Effect Of High Temperature Heat Treatment Research Articles

Electrical resistivity of heat-treated charcoal

The aim of this investigation was to determine the effect of high-temperature heat treatment on the electrical resistivity of charcoal. Samples of two different wood types (eucalyptus and black wattle) were pyrolised in a retort at a temperature of 700°C and the resulting charcoals heat-treated in an induction furnace at temperatures from 800°C to 1800°C and residence times from 60 to 120 minutes. After cooling, the resistivities of the samples were measured at room temperature using the four-point probe technique. It was found that as the heat treatment temperature increased the electrical resistivity of the charcoal decreased, approaching an asymptotic value at higher temperatures. Longer residence times decreased the resistivity, but this effect was not pronounced.

Improved Soft Magnetic Properties in FeNi@MgO Composites by Sol-Gel-Based Surface Coating and High-Temperature Heat Treatment

In this study, we utilized MgO as an insulating buffer layer to enhance the thermal stability and soft magnetic properties of Fe-Ni soft magnetic composites (SMCs) and investigated the effect of high-temperature heat treatment on those soft magnetic properties. By employing the sol-gel process, a uniform MgO insulating layer with a thickness of 600 nm was coated onto Fe-Ni magnetic powder. Subsequently, high-density SMCs were fabricated through high-pressure compaction molding. The MgO layer remained intact up to 800 °C, leading to the FeNi@MgO@MK SMCs exhibiting enhanced permeability and reduced hysteresis loss due to grain enlargement and elimination of defects, such as dislocation stacking. Notably, the dynamic loss increase after high-temperature heat treatment was significantly regulated compared to the case of the uncoated counterpart. The results underscore the potential to improve the thermal stability and soft magnetic properties of MgO-coated Fe-Ni SMCs, rendering them suitable for various electromagnetic applications.

The effect of high-temperature heat treatment and homogenization on the microstructure of set yogurt curd networks.

Set yogurt's physical characteristics are greatly affected by the homogenization and heat treatment processes. In our previous study, set yogurt treated at 130°C and with the fat particle size reduced to ≤0.6 μm had equivalent curd strength, less syneresis and smoother texture than yogurt treated at 95°C. When investigating the mechanisms underlying yogurt's physical properties, it is important to evaluate the yogurt's microstructure. We conducted electron microscopy evaluations to investigate the mechanisms of changes in yogurt's physical properties caused by 130°C heat treatment and by a reduction in the fat globule size. We prepared yogurt mixtures by combining heat treatment at 95 and 130°C and homogenization pressure at 10 + 5 and 35 + 5 MPa and then fermented the mixtures in a common yogurt starter. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for the structural observations. Fine particles were observed on the surface of the casein micelles of the yogurt treated at 95°C, and the coalescence density between micelles was high. The surface of the yogurt treated at 130°C had few fine particles, and the coalescence density between micelles was low. The yogurt treated at 130°C with 35 + 5 MPa homogenization had low coalescence density between casein micelles, but smaller-particle-size fat globules increased the network density. Approximately 30% of the fat globules were estimated to be incorporated into the yogurt networks compared to the volume of casein micelles. We speculate that 130°C heat treatment alters the structure of whey protein on the surface of casein micelles and interferes with network formation, but reducing the size of fat globules reinforces the network as a pseudoprotein.

Effect of high-temperature heat treatment on electrochemical corrosion behavior of laser cladding Fe-based alloy coating in H2SO4 solution

Double-layer Fe-based alloy coatings were fabricated on the surface of ductile cast iron using high-speed laser cladding. The electrochemical corrosion behavior of the coatings in 0.5 mol/L H2SO4 solution was analyzed after heat treatment (HT) at 950 ℃ for 1, 2, and 3 h. The results show that many fine and dispersed particles were precipitated in dendrites after 1 and 2 h HT. The precipitates in the dendrites of the 3 h heat-treated aggregated, nucleated, and grew up, forming the blocky. At the same time, the intergranular part of the long-chain structure began to dissolve and break. The corrosion rate decreased significantly with the increase in HT time. The specimen had the most-nobel self-corrosion potential (−0.15 V) and the best corrosion resistance after 3 h HT.

