was constructed based on the phase identification and analysis results from annealed alloys using X-ray diffraction and Scanning electron microscopy equipped with Energy dispersive spectroscopy. Two previously reported binary compounds, Nd4Rh and Fe2Nd, could not be confirmed. No new ternary compounds were found in the isothermal section. In the present work, the homogeneity ranges of the Fe-Rh binary system were redefined using phase disappear method, which were determined to be about 70–100 Fe at%, 51–69 Fe at%, 0–45 Fe at% for the single-phase region α-Fe, FeRh and γ-(Rh, Fe), respectively. It was confirmed that the maximum solid solubility of Fe in NdRh2, Nd3Rh and Nd7Rh3 is about 15.6 at% Fe, 4.0 at% Fe and 3.1 at% Fe, respectively, while no appreciable solubility was observed for the other binary compounds in the Nd-Fe-Rh system. The isothermal section of the Nd-Fe-Rh ternary system at 600 ℃ consists of 13 single-phase regions, 23 two-phase regions, and 11 three-phase regions. It suggests the presence of predominant antiferromagnetic exchange interaction in the NdRh compound. For the 38Nd-8Fe-54Rh sample, two magnetic entropy change peaks originate from the combined contribution from two magnetic phase transitions, an antiferromagnetic-paramagnetic transition and a ferromagnetic-paramagnetic transition for NdRh and NdRh2 phase, respectively.

Exploring the machined surface characteristics of Haynes 25 superalloy: Cost mitigation and quality enhancement perspective

The current study investigates the surface characteristics and machining cost of electrical discharge machining (EDM) of Haynes 25 superalloy using tools made by additively manufactured CuCr1Zr, pure copper and graphite. Before assessing machinability, the workpiece and tool materials were characterized using Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD) and evaluations of tensile strength, micro-hardness, density and thermal conductivity. The effects of current (I), voltage (V), pulse duration (Ton), duty cycle (τ) and flushing pressure (Fp) is analyzed on surface characteristics viz. surface roughness (SR), surface crack density (SCD), recast layer thickness (RCT), heat-affected zone (HAZ), micro-hardness (MH) and machining cost (MC). Post machining XRD analysis revealed the formation of cobalt oxides like (CoO and Co3O4) affecting the micro-hardness of the machined surface. Alongside, a field emission scanning electron microscopy (FESEM) is carried out which confirms, the deposition of metal carbides and oxides on the EDMed surface. Current and pulse-on-time significantly influenced performance, with optimal EDM parameters identified and validated through confirmative experiments, resulting in a mean error of ∼2.84%. It is seen that the use of additively manufactured CuCr1Zr tools resulted in improved machined surface characteristics and a more cost-effective approach for producing intricate profiles with minimal surface defects.

Ziziphus Nummularia Leaves Extract Mediated CuO Nanostructures for Photocatalytic degradation of Methylene Blue

In this study, Ziziphus nummularia leaves extract was applied for the synthesis of CuO nanostructures. The material was characterized by various techniques such as Infrared (IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray (EDX) and scanning electron microscope (SEM) analysis. The characteristic peaks in powder XRD pattern of nanostructured of CuO at 2θ of 32.33, 35.57, 38.71, 46.11, 48.80, 51.50, 58.22, 61.58, and 68.08◦, correspond to (110), (-111), (111), (-112), (-202), (112), (202), (-113), and (220), respectively, match with diffraction patter of standard monoclinic phase of CuO (JCPDS: 01-080-1916). Tauc plot was plotted and band gap energy was calculated, and found to be 2.4eV. The material was tested as photocatalyst for degradation of MB, and worked well at optimum parameters such as dosage of catalyst 25mg, concentration of MB 20.0mgL-1, pH 7 and time 120min. The proposed method worked very well on synthetic solutions with degradation efficiency (%) ≥83.51 and an RSD (%) of ≤4.0.

Silver diamine fluoride in preventing enamel erosion: An in vitro study with salivary pellicle

