Thermal Shock Process Research Articles

Grain-based coupled thermo-mechanical modeling for stressed heterogeneous granite under thermal shock

Microscopic damage and macroscopic mechanical properties of granite under the coupling effect of thermal load and initial stress are crucial considerations for the safe construction of underground geo-energy engineering. However, visualizing real-time micro-crack processes in rocks under high-temperature and high-pressure conditions using the current experimental techniques remains challenging. In this study, a numerical method is developed to analyze the thermally induced damage in heterogeneous granite under the coupled influence of initial stress and thermal loading. A biaxial thermo-mechanical grain-based model considering real mineral distribution is established based on digital image processing technology, the grain-based modeling method, and heat conduction theory. The microscopic parameters are calibrated and the effectiveness of the model is verified based on thermal shock and uniaxial compression experiments. The thermal destruction mechanism of granite under initial stress from a microscopic perspective was unveiled for the first time. During the thermal shock process, the stress within the rock does not remain constant at the initial stress value. Instead, it changes continuously with the progression of heat conduction. The impact of the initial stress on the thermally induced cracks is relatively minor. Cooling causes more damage to the rock than heating during thermal shock. The intragranular cracks of quartz consistently outnumber other intragranular or intergranular cracks during thermal shock. The initial stress and thermal shock damage enhance and weaken the biaxial peak strength of granite, respectively. The weakening effect of thermal shock on the peak strength becomes more pronounced at a higher initial stress. These research findings and proposed research techniques contribute to the management and optimization of underground geo-energy engineering.

Mechanical properties and thermal shock resistance of TiB2‒B4C composite ceramic tool materials at microscopic scale

AbstractA finite model incorporating microstructure was developed to investigate the thermal shock resistance of TiB2‒B4C composite ceramic cutting tool materials. Numerical simulations were conducted to analyze changes in the transient temperature field and thermal stress field during the thermal shock process. TiB2‒B4C composite ceramic tool materials were fabricated using discharge plasma sintering technology. With different B4C contents, different sintering temperatures and holding times as study variables, optimization of the sintering process parameters and ceramic material components was achieved through testing the mechanical and microscopic morphology of the ceramics. Thermal shock water quenching experiments were performed, and the strength‐decay method was employed to assess the thermal shock resistance of TiB2‒B4C ceramics. The findings indicate that the optimal sintering conditions are temperature of 1700°C and holding time of 5 min. The TiB2‒B4C ceramic material containing 20 vol% B4C exhibits superior comprehensive mechanical properties and thermal shock resistance, and its relative density, fracture toughness, hardness, and flexural strength were 99.3%, 6.8 MPa m1/2, 22.8 GPa, and 598 MPa, respectively. The critical thermal shock temperature difference falls within the range of 400°C‒500°C.

Millisecond activity modulation of atomically-dispersed Fe–N–C catalysts

Precious-metal-free transition metal–N–C catalysts containing atomic MeNx centers are promising candidates for the oxygen reduction reaction (ORR) in rechargeable zinc-air batteries. In this study, we report the highly efficient synthesis and activity modulation of Me–N–C (Me = Fe, Co, Ni, and Cu) catalysts utilizing the flash Joule heating technique, accomplished within 200 milliseconds. The instantaneous high temperature (∼3535 K) and rapid heating and cooling rates (above 104 K s–1) induce the formation of atomically-dispersed MeNx sites on the surface of carbon nanotube matrices. This ultrafast thermal shock process not only prevents the aggregation of isolated metal atoms but also achieves catalytic activity modulation through heteroatom engineering. Typically, phosphorus atoms play a crucial role in suppressing nitrogen loss and regulating the local coordination environment of FeNx centers, thereby facilitating the 4 e– electrocatalytic reduction of oxygen. As expected, the phosphorus-doped Fe–N–C catalyst exhibits excellent ORR activity with a high half-wave potential of 0.904 V and a low Tafel slope of 23.1 mV dec–1 in a 0.1 M KOH medium. The assembled zinc-air battery demonstrates a prominent power density of 236.3 mW cm–2 and desirable long-term durability over 400 h, surpassing that of the Pt/C+IrO2-based battery.