Thermally activated plastic deformation of Si single crystals at temperatures above 1173 K

The effect of high-temperature heat treatment during production on the mechanical property of Si wafer, namely yield stress, was studied through tensile tests of Si single crystals at 1123–1373 K, where stress–strain curves were obtained along the and directions. The critical resolved shear stress showed a remarkable temperature dependence, and it decreased with increasing test temperature. Below 1348 K, the activation enthalpy determined through strain rate jump tests showed no significant difference between crystals made by the Chokralski and the floating zone methods. This indicated that the solute oxygen does not influence the thermally activated dislocation glides. The activation enthalpy of 4.9 eV for a dislocation glide was much higher than that reported by previous studies (2.2 eV at temperatures below 1100 K), indicating that the thermal activation of dislocation glide is different from kink-pair nucleation. It was found that self-diffusion can assist the dislocation glide at temperatures above 1130 K.

Formation of eutectic and hydrogen absorption/ desorption behavior of heat-treated Ti19Hf4V40Mn35Cr2 alloys

The effect of high-temperature heat treatment (1673 K, 1min/5min/30min, water quenching) on the microstructure and hydriding/dehydriding properties of Ti19Hf4V40Mn35Cr2 alloys was studied. Both the proportion and lattice contraction of BCC phases increased after heat treatment. The eutectic (BCC phase + C14 Laves phase) structure was formed under different heat treatment conditions. Ti19Hf4V40Mn35Cr2 treated at 293 K for 1 min had the highest hydrogen storage capacity (2.23 wt%) and the fastest absorption rate. This was because of the easy and fast diffusion of H atoms. The dehydriding enthalpy (ΔH) of the as-cast alloys was 41.70 kJ/mol H2, which was higher than 33.62 kJ/mol H2 of heat-treated alloys. The reason was the decrease in hydride stability.

Effect of High-Temperature Heat Treatment on Strengthening Mechanism of AlCoCrFeNi Component Fabricated by LMD

In the present study; an AlCoCrFeNi high-entropy alloy (HEA) component was produced by laser melting deposition (LMD) technique. Then; a heat-treatment process based on the detection results of Differential Scanning Calorimeter (DSC) was used. The effects of heat treatment on the phase transition; microstructure and mechanical properties of the AlCoCrFeNi component were systematically studied. The results showed that low-temperature heat treatment (600 °C) had little effect on the microstructure and mechanical properties of component. The 800 °C heat treatment precipitated σ and face-center cubic (FCC) phases near grain boundaries in the component. The high dislocation capacity of FCC phase and precipitation strengthening of σ phase improved the strength and plasticity of this component. However; hard and brittle σ phase was not conducive to uniform distribution of microhardness. High-temperature heat treatment (1000 °C) caused the σ phase to remelt and increased FCC phase content at grain boundaries; resulting in a significant increase in strength and plasticity. Although the microhardness of the AlCoCrFeNi component after this heat treatment was reduced; the good strength and plasticity will facilitate its application in the structural field.

Effect of high-temperature heat treatment on microstructure and properties of FeMnCrNiCo + 20 wt.%TiC high-entropy alloy coating

Effect of high-temperature heat treatment on microstructure and properties of FeMnCrNiCo + 20 wt.%TiC high-entropy alloy coating

Effect of high-temperature heat treatment on the microstructure and mechanical behavior of PIP-based C/C-SiC composites with SiC filler

C/C-SiC composites were fabricated by a combined process of chemical vapor deposition (CVD), slurry infiltration(SI), and precursor infiltration and pyrolysis (PIP). The microstructure and mechanical behavior were investigated for the dense C/C-SiC composites before and after high-temperature heat treatment. The results indicated that the sintering of the SiC matrix and the migration of the SiC matrix/fiber bundles weak interface occurred after high-temperature heat treatment at 1900 ℃. The SiC sintering resulted in an increase in the flexural strength of the C/C-SiC composites from 298.9 ± 35.0 MPa to 411.1 ± 57.3 MPa. The migration of the weak interface changed the direction of crack propagation, making the fracture toughness of the C/C-SiC composites decrease from 13.3 ± 1.7 MPa⋅m 1/2 to 9.02 ± 1.5 MPa⋅m 1/2.

