Thermogravimetry-differential Thermal Analysis Research Articles

Structural properties and photocatalytic activity of amorphous-crystalline TiO2 thin films

TiO2-coated glass plates were prepared by dip coating using TiO2 coating sol with a mixed amorphous and crystalline structure. These samples were dried at 100°C or calcined at 500°C, which were referred to as MT and CT, respectively. The TiO2 thin films on glass plates were characterized by X-ray diffraction, thermogravimetry-differential thermal analysis, X-ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy, Brunauer-Emmett-Teller surface area measurement, scanning electron microscopy, and ultraviolet–visible diffuse reflectance spectra. The TiO2 thin films of MT samples had mixed amorphous and crystalline structures, while those of CT samples had only crystalline structures. The photocatalytic activity of the samples was investigated on the basis of methylene blue (MB) decomposition under ultraviolet and visible light irradiation. In the dark stabilization, MT samples had a higher MB adsorption capacity than CT samples. MT samples had a smaller amount of anatase TiO2 than CT samples, but both glass plate samples showed the same MB photocatalytic activity under ultraviolet light irradiation. We presumed that these results were because the amorphous-crystalline TiO2 thin films had a high specific surface area, so they had more adsorption and active sites. Under visible light irradiation, only the MT samples had photocatalytic activity, which can be attributed to their high visible light absorbance, which may be due to their peroxo groups, disordered structure, and larger specific surface area.

Synthesis, characterization, sorption, and antibacterial properties of a new polystyrene-supported o-hydroxyacetophenonediethylenetriamine polymer

A new polystyrene-supported Schiff base resin, o-hydroxyacetophenonediethylenetriamine-polystyrene (PS-HAPDA), has been synthesized via a reaction between the commercially available chloromethyl polystyrene polymer and the Schiff base o-hydroxyacetophenonediethylenetriamine (HAPDA). The structure of the synthesized polymer has been determined by Fourier transform infrared spectroscopy and thermogravimetry differential thermal analysis (TG/DTA). The chelating properties of the new polymer toward some divalent metal ions were studied by a batch equilibration technique under different experimental conditions. Results revealed that the metal-ion uptake follows the order Cu+2 > Zn+2 > Ni+2 > Co+2 > Pb+2. The antibacterial activity of complexed PS-HAPDA was tested against Gram-negative strains and Gram-positive strains.

Selection and thermophysical assessment of phase change materials (PCMs) for space cooling applications in buildings

Phase change materials are gaining more attention in building comfort applications because of their latent heat thermal energy storage (TES) capacity. Identifying the best PCM candidate is a pivotal factor that significantly impacts the thermal performance of a building. This study delves into assessing prospective PCM candidates for potential utilization in cooling systems within buildings in hot subtropical climates. Extending the application of multicriteria decision-making (MCDM) methodologies, this research scrutinizes various commercial PCMs by conducting an exhaustive analysis of pertinent literature in the context of this specific application objective. Thermophysical properties are integrated into the MCDM framework to identify the most fitting candidates with optimal properties and attributes. The properties and attributes of PCMs are subjected to scoring and weighting through the AHP based on their significance in the given application context. TOPSIS and VIKOR techniques select the suitable PCM from the identified PCMs. The results showed that latent heat receives the highest weightage, amounting to 50.2%, due to its paramount importance. Furthermore, OM37 emerged as a promising choice for building space cooling, considering the prescreened temperature range of 30 °C–40 °C and for the specific location under consideration. Following PCM selection, thorough characterization was performed to evaluate the suitability of the chosen PCM for integration within building envelopes. The thermal conductivity of OM37 was determined to be 0.20 W/mK, while the morphology by a Field Emission Scanning Electron Microscope (Fe-SEM) intricate porous structure. Furthermore, a differential scanning calorimeter (DSC) suggests melting and solidification temperatures of 40 °C and 34 °C with a total enthalpy of 197.04 j/g, and a Thermogravimetry Differential Thermal Analysis (TG/DTA) showed a substantial weight loss of approximately 98.9% at around 247.3 °C. The presented experimental test results agree with the literature data and other researchers’ results.

Effect of Na versus Ca Sulfate Salts on the Hydration of Calcium Sulfoaluminate Clinker.