Ultrafast In-Situ synthesis of flexible MoO3 anode in five seconds for High-Performance aqueous zinc ion hybrid capacitor

The efficient synthesis of high-performance α-MoO3 on flexible conductive substrates is crucial for enhancing its value in the field of energy storage. However, traditional synthesis methods currently employed often suffer from slow heating rates, intricate reaction processes involving multiple steps, sluggish reaction kinetics, high energy consumption, and prolonged preparation times, thereby hindering efficient production. Presented herein is a facile, ultrafast, and versatile approach utilizing microwave carbon thermal shock, a one-step reaction synthesis of α-MoO3 on carbon substrates within 5 s. During microwave carbon thermal shock, the precursor salt experiences an extremely rapid heating rate, swiftly decomposing to form small-sized α-MoO3 crystals. Simultaneously, this process promotes the oxidation of adjacent carbon sites, thereby imparting multi-scale defects and oxygen-containing functional groups to the resulting carbon cloth (CC). The exceptionally low reaction energy barriers and superior Gibbs free energy (ΔG) further substantiate the advantages of the microwave carbon thermal shock strategy over traditional synthesis methods in terms of both kinetics and thermodynamics. The air-assisted transient microwave carbonthermal shock (AMCTS) process circumvents high energy requirements, multistep reactions, and extended preparation times, endowing AMCTS-CC@MoO3 with remarkable flexibility and processability. In demonstrating its practical utility within zinc-ion hybrid micro capacitors, it exhibits outstanding specific capacitance (up to 2300mF cm−2) and mechanical stability. This air-assisted transient microwave thermal shock process provides an efficient route for ultrafast and low-cost synthesis of flexible zinc-ion anode materials.

Combination of a hierarchical and thermal shock process with a specific aqueous buffer: a safe, rapid and reliable DNA extraction method for plant endophytic fungi

Combination of a hierarchical and thermal shock process with a specific aqueous buffer: a safe, rapid and reliable DNA extraction method for plant endophytic fungi

The thermal shock resistance of in-situ synthesized mullite absorption and storage integrated ceramics for solar thermal power generation

Solar high-temperature thermal power generation systems require thermal storage materials with excellent thermal shock resistance due to the large temperature difference during operation (in the range of 20–800 °C). In this study, mullite-based absorption and storage integrated ceramics were prepared using low-cost bauxite and kaolin as raw materials and Fe2O3 as additive. The effect of Fe2O3 on the thermal shock resistance of mullite-based ceramics was investigated. The results showed that the absorption and bending strength of sample BK4 (bauxite: 50 wt%, kaolin: 50 wt%, Fe2O3: additional 11 wt%) increased by 2.98% (89.8%) and 8.00% (147.10 MPa), with a storage thermal density of 1185.75 kJ kg−1 after 30 thermal shock cycles. The mechanism for the excellent thermal shock resistance of the ceramics is revealed from the aspect of the changes in phase and microstructure of the samples induced by the changes in the mass transfer rate during the thermal shock process. It was calculated that a unit volume of BK4 (with a raw material cost of about 154.22 USD) could generate 974.95 kW h of electricity (saving 119.92 kg of coal) when used in a solar thermal storage system.

Failure Mechanism of Thermal Barrier Coatings on Nozzle Guide Vanes Fabricated from Nickel-Based Single-Crystal Superalloy under Gas Thermal Shock Conditions

The objective of this study was to investigate the early failure behavior of thermal barrier coatings on single-crystal nozzle guide vanes under gas thermal shock conditions. The microstructure and mechanical properties of the thermal barrier coating before and after the gas thermal shock tests were analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and microhardness testing. The results indicate the presence of a mixed layer containing Ni, Cr, Al, Zr, and O at the base of the ceramic layer, and reveal failure behavior in the thermal barrier coating. The analysis suggests that the incomplete formation of the thermal growth oxide layer between the ceramic layer and the bonding layer, before the deposition of the YSZ ceramic layer, led to the easy diffusion of elements from the bonding layer into the root of the ceramic layer during the gas thermal shock process, resulting in the formation of a mixed layer. In the test environment, significant thermal stress was generated in the mixed layer, leading to transverse cracks and ultimately causing early failure of the thermal barrier coating. Consequently, the “incomplete initial TGO layer” model is proposed.

