Influence Of High-temperature Treatment Research Articles

Microstructural investigation and performance of carbon matrix composites developed through facile pitch modification route

Increasing demand of high-performance materials lead to development of composites with affordable cost and processing route. Present work involves facile chemical modification (nitric acid and melamine) route to produce carbon matrix composites exhibiting progressive performance. Modified pitches and resultant carbon matrix composites were characterized by FTIR, optical microscopy, SEM, XRD, TGA, TMA, tribological study and compression strength. Chemical treatment given to pitch imparts active functional groups which help to improve affinity between pitch particles. Additionally, to evaluate influence of high temperature treatment, composites were also heated to 1400 °C. Optical images show that microstructure of carbonized (1000 °C) and further heat-treated (1400 °C) composites contain fine isotropic grains and flow domains, attributed to the effective influence of chemical modification. SEM images and Raman spectroscopy also confirmed the similar results of arrangement of carbon layers. TGA analysis revealed that heat-treated composites with acid modified pitch have better thermal stability at 800 °C in zero air. Coefficient of thermal expansion of all composites was measured and found very low i.e. 5 to 10 ppm/°C. Chemical treatment applied to the pitch yielded improved results for tribological performance, coupled with enhanced compressive strength. Notably, up until the present, it was difficult to find reports on fabrication of carbon matrix composites from chemically modified pitch.

The Impact of High Temperature on Microbial Communities in Pork and Duck Skin.

Pork skin and duck skin are highly favored by consumers in China, and high-temperature processing methods are widely employed in cooking and food preparation. However, the influence of high-temperature treatment on the microbial communities within pork skin and duck skin remains unclear. In this study, a high-temperature treatment method simulating the cooking process was utilized to treat samples of pork skin and duck skin at temperatures ranging from 60 °C to 120 °C. The findings revealed that high-temperature treatment significantly altered the microbial communities in both pork skin and duck skin. Heat exposure resulted in a decrease in microbial diversity and induced changes in the relative abundance of specific microbial groups. In pork skin, high-temperature treatment led to a reduction in bacterial diversity and a decline in the relative abundance of specific bacterial taxa. Similarly, the relative abundance of microbial communities in duck skin also decreased. Furthermore, potential pathogenic bacteria, including Gram-positive and Gram-negative bacteria, as well as aerobic, anaerobic, and facultative anaerobic bacteria, exhibited different responses to high-temperature treatment in pork skin and duck skin. These findings highlighted the substantial impact of high-temperature processing on the composition and structure of microbial communities in pork skin and duck skin, potentially influencing food safety and quality. This study contributed to an enhanced understanding of the microbial mechanisms underlying the alterations in microbial communities during high-temperature processing of pork skin and duck skin, with significant implications for ensuring food safety and developing effective cooking techniques.

Influence of High Temperature Treatment of C/C Porous Preform on Friction and Wear Behavior of C/C-SiC Composites

Influence of High Temperature Treatment of C/C Porous Preform on Friction and Wear Behavior of C/C-SiC Composites

INFLUENCE OF HIGH TEMPERATURE TREATMENT ON THE MECHANICAL CHARACTERISTICS OF CARBON-CARBON COMPOSITE MATERIALS WITHPYROCARBON MATRIX

Pyrolytic compaction of porous substrates is one of the methods for obtaining carbon-carbon composite materials. When using such materials at high temperatures, for example, as elements of heaters, it is necessary to take into account the effect of high temperatures on their mechanical characteristics. In this work, the influence of high-temperature treatment on me-chanical characteristics was studied and the mechanism of destruction of samples of the mate-rial "Argolon GR" produced by JSC "Composite" was considered. It is shown that with an in-crease in the processing temperature from 1800 to 2400 °C, the open porosity of the samples increases in proportion to the increase in the number and size of cracks in the samples. The compressive failure stress depends very weakly on temperature, however, the graph of the corresponding dependence clearly shows its slight decrease with an increase in the processing temperature from 2000 to 2400 °C, which corresponds to the accumulation of damage in the material matrix that reduces its strength. Attention is drawn to a significant increase in the ten-sile strength of the material after high-temperature treatment, which is not typical for carbon-carbon composite materials. The dependence of the breaking stress in tension with an increase in the processing temperature for material samples has a pronounced maximum at 2000 °C. The analysis of the change in impact strength, the roughness parameter of the fracture surface of the samples, and the breaking stress in tension showed that the dominant mechanism during fracture is the mechanism of strength increase associated with the violation of the compatibility condition of deformations in the components of the material, while the effect of thermal stress relaxation is very small.

