High-temperature Thermal Treatment Research Articles

High-temperature anaerobic calcination for stabilizing environmentally stressful elements in phosphoric acid production by-products

Phosphorus tailings (P) refer to the waste materials left over after the extraction of phosphorus from phosphate rock during mining and processing. phosphogypsum (PG) is typical by-products of phosphoric acid production (PPB), containing numerous environmentally hazardous elements (EHE) that pose significant risks to ecological safety. In this study, we examined the impact of high-temperature anaerobic calcination on the migration and immobilization of EHE in PPB. The results indicated that higher temperature ranges favorably controlled the leaching toxicity of PPB. In the calcination products of P and PG, the inhibition efficiency of Pb leaching toxicity reached 84.93% and 89.33%, respectively. Under higher temperature conditions (P at 700 °C, PG at 600 °C), the inhibition of Cr leaching toxicity reached 100%. The inhibitory effects of high-temperature environments on EHE in PPB were ranked as fluorine > phosphorus > heavy metals. The mechanisms of migration and transformation of EHE in PPB under high-temperature anaerobic calcination were elucidated in three aspects, ranked from strongest to weakest. Firstly, the encapsulation of EHE by a shell-like structure, attributed to the “melt-wrap” phenomenon. Secondly, the decomposition-gasification phenomenon induced by high-temperature conditions. Thirdly, the effect of high temperature on the transformation of the storage forms of EHE. This study fills a research gap in the field of thermal treatment of PPB, enhancing the understanding of the specific effects of thermal treatment on the transformation of EHE in PPB, and provides theoretical and data support for the high-temperature thermal treatment of solid wastes.

Gradual Optimization of Molecular Aggregation and Stacking Enables Over 19% Efficiency in Binary Organic Solar Cells.

Volatile solid additive is an effective and simple strategy for morphology control in organic solar cells (OSCs). The development of environmentally friendly new additives which can also be easily removed without high-temperature thermal annealing treatment is currently a trend, and the working mechanism needs to be further studied. Herein, a highly volatile and non-halogenated solid additive 1-benzothiophene (BBT) is reported to regulate molecular aggregation and stacking of active layer components. According to the film-forming kinetics process, a momentary intermediate phase is formed during spin-coating, which slows down the film-forming process and leads to more ordered molecular stacking in the solid film after introducing solid additive BBT. Subsequently, after solvent vapor annealing (SVA) further treatment, the resultant blend films exhibit a tighter and more ordered molecular stacking. Consequently, the synergistic effect of solid additive BBT and SVA treatment can effectively control morphology of active layer and improve carrier transport characteristics, thereby enhancing the performance of OSCs. Finally, in D18-Cl:N3 system, an impressive power conversion efficiency of 19.53% is achieved. The work demonstrates that the combination of highly volatile solid additives and SVA treatment is an effective morphology control strategy, guiding the development of efficient OSCs.

PDMS-Based Hierarchical Superhydrophobic Fabric Coating Fabricated by Thermal Treatment and Electrostatic Flocking Technology.

Superhydrophobic coatings have broad applications in a variety of industries. By using a low-surface-energy material and creating nanoscale roughness, a superhydrophobic surface can be produced. To overcome the health and environmental concerns of fluorine-based materials and the limitations of large-scale rough microstructure fabrication, a poly(dimethylsiloxane) (PDMS)-based hierarchical superhydrophobic fabric coating prepared by simple thermal treatment and electrostatic flocking technology was introduced in this study. High-temperature thermal treatment is employed to create PDMS nanoparticle-decorated carbon fibers, which are further vertically implanted onto the surface of cotton fabric via electrostatic flocking technology. The environmentally friendly PDMS nanoparticles were adopted as low-surface-energy materials, and the electrostatic flocking technology was utilized to generate a vertically aligned carbon fiber array coating, mimicking a lotus leaf-like superhydrophobic surface microstructure. Therefore, an ultrahigh water contact angle of 173.9 ± 2.8° and a low sliding angle of 1 ± 0.5° can be obtained by the fabric coating with a PDMS-to-carbon fiber ratio of 20:1. The prepared superhydrophobic fabric also exhibits an excellent self-cleaning property and great durability after 60 cycles of washing. Through commercially available thermal treatment and electrostatic flocking processes, this strategy for fabricating fluorine-free superhydrophobic fabric can be easily scaled up for commercial manufacturing and promotes the design of superhydrophobic coatings for other substrates.