Experiment and numerical simulation study of thermal fatigue of an aluminum alloy piston

AbstractIn this study, a magneto‐thermo‐structural coupling finite element method was proposed to calculate the electromagnetic field, temperature field, stress field, and strain field of an aluminum alloy piston during thermal shock process. The computed temperature results at the measurement points of T3 and T4 agree well with the measured data. The concept of tensile strain energy density was proposed as a thermal fatigue damage parameter, and the thermal fatigue life of the piston was predicted on the basis of the calculated results by magneto‐thermo‐structural coupling analysis and tensile strain energy density‐life equation; the discrepancy between the predicted life and the experimental one is 16%. The thermal fatigue failure mechanism of the piston was also clarified. High cyclic stresses occur on the edge of Si due to the difference in thermal expansion coefficient of Al and Si; micro cracks first originate on the edge of Si, then grow through combining other micro cracks, and eventually form macro cracks.

Current-induced solder evolution and mechanical property of Sn-3.0Ag-0.5Cu solder joints under thermal shock condition

Solder joint reliability suffers great challenges due to high current density and miniature solder bump diameter of electronic packages at cryogenic temperature. To tackle these issues, the solder microstructure evolution and the corresponding failure mechanism should be emphasized. In this study, the current-induced microstructure characteristics and mechanical behavior of Sn-3.0Ag-0.5Cu (SAC305) solder joints during thermal shock process was thoroughly addressed over cycles by combining diffusional, electrical, thermal and mechanical features. This result verified that the combining method of thermal shock and electromigration (EM) contributed to the atom diffusion and high thermal stress formation, further causing intermetallic compound (IMC) growth, the repaid dissolution of Cu pad and high thermal stress of the solder joints. High stress induced by either the thermal expansion mismatch of different component, large temperature change (ΔT =346 ℃) and severe lattice distortion became the direct reason for twins and cracks formation of SAC305 solder joints. The combination of crack propagated along the interface and the quick dissolution of Cu substrate at the corner accelerated the eventually failure of the solder joints. Moreover, as the thermal chock cycles was extended, the initiation and propagation of cracks at the cathode side weaken the cathodic shear strength. High stress-induced twin formation at the interface effectively moderated the shear strength degradation due to anode IMC growth after 9 cycles. This study contributed to thoroughly grasp the failure mechanism of the solder joints and design the twin-strengthened Sn-based solder joints under the coupling effects of extreme temperature variation and current stressing.

Measurement of ceramics cracking during water quenching by digital image correlation

Measuring the thermal shock crack growth process is crucial for revealing ceramic materials and structures’ thermal shock failure mechanisms and evaluating their reliability. We used a self-made water quenching system to conduct thermal shock tests on alumina and zirconia ceramics. The thermal shock process was recorded by high-speed digital image correlation (DIC) during the test. The process of thermal shock crack initiation and propagation in two kinds of ceramics was determined by analyzing the speckle image change on the sample’s surface. It is found that the crack growth rate of alumina is faster than that of zirconia, which is caused by different material parameters. This paper presents an in-situ measurement method for the initiation and propagation of thermal shock cracking in ceramic materials. It can provide a measurement method to identify and predict the thermal shock damage of ceramic components.

