Effect Of High-temperature Treatment Research Articles

Influence of heat treatment on the structure and mechanical properties of zirconium dioxide crystals partially stabilized by samarium oxide

The effect of high-temperature treatment in different media on the phase composition, microhardness and fracture toughness of (ZrO2)1-х(Sm2O3)х crystals with x = 0.02÷0.06 has been studied. The crystals have been grown using direction melt crystallization in a cold skull. The crystals have been heat treated at 1600 °C for 2 h in air and in vacuum. The phase composition of the crystals has been studied using X-ray diffraction and Raman scattering. We show that samarium cations enter the ZrO2 lattice mainly in a trivalent charge state and do not change their charge after air or vacuum annealing. The as-annealed phase composition has changed in all the test crystals except for the (ZrO2)0.94(Sm2O3)0.06 composition. After air or vacuum annealing the (ZrO2)1-x(Sm2O3)x crystals with 0.002 ≤ x ≤ 0.05 contain a monoclinic phase. The (ZrO2)0.94(Sm2O3)0.06 crystals contain two tetragonal phases (t and t´) with different tetragonality degrees. After air or vacuum annealing of the (ZrO2)0.94(Sm2O3)0.06 crystals the lattice parameters of the t and t´ phases change in opposite manners, suggesting that the tetragonality degree of the t phase increases whereas the tetragonality degree of the t´ phase decreases. The microhardness and fracture toughness of the as-annealed crystals depend on the Sm2O3 concentration in the solid solutions. The formation of the monoclinic phase in the (ZrO2)1-х(Sm2O3)х crystals with 0.037 ≤ x ≤ 0.05 significantly reduces the microhardness and fracture toughness of the crystals. Annealing of the (ZrO2)0.94(Sm2O3)0.06 crystals triggers more efficient hardening mechanisms and thus increases the fracture toughness of the crystals. We show that air or vacuum annealing of the (ZrO2)0.94(Sm2O3)0.06 crystals increases the fracture toughness of the crystals by 1.5 times as compared with that of the as-grown crystals.

Effect of high-temperature treatment on water vapour sorption of montmorillonite

The changes and associated mechanisms in water vapour sorption of montmorillonite after high temperature treatment remain unclear. Here, we hypothesize that water vapour sorption behaviors of montmorillonites treated at high temperatures (>200 ℃) are different from that of untreated montmorillonite. Thus, the objective of this study is to investigate the effect of high temperature treatment on water vapour sorption of montmorillonite. Two successive adsorption/desorption isotherms and the physicochemical properties of pristine montmorillonite (CK) and the montmorillonites treated at 200 ℃, 350 ℃, 500 ℃ and 800 ℃ (marked as M200, M350, M500, and M800) were determined. The first and second water vapour adsorption/desorption isotherms of CK and M200 exhibited a type II, and that of M800 exhibited a type III. For the M350 and M500, the first adsorption isotherms showed a type III, but the first desorption and second adsorption/desorption isotherms showed a type II. The high-temperature heating decreased the water content change (WCC) in the water activity (aw) range from 0.05 to 0.2 (WCC0.05-0.2), and the degree of decrease became larger with increasing heating temperature. For the M350 and M500, the decrease in WCC0.05-0.2 during the first adsorption was greater than that at the second adsorption. Comparing with the CK, the treatments of 200 °C and 350 °C increased the WCC0.2-0.6 during the first adsorption by 33.0% and 28.1%, respectively, and increased the WCC0.6-0.93 during the first adsorption by 17.3% and 31.3%, respectively, but had little effect on the WCC0.2-0.6 and WCC0.6-0.93 values during the first desorption and second adsorption/desorption. Except for the increase in WCC0.6-0.93 during the first adsorption for M500, the WCC0.2-0.6 and WCC0.6-0.93 of M500 and M800 was decreased during the two successive adsorption/desorption processes.

