Extreme Temperature Environments Research Articles

Effect of temperature on the properties of polymer cement composite material

AbstractIn the actual working environment for the polymer cement composite, the effect of temperature on its properties cannot be ignored. In order to investigate the properties of polymer cement composite in extreme temperature environment, this study conducted bond test, tensile test, and shear test of composites at different temperatures (−30, −15, 25, 40, and 60°C). Through measuring the elastic recovery rate of specimens, as well as relevant strength indexes, deformation indexes and energy consumption indexes under tensile and shear loads, the effect of temperature on the bond property, tensile property, and shear property of the composite were investigated. The results show that the polymer cement composite has a good bond property, and no damage occurs at any temperature or after cold drawing and hot pressing cycle. Temperature has a great influence on the tensile property and shear property of polymer cement composite. At a low temperature, the tensile property and shear property improve, the strength and energy consumption indexes increase noticeably, and the elongation at break increases while the peak strain reduces in terms of deformation indexes. At a high temperature, the tensile property and shear property deteriorate, and the strength, deformation, and energy consumption indexes all fall. As a result, the polymer cement composite is more suitable for cold areas.

Coaxial laser absorption and optical emission spectroscopy of high-pressure aluminum monoxide.

This work advances laser absorption spectroscopy with measurements of aluminum monoxide (AlO) temperature and column density in extreme pressure (P > 60 bar) and temperature (T > 4000 K) environments. Measurements of the AlO A2Πi-X2Σ+ transition are made using a microelectromechanical system, tunable vertical cavity surface emitting laser (MEMS-VCSEL). Simultaneous emission measurements of the AlO B2Σ+-X2Σ+ transition are made along a line of sight that is coaxial with the laser absorption. Absorption temperature fits agree with emission spectra for a T = 3200 K, P = 9 bar case. In cases with T > 4000 K, P > 60 bar, absorption fits match the ambient temperature while emission fits over-estimate it, owing to high optical depths. These data juxtapose passive and active spectroscopic methods and demonstrate the versatility of AlO laser absorption in high-pressure and high-temperature environments where experimental data remain scarce, and engineering models will benefit from refined measurements.

Correlation between d-orbital bandwidth and local coordination environment in RE2SiO5 compounds with implications in minimizing the coefficient of thermal expansion anisotropy (RE = Sc, Y, La)

Y2SiO5 is one of the promising environmental barrier coating (EBC) materials that protect the gas turbine engine components from unfavorable reactions at higher temperatures. The Y2SiO5 compound forms in the monoclinic crystal structure (C2/c space group), and one of the drawbacks is its appreciable coefficient of thermal expansion (CTE) anisotropy, which adversely affects its lifetime as the EBC material. The objective of this work is to uncover previously unknown correlation between the electronic structure and crystal structure of RE2SiO5 compounds in the equilibrium and hypothetical C2/c structures (where RE = Sc, Y, or La). Our density functional theory calculations reveal a trend in the RE-cation d-orbital bandwidth as a function of the RE electronic configuration, local RE–O coordination environment, and unit cell volume. We predict that the Y-4d orbital bandwidth can become narrower when Y2SiO5 forms in an open structure with a reduced Y–O effective coordination number. We conjecture that a narrow Y-4d orbital bandwidth may give rise to smaller CTE anisotropy compared to Y2SiO5 in its equilibrium structure. The outcome of this work has potential implications in the rational design of Y2SiO5-based EBCs for use under extreme temperature environments.

Performance Comparison of CdTe:Na, CdTe:As, and CdTe:P Single Crystals for Solar Cell Applications.

