Extreme Temperature Environments Research Articles

Effects of extreme temperature environments on nonlinear vibrations of the cable-stayed functionally graded beam

A cable-stayed functionally graded beam (CSFGB) model is proposed for the first time to study nonlinear behaviors of the system exposed to extreme temperatures. To this end, the in-plane one-to-one internal resonance between the global mode (FGB's mode) and the local mode (cable's mode) is explored under the condition of external primary resonance. First, governing differential equations of the system considering temperature effects are derived by using Hamilton's principle. To obtain the modal function of the FGB, the in-plane eigenvalue problem is solved through the separation-of-variables method. Subsequently, ordinary differential equations (ODEs) are yielded according to Galerkin discretization. The method of multiple time scales is then applied to deal with the ODEs and derive the modulation equations. Based on the above theoretical solutions, the frequency-/force-response curves at three different temperatures are delineated via Newton-Raphson method and the continuation of fixed points. Meanwhile, the time histories and phase portraits are also provided by directly integrating the ODEs. The results show that temperature changes have a significant influence on nonlinear characteristics of the system.

Process optimization and tribological behavior of Ti-48Al-2Cr-2Nb prepared by selective electron beam melting

Selective electron beam melting (SEBM) technology was utilized to fabricate TiAl alloys which possess low density and excellent high-temperature performance, to achieve lightweight design of automotive engines. The forming process of Ti-48Al-2Cr-2Nb was systematically optimized, and found that the microstructure of TiAl formed by SEBM consisted of a layer of alternating γ-band structure and duplex-like structure. As the energy density increases, grain coarsening, proportion increasing of high angle grain boundaries, and anisotropy strengthening occur successively. The forming quality of TiAl reaches its peak at an energy density of 22.5 J/mm3, at which point its mechanical properties and wear resistance also perform the best. Subsequently, in-depth friction experiments at high and room temperatures were conducted, and it was found that at room temperature, as the load increased, the friction coefficient of the samples decreased and the wear rate increased. In addition, the friction coefficient decreases from 0.54 to 0.44, while the wear rate increases from 19.90×10−5 mm3/(N·m) to 25.97×10−5 mm3/(N·m). At this point, abrasive and adhesive wear were the main wear mechanism. Under high temperature conditions, the wear mechanism of the substrate is mainly abrasive wear, adhesive wear, and oxidative wear. And the friction coefficient decreases from 0.69 to 0.49. At lower temperatures, the detached debris was filled and solidified on the wear marks under the action of the friction ring, forming a hardened layer called “enamel”, which can alleviate the negative effects of wear. Under the influence of extreme high temperature environment, the unworn surface forms a light blue oxide film due to rapid oxidation, known as the “burning blue” phenomenon. Along with the high-temperature oxidation phenomenon confirmed by EDS, the oxide layer is more prone to peeling off and forming debris. In addition, melting softening occurs inside the annular wear scar, which increases the amount of deformation under external force, ultimately leading to a significant increase in wear.

Microstructurally resolved electrochemical evolution of mechanical- and irradiation-induced damage in nuclear alloys

There is a need for high-throughput, scale-relevant, and direct electrochemical analysis to understand the corrosion behavior and sensitivity of nuclear materials that are exposed to extreme (high pressure, temperature, and radiation exposure) environments. We demonstrate the multi-scale, multi-modal application of scanning electrochemical cell microscopy (SECCM) to electrochemically profile corrosion alterations in nuclear alloys in a microstructurally resolved manner. Particularly, we identify that both mechanically deformed and irradiated microstructures show reduced charge-transfer resistance that leads to accelerated oxidation. We highlight that the effects of mechanical deformation and irradiation are synergistic, and may in fact, superimpose each other, with implications including general-, galvanic-, and/or irradiation-activated stress-corrosion cracking. Taken together, we highlight the ability of non-destructive, electrochemical interrogations to ascertain how microstructural alterations result in changes in the corrosion tendency of a nuclear alloy: knowledge which has implications to rank, qualify and examine alloys for use in nuclear construction applications.

Entropy-Driven Hydrated Eutectic Electrolytes with Diverse Solvation Configurations for All-Temperature Zn-ion Batteries.