This paper examined how the amount (5% or 20%) and type (CaSO4 or Na2SO4) of sulphate salt affect the hydration of calcium sulphoaluminate clinker (KCSA). The mechanical behavior of the pastes was determined at 1, 3, 28, and 90 days, the heat flow and total heat were measured with isothermal conduction calorimetry, and the reaction products were characterized using X-ray diffraction (XRD), differential thermal analysis/thermogravimetry (DTA/TG) and scanning electron microscopy (SEM). The results obtained indicated that both the amount of sulphate salt (5% or 20%) and its type (CaSO4 or Na2SO4) affect the hydration kinetics, type of reaction products formed, and development of mechanical strength. The incorporation of CaSO4 has a positive effect on the development of the mechanical strength of KCSA. However, Na2SO4 can also produce adverse side effects at older ages. The presence of Na2SO4 increases pH values, which partly destabilizes the ettringite formed, thereby favoring carbonation and thenardite precipitation, which can cause the specimens to crack and break.

Integrated experimental assessment and validation of oxidation with real-scale SiC fuel compact in HTGR

Air ingress is a critical accident in HTGR design, caused by a rupture in the coolant pipe. It leads to the oxidation of hot graphite at high temperatures, resulting in mechanical degradation of graphite structures. To address this issue, the authors propose a novel approach of substituting graphite fuel compacts with polycrystalline reaction-sintered SiC (RS-SiC) fuel compacts due to their superior oxidation resistance. The adoption of SiC based fuel compact will eliminate the graphite sleeves currently used in the pin-in-block type HTGR designs. It will also make it possible to achieve the high-power density due to the absence of graphite sleeves. There is limited understanding of the oxidation kinetics and transition behavior in RS-SiC. To address this knowledge gap, integrated experiments are conducted to investigate the thermal and oxidation behavior of SiC under varying oxygen concentrations. These experiments aim to provide insights into SiC's performance in HTGR environments using similar temperature and flow velocity conditions. Experimental data obtained will be utilized to develop a numerical model for enhanced understanding. In this study, both experimental and computational fluid dynamics (CFD) analyses were performed to compare the temperatures obtained from simulations with experimental measurements. The results demonstrated good agreement between experimental and numerical data. Passive oxidation was observed in real scale SiC fuel compacts at both 900 °C and 1100 °C, with slightly lower weight gain at the higher temperature. This suggests the possibility of damage to the SiO2 oxide layer at elevated temperatures. These results are important as the experiments are done in an integrated test facility using the air ingress accident boundary conditions of HTGR with the SiC fuel compact of real scale. These experiments validate the earlier findings from thermogravimetry differential thermal analysis (TG/DTA) conducted in a smaller-scale facility. They play a role in extending our understanding of SiC oxidation behavior, thereby assisting in the advancement of HTGR designs for enhanced safety and performance.

Aluminium dross waste utilization for phosphate removal and recovery from aqueous environment: Operational feasibility development

The need to minimize eutrophication in water bodies and the shortage of phosphate rock reserves has stimulated the search for sequestration and recovery of phosphate from alternative sources, including wastewater. In this study, aluminium dross (AD), a smelting industry waste/by-product, was converted to high-value material by encapsulation in calcium alginate (Ca-Alg) beads, viz. Ca-Alg-AD and utilized for adsorptive/uptake removal and phosphate recovery from an aqueous environment. Encapsulation of AD in alginate beads solves serious operational difficulties of using raw AD material directly due to density difference constraining efficient contact of AD with pollutants present in water and post-treatment recovery of AD material. The phosphate removal was evaluated in both batch and continuous flow operation modes. The batch adsorption study revealed 96.86% phosphate removal from 10 mg L−1 of initial phosphate concentration in 70 min of optimal contact time. Further, the phosphate removal potential of Ca-Alg-AD beads turned out to be independent of solution pH, with an average of 95.93 ± 1.40 % phosphate removal in the 2–9 pH range. The result reflects phosphate adsorption on Ca-Alg-AD beads following a second-order pseudo-kinetic model. Ca-Alg-AD beads-based adsorption followed Freundlich and Langmuir isotherm models. Further, a continuous packed bed column study revealed a total phosphate adsorption capacity of 1.089 mg g−1. The chemical composition, physical stability, and surface properties of Ca-Alg-AD beads were analyzed by means of state-of-the-art analytical techniques, such as Scanning Electron Microscopy-Energy Dispersive X-ray spectroscopy (SEM-EDX), Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetry/Differential Thermal Analysis (TG/DTA). These characterization techniques comprehend the mechanism and influence of surface properties and morphology on the phosphate adsorption behaviour, which induce the involvement of multiple mechanisms such as ligand complexation, ion exchange, and electrostatic attraction for phosphate adsorption on Ca-Alg-AD beads.