Microplastics in sewage sludge destined to anaerobic digestion: The potential role of thermal pretreatment

Microplastics (MPs) are plastic particles with size smaller than 5 mm: their removal in municipal wastewater treatment plants mostly results in the accumulation of the coarser fraction into the sludge. The common application of the treated sludge as soil amendment raises the issue of the uncontrolled release of MPs into the environment, which depicts the need to identify suitable counteraction strategies. This work briefly reviews the most recent studies that focus on the fate of MPs during conventional sludge treatments, and, based on the results of this analysis, proposes the thermal pretreatment (120 °C, 30 min) of waste activated sludge (WAS) containing different kinds of MPs, in order to investigate its effect on the anaerobic biodegradability as well as on the abundance and physical features of MPs. Experimental results show that high temperatures did not alter polyethylene terephthalate (PET) MPs but the biodegradable-compostable ones (BIO-MPs), complying with the UNI EN 13432 standards. The profile of methane generation from thermally pretreated samples containing PET-MPs do not indicate any inhibition of the anaerobic process, which was positively influenced by the BIO-MPs in WAS: a 100% and 25% methane increase was observed over the control samples with and without the thermal pretreatment, respectively. Further studies are needed to better understand the mechanisms underlying biodegradable MPs behavior as well as to investigate the influence of high temperature treatments on smaller size MPs during anaerobic processes.

Influence of High-Temperature Treatment on Strength and Failure Behaviors of a Quartz-Rich Sandstone under True Triaxial Condition

Abstract In this paper, the effect of high temperature on the mechanical properties of quartz-rich sandstone was studied by true triaxial pressure experiment. The density, P-wave velocity, elastic modulus, peak stress, peak strain, and failure mode of quartz-rich sandstone before and after heat treatment were analyzed and compared. It was found that the color of quartz-rich sandstone changes greatly when heated to 500°C. In detail, the brittleness of quartz-rich sandstone gradually decreased and the ductility increased at high temperature. Although the density, P-wave velocity, and elastic modulus fluctuate, they showed a decreasing trend as a whole. In addition, the peak stress and peak strain showed an overall upward trend with the increase of temperature, and 500°C was the high-temperature failure threshold of quartz-rich sandstone. The failure mode of quartz-rich sandstone at high temperature changes from shear failure to shear-tension combined failure, and the number of cracks increases. Therefore, these research results can provide a certain reference for high-temperature underground operation.

Loss of immobilized water and intense protein aggregation responsible for quality deterioration of ready to eat firm tofu.

The influence of high-temperature treatment (100-120°C, 15 min) on the texture, color, and water-holding capacity of tofu gels was investigated. As the temperature increasing, the hardness and chewiness as well as the values of redness a and yellowness b increased gradually, while the water content and the lightness L value reduced progressively, and these variations were more pronounced at 115 or 120°C. Low field nuclear magnetic resonance showed that the loss of T22 water led to the decrease of the water content. Scanning electron microscope revealed that the micropore in gels decreased after heating, and almost entirely disappeared at 120°C. Further analysis by SDS-PAGE indicated the soy protein aggregation formed via disulfide linkage was observed in the thermal treated tofu gels, and nondisulfide linkage might also be occurred as temperature reached 110°C or higher. The quality deterioration may be attributed to immobilized water loss combined with the protein aggregation.

High Temperature Treatment of Castings from Steel Grade 150KhNM

High-temperature processing of steel cast is an effective way to obtain a high range of properties of finish product. The main purpose of the study was to determine the critical temperatures and modes of processing of molten steel 150KhNM. The thermal calculation was carried out according to the additivity rule. The holding time of the melt was determined experimentally. Laboratory melts were performed with varying temperatures of maximum heating of the melt above and below tcr. The optimal modes of high-temperature processing of the melt were determined by analyzing the structure of solid samples. The influence of high-temperature treatment on the structure and properties of castings from steel grade 150KhNM has been studied. The main processing parameters of this alloy have been determined. The dependences of the metal overheating influence on the castings mechanical properties improvement are obtained. Examples of improving the quality of products with using optimal modes of high-temperature processing are given. The investigated modes have showed that holding at a critical temperature leads to change in the type of casting-box (raw sand, dry sand, chill mold) and uniformity of distribution. This fact leads to a change in properties and a more homogeneous structure is formed.