Batteries always encounter uncontrollable failure or performance decay under extreme temperature environments, which is largely limited by the properties of electrolytes. Herein, an entropy-driven hydrated eutectic electrolyte (HEE) with diverse solvation configurations is proposed to expand the operating temperature range of Zn-ion batteries. The HEE possesses over 40 types of Zn2+ solvation structure with uniform distribution, contributing to its much higher solvation configurational entropy compared to the conventional aqueous counterpart (only 6 types). These effectively promote its anti-freezing ability under ultralow temperatures, with a high ionic conductivity of 0.42 mS cm-1 even at a low temperature of -40 °C. Moreover, the entropy-driven property can simultaneously enhance the thermal stability under a high temperature over +140 °C. Therefore, the HEE can enable full cells stably working over a wide temperature range of -40~+80 °C, performing over 1500 cycles with 100 % capacity retention at -40 °C and 1000 cycles with ~72 % capacity retention at +80 °C. This inspiring concept of entropy-driven electrolyte with quantized solvation configurational entropy value has charming potential for designing future special batteries with excellent adaptability towards extreme temperature environments.

Entropy‐Driven Hydrated Eutectic Electrolytes with Diverse Solvation Configurations for All‐Temperature Zn‐ion Batteries

AbstractBatteries always encounter uncontrollable failure or performance decay under extreme temperature environments, which is largely limited by the properties of electrolytes. Herein, an entropy‐driven hydrated eutectic electrolyte (HEE) with diverse solvation configurations is proposed to expand the operating temperature range of Zn‐ion batteries. The HEE possesses over 40 types of Zn2+ solvation structure with uniform distribution, contributing to its much higher solvation configurational entropy compared to the conventional aqueous counterpart (only 6 types). These effectively promote its anti‐freezing ability under ultralow temperatures, with a high ionic conductivity of 0.42 mS cm−1 even at a low temperature of −40 °C. Moreover, the entropy‐driven property can simultaneously enhance the thermal stability under a high temperature over +140 °C. Therefore, the HEE can enable full cells stably working over a wide temperature range of −40~+80 °C, performing over 1500 cycles with 100 % capacity retention at −40 °C and 1000 cycles with ~72 % capacity retention at +80 °C. This inspiring concept of entropy‐driven electrolyte with quantized solvation configurational entropy value has charming potential for designing future special batteries with excellent adaptability towards extreme temperature environments.

Current-carrying tribological behavior of C/Cu contact pairs in extreme temperature and humidity environments for railway catenary systems

Current-carrying tribological behavior of C/Cu contact pairs in extreme temperature and humidity environments for railway catenary systems

Ultra strong, tough and extreme environments resistant PBO papers with a nacre-like structure constructed by synergistic electrostatic interaction and interlayer entanglement

In extreme environments, it is difficult to balance the strength and toughness of ultra-thin film materials. To address this problem, we propose a promising strategy to build ultra strong, tough and extreme environments resistant Poly(p-phenylene-2,6-benzobisoxazole) (PBO) papers with a nacre-like structure constructed by synergistic electrostatic interaction and interlayer entanglement through the sol–gel-film method and hot press orientation. Highly interconnected PBO nanofibres （PNFs） with positive charges are tightly wound around the anisotropic graphene oxide (GO) nanosheets with negative charges through strong electrostatic interaction, forming a nacre like microstructure. The addition of Fe (Ⅲ) can form a coordination bond with the amino group on PNFs. Chemical crosslinking and hydrogen bonding synergize with interlayer entanglement effect among different PNFs，which can effectively dissipate interlayer energy and alleviate the conflict between strength and toughness. The resultant tensile strength and toughness are as high as 338.3 MPa and 16.04 MJ/m3，which are 197.7 % and 425.4 % of those of the intrinsic PBO paper, respectively. Additionally, after 5000 folding-unfolding cycles, the tensile strength retention and toughness retention of the PBO/GO/Fe (PGFe) paper were still 85.4 % and 71.9 %, respectively. Moreover, the paper exhibits excellent tolerance to extreme temperature environments and showed extremely strong chemical stability.