Rapid Photocatalytic Activity of Crystalline CeO2-CuO-Cu(OH)2 Ternary Nanocomposite

The development of a heterojunction nanocomposite leads to improved optoelectronic properties. Herein, ceria (CeO2), copper oxide (CuO), and ceria–copper–copper hydroxide (CeO2-CuO-Cu(OH)2) nanocomposites were prepared via a facile chemical method and their structural, morphological, and optical properties were studied using various characteristic techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM), ultra-violet visible light absorption (UV-visible), photoluminescence, and thermogravimetry differential thermal analysis (TG-DTA). In the integration of CeO2 and CuO with Cu(OH)2, the band gap is modified to 2.64 eV; this reduced band gap can improve the photocatalytic efficiency of the nanocomposite. The CeO2 can increase light absorption in the nanocomposite, while CuO acts as an electron trap in the composite and this leads to a good enhancement of the optical properties of the CeO2-CuO-Cu(OH)2 nanocomposite. In addition, the heterojunction combination at the interfaces of the CeO2-CuO-Cu(OH)2 nanocomposite facilitates the photo-generated charge separation in the composite, which increases the charge participation in the catalyzed conversion reactions of the prepared composite. The highest photocatalytic degradation efficiencies of 96.4% and 92.7% were achieved for fast green (FG) and bromophenol blue (BP), respectively, using the CeO2-CuO-Cu(OH)2 nanocomposite.

Influence of multi-stage processing and mechano-chemical treatments on the hydration and microstructure properties of recycled aggregate concrete

On account of the shortage of naturally occurring coarse aggregate, recycled aggregate (RA) made from crushed concrete debris is now used in the construction industry. With this rise in the utilisation of recycled aggregate in the construction sector, there has been extensive research into ways to improve its quality. The significant fraction of mortar remains that are left on the RA surface is the primary factor that affects its quality. Concrete made from RA loses strength and mechanical performance due to the attached mortar's increased porosity and water absorption values and the frailer transition region between the new mortar and aggregates. In order to minimise the old cement fractions and increase the quality, this paper studies the effect of concrete incorporating multi-stage processed RA from demolished concrete waste, followed by treatment with mechanical abrasion and sodium silicate immersion. The recycled aggregates were produced through multi-stage jaw crushing, followed by utilising natural aggregate, recycled aggregate, and recycled aggregate obtained after mechanical abrasion, followed by sodium silicate treatment for concrete mix design at various substitution percentages as coarse aggregates. The experimental investigation further progresses with the evaluation of mechanical and durability properties of concrete mixes, which is additionally followed by microstructural studies such as scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDAX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Thermogravimetry-differential thermal analysis (TG-DTA). The outcomes demonstrate that two-stage treatment, such as mechanical abrasion followed by sodium silicate immersion, yields superior-quality RA. Recycled aggregate concrete (RAC) made with these treated aggregates illustrated an increase in workability and density with respect to an untreated RAC mix. Furthermore, comparable strengths in compression, flexure, and tension are found in treated RAC mixes, particularly at 35% replacement levels, with respect to concrete mixes comprised of natural aggregates. A similar trend is detected in the chloride penetration tests and water sorptivity tests. In addition, the microstructural investigation confirmed the formation of additional calcium silicate hydrate for treated RAC mixes, particularly for the 35% substituted RA mix. On the basis of the results, it is suggested that multi-stage jaw crushing followed by treatment through mechanical abrasion and sodium silicate can potentially enhance the mechanical, microstructural, and durability performance of RAC.