Effect of thermal and non-thermal processing methods on the Structural and Functional Properties of Whey Protein from Donkey Milk

This study evaluated the impact of thermal, ultrasonication, and UV treatment on the structural and functional properties of whey proteins from donkey milk (DWP). Whey proteins exhibited notable stability in non-heat-treated environments, while their structural and functional characteristics were notably impacted by excessive heat treatment. The application of high-temperature long-time thermal treatment (HTLT) resulted in a decrease in fluorescence intensity, foaming and emulsification stability, and considerable damage to the active components of the proteins. Specifically, the preservation of lysozyme activity was only 23%, and lactoferrin and immunoglobulin G exhibited a significant loss of 70% and 77%, respectively. Non-thermal treatment methods showed superior efficacy in preserving the active components in whey proteins compared with heat treatment. Ultrasonic treatment has demonstrated a notable capability in diminishing protein particle size and turbidity, and UV treatment has been observed to have the ability to oxidize internal disulfide bonds within proteins, consequently augmenting the presence of free sulfhydryl groups, which were beneficial to foaming and emulsification stability. This study not only offers a scientific basis for the processing and application of DWP but also serves as a guide to produce dairy products, aiding in the development of dairy products tailored to specific health functions.

Chemical Stability of High-Entropy Spinel in a High-Pressure Pure Hydrogen Atmosphere.

This paper focuses on high-entropy spinels, which represent a rapidly growing group of materials with physicochemical properties that make them suitable for hydrogen energy applications. The influence of high-pressure pure hydrogen on the chemical stability of three high-entropy oxide (HEO) sinter samples with a spinel structure was investigated. Multicomponent HEO samples were obtained via mechanochemical synthesis (MS) combined with high-temperature thermal treatment. Performing the free sintering procedure on powders after MS at 1000 °C for 3 h in air enabled achieving single-phase (Cr0.2Fe0.2Mg0.2Mn0.2Ni0.2)3O4 and (Cu0.2Fe0.2Mg0.2Ni0.2Ti0.2)3O4 powders with a spinel structure, and in the case of (Cu0.2Fe0.2Mg0.2Ti0.2Zn0.2)3O4, a spinel phase in the amount of 95 wt.% was achieved. A decrease in spinel phase crystallite size and an increase in lattice strains were established in the synthesized spinel powders. The hydrogenation of the synthesized samples in a high-pressure hydrogen atmosphere was investigated using Sievert's technique. The results of XRD, SEM, and EDS investigations clearly showed that pure hydrogen at temperatures of up to 250 °C and a pressure of up to 40 bar did not significantly impact the structure and microstructure of the (Cr0.2Fe0.2Mg0.2Mn0.2Ni0.2)3O4 ceramic, which demonstrates its potential for application in hydrogen technologies.

Multifunctional mullite fiber reinforced SiBCN ceramic aerogel with excellent microwave absorption and thermal insulation performance

Mullite fibers have been widely used in thermal protection materials, but they still face challenges related to inefficient wave absorption performance. SiBCN aerogel has the advantage of tunable dielectric properties, outstanding microwave absorption performance, low density and low thermal conductivity, making it an ideal candidate for enhancing mullite fibers. Herein, a novel SiBCN aerogel/mullite fiber composite (SiBCN/MF composite) was prepared by sol-gel, freeze-drying and high temperature thermal treatment for the first time. By tuning the concentration of polyborosilazane (PBSZ), the density, microwave absorption performance, and thermal insulation properties were regulated. The obtained composites displayed low density (0.151–0.190 g/cm3), excellent microwave absorption performance (the minimum reflection loss as low as −67.83 dB and effective absorption bandwidth of 5.40 GHz) and low thermal conductivity (0.056–0.081 W/(m·K)). The outstanding comprehensive performance of the fabricated composites makes them promising candidates for use in the thermal protection system of aerospace vehicles.