Whole genome resequencing reveals the adaptability of native chickens to drought, tropical and frigid environments in Xinjiang

Chickens exhibit extensive genetic diversity and are distributed worldwide. Different chicken breeds have evolved to thrive in diverse environmental conditions. However, research on the genetic mechanisms underlying chicken adaptation to extreme environments, such as tropical, frigid and drought-prone regions, remains limited. In this study, we conducted whole-genome sequencing of 240 individuals from six native chicken breeds in Xinjiang, China, as well as 4 publicly available chicken breeds inhabiting regions with varying annual precipitations, temperatures, and altitudes. Our analysis revealed several genetic variants among the examined breeds. Furthermore, we investigated the genetic diversity and population structure of breeds residing in extreme drought and temperature environments by comparing them. Notably, native chicken breeds exhibited different genetic diversity and population structures. Moreover, we identified candidate genes associated with chicken adaptability to the environment, such as CORO2A, CTNNA3, AGMO, GRID2, BBOX1, COL3A1, INSR, SOX5, MAP2 and PLPPR1. Additionally, pathways such as lysosome, cysteine and methionine metabolism, glycosaminoglycan degradation, and Wnt signaling may be play crucial roles in regulating chicken adaptation to drought environments. Overall, these findings contribute to our understanding of the genetic mechanisms governing chicken adaptation to extreme environments, and also offer insights for enhancing the resilience of chicken breeds to different climatic conditions.

Design of Wide‐Temperature Lithium‐Sulfur Batteries

AbstractIn electrochemical energy storage (EES), lithium‐sulfur (Li−S) batteries have recently gained recognition for their exceptional theoretical specific capacity, making them stand out among a wide range of cutting‐edge energy storage technologies. While Li−S batteries demonstrate a long cycle life under regular conditions, expanding their application scenarios is crucial for their future development. Specifically, ensuring stable battery operation in extreme temperature environments, such as below 0 °C and above 60 °C, becomes paramount. Thus, this review aims to summarize the recent progress of Li−S batteries in extreme temperature ranges and analyse the processability of critical materials within these batteries at extreme temperatures. Ultimately, this review presents insights and potential prospects for Li−S battery systems operating within a wide temperature range, contributing to advancing energy storage devices capable of functioning across various temperatures.

Effect of phonon anharmonicity on thermal conductivity of ZnTe Thin films

The ZnTe thin film is a potential material for optoelectronic devices in extreme temperature and radiation environments. In this report, the thermal conductivity of ZnTe films is measured non-invasively using the micro-Raman method and correlated with the phonon anharmonic effect. The evolution of crystalline ZnTe thin films from Te/ZnO bilayer by thermal annealing at 450 ∘C has been observed above the melting point of Te, which is confirmed from x-ray diffraction and high-resolution transmission electron microscopy. The ZnTe thin films illustrate three longitudinal phonon modes with higher harmonics of nLO (n = 3) at room temperature. Temperature-dependent Raman spectra in the range of 93–303 K are used to analyze the phonon anharmonicity from Raman shift, FWHM, and Phonon lifetime of the thin films. The Balkanski model is used to fit the anharmonicity-induced phonon frequency shift of nLO modes as a function of temperature, taking into account three- and four-phonon interactions. The intensity ratio of the I 2LO /I 1LO and I 3LO /I 2LO provide information about the electron-phonon coupling strength, which is influenced by the anharmonic effect. The laser power-dependent Raman spectra are used to determine the thermal conductivity of the ZnTe films, which is found to be approximately 9.68 Wm−1K−1, remains relatively constant for all nLO modes, indicating that multi-phonon scattering process. The correlation between thermal conductivity and phonon anharmonicity can pave the way for understanding the phonon scattering process in ZnTe thin films for high-performance optoelectronic device applications in harsh conditions.

A Study of a Cryogenic CuAlMn Shape Memory Alloy

In extreme temperature environments, a newly emerging engineering application involves both the active and passive control of structures using cryogenic shape memory alloys, which are smart materials able to recover high deformation below the freezing point. With the objective of carrying out new advances in this area, the present work aims to investigate the Cu-7.5Al-13.5Mn (wt.%) shape memory alloy. Thermal, microstructural, and thermomechanical analyses of as-cast and hot-rolled specimens were performed, taking into account the effects of annealing and solubilization. It was observed that the phase transition occurs at temperatures below 120 K and changes according to the thermo-mechanical path. Specifically, hot-rolling lowers the phase transition temperature range with respect to the as-cast condition–from 34 K to 23 K for Mf, and from 89 K to 80 K for Af. Additionally, when the annealing temperature rises, the phase transformation temperature increases as well, and the alloy loses its cryogenic features when heat treated above 473 K. Finally, loss factors of 0.06 and 0.088, which were respectively found in dynamic and static settings, validate the material’s good damping response.