Parameters Synthesis of Na-Magadiite Materials for Water Treatment and Removal of Basic Blue-41: Properties and Single-Batch Design Adsorber

Na-magadiite materials were prepared from a gel containing a silica source, sodium hydroxide, and water via hydrothermal treatment at different temperatures (130 °C to 170 °C) and periods of time (1 day to 10 days). In this study, four silica sources were selected (fumed silica, colloidal silica, Ludox HS-40%, and Ludox AS-40%). Variable conditions such as sodium hydroxide and water contents were explored at a specific temperature and reaction time. The obtained materials were characterized by using X-ray diffraction (XRD), thermogravimetry differential thermal analysis TG-DTA, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), Fourier Transform Infrared spectroscopy (FTIR), solid 29Si magic angle spinning magnetic nuclear resonance (MAS MNR, and nitrogen adsorption isotherms. A pure Na-magadiite phase was obtained from the four silica sources at a synthesis temperature of 150 °C after a period of one to two days with a characteristic basal spacing of 1.54 nm. At a longer reaction time of 3 days and a higher temperature of 170 °C, Na-kenyaite with a basal spacing of 2.01 nm was achieved, in addition to a quartz phase. The content of water or sodium hydroxide in the gel affected the nature of the prepared phases. A cauliflower-like morphology was obtained from colloidal silica sources, while a different morphology was achieved using solid fumed silica. The 29Si solid NMR confirmed the presence of Q3 and Q4 silicon sites in the Na-magadiite materials. The optimal Na-magadiite materials at 150 °C for 2 days were assessed for their ability to remove Basic Blue-41 dye from artificially contaminated aqueous solution. The Langmuir equation was used to estimate the maximum removal capacity. A maximum removal capacity of 219 mg/g was achieved using Na-magadiite prepared from a Ludox-HS40% silica source, and a maximum removal capacity of 167 mg/g was observed for Na-magadiite prepared from fumed silica. Basic Blue-4’s removal percentage was enhanced at basic pH levels (8 to 10) to a maximum of 95%. These materials could be regenerated for seven cycles of reuse with a reduction of 27 to 40% of the original values. Therefore, Na-magadiite materials are promising and efficient removal agents for the removal of Basic Blue-41 from effluents.

Facile and green synthesis, crystal structure, antibacterial activity, Hirshfeld surface analysis, and computational investigation of a novel lithium(I) complex: Comparisons of theoretical and experimental analyses

A novel monovalent lithium complex, [Li(C6H4NO3)(H2O)2] (1), was prepared via a simple one-pot green reaction of 2-hydroxypyridine-3-carboxylic acid (2-hpca) with lithium carbonate and aminoguanidine (Amgu) bicarbonate in water. Complex 1 was investigated using elemental, ultraviolet–visible, Fourier transform infrared (FT-IR), thermal, and single-crystal X-ray diffraction (SC-XRD) measurements. We found that 1 crystallized in the monoclinic C2/m space group with a = 12.800(2) Å, b = 6.6657(13) Å, and c = 9.4687(19) Å. The Li ion exhibited four coordinates with a distorted square planar geometry. That is, the ion was surrounded by four oxygen atoms, of which two were derived from two water molecules, one was from the carboxylate group, and one was from the keto group of the 2-oxo-1,2-dihydropyridine-3-carboxylate ligand. Simultaneous thermogravimetry–differential thermal analysis of 1 exhibited dehydration followed by continuous low-temperature (∼400 °C) decomposition to produce lithium oxide as the end product in an air atmosphere. Furthermore, density functional theory (DFT) analysis was conducted to compare the theoretical and experimental data collected via SC-XRD. In addition, DFT was used to analyze the frontier molecular orbital energy levels and energy gaps. Moreover, we conducted Hirshfeld surface studies with respect to 1 to differentiate between the intermolecular hydrogen bond contacts. Energy frameworks for 1 were produced by analyzing the energy interactions between intermolecular hydrogen bonds to investigate the prevailing interactions involved in molecular packing. The in silico results showed that 1 has high potential for the development of antimicrobial drugs. Molecular docking studies were also conducted to determine the binding energy of 1 with Staphylococcus aureus (5CZZ) and Escherichia coli (3T88). The results were consistent with the experimental data obtained from the antibacterial activity of 1 with respect to Staphylococcus aureus and Escherichia coli.

