Thermal Route Research Articles

Impact of surface-roughness and fractality on electrical conductivity of SnS thin films

Mono- and multi-fractal geometry have been used to explore the surface characteristics of scanning electron microscopy (SEM) micrographs of the SnS films with thicknesses of 100nm (SnS1) to 600nm (SnS4), respectively. For this investigation, the SnS thin films have been grown on fluorine-doped tin oxide (FTO)-coated glass substrate through the thermal evaporation route, and surface morphologies are captured by SEM. Two-dimensional multi-fractal detrended fluctuation analysis (MFDFA) based on the partition function is used to examine whether the surfaces have a multi-fractal nature or not. The partition function is applied to extract the generalized Hurst exponent from the segment size. It has been found that surfaces with higher surface roughness induce substantial nonlinearity and a wider width of the multi-fractal spectrum. The multi-fractal spectrum acquired from the analysis of the geometry and shape of the singularity spectrum is used to quantify the irregularity and complexity of surfaces. Minkowski functionals (MFs) parameters such as volume, boundary, and connectivity were measured for each thin film. Moreover, we tried to correlate the electrical conductivity with the mono- and multi-fractal parameters such as fractal dimension (Df), singularity strength function (Δα), singularity spectrum Δf(α), and it is observed that the conductivity of a thin film decreases with decreasing fractal dimension. The minimum (maximum) resistivity (conductivity) was observed for the surface having a larger fractal dimension. The present investigation suggests that such SnS surfaces, having minimal resistivity and maximum conductivity on the roughest surface, indicate enhanced light trapping capacity and can be utilized as active layers for advanced optoelectronics devices.

Construction of Ru/MnO–Mn7C3/N-doped carbon sheets for boosting electrocatalytic hydrogen generation

Suffering from their low conductivity, Mn-base oxides are commonly inactive in H–OH activation. Generally, tailoring the coordinate environment of materials could induce variation in the atomic arrangement and further influence their chemical activity. Herein, we propose a feasible strategy to mediate the electronic structure of Mn-based oxides by facile hydrothermal method and thermal reduction route. Compared with MnO2 sheets, the as-synthesized Ru/MnO–Mn7C3/N-doped carbon sheets (Ru/MnO–Mn7C3/NC) exhibit the higher activity for both acidic (73 mV) and alkaline water reduction reaction (44 mV@10 mA/cm2). Benefitting from unique structures, Ru/MnO–Mn7C3/NC sheets show the better freshwater/seawater oxidation reactivity, exceeding RuO2. The strong interaction of MnO–Mn7C3 heterostructures, Ru, and N-doped carbon endows Ru/MnO–Mn7C3/NC with the good freshwater and seawater dissociation performance, outperforming most of the reported Mn-based oxides.

Comparative assessment of global warming potential of gasoline, battery, and hybrid vehicles in India

This study reports a comparative analysis of life cycle greenhouse gas (GHG, CO2-eq.) emissions of three fuel-type vehicles, viz. internal combustion engine (ICEVs), battery electric (BEVs), and hybrid electric vehicles (HEVs), from an Indian perspective. Vehicles in hatchback and compact sports utility vehicles (SUVs) categories were analyzed. GHG emissions in fuel life cycle (well-to-tank and tank-to-wheel) and vehicle life cycle were estimated using data from websites of OEMs and ministries of Government of India, and the GREET software. The vehicle life cycle constitutes a smaller fraction (15–20 %) of total life cycle GHG emissions for ICEVs and HEVs compared to BEVs (∼35 %). The vehicle cycle emissions of BEVs are higher than ICEV and HEV in both categories (52–63 % for hatchback and approx. 45 % for compact SUV). The fuel cycle emissions of BEVs are smaller than ICEV and HEV in both categories (29–34 % for hatchback and 32–40 % for compact SUV). The total life cycle GHG emissions of BEVs were lower than ICEV and HEV (15–17 % in hatchback and 17–25 % in compact SUV category) for the 2023 energy mix in India with a significant share of thermal route. With anticipated doubling of renewable energy sources in India by 2030, the total life cycle GHG emission of BEV will decrease by approximately 20 %. However, sensitivity analysis revealed that BEVs produce higher GHG emissions than ICEVs and HEVs until a minimum lifetime travel distance. Thermal power plant efficiency and battery lifespan also influence BEVs lifetime GHG emissions.