The influence of high temperature treatment on morphology and performance of superfine glass fiber felts

This article presents an investigation on effects of heat treatments in the range 400–700℃ on morphology, fractal dimension, pore size distribution, and air permeability of superfine glass fiber felts. During the heat treatments, the released residual stress, thermal decomposition, and thermal contraction make fibers bend to different degrees, corresponding with different fractal dimensions. The felt pores are formed by the random interlacing of fibers, varying with the different bending degree of fibers, which results in an influence on the air permeability of the felt. The results show that there was no visible change in the morphology of the heated felt at 400–550℃. However, the treatment at 600℃ could cause the breakage of some fibers, and above 650℃ the damage of felts. The fractal dimension of heated felt decreased at 400 and 450℃, but then increased above 500℃. The lowest fractal dimension was 1.8827 at 450℃, and the highest was 1.9666 at 600℃. Besides, the pores tend to distribute in a smaller size and a narrower scale under high temperatures, resulting in a decrease in the air permeability. However, the air permeability had the same variation trend with fractal dimension at 400 and 450℃, but opposite above 500℃. The relationship among them was verified by comparing the experimental and theoretical results. At 600℃, the mean pore size and the air permeability reduced by 16% and 31%, respectively.

Influence of annealing on the chemical composition of nanocomposites with the ferromagnetic grains in the CaF2 dielectric matrix

In the paper the content of individual elements (Fe, Co, Zr, Ca and F) contained in nanocomposites FeCoZr ferromagnetic alloy in the CaF2 transparent ceramics dielectric matrix, depending on the content of the metal phase x was determined by the X-ray diffusion microanalysis (EDX) method. The nanocomposites were made by sputtering by argon ions. Investigations of changes in the chemical composition of nanocomposites under the influence of high-temperature treatments were carried out using the thermogravimetry method in the temperature range from 25 °C to 1000 °C with a temperature increase rate of 10 °C/min. On the basis of the research, a model of changes of the structural-phase state of nanogranular layers of ferromagnetic alloy Fe45Co45Zr10 in the transparent ceramics CaF2 matrix occurring under the influence of high-temperature treatments was proposed.

Effect of Titanium Depletion of High Temperature Treated NiTi Shape Memory Alloy Wire

Shape memory behaviour of NiTi is very sensitive to the presence of inclusion in the matrix and oxide and the surface. This work studied the influence of high temperature treatment towards thermal martensitic transformation behaviour of NiTi. The alloy was subjected to heat treatment at 1223 K for various times in argon and air environment. It was found that treatment in air severely destroyed the shape memory property of the alloy due to the formation of multilayer of oxides. Treatment in argon also reduced the volume percentage of martensite phase transformation, even though no oxide layer was observed at the surface. This reduction is caused by the depletion of Ti element in the matrix due to the outward diffusion of Ti element. The outward diffusion of Ti is however stabilized at 15 hours exposure time of 1223 K heating temperature.

Influence of high-temperature treatment on the pore structure of carbon reducing agents

The influence of heat treatment (up to 1700°C) of coke and semicoke on their porous structure and properties is investigated. The micro- and macroporous structure of the reducing agents is studied by sorptional analysis and mercury porometry. High temperatures result in compaction of the coke’s fine-pore structure. For semicoke, the change in the macroporous structure may take various forms. These factors must be taken into account when using coke and semicoke as reducing agents.

TEMPERATURE STRESS AND SEEDS DORMANCY OF VEGETABLE UMBELLIFERAE CROPS. FEATURES OF INTRODUCTION, EXPRESSION, AND OVERCOMING (SECOND PART)

The influence of high temperature treatment of the seeds of vegetable Umbelliferae crops was studied. Features of seed germination and embryo development depending on incubation time were revealed. High-temperature treatment of seeds during 5 and 20 days inhibits the embryo development and seed germination.

Effect of Structure on the Mechanical Properties of PAN-Based Carbon Fibers during Graphitization

An investigation was conducted to determine the influence of high temperature treatment from 1600°C to 2800°C under stretching stress of 10MPa on PAN-based carbon fiber structure and physical properties. The tensile strength of fibers decreased from 4.5GPa to 2.97GPa with increasing treatment temperature up to 2800°C，while the modulus of fibers increased from 230GPa to 375GPa The texture in the longitudinal surface of fibers through heat treatment was characterized using a scanning electron microscopy. The contours of fiber surface became accidented with gaps becoming deeper as temperature increased. It has been observed that both the crystallite sizes (La, Lc) and the degree of preferred orientation increasd, while the crystallite interlayer spacing (d002) decreased by X-ray diffraction analysis with increasing heat-treatment temperature. The total porosity of fibers decreased from 21.01% to 15.09% and while the density of fibers increased from 1.720g/cm-3 to1.886 g/cm-3 with increasing heat-treatment. In addition, the relationship between mechanical properties and structure of variants was also explored in detail.