Enhanced visible-light induced photocatalytic activity in core-shell structured graphene/titanium dioxide nanofiber mats

Semiconductor photocatalysts suffer from low photocatalytic quantum efficiency, diminished solar energy utilization, and inadequate photostability, thereby impeding their widespread adoption. Meanwhile, graphene emerges as an ideal substrate material for fabricating high-performance composite photocatalysts owing to its distinctive single-layer sp2-hybridized carbon atom arrangement, substantial specific surface area, exceptional electron conductivity, and pronounced transparency. In this study, a graphene-anatase-rutile core-shell structured nanofiber mat architecture is successfully synthesized by sol-gel-assisted coaxial electrospinning with high-temperature thermal treatment. This innovative architecture effectively narrows the bandgap of TiO2 and synergizes adsorption and catalysis processes to achieve heightened catalytic efficiency and prolonged stability. Photocatalytic assays conducted under visible light irradiation demonstrate the excellent photocatalytic activity and stability of the graphene-titanium dioxide hybrid material during the degradation of phenol. The kinetics and mechanism of the phenol degradation of the nanofiber mat have been explored. Furthermore, the unique mesh-like configuration intrinsic to the nanofiber assembly confers sedimentation and recyclability upon the composite material.

Formation of volatile chlorinated and brominated products during low temperature thermal decomposition of the representative PFAS perfluorohexane sulfonate (PFHxS) in the presence of NaCl and NaBr

Per- and polyfluoroalkyl substances (PFAS) are synthetic organofluorine compounds known for their chemical and physical stability as well as their wide range of uses. Some PFAS are widely distributed in the environment, leading to concerns related to both environmental and human health. High temperature thermal treatment (i.e., incineration) has been utilized for PFAS treatment, but this requires significant infrastructure and energy, prompting interest in lower temperature approaches that may still lead to efficient destruction. Lower treatment temperatures, however, increase the potential for incomplete PFAS mineralization and formation of volatile organofluorine (VOF) products. Herein, we report the formation of novel VOF products that include chlorinated and brominated compounds during the thermal treatment of potassium perfluorohexane sulfonate (PFHxS), a representative perfluoroalkyl acid (PFAA). By comparing the gas chromatography-mass spectrometry (GC-MS) results of known VOF stocks to evolved VOF during thermal treatment of PFAS, the formation of perfluorohexyl chloride and perfluorohexyl bromide was observed when PFHxS was heated at temperatures between 275 and 475 °C in the presence of NaCl and NaBr, respectively. To our knowledge, this is the first report of chlorinated or brominated VOF products during thermal treatment of a PFAA. These findings suggest that a range of mixed halogenated VOF may form during thermal treatment of PFAS at relatively low temperature (e.g., 500 °C) and that these can be a function of salts present in the matrix.

Debundling and reorganization of CNT networks under high temperature treatment

Highly purified and uniformly distributed carbon nanotube (CNT) network is one of the key issues for developing advanced nanocomposites. However, the challenge for mitigation of the aggregation of CNT bundles during the CNT film fabrication still remained. In this work, debundling and reorganization of CNT bundles have been realized simultaneously by using a high-temperature thermal treatment. The debundling of large CNT bundles into small ones started after they were heat treated under 1400 °C and uniformly distributed CNT networks with small bundles were obtained after heat treated under 1800 °C. The tensile strength of the CNT film significantly increased by about 64% compared to the pristine film. Microstructural observations showed that the iron nanoparticles started to evaporate at 1400 °C and were completely removed at 1800 °C. Hollow amorphous carbon shells wrapped on the nanoparticles were left inside the CNT networks after the removal of the iron nanoparticles. Interestingly, these amorphous carbon shells act as carbon source for the deposition of a carbon layer on the CNT surface when the heat treatment temperature was up to 2000 °C, and they were completely consumed after being treated at 2800 °C. The microstructural evolution process of CNT bundles during heat treatment suggests the simple high-temperature treatment strategy could be applied for fabrication of highly purified CNT networks with well-distributed small bundles, enabling the development of advanced multifunctional nanocomposites in the near future.