Facile Carbothermal Synthesis of Metal Phosphides-Based Multifunctional Electrocatalysts via Polyaniline Doped with Phosphoric Acid

Transition metal phosphides (TMPs) and their composites are promising non-platinum electrocatalysts for hydrogen evolution (HER), oxygen evolution (OER), and oxygen reduction (ORR) reactions. But traditional methods to obtain these electrocatalysts are usually multi-step and include the participation of hazardous phosphorus compounds during phosphidation. Here, the possibility of using a polyaniline doped with phosphoric acid (PANI∙H3PO4)—as a source of C, N and P simultaneously - to obtain composites based on N,P-doped carbon and nano- and/or submicron TMP particles as HER, OER and ORR electrocatalysts is demonstrated. The pyrolysis of PANI∙H3PO4 together with Co, Ni, Mo, or Fe salt allows the formation of such composite electrocatalysts by the carbon thermal reduction route. Regardless of the pH of the electrolyte, the MoP-based electrocatalyst is characterized in HER by the smallest Tafel slope and overpotential of hydrogen evolution and also exhibits high stability during long-term operation. At the same time, other composites are multifunctional electrocatalysts possessing activity not only in HER, but also in OER and ORR. The proposed approach can be a starting point for a simple, universal in choice of d-metal, and environmentally attractive preparation of multifunctional TMP-based electrocatalysts with further improvement of their performance.

Harnessing bright upconversion luminescence from PEG-coated NaGdF4:Ho3+/Yb3+ nanoparticles for contrast enhancement in dual mode OCT imaging and optical temperature sensing

In this work, authors synthesized the Polyethylene Glycol (PEG) coated NaGdF4:Ho3+/Yb3+ nanoparticles using the thermal decomposition reaction route. Our primary objective was to comprehensively evaluate their suitability for augmenting image contrast, particularly within the intricate domain of Swept Source Optical Coherence Tomography (SSOCT) and photo-thermal Optical Coherence Tomography (PTOCT) imaging modalities. Our meticulous inquiry yielded the revelation of extraordinary upconversion emissions, which emanated from the distinct transitions of Ho3+ ions, most notably the 5F4(5S2)→ 5I8 and 5F5→ 5I8 transitions. These transitions manifested as strikingly vibrant green emissions, precisely at the 539 nm and 661 nm wavelengths. Furthermore, we investigated the underlying upconversion mechanism, delving deeply into the elucidation of decay times and the nanoparticles' ability to transform incident radiation into thermal energy. Impressively, these nanoparticles exhibited a noteworthy photo-thermal conversion efficiency, specifically measured at an impressive 47.4 % along with the bright green luminescence. Our study also extended to bio-compatibility, where we achieved highly encouraging outcomes. Following 24 h of incubation with HeLa cells treated with UCNP-PEG, we ascertained a compelling cell survival rate exceeding 80 %, underscoring the favorable biocompatibility of these nanoparticles. Moreover, these nanoparticles demonstrated a conspicuous thermal sensitivity, quantified at 5.1 × 10−3 K−1 at 380K, thus signaling their potential for precision temperature monitoring and could be applied at the cellular level.

Liquid crystalline polyurethane/POSS hybrid nanocomposites pyrolysis studies by Py-GC/MS and TG/FTIR techniques

The process of pyrolysis of liquid crystalline polyurethane (LCPU) composites with polyhedral oligomeric silsesquioxanes (POSS) has been studied using pyrolysis - gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetry/Fourier transform infrared spectroscopy (TG/FTIR) coupled thermoanalytical techniques. LCPU elastomers modified with POSS molecules with different architectures, bearing aromatic, isobutyl and cycloaliphatic moieties, yield various volatile products of pyrolysis that were collected and characterized. The TG study showed significant differences in the thermal behavior of composites studied, evidencing the influence of the silsesquioxane type on the polyurethane pyrolysis paths. FTIR study of volatile products of thermal decomposition showed the presence of characteristic bands originated from carbonyl, amine, ether, methylene, and unsaturated hydrocarbon linkages. GC/MS investigation confirmed the existence of compounds identified by the IR method. The application of both thermoanalytical methods made it possible to postulate the thermal decomposition routes of PU/POSS hybrids and to point out the main factors responsible for changes in the thermal stability.

