11 - Dielectric Polymer Materials with High Thermal Stability

Ultra-low hysteresis electrostrictive strain with high thermal stability in Bi(Li0.5Nb0.5)O3-modified BaTiO3 lead-free ferroelectrics

High thermal stability and tunable magnetic exchange interaction (MEI) in SmCo materials have been the critical problem in applications to magnetic recording media and nanocomposite permanent magnets. We constructed SmCo films with a high thermal stability and tunable MEI by controlling the phase transformation through properly increasing the Sm concentration (20.5–37.7 at.%) and controlling the annealing process. Microstructure studies show that the SmCo5 phases ensure that the film has a high thermal stability. Moreover, we manipulated the MEI in the film with non-magnetic precipitated SmCo2 particles in the vicinity of SmCo5 particles. These results provide a novel way to tune the MEI in SmCo materials while maintaining a high thermal stability.

Evaluation of basic sites of ZIFs metal organic frameworks in the Knoevenagel condensation reaction

High thermal stability and colossal permittivity of novel solid solution LaFeO3/CaTiO3

Electron Beam Physical Vapor Deposition (EB-PVD) was applied to fabricate a thin film YSZ electrolyte with large area on the porous NiO-YSZ anode substrate. Microstructural and thermal stability of the as-deposited electrolyte film was investigated via SEM and XRD analysis. In order to obtain an optimized YSZ film with high stability, both temperature and surface roughness of substrate were varied. A structurally homogeneous YSZ film with large area of 12 × 12 ㎠ and high thermal stability up to 900℃ was fabricated at the substrate temperature of T s /T m higher than 0.4. The smoother surface was proved to give the better film quality. Precise control of heating and cooling rate of the anode substrate was necessary to obtain a very dense YSZ electrolyte with high thermal stability, which affords to survive after post heat treatment for fabrication a cathode layer on it as well as after long time operation of solid oxide fuel cell at high temperature.

Improving the thermal stability of diamond and other superhard materials has great significance in various applications. Here, we report the synthesis and characterization of bulk diamond–cBN–B4C–Si composites sintered at high pressure and high temperature (HPHT, 5.2 GPa, 1620–1680 K for 3–5 min). The results show that the diamond, cBN, B4C, BxSiC, SiO2 and amorphous carbon or a little surplus Si are present in the sintered samples. The onset oxidation temperature of 1673 K in the as-synthesized sample is much higher than that of diamond, cBN, and B4C. The high thermal stability is ascribed to the covalent bonds of B–C, C–N, and the solid-solution of BxSiC formed during the sintering process. The results obtained in this work may be useful in preparing superhard materials with high thermal stability.

High thermal stability chalcogenide phase-change materials for embedded memory applications

This paper presents the thermal and electromagnetic behaviors of multistacked no-insulation (NI) REBa 2Cu3O7− x (REBCO, RE = rare earth) pancake coils. The NI winding technique gives a high enough thermal stability not to damage REBCO coils even though a normal-state transition occurs. The high thermal stability has been verified through overcurrent tests. Moreover, the numerical simulation of multistacked NI REBCO pancake coils has been performed to investigate the electromagnetic behaviors in detail. The simulation results also confirmed the high thermal stability of NI REBCO pancake coils. However, it does not mean that an NI REBCO magnet never quenches. In experiments, it was observed that a quench in one of the pancake coils propagated to the other pancake coils sequentially. The above sequential quench from pancake to pancake has not been confirmed in the numerical simulation since the thermal behavior is not considered. For the more reliable verification, we have developed a numerical simulation to investigate the thermal and electromagnetic behaviors by the partial element equivalent circuit method and the