Present study discusses about a technique for producing high-purity Cr2AlC MAX phase materials and gaining insight into their thermal behavior for high-temperature applications. The research conducted involved synthesizing a pure layered ternary carbide Cr2AlC MAX phase material by mixing powders of Chromium, Aluminum, and Carbon and then subjecting them to two-step pressureless sintering process in argon atmosphere. First step involves the annealing of ball-milled mixture at 750 °C for 2 h followed by the second step in which the annealed mixture is subjected to heat-treatment at 1350 °C for 2 h. Analysis using XRD and Raman techniques revealed that the synthesized product consists of Cr2AlC phase, without any impurities. SEM studies confirmed that the Cr2AlC had a layered topography, while EPMA analysis indicated that the atomic percentage of Cr, Al, and C was consistent with the XRD phase analysis. XPS investigations confirmed the presence of Cr-C bonds representing Mn+1Xn of the MAX phase material. TG-DSC results showed an approximately 2

Aluminium 6061 has a widespread applications in the automotive and aerospace sectors. However, because of its poor tribological properties, its life is limited. In this investigation, a surface composite of Ti3AlC2 and Al 6061 alloy was prepared using friction stir processing and its effects have been studied. The examination of microstructure of the fabricated samples were studied using optical microscopy and scanning electron microscopy. The microstructural analysis revealed reduction in grain size within both the base metal FSPed and aluminium- Ti3AlC2 composites. The area mapping showed uniform dispersion of Ti3AlC2 particles within the friction stir processed zone. The microstructure refinement lead to increase in the microhardness. The average microhardness of the base metal was 65 HV0.2 and that of base metal FSPed and Al- Ti3AlC2 were 85 HV0.2 and 135 HV0.2. The grain refinement and uniform distribution of particles were found responsible for the improvement in wear properties. It was observed that the wear resistance improvement of more 100 percent in comparison to the parent metal. The predominant wear mechanism, as demonstrated by scanning electron microscopy micrographs, was abrasive wear with varying degrees and features.

This study presents a novel and eco-friendly method for synthesizing ammonium nitrate (NH₄NO₃) using plasma-activated water (PAW) prepared through air and ammonia (NH₃) plasma treatments. Initially, PAW containing nitrate ions (NO₃ˉ) is produced by treating water with air plasma. This PAW (air) is then frozen and exposed to low-pressure NH₃ plasma, introducing ammonium ions (NH₄⁺) to form NH₄NO₃ (PAW (air+NH3)). We systematically investigate the voltage-current characteristics of the air and NH₃ plasmas, analyze the generated species and radicals to understand the mechanism of NH₄NO₃ formation, and evaluate the effects of process parameters such as NH₃ gas pressure, applied voltage, and treatment time on the properties of PAW (air+NH₃).Our results indicate that all examined process parameters positively influence the properties of PAW (air+NH₃). Among these parameters, the duration of NH₃ plasma treatment on PAW (air) ice exerts the most significant effect. Specifically, the concentration of NH₄⁺ ions increased by 134.2% when the NH₃ treatment time was extended from 0.5 hours to 1 hour, compared to 12.7% and 33.3% increases for NH₃ gas pressure (ranging from 0.25 to 0.55 mbar) and applied voltage (ranging from 500 to 700 V), respectively. Similarly, variations in pH, oxidation-reduction potential (ORP), and electrical conductivity were substantially higher with increased treatment time than with changes in gas pressure and applied voltage. The PAW (air+NH3) exhibited a neutral to slightly basic pH, making it ideal for soil applications, thereby addressing the existing issue of the high acidity of PAW and its use in agriculture.These findings highlight a promising green synthesis route for ammonium nitrate, providing an environmentally sustainable alternative to conventional production methods. This approach not only leverages plasma technology for chemical synthesis but also underscores its potential for developing sustainable industrial processes.

