High-temperature Devices Research Articles

Research on Pt-Based Film Negative Photoconductivity Photothermal Detector Under Different Wavelength Laser Irradiation

Platinum (Pt) is a rare and precious metal element with numerous unique properties. These properties have led to the widespread use of Pt in electronic components, thermocouples, and high-temperature devices. In this study, we present the bolometric effect of single-metal Pt-based negative photoconductivity (NPC) devices under the laser irradiation of 375 nm, 532 nm, and 808 nm. Under the condition of applying 0.5 V voltage, the responsivity (R) of the Pt photothermal detector (Pt-PTD) under 375 nm laser irradiation was 69.14 mA/W, and the specific detectivity (D*) was 5.38 × 107 Jones; the R of the Pt-PTD under 532 nm laser irradiation was 59.46 mA/W, and the D* was 4.61 × 107 Jones; the R of the Pt-PTD under 808 nm laser irradiation was 37.88 mA/W, and the D* was 2.95 × 107 Jones. Additionally, a single-site scanning imaging system based on a Pt-PTD was designed to test the capability of the device. This study provides a strategy for the development of thermal measurement detectors based on Pt materials.

Interface engineering of van der Waals heterostructures towards energy-efficient quantum devices operating at high temperatures

Abstract Quantum devices, which rely on quantum mechanical effects for their operation, may offer advantages, such as reduced dimensions, increased speed, and energy efficiency, compared to conventional devices. However, quantum phenomena are typically observed only at cryogenic temperatures, which limits their practical applications. Two-dimensional materials and their van der Waals (vdW) heterostructures provide a promising platform for high-temperature quantum devices owing to their strong Coulomb interactions and/or spin-orbit coupling. In this review, we summarise recent research on emergent quantum phenomena in vdW heterostructures based on interlayer tunnelling and the coupling of charged particles and spins, including negative differential resistance, Josephson tunnelling, exciton condensation, and topological superconductivity. These are the underlying mechanisms of energy-efficient devices, including tunnel field-effect transistors, topological/superconducting transistors, and quantum computers. The natural homojunction within vdW layered materials offers clean interfaces and perfectly aligned structures for enhanced interlayer coupling. Twisted bilayers with small angles may also give rise to novel quantum effects. In addition, we highlight several proposed structures for achieving high-temperature Majorana zero modes, which are critical elements of topological quantum computing. This review is helpful for researchers working on interface engineering of vdW heterostructures towards energy-efficient quantum devices operating above the liquid nitrogen temperature.

DFT study of structural, electronic, optical and elastic properties of lead-free Bi based perovskites X2NaBiCl6 (X= K and Rb) with pressure

The pressure dependent structural, electronic, optical and mechanical properties of Bi-based cubic halide double perovskites, X2NaBiCl6 (X = K and Rb) are explored by implementing full-potential linearized augmented plane wave (FP-LAPW) method. At zero pressure, K2NaBiCl6 and Rb2NaBiCl6 posses indirect band gaps of 3.746 and 3.735eV, respectively and the band gaps decrease with increasing pressure for both compounds. The elliptical shape of charge density contours under high pressure ensured a strong covalent bonding between K/Rb and Cl atoms along (110) plane. We explored the essential optical properties for both compounds with different pressures and found a red-shift with increase in pressure. Furthermore, all the values of mechanical parameters, viz. elastic constants and moduli, Vickers hardness, Debye and melting temperatures are enhanced with increasing pressure. Due to suitable band gaps and appropriate mechanical parameters, both perovskites are proved as promising candidates in thermoelectric power generation and high temperature devices.

Simultaneously Achieved High Piezoelectricity and High Resistivity in Na0.5Bi4.5Ti4O15-Based Ceramics with High Curie Temperature.