A review of computational and experimental analysis of high temperature thermal treatment of wood based on thermowood technology

A review of computational and experimental analysis of high temperature thermal treatment of wood based on thermowood technology

Effect of high temperature thermal treatment on the electrochemical performance of natural flake graphite

Natural graphite is currently considered as a critical raw material in EU. The demand for graphite is still increasing as it is commonly used in the anodes of the Li-ion batteries (LIBs). The total graphite content for energy storage applications such as LIBs should be more than 99.95%. Several purification processes for natural graphite exist but the requirement of high purity is challenging. Here we present the high temperature thermal treatment for natural graphite ores. Thermal treatment at 2400 °C for 15 min can produce battery-grade graphite with high purity and crystallinity needed for the optimum performance of the battery cells. In addition, the crystallinity and crystalline structure of graphite was improved during the treatment. The electrochemical studies of thermally treated graphite powders showed increased electrochemical performance compared to the untreated graphite samples. The improved performance was attributed to the increased purity and crystallinity of the thermally treated powders.Graphical Effect of thermal purification on the electrochemical performance of natural flake graphite

Thermal decomposition mechanism and characterization of phosphogypsum in suspension under multifactor coupling effect

Phosphogypsum (PG) is solid waste generated by the phosphate fertilizer industry. However, by high-temperature thermal treatment, it can be effectively decomposed into byproducts like SO2 and CaO, which are valuable raw materials for the production of sulfuric acid and construction materials, respectively. In this study, we investigated the thermal decomposition properties of suspended PG, as well as the factors governing the PG decomposition procedure. The results show that the PG decomposition rate was influenced by several parameters, with temperature being the most significant, followed by time, atmosphere, and charcoal powder dosing. Similarly, the desulfurization rate was primarily influenced by time, followed by temperature, atmosphere, and charcoal powder dosing. The PG exhibited maximum decomposition and desulfurization rates of 97.73% and 97.2%, respectively, at a calcination temperature of 1180 °C, a calcination period of 15 min, a carbon powder dosage of 4%, and a CO concentration of 6%. Kinetic studies revealed that the activation energy of the PG decomposition reaction decreased from 303.45 to 254.28 kJ/mol as the CO concentration increased from 4% to 6% upon addition of charcoal powder as a reducing agent. Furthermore, higher CO concentrations had a more pronounced effect on lowering the activation energy of PG pyrolysis. When the contents of SiO2 and Al2O3 impurities in the PG content were higher, they reacted with CaO in the decomposition products to produce silicate and aluminate minerals, respectively, decreasing both the CaO content in the product and the PG decomposition rate.

Crystal structures, bonding and electronic structures of α- and β-Ir2B3-x compounds.

The binary boron-rich compounds α-Ir2B3-x and β-Ir2B3-x, formerly denoted as α- and β-Ir4B5, were synthesized via both arc melting followed by annealing at 800 °C (900 °C) and high-temperature thermal treatment of mixtures of the elements. X-ray structure analysis of α-Ir2B3-x was performed on a single crystal (space group C2/m, a = 10.5515(11) Å, b = 2.8842(3) Å, c = 6.0965(7) Å, β = 91.121(9)°). The orthorhombic structure of β-Ir2B3-x was confirmed by X-ray powder diffraction (space group Pnma; a = 10.7519(3) Å, b = 2.83193(7) Å, c = 6.0293(1) Å). The α-Ir2B3-x structure exhibits ordered arrangements of iridium atoms. The structure is composed of corrugated layers of boron hexagons (interlinked via external B-B bonds) alternating with two corrugated layers of iridium along the c-direction; an additional boron atom (Oc. 0.46(7)) is located between iridium layers in Ir6 trigonal prisms. The boron partial structure in β-Ir2B3-x is composed of ribbons made up of slightly corrugated quadrilateral units running along the b-direction in the channels formed by 8 iridium atoms each. DFT calculations revealed a number of bands crossing the Fermi level, predicting metallic behaviors of the two compounds. β-Ir2B3-x is characterized by a pseudogap around the Fermi level and a smaller eDOS of 0.6405 states per eV per f.u. at the Fermi level, as compared to the α-Ir2B3-x value of 1.405 states per eV per f.u. The calculated electron localization functions revealed strong covalent bonds between boron atoms in the core part of the B6 hexagons, metallic B-B bonds within the quadrilateral boron partial structure and mixed covalent and metallic interactions between iridium and boron atoms. Structural relationships of α-Ir2B3-x and β-Ir2B3-x with ReB2-type structures as well as the common structural features with layered binary borides with CrB-type related structures have been discussed.