Study on the Effect of High-Temperature Heat Treatment on the Microscopic Pore Structure and Mechanical Properties of Tight Sandstone

The investigation of changes in physical properties, mechanical properties, and microscopic pore structure characteristics of tight sandstone after high-temperature heat treatment provides a theoretical basis for plugging removal and stimulation techniques, such as high energy gas fracturing and explosive fracturing. In this study, core samples, taken from tight sandstone reservoirs of the Yanchang Formation in the Ordos Basin, were first heated to different temperatures (25-800°C) and then cooled separately by two distinct cooling methods—synthetic formation water cooling and natural cooling. The variations of wave velocity, permeability, tensile strength, uniaxial compressive strength, and microscopic pore structure of the core samples were analyzed. Experimental results demonstrate that, with the rise of heat treatment temperature, the wave velocity and tensile strength of tight sandstone decrease nonlinearly, yet its permeability increases nonlinearly. The tight sandstone’s peak strength and elastic modulus exhibit a trend of the first climbing and then declining sharply with increasing temperature. After being treated by heat at different temperatures, the number of small pores varies little, but the number of large pores increases obviously. Compared to natural cooling, the values of physical and mechanical properties of core samples treated by synthetic formation water cooling are apparently smaller, whereas the size and number of pores are greater. It can be explained that water cooling brings about a dramatic reduction of tight sandstone’s surface temperature, generating additional thermal stress and intensifying internal damage to the core. For different cooling methods, the higher the core temperature before cooling, the greater the thermal stress and the degree of damage caused during the cooling process. By taking into consideration of changes in physical properties, mechanical properties, and microscopic pore structure characteristics, the threshold temperature of tight sandstone is estimated in the range of 400-600°C.

Fast-cure ionogel electrolytes with improved ion transport kinetics at room temperature

Fast-cure 1-ethyl-3-methylimidazolium trifluoromethanesulfonate-based ionogels have been realised for the first time. The influence of curing temperature on the structure of ionogels and their performance as the electrolyte for electric double-layer capacitors (EDLCs) has been investigated. Hybrid ionogels were synthesised via a non-hydrolytic sol-gel route and were fully gelled post heat-treating at 125, 150, 175 and 200 °C for 60 min with minimal shrinkage. Charge-transfer resistance (a rate-limiting parameter in cell kinetics during charge/discharge cycles) was reduced by ∼80% by increasing the heat-treatment temperature; this was partially attributed to the interlocking effect facilitated by high curing temperature. We report a maximum areal capacitance of 95 mF cm−2. Due to ∼40% increase in the penetrability coefficient of the ionic liquid, the electrode 'full' wetting time dropped from 48 to 5 h when the curing temperature was increased above 150 °C. These results were supported by SEM and Raman spectroscopy to characterise the effect of high temperature heat-treatment on the electrode-ionogel interface and the degree of electrode wetting by the ionic liquid. The fast-cure fabrication process for ionogels removes one of the major hurdles in their industrial application while the improved room temperature ion transport kinetics expands the potential application of ionic liquid-based electrochemical systems.

Effects of high-temperature heat treatment on the microstructure and mechanical performance of hybrid Cf-SiCf-(Al2O3p) reinforced geopolymer composites

Abstract Hybrid C f and SiC f reinforced geopolymer composites with Al 2 O 3 particles were successfully fabricated, and the effects of high-temperature treatment on the microstructure evolution and mechanical properties of C f -SiC f -(Al 2 O 3p )/KGP composites were investigated. Results showed that the amorphous matrix of C f -SiC f -(Al 2 O 3p )/KGP composites transformed into kalsilite and leucite phase after treated at 1000 and 1200 °C, respectively, due to the addition of fibers hindering crystallization of the geopolymer matrix. The addition of Al 2 O 3p was helpful to increase the thermal stability of composites after high-temperature treatment. Flexural strength and Young's modulus of the composites decreased after high temperature treatment and showed the maximum values at 1000 °C. All the composites showed a non-catastrophic fracture behavior after heat treated, which was attributed to fiber pulling-out and debonding.