Boron carbide (B4C) ceramic has attracted fusion communities worldwide due to its high neutron shielding capabilities and other satisfactory thermal, chemical, physical, and mechanical properties. It is receiving wide attention for the ITER diagnostics ports for neutron shielding and for protecting maintenance personnel against radiation exposure. B4C ceramic blocks were developed using vacuum hot pressing of B4C powder at a process temperature of similar to 2100 degrees C and 30 MPa pressure by ITER-India through Indian Industry. Considering the need for reduced contamination, no sintering aid was used during the process. Inside the diagnostics port of Tokamak, B4C will be subjected to high radiation, ultrahigh vacuum, and high-temperature (HT) environments. Therefore, it is necessary to study temperature-dependent properties along with its other properties and vacuum compatibility. Toward the qualification of this vacuum hot-pressed B4C ceramic, its phase purity and surface microstructure were analyzed using X-ray diffraction (XRD) techniques and scanning electron microscopy (SEM). XRD data confirmed the presence of the B4C phase. Helium pycnometry was applied to determine the true density of the powder and hot-pressed B4C pellets, which were 2.55 and 2.52 g/cc, respectively. The thermal expansion is estimated to be 0.6% up to 1200 degrees C, with a mean coefficient of thermal expansion of 5.28 x 10(-6) K-1 between room temperature (RT) and 700 degrees C. Thermal expansion data were used to calculate temperature-dependent densities up to 1200 degrees C. The Differential scanning calorimetry sensor (DSC) measures phase stability up to 700 degrees C and calculates specific heat capacity. It was observed experimentally that the thermal conductivity drops by 45% between 50 degrees C and 500 degrees C. The experimental results are compared with the published data and are discussed in depth in this work.

This study introduces a green and sustainable method for synthesising ammonium nitrate (NH4NO3) using plasma activated water (PAW). Nitrate ions (NO3-) were generated via air plasma treatment, and ammonium ions (NH4+) were introduced using low pressure ammonia (NH3) plasma exposure to nitrate-rich PAW in frozen form to produce NH4NO3. Results demonstrated that process parameters, including NH3 gas pressure, applied voltage, and treatment time, significantly influenced PAW properties, with NH3 plasma treatment time showing the most substantial impact. Extending the treatment time from 0.5-1.5 hours increased NH4+ ion concentration by 134.2%, achieving a maximum of 168.2 mg L-(1) with an energy consumption of 74.8 mg NH4+ ions kWh-(1). The NO3- ion concentration reached 63.5 mg L-(1) with an energy yield of 222 mg NO3- ions kWh-(1). This method achieved a total yield of 27.6 mg NH(4)NO(3 )kWh-(1) and produced a neutral to slightly basic PAW suitable for agricultural applications, offering a promising alternative to traditional NH4NO3 production processes. [GRAPHICS]

Graphene and tungsten oxide (WO3) quantum dots (QDs) are known for their unique characteristics and their mixture has good potential for supercapacitor applications. To date, most of the reported processes for the synthesis of WO3 QDs are either expensive or require high capital investment and are performed at elevated temperatures. This study uses WO3 QDs produced by electrochemical oxidation of WC-6Co scrap at room temperature, followed by a microwave treatment resulting in the formation of partially dehydrated WO3·H0.5 QDs. The dehydration of WO3 QDs changed their crystal structure, reduced band gap, and increased vacancy concentrations which make them useful for energy storage applications. The primary objective of this study was to improve the supercapacitance performance of WO3 QDs by mixing them with electrochemically exfoliated graphene nanoplatelets. The graphene platelets were synthesized at room temperature via electrochemical exfoliation of graphite sheet at low voltage (3–4 V) using KOH solution as electrolyte of low concentration (0.05 M). These exfoliated graphene nanoplatelets had very low defect concentration. The synthesis of graphene was confirmed using transmission electron microscopy and Raman spectroscopy. The graphene-WO3 composite powder was prepared by manually mixing 1, 3, and 5 wt