In situ formation mechanism of the honeycomb structure of a vitrified-bond diamond composite

Vitrified-bond diamond composites are materials commonly used for grinding wheels in the grinding process of silicon wafer production. In this study, the mechanism of the in situ honeycomb structure formation in the sintering process of composite materials was explored by changing the binder content without adding a pore-forming agent.The results show when the content of vitrified bond is 55 wt%, the in situ honeycomb structure forms, resulting in a porosity of 60.68 % and bending strength of 23.03 MPa.The X-ray diffraction (XRD), Raman spectroscopy (RS), and thermogravimetry-differential thermal analysis (TG-DTA) results show that no graphitization of diamond grain occurs during sintering. The bonding ability between the vitrified bond and diamond grain, along with the microstructure of vitrified-bond diamond composites, was studied using scanning electron microscopy (SEM). Moreover, the results of energy spectrum analysis (EDS) show that the diffusion and segregation of Na at the interface between the diamond particles and the vitrified bond improve the bonding strength, and the vitrified bond can effectively bond with the diamond particles. Finally, the formation mechanism of the honeycomb structure was elucidated using the surface and interface sintering theory.

Viability of Bauxite Deposits from Catalonia (Spain) for Ceramic Applications

This study provides a characterization of materials from wastes and outcrops of two inactive bauxite mines located close to Sant Joan de Mediona and Peramola, Spain. Mineralogy was determined via powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Thermal properties were measured via differential thermal analysis–thermogravimetry (DTA-TG) and gresification tests. The crystalline phases are medium-high crystalline kaolinite and variable amounts of illite, quartz, calcite, boehmite, hematite and rutile/anatase. DTA show two endothermic peaks produced by the dehydroxylation of minerals: the first peak, at 530–538 °C, belongs to boehmite; the second peak, at 535–568 °C, corresponds to kaolinite. An exothermic peak at 950–978 °C is associated with mullite crystallization. The optimal sintering temperatures obtained from the gresification curves (firing shrinkage and water absorption) were 970 °C for carbonate-poor, illite-rich clays; 1100 °C for illite- and carbonate-poor samples; and near 1190 °C for carbonate-rich materials. The carbonate-poor samples fired at 1300 °C contain sillimanite and mullite, and the carbonate-rich materials are rich in gehlenite, anorthite, and hedenbergite. The mineralogy of these materials is sufficient to obtain ceramic materials with suitable properties, but not their low plasticity. They could be used in the formulation of bricks or as part of mixtures to produce refractory ceramics.

Ceramic 3D printing using lithium silicate prepared by sol-gel method for customizing dental prosthesis with optimal translucency

In dentistry, various ceramics have been tested to overcome the opacity of zirconia. Moreover, three-dimensional (3D) printing technology is being used to accurately reproduce intricate shapes and overcome material wastage. This study described the application of a lithium silicate 3D printing material for the fabrication of transparent ceramic dental prostheses and the optimization of the process. After synthesizing approximately 500 nm of lithium silicate powder using the sol-gel method, field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), were performed and rheological properties were evaluated. Then, the sintering conditions were set based on thermogravimetry differential thermal analysis (TG-DTA). A slurry for 3D printing containing 40 vol% powder along with a photocurable resin, an acrylate binder, and a dispersant was prepared. A specimen measuring 15 mm in diameter and 1.8 mm in height, with a layer thickness of 50 μm, was printed with a digital light process (DLP) 3D printer using different holding times (1, 3, 5, and 10 h) and at a final sintering temperature of 1325 °C among the preceding sintering conditions. The shrinkage rate, Vickers hardness, and translucency of the finished specimens were compared and analyzed. Our study terrified the possibility of 3D printing of lithium silicate. Furthermore, our results suggest that a long sintering holding time has a positive effect on the specimen characteristics.

Photocatalytic and Cathode Active Abilities of Ni-Substituted α-FeOOH Nanoparticles.