ObjectivesTo compare the prevention of enamel erosion and discolouring effect with a single and two weekly topical applications of silver diamine fluoride (SDF) solution. MethodsHuman enamel blocks were divided into four groups. Group 1 (SDF2) received two weekly applications of SDF solution (Advantage Arrest: 260,000 ppm Ag, 44,300 ppm F, pH 9.1). Group 2 (SDF1) received a single application of SDF solution. Group 3 (SNF, Positive Control) received daily application of stannous-chloride/amine-fluoride/sodium-fluoride solution (Elmex® Enamel professional: 800 ppm Sn(II), 500 ppm F, pH 4.5). Group 4 (DW, Negative Control) received daily application of deionised water. The treated blocks were subjected to a 14-day erosive challenge. Crystal characteristics, elemental composition, surface morphology, percentage of surface microhardness loss (%SMHL), surface loss, and total colour change (ΔE) of the blocks were investigated using X-ray diffraction (XRD), energy-dispersive spectrometry (EDS) and scanning electron microscopy (SEM), Vickers’ hardness testing, non-contact profilometry, and digital spectrophotometry, respectively. ResultsXRD and EDS revealed precipitates of silver for SDF2 and SDF1 and tin for SNF. SEM showed prominent etched enamel pattern on DW than the other three groups. The%SMHL (%) of SDF2, SDF1, SNF, and DW were 26.6 ± 2.9, 33.6 ± 2.8, 38.9 ± 2.9, and 50.5 ± 2.8 (SDF2<SDF1<SNF<DW, p < 0.001). Surface loss (μm) of SDF2, SDF1, SNF, and DW were 3.1 ± 0.6, 3.9 ± 0.6, 3.9 ± 0.7, and 5.5 ± 0.8 (SDF2<SDF1=SNF<DW, p < 0.05). Colour change of SDF2, SDF1, SNF, and DW were 7.9 ± 3.9, 4.0 ± 3.6, 3.6 ± 3.5, and −4.4 ± 3.9 (SDF2>SDF1=SNF>DW, p < 0.05). ConclusionTwo weekly applications was more effective than a single application of SDF in preventing enamel erosion, though it caused more discolouration. Clinical significanceTopical application of 38 % SDF with two weekly applications protocol is effective in preventing enamel erosion.

The structural and digestive properties of indica rice starch-fatty acid complexes

The structural and digestive properties of indica rice starch-fatty acid complexes and the effects of lipoxygenase on the structural and digestive properties of the complexes were examined in this study. The complexes were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy and Raman spectroscopy. The results showed that indica rice starch had the highest molecular chain order and the highest crystallinity, and the crystallization disappeared after gelatinization, and the formation of indica rice starch-fatty acid complexes promoted the transformation of starch crystal structure from A-type to V-type. Lipoxygenase reduced the regularity of starch molecular crystal structure in the complexes, while enzyme protein improved the order of starch molecular structure in the complexes. The regularity of starch crystal structure in the complexes could improve with the increase of composite temperature and the increase of fatty acid unsaturation. In vitro digestibility and in vitro digestion kinetics showed that the formation of indica rice starch-fatty acid complexes reduced the digestibility of indica rice starch to a certain extent. The RDS content of indica rice starch was 66.42 ± 0.39 %, and lipoxygenase reduced the reduction of rapidly digested starch content during complexes digestion, while enzyme protein increased the content of resistant starch.

Hydroxyapatite Derived from Eggshell Embedded on Functionalized g-C3N4 for Synergistic Extraction of U(VI) from Aqueous Solution

In this paper, we report hydroxyapatite derived from egg-shell biowaste embedded on diglycolamic acid functionalized graphitic carbon nitride nanocomposite (abbreviated as HAp@D-gCN). The compositional and morphological characteristics of HAp@D-gCN were evaluated using scanning electron microscopy, X-ray diffraction, BET, FTIR techniques and surface charge using zeta potential measurement. The sorption of U(VI) species on HAp@D-gCN was investigated through batch studies as a function of pH, contact time, initial U(VI) concentration, adsorbent dosage and ionic strength. The adsorption of U(VI) onto HAp@D-gCN was confirmed by FTIR, XRD and EDS elemental mapping. Adsorption kinetics follows pseudo second order model and it attains equilibrium within 20 minutes. Adsorption isotherm data correlates well with Langmuir isotherm model with a maximum sorption capacity of 993.06 mg g−1 at 298K. U(VI) can be leached from the loaded adsorbent using 0.01 M Na2CO3 as desorbing agent and its sorption capacity remains unaffected even after 4 adsorption-desorption cycles. Hence, the present study reveals that HAp@D-gCN nanocomposite could serve as an environmental friendly material with potential application in environmental remediation.