This study explores a green pathway for urea synthesis using plasma-ice interaction with gas mixtures of N2 + CO2 and NH3 + CO2. Electrical and optical emission spectroscopy were employed to characterize the plasmas, revealing that urea formation involves complex reactions driven by high-energy species, producing reactive nitrogen and carbon intermediates that further react to form urea. Physicochemical analyses of plasma-treated ice showed increased pH, electrical conductivity (EC), and reduced oxidation-reduction potential (ORP). Optimization of plasma process parameters (gas pressure, applied voltage, and treatment time) was performed to enhance urea formation. Among these parameters, plasma treatment time had the most substantial influence. Increasing treatment time from 20 to 60 minutes significantly impacted physicochemical properties: for N2 + CO2 plasma, pH increased by 21.05%, EC by 184.7%, and ORP decreased by 27.48%; for NH3 + CO2 plasma, pH increased by 27.37%, EC by 239.05%, and ORP decreased by 72.67%, respectively. The study shows that NH3 + CO2 plasma produces a significantly higher concentration of urea (7.7 mg L-1) compared to N2 + CO2 plasma (0.55 mg L-1). This is attributed to the direct availability and reactivity of ammonia, which simplifies reaction pathways and enhances intermediate formation. These findings highlight the potential of plasma-ice interaction as an energy-efficient and environmentally friendly method for urea synthesis, offering a sustainable alternative to conventional processes.

The reported study involves the synthesis of high purity layered ternary carbide Ti3AlC2 MAX phase material by mixing the TiH2, Al and TiC powders in a planetary ball mill followed by two step pressureless sintering in flowing Argon (Ar) atmosphere. XRD and Raman analysis confirms the presence of Ti3AlC2 phase without im-purities of Al2O3 and TiC. The morphology studies using SEM confirms the lamellar structure of Ti3AlC2 and EDS measurements shows atomic percentage of Ti, Al and C are in compliance with the XRD phase analysis. X-ray Photoelectron spectroscopy investigations confirm the Ti-C bond. Core level XPS data of Al2p peak show a negative shift indicating electrostatic bonding of Al in Ti3AlC2. Ti2p and C1s core level spectra show the bonding of Mn+1Xn i.e TiC bond. TG-DSC results revealed approximately 7% increase in weight. Ti3AlC2 phase follows an endothermic pattern and does not undergo decomposition upto 1400 degrees C in vacuum environment. From XRD analysis at different temperatures, it was seen that Al2O3 and TiCx peaks started to form along with Ti3AlC2 at 1000 degrees C because of selective oxidation of Al into Al2O3. Thus, this study provides a beneficial approach to synthesis of high-purity Ti3AlC2 materials and understanding the thermal behaviour of Ti3AlC2 for high tem-perature applications.

Present work deals with the DBD plasma-induced surface modifications of aramid fabric for different exposure times and at atmospheric pressure using various characterization techniques such as XPS, ATR-FTIR spectroscopy and water contact angle measurements. Surface morphology using SEM reveals that, plasma treatment roughened the surface of the fabric. XPS results indicate that plasma treatment can successfully introduce polar functional groups onto the aramid fabric surface, improving its wettability and chemical reactivity. However, exceeding the optimal treatment time can result in the destruction of these functional groups and an increase in the C–C content, this can be attributed to the excessive etching of the surface and the destruction of the functional groups that were initially introduced during the plasma treatment. The ATR-FTIR spectra of plasma-treated aramid fabric show significant improvement in the intensities of CO and C–O stretching vibrations which relate to the wettability improvement. The results are discussed in the light of physical and chemical changes that occur due to DBD plasma treatment.

Plasma technologies for metallurgical applications are increasingly being adopted as they have the advantages of the unique properties of plasma. Amongst the major development priorities in many metallurgical operations and the development of new materials, plasma promises improved process control, direct utilization, improved environmental compliance and increased efficiency of energy. As a result, plasma is used for a wide spectrum of applications in materials processing like waste destruction, plasma spraying, plasma cutting, plasma welding, plasma synthesis of nanopowders, iron and steel making and extractive metallurgy for recovery of precious materials. Plasma has also recently been used as a source for the future fusion reactor, where it is confined by using the magnetic field inside the doughnut-shaped vacuum vessel. The fusion reactor which is being developed is seen as a promising, clean source of energy to solve the world's energy problem in the future as it does not use radioactive materials or pollute the air by carbon emissions. There are many challenging issues related to material constraints and plasma wall interactions which need attention as the operating environment of a fusion reactor imposes radiation damage effects. Detailed metallurgical investigation studies to select the most appropriate material are being done by many researchers. Moreover, the extremely harsh loading conditions in the fusion reactor can only be met with very diligent component design and careful selection of the best-suited material; fabricating and manufacturing techniques and efforts on developing new techniques are being carried out globally by many researchers. In this contributory article, a few examples of plasma-based technologies developed at Institute for Plasma Research (IPR) for industrial applications are described in brief. IPR has also developed, materials, technologies for blanket and fusion reactors, high temperature superconductors (HTS) for fusion magnets and they are elucidated in the below sections.