Improved shear property of Sn-3.0Ag-0.5Cu/Ni micro solder joints under thermal shock between 77 K and 423 K by adding TiO2 nanoparticles

The rapid development of space exploration technology was intensifying the desire for lead-free solders with high performance and reliability under extreme temperature environments. In this study, the influence of TiO2 nanoparticle addition on the microstructure, growth behavior of interfacial intermetallic compounds (IMCs) and shear property of Sn-3.0Ag-0.5Cu (SAC305)/Ni micro solder joints under thermal shock from 77 K to 423 K was systematically investigated. The results indicated that the grain size of β-Sn, IMC (Ag3Sn and (Cu,Ni)6Sn5) particles inside the solder was refined by adding 0.05 and 0.1 wt% TiO2 nanoparticles. Due to the spalling of interfacial IMCs into the solder occurring in all micro joints during thermal shock, the thickness of interfacial IMCs did not show a monotony increasing trend with increasing thermal cycles. However, the micro composite solder joint added with 0.05 and 0.1 wt% TiO2 nanoparticles always exhibited thinner interfacial IMC thickness and higher shear force compared with the plain micro joints during thermal shock. The inhibiting effect of TiO2 nanoparticles on the interfacial IMC growth could be explained by the adsorption theory and grain boundary pinning theory. The improvement in shear property of micro composite solder joints was primarily induced by the refinement of IMC particles in the solder and the reduced growth rate of interfacial IMCs by adding TiO2 nanoparticles.

Reliable electrical performance of β-Ga2O3 Schottky barrier diode at cryogenic temperatures

Electrical and trap characteristics of a large-size (2 × 2 mm2) β-Ga2O3 Schottky barrier diode (SBD) from 50 to 350 K have been reported. The ideality factor (n) decreases from 1.34 to nearly unity as temperature rises from 50 to 350 K, demonstrating near-ideal Schottky characteristics. The leakage current at cryogenic temperature (100 K) was significantly suppressed, indicating excellent off-state blocking performance at low temperatures. The weak temperature dependence of the carrier concentration (NS) and Schottky barrier height (ΦB) infers stable electrical characteristics of the β-Ga2O3 SBD. The stressed current density-voltage (J-V) and on-the-fly measurements reveal reliable dynamic performance under harsh low temperature conditions. Via deep-level transient spectroscopy, an electron trap, which is related to the dynamic performance instability and Lorentzian hump in low frequency noise spectra, is revealed for a β-Ga2O3 epilayer. The study reveals enormous potential of the utilization of a large-size β-Ga2O3 SBD for extreme temperature environments.

Powering for Long Term Monitoring in the Enclosed Areas

Paper presents possible solution and practical examples for wireless powering and signal transfer using the inductive coupling. It can be suitable for long term monitoring in enclosed areas and systems that are isolated form the surroundings. This solution allows avoiding the batteries. It can be used for probes bricked in to the wall, extreme temperature environment measurement, the barrels internal shells health monitoring etc. Main advantage of this kind of powering is nearly unlimited lifetime, no toxic pollutions (such as Cd, Li, H2SO4,… contained in the batteries) and universal applicability. The powering is provided by the near magnetic field. The resonance is considered in the design for increasing the voltage transfer. Also the passive signal transfer can be performed using this principle while it is similar to the RFID systems (Radio Frequency Identification). The main contribution of this paper is prediction of the powering potentialities and distance limits of this strategy. Voltage levels, power transfer efficiency and signal modulation effects are studied up to distance of 30 cm. The simple coils are considered. Also special converter principle is presented for this purpose.