We compared thermal stability, open-circuit voltage, short-circuit current, and fill factor values of single-crystal Cadmium telluride (CdTe) grown using the vertical Bridgman (VB) technique and doped with group V elements (phosphorus and arsenic), and group Ⅰ element (sodium), followed by an annealing process. The sodium-doped CdTe maintained a hole density of 1016 cm−3 or higher; after annealing for a long time, this decreased to 1015 cm−3 or less. The arsenic-doped CdTe maintained a hole density of approximately 1016 cm−3 even after the annealing process; however its bulk minority carrier lifetime decreased by approximately 10%. The phosphorus-doped CdTe maintained its properties after the annealing process, ultimately achieving a hole density of ~1016 cm−3 and a minority carrier lifetime of ~40 ns. The characteristics of a single-crystal solar cell were evaluated using a solar cell device that contained single-crystal CdTe with various dopants. The sodium-doped sample exhibited poor interfacial properties, and its performance decreased rapidly during annealing. The samples doped with group V elements exhibited stable characteristics even during long-term annealing. We concluded, therefore, that group V elements dopants are more suitable for CdTe single-crystal-based solar cell applications involving thermal stress conditions, such as space missions or extreme fabrication temperature environments.

The mechanical and structural properties of lunar regolith simulant based geopolymer under extreme temperature environment on the moon through experimental and simulation methods

The lunar regolith simulant based geopolymer was prepared, and its mechanical and structural properties under extreme temperature were investigated. Results show 7-day compressive strength of geopolymer cured at 60℃ was 58.8 MPa. After laboratory tests under extreme temperature, compressive strength of geopolymers under 120℃ and −30℃ were above 50.0 MPa and 80.0 MPa respectively. The extreme temperature resistance of geopolymers could be understood by the simulation results in terms of molecular structure stability, which reveals the stable aluminosilicate structures under lunar high temperatures and under ultra-low temperatures. After 40 cycles of thermal shocks (-196℃-25℃), compressive strength of geopolymer even increased explained by relatively dense microstructures through SEM and BET. The geopolymer based lunar concrete has demonstrated a great potential for in-situ lunar base construction.

Magnet-assisted selective oil removal from water in non-open channel and continuous oil spills clean-up

• A superhydrophobic-superoleophilic, magnetic foam is synthesized. • The foam can selectively remove oil from water in both open and non-open environment. • The foam can be reused for multicycle oil adsorption, and shows long-term durability. • A novel magnetic attraction strategy is proposed to assemble the foam. 3D porous superhydrophobic materials have been widely developed for selective oil adsorption from open water surface, but it is still challenging for the oil removal from water in non-open environment. Herein, a superhydrophobic-superoleophilic, magnetic and 3D porous carbon-based foam, containing carbon-nanosheet frameworks (CNFs), iron/iron carbide nanoparticles (Fe/Fe 3 C NPs) and polydimethylsiloxane (PDMS) coating, is synthesized via ferric nitrate assisted chemical blowing and carbonization of polyvinylpyrrolidone (PVP), and post-treatment by PDMS. The PDMS-CNF-Fe/Fe 3 C foam shows low density (<90 mg cm −3 ), extremely high compressive strength (≈47.7 kPa) and selective oil removal ability with high oil adsorption capacity (>2700% for chloroform). The remarkable paramagnetic property of the foam enables it to be capable of removing oil selectively from water in non-open channels under assistance of a magnet bar. Additionally, the foam can be easily reused for oil adsorption by heating or releasing in other solvents with negligible adsorption capacity decline. The chemically stable carbon-based matrix and PDMS coating impart the foam with excellent high/low temperature stability and certain corrosion resistance, which facilitate effective oil removal from caustic aqueous solutions (especially in alkaline and salty conditions) or under extreme temperature environment. The 3D porous and self-similar micro structures enable the foam to be mechanical abrasion resistant, and the foam retains its water repellence and oil adsorption capacity after repeated and intensive abrasion by sandpaper. Moreover, we propose to assemble the foam with a vacuum pumping system by ring-shaped magnet to realize continuous oil removal. The mechanochemically durable PDMS-CNF-Fe/Fe 3 C foam with magnetic response capacity and outstanding reusability is therefore a promising candidate for selective oil removal from water in both open and non-open environments under remote control of magnet. The novel magnet assisted assembly strategy also provides a simple, reliable and automatable method to integrate magnetic 3D oil adsorbent with pumping system for large-scale oily wastewater remediation.