Performance of high-strength green strain-hardening cementitious composites incorporating CSA/CAC cements and GGBS

Strain-hardening cementitious composites (SHCCs) possess crack control and durability properties. In the pursuit of reducing CO2 emissions and addressing potential issues of slow strength development for SHCCs with pozzolans, the objective of this study was to develop high-strength green SHCCs (HSG-SHCCs) that exhibit improved early strength, drying shrinkage, and environmental friendliness. A ternary binder system was proposed, comprising of ground granulated blast furnace slag (GGBS), ordinary Portland cement (OPC), and either calcium sulfoaluminate cement (CSA) or calcium aluminate cement (CAC). The fresh, mechanical, and durability properties of the proposed HSG-SHCCs were experimentally investigated. Additionally, the microstructures and chemical phases of the developed CSA/CAC-GGBS-OPC ternary binder system were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results revealed that the developed HSG-SHCCs demonstrated 6-hour and 28-day strengths of up to 11 MPa and 110 MPa, respectively. The CSA/CAC-based ternary binder system also exhibited enhanced durability and improved drying shrinkage. However, the inclusion of CSA and CAC in HSG-SHCCs could lead to a reduction in tensile performance, specifically in strain capacity. The main hydration products of the CSA/CAC-GGBS-OPC ternary binder system were C-S-H, ettringite, gibbsite, and calcium hydrate. In addition to the fresh, mechanical, and durability properties, the environmental impact of the developed HSG-SHCCs was also assessed. The results indicated that a 30 % replacement of OPC with CSA cement in the HSG-SHCC mix notably improved the trade-off among CO2 emissions, compressive strength, and tensile cracking resistance.

Achieving 2.7 GPa tensile strength in ultrastrong high-carbon steel through prolonged low-temperature tempering

The mechanical properties of high‑carbon martensitic steel are improved by low-temperature tempering. This is due to carbon diffusion and carbide precipitation, which depend on temperature and time. To further improve mechanical properties and develop optimum tempering conditions of the conventional high‑carbon martensitic steel, long-term tempering was carried out at approximately 175 °C and 250 °C. Excellent mechanical properties, which had not been achieved before, were obtained after tempering samples at 175 °C for over 40 d, resulting in tensile strength of 2.7 GPa, yield strength of 2.3 GPa and total strain of 2.6%. Similarly, yield strength values exceeding 2.4 GPa were observed in samples tempered at 250 °C for 5 d. To understand the remarkable outcomes achieved, a detailed investigation into the tempering stages, with the use of Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD) analyses, was essential. The microstructure contained the typical tempered martensite matrix embedded by ultrafine carbides and retained austenite which decomposed slowly with increasing tempering time at 175 °C, contributing to a noticeable increase in strength. Conversely, no pronounced effect of retained austenite was observed on the strength evolution of tempered specimens at 250 °C. At the initial stage of long-term tempering, the primary strengthening mechanism was carbon solid solution strengthening with a value exceeding 1000 MPa. The solid solution strengthening weakened with tempering time, while precipitation strengthening increased with the growth and increasing volume fraction of carbides. The interplay of their effects and the softening of retained austenite led to a trend in which the total yield strength increased, followed by a decrease with increasing holding time. The resulting nuanced mechanical properties and microstructure obtained from long-term tempering offer strategies for synergistic strengthening and ductility of high‑carbon steels, thereby facilitating the expansion of their potential applications.

Promoted stability of Cu/ZnO/Al2O3 catalysts formethanol production from CO2 hydrogenation by La modification

Deactivation of Cu/ZnO/Al2O3 catalysts in CO2 hydrogenation to methanol reaction is one of the main reasons limiting their application. We synthesized a series of La modified Cu/ZnO/Al2O3 catalysts by adding different contents of La to improve the stability. In the 100 h short-term stability test at 200 °C under 3 MPa with a GHSV of 12000 mL/(g·h), the unmodified Cu/ZnO/Al2O3 catalysts degraded obviously over 100 h. In sharp contrast, the stability was significantly promoted by the addition of La. The best activity was achieved with 5% La added samples (4% CO2 conversion and 85% methanol selectivity),which also showed impressive stability over 1000 h except about 17% deactivation during the initial 190−220 h. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results revealed that the addition of 5% La improved the dispersion of Cu and Zn, inhibited the sintering of Cu, stabilized the Cu0/+ species and retarded oxidation of Cu in catalysts, which attributed to the high stability of the catalysts.