The present study investigates the relationship between the local structure, photocatalytic ability, and cathode performances in sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs) using Ni-substituted goethite nanoparticles (NixFe1-xOOH NPs) with a range of 'x' values from 0 to 0.5. The structural characterization was performed applying various techniques, including X-ray diffractometry (XRD); thermogravimetry differential thermal analysis (TG-DTA); Fourier transform infrared spectroscopy (FT-IR); X-ray absorption spectroscopy (XANES/EXAFS), both measured at room temperature (RT); 57Fe Mössbauer spectroscopy recorded at RT and low temperatures (LT) from 20 K to 300 K; Brunauer-Emmett-Teller surface area measurement (BET), and diffuse reflectance spectroscopy (DRS). In addition, the electrical properties of NixFe1-xOOH NPs were evaluated by solid-state impedance spectroscopy (SS-IS). XRD showed the presence of goethite as the only crystalline phase in prepared samples with x ≤ 0.20, and goethite and α-Ni(OH)2 in the samples with x > 0.20. The sample with x = 0.10 (Ni10) showed the highest photo-Fenton ability with a first-order rate constant value (k) of 15.8 × 10-3 min-1. The 57Fe Mössbauer spectrum of Ni0, measured at RT, displayed a sextet corresponding to goethite, with an isomer shift (δ) of 0.36 mm s-1 and a hyperfine magnetic distribution (Bhf) of 32.95 T. Moreover, the DC conductivity decreased from 5.52 × 10-10 to 5.30 × 10-12 (Ω cm)-1 with 'x' increasing from 0.10 to 0.50. Ni20 showed the highest initial discharge capacity of 223 mAh g-1, attributed to its largest specific surface area of 174.0 m2 g-1. In conclusion, NixFe1-xOOH NPs can be effectively utilized as visible-light-activated catalysts and active cathode materials in secondary batteries.

Magnetic core/shell structures: A case study on the synthesis and phototoxicity/cytotoxicity tests of multilayer graphene encapsulated Fe/Fe3C nanoparticles

This study reports on a novel and optimized synthesis procedure of multilayer graphene (MLG) encapsulated Fe/Fe3C nanoparticles using a combined method of spray drying, chemical vapor deposition (CVD) and leaching from FeCl3.6 H2O based precursor, in addition to phototoxicity/cytotoxicity tests for their potential use in biomedical applications. CVD studies were employed at various temperature/time and gas flow rate values. Based on the X-ray diffractometry (XRD), Raman spectroscopy, vibrating sample magnetometry (VSM), transmission electron microscopy/energy-dispersive spectroscopy (TEM/EDS) and differential thermal analysis/thermogravimetry (DTA/TG), CVD parameters of 900 °C, 60 min, 50 mbar and CH4/H2:1/1 were determined as optimum conditions. MLG encapsulated (d-spacing: 0.34 nm) nanoparticles consisting BCC Fe, FCC (Fe, C) and orthorhombic Fe3C phases were obtained with average core diameter of ∼45 nm and average shell thickness of ∼6 nm (8–50 layers). MLG encapsulated Fe/Fe3C nanoparticles were achieved with soft ferromagnetic (Ms: ∼64 emu/g; Hc: ∼276 Oe) property. MLG coated Fe/Fe3C nanoparticles were suspended in an aqueous media using poly/acrylic acid as a post-synthetic treatment. They were found cytocompatible even at 200 µg/mL and 75 µg/mL after 24 and 48 h exposure, respectively. Dose dependent cytotoxicity was studied on both MCF7 and HeLa cells after 72 h incubation. Light-to-heat conversion efficiency of these nanoparticles at 795 nm irradiation in water was calculated as 37.60 %. After laser irradiation, with an increased concentration of nanoparticles (75–200 µg/mL), more than 80 % cell death was observed on both MCF7 and HeLa cells lines via late apoptotic cell death as a result of photothermal effect.