Effect of High Temperature Treatment on the Photoluminescence of InGaN Multiple Quantum Wells

In this work, the photoluminescence (PL) properties of three as-grown InGaN/GaN multiple quantum well (MQW) structures which are heat-treated under different temperatures with nitrogen (N2) atmosphere are investigated. Temperature-dependent photoluminescence (PL) analysis was used to characterize the depth of localized states and defect density formed in MQWs. By fitting the positions of luminescence peaks with an LSE model, we find that deeper localized states are formed in the MQWs after high-temperature treatment. The experimental results show that the luminescence intensity of the sample heat-treated at 880 °C is significantly improved, which may be due to the shielding effect of In clusters on defects. While the luminescence efficiency decreases because of the higher defect density caused by the decomposition of the InGaN QW layer when the sample is heat-treated at 1020 °C. Moreover, the atomic force microscope results show that the increase in heat-treatment temperature leads to an increase in the width of surface steps due to the rearrangement of surface atoms in a high-temperature environment.

Effect of high-temperature treatment on the desorption efficiency of gas in coalbed methane reservoirs: Implication for formation heat treatment

Formation heat treatment has been considered as a potential stimulation technology for the enhanced recovery of coalbed methane. However, the influence of heat treatment on the desorption efficiency of coalbed methane has not been clarified. In this study, isothermal adsorption experiments of a cylindrical anthracite coal treated at 25 °C, 200 °C, 400 °C, 600 °C, and 800 °C were conducted to investigate the variation in the methane adsorption potential and desorption efficiency. The pore structure of coal was characterized by nuclear magnetic resonance measurements and scanning electron microscopy. Changes in the organic matter and functional group content of coal were monitored by proximate analysis and Fourier transform infrared spectroscopy. Results reveal that pore structure and composition are the main factors that affect the coal adsorption potential. With the increase in the temperature to 200–600 °C, the maximum adsorption potential of coal increased by 7% due to the increase in the pore volume and the functional group content. At a heat-treatment temperature of 800 °C, the functional group content decreased, which in turn reduced the maximum adsorption potential by 76%. Comparison of isothermal adsorption data of coals with different ranks reveals that the Langmuir parameter of bituminous coals is more easily affected by heat treatment in comparison with that of anthracite coal. Based on the reversible theory of coalbed methane isothermal adsorption and desorption process, weighted pressure was proposed, which could comprehensively evaluate the desorption efficiency of coal after heat treatment at different temperatures, and the heat treatment temperature for the optimal desorption efficiency can be determined by the weighted pressure.

Effect of High-Temperature Treatment of Bronze Particles on the Characteristics of Coatings Formed by the Method of Cold Gas-Dynamic Spraying

Effect of High-Temperature Treatment of Bronze Particles on the Characteristics of Coatings Formed by the Method of Cold Gas-Dynamic Spraying

Effect of High-Temperature Treatment on the Properties of Carbon Nanotube-Based Petroleum Coke Composite

Effect of High-Temperature Treatment on the Properties of Carbon Nanotube-Based Petroleum Coke Composite

Investigation of hydrogen impurities in PE-ALD AlN thin films by IBA methods

Hydrogen impregnation is one of the main sources of contamination in AlN thin films obtained by atomic layer deposition method (ALD) as many studies report. Such impurities can be potentially detrimental to mechanical and electrical properties of the material. In this study methods belonging to ion-beam analysis (IBA) group, namely: elastic recoil detection analysis (ERDA), nuclear reaction analysis (NRA) and secondary-ion mass spectrometry (SIMS) were utilized to examine AlN thin films obtained by plasma-enhanced atomic layer deposition (PE-ALD) with use of trimethylaluminium (TMA) and N2+H2 gas mixture as precursors. Several depositions of AlN layers were carried out with different values of N2+H2 flux intensity (20, 100, 150 sccm) and TMA pulse (0.06, 0.12, 0.15 s) in order to investigate whether such alterations would produce any effect on the resulting films. Data obtained within the scope of this study suggest that AlN grown by PE-ALD exhibit rather low amounts of hydrogen impurities, especially when compared to thermal ALD. Furthermore, the effect of high-temperature treatment in N2 atmosphere was studied and was found out to produce a positive effect on the chemical composition of AlN films.