Chemical activation of atom-precise Pd3 nanoclusters on γ-Al2O3 supports for transfer hydrogenation reactions.

Deposition of atom-precise nanoclusters onto solid supports is a promising route to synthesize model heterogeneous catalysts. However, to enhance nanocluster-support interactions, activation of the nanoclusters by removal of surface ligands is necessary. Thermal treatment to remove surface ligands from supported metal nanoclusters can yield highly active heterogeneous catalysts, however, the high temperatures employed can lead to poor control over the final size and speciation of the nanoclusters. As an alternative to high-temperature thermal treatments, chemical activation of [Pd3(μ-Cl)(μ-PPh2)2(PPh3)3]+ (Pd3) nanoclusters on γ-Al2O3 supports under mild reaction conditions has been demonstrated in this work. Hydride-based reducing agents such as NaBH4, LiBH4, and LiAlH4 have been examined for the activation of the Pd3 nanoclusters. The structural evolution and speciation of the nanoclusters after activation have been monitored using a combination of XAS, XPS, STEM-EDX mapping, and solid-state NMR techniques. The results indicate that treatment with borohydride reducing agents successfully removed surface phosphine and chloride ligands, and the extent of size growth of the nanoclusters during activation is directly correlated with the amount of borohydride used. Borate side products remain on the γ-Al2O3 surface after activation; moreover, exposure to high amounts of NaBH4 resulted in the incorporation of B atoms inside the lattice of the activated Pd nanoclusters. LiAlH4 treatment, on the other hand, led to no significant size growth of the nanoclusters and resulted in a mixture of Pd single-atom sites and activated nanoclusters on the γ-Al2O3 surface. Finally, the catalytic potential of the activated nanoclusters has been tested in the transfer hydrogenation of trans-cinnamaldehyde, using sodium formate/formic acid as the hydrogen donor. The catalytic results showed that smaller Pd nanoclusters are much more selective for hydrogenating trans-cinnamaldehyde to hydrocinnamaldehyde, but overall have lower activity compared to larger Pd nanoparticles. Overall, this study showcases chemical activation routes as an alternative to traditional thermal activation routes for activating supported nanoclusters by offering improved speciation and size control.

Perovskite evolution on La modified Mn1.5Co1.5O4 spinel through thermal ageing with enhanced oxidation activity: Is sintering always an issue?

Non-precious metal oxides have great potential in catalytic deep oxidation of emitted hydrocarbons to help address various environmental pollution concerns. However, sintering issue is a stumbling block in practical application upon long-term high-temperature operation or thermal shock experience. Herein, La was applied to modify Mn1.5Co1.5O4 spinel to get a highly active oxidation catalyst with exceptional stability against high-temperature thermal ageing treatment. With thermal ageing at 750 °C for 100 h, the La modified Mn–Co composite reached 90 % conversion in toluene oxidation at 265 °C under the high WHSV of 120,000 mL g−1 h−1, while this value increased to 312 °C over blank Mn–Co spinel. The addition of La not only inhibited the growth of spinel nanocrystals, but also brought about perovskite formation through sintering, generating perovskite-spinel interfaces, thus enhancing both activity and stability. Meanwhile, the La modified Mn–Co spinel exhibited superior performance in presence of water or sulfur dioxide after thermal ageing treatment. This work offers a versatile strategy to design anti-sintering and active oxidation nanocatalysts based on non-precious metal oxides for industrial applications.