Good piezoelectricity and high resistivity are prerequisites for high-temperature acceleration sensors to function correctly in high-temperature environments. Bismuth layered structure ferroelectrics (BLSFs) are promising candidates for piezoelectric ceramics with excellent piezoelectric performance at high temperatures, high electrical resistivity, and high Curie temperatures (Tc). In this study, (LiMn)5+ is substituted for Bi at the A-site, and Ce-doping is performed to replace Ti ions in Na0.5Bi4.5Ti4O15, which achieves the desired combination of high piezoelectric coefficients and high resistivity. Herein, we prepared Na0.5Bi3(LiMn)0.9Ti4-xCexO15 high-temperature piezoelectric ceramics, achieving a high piezoelectric coefficient d33 of 32.0 pC/N and a high resistivity ρ of 1.2 × 108 Ω·cm (at 500 °C), and a high Curie temperature of 648 °C. It is important that the d33 variation remains within 8% over a wide temperature range from 25 °C to 600 °C, demonstrating excellent thermal stability. Structural characterization and microstructure analysis showed that the excellent piezoelectric coefficient and high resistivity of cerium-doped Na0.5Bi4.5Ti4O15-based ceramics are attributable to the synergistic effects of structural characteristics, defect concentration, refined grain size and domain morphology. This study demonstrates that the superior properties of Na0.5Bi3(LiMn)0.9Ti4-xCexO15 ceramics are crucial for the stable operation of high-temperature accelerometer sensors and for the development of high-temperature devices.

Phonon confinement in TiO2 sandwiched MOF particles for high temperature dielectric energy storage

For promising energy storage applications, high surface area materials containing both ionic and organic components are ideal candidates. While Metal Organic Frameworks (MOFs) exhibit the desired characteristic, they generally lack high-temperature structural stability observed in conventional inorganic metal-based compounds. Here we propose a novel composite material comprising TiO2- incorporated and encapsulated carbonized ZIF-67 (TZT), showing stable dielectric and energy storage performance at elevated temperatures than other MOF composites. By integrating TiO2 within the ZIF-67 framework, the composite achieves significant phonon confinement for enhanced dielectric polarization, with permittivity achieving a value of 50, while the external coating gives the imidazole structure temperature sustainability. The current density shows a prominent increase with the increase of temperature and frequency and hence lowering of activation energy and Schottky barrier potential, that results in a prominent rise of polarization with respect to electric filed. The study elucidates the underlying mechanisms of phonon-modulated polarization dynamics, demonstrating dual Debye relaxations at low temperatures and Maxwell-Wagner relaxations at high temperatures. These findings highlight the crucial role of phonon dynamics in enhancing the energy storage capabilities and dielectric performance of the composite material, making TZT a superior candidate for advanced high-temperature energy storage devices.

Oxygen nonstoichiometry, defect chemistry and thermodynamic modeling of donor-doped CaMnO3−δ: Effect of disproportionation of Mn3+ ions in nonstoichiometric manganites

The present study concerns the investigation of the oxygen content in the perovskite-type manganite Ca0.6−уSr0.4HoуMnO3−δ (0 ≤ y ≤ 0.15) as a function of temperature (T) and oxygen partial pressure (pO2) in the gas phase since the oxygen nonstoichiometry (δ) has a significant impact on the physicochemical properties of materials applied in a variety of high-temperature devices. The δ value has been determined using thermogravimetry and coulometric titration methods. The resulting pO2 – T – δ diagrams have been accurately described by the defect chemical equilibrium model, that accounts for the oxidation reaction of Mn3+ to Mn4+ in all of the studied samples. Additionally, for the samples containing holmium, the disproportionation reaction of Mn3+ to Mn2+ and Mn4+ has been considered. This is the first study to demonstrate the distinction in Mn3+ disproportionation reactions in stoichiometric and nonstoichiometric Ca0.6−уSr0.4HoуMnO3−δ manganites, resulting from the discrepancy in oxygen coordination of Mn3+ ions at low and high temperatures. The experimental dependencies δ(T, pO2) have been employed in order to calculate the chemical potential of oxygen (ΔμO) in relation to the standard state. Statistical thermodynamic analysis has yielded equations that describe the relationships between the partial molar enthalpy (ΔhO) and entropy (ΔsO) of oxygen with standard enthalpies and entropies of defect formation reactions, Mn3+ ion concentration, and nonstoichiometry δ. The calculated functions ΔhO(y, δ, T) and ΔsO(y, δ, T) have been shown to exhibit a high degree of correlation with the values of ΔhO and ΔsO obtained from the linear dependencies of ΔμO on T.