Modeling of temperature effect on DC characteristics of microwave GaN devices

Due to the advantages of high power density, high efficiency, and great potential in extreme temperature environments, the GaN high electron mobility transistor (HEMT) device is widely used in circuit systems at high or low temperatures. However, its electrical performance is sensitive to the ambient temperature. Therefore, it is essential to build a model that can accurately characterize the electrical performance of GaN HEMTs at different ambient temperatures, which is also essential for precise circuit design. With the analysis of experiment and theory on the GaN HEMT at different ambient temperatures, an improved model for temperature effect on the DC characteristics of the GaN HEMT is proposed based on EEHEMT model. Considering the influence of the ambient temperature on electrical properties of the GaN HEMT, such as the threshold voltage, the knee voltage, and the saturated current, the model establishes a temperature-dependent function for key parameters in the formula of the drain-source current. Through Verilog-A implementation and simulation on the ICCAP software, the improved model accurately reflects the trend of the electrical performance changes of the GaN HEMT at different ambient temperatures. To further verify the model in this work, the on-wafer measurements at different temperatures including –55, –25, 25 and 75 ℃ are carried out for GaN HEMTs with different sizes, which are developed by Nanjing Electronic Devices Institute. Compared with the measured data, the output characteristics and the transfer characteristics simulated by the proposed model are accurate in an ambient temperature range of –55–75 ℃, with a relative fitting error less than 5%. The result shows that the improved model is of guiding significance in analyzing the direct current performance and high reliability design of circuits at different temperatures.

TiO2/SiO2 spiral crimped Janus fibers engineered for stretchable ceramic membranes with high-temperature resistance.

The tensile brittleness of ceramic nanofibrous materials makes them unable to withstand the relatively large fracture strain, greatly limiting their applications in extreme environments such as high or ultra-low temperatures. Herein, highly stretchable and elastic ceramic nanofibrous membranes composed of titanium dioxide/silicon dioxide (TiO2/SiO2) bicomponent spiral crimped Janus fibers were designed and synthesized via conjugate electrospinning combined with calcination treatment. Owing to the opposite charges attached, the two fibers assembled side by side to form a Janus structure. Interestingly, radial shrinkage differences existed on the two sides of the TiO2/SiO2 composite nanofibers, constructing a helical crimp structure along the fiber axis. The special configuration effectively improves the stretchability of TiO2/SiO2 ceramic nanofibrous membranes, with up to 70.59% elongation at break, excellent resilience at 20% tensile strain and plastic deformation of only 3.48% after 100 cycles. Additionally, the relatively fluffy ceramic membranes constructed from spiral crimped Janus fibers delivered a lower thermal conductivity of 0.0317 W m-1 K-1, attributed to the increased internal still air content. This work not only reveals the attractive tensile mechanism of ceramic membranes arising from the highly curly nanofibers, but also proposes an effective strategy to make the ceramic materials withstand the complex dynamic strain in extreme temperature environments (from -196 °C to 1300 °C).

A Step Towards the Impossible – the Combination of High Ionic Conductivity and Mechanical Stability in Highly Crystalline Solid Polyketone Electrolytes

Implementation of solid polymer electrolytes (SPEs) is believed to be one pathway forward in the development of lithium-metal batteries (LMBs) that are both safe and possesses high capacities. This combination is possible since the free-standing SPE maintains its mechanical integrity during electrochemical and thermal exposure while utilizing lithium metal as the negative electrode, thus accessing the extremely high theoretical capacity of lithium metal. The main drawback for SPEs are however the poor ionic conductivity compared to the liquid electrolytes used in lithium-ion batteries today.[1] The low ionic conductivity for SPEs stems from the conduction mechanism of the ions, which is a slower process in SPEs compared to in liquid electrolytes. In general, the conductivity in SPEs are confined to the amorphous regions, where segmental motion of the polymer chains facilitates the ion transport; while the crystalline regions restrict the movements of the polymer chains and impairs the ion transport.[2] The highly crystalline polyketone poly(1-oxoheptamethylene) (POHM) is a material that has shown interesting characteristics for implementation as a SPE in batteries. In earlier studies, the polyketone revealed an extensive improvement of the ionic conductivity upon increasing the salt concentration, although the crystallinity remained with a high melting point.[3] Herein this study, the effect of the crystallinity on the characteristics and the performance was investigated further. To understand its effect, a second less hydrogenated version of POHM was synthesized, POHM-75, which is fully amorphous at high salt concentrations. The characteristics of the polyketones were in addition also compared with the more well-studied SPEs, that is polyethylene oxide (PEO) and poly(trimethylene carbonate) (PTMC). Focus of the presentation is on the interplay between the ionic conductivity and mechanical stability for the polyketones, for which something different to the normally observed tradeoff between the two properties is observed. The electrochemical performance of the polyketones are furthermore evaluated when implemented as SPEs in LMBs at extreme temperature environments, a possible application area for mechanically stable SPEs.[1] D. Zhou, D. Shanmukaraj, A. Tkacheva, M. Armand, G. Wang, Chem 2019, 5, 2326-2352.[2] M. A. Ratner, P. Johansson, D. F. Shriver, MRS Bulletin 2011, 25, 31-37.[3] T. Eriksson, H. Gudla, Y. Manabe, T. Yoneda, D. Friesen, C. Zhang, Y. Inokuma, D. Brandell, J. Mindemark, Macromolecules 2022, 55, 10940-10949. Figure 1