Efficient broadband yellow-emitting Mg2.5Lu1.5Al1.5Si2.5O12:Ce3+ garnet phosphors for blue-light-pumped white light-emitting diodes

The discovery of yellow-emitting phosphors with higher luminescence intensity and wider bandwidth than the commercial Y3Al5O12:Ce3+ (YAG:Ce3+) phosphor upon blue light excitation remains one of the significant challenges for establishing human-centered warm white light-emitting diode towards high-performance illumination. Herein, we innovatively synthesized a novel Ce3+-activated broadband yellow-emitting garnet phosphor of Mg2.5Lu1.5Al1.5Si2.5O12:Ce3+ (MLASO:Ce3+) via conventional high-temperature solid-state reaction method. The as-prepared MLASO:10%Ce3+ garnet sample possesses a cubic structure with Ia3‾d space group and lattice parameters of a = b = c = 11.85098 Å and V = 1664.421(0.044) Å3. Luminescence spectroscopy tests indicates that the optimal MLASO:10%Ce3+ yellow-emitting phosphor features 1.2 times higher relative integral luminescence intensity and an impressive full width at half maximum (FWHM) of up to 145 nm with respect to the most extensively available commercial YAG:Ce3+ phosphor (FWHM = 122 nm) under the identical blue light irradiation, which can provide more red-components for improving color rendering index. Additionally, the CIE color coordinates and a satisfactory internal quantum efficiency are determined to be (0.4751,0.5028) and 74%, respectively. More importantly, the representative optimal sample can preserve 77% luminescence emission intensity at a 423 K high temperature thermal treatment environment compared to the ambient temperature. As a result, this study sheds light on newly discovered broadband yellow-emitting MLASO:10%Ce3+ garnet phosphor containing more of the red chromatic spectrum can sever as one of the promising color-conversion-materials in high-performance white LEDs with high color rendering index for healthy solid-state lighting.

Investigation of Fracture Evolution and Failure Characteristics of Rocks under High-Temperature Liquid Nitrogen Interaction

The utilization of liquid nitrogen as a sustainable and water-free fracturing medium exhibits immense promise in engineering applications. In this investigation, Brazilian split tests and acoustic emission tests were conducted to explore the impact of liquid nitrogen cooling on the internal structure and mechanical properties of rock specimens. To examine the influence of liquid nitrogen cooling on the tensile strength of rocks, displacement-load curves were obtained from samples subjected to varying cycles of high-temperature liquid nitrogen cooling using Brazilian split tests. Acoustic emission experiments were conducted to investigate the characteristics of granite samples exposed to various cycles of high-temperature liquid nitrogen cooling. Based on these findings, the impact of liquid nitrogen cooling on the internal structure of rock masses was analyzed. The findings of this study demonstrate that high-temperature liquid nitrogen thermal treatment significantly modifies the microscopic structure and mechanical properties of rocks, with potential implications for overall stability and reliability. Notably, an observable decline in tensile strength was observed as the number of cycles of high-temperature liquid nitrogen treatment increased. These findings underscore the substantial impact of liquid nitrogen cooling on the behavior of rocks. High-temperature liquid nitrogen treatment effectively promotes the generation of microcracks within rocks, thereby increasing their permeability. During the experiment, granite specimens primarily exhibited shear-type fractures when subjected to high-temperature freeze-thaw cycles induced by liquid nitrogen.

The effects of high temperature thermal treatments on β-Ga2O3 films grown on c-sapphire by low-pressure CVD

As a simple and effective method for improving the crystalline quality of epitaxial Ga2O3 film, post-thermal treatment has been identified as a competitive process involving crystal reconstruction accompanied by defect formation. In this study, β-Ga2O3 films grown on a c-sapphire substrate using low-pressure chemical vapor deposition were subjected to thermal treatment at 1000 °C in air for various duration to investigate the effects of treatment time on the films. The full width at half maximum (FWHM) of x-ray rocking curves initially decreased from 1.62° to 0.98° with increasing treatment time up to 5 h, indicating improved crystallinity. This improvement is likely a result of the reduced angle between Ga2O3 grains and the reconstructed Ga2O3 lattice, oriented towards the (−201) plane due to the thermal treatment, as observed in the transmission electron microscope and electron back-scattering diffraction results. However, under 7 h of treatment, the crystallinity of Ga2O3 degraded, as evidenced by an increased FWHM, as well as by x-ray photoelectron spectroscopy, photoluminescence, and time-of-flight secondary ion mass spectrometry results. This degradation can be attributed to the presence of massive oxygen vacancies and the substitutional incorporation of nitrogen into oxygen sites (NO), resulting in defects.