Diamond Crystal Growth on Orientation-Controlled Carbon-Based Materials

Diamond is an excellent semiconductor material due to its wide band gap (5.45 eV), high mobility and high thermal conductivity. Diamond semiconductors are expected to be used in the construction of ultraviolet light-emitting devices, high-temperature devices and high-speed devices. Diamond have the potential to contribute to energy saving and miniaturization of various electrical products when diamond is widely used in practical applications. However, there are various problems in using diamond as a semiconductor. One of the problems is that size-limited and the high cost of the substrates in homoepitaxial growth used to fabricate high-quality diamond substrates. It is therefore preferable to establish a process for the fabricate of high-quality diamond substrate by heteroepitaxial growth.We used orientation-controlled graphite, an allotrope of diamond, as a substrate for diamond crystal growth. We present the results of our investigation into methods for diamond heteroepitaxial growth on graphite. Although there have been reported that of diamond crystal growth on graphite substrates after a pre-treatment. This is considered that this required pre-treatment because the crystal growth was on the plane of a honeycomb structure with hexagons lined up by carbon, and there were no bonding points. In the present study, crystals were grown without any pre-treatment process on the X-Y plane, where the configured by honeycomb structure, and on the Z plane, which intersects it at right angles and exposes the chemically active points as the dangling bonds. The effect of the orientation of the crystal growth substrate on diamond crystal growth was analyzed and the possibility of graphite substrates as diamond crystal growth substrates was examined.Here, it is considered that the dangling bonds on the Z-plane before crystal growth are terminated with hydrogen.In this study, polycrystalline diamond were fabricated on highly oriented pyrolytic graphite (HOPG) substrates using a microwave plasma chemical vapor deposition (MPCVD). The dependence of crystal size on raw gas ratio, deposition temperature, and substrate orientation was investigated. The raw gas ratio was fixed at CH4:H2 = 0.5:199.5 and the deposition temperatures were set at 600°C, 700°C, 800°C, 900°C and 980°C. The deposition pressure was kept constant at 10 kPa.The diamond crystal size deposited in the XY plane exceeded that deposited in the Z plane. The largest difference in crystal size was observed at a temperature of 980°C and a methane flow rate of 0.5, the crystal size in the XY and Z planes was 1.3311μm2 and 0.4232μm2, respectively, and the crystals in the XY plane were about three times larger than those in the Z plane. We attributed this change in crystal size due to the difference in substrate orientation to the distortion of part of the tetrahedral structure of diamond to match the hexagonal structure of graphite in the XY plane and the secondary bonding of the tetrahedral structure. In other words, although many active sites are exposed on the Z plane, the bonding distance of carbon atoms is not convenient for the generation of diamond crystals, and the hexagonal reticular structure of the XY plane is more convenient for the generation of crystals, so the diamond crystals on the XY plane are considered to have grown larger in these condition ranges. Figure 1

Electrolytic Extraction of Transition Metals from Lithium-Ion Cathodes in Molten Hydroxide Salts