Experimental studies on the effect of cyclic thermal shock and cooling methods on the mechanical properties and fracture behavior of prefabricated fissured sandstone

The construction of sandstone thermal storage systems and the evaluation of their long-term stability are of great significance to the development of geothermal energy. In this study, the effect of the number of thermal shocks and cooling methods on the mechanical properties and fracture behavior of sandstone containing a single prefabricated fissure was investigated. The experimental results show that as the number of thermal shocks increases, the peak stress and elastic modulus of the fissured sandstone gradually decrease, and show a very good exponential functional relationship. The first thermal shock weakens the mechanical properties of fissured sandstone most severely, and the deterioration effect of mechanical properties is significantly slowed down when the number of thermal shocks exceeds 4. In addition, compared with water cooling, the reduction of the mechanical properties of fissured sandstone by air cooling is lower. As the cooling water temperature decreases, the thermal shock effect of the fissured sandstone is more severe, resulting in more significant damage. An empirical formula considering the number of thermal shocks and cooling water temperature is proposed to characterize the damage to the fissured sandstone. The crack initiation of fissured sandstone under uniaxial compression subjected to different thermal shocks is dominated by tensile failure (wing crack). As the number of thermal shocks increases and the cooling water temperature decreases, the initial crack modes gradually change from T1 to T2, or a more complex pattern. Subsequently, the thermal shock process of fissured sandstone is simulated in COMSOL Multiphysics. The effect of heat transfer coefficient and cooling water temperature on the temperature field and stress field in fissured sandstone are discussed, and the reasons for the thermal cracking of the fissured sandstone under thermal shock are revealed.

Preparation and thermal shock resistance of anorthite solar thermal energy storage ceramics from magnesium slag

Anorthite solar thermal energy storage ceramics were fabricated from magnesium slag solid waste by pressureless sintering. The effects of CaO/SiO2 ratio and sintering temperature on the physical, chemical, and thermophysical properties of ceramics were explored. X-ray diffraction results demonstrated that thermal shock process contributed to the formation of anorthite, and increasing CaO/SiO2 ratio promoted the transformation of anorthite (CAS2) into melilite (C2AS). Some micro-cracks were found according to SEM analysis, forming by the mismatch of thermal expansion coefficients among phases. The combined effects of the low thermal expansion coefficient of anorthite and micro-crack toughing endowed the ceramic with good thermal shock resistance. Optimum comprehensive performances were observed in the sample with a CaO/SiO2 ratio of 0.58 sintered at 1160°C, of which the specific thermal storage capacity was 0.63 J·g-1·°C-1(room temperature). The bending strength increased by 0.22% after 30 thermal shock times (room temperature-800°C, wind cooling). Therefore, the anorthite ceramics exhibited great potential for solar thermal energy storage.

Microstructural evolution during thermal shock process and the residual strength of Si3N4 ceramics

AbstractThermal shock resistance of silicon nitride was investigated from aspects of residual strength and microstructure, using a water quenching method. The residual strengths after 800 and 1000°C thermal shock polarized as higher ones and much lower ones, and reasons for the huge disparity are explored. With heat treatment temperature getting higher, the inner small pores rush to and aggregate in the surface layer of the samples. When the heat treatment reaches 1400°C, a darker subsurface layer is observed, which is caused by the loss of most Al and Y elements. Moreover, many more small pores are found in this layer, acting as the dissipation sources, they protect the material strength by releasing the intense thermal stress. But this subsurface layer disappears during the natural cooling down to 600°C as Al and Y uniformly redistributed in extended oxidation, then huge cracks form on the surface layer undergoing much smaller thermal stress from 600 to 0°C. Moreover, the bonding Y and Si can be oxidized into two types of Y2Si2O7 crystals that improve the thermal shock performance of Si3N4.

N-doped graphene film prepared by rapid thermal shock for ultra-sensitive temperature reading