Electrochemical Exfoliation and Thermal Deoxygenation of Pristine Graphene for Various Industrial Applications

The transition of graphene from the lab to consumer goods is still a challenging job that necessitates efficient and cost-effective large-scale graphene production. This study combines electrochemical exfoliation in an aqueous solution of sulfuric acid (1M H2SO[Formula: see text] and hydrogen peroxide (3% H2O[Formula: see text] followed by thermal deoxygenation at a temperature of 800[Formula: see text]C within the ambient environment. This method allows the inexpensive synthesis of pristine graphene for various industrial applications. X-Ray diffraction (XRD) results for pristine graphene showed a distinct peak at 2[Formula: see text] with a corresponding interplanar distance ([Formula: see text] of 3.3754 Å and a crystallite size of 18 nm. XRD statistics indicated that the crystal structure of the original graphene was preserved. The crystalline structure was recovered and the interplaner distance was decreased following the high temperature thermal reduction. According to Raman spectroscopy, the impurity degree (I[Formula: see text]/I[Formula: see text] region fraction of pristine graphene was 0.211. This indicates that the original graph produced by the current method has little distortion. Raman analysis shows that there is a linear red shift in peaks D-band (D), G-band (G), and second order of the D-band (2D) due to the increase in phonon–phonon nonlinear interactions with increasing temperature, so that peaks (D), (G) and (2D) shifts are shown. The majority of the functional groups were discovered to be eliminated after high temperature thermal treatment. The three-dimensional graphene sheet is highly defined and intricately coupled in the microstructure analysis, resulting in a laxer and porous structure. When treated at a temperature below 800[Formula: see text]C, there was only minor damage to the reduced graphene oxide (RGO) microstructure. The results of the Atom Force Microscope (AFM) demonstrated that the flaws spread over time from the layer boundaries and pores to the edges and eventually resulted in a separate RGO archipelago. According to TGA analysis, at temperatures up to 800[Formula: see text]C, the RGO sheet loses up to 45% of its weight.

Effect of low sintering temperature on the structural and magnetic properties of M-type strontium hexaferrite

A pure M-type strontium hexaferrite with nominal composition SrFe12O19 has been prepared via the modified conventional citrate precursor method.The entirework emphasizes on improvingthe standardof hexagonal ferrite without undergoing high-temperature thermal treatments. By incorporating some adjustments in processing conditions, the prepared sampleis sintered at 800 °C and 910 °C, identified through thermalgravimetric analysis(TGA/DTA). The impact of the low-temperature sintering process on structural, spectroscopic, and magnetic properties are investigated via using different characterization techniques like XRD, FESEM, FTIR, Raman spectroscopy (RS), and VSM respectively. The XRD confirmed the formation of the M-phasealong withsome impurities of Fe2O3 and these results are strongly supported via both FTIR and RS. Similarly, FESEM analysis confirmed the formation of densely packed grains some hexagonal platelets. The magnetic properties of SrM hexaferrites show the increment of saturation magnetization Ms from 81 emu/g to 92 emu/g as the sintering temperature increases from 800 °C to 910 °C. Apart from the higher Ms for SrM hexaferrite, the Hc values 107 Oe and 262 Oe respectively are the vital findings of this research. This rare nature of SrM hexaferrite signifies the erection of soft character in hard SrM hexaferrites. Moreover the abrupt increase in the squarenes ratio (SQR) from 0.26 to 0.54 represents the transformation from multidomains to single domain. Material with such properties can be utilized in switching devices, recording media, high frequency applications.