Optical transmission and dimensional stability of single-crystal sapphire after high-dose neutron irradiation at various temperatures up to 688 °C

The use of single-crystal sapphire optical fibers has been considered to extend fiber-optic sensing to the extreme temperature (>1000 °C) environments encountered in nuclear applications. However, before these sapphire fiber–based sensors can be deployed, their optical transmission and dimensional stability (which impacts drift of some sensors) must be characterized under representative testing conditions. Data regarding the optical transmission of sapphire following high-dose neutron irradiation at temperatures >100 °C is extremely limited. This work provides measurements of optical density (i.e., attenuation) and directional dimensional changes in bulk single-crystal sapphire materials irradiated to a fast neutron fluence of 2.4 × 10 21 n/cm 2 (3.5 displacements per atom) at temperatures ranging from 95 to 688 °C. Optical density measured after irradiation at 95 and 298 °C showed ultraviolet and visible absorption bands corresponding to known defect centers and temperature trends that were generally consistent with previous ex situ and in situ measurements made at much lower neutron fluence. However, optical density measured after irradiation at 688 °C was as much as two orders of magnitude higher, indicating that the fundamental mechanism for radiation-induced attenuation changes at this irradiation temperature. Additional analysis and comparison with previous works suggest that the attenuation may result from void formation, leading to increased Rayleigh scattering losses in the material and increased swelling that would also result in drift of Bragg grating-based sensors in sapphire fibers. These results pose serious questions regarding the feasibility of sapphire fiber–based sensors for high-temperature nuclear applications.

All-water-based superhydrophobic coating with reversible wettability for oil-water separation and wastewater purification

Superhydrophobic surfaces with reversible switchable wettability have great application value in the treatment of oily wastewater. However, the advancement of switchable wettability surfaces is limited by the complexity of the manufacturing process and the excessive use of environmentally unfriendly solvents. Herein, an all-water-based reversible wettability coating was fabricated by simply spraying a water suspension consisting of N-[3-(trimethoxysilyl) propyl] ethylenediamine (AS)-, 3-(trimethoxysilyl) propyl methacrylate (KH-570)-, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FAS)-modified titanium dioxide (TiO2) nanoparticles and cellulose. The coating possesses good adhesion with various substrates and exhibits stable mechanical and chemical stability as well as good resistance to harsh environments such as various organic solvents, strongly corrosive environments and extreme temperature environments. The coating can be switched between having superhydrophobicity (160°) and superhydrophilicity under UV irradiation and heating treatment. The coated cotton fabric can separate heavy/light oil-water mixtures and water-in-oil/oil-in-water emulsions with a high efficiency of greater than 95%. Due to the photocatalytic properties of TiO2, the coating can degrade soluble pollutants in water during UV irradiation, and the degradation efficiency is over 97%. This study provides a green industrial route for designing a simple, switchable wettability coating, which is expected to promote the large-scale industrial production and application of functional smart surfaces.

Research Progresses on Reliability of Sn-based Solder Joints in Extreme Temperature Environment

Research Progresses on Reliability of Sn-based Solder Joints in Extreme Temperature Environment

Effect of Temperature on Damping Performance for Wire Mesh Damper Made of Ni-Ti Shape Memory Alloy

Wire mesh dampers (WMDs) are known as a vibration suppression device for a rocket engine turbopump. The advantages of the WMDs are extreme temperature environment and oil-free operation. Recently, many studies are conducted about the damping performance, effect of material, and effect of design variables for the WMDs. The purpose of this study is to elucidate the effect of temperature on damping performance for WMD made of Nickel-Titanium (Ni-Ti) shape memory alloy. Since the WMD have different crystal structures depending on the temperatures, it is necessary to consider the temperature dependence of the damping performance. This paper presents the damping performance of the WMD due to phase transformation by forced vibration tests using one-dimensional exciter with heating. Result shows that energy dissipation of Ni-Ti WMD from hysteresis loop was decreased with increase of temperature, although dynamic stiffness was increased. The reason is considered that phase transformation of Ni-Ti shape memory alloy was occurred from martensite to austenite due to heating. Thus, the stiffness of the material increases, and the damping performance decreases as the temperature of WMD rises.