Graphene is restricted by its zero-band gap when applying in functional components. However, its band structure can be adjusted appropriately through nitrogen doping. At present, many nitrogen doping processes have been developed such as chemical vapor deposition, thermal annealing and plasma sputtering, but in general these methods are time-consuming and difficult to control the type of nitrogen atom doped. In this work, an in situ high-temperature thermal shock process, with an extremely fast rate of temperature change of more than 104 K/s, is developed and used to prepare the nitrogen doped graphene (NG) films. This novel N-doped process enables the preparation of NG films within 10 s, which is the fastest to the best of our knowledge. Moreover, the type and content of doped nitrogen atoms can be effectively regulated by controlling the composition of precursor films. Optimally, the nitrogen content of NG film reaches 2.26 %, and the proportion of graphite nitrogen is more than 60 %. The electrical conductivity and the average Seebeck coefficient of the NG film are 13,870 S·m−1 and −46.5 μV/K, respectively. Its thermoelectric power factor reaches 30 μW·m−1·K−1, indicating that the NG film has a good prospect of functional application. Furtherly, A NG film-based temperature reading device is developed, which shows ultra-high accuracy and sensitivity in temperature reading within a rather wide temperature range.

Ultra-high temperature oxidation resistance of a novel (Mo, Hf, W, Ti)Si2 ceramic coating with Nb interlayer on Ta substrate

In order to solve the challenge of recyclability of tantalum substrates in high temperature oxidation environments, a novel MoSi2-WSi2-HfSi2-TiSi2 composite ceramic coating containing an Nb interlayer was prepared on the surface of tantalum substrate by a three-step method. The mix ceramic silicide coating exhibited superior performance and effective protection for 10.2 h at 1800 °C, possibly due to the formation of an outer SiO2-HfO2-HfSiO4 composite oxide film with low oxygen permeability, moderate viscosity and thermal expansion coefficient, as well as good self-healing ability. Furthermore, the coating successfully passed 537 thermal cycles from room temperature to 1800 °C. The presence of Nb interlayer significantly mitigated the thermal mismatch between the ceramic coating and the tantalum substrate, and the bidirectional diffusion of Nb element during the high temperature oxidation and thermal shock process further reduced the tendency of the coating to crack.

Effect of surface brittle-to-ductile transition on high-temperature thermal shock resistance of Al2O3 ceramics

The effect of surface brittle-to-ductile transition (BDT) on the high-temperature thermal shock resistance (TSR) of Al2O3 ceramics was investigated by quenching in a cold compressed-air flow. The brittle-to-ductile transition (BDT) and transition temperature were determined from the transformation in fracture mechanism via measuring flexural strength at elevated temperatures. Effects of cooling rate on the residual strength and microstructural evolution of Al2O3 ceramics were systematically studied. Results showed that the BDT temperature in Al2O3 ceramics was around 1000 °C. The BDT mechanism is associated with the softening of the grain boundary glass phase, which permits a certain degree of crack passivation to reduce thermal stress concentration. Compared with the original strength of 375 MPa, the residual strength of the specimen decreased rapidly to 190 MPa at a final temperature of 700 °C, while the residual strength of the specimen was maintained to 352 MPa at a final temperature of 1000 °C. The appearance of surface BDT in Al2O3 ceramics during the high-temperature thermal shock process produces a favorable impact on improving the residual strength of specimens by blunting the crack tip and reducing the surface thermal stress. Therefore, the surface BDT in Al2O3 ceramics is beneficial to the improvement of the high-temperature TSR of Al2O3 ceramics.

Application of resin-TiO2 nanoparticle hybrid coatings on travertine stones to investigate their durability under artificial aging tests

Three different stone coating products including industrial resin, resin-anatase nanoparticles and resin-rutile nanoparticles (NPs) were used to evaluate their stone surface protection effect against thermal shock and salt crystallization on three types of porous travertine stones. The results showed that the use of nanoparticles of both TiO2 polymorphs (rutile and anatase) dispersedly in resin, significantly increased durability of the stones surfaces during the aging tests. No color change in the sample surfaces is another advantage of the resin-TiO2 NPs hybrid coating. Product with anatase nanoparticles shows by far the best performance in protecting the stone surfaces. In both aging tests, samples coated by resin-anatase NPs had the lowest mass changes and the highest surface hardness compared to samples coated by the other coatings. Mineralogy, porosity and microbial activity textural features controlled the durability of the studied stones. Mono-mineral composition and macro porosity of studied samples explain their significant durability against the thermal shock process. On the other hand, the growth of salt crystals in the pore space of the stones in some cases induced macroscopic cracks, particularly in Abarkooh sample with high porosity and microbial textural features Scanning electron microscopy observation confirms that the samples underwent microcracking processes related mainly to salt crystallization pressures. Finally it can be concluded that the resin-TiO2 NPs hybrid coating had a good compatibility with the stone substrate and could be very promising to protect the porous stone façades against natural aging processes.