Assessment of thermal stability of two N-ethoxyethyl-N-methylpiperidinium borate ionic liquids by non-Arrhenian incremental kinetic method

Thermal stability of two borate-based ionic liquids (ILs) recently proposed as effective additive for high voltage batteries, N-ethoxyethyl-N-methylpiperidinium bis(oxalato)borate (BOB) and N-ethoxyethyl-N-methylpiperidinium difluoro(oxalato)borate (DFOB), was investigated. Thermogravimetry–differential thermal analysis measurements performed under nitrogen at 1, 2, 4, and 7 °C min−1 show gradual mass loss above 220 °C for both compounds. The TG curves were processed by isoconversional kinetic analysis under the assumption of non-Arrhenian behavior. The outcome of the analysis suggests that even the initial decomposition stages occur by a complex mechanism, probably via competing evaporation–decomposition paths with relative contributions varying with the heating rate. The service lifetimes estimated by the kinetic analysis result in a stability of DFOB up to 10-times higher than that of BOB in the 25–125 °C range. Further experiments were carried out by the Knudsen effusion mass spectrometry (KEMS) in order to get information on the composition of the vapor phase produced upon heating under effusion conditions. The mass spectra of the vapor phase showed a rapid onset of decomposition at 110 °C and 130 °C for BOB and DFOB, respectively, with a large release of the ion species with m/q = 98. This decomposition path dominates the simple evaporation to neutral ion pairs, which was nonetheless observed at m/q = 172 (integer cation). All the results seem to point toward a higher stability of DFOB compared to BOB, most probably due to the charge-stabilizing inductive effect of fluorine atoms.

Reclamation of chromium-contaminated soil by native Cr(VI)-reducing and PHA-accumulating Bacillus aryabhattai CTSI-07.

Reclamation of chromium-contaminated soil by bacteria is a big confront concerning to soil health restoration, food safety, and environmental protection. Herein, the chromium-resistant Bacillus aryabhattai CTSI-07 (MG757377) showed resistance to 1000 and 300 ppm of Cr(VI) in nutrient rich Luria Bertani (LB) and nutrient-deficient sucrose low phosphate (SLP) medium, respectively. It reduced 96.7% of Cr(VI) from contaminated soil in the presence of 100 ppm of Mg within 96 h under optimized conditions. Furthermore, Cr(VI) reduction by the bacteria was validated by Fourier transform infrared spectroscopic (FTIR) and X-ray diffraction (XRD) analysis. Besides Cr(VI) reduction, the bacterial strain also showed plant growth promoting traits like N2 fixation and indole acetic acid (IAA) production. On the other hand, transmission electron microscopy (TEM) imaging confirmed polyhydroxyalkanoates' (PHAs) granule accumulation and 0.5 g/l of PHAs was extracted from bacterial cell using SLP medium. Infra-red (IR) spectra and proton nuclear magnetic resonance (1H NMR) chemical shift patterns established the PHAs as polyhydroxybutyrate (PHB). Melting (Tm) and thermal degradation (Td) temperature of the PHB were 169 °C and 275 °C, respectively, as evident from thermogravimetry differential thermal analysis (TG-DTA). Atomic force microscopic (AFM) imaging depicted that the PHB film surface was rough and regular. Furthermore, the multi-metal-resistant, plant growth-promoting, and PHB-producing bacteria could reduce 99.82% of Cr(VI) from contaminated soil within 120 days in pot culture. Thus, it can be used for long-term reclamation of chromium-contaminated soil to restore soil health, provide food safety, and environmental protection.

Synthesis, crystal growth, optical, thermal, electrical and theoretical investigation on 1,2,3- benzotriazole 2-chloro 4-nitrobenzoic acid (BCNB) single crystal for nonlinear optical (NLO) applications