Green composites for sustainable food packaging: Exploring the influence of lignin-TiO2 nanoparticles on poly(butylene adipate-co-terephthalate)

Titanium dioxide (TiO2) is a common pigment used in food packaging to provide a transparent appearance to plastic packaging materials. In the present study, poly(butylene adipate-co-terephthalate) (PBAT) incorporated with lignin-TiO2 nanoparticles (L-TiO2) eco-friendly composite films was prepared by employing an inexpensive melting and hot-pressing technique. The P-L-TiO2 composite films have been studied using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), Thermogravimetric analysis (TGA), and Differential scanning calorimetry (DSC) analysis. The FTIR results and homogeneous, dense SEM images confirm the interaction of L-TiO2 with the PBAT matrix. It has also been found that the addition of L-TiO2 nanoparticles can increase the crystallinity, tensile strength, and thermal stability of PBAT. The addition of L-TiO2 increased the tensile strength and decreased the elongation at break of films. The maximum tensile strength of the film, achieved with 5 wt% L-TiO2, was 47.0 MPa, compared with 24.3 MPa for pure PBAT film. The composite film with 5 wt% L-TiO2 has outstanding oxygen and water vapor barrier properties. As the content of lignin-TiO2 increases, the antimicrobial activity of the composite films also increases; the percentage of growth of all the tested bacteria Staphylococcus aureus (S. aureus), and Escherichia coli (E. coli) is significantly reduced. Strawberries were packed to evaluate the suitability of produced composite films as packaging materials, as they effectively preserved pigments from accumulation and extended the shelf-life as compared to commercial polyethylene packaging film.

Novel kosnarite-based M0.5Zr2(AsO4)x(PO4)3-x (M – Sr, Ba and Cd) ceramics for radwaste incorporation

Mineral-like single-phase NZP materials of variable composition M0.5Zr2(AsO4)x(PO4)3−x (M − Sr, Ba, Cd) are of interest as matrices for isolation of high-level Sr, Ba and Cd wastes generated during reprocessing of irradiated nuclear fuel. Such polycrystalline phases were synthesized by sol-gel method with subsequent heat treatment and investigated by X-ray diffraction, IR spectroscopy and electron-probe microanalysis. Rietveld structure refinement showed that the framework is formed by ZrO6 octahedra and mixed AsO4/PO4 tetrahedra connected by vertices; Sr, Ba or Cd cations are located in extra-framework positions. Arsenate-phosphates can be classified as medium thermal expansion materials due to their average coefficient of linear thermal expansion of 2.8∙10−6°C−1. Chemical durability test indicates that the leaching rate of Sr2+ ions from the NZP structure type solid solution is of the order of 10−5 g cm−2 d−1.

Effect of Sintering Temperature on Ceramic Membrane Fabricated Using Coal Flyash and Natural Clay for Lignin Recovery

This study explores the utilization of coal fly ash combined with natural clay as a precursor for creating ceramic membranes through the uniaxial compaction method, aiming at lignin separation. These membranes were sintered at varying temperatures from 600 to 1000 °C. Thermal Gravimetric Analysis (TGA) revealed the robust thermal stability of the membranes. Fourier Transform Infrared (FTIR) analysis affirmed the presence of silica and alumina within the membranes. X-ray Diffraction (XRD) peaks indicated the crystalline structure and the presence of metal oxides originating from the fly ash and clay components. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) images illustrated the porous nature and rough surface of the ceramic membranes. The average pore radius of the fabricated membrane expanded from 43.12 to 7.91 nm with increasing temperature. Concurrently, membrane flux decreased from 4.13 to 0.96 ×10-6 m3/m2 s with higher temperatures. Lower contact angles indicated the hydrophilic properties of membranes. All membranes exhibited superior corrosion resistance and negative zeta potential, owing to the significant silica content in the fly ash. Lignin separation efficiency increased from 65 % to 81 % with increasing temperatures. The optimal sintering temperature was determined to be 800 °C, achieving a lignin recovery greater than 76 % and a membrane permeability of about 7×10-9 m3/m2 s kPa. Thus, the fly ash-clay-based ultrafiltration membranes synthesized in this study offer the potential for lignin biomass recovery from biorefinery effluent.

A Study on the Structural, Wear, and Corrosion Properties of CoCuFeNiMo High-Entropy Alloy

This study investigates the structural properties, wear resistance and corrosion behavior of a CoCuFeNiMo equiatomic high-entropy alloy. The alloy was prepared using a vacuum arc melting device, and its structural properties were analyzed through X-ray diffraction (XRD) and scanning electron microscopy (SEM). Wear tests were conducted using a pin-on-disc machine against 4140 stainless steel at different loads. Corrosion behavior was evaluated through potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in a 3.5wt% NaCl solution. The results indicated the presence of a major face-centered cubic (FCC) phase and a minor (µ) phase. The alloy exhibited segregation of Cu, attributed to positive mixing enthalpy. The coefficient of friction exhibited stability under lower loads but fluctuated under higher loads, possibly due to inhomogeneity in the microstructure caused by Cu segregation. Wear rates increased linearly with applied loads, indicating a direct relationship between load and wear properties. The worn surfaces displayed characteristics of mild abrasive wear, with delaminations, ploughing, and abrasive wear tracks. Pitting corrosion was observed, and the corrosion process was explained as the attack of Cl- ions leading to galvanic corrosion between different phases. In the corrosion analysis, the Ecorr value was -0.616V, and the icorr value was found to be 2.22 × 10-5 A/cm2.

