Increasing Treatment Temperature Research Articles

Effects of oil heat treatment on poplar wood properties: A pilot scale study

Pilot-scale oil heat treatment was conducted to enhance the quality of poplar wood obtained from a fast-growing plantation. Three target temperatures, namely 180, 190, and 200 ˚C, were chosen for the oil heat treatment process. Clear, small specimens were cut from the lumber, following the prescribed standards for assessing wood quality. Light microscopy revealed the ruptures and deformation of the wood cell wall as the treatment temperature increased. The volumetric swelling of the treated specimen decreased proportionally with the increase in treatment temperature. The impact of oil heat treatment on the mechanical properties of wood varied depending on the specific type of mechanical strength and processing temperature. The modulus of rupture, toughness, and hardness of the treated specimens drastically decreased at 200°C. However, the specimens treated at 200°C exhibited much lower mass loss during the fungal decay test. The results of the analytical test showed an increase in the crystalline cellulose content and thermal stability of the treated wood, due to the thermal degradation of hemicelluloses and amorphous regions of cellulose. Overall, it is concluded that oil heat treatment of poplar wood in the optimal temperature is an efficient approach to upgrade its quality with minimal reduction in mechanical strength.

Effect of heat treatment on interface failure behavior in SiCf/PyC/SiC composites reinforced with Cansas-3 fibers

The influence of heat treatment on the correlation between interfacial mechanical properties and microstructure in CVI-SiCf/PyC/SiC composites was systematically investigated. The results reveal a progressive reduction in the average interfacial bond strength, interfacial shear stress, and interfacial debonding energy within the composites as the heat treatment temperature increases, especially beyond 1350 °C. This decline can be attributed to the attenuation of the SiCf/PyC interfacial bond strength arising from the contraction in fiber volume induced by the precipitation of Cansas-3 fibers. After push-in testing, SiCf/PyC/SiC composites heat-treated at or below 1350 °C displayed fibers in a compressed state. Conversely, composites exposed to extended heat treatment at 1400 °C or higher maintained fibers in an ejected state after push-in testing. Moreover, the composites heat-treated at 1450 °C and 1500 °C demonstrated fibers that were spontaneously ejected subsequent to cross-section polishing.

Phase transformation sequence of amorphous nickel-molybdenum electrodeposit

In this paper, the amorphous Ni-Mo alloy with cauliflower-like morphology is successfully prepared by electrodeposition, and the effects of heat treatment on its morphology, element content and structure are studied. The results of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Auger electron spectroscopy (AES) show that, when the temperature is higher than 600 ℃, the fine grains gradually appear and then cover the entire surface of Ni-Mo alloy. The Ni-Mo alloy occurs simultaneously the segregation phenomenon and the Mo content increases on the surface. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis illustrate that the Ni-Mo alloy gradually transfers from amorphous into crystalline structure, and the first phase MoNi4 and the second phase MoNi precipitate near 633℃ and 707℃ respectively. The apparent activation energy is 234.1 kJ/mol (ΔEa1) for the first phase crystallization and 819.9 kJ/mol (ΔEa2) for the second phase crystallization. The HER catalytic activity of Ni-Mo alloy increases first and then decreases with the increase of heat treatment temperature.

Effect of magnetic field on the apparent viscosity of water-in-oil waxy crude oil emulsion

The application of the magnetic field to reduce the apparent viscosity of water-in-oil waxy crude oil emulsions holds significant potential. A novel integrated magnetic processing apparatus was developed. The effects of magnetic treatment conditions on the viscosity of waxy crude oil and water-in-oil waxy crude oil emulsions with different water cuts were experimentally investigated. The viscosity reduction induced by the magnetic field was more pronounced for the emulsion with a higher water cut. The viscosity reduction degree of the emulsion first increased and then decreased with the increase in magnetic field intensity and magnetic treatment temperature. The viscosity reduction degree of the emulsion had a slight correlation with the magnetic treatment time and magnetic field frequency. Microscopic observation demonstrated that water droplet aggregation occurred in the magnetically treated emulsion compared to the untreated emulsion. Mechanism analysis shows that the oscillation of asphaltene molecules at the oil–water interface, the orientational arrangement of asphaltene molecules in crude oil, and the generation of monomeric water molecules induced by magnetic field contribute to the reduction in the apparent viscosity of waxy crude oil and the aggregation of water droplets. The viscosity of the emulsion is thus decreased. The research results provide a theoretical basis for the field application of viscosity reduction for water-in-oil waxy crude oil emulsion by magnetic treatment technology.