Effect of high-temperature heat treatment duration on the purity and microstructure of MWCNTs

The effect of high-temperature heat treatment on purity and structural changes of multiwalled carbon nanotubes (MWCNTs) were studied by subjecting the raw MWCNTs (pristine MWCNTs) to 2600∘C for 60 and 120 min. Thermogravimetric analysis (TGA), X-ray diffraction, Raman spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to study the effect of heat-treatment duration on the purity and structural changes of MWCNTs. Results show that high-temperature heat treatment can be used to purify MWCNTs with proper optimization of treatment time. It was observed that 60 min heat treatment of raw MWCNTs imparts high purity and structural perfection to MWCNTs, while 120 min heat treatment imparts structural degradation to MWCNTs with collapse of the innermost shells. The present study indicates that metal impurities act as moderators in controlling the degradation of MWCNTs up to certain duration, and once the metal impurities escape completely, further heat treatment degrades the structure of MWCNTs.

Effect of High-Temperature Heat Treatment on Mechanical Property of Cr-Geopolymer Composite

Chromium powder reinforced geopolymer composite (Cr/geopolymer) was prepared in order to enhance its thermal conductivity and mechanical properties. The phase composition, microstructure and mechanical properties of Cr/geopolymer before and after heat treatment at 900, 1000, 1100 and 1200°C were investigated by the X–ray diffraction (XRD), scanning electron microscopy (SEM) and three–point bending test. With increasing heat treatment temperature from 900 to 1100°C, mechanical property of Cr/geopolymer increased gradually and at 1100°C flexural strength got the peak value, which was 325% higher than that of specimens without heat treatment. Cr/geopolymer treated at 900°C did not completely transform into crystalline phase, and many micro cracks around the chromium particles were observed. Cr/geopolymer treated at 1000–1100°C completely crystallized into leucite phase, and the metal chromium remained its original state. Meanwhile, most of the micro cracks were closed. When the temperature further increased to 1200°C, many visible defects were observed in Cr/geopolymer, and chromium oxide appeared in the interface of Cr/geopolymer, which had detrimental effect on the heat conduction and mechanical property of the composite.

The effect of high-temperature heat-treatment on the strength of C/C–SiC joints

Joining of carbon fiber reinforced C–SiC dual matrix composite (denoted by C/C–SiC) is critical for its aeronautical and astronautical applications. Joining of C/C–SiC has been realized through a reaction joining process using boron-modified phenolic resin with micro-size B4C and nano-size SiO2 powder additives. The effect of the heat-treatment temperature on the retained strength of the joints, calculated by dividing the strength of the heat-treated joints by the strength of the joints before heat-treatment, was studied. The maximum retained strength of the joints is as high as 96.0% after the heat-treatment at 1200 °C for 30 min in vacuum, indicating good heat resistance of the joints. The thickness of the interlayer of the joint after the heat-treatment is about 18 μm and it is uniform and densified. There are no obvious cracks or pores at the interfaces. During the heat-treatment, carbon, oxygen, silicon, and boron diffuse at the interfacial area. The interlayer is composed of B4C, SiO2, glassy carbon, amorphous B2O3, and borosilicate glass. SiC appears in the interlayer of the joint heat-treated at 1400 °C for 30 min in vacuum. The addition of B4C and SiO2 powders contributes to the densification of the interlayer, the bonding at the interfaces and the heat resistance of the joints.