Thermal degradation of non-isocyanate polyurethanes

Non-isocyanate polyurethanes (NIPUs) are considered as a class of environmentally-safe polymers that show promising properties, such as chemical and mechanical resistance. An important feature that may limit some important applications is the thermal degradation behavior of NIPUs and their composites and hybrids. Hence, this article comprehensively reviews recent developments in these materials groups, focusing on the thermal stability and degradation routes. Influence of urethane linkage vicinity, molar mass and ratio of carbonate and amine components, and chemical structure on NIPU thermal degradation behavior was discussed. The onset temperature of degradation was found to be mainly influenced by urethane bonds concentration and crosslinking density of NIPU material. Chain length of amine component has also a significant impact on the thermal degradation profile. The incorporation of bio-sourced and nano-scaled additives (carbon- and silica-based nanoparticles) and their impact on thermal stability of NIPU matrix was analyzed, too, and future outlooks were given.

Regional heterogeneity of sustainable wastewater sludge management in China

In various regions of China, the sludge characteristics, available sludge treatment and disposal routes, and economic and environmental concerns exhibit significant variations. This makes it challenging for regions to select appropriate technologies for sustainable sludge management. This study proposed a universal framework that integrates carbon emissions, economic cost, and environmental risk potential to assess sustainability of diverse sludge treatment and disposal routes in different regions of China. An up-to-date database of sludge characteristics in different regions of China has also been created. Depending on sludge characteristics, co-incineration in coal-fired plants or cement kilns and thermal hydrolysis-anaerobic digestion routes demonstrate outstanding sustainability for most regions in China. Moreover, the current carbon trading price in China is low and does not significantly influence the technical selection. The created sludge characteristics database and the sustainability assessment framework could help sludge managers make better in process selection, technological improvement, and future policy formulation.

Photothermal catalytic CO2 oxidative dehydrogenation of propane over a dual functional Pt-GaN/SrTiO3 catalyst

Photothermal CO2 oxidative dehydrogenation of propane (CO2-ODHP) is an environmentally friendly and sustainable route for propylene production and CO2 utilization. In the present work, we developed a Pt-GaN/SrTiO3 dual-functional catalyst to facilitate the reaction. The catalyst achieved propylene and CO yields of 1 mmol·gcat-1·h-1 and 1.2 mmol·gcat-1·h-1 under photothermal conditions at 320 °C, surpassing the performance of previously reported catalysts. Additionally, control experiments and in situ DRIFTS analyses corroborated that GaN and Pt were primarily responsible for the activation of C-H and CO bonds, respectively, and the photothermal route worked via a distinguished intermediate for CO2 activation in contrast to the thermal route. DFT calculations supported the reaction route involving the coupling direct dehydrogenation of propane and reverse water-gas shift reaction. The present work shines a light on the design of photothermal catalysts with dual functions, particularly for the activation of CO2 and light hydrocarbons. Additionally, it proposes a strategy to initiate high-temperature reactions at relatively lower temperatures.