CALPHAD simulation and experimental study on heat treatment process of Al-Cu-Mn-Mg-Sc cast alloys

Because different heat treatment parameters have different effects on the microstructure and mechanical properties, it is necessary to optimize the heat treatment parameters to obtain alloys with better properties. In this study, the heat treatment parameters of Al-Cu-Mn-Mg-Sc cast alloys were optimized by using thermal simulation and experimental methods. The results show that the phase transformation temperature of the low melting point eutectic phase Al2Cu is 542.9 ℃, and the time for element homogenization distribution of the alloy during solid solution at 525 ℃, 535 ℃ and 550 ℃ is 8 h, 7 h and 4.5 h, respectively. With the rise of solid solution temperature, the microhardness increase at first and then decrease, and the microhardness reaches to 96.4 HV at 535 ℃. When solid solution heat treatment is carried out at 535 ℃ for different times, the microhardness increase at first and then decrease with time, and the microhardness reaches to 118.4 HV at 5 h. It is known that the number of metastable phase decreases gradually with the increase of aging heat treatment temperature by using the calculation of thermodynamic software. The optimal aging heat treatment process parameter for the alloy is 170 ℃ for 10 h, and the microhardness at this time reaches to 142.3 HV.

Analysis of the ceramic coatings' recrystallization produced on the surface of the Zr-25Ta-25Ti alloy

The objective of this study is to analyze the influence of the heat treatment temperature carried out at ultra-high vacuum on surfaces formed in the Zr-25Ta-25Ti alloy by the micro-arc oxidation (MAO) technique to produce a ceramic layer with high hardness and high wear resistance. The results of structural (XRD) and microstructural characterization (SEM, optical and confocal microscopy technique) show that the surfaces are mainly composed of zirconium dioxide (ZrO2), Ti2ZrO, and calcium oxide (CaO). The heat treatments at high temperatures (500–800 °C) altered the phases of the MAO coating, forming ZrC. Confocal images showed that increasing temperature increased the roughness of the coatings (0.65 → 1.06 μm). Consequently, the topography of the coatings, wettability, microhardness (Vickers), and wear resistance (obtained by the ball cratering technique) of the materials are also modified. The wear results show that the MAO coating has a low wear rate value due to the MAO surfaces’ high hardness, efficiently protecting the substrates of the Zr-25Ta-25Ti alloy against tribological phenomena. Finally, the increase in heat treatment temperature promoted the formation of cracks in the coatings due to the difference in thermal expansion of the MAO ceramic with the Zr-25Ta-25Ti alloy substrate, causing a decrease in the hardness value and reducing wear resistance.

Valence state conversion of Mn ions in Li2O–ZnO-GeO2 glass-ceramics: Spectral, structural, ESR and XRF studies

Lithium-zinc-germanate glass-ceramics doped with Mn ions are synthesized by volume crystallization method. Structural studies show nucleation of different forms of lithium germanate crystals depending on the isothermal treatment regime of the initial glass. With the increase of the heat treatment temperature and the lithium content in the initial glass, the [GeO4] /[GeO6] ratio in the nucleated crystalline phases increases. The initial distribution of Mn2+/Mn3+/Mn4+ is defined by the Li2O/ZnO ratio in the glass composition: the ratio growth increases the contribution of Mn4+ over the Mn2+ and Mn3+. Low-temperature heat treatment of initial glass leads to uprise of intense red emission of Mn4+ ions in the octahedral environment. High-temperature heat treatment leads to occurrence of intense green emission related to Mn2+ ions in a tetrahedral environment. Discussions on all transformations of symmetry, the crystal field strength of Mn ions’ environment and their valence state based on the results of optical spectroscopy, ESR and XRF studies are provided. The maximum quantum yield of red luminescence is 61%, and of green luminescence is 23%. The synthesized glass-ceramics can be used as a luminescent converter of the UV LED radiation with the maximum energy efficiency of 20%.