Effect of High-Temperature Treatment on the Structure and Mechanical Properties of a VKh4L-VI Alloy

Effect of High-Temperature Treatment on the Structure and Mechanical Properties of a VKh4L-VI Alloy

The effect of Sibunit graphitization on the stability of Ru/(Pt, Pd)/Sibunit catalysts in an oxidizing atmosphere at elevated temperatures

The effect of high-temperature treatment on the thermal stability of a graphitic carbon material Sibunit in an oxidizing medium was studied in dependence on the presence of active component – Pt, Pd or Ru. According to thermal analysis data, a high-temperature pretreatment of Sibunit increases the onset temperature of carbon oxidation. It was found that holding of the Ru/Sibunit samples for 4 h in a nitrogen: air (1 : 1) mixture at a temperature of 400 °С resulted in a partial destruction of the pyrocarbon matrix of Sibunit and increased the mean size of Ru particles. It was demonstrated that ruthenium catalysts can efficiently oxidize CO at a temperature not higher than 200 °С and withstand overheats up to 400 °С without a significant loss in activity.

Effect of High Temperature Treatment on the Photoluminescence of InGaN Multiple Quantum Wells

Effect of High Temperature Treatment on the Photoluminescence of InGaN Multiple Quantum Wells

Effect of High Temperature Treatment in Ar Atmosphere on the Tensile Strength and Structure of SiC Fiber

The properties and structure changes of SiC fiber in high temperature determine the service temperature of the reinforced ceramic matrix composites, so the properties of SiC fibers under high temperature are very important. The SiC-A and SiC-B fibers were treated at 1200, 1350 and 1600°C in Ar atmosphere. Then the tensile strength was measured, the microstructure and composition of the fibers were analyzed by SEM, EDS, XRD and AES. The results show that the tensile strength of SiC-A and SiC-B decrease slowly at 1200 and 1350°C, but decrease rapidly at 1600°C.

Regenerating Anode Materials from Scrapped Lithium-Ion Battery by High-Temperature Treatment

Regenerating anode materials from scrapped LIBs draws a significant role in utilizing spent graphite materials and protecting ecological environment. Heat treatment is an essential step in the regeneration process of spent anode. In this study, we focused on the effect of high-temperature treatment on graphite lattice structural reconstruction and electrochemical performance. Prior to heat treatment at different temperatures (e. g. 700, 900, 1100, 1300 and 1500 °C), spent graphite could be purified in sulfuric acid solution. Then, the structural analysis was performed by using XRD tests before and after regeneration, and the results show that when temperature reaches 900 °C, recovered graphite had already formed a good crystallinity. Additionally, the analysis of size distribution, surface area and pore diameter distribution were performed to characterize physical properties. The results showed that heat-treated graphite at 900 °C (HTT-900) displayed the optimal physical properties, which was close to that of commercial graphite. Furthermore, HTT-900 retained an outstanding initial specific capacity (358.1 mAh/g at 0.1 C) and a remarkable cycle stability (capacity retention of 98.8% after 100 cycles). Moreover, the reversible capacities of HTT-900 at 0.1-2.0 C and another 0.1 C reached up to 356.8, 340.1, 306.1, 242.6, 69.7 and 359.2 mAh/g, respectively.