Evidence for and mitigation of the encapsulation of gold nanoparticles within silica supports upon high-temperature treatment of Au/SiO 2 catalysts: Implication to catalyst deactivation

Silica is one of the most widely used catalyst supports for metal nanocatalysts. Although the sintering of metal nanoparticles on various silica supports has been extensively studied, the restructuring of silica supports and its effect on supported metal nanoparticles have been seldom investigated. In this paper, silica-supported gold catalysts were used as a model system to probe the interplay of silica supports and metal nanoparticles under high-temperature treatment conditions. Gold was loaded onto mesoporous SiO 2 (SBA-15) using Au(en) 2Cl 3 as the precursor in the presence of aqueous NaOH (pH ∼ 10). The influence of high-temperature treatment on the textural and structural changes of SBA-15 and Au/SBA-15 was studied by X-ray diffraction (XRD), N 2 adsorption–desorption, and transmission electron microscopy (TEM). Control experiments were conducted using an amorphous SiO 2 (Cab-O-Sil) as the support. It was found that SBA-15 undergoes significant phase transformation to crystalline cristobalite upon high-temperature treatment, resulting in the dramatic decrease in surface area. More interestingly, the crystallization of SiO 2 leads to the encapsulation of gold nanoparticles inside the SiO 2 matrix. This conclusion was proven by aqua regia leaching, EDX, and SEM/TEM experiments. Gold nanoparticles can also be encapsulated into the SiO 2 matrix when using Cab-O-Sil as the support, but the process takes place under much higher temperatures. The encapsulation of gold nanoparticles can be mitigated by coating Au/SBA-15 with amorphous Al 2O 3 or by coating SBA-15 with Al 2O 3 before loading gold. Our findings shed new light on the deactivation of supported gold catalysts under high-temperature conditions.

Influence of High Temperature Treatments on Fullerene Soot and Formation of Multi-shell Carbon Nanoparticles Filled with LaC2

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Influence of high temperature treatment of porous carbon on the electrochemical performance in supercapacitor

Mesoporous carbon (MoC), prepared by the template method from phenol resin, commercial mesoporous carbon fiber (ACF) and microporous activated carbon (MiC) were heat-treated under 1200 °C in nitrogen. The samples before and after high temperature heat treatment (HTT) were used as electrodes in 30% KOH electrolyte for supercapacitor. The structure and electrochemical properties of these samples were characterized by X-ray diffraction (XRD), galvanotactic charge–discharge, cyclic voltammetry (CV) and electrochemical impedance spectra, respectively. Results showed that HTT caused a remarkable increase of mesoporous ratio in texture accompanied with a significant reduction of surface area. After HTT, the layer–layer space among graphite crystallite decreased and the degree of graphitization was improved. The capacitance values of mesoporous carbons increased and a more stable tendency for specific capacitance was obtained compared with the contrary performance of MiC-1200. The cyclic voltammetry of the samples at different sweep rates was close to the rectangular shape, which represented the lower ESR and higher power density. It was also found that high temperature treatment could improve the electrical conductivity and decrease the impedance of the electrode remarkably. The improved specific capacitance and the better conductivity of mesoporous carbons could be ascribed to the expanding and reorganization of crystallite structure as well as increase of mesopore ratio.

Influence of high-temperature treatment of melt on the structure formation and wear resistance of white chrome iron

Influence of high-temperature treatment of melt on the structure formation and wear resistance of white chrome iron

Modification of styrene-containing polymer with pinane. Possible applications of the product

The influence of high-temperature treatment on the properties of a styrene-containing polymer prepared from by-products of polybutadiene production was studied. The use of the products in production of emulsion rubbers and for protecting treatment of wood materials was examined.

高温熱処理したシリカゲルおよび多孔質ガラスを吸着剤に用いたトリチウム水の濃縮

1100℃までの温度範囲で熱処理を行ったシリカゲル及び多孔質ガラスを吸着剤に用いて, トリチウム水の吸着濃縮を行った。トリチウム水は通常の水に比べ強く吸着していることがわかった。トリチウム分配係数は, 多孔質ガラスでは熱処理温度の上昇と共に低下する傾向が見られたのに対し, シリカゲルでは逆に, 900℃以上で急激に上昇し, 1100℃熱処理では1.38と高い値を示した。熱処理後のシリカゲルには孤立型シラノール基が形成されていることがわかった。孤立型シラノール基に吸着したヒドロキシル基あるいは水分子は互いに水素結合することが困難であるため, トリチウムの質量効果が大きく現れたものと推察された。