Structural, optical and electrochemical properties of Sr-doped ZnO nanoparticles

The Sr-doped ZnO nanoparticles have been synthesized by the chemical precipitation method at room temperature. The prepared nanoparticles are annealed at 500 °C for 4 hours. The nanoparticles have been characterized using X-ray diffraction (XRD) technique, scanning electron microscope and UV-Vis spectroscopy. The XRD studies reveal the formation of a wurtzite geometry. The crystallite size, dislocation density and strain are examined as a function of Sr-doping concentration. The band gap of the prepared nanoparticles ranges from 3.46 eV to 3.56 eV. The nanoparticles have a higher hole concentration than electron concentration. Supercapacitor cells have been prepared by using synthesized nanoparticle electrodes and it is characterized using cyclic voltammetry (CV) by using KOH as an electrolyte solution. The calculated specific capacitance is high at a high doping concentration of ‘Sr’.

NiOx Passivation in Perovskite Solar Cells: From Surface Reactivity to Device Performance.

Nonstoichiometric nickel oxide (NiOx) is one of the very few metal oxides successfully used as hole extraction layer in p-i-n type perovskite solar cells (PSCs). Its favorable optoelectronic properties and facile large-scale preparation methods are potentially relevant for future commercialization of PSCs, though currently low operational stability of PSCs is reported when a NiOx hole extraction layer is used in direct contact with the perovskite absorber. Poorly understood degradation reactions at this interface are seen as cause for the inferior stability, and a variety of interface passivation approaches have been shown to be effective in improving the overall solar cell performance. To gain a better understanding of the processes happening at this interface, we systematically passivated specific defects on NiOx with three different categories of organic/inorganic compounds. The effects on NiOx and the perovskite (MAPbI3) deposited on top were investigated using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Here, we find that the perovskite's structural stability and film formation can be significantly affected by the passivation treatment of the NiOx surface. In combination with density functional theory (DFT) calculations, a likely origin of NiOx-perovskite degradation interactions is proposed. The surface passivated NiOx layers were incorporated into MAPbI3-based PSCs, and the influence on device performance and operational stability was investigated by current-voltage (J-V) characterization, impedance spectroscopy (IS), and open circuit voltage decay (OCVD) measurements. Interestingly, we find that a superior structural stability due to interface passivation must not relate to high operational stability. The discrepancy comes from the formation of excess ions at the interface, which negatively impacts all solar cell parameters.

Improvement in electrochemical performance of SrTiO3 with rGO via composite (SrTiO3/rGO) strategy fabricated via solvothermal approach

Developing sustainable and highly effective electrocatalysts for the oxygen evolution reaction (OER) is a significant research target for precise custody of water splitting to fulfill worldwide energy demands. This study focuses on the fabrication of SrTiO3/rGO-based composite via a solvothermal technique, which works as an electrocatalyst for evaluating the efficiency of OER in alkaline media. The material displays outstanding OER efficacy in 1 M KOH solution, with its cubic structure validated by the X-ray diffraction (XRD) study. The electrochemical study reveals that the SrTiO3/rGO composite has a minimal overpotential (222 mV) compared to SrTiO3 (289 mV) and the commercial catalyst RuO2 (367 mV). The SrTiO3/rGO composite also has a minimal Tafel plot gradient of 37 mV dec−1 whereas RuO2 has a Tafel value of 72 mV dec−1. The current material has superior properties compared to RuO2, a commercial catalyst for the OER. The SrTiO3/rGO composite shows exceptional stability for 40 h. The low conductivity of oxygen-deficient SrTiO3 perovskite can be improved by incorporating carbon-based rGO into it, as demonstrated by the minimal Rct (0.07 Ω) obtained from electrochemical impedance spectroscopy (EIS) analysis and an enlarged surface area of 250 cm2, as evidenced by electrochemical surface area (ECSA). Therefore, our research indicates that a particular morphology of metal oxide can improve the efficiency of electrocatalysis when combined with reduced graphene oxide (rGO), suggesting its potential for generating effective and environmentally friendly energy. Hence, these findings may improve the smooth passage of electrons and provide a novel perspective to function as an adequate substitute for RuO2, a commercial catalyst.