We have developed an electrometallurgical recycling process that uses low melting temperature molten hydroxide salts to produce metals from lithium-ion battery materials. Existing commercial recycling processes typically use high temperatures, require high-purity reagents, and use coke as a reductant, which makes the processes expensive and CO2-emissions heavy1. Molten hydroxide salts can lower the required temperatures and emissions needed for extraction of critical materials from spent lithium-ion batteries.Molten hydroxide salts are water-tolerant, oxyanion-conducting, and can be used as electrolytes for electrochemical extractions2. This water tolerance is unique among molten salts and enables oxyanion-based electrochemical reactions through the Lux-Flood acid-base equilibrium: 2OH- ↔ H2O + O2- (1)Where water is the oxoacid and accepts oxyanions to form the hydroxide ion. Here, we leverage the unique properties of molten hydroxide electrolytes and demonstrate a one pot, two-step electrochemical extraction of critical metals from battery cathode materials. In the first step, lithium-ion cathodes are electrochemically reduced to form soluble oxides in the hydroxide melt. In the second step, the solubilized materials are reduced onto a separate cathode and recovered as an alloy. We will discuss test results for both process steps to recover Ni, Mn, and Co metal from both fresh NMC 622 and used cathode material (black mass). The effect of process conditions such as moisture content and operating parameters on the chemistry will be discussed. B. MAKUZA et al., “Pyrometallurgical options for recycling spent lithium-ion batteries: A comprehensive review,” J. Power Sources 491 February, 229622, Elsevier B.V. (2021); https://doi.org/10.1016/j.jpowsour.2021.229622.E. GÜRBÜZ et al., “Significance of Molten Hydroxides With or Without Molten Carbonates in High-Temperature Electrochemical Devices,” Front. Energy Res. 9 April, 1 (2021); https://doi.org/10.3389/fenrg.2021.666165.

Ultra-Low Temperature Epitaxy of Ge-Rich Nanosheets on SOI for Reconfigurable Transistor Applications

Implementing only tens of nanometer-thin Ge and Ge-rich SiGe nanosheets on SOI is expected to boost performance metrics of next-generation electronic devices, such as reconfigurable field effect transistors [1]. However, an inherent lattice mismatch between Ge and Si drastically limits the thickness of high-quality Ge layers on Si to a few monolayers, i.e., far too thin for practical nanosheet device applications. Thus, to date, many prototype Ge-rich nanoelectronics device concepts are based on nanowires' vapor-liquid-solid (VLS) growth. Since these nanowires grow on untypical (111) substrates and in a vertical manner, they need to be picked and placed onto Si(001) substrates: A serial process and, thus, barely scalable. Therefore, whenever two-dimensional nanosheets of a material are available, they provide distinct advantages with respect to the scalability of the device integration. Here, we show that pure Ge and SiGe alloyed nanowires can be formed top-down from nanosheets. We show that devices from nanowires based on Ge on SOI nanosheets have excellent quality and can outperform other material platforms, such as VLS nanowires or devices based on GeOI substrates, thereby enabling extended device functionalities [2].For high Ge contents and typical Ge growth temperature above 500°C, the achievable thickness of pseudomorphic, defect-free (Si)Ge epilayers is just a couple of monolayers if grown directly on Si(001) substrates [3,4]. Above this thickness, the inherent strain between the layer and SOI substrate leads to harmful plastic or elastic relaxation under common growth conditions.We depart from established (Si)Ge epitaxy temperatures of ≥500°C and employ molecular beam epitaxy (MBE) growth at ultra-low temperatures (ULT), ranging from 100°C to 350°C [5,6]. We show that the lowered surface kinetics leads to a pronounced layer supersaturation, allowing us to access layer thicknesses about an order of magnitude larger than previously reported values. Also, in contrast with previous results for ULT epitaxy [7], we do not observe layer amorphization even for growth at 100°C. Here, we highlight that pristine growth pressures deep in the ultra-high vacuum range (≤10-10 mbar) are crucial to keep the density of unwanted impurities in the (Si)Ge layers to a minimum and, thus, enable excellent electrical and optical properties of the grown heterostructures. These low growth pressures are particularly important in ULT growth since the low thermal budget impedes the efficient desorption of residual gas molecules from the substrate.We further show the fabrication of nanosheet transistors based on fully strained, defect-free (Si)Ge epilayers grown directly on SOI substrates [2,8,9]. For these devices, properties like thickness, SiGe(Sn) content, barrier material, and doping can be conveniently tuned during the epitaxy process beyond past limitations. We demonstrate that these nanosheets are a highly scalable platform for emerging devices, such as reconfigurable transistors with excellent performance [2,8,9] and highly symmetric n- and p-type transistor characteristics. Notably, the ULT-grown nanolayers withstand high-temperature device fabrication steps such as SiO2 formation and Al-SiGe exchange [2,8,9].