Thermal plasma synthesized Mn3O4 nanoparticles as T1 and T2 MRI contrast agents

In Magnetic Resonance Imaging (MRI), manganese oxides are predominantly used as contrast agents (CAs) to enhance contrast of T1–weighted acquisitions. In this work, Mn3O4 nanomaterials were synthesized by high temperature thermal plasma route and thoroughly characterized by structural, microscopic and biocompatibility investigations. The nanoparticles so obtained display both T1 and T2 MRI contrast properties. This was attributed to the fact that the nanomaterials synthesized by thermal plasma route possess higher saturation magnetization than those synthesized by various chemical methods. The presence of oxygen vacancies and relatively large size of the synthesized nanoparticles can also be regarded as other two reasons behind attainment of T1-T2 dual contrast. Thermal plasma synthesized nanomaterials have never been earlier demonstrated as MRI CAs. Moreover, this is the first report presenting detailed characterization of the thermal plasma synthesized Mn3O4. The microstructure of the synthesized Mn3O4 nanoparticles was observed to be spherical in shape. The biocompatibility of the developed nanosystem was established by cell viability analysis. Finally, the efficiency of the agent for T1–T2 contrast enhancement was confirmed through MRI experiments. This work lays the foundation of research on a new class of MRI CAs synthesized by thermal plasma.

Antibiotic Chloramphenicol degradation using submerged thermal plasma synergized with LaMnO3 catalyst

The present study focused on the degradation of antibiotic Chloramphenicol (CAP), an emerging contaminant, using submerged thermal plasma (STP) technology. Almost 99 % degradation and 82 % mineralization were achieved within 20 min of treatment by Ar/CO2 plasma, generated at 6.2 kW discharge power using a customized thermal plasma torch inside the aqueous solution. Kinetic analysis revealed first-order reaction for CAP degradation with a rate constant of 0.257 min−1. Long-lived species, such as H2O2, O3, NO2–, NO3–, and Cl- formed during plasma treatment were quantified. LaMnO3 perovskite (LMO) nanopowder prepared through a novel thermal plasma route, was introduced as catalyst into the treatment system which enhanced the degradation and mineralization efficiency by 34 % and 17 %, respectively, showing a strong synergetic effect between STP and catalyst. The energy yield was elevated from 102 mg/kWh to 144 mg/kWh with the addition of catalyst into the STP treatment system. Liquid chromatography-mass spectroscopy was used to identify the various degradation intermediates produced during thermal plasma treatment and correspondingly possible degradation pathways were proposed. The antibacterial activity assessment results revealed a significant reduction in the antimicrobial activity of all treated solutions against Gram-positive Bacillus cereus and Gram-negative Pseudomonas aeruginosa bacteria. Additionally, seed germination and growth assessment revealed a reduction in phytotoxicity of the treated solutions. STP, combined with the LMO, proved highly effective in treating pharmaceutical contamination in aqueous medium.

Electrochemical charge storage performance of (Mn, Ni, Mo, Co, Fe)3O4 high entropy oxide nanoparticles produced via thermal plasma route

Highly complex high entropy metal oxides (HEOs) have several unique characteristics, such as more active sites and material stability that improve the electrochemical charge storage capacity. In this study, HEOs (Mn, Ni, Mo, Co, Fe)3O4 nanoparticles were synthesized using a thermal plasma route and its electrochemical energy storage performance was studied with two distinct electrolytes such as 1 M KOH and NaOH. The X-ray diffraction analysis revealed the phase pure spinel structured HEOs with crystalline size ranging from 13 to 29 nm. Scanning electron microscopy and electron dispersive X-ray spectroscopy results revealed the quasi-spherical morphology and uniform distribution of constitutional cations in the as-synthesized HEOs. The X-ray photoelectron spectroscopy results identified the oxidation states of cations in spinel HEOs. The charge/discharge studies of as-synthesized HEOs showed a specific capacitance of 215 F g-1 /26.9 mAh g-1 at a current density of 2 A g-1 in 1 M KOH electrolyte which is 156 % greater than 1 M NaOH electrolyte. Furthermore, a high capacitance retention of 91 % was achieved after completing 3000 cycles at 10 A g-1 current density which indicates that the HEOs have excellent charge/discharge reversibility. Electrochemical impedance spectroscopy revealed that the solution and charge transfer resistances of HEOs electrodes were 1.04 and 3.2 Ω, respectively. This novel synthesis strategy attempts to overcome the difficulties experienced by established methods for bulk manufacture of phase pure HEOs since thermal plasma method is a rapid and a single-step approach for the bulk production of nanomaterial.