Development of Sapphire Optical Temperature Sensing System Used in Harsh Environment Sensing

A sapphire optical fiber blackbody radiation sensor based on the high temperature multilayer structure of wolfram and aluminum oxide has been developed. Through the analysis of Planck&#x2019;s law, the linear relationship between the temperature and the square root of the voltage is theoretically deduced. Radio frequency magnetron sputtering method is used to sputter and deposit high-temperature wolfram metal film and aluminum oxide film on sapphire fiber. In order to meet the needs of real-time temperature measurement, an online acquisition system of optical signals is designed to complete the demodulation and storage of signals. The high-temperature experiment results show that the temperature response sensitivity is 0.00113V1/2/&#x2103; between 300&#x2103; and 1750&#x2103;, and it can work stably for more than 10 hours. The sensor is calibrated in the metrology institute where a maximum quoted error of 0.84% within a range between 900 &#x2103; and 1600&#x2103; is proved. Compared with the traditional high temperature measurement method, the sensor has the advantages of compact structure, anti-electromagnetic interference, large measuring range, and good linearity, which can be widely used in the sensing and measurement of extreme high temperature environments such as aero-engine tail injection temperature monitoring, combustion chamber temperature monitoring of aero-engine simulation test benches.

A fractional model and its application to heat prevention coating with cocoon-like hierarchy

In this paper, a fractional model is established by using the variational iteration method to elucidate the thermal properties of building prevention coating with a cocoon-like hierarchy. The fractal hierarchical structure of heat prevention coating makes the building wall mathematically adapted for an extreme temperature environment. This work has inspired the bionic design of protective suits and extreme temperature clothing.

Structure of Molten Alkali Chlorides at Charged Interfaces and the Prediction and Interpretation of Their X-ray Reflectivity

The fundamental properties of molten salts have been the subject of research that spans a century. Yet, in the past few years, there has been an unprecedented surge in interest for these systems in the bulk and under confinement by walls and interfaces including under applied potentials. This is driven by the prospect of exciting and very practical energy technologies, including those in the solar and nuclear fields. This article sets to answer two simple but fundamental questions. How does the liquid structure of alkali chlorides change at a real interface when it is charged? Also, how would such changes on the liquid side of the interface be detected in X-ray reflectivity experiments? We use an interface mimicking conductive diamond, which because of its lattice spacing, is an excellent choice for reflectivity experiments. The reason for our interest in X-ray reflectivity is that, as opposed to electrochemical measurements alone, this is likely the only technique in which atomic level information at the liquid side of the interface can be gained under the extreme temperature environments of molten salts. As it will become apparent, the interpretation of reflectivity results in terms of atomic positions is complex when multiple species with different X-ray contrasts on the liquid side are considered. A theoretical scheme termed “the peaks and antipeaks analysis of reflectivity” originally introduced in our prior work (J. Phys. Chem. C 2019, 123 (8), 4914–4925) is expanded to interpret the structural changes at the interface as a function of applied electrical bias.

Atomic-Scale Hidden Point-Defect Complexes Induce Ultrahigh-Irradiation Hardening in Tungsten.