The performance and mechanism of HCHO oxidation on Pd/SiO2 catalysts with different Pd particle sizes

In general, for Pd-based catalysts, the smaller the Pd particles on the catalysts are, the better the activity for HCHO oxidation; this has solely been ascribed to the high Pd dispersion on the catalysts’ surface. However, the Pd site effect on HCHO oxidation is still not clear. In this work, we regulated the proportions of different Pd sites on Pd/SiO2 catalysts by high-temperature treatment of the carriers. With the increase in treatment temperature, the dominant active sites on Pd particles changed from terraces to steps and finally to corner sites. The corner sites were found to be important for oxygen activation, which led to the HCHO catalytic oxidation performance increasing in the order Pd/SiO2, Pd/SiO2(500) and Pd/SiO2(800). It is worth noting that in the reaction pathway for HCHO oxidation, formate was the primary intermediate on the Pd/SiO2 catalyst. However, in addition to formate, CO species were also detected on the Pd/SiO2(500) and Pd/SiO2(800) catalysts. DFT results confirmed that the corner sites were more favorable for the HCHO → CHO → CO pathway, compared to the terrace sites. This work elucidates the effect of Pd sites on the HCHO oxidation mechanism over Pd/SiO2 catalysts, providing valuable insights for the design of highly active catalysts.

Effects of Supercritical CO2 Treatment on Color, Lipid Oxidation, Heme Iron, Non-Heme Iron and Metmyoglobin Contents in Ground Pork.

The color, lipid oxidation, heme iron (HI) and non-heme iron (NHI) contents, metmyoglobin content and Soret band of myoglobin of ground pork subjected to supercritical CO2 treatment under different conditions, or to heat treatment (40°C, 2 h) and subsequent storage at 4°C were evaluated during 9-day period. Supercritical CO2 treatment significantly increased CIE L* and CIE b* values of ground pork during subsequent storage, while the HI content was slightly affected. In general, CIE a* value and metmyoglobin content were decreased. Supercritical CO2 treatment for 2 h could increase the thiobarbituric acid-reactive substances (TBARS) value, while treatment for 1 h or less had no effect. The NHI content could be increased only after treatment at above 40°C or 17.2 MPa for 2 h. The Soret band of myoglobin was shifted to longer wavelength. Increasing treatment temperature from 35°C to 45°C could increase CIE L*, CIE a*, CIE b* and TBARS values, HI and NHI contents of the ground pork, while decreasing metmyoglobin content. As the treatment pressure increased from 13.8 MPa to 20.7 MPa, CIE b* and TBARS values were decreased, while the NHI and metmyoglobin contents were increased. However, the other parameters were unchanged. Extending exposure time from 0.5 h to 2 h could increase CIE L*, CIE b* and TBARS values, HI contents, while decreasing CIE a* value and metmyoglobin content. Correlation analysis showed that the TBARS value was significantly and negatively correlated with the HI content or metmyoglobin content in samples treated at 40°C or above for 2 h.

Effect of heat treatments on mechanical properties and wear resistance of laser-powder bed-fused Ti6Al4V alloy

The effects of heat treatment on the microstructure, mechanical properties and wear resistance of Selective Laser Melting Ti6Al4V alloy were systematically studied. The results show that the as-built part has an acicular [Formula: see text] martensite structure. The increase in heat treatment temperature causes the decomposition of acicular [Formula: see text] martensite, which leads to the decrease of the hardness of Ti6Al4V alloy. When the heat treatment temperature is 800∘C, the alloy forms an [Formula: see text]/[Formula: see text] structure, which increases the tensile strength and elongation of the alloy by 12% and 23%, respectively. When the heat treatment reaches above 900∘C, the mechanical properties of the alloy decrease sharply due to the disappearance of the [Formula: see text]/[Formula: see text] structure, the coarse grains of the [Formula: see text] phase, and the increase of the content of the [Formula: see text] phase. The tensile strength decreased from 935[Formula: see text]MPa to 815[Formula: see text]MPa, and the elongation decreased from 8.7% to 3.1%. With the increase of heat treatment temperature, the friction coefficient and wear rate increase linearly, which is opposite to the changing trend of hardness, and the wear mechanism is changed from single abrasive wear to abrasive wear and oxidative wear. This is attributed to the increase in the grain size of the alloy and the increase in the content of the [Formula: see text] phase, resulting in a decrease in the overall hardness of the alloy.