Effective phonon dispersion and low field transport in AlxGa1−xN alloys using supercells: An ab initio approach

To investigate the transport properties in random alloys, it is important to model the alloy disorder using supercells. Although computationally expensive, the local disorder in the system is accurately captured as translational symmetry that is imposed on the system over larger length scales. Additionally, in supercells, the error introduced by self-image interaction between the impurities is reduced. In this work, we have investigated the Effective Phonon Dispersion (EPD) and transport properties, from first principle calculations using supercells in AlxGa1−xN alloy systems. Using an in-house developed code for phonon-band unfolding, the EPD of AlGaN is obtained and the individual phonon modes are identified with good agreement with experimental values. Moreover, we report an in-house developed method to calculate low-field transport properties directly from supercells without phonon band unfolding. First, to validate our methods, we have solved the Boltzmann transport equation using Rode’s method to compare the phonon limited mobility in the 4 atom GaN primitive cell and 12 atom GaN supercell. Using the same technique, we have investigated the low field transport in random AlxGa1−xN alloy systems. The quadrupole interaction is included for transport properties of GaN and AlN to accurately capture the physics in these materials. Our calculations show that along with alloy scattering, electron–phonon scattering may also play an important role at room temperature and high-temperature device operation. This technique opens up the path for calculating phonon-limited transport properties in random alloy systems.

Spark plasma sintering of high-TC calcium bismuth niobate (CaBi2Nb2O9) with superior piezoelectric performance

Calcium bismuth niobate (CaBi2Nb2O9) is a promising ceramic material for high-temperature piezoelectric applications due to its high Curie temperature (TC) of 940 °C. However, its practical use is limited by poor piezoelectric performance and low direct-current (DC) electrical resistivity at elevated temperatures. In this study, we introduced pseudo-tetragonal distortion into CaBi2Nb2O9 by substituting rare-earth thulium ions, which reduced domain wall energy, facilitated domain switching, and decreased the presence of oxygen vacancies. These enhancements significantly improved both the piezoelectric performance and DC electrical resistivity of the material. To further enhance piezoelectric performance, we prepared textured thulium-substituted CaBi2Nb2O9 ceramics with a Lotgering factor (f) of up to 77.4 % using a two-step spark plasma sintering method. The resulting textured CaBi2Nb2O9 ceramics exhibited superior piezoelectric performance, with a piezoelectric constant d33 of 25.2 pC/N, four times higher than that of non-textured CaBi2Nb2O9. Importantly, these textured ceramics maintained excellent electrical properties at elevated temperatures, suggesting their suitability for high-temperature piezoelectric device applications.