In this study, the impact of an air bubbler on the properties of plasma-activated water (PAW) was investigated in different configurations. A pencil plasma jet (PPJ) using a dielectric barrier discharge (DBD) was used to prepare PAW. In one configuration, the air bubbler was fitted at the tip of the pencil plasma jet, causing the discharge gases to emerge as bubbles in the water. In another configuration, the water was agitated using the bubbler during plasma-water interaction. The plasma generated in the PPJ setup was a filamentary DBD micro-discharge. However, water agitation using the bubbler changed this filamentary DBD to a diffusive DBD, which showed higher discharge current and lower electrode voltage compared to filamentary DBD. PAW produced using the fitted bubbler in the PPJ setup showed enhanced physicochemical properties, including NO2, NO3, dissolved O3, and non-traceable H2O2 compared to PAW produced without a bubbler. Additionally, PAW produced using water agitation by the bubbler showed a substantial increase in physicochemical properties and reactive species concentrations. The PAW process parameters such as air flow rate, plasma-water treatment time, and plasma discharge power showed monotonically increasing properties of PAW. The maximum concentrations of NO2, NO3, H2O2, and dissolved O3 (flow rate: 20 L/min, time: 5 min, power: 15 W) observed in this study were 0.334 g/L, 0.078 g/L, 0.045 g/L, and 0.016 g/L, respectively. This enhancement in the properties of PAW using a bubbler adds value to the current PAW technology in fields such as microbial inactivation, medicine, agriculture, and aquaculture, etc.

Electrochemical exfoliation of graphite is a promising technique for the synthesis of graphene at a commercial scale. Electrochemical synthesis of graphene at high voltage (similar to 10 V) is widely reported. However, at high voltage, multilayer graphene platelets with high defect concentration are produced. In this study, high quality graphene nanoplatelets consisting of 1-5 layers were produced at low voltage (3-4 V) using KOH solution as electrolyte. The effect of electrolyte stirring on the characteristics of graphene was studied. The stirring of electrolyte during electrolysis showed profound effect on the characteristics of graphene. The scanning electron microscopic (SEM) analysis showed that the stirring of electrolyte increased the average size of graphene nanoplatelets to 360 nm from 253 nm (without stirring). Raman spectroscopy indicated the presence of 1-5 layers of carbon atoms and the same was confirmed by transmission electron microscopy (TEM). A decrease in the defect concentration was noted with the increase in number of layers of carbon atoms in graphene produced with stirring.

To achieve higher efficiency in high-temperature environments, 9Cr-1Mo steels (also known as P91 steels) are promising candidates in power plants, petrochemical industries, heat exchangers, and nuclear applications. To enhance the performance against harsh environments, such as high-temperature oxidation and corrosion during operations, adding aluminum oxide (Al2O3)/iron aluminide (FeAl) coating through the aluminizing process has been found promising. Such coatings have been considered reliable for resistance to liquid-metal corrosion against flowing lead-lithium liquid breeders and against tritium permeation in blanket modules of fusion reactors. However, the welding process for aluminized coated steels is a challenge and is scarcely reported. The aluminum-rich coating at the top may alter the metallurgy of weld metal and subsequently the mechanical properties after welding. To investigate the same, preliminary bead-on-plate trials with a novel activated-tungsten inert gas welding process has been attempted for the first time. Bead-on-plate welding samples were prepared (with the same welding parameters) with five different fluxes, such as iron (III) oxide (Fe2O3), nickel (II) oxide (NiO), copper (II) oxide (CuO), cobalt tetroxide (Co3O4), and Al2O3, for aluminized coated 9Cr-1Mo steel. The resultant weld metal microstructure was evaluated using optical and electron microscopy, elemental analysis using energy-dispersive X-ray spectroscopy, phase analysis using X-ray diffraction, and Vickers hardness testing. It was observed that the presence of oxide-type fluxes results in arc constriction, which thereby affects the depth of penetration. The weld metal prepared with Fe2O3 flux demonstrates a superior depth-to-width ratio compared to other fluxes. An analysis for delta ferrite was also carried out and was observed to be present in Fe2O3 flux welds only. A detailed analysis of the weld metal under different activated fluxes is presented in the paper. The outcome of this work presents the feasibility of the welds of aluminized 9Cr steels as relevant for fusion reactor applications.