Tungsten displays high strength in extreme temperature and radiation environments and is considered a promising plasma facing material for fusion nuclear reactors. Unlike other metals, it experiences substantial irradiation hardening, which limits service life and presents safety concerns. The origin of ultrahigh-irradiation hardening in tungsten cannot be well-explained by conventional strengthening theories. Here, we demonstrate that irradiation leads to near 3-fold increases in strength, while the usual defects that are generated only contribute less than one-third of the hardening. An analysis of the distribution of tagged atom-helium ions reveals that more than 87% of vacancies and helium atoms are unaccounted for. A large fraction of helium-vacancy complexes are frozen in the lattice due to high vacancy migration energies. Through a combination of in situ nanomechanical tests and atomistic calculations, we provide evidence that irradiation hardening mainly originates from high densities of atomic-scale hidden point-defect complexes.

Enhancement of thermal shock resistance in β-Si3N4 coating with in situ synthesized β-Si3N4 nanowires/nanobelts on porous Si3N4 ceramics

A dense β-Si3N4 coating toughened by β-Si3N4 nanowires/nanobelts was prepared by a combined technique involving chemical vapor deposition and reactive melt infiltration to protect porous Si3N4 ceramics in this work. A porous β-Si3N4 nanowires/nanobelts layer was synthesized in situ on porous Si3N4 ceramics by chemical vapor deposition, and then Y–Si–Al–O–N silicate liquid was infiltrated into the porous layer by reactive melt infiltration to form a dense composite coating. The coating consisted of well-dispersion β-Si3N4 nanowires/nanobelts, fine β-Si3N4 particles and small amount of silicate glass. The testing results revealed that as-prepared coating displayed a relatively high fracture toughness, which was up to 7.9 ± 0.05 MPa m1/2, and it is of great significance to improve thermal shock resistance of the coating. After thermal cycling for 15 times at ΔT = 1200 °C, the coated porous Si3N4 ceramics still had a high residual strength ratio of 82.2%, and its water absorption increased only to 6.21% from 3.47%. The results will be a solid foundation for the application of the coating in long-period extreme high temperature environment.

Ketamine Stability over Six Months of Exposure to Moderate and High Temperature Environments

Background: All medications should be stored within temperature ranges defined by manufacturers, but logistical and operational challenges of prehospital and military settings complicate adherence to these recommendations. Lorazepam and succinylcholine experience clinically relevant heat-related degradation, whereas midazolam does not. Because ketamine’s stability when stored outside manufacturer recommendations is unknown, we evaluated the heat-related degradation of ketamine exposed to several temperature ranges. Methods: One hundred twenty vials of ketamine (50 mg/mL labeled concentration) from the same manufacturer lot were equally distributed and stored for six months in five environments: an active EMS unit in southwest Ohio (May-October 2019); heat chamber at constant 120 °F (C1); heat chamber fluctuating over 24 hours from 86 °F-120 °F (C2); heat chamber fluctuating over 24 hours from 40 °F-120 °F (C3); heat chamber kept at constant 70 °F (manufacturer recommended room temperature, C4). Four ketamine vials were removed every 30 days from each environment and sent to an FDA-accredited commercial lab for high performance liquid chromatography testing. Data loggers and thermistors allowed temperature recording every minute for all environments. Cumulative heat exposure was quantified by mean kinetic temperature (MKT), which accounts for additional heat-stress over time caused by temperature fluctuations and is a superior measure than simple ambient temperature. MKT was calculated for each environment at the time of ketamine removal. Descriptive statistics were used to describe the concentration changes at each time point. Results: The MKT ranged from 73.6 °F-80.7 °F in the active EMS unit and stayed constant for each chamber (C1 MKT: 120 °F, C2 MKT: 107.3 °F, C3 MKT: 96.5 °F, C4 MKT: 70 °F). No significant absolute ketamine degradation, or trends in degradation, occurred in any environment at any time point. The lowest median concentration occurred in the EMS-stored samples removed after 6 months [48.2 mg/mL (47.75, 48.35)], or 96.4% relative strength to labeled concentration. Conclusion: Ketamine samples exhibited limited degradation after 6 months of exposure to real world and simulated extreme high temperature environments exceeding manufacturer recommendations. Future studies are necessary to evaluate ketamine stability beyond 6 months.