High performance polydimethylsiloxane elastomer for triboelectric nanogenerators in extreme environment

Safety is a great challenge in the fields of electronics, especially in the harsh environments. Triboelectric nanogenerators would provide an efficient way to harvest mechanical energy from environment and convert them into electrical energy. However, most conventional polymeric materials for TENGs are easily flammable in the fire condition and would intenerate under high temperature. All these properties greatly affect the application of TENG. Herein, a novel polydimethylsiloxane elastomer with conjugated benzene ring is proposed to fabricate the heat- and fire-resistant TENG for the first time. The existence of conjugated benzene ring guarantees the polydimethylsiloxane elastomer with excellent mechanical properties, outstanding anti-dripping, superior thermal stability and fire-resistance. The resultant TENG exhibits excellent electrical performance which is originated from the existence of Si-benzene group and high dielectric constant (3.9). And it could maintain 100 % and 80 % output voltage in the high temperature (300 °C) and high tensile strain (200 %). What’s more, the output voltage of the obtained TENG remains almost unchanged after 60 s combustion. Consequently, this work will offer a novel strategy for tailoring the TENGs toward a secure power generator and electronics with fire hazard reduction, and potential application in firefighting and extreme temperature environments.

Thermosensation and Temperature Preference: From Molecules to Neuronal Circuits in Drosophila.

Temperature has a significant effect on all physiological processes of animals. Suitable temperatures promote responsiveness, movement, metabolism, growth, and reproduction in animals, whereas extreme temperatures can cause injury or even death. Thus, thermosensation is important for survival in all animals. However, mechanisms regulating thermosensation remain unexplored, mostly because of the complexity of mammalian neural circuits. The fruit fly Drosophila melanogaster achieves a desirable body temperature through ambient temperature fluctuations, sunlight exposure, and behavioral strategies. The availability of extensive genetic tools and resources for studying Drosophila have enabled scientists to unravel the mechanisms underlying their temperature preference. Over the past 20 years, Drosophila has become an ideal model for studying temperature-related genes and circuits. This review provides a comprehensive overview of our current understanding of thermosensation and temperature preference in Drosophila. It encompasses various aspects, such as the mechanisms by which flies sense temperature, the effects of internal and external factors on temperature preference, and the adaptive strategies employed by flies in extreme-temperature environments. Understanding the regulating mechanisms of thermosensation and temperature preference in Drosophila can provide fundamental insights into the underlying molecular and neural mechanisms that control body temperature and temperature-related behavioral changes in other animals.

Spark plasma sintering of HUST-1 lunar regolith simulant and its thermal shock resistance properties

The construction of lunar bases has become a new target for lunar exploration by many space powers worldwide. Sintered lunar regolith is one of the most promising building materials for in situ resource utilization (ISRU). Spark plasma sintering (SPS) technology has the advantageous features of a fast sintering speed and high density. This study explored the feasibility of sintering a HUST-1 lunar regolith simulant using SPS technology. The physical, mechanical, and thermal properties, as well as the microstructure and phase composition of the sintered samples were investigated at multiple scales. In addition, the effects of the SPS conditions on the sintering results were studied, including the sintering temperature, heating rate, and applied pressure. The test results indicated that the sintering conditions significantly affected the sintered products. Finally, the thermal shock resistances of the sintered samples were investigated at simulated lunar temperatures. The samples were treated at two different temperature ranges, one from −60 to 60 °C (±60 °C) and another from −120 to 120 °C (±120 °C). The results showed that the sintered samples exhibited excellent thermal shock resistance in the extreme temperature environment of the lunar surface. After 100 thermal test cycles at ± 60 °C and ± 120 °C, the compressive strength increased by 16.0 % and 33.4 %, respectively. The reason for the increase in strength remains unclear. The Brunauer-Emmett-Teller (BET) test results showed that this may be caused by the gradual disappearance of micropores smaller than 10 nm during thermal cycling.