Improved superconducting properties of multifilament internal Mg diffusion processed MgB2 wires by rapid thermal processing

6+1-filament MgB2 long wires with high critical current densities were fabricated using an internal Mg diffusion (IMD) process. The effect of high temperature treatment by conventional furnace annealing and rapid thermal processing on the superconducting properties and microstructure of IMD wire was investigated. The rapid thermal processing can improve the superconducting properties of multifilament internal Mg diffusion processed MgB2 wires obviously. A best layer Jc and Je as high as 2.8 × 105 A/cm2 and 3.1 × 104 A/cm2 at 4.2 K and 6 T were obtained by rapid thermal processing in the continuous heat treatment furnace. The Je is about 1.0 × 104 A/cm2 and 5.2 × 103 A/cm2 at 8 and 10 T, respectively. The engineering Je and MgB2 fill factor of MgB2 wires were improved obviously. Our obtained results show that the IMD wires with excellent superconductivity and mechanical property are suitable for practical applications.

Wort Boil Time and Trub Effects on Fermentability

The purpose of this research was to understand and evaluate the effect of high temperature treatment of wort at varying time periods (30, 45, 60, 90, and 120 min) on wort fermentability. The effect of trub was also analyzed. Small-scale fermentations were conducted using a malt (malted from AC Metcalfe) free of premature yeast flocculation tendencies and a standard SMA yeast strain. The turbidity and apparent extract were measured at specific time intervals. The decline in extract was modeled with the ASBC Yeast-14 logistic equation predicting a sigmoidal curve. Turbidity measurements were modeled with a “tilted Gaussian” fit. Heat-treating the wort (at 100 or 121.1 °C) resulted in a significant decline in ADF (p < 0.05). As denoted by the midpoint of the fermentation, all fermentation runs, with and without trub, at lower wort boil durations fermented faster than longer or higher wort-boiling treatments. The decline in wort fermentability was highest upon treatment at wort temperature and pressure levels of 121.1 °C and 3.0 atm. The amount of trub and the wort color formed after each heat treatment showed a gradual increase with heating duration. Free amino nitrogen levels of wort declined significantly with respect to both increase in wort boiling temperature and time intervals (p < 0.001).

Effect of high temperature treatment on the microstructure and elastoplastic properties of polyacrylonitrile-based carbon fibers

The effects of high temperature treatment (2000–2800 °C) on the microstructure evolution and elastoplastic properties of polyacrylonitrile-based carbon fibers were investigated. It is found that the uneven shrinkage of the carbon fiber surfaces leads to formation of bulges whose length-to-width ratios increase with increasing heat treatment temperature. Because of the shrinkage stress, a closely stacked and curved graphene layer can be found in the sub-surface region of the carbon fibers. In the longitudinal section, the continuity of the graphite-like ribbons in the sub-surface region is worse than that in the skin region and the cross-linking regions between the graphite-like ribbons still contain a lot of defects after heat treatments. As the indentation depth increases, the axial and transverse elastic modulus of the carbon fibers decrease, which are related to the needle-like pores and the ordered graphite-like crystallites. The improvement of the slip between the graphene layers and the breakage of the graphite-like crystallites and the cross-linking regions are responsible for the decrease in axial elastic modulus with increasing heat treatment temperature. By contrast, the transverse elastic modulus is low and the excellent elasticity in the transverse direction is due to the curved graphene layers and the needle-like pores.

Effect of high temperature treatment of Hevea brasiliensis on density, strength properties and resistance to fungal decay

Plantation grown Hevea brasiliensis (rubberwood)—a tropical wood species of low natural durability was thermally processed at four temperatures in the range of 150–240 °C for different durations under vacuum. Effect of heat treatments on various important physical and mechanical properties such as weight loss, density, flexural strength (modulus of rupture—MOR), stiffness (modulus of elasticity—MOE), compressive strengths and surface hardness as well as decay resistance were evaluated and compared with untreated wood. The weight loss due to heat treatments was found to be in the range of 1.0–14.6%. Density and flexural MOR were found to decrease with increasing temperature (up to 210 °C), while flexural MOE, compressive strengths and hardness were not much affected. Higher treatment temperatures (210–240 °C) were observed to have deleterious effect on the mechanical strength of wood. Heat treated rubberwood showed excellent durability against brown rot (Polyporus meliae) and white rot (Coriolus versicolor) fungi as evidenced by lower amount of weight loss of exposed samples. The decay resistance was found to increase with severity of treatments. Based on improved durability and moderate variations in mechanical properties due to relatively mild heat treatments (180–210 °C), thermally modified rubberwood is found to be suitable for certain nonstructural applications. Moreover, heat-treated rubberwood may also be considered as an ecological alternative to chemically impregnated wood which offers many potential and attractive opportunities to the timber processing and product industry for commercial market.