Al-clad Cu bond wires for power electronics packaging: Microstructure evolution, mechanical performance, and molecular dynamics simulation of diffusion behaviors

With the advancement of power electronics, aluminum-clad copper thick bonding wires have garnered attentions due to superior electrical and thermal properties, making them well-suited for high-temperature and high-current applications. However, the impact remains unveiled of whether the growth of intermetallic compounds (IMCs) at the bonding interface presents critical challenges to the reliability of wedge wire bonds. Therefore, it is necessary to investigate the evolution behavior of Cu/Al IMCs in Al-clad copper wires. In this study, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were firstly employed to characterize the phase composition and growth behavior of Cu/Al intermetallic compounds (IMCs) at two distinct interfaces—the bonding interface and the core-shell interface—under various annealing conditions during high-temperature storage (HTS) tests, revealing a parabolic relationship between aging time and IMCs thickness. Subsequently, shear and pull tests of Al-clad copper bond wires were conducted to evaluate the bonding strength under different aging conditions, clarifying the correlation between various failure modes of the bonds and the evolution of IMCs at the bi-interfaces of this novel composite across different aging stages. Additionally, molecular dynamics (MD) simulations were employed to explore the diffusion behavior of Cu and Al atoms. It revealed that polycrystalline structures enhanced the mutual diffusion at the interface, with copper serving as the predominant element in the interdiffusion process. In conclusion, this study integrates experimental and numerical approaches to elucidate the growth mechanisms of Cu/Al intermetallic compounds and their effects on reliability, providing valuable guidance for optimizing the performance of composite bonding wires in high-temperature power device applications.

Water invasion and residual gas distribution in partially filled fractures via phase-field method

Water invasion is a significant factor affecting the conductivity of fractures in coal seams. The partially contact characteristics of deep coal seam fractures are pronounced, and surface wettability varies significantly. However, there is a limited understanding of how water invasion behavior in partially filled fractures affects the gas produced by these fractures. In this study, a high-temperature and high-pressure contact angle testing device was employed to assess the wettability of coal seams under in situ conditions. The geometry of partially filled fractures was reconstructed using random functions, while the phase field method was employed to calculate the interactions at the two-phase interface during water invasion. The results indicate that the deep coal seams in the Ordos Basin demonstrate weak air-wetting properties under in situ conditions. The partially contact characteristics of the filled fractures in the deep coal seams categorize the fractures into distinct pore and throat regions. The variations in connectivity levels lead to the gas exhibiting uninvaded, clustered, and fully invaded characteristics following water invasion. The change in gas saturation during water invasion is more sensitive to larger values of lgCa and higher cos(θ). A larger displacement pressure difference and a smaller contact angle enable the invasion fluid to penetrate smaller throats, resulting in a higher number of clusters of residual gas and a smaller cluster radius. The results enhance our understanding of water invasion behavior, and the variability of fracture surface properties and gas-water two-phase flow in deep coal seams deserves further investigation.

Temperature dependence of Ce luminescence characteristics in LaBr3: Ce crystal

Despite the large interest in the scintillation properties of LaBr3:Ce, a detailed understanding of the underlying mechanism of temperature-dependence properties of Ce luminescence remains elusive. This study introduces a self-designed spectral apparatus to explore these properties in LaBr3:5%Ce. We observed a redshift phenomenon and band changes in the emission peak bands, indicating a reduction of the bond length between Ce and the host with increasing temperature. Moreover, the probability of low-energy peak emission decreases and the probability of high-energy peak emission increases, with increasing temperature was observed, suggesting a correlation with the proximity of Ce's 4f energy level to the valence band. Utilizing intensity parameters from the spectra, we identified the impact of temperature on LaBr3:Ce's self-absorption effect, revealing a significant self-absorption effect at the high-energy peak for the first time. A simple self-absorption model indicated that, despite high quantum efficiency of Ce, the overall self-absorption is minimal, establishing a correlation between the self-absorption coefficient of the high-energy peak and overall absorption. This research offers insights for developing radiation-resistant high-temperature luminescent devices and advances the field of high-temperature luminescent materials.