Dimensional Stability and Mechanical Properties of Gmelina arborea Roxb. Wood Thermally Modified through Open Reactor and Low-Pressure Closed Reactor Systems

This study focused on the thermal modification of Gmelina arborea Roxb. wood following processes using the open reactor and low-pressure closed reactor systems. The aim is to determine the optimum treatment conditions suitable for gmelina wood due to its poor drying characteristics using the low-pressure closed reactor thermal modification. Subsequent to thermal modification under both processes, the dimensional stability and mechanical properties of gmelina wood were investigated. Effects of the thermal modifications under the open and low-pressure closed reactor systems on mechanical properties were additionally reported. The outcome of this investigation revealed that mass loss increased with increasing treatment temperatures, but minimal mass losses were observed for samples modified in the low-pressure closed reactor system. Due to the low-pressure regime used in the closed reactor system, a lesser improvement was found in volumetric shrinkage, fibre saturation point and tangential-to-radial swelling compared to the improvement in these properties in the open reactor system. Results further revealed that the mechanical properties of gmelina wood deteriorated more rapidly after modification in the open reactor system. Since the properties of modified gmelina wood are comparable at 180 °C under both systems, the closed reactor system will be investigated further to arrive at a suitable treatment condition under higher pressure variations. The thermal modification of gmelina wood with the closed reactor system is more promising in delivering a better quality of modified gmelina wood.

Effect of Hydrothermal Treatment on the Mechanical and Microscopic Properties of Moso Bamboo

In this study, moso bamboo was used as a raw material. To increase the plasticity of bamboo to achieve a greater softening effect, the softening method of hydrothermal treatment was used. Hardness and the flexural elastic modulus were used as the evaluation indices, and the crystallinity and main functional groups of the softened bamboo were analysed using X-ray diffraction and Fourier-transform infrared spectroscopy. Combined with the examination of timber colour, micromorphology, bending strength, and nanomechanical tests, our analysis showed the effects of the hydrothermal treatment on bamboo. The results showed that the hardness and flexural moduli of bamboo decreased with the increase in hydrothermal treatment temperature. However, cracking occurred after 3.5 and 4 h of treatment at 180 °C and 190 °C. This indicated that the softening effect was most pronounced when the treatment temperature and time were 180 ℃ and 3 h, respectively. The cellulose crystallinity of bamboo increased and then decreased with the increase in treatment temperature. Cracks were produced in the cell structure, starch locally disappeared, and the hardness and the elasticity modulus of the thin-walled bamboo cells first increased and then decreased with the increase in treatment temperature.

Evolution of static recrystallization microstructure caused by residual strain of an Al-richen Ni-based single crystal superalloy

Recrystallization has a devastating effect on the service process of single crystal superalloys (SX). This study mainly investigated the static recrystallization (SRX) behavior of an as-cast high Al content nickel-based SX under local or global deformation at room temperature, as well as heat treatment at various temperatures. The microstructural evolution was observed under different conditions using electron back scatter diffraction (EBSD), which was employed to determine the SRX threshold. The results indicated that the critical SRX temperature exceeds 1260 °C, and the critical plastic strain is greater than 5 %. In particular, the characteristic of the higher SRX tendency in the interdendritic region (IDR) of the as-cast SX was discovered, which was attributed to the phenomenon that the IDR with lower deformation resistance was prone to significant plastic accumulation and the bulk γ' could be the nucleation substrate of the SRX. Furthermore, with the increase in heat treatment temperature, there are certain changes in the morphology characteristics of re-precipitated γ' in the vicinity of the SRX grain boundary with a higher migration rate. This is mainly attributed to the decrease in the internal subcooling of the bulk γ' phase and the increase in the concentration of γ' forming elements at the grain boundary front.

Effect of heat treatment on microstructural evolution and mechanical properties of the TiAlV0.5CrMo refractory complex concentrated alloy