The 1,2,3-benzotriazole 2-chloro-4-nitrobenzoic acid (BCNB) single crystal was successfully grown by the slow evaporation solution technique (SEST) and using methanol as the solvent for nonlinear optical applications. The crystal system and space group of the BCNB single crystal were identified by single crystal X-ray diffraction (SXRD) analysis. The BCNB crystal was subjected to powder X-ray diffraction (PXRD) to endorse the crystalline quality of the material. The UV–Visible-NIR study exposes the transparency and cut-off wavelength of the BCNB crystal. The chemical environment of carbon and hydrogen in the proposed structure of BCNB crystal was confirmed by FT-NMR studies. The vibrational assignments and their functional groups were identified from the FT-IR and FT-Raman analysis. The thermal properties like thermal stability point, melting point, and decomposing point were examined by Thermogravimetry/Differential thermal analysis (TG-DTA). The third order NLO behaviour of BCNB crystal was investigated by the Z-scan technique. The negative photoconductive nature of BCNB crystal was confirmed by photoconductivity analysis. The surface morphology of the grown crystal was examined by chemical etching analysis. The dielectric experiment (constant & loss) was performed on BCNB crystal as a function of frequency at room temperature to measure electrical properties of the material. Density functional theory (DFT) calculations have been investigated by DFT/B3LYP/6–311++G (d,p) method. To understand the intermolecular interaction of crystal packing, the BCNB material was investigated by Hirshfeld surface analysis and it was concluded that the molecular H-H interactions are of higher value compared to other interactions of the total molecules. The Gaussian 09 W programme was used for the DFT calculations such as molecule structure optimization, natural bond orbital analysis (NBO) and HOMO-LUMO analysis. The HOMO and LUMO energy values are estimated as −7.3239 eV and −2.8958 eV respectively.

Mineralogical analysis and firing temperature of the ancient potteries of Tamil Nadu using spectroscopic techniques

Our curiosity about archaeological artefacts leads us to discover details about the lifestyles of our ancestors. Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDX), and thermogravimetry differential thermal analysis (TG-DTA) techniques have been used to characterize the ancient potteries unearthed at the recently excavated archaeological site of Palayanur, Tamil Nadu. Minerals such as quartz (silicate group), feldspar, clay minerals (illite), calcite, hematite, magnetite, and organic carbon were identified from FT-IR analysis. Quartz had been detected in all of the samples, as evidenced by the significant absorption peaks at 794 cm−1, 795 cm−1, 779 cm−1, 780 cm−1, 781 cm−1, and 695 cm−1. The obtained 2θ values from the XRD spectrum validated the mineral’s presence as well as the pottery’s firing condition and temperature. The presence of calcite indicates that these samples were fired below 850 ℃, and the presence of hematite in the potteries indicates that they were fired in an oxidizing atmosphere. The elemental concentration and microstructure of collected pottery samples were determined by the SEM-EDX technique to elucidate the nature of the raw material used for making pottery samples.

Fractal-like kinetic modelling for sorption of diclofenac onto graphene oxide/polypyrrole composite: Mechanism analysis and response surface methodology for optimization

Graphene oxide/polypyrrole (GO/PPy) composite material was prepared to explore its utility in the removal of diclofenac from aqueous system. The characterization was achieved using Fourier transform infrared spectroscopy, X-ray powder diffraction analysis, thermogravimetry-differential thermal analyses, scanning electron microscopy coupled with energy dispersive X-ray analysis and transmission electron microscopy analysis. Response surface methodology was exploited to optimize the process variables for the sorption of diclofenac onto GO/PPy. Three variables such as contact time, adsorbent dose and initial concentration of diclofenac were selected for optimization to achieve maximum removal of diclofenac. All experiments were conducted at pH 5. The contact time, adsorbent dose and initial concentration of diclofenac were examined in the ranges of 03–37 min, 13–147 mg/25 mL and 10–110 mg/L, respectively. The optimum values obtained were: contact time: 20 min; GO/PPy dose: 80 mg/25 mL and initial diclofenac concentration: 60 mg/L. The maximum sorption capacity and percent removal of diclofenac were found to be 29.50 mg/g and 98.50 %, respectively. The measured data (at equilibrium) were investigated using different isotherm models and best described by Freundlich model (R2 = 0.9943–0.9952, χ2 = 0.0062–0.0077, APE = 1.45–1.61). The experimental kinetic data were analyzed with the help of fractal-like kinetic models. The kinetic data are best fitted by fractal-like mixed 1,2 order (R2 = 0.9830–0.9886, χ2 = 0.0014–0.0036, APE = 0.6780–1.1059). Adsorption mechanism has been discussed based on kinetic, FTIR and molecular docking studies which indicated the participation of π-π interactions and hydrogen bonding on energetically heterogeneous surface. The adsorption/desorption test demonstrated that GO/PPy had excellent reusability performance up to 15 cycles.