Diffusion in Solids: Key Topics in Materials Science and Engineering discusses the role of diffusion in coating, heat treating, and bonding processes. The book is organized into two sections, the first of which is a tutorial that covers the principles of diffusion, the factors that affect it, and some of the more common diffusion-driven processes in manufacturing. The section that follows furthers the learning process by guiding readers through a series of real-world problems and their respective solutions.

In the present work, we study the physicochemical changes that arise in water named plasma processed water (PPW) when it is exposed to the downstream low-pressure discharge of ammonia (NH3) gas. Optical emission spectroscopy and voltage-current characteristics of NH3 plasma are studied to identify species formed in NH3 plasma along with plasma characterization. A three-way full factorial design of experiment is performed to study the effect of process parameters named applied voltage, post-discharge gas-water interaction time, and NH3 gas pressure on physicochemical properties of PPW. The obtained results are analyzed using analysis of variance, standardized effect estimation, regression analysis, and response surfaces. The optimum values of these properties and PPW process parameters are estimated using MATLAB fmincon solver with experimental constraints. The emission spectrum of NH3 plasma showed strong intensity N2 + lines along with weak intensity N2, NH, and N+ lines. The obtained results showed the post-discharge gas-water interaction time and applied voltage had a significant impact on physicochemical properties and ammonium ions concentration in PPW. The obtained optimum value of voltage and time is 550 V and 15 min with given experimental constraints.

& nbsp;Aluminide coating on 9Cr steel is candidate coating for blanket module applications of fusion reactors. The welding fabrication processes associated with coated steels are still an issue as the presence of Al in weld metal has several detrimental outcomes. To address this, the authors have attempted a study on conventional TIG welding with V-groove to mitigate the effect of coating on weld metallurgy. This work emphasizes the com-parison of mechanical properties and microstructures of aluminide coated and uncoated/bare 9Cr-1Mo steel. Microstructural observations indicated presence of un-dissolved alumina inclusions at the weld fusion line. Despite such inclusions, the observed tensile strength of the weld joint for coated steel is 648 MPa +/- 16 MPa which is in line with the weld joint of un-coated steel (667 +/- 14 MPa) and substrate (643 MPa +/- 18 MPa). Impact toughness tests carried out at 0 C,-25 C and room temperature also indicate that there is no drastic effect of coating on weld joint and the observed toughness values are acceptable as per the reported data (45 J).

In this study, the high temperature cyclic oxidation behavior of thermal and plasma-treated aluminide coated Ti6Al4V alloy was investigated at 800 ? up to 360 h in 24 h cyclic exposures. The microstructural characteristics, phase analysis, morphological features, and microhardness of resultant oxidized samples were evaluated and compared with those of untreated Ti6Al4V alloy. The weight gain studies conducted from the cyclic oxidation tests revealed very minimal weight gain in plasma treated (PT) aluminide coated samples as compared to the thermal treated (TT) and uncoated (UC) samples. XRD results indicate that the UC samples oxidized at 800 ? exhibits the formation of a thick oxide layer consisting of only the rutile phase (TiO2). The TT and PT samples oxidized at 800 ? revealed presence of both alumina (Al2O3) and rutile (TiO2) phases. However, PT samples revealed stable alpha-Al2O3 phase whereas the TT samples showed metastable theta-Al(2)O(3 )phases in the oxide layer. The surface morphological features reveal that the oxide film formed on the surface of the PT samples had enough stability at 800 ? irrespective of the oxidation time. The PT samples exhibited higher hardness and improved oxidation resistance as compared to TT and UC samples. Increase in thermal stability, mechanical and oxidation properties of PT samples could be attributed to the formation of stable alumina (alpha-Al2O3) and presence of nanocrystalline aluminide phases (TiAl3 & TiAl2) in the diffusion layers during the oxidation tests. Therefore, a strong emphasis was placed on correlating the interfacial processes to the high temperature oxidation behavior.