Formation, migration, and removal mechanisms of PCDD/Fs throughout the temperature range (850°C–150°C) in a full-scale MSW incinerator: The invention of novel high-temperature PCDD/F sampling device

Polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) emitted from municipal solid waste (MSW) incineration have detrimental effects on the ecological environment. This study innovatively invented a high-temperature sampling device for PCDD/Fs, followed by a process tracing experiment conducted in a full-scale MSW incinerator to investigate the formation and migration mechanisms of PCDD/Fs throughout the temperature range (850°C–150°C). The results highlighted the considerable PCDD/F level of 0.446 ng I-TEQ Nm−3 at the @1 furnace outlet (850°C). The distribution characteristics of PCDD/Fs suggested a prevalence of high-temperature homogeneous reactions in the flue zone between sites @1 and #1 (850°C–600°C). In the low-temperature zone, de novo synthesis emerged as the dominant formation mechanism, primarily occurring near the @2 superheater outlet (∼368°C) and inside the SCR system (∼230°C). The impact and removal efficiency of individual air pollutant control devices on PCDD/Fs was systematically analyzed, yielding an overall PCDD/F reduction of 99.7%. Remarkably, the buffering effect of economizer, the co-removal of semi-dry deacidification system, and the adsorption-filtration effect of activated carbon injection and fabric filter individually reduced PCDD/F concentrations by 23.9%, 35.3%, and 99.7%, respectively; while de novo synthesis inside the SCR system negatively impacted PCDD/F removal, demonstrating an efficiency of −43.2%. Consequently, these comprehensive insights inspired industrial operation optimization and ultra-low PCDD/F emission control.

A Temperature-Sensitive Fluorescent Supramolecular Polymer Constructed by Discrete Platinum(II) Metallacycle and Pillar[5]arene-Based Host-Guest Interactions.

The application of thermosensitive fluorescent supramolecular polymers in advanced optical materials, chemical sensors, artificial optical devices, and external stimulus responses remains underdeveloped. In this study, we introduced a novel method for constructing a mechanically interlocked fluorescent supramolecular polymer utilizing host-guest interactions, including C-H···π interactions and π-π stacking. This polymer exhibits outstanding temperature-sensitive fluorescence properties and is environmentally friendly due to its recyclability. Leveraging the polymer's fluorescence response at critical temperature ranges, we developed a high-temperature warning device. This device utilizes the temperature-sensitive fluorescence characteristic of the polymer to indicate dangerous temperature levels, thereby demonstrating its potential in practical safety applications.

In the LiCl-KCl melt at 500<sup>о</sup>С depending on the content of Li<sub>2</sub>О и LiOH

Molten alkali metal chlorides used in pyrotechnologies are aggressive corrosive agents. The high operating temperature of the process, the heterogeneity of the environment, and the significant corrosion activity of the molten salt necessitate both the search for stable structural materials and the development of methods for protecting the structural elements of high-temperature technological devices. Corrosion loss reduction techniques traditionally used in low temperature environments are not applicable at high temperatures. The article examines the influence of oxygen-containing impurities (lithium oxide and hydroxide) on the corrosion behavior of metallic nickel (grade NP1) – the main component of candidate structural alloys, a thermodynamically and structurally stable material in the melt for the process of electrolytic refining of spent nuclear fuel. A method for preparing the LiCl–KCl salt electrolyte and obtaining lithium oxide by thermal decomposition of anhydrous lithium hydroxide under vacuum is described, and the concentrations of impurities in the electrolyte and the synthesized lithium oxide are determined. An installation for conducting corrosion tests in an inert atmosphere of a glove box is presented. To assess the corrosion resistance of the material, the following were used: gravimetric analysis, X-ray diffraction analysis of the surface and cross-sectional sections, and X-ray diffraction analysis of the surface of the samples. The dependences of the corrosion rate of the material on the concentration of oxygen-containing additives Li2O and LiOH were obtained. Based on a combination of gravimetric, X-ray microspectral and X-ray phase analysis data, it was established that metallic nickel samples demonstrate high corrosion resistance in the studied melts with the introduction of Li2O and LiOH additives.