Metal-urea complexes as primary precursors to generate VO2, ZrO2, NbO2, TaO2, Ga2O3 and TeO2 oxides in the nanoscale range by thermal decomposition route

Six metal chlorides of vanadium, zirconium, niobium, tantalum, gallium, and tellurium (i.e., VCl3, ZrOCl2×8H2O, NbCl5, TaCl5, GaCl3, and TeCl4) were reacted with urea (referred to as U) in aqueous media at ~ 50 oC. The resulting metal-urea complexes were characterized using CHN elemental analyses, infrared (IR) spectroscopy, and thermogravimetry. After the synthesized metal-urea complexes were characterized, their ability to form stable metal oxides was examined. The vanadium(IV) oxide; VO2, zirconium(IV) oxide; ZrO2, niobium(IV) oxide, NbO2, tantalum(IV) oxide; TaO2, gallium(III) oxide; Ga2O3, and tellurium(IV) oxide; TeO2, were generated by the thermal decomposition route of the synthesized metal-urea complexes at low temperature 600 °C in static air atmosphere. The transmission electron microscopy (TEM) revealed that the oxides contain uniform spherical nanoparticles. KEY WORDS: Metal chloride, Metal-urea complex, Urea, FTIR, TEM Bull. Chem. Soc. Ethiop. 2024, 38(4), 1003-1012. DOI: https://dx.doi.org/10.4314/bcse.v38i4.15

Ultra-Broadband Plasmon Resonance in Gold Nanoparticles Precipitated in ZnO-Al2O3-SiO2 Glass

Optical materials with a tunable localized surface plasmon resonance (LSPR) are of great interest for applications in photonics and optoelectronics. In the present study, we explored the potential of generating an LSPR band with an ultra-broad range of over 1000 nm in gold nanoparticles (NPs), precipitated through a thermal treatment in ZnO-Al2O3-SiO2 glass. Using optical absorption spectroscopy, we demonstrated that the LSPR band’s position and shape can be finely controlled by varying the thermal treatment route. Comprehensive methods including Raman spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy were used to study the glass structure, while computational approaches were used for the theoretical description of the absorption spectra. The obtained results allowed us to suggest a scenario responsible for an abnormal LSPR band broadening that includes a possible interparticle plasmonic coupling effect taking place during the liquid–liquid phase separation of the heat-treated glass. The formation of gold NPs with an ultra-broad LSPR band in glasses holds promise for sensitizing rare earth ion luminescence for new photonics devices.

Production of sustainable methanol from aquatic biomass via thermal conversion route

Energy security is considered a basic need for the community. The development of a non-competing energy source is necessary to maintain harmony when fulfilling energy and food needs. Aquatic biomass such as algae is a promising sustainable energy source as it can be cultivated in the sea or pond which does not require productive land. By using thermal reaction, algae can be converted into methanol via gasification followed by hydrogenation reactions. The key challenge of algae utilization lies in the high moisture content. This work presents an understanding of the role of moisture on the algae for methanol production. Although moisture content has a negative impact on the syngas quality, the methanol production does not change with increasing moisture content. Under the optimum condition, the algae-to-methanol route converts ∼45% of the total energy input into energy in the form of methanol. The production of one-ton methanol from algae with 10 wt% moisture requires algae (2.7 ton), oxygen (0.9 ton), boiler feed water (1.5 ton), thermal energy (12.1 GJ) and electricity (0.7 MWh). The present work provides a clear understanding of the potential of aquatic biomass for methanol production, leading to further development to achieve a feasible algae-to-methanol route.

The coupling influence of chemical/physical effects of NH3 on the NO formation in the premixed CH4–NH3 flames