Effect of high‐temperature treatment on the mechanical and thermal properties of phenolic syntactic foams

Phenolic syntactic foams were prepared with phenol–formaldehyde resin (PF), p‐toluene sulfonic acid, γ‐aminopropyltriethoxysilane (APTES), and glutaraldehyde (GA) cooperative treated hollow glass microsphere (HGM). Five types of syntactic foams were fabricated by filling different content of modified HGM. Compressive, flexural and thermal properties of the foams were investigated with respect to HGM content and treated temperature. Thermogravimetric analysis (TGA) studies presented a considerable reduction in the weight loss rate of system with the addition of HGM, the residual weight of syntactic foam with 50 vol% HGM at 800°C is 72.45%. Compression and bending tests results showed an increase on compressive and flexural properties for syntactic foams treated at high temperature with increasing HGM volume fraction. The thermal conductivity of all syntactic foams increased with temperature while decreased with introducing HGM, and thermal conduction through solid phase was the main heat transfer approach. The incorporation of HGM was beneficial to improving the thermal insulation property of syntactic foams especially at high temperatures. POLYM. ENG. SCI., 58:2200–2209, 2018. © 2018 Society of Plastics Engineers

The effect of high-temperature treatment on the formation of nanoscale intermetallic compounds of transition metals in Al–Cu–Mn–Zr alloy

The precipitation of intermetallic compounds of transition metals during aging of the Al–5.8%Cu–0.3%Mn–0.1%Zr alloy has been studied using DSC, resistometry, X-ray and transmission electron microscopy. In these age hardenable alloys, the nanoscale metastable Θ″ and Θ′ phases of the Al2Cu compound are the main strengthening phases, which are formed at low temperature aging of T < 300 °C. The effect of high-temperature treatment (homogenization, heating for quenching, heating for the elimination of internal stresses, etc.) on the aging with the precipitation of strengthening phases has been investigated.

Increasing the Luminescence Yield of Zirconia

The effect of high-temperature treatment in vacuum in the presence of carbon as a reducing agent on the luminescent properties of zirconia is studied. It is shown that an increase in the intensity of pulsed cathodoluminescence at 480 nm and thermoluminescence in the dominant peak at 500 K is due to the thermochemical coloration of the initial samples with the formation of oxygen vacancies detected by electron paramagnetic resonance. The described procedure for increasing the luminescence yield of ZrO2 can be applied when it is used in optoelectronics, photonics, and radiation dosimetry.

The effect of high-temperature annealing on the stability of the structure and properties of welded joints in tungsten single crystals with planar and axial geometry

The results of experimental studies of the effect of high-temperature treatment on the stability of the substructure, crystallography and mechanical properties of welded joints in tungsten single crystals with planar and axial geometry are presented. The main task of the study was to obtain data on the possibility of producing monohedral tubes of tungsten single crystals with a stable structure (ρ = 105–106 cm−2), with permissible misorientation angles at the sub-boundaries (θ < 3°) in the central part of the welded joint and strength characteristics (σbend of the weld metal should be higher than or equal to σbend of the parent metal), suitable for service of these components at working temperatures (up to 2500 °C). The methods for producing pipes with the required homogeneous orientation of the side (working) surface made of a single crystal tungsten ingot are described.