Failure analysis on rubber sealing structure of mandrel hanger and improvement in extreme environments

In view of the failure of the sealing structure of mandrel hanger under high pressure and extreme temperature environment, according to the sealing structure characteristics and application requirements of conventional mandrel hanger, based on the principle of the minimum sealing pressure ratio of metal sealing surface and the constitutive model of rubber material, the advantages and disadvantages of three conventional sealing structures are analyzed and compared. Based on the heat conduction theory and the energy conservation equation of thermal coupling, the transient temperature field model of the hanger seal structure is established. The heat transfer analysis and thermo-mechanical coupling calculation of the new metal seal structure are carried out at extreme temperature. The results show that the contact pressure on the double U and single U sealing rings is greater than 140 MPa at extreme temperature, which meets the principle of minimum sealing pressure ratio. The temperature distribution law of the conventional rubber structure under the temperature and pressure load is analyzed, and the reason of early failure of rubber is found. The mandrel hanger of full metal sealing structure is used in the field. The mandrel hanger of full metal have been tested for more than 20 times of gas pressure. The pressure is stable and the sealing effect is good. The test results show that this new structure has the advantages of good seal performance.

Research on Testing Methods of Temperature Strain and Force Strain under Extreme Temperature Environment

The traditional quartz differential method and the half-bridge connection temperature compensation test method are improved to realize the effective separation of the physical deformation of the material caused by the temperature effect and the deformation caused by the load under the coupling effect of temperature and load, so as to be the thermal expansion coefficient of the material at extreme temperatures And provide the basis for the test and determination of mechanical performance parameters.

Crack growth behavior and thermal shock resistance of ceramic sandwich structures with an auxetic honeycomb core

This paper developed a thermal–mechanical analysis model to describe the thermal shock behavior of ceramic sandwich structures (CSSs) with an auxetic honeycomb core. The transient temperature distribution and the associated thermal stress field of CSSs subjected to a thermal shock were determined. The crack growth behavior was discussed based on the thermal stress intensity factor (TSIF), crack location, face-sheet thickness, and internal cell orientation of the honewycomb core in detail. The results revealed that the auxetic and non-auxetic honeycomb cores have the similar temperature distribution profile however the auxetic honeycomb core can substantially reduce the overall thermal stress level. Furthermore, by equating the maximum TSIF and equivalent fracture toughness, the critical temperature for which the honeycomb core can sustain without failure was obtained. The results showed that CSSs with auxetic honeycomb core possessed a higher thermal shock resistance than that of non-auxetic. This research work was the first attempt to identify the the thermal shock resistance of CSSs with an auxetic honeycomb core. The results would provide fresh insight into the design and selection of CSSs applied in an extreme temperature environments.

Enhanced energy storage properties of thermostable sandwich-structured BaTiO3/polyimide nanocomposites with better controlled interfaces

The energy density of polymers for high temperature applications is still relatively low. Among them, polyimide (PI) is one of the most attractive matrixes because of its high thermal stability. Instead of the mono thermal imidization method to fabricate multilayer PI nanocomposites in the literature, a novel method was proposed herein to better control the multilayer morphology, which could help to further enhance the energy storage properties. The method's effect on the morphology especially on the interfaces between adjacent layers was studied, and then the mechanism of breakdown strength change was discussed by a proposed model based on bipolar charge transport. The sandwich-structured PI nanocomposites, composed of the middle polarization layer with high BaTiO3 (BT) content and the two outer insulation layers with low BT content, were fabricated. Enhanced breakdown field and discharged energy density of 550 kV/mm and 5.1 J/cm3 with the efficiency of about 70% were achieved, while keeping a high thermal stability (500 kV/mm and 3.9 J/cm3 at 100 °C). This work presents a promising polymer nanocomposite for energy storage capacitors especially in extreme temperature environments, and a new concept to fabricate multilayer dielectric composites.