The effect of high temperature heat-treatment on the strength of C/C to C/C–SiC joints

Joining of carbon fiber reinforced carbon matrix composite to a carbon fiber reinforced C–SiC dual matrix composite has been realized through a reaction joining process using boron-modified phenolic resin with micro-size B 4C and nano-size SiO 2 powder additives. The effect of the heat-treatment temperature on the retained strength of the joints, calculated by dividing the strength of the heat-treated joints by the strength of the joints before heat-treatment, was studied. The maximum retained strength of the joints is 91.9% after heat-treatment at 1200 °C for 30 min in vacuum, indicating good heat-resistance of the joints. The interlayer with a thickness of about 25 μm is uniform and densified. There are no obvious cracks or pores at the interfaces. The interlayer is composed of B 4C, SiO 2, glassy carbon, B 2O 3 and borosilicate glass. Si diffuses from the interlayer into the substrates and reacts with carbon to form SiC. Both B and O migrate from the interlayer into the substrates, contributing to the interfacial bonding. The B 4C and the SiO 2 powder additives contribute to the densification of the interlayer, the bonding at the interfaces and the heat-resistance of the joints.

Effects of high-temperature heat treatment on the mechanical properties of unidirectional carbon fiber reinforced geopolymer composites

Abstract Unidirectional carbon fiber reinforced geopolymer composite (C uf /geopolymer) is prepared by a simple ultrasonic-assisted slurry infiltration method, and then heat treated at elevated temperatures. Effects of high-temperature heat treatment on the microstructure and mechanical properties of the composites are studied. Mechanical properties and fracture behavior are correlated with their microstructure evolution including fiber/matrix interface change. When the composites are heat treated in a temperature range from 1100 to 1300 °C, it is found that mechanical properties can be greatly improved. For the composite heat treated at 1100 °C, flexural strength, work of fracture and Young's modulus reach their highest values increasing by 76%, 15% and 75%, respectively, relative to their original state before heat treatment. The property improvement can be attributed to the densified and crystallized matrix, and the enhanced fiber/matrix interface bonding based on the fine-integrity of carbon fibers. In contrast, for composite heat treated at 1400 °C, the mechanical properties lower substantially and it tends to fracture in a very brittle manner owing to the seriously degraded carbon fibers together with matrix melting and crystal phases dissolve.

Pre-treatment methods of Edam cheese milk. Effect on cheese yield and quality

The effect of high-temperature heat treatment (HH), microfiltration (MF) and ultrafiltration (UF) on the Edam vat milk composition, processing and cheese yield, ripening and functional characteristics were studied. The protein level of the MF and UF cheese milk was adjusted to 42 g/kg, whereas the level in the reference (REF) and HH milk was 34 g/kg. The cheese yield from ultrafiltration and microfiltration milk (CY v) was 12.8 g/100 g milk, yield from reference and high-temperature heat treatment milk was 10.1 and 10.2 g/100 g milk, respectively. The adjusted cheese yield (ACY r), calculated from raw milk, was lowest when MF was used. The pre-concentration method had little effect on the starter activity: no differences were observed in the pH of cheeses. The compositions of the ripened cheeses were comparable. The casein to fat ratio of MF cheese was elevated, possibly due to elevated casein to fat ratio of vat milk. Even though the high-temperature heat treatment, ultrafiltration and microfiltration cheeses were harder than reference cheese, they retained their elasticity. Resilience was significantly higher with microfiltration and ultrafiltration cheeses. The sensory quality of all cheeses was considered according to specification. The pre-treatment methods had little effect on the processing characteristics, cheese quality or yield when calculated on the basis of the quantity of original milk.

Effects of high-temperature heat treatment of oat kernel on viscosity properties of oat flour.

Effects of high-temperature heat treatment of oat kernel on viscosity properties of oat flour.

Effect of high-temperature heat treatment on the generation and annealing of radiation-induced defects in n-type silicon crystals

Defect formation and annealing processes in n-type silicon crystals heat-treated at temperatures from 550 to 1000°C for a short time and then gamma-irradiated in a 60Co source or electron-irradiated (E = 4 MeV) at room temperature have been studied using Hall effect measurements. The results demonstrate that the preheat treatment (PHT) has an insignificant effect on the energy spectrum and generation efficiency of major defect species. At the same time, PHT results in enhanced annealing of radiation-induced defects, accompanied by the formation of additional electrically active centers. PHT is assumed to activate transition-metal impurities (fast diffusers in silicon), which then interact with radiation-induced defects.