Residual stress variation and deformation of shot peened glass fiber reinforced composites/aluminum–lithium laminates under thermal shock and thermal fatigue

AbstractThis paper aims to reveal the deformation mechanism of glass fiber reinforced composites (GFRP)/aluminum–lithium (Al–Li) laminates under thermal shock or fatigue and verify reliability of shot peen forming for the composites. In this study, residual stresses in laminate after shot peening was analyzed using finite element model, and the simulation results were verified by experiments. It was found that the shot peened laminates, compared with pure metal panel, similarly exhibited compressive stress at the two external metal surfaces and tensile stress in GFRP layer. The residual stresses changed discontinuously at the metal/fiber and 0°/90° fiber interface owing to the different modulus. Moreover, stresses generated during curing process significantly affected the final deformation after shot peening. Residual stresses altered in each layer with the increase of temperature from 0 to 100°C, which caused the arc height of the laminate decreased. However, the arc height increased to initial dimensions when the temperature dropped to 0°C. Thermal shock process was proved that it hardly influenced the sample geometry. The stress relaxation behaviors were found in long‐term thermal fatigue. 1100 cycles from −55 to 100°C, which lasted 4 h in every cycle, resulted in 5% decrease of the arc height. The deformation problem should be further concentrated on for components made of GFRP/Al–Li laminates and processed by shot peen forming technology.

A novel approach for the synthesis of lanthanum aluminate nanoparticles using thermal shock assisted solid-state method as a microwave absorber layer

In this research, lanthanum aluminate (LaAlO3) nanoparticles were synthesized by a solid-state reaction followed by the thermal shock process; this was done by applying high purity materials for microwave absorption applications. The fabricated nanoparticles were analyzed using different techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) method and field emission scanning electron microscopy (FE-SEM). The results indicated that the fabricated LaAlO3 particles formed nanocrystallites with the average grain size of 90 nm and an appropriate morphology with the related functional groups. The rhombohedral structure of the synthesized sample was identified by the X-ray diffractogram. Also, microwave absorber samples containing paraffin and lanthanum aluminate as the wave absorber parts were prepared. The electromagnetic parameters were measured by utilizing a vector network analyzer (VNA) in the frequency range of 8.2–12.4 GHz. The results related to electromagnetic absorbability indicated that the binary samples showed great microwave absorption qualities. The RL values of paraffin-based nano-LAO samples was strongly affected by the amount of LAO segments and the thickness of the samples. The sample with 10% LaAlO3 particles and the thickness of 1 mm showed a minimum reflection loss of −10.37 dB at 10.55 GHz. The advanced and innovative strategy used in the present study can be practically applied to obtain binary samples based on paraffin and dielectric particles to serve as microwave absorber layers.

Thermal shock behavior of co-continuous TiCx-Cu cermets in air and anaerobic environment

The present work investigated the microstructure and mechanical properties of TiCx-Cu cermets before and after thermal shock tests. Thermal shock temperature was from 800 °C to 1200 °C and number of cycles was from 1 to 20. The results indicated that TiCx-Cu cermets with co-continuous structure exhibited a stable and excellent thermal shock resistance. When quenched at 1000 °C for 1 cycle, the residual flexural strength of the cermet increased to 882 MPa, which was 10.1% higher than that without thermal shock. After 20 cycles of thermal shock, the residual flexural strength still maintain 760 MPa. When quenched at 800 °C and 1200 °C, the strengths of cermet decreased correspondingly, which were caused by the thermal mismatch between metal and ceramics and effusion of Cu or collapses of oxide layer, respectively. Herein, the recrystallization and refinement of metal phase grains caused during the thermal shock process, resulting in the superior thermal shock performance of cermet.