Ultra-fine grain TiAlV0.5CrMo refractory complex concentrated alloy (RCCA) was prepared by using mechanical alloying (MA) and spark plasma sintering (SPS), and the effects of heat treatment temperature on phase composition, microstructural evolution and mechanical properties were investigated. The results indicate that the phase composition of as-SPSed alloy comprises disordered BCC1 and BCC2 solid solution phases, along with a minor amount of Al2O3 phase. The system demonstrates exceptional microstructural and phase stability after the heat treatment at 1200 °C for 6 h, with only a slight decrease in hardness to a value of 9.86 GPa. With the increase in heat treatment temperature, the volume fraction of recrystallized grains gradually increases, leading to an initial growth and subsequent refinement in grain size. Under heat treatment at 800 °C and 1000 °C, the increase in volume fraction of Al2O3 was found to enhance the room temperature compressive yield strength of the alloy while deteriorating the plasticity. Specifically, the strength-plasticity trade-off was achieved after heat-treated at 1200 °C for 2 h, with a compressive yield strength of 2667 MPa and a plastic strain of 10.7% at room temperature. The excellent mechanical properties were attributed to the synergistic effects of lattice distortions, reduced dislocation density, weakened texture and refined grain structure. Furthermore, this alloy demonstrated a compressive yield strength of 153 MPa at a temperature of 1100 °C without fracturing at a strain of 50%. The flow stresses exhibited typical dynamic recrystallization (DRX) characteristics at elevated temperatures.

A Comprehensive Study on the Influence of Superheated Steam Treatment on Lipolytic Enzymes, Physicochemical Characteristics, and Volatile Composition of Lightly Milled Rice.

Enzyme inactivation is crucial for enhancing the shelf life of lightly milled rice (LMR), yet the impact of diverse superheated steam (SS) treatment conditions on lipolytic enzyme efficiency, physicochemical properties, and volatile profiles of LMR remains unclear. This study investigated varying SS conditions, employing temperatures of 120 °C, 140 °C, and 160 °C and exposure times of 2, 4, 6, and 8 min. The research aimed to discern the influence of these conditions on enzyme activities, physicochemical characteristics, and quality attributes of LMR. Results indicated a significant rise in the inactivation rate with increased treatment temperature or duration, achieving a notable 70% reduction in enzyme activities at 120 °C for 6 min. Prolonged exposure to higher temperatures also induced pronounced fissures on LMR surfaces. Furthermore, intensive SS treatment led to a noteworthy 5.52% reduction in the relative crystallinity of LMR starch. GC/MS analysis revealed a consequential decrease, ranging from 44.7% to 65.7%, in undesirable odor ketones post-SS treatment. These findings underscore the potential of SS treatment in enhancing the commercial attributes of LMR.

Preparation of ZrP2O7-CePO4 composite porous ceramics and their excellent thermal insulation and wave-transmission performance for supersonic aircraft

In this study, a two-step method combining the direct foaming process with the control of solid content and heat treatment temperature was employed to prepare ZrP2O7-CePO4 composite porous materials with varying porosities. The results indicate that an increase in solid content and heat treatment temperature leads to a reduction in porosity and average pore size while simultaneously improving the mechanical properties. The porosities, compressive strengths, thermal conductivities, ε and Tanδ ranged from 63.2 to 85.3 vol%, 19.43 to 0.99 MPa, 0.089 to 0.088 W/(m·K), 1.64 to 2.72, and 0.88 × 10−3 to 1.99 × 10−3, respectively. Electromagnetic simulations have validated that ZrP2O7-CePO4 composite porous ceramics, when used as the core layer material for A-sandwich antenna radomes, exhibit excellent transmittance properties. This suggests the potential application of these materials for supersonic aircraft antenna radomes.

A flexible piezoelectric/pyroelectric dual-function sensor with high temperature resistance

Most of existing piezoelectric polymers have low glass transition temperatures, so they can only operate at lower temperatures (<150 ℃). Once the operating temperature is exceeded, the piezoelectric performance of the device rapidly decreases. At higher temperatures, dense chain motion can interfere with the orientation of dipoles, thus limiting the development of polymer based high-temperature piezoelectric sensors. High-temperature piezoelectric sensor devices are entirely made of inorganic materials, however, inorganic materials are rigid and can only work under small strains. Therefore, enhancing the temperature resistance of piezoelectric polmers and constructing piezoelectric asymmetric structure are the key to fabricating flexible high-temperature resistant piezoelectric/pyroelectric dual functional sensors. In this study, polyacrylonitrile (PAN) nanofiber film is prepared by electrospinning, and then subjected to heat treatment through programmed temperature control. The effects of the different heat-treatment temperatures on the mechanical and electrical performance of PAN nanofiber film are studied systematically, and the results show that PAN high temperature resistant flexible nanofiber film sensors can be used in high temperature environments (> 500 ℃). Its output performance is improved with the increase of heat treatment temperature (< 260 ℃) and then basically remains unchanged in a temperature range of 260–450 ℃. Finally, the output performance decreases at temperatures higher than 450 ℃. When the heat treatment temperature reaches 260 ℃, the output voltage increases to 10.08 V, and current reaches 2.89 μA. Compared with those of the untreated PAN membranes , its output voltage and current are increase by 3.54 times and 2.83 times, respectively. At the same time, the output of the PAN high temperature resistant flexible nanofiber film sensors is almost unchanged in the high-temperature environments. This is the first time that the pyroelectric effect has been observed in heat-treated PAN nanofiber films and both the open-circuit voltage and short-circuit current have been shown to increase with temperature gradient increasing. Besides, the PAN nanofiber film sensors have durability of more than 5000 cycles at room temperature(25 ℃) even at high temperature (400 ℃). Overall, good flexible, high-temperature resistance, and bifunctional sensing ability make PAN flexible nanofiber film sensors expected to be widely used in high temperature environments such as fire safety, aerospace and other harsh environment.