The investigation of the oxidation resistance and tensile behavior of aluminide coated and uncoated Ti6Al4V at room temperature and at 600 degrees C was carried out. Ti-Al coating was developed on Ti6Al4V by Hot-dip Aluminizing technique followed by solution treatment (900 degrees C/1 h), quenching in water and ageing treatment (500 degrees C/6 h). For a comparative analysis, the diffusion heat treatment was performed with and without oxygen plasma environment. The diffusion treatment without oxygen plasma is referred as thermal treatment while the diffusion treatment with oxygen plasma is referred as plasma treatment. The cyclic oxidation test was carried out for uncoated samples, thermally treated (THT samples) and plasma treated samples (PAHT samples) at 600 degrees C for 120 h. Significant improvement in the oxidation resistance was observed for coated samples. Weight gain during oxidation studies in PAHT samples is almost 100 times less than uncoated samples and 8 times less than THT samples. The tensile test conducted at room temperature and at 600 degrees C showed marginal reduction of Ultimate tensile strength (UTS) and Yield strength (YS) of substrate for PAHT samples and THT samples. Plasma processing yields nanocrystalline coatings which have been found to improve oxidation resistance and would help address oxidation issues in gas turbine applications.

Plasma assisted aluminide coating was formed on Ti6Al4V alloy by hot-dip aluminizing (HDA) followed by two-step diffusion heat treatment. The HDA coated Ti6Al4V alloys were subjected to solution annealing (900 °C/1 h) and aging heat treatment (500 °C/6 h) by plasma processing route and compared with thermal treatment. The resultant coated and heat-treated samples were characterized using SEM for surface morphology and microstructure analysis, EDS for elemental analysis and x-ray diffraction (XRD) for phase analysis. From the characterization, it was observed that after the diffusion heat treatments, the microstructure of aluminized coating consisted of an outer layer of Al2O3 followed by TiAl3, TiAl2, Ti-Al, and Ti3Al phases. In the diffusion zone, hardness variation in the range of 366–490 HV0.05 and 342–525 HV0.05 was observed in case of thermal and plasma-treated samples respectively. However, in the diffusion zone, the microhardness of plasma-treated samples was slightly higher than the thermally treated samples. The plasma ion bombardment appears to alter the crystalline size due to vacancy concentration which leads to increment in the hardness value. The details of experiments, characterization along with the interpretations and comparison of various microstructural aspects have been presented in this manuscript.

Aluminide coatings with a top alumina layer on 9Cr steels are considered candidates for fusion blanket applications. One of the critical issues associated with such coating is the fabrication sequence. It is therefore important to investigate the effect of aluminide coating on weld properties of 9Cr steels. This work is a preliminary investigation of the weldability of aluminide coated 9Cr-1Mo steels using bead-on-plate welding experiments. Alumina coated GRADE 91 steel samples by hot dip aluminizing followed by normalizing and plasma tempering were generated. Bead-on-plate welding studies were conducted at different heat inputs by varying the weld speed (100,125,150 mm/min) and using a constant current of 200A by autogenous tungsten inert gas (TIG) welding process. The effect of coating on the weld microstructure was investigated using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive x-rays (SEM-EDX) and microhardness tests. It was observed that the presence of alumina (Al2O3) on the top of coated samples resulted in improved depth of penetration (DOP) due to arc constriction. The presence of Al rich inclusions (AlN) in the weld bead were also observed. The marginal increase in Al concentration of the weld bead appears to reduce the grain size of weld metal for coated sample and microhardness was enhanced compared to the uncoated 9Cr-1Mo steels.