Enhancing piezoelectric properties of BiScO3-PbTiO3 ceramics via- incorporation of Bi(Zn1/2Ti1/2)O3 with high spontaneous polarization

High-performance piezoelectric materials are the core elements for the fabrication piezoelectric transducers and actuators. In recent years, there has been an increasing demand for piezoelectric materials with both high operational temperature and large piezoelectricity. However, the conventional approach of soft doping to enhance the piezoelectric response often results in a reduction in Curie temperature. To address this issue, we incorporated Bi(Zn1/2Ti1/2)O3 with a large spontaneous polarization (Ps ∼ 100 µC/cm2) and high Curie temperature (Tc ∼ 1380 °C) into BiScO3-PbTiO3 ceramics to improve the piezoelectric response while maintaining high Tc. The newly developed 0.08Bi(Zn1/2Ti1/2)O3-0.335BiScO3-0.585PbTiO3 ceramic exhibits impressive properties including a high d33 value of 585 pC/N (increased by ∼ 33 % compared to the 0.36BiScO3-0.64PbTiO3 ceramics), an electromechanical coupling coefficient k33 of 0.75, a dielectric constant ε′ of 2380, a relatively high Tc of 421 °C. These remarkable improvements hold great promise for advancing high-temperature piezoelectric devices.

Novel Self-Assembling Supramolecular Phenanthro[9,10-a]phenazine Discotic Liquid Crystals: Synthesis, Characterization and Charge Transport Studies.

The incorporation of heteroatoms in the chemical structure of organic molecules has been identified as analogous to the doping process adopted in silicon semiconductors to influence the nature of charge carriers. This strategy has been an eye-opener for material chemists in synthesizing new materials for optoelectronic applications. Phenanthro[9,10-a]phenazine-based mesogens have been synthesized via a cyclo-condensation pathway involving triphenylene-based diketone and o-phenyl diamines. The incorporation of phenazine moiety as discussed in this paper, alters the symmetric nature of the triphenylene. The phenanthro[9,10-a]phenazine-based mesogens exhibit hole mobility in the order of 10-4 cm2/Vs as measured by the space-charge limited current (SCLC) technique. The current density in the SCLC device increases with increasing temperature which indicates that the charge transport is associated with the thermally activated hopping process. This report attempts to elucidate the self-organization of asymmetric phenanthro[9,10-a] phenazine in the supramolecular liquid crystalline state and their potential for the fabrication of high-temperature optoelectronic devices. However, the low charge carrier mobility can be one of the challenges for device performance.

The Analysis of Differential Saturation in Shale Oil Accompanied by an Enhanced Classification of Fluid Distribution within the Pore

Shale oil saturated by high temperature (20 MPa) and high pressure (60 °C) conditions can not only realize the efficient saturation of shale, but also invert the shale oil return and drainage characteristics under the stratum temperature and pressure due to the heterogeneity of shale formations. In this study, the Chang 7 Member shale samples were collected, and the high-temperature and high-pressure containment device was utilized to saturate the shale oil efficiently under 20 MPa and 60 °C, and the differences of liquid hydrocarbon saturation and the degree of liquid hydrocarbon saturation for different types of pores and fractures in the shale were quantitatively characterized with a low-field nuclear magnetic resonance (NMR) technology. The results show that under the condition of formation temperature (60 °C) and pressure (20 MPa), shale oil saturation can be reached after 14 d of saturation in the shale samples. The shale oil saturation process can be roughly divided into three stages according to the various saturation rates: the rapid saturation stage, the slow saturation stage, and the second rapid saturation stage, and the degree of saturation of shale oil is characterized by a V-shape. The shale oil was distributed into four types of pore-fracture systems: adsorption pores, micropores, seepage fractures, and layer fractures. Additionally, the fluid dominantly distributes in the micropores and seepage fractures, the shale oil saturation degree of the micropores features a continuous increase, while that for the seepage fractures presents a V-shape, which finally determines the shale oil saturation characteristics of the shale.