Effect of Solution Treatment on Mechanical Properties of Inconel 718 Alloy Formed by SLM

Based on SLM forming process, Inconel 718 alloy powder material was used to design and print test parts, and the test parts were treated with solution treatment. This article explored the effects of solution treatment temperature and time on the mechanical properties of Inconel 718 alloy. The results indicate that the solution treatment can effectively improve the tensile strength, yield strength and density of the parts. When the solution treatment temperature increases, the material brittleness becomes larger, and when the solution treatment time prolongs, the material toughness improves. The density of the material increased with the extension of solution treatment time and the increase of temperature.

Microstructural Evolution and Mechanical Properties of a Ni-Based Alloy with High Boron Content for the Pre-Sintered Preform (PSP) Application

The pre-sintered preform (PSP) is an advanced technology for repairing the Ni-based superalloy blade in a turbine. In general, boron is added to the Ni-based superalloys in small quantities (<0.1 wt.%) to increase boundary strength and cohesivity. Despite this, the effect of high B content (>1.0 wt.%) on the microstructure evolution and mechanical properties in Ni-based superalloys for the PSP application is rarely studied. The variety, composition and evolution of the precipitates during solution heat treatment in the alloy with high B content were determined by EBSD, EPMA and SEM. The results indicate that Cr, W and Mo-rich M5B3 type borides precipitate from the matrix and its area fraction reaches up to about 8%. The area fraction of boride decreases with the prolonging of solution time and the increase of temperature higher than 1120 °C. The borides nearly disappear after solution treatment at 1160 °C for 2 h. The redissolution of boride and eutectic results in the formation of B-rich area with low incipient melting (about 1189 °C). It can bond metallurgically with the blade under the melting point of the blade, which decreases the precipitation of harmful phases of the blade after PSP repairing. The microhardness within the grain in the PSP work-blank first decreases (lower than 1160 °C) and then increases (higher than 1185 °C) with the increase of solution heat treatment temperature due to the dissolving and precipitation of borides. The tensile strength of the combination of PSP work-blank and Mar-M247 matrix at room temperature after solution treatment is related to the area fraction of boride, incipient melting and the cohesion between PSP work-blank and Mar-M247 matrix.

Structural properties and failure characteristics of granite after thermal treatment and water cooling

In a variety of fields such as exploitation of geothermal energy and the reconstruction of nuclear waste storage, both of high-temperature and cooling process change the physical and mechanical properties of granite. Uniaxial compression tests were performed on five groups of granite samples at 25 °C, 200 °C, 400 °C, 600 °C and 800 °C after water cooling, and CT scanning, acoustic emission(AE) monitoring and X-ray diffraction(XRD) scanning were used to investigate the structure properties and failure characteristics of granite. It is found that the proportions of pore volume greater than 106 μm3 and less than 105 μm3 with are positively and negatively correlated with the thermal treatment temperature respectively. The mechanical properties of granite are significantly deteriorated by temperature gradient shock, and crack development scale during failure process overall increases as implied by AE response. The failure intensity index η is proposed to characterize the failure severity of granite, and the value of η descends with the increase of thermal treatment temperature, indicating the failure severity of granite is alleviated. Three types of loading failure mode are classified for water-cooled high-temperature granite. The failure mode of granite at 200 °C and 600 °C is tensile failure and tensile-shear failure respectively, while the granite samples are dominated by shear failure at 25 °C, 400 °C and 800 °C.