The individual and coupling chemical/physical effects of NH3 addition on the NO formation of the CH4 premixed combustion process are investigated using the numerical simulation and the detailed chemical mechanism. The roles of chemical and physical effects of NH3 component in NO formation routes and major NO-related reactions of CH4–NH3 premixed flames are identified at different equivalence ratios (φ) and blending ratios (ηNH3). The results show that, with the increased NH3 addition, the continuously increased peak NO concentration at the fuel-lean condition is predominated by the chemical effects of NH3, while the variation of peak NO concentration at the fuel-rich condition can be ascribed to both chemical and physical effects of NH3. Additionally, for the pure CH4 fuel or the CH4/NH3 blends with the low NH3 addition, the NO/NO2 conversion process is always significant to the NO concentration variations at φ = 0.8. Furthermore, with the NH3 addition, the enhanced importance of the NO/NO2 conversion and the HNO route to the NO formation are attributed to the physical and chemical effects respectively at φ = 0.8. By contrast, with the NH3 addition at φ = 1.2, the NO formation is predominated by the HNO route, the thermal route and the NNH route, while their contribution variations are all dominated by chemical effects of NH3. Specifically, the HNO route becomes increasingly significant to the NO production, while the thermal route and the NNH route play the more paramount roles in the NO consumption in the CH4–NH3 flame at φ = 1.2. Besides, with the increased NH3 addition up to the medium level, the considerably decreased contribution of the thermal NO pathway is mainly attributed to physical effects of NH3, while the improved HNO pathway is undoubtedly dominated by chemical effects. Furthermore, the NO/NO2 conversion process always plays a significant role in the NO formation with the increased NH3 addition, and its contribution is increased initially due to physical effects but decreased subsequently thanks to chemical effects. In addition, it is also confirmed that the NO destruction can be accelerated by the increased NHi radicals with the NH3 addition, while the C–N kinetics could be important to the NO formations in the CH4–NH3 flame considering the certain contribution of CH3+HNONO + CH4 to the NO production.

Photocatalytic degradation of methyl orange using CuO/Al2O3 nanocomposite obtained by microwave-assisted thermal decomposition route

Aluminum oxide (Al2O3) and copper oxide (CuO) are known to exhibit very exceptional properties including high thermal and chemical properties that promise a wide area of applications. In this paper, we report the microwave-assisted thermal decomposition route to CuO/Al2O3 nanocomposite and its application as a photocatalyst for methyl orange (MO) degradation. Al2O3 was first prepared at different temperatures of 900, 1000, and 1100 °C, denoted as Al2O3(1), Al2O3(2), and Al2O3(3). Subsequently, the best temperature (1000 °C) was selected for the synthesis of CuO/Al2O3 nanocomposite. XRD analysis confirmed the hexagonal crystal structure for all the Al2O3 and the monoclinic phase for the CuO within the composite. The crystallite sizes of the alumina increased with temperature and a similar growth pattern occurred in the entire samples. Scanning electron microscopy and transmission electron microscopy (SEM and TEM) show clear spherical morphology for all the samples with obvious agglomeration as temperature increases. Optical characterization displayed decreasing band gap energies with increasing temperature, implying size increase due to particle interaction, boundary energy reduction, and grain boundary migration. The photocatalytic performance of the CuO/Al2O3 under visible light was evaluated on methyl orange (MO), and the degradation was studied with some process parameters such as the effect of catalysts dosage and initial concentration of MO. Results showed that the CuO/Al2O3 exhibited about 94.2 % efficiency within 3 h using an optimum dose of 2.0 g/L and an initial MO concentration of 20 mg/L. However, the use of CuO/Al2O3 nanocomposites to remove other organic pollutants could confirm the robustness of this catalyst.

Simultaneous impacts of H2 and CO2 transport on NO formations of premixed and diffusion opposed flames fueled by biogas-H2 blends

With the numerical simulation, the transport impacts of H2 and CO2 on the NO formations of premixed and diffusion opposed biogas-H2 flames were isolated quantitatively by using the fictious species method. The combined and individual impacts of H2 and CO2 transport on the NO concentrations, radical pools and critical reactions were compared and investigated comprehensively. The results show that the NO concentration of diffusion flame can be increased steadily with either H2 or CO2 transport, while the NO concentration of the premixed flame can be increased and decreased at fuel-lean and fuel-rich conditions respectively owing to the dominant role of H2 transport in the coupling transport influence. The CO2 transport is confirmed to have the effective influence on the NO formations in the fast reaction zones of the premixed flames based on the convection-diffusion-reaction (CDR) budget analysis, but its effects on the NO concentration are weakened effectively owing to that the NO production in the post-flame zone plays a more dominant role in the NO concentration of the premixed flame. Additionally, the H2 and CO2 transport have the opposite impacts on the major NO production/destruction reactions in the premixed flame but they exert negative or positive effects simultaneously in the diffusion flame. In either premixed or diffusion flame, the H2 and CO2 transport can influence the NO production primarily by affecting the NO/NO2 conversion rate, the thermal route (N + OHNO + H) and the NNH intermediate route (HNO + HH2+NO). Particularly, unlike the CO2 transport effects on the thermochemistry identified in our previous studies, the CO2 transport is found to be relatively insignificant to the NO generation of the premixed biogas-H2 flame. Meanwhile, for the NO production in the diffusion biogas-H2 flame, the CO2 transport effects could account for around 25% of total transport effects of H2 and CO2, suggesting that the CO2 transport should be not neglected when investigating the NO production in the diffusion biogas-H2 flame.

Thermal plasma processing of technologically important materials

Thermal plasma is one of the upcoming powerful tools used for materials processing. It covers a wide range of technological applications such as synthesis of various refractory ceramic materials, metals and alloys, deposition of coatings, high temperature processing of materials as well as disintegration of waste materials. Representative technologically important material systems viz rare earth hexaboride (e.g. GdB6) and carbonaceous materials are focus of the present manuscript. Both the material systems have been processed using DC thermal plasma route and characterized thoroughly for structural, morphological, surface properties using XRD, TEM, XPS respectively. Morphology of GdB6 has been tailored by varying plasma parameters during synthesis. Further, these GdB6 powder were investigated for electron emission performance using Field Electron Emission and maximum current density of 0.5 mA/cm2 was noted for the nanocrystalline GdB6 sample. Feasibility of thermal plasmas for production of nanocrystalline GdB6 and processing of a bio-waste to obtain technologically important carbonaceous materials has also been explored.

Characterization and electrochemical properties of TiO2-rNTs/SnO2–Sb/PbO2 electrodes for the mineralization of persistent organic pollutants using anodic oxidation coupled Electro-Fenton treatment: Effect of precursor selection

The present study compares the effect of using different solvents on the electrochemical properties of the reduced TiO2 nanotubes (TiO2-rNTs) layered Ti/TiO2-rNTs/SnO2–Sb/PbO2 anodes. The electrodes are prepared using three different solvent-based precursors: (i) isopropanol, (ii) ethylene glycol and citric acid (Pechini method), and (iii) 2-hydroxyethylammonium acetate (2HEAA) ionic liquid (IL) via the thermal decomposition route. The decomposition mechanism of precursor solutions was explored using the thermogravimetric (TGA) analysis. Further, the physicochemical properties of the electrodes are examined using Field emission Scanning Electron microscopy (FE-SEM), X-ray diffraction spectroscopy (XRD), and X-ray photoelectron emission spectroscopy (XPS). The results revealed that solvents with higher viscosity and slower decomposition rates support better film uniformity and higher stability of the electrode. The TiO2 -rNTs bottom layer and PbO2 top layer helped obtain higher film stability, increased working potential window (2.2 V vs. SHE) of the electrode, and the repeatability of the results. The performance of different electrodes based on the precursor solution is found as IL ≫ Pechini > Isopropanol. 4-chlorophenol (4-CP) is used as a model pollutant to test the performance of IL-Ti/TiO2-rNTs/SnO2–Sb/PbO2 anode in an anodic oxidation (AO) coupled electro-Fenton (EF) treatment. Further, the reliability of the electrode is evaluated by mineralizing other persistent organic pollutants (POPs) like tetracyclin, phenol, 2-chlorophenol (2-CP), and 2,4-dichlorophenol (2,4-DCP). Under the optimized conditions, the proposed system was able to mineralize the tetracyclin, phenol, 2-CP, 2,4-DCP, and 4-CP up to 78.91, 82.07, 74.96, 78.78, and 69.3 %, respectively. Moreover, the degradation mechanism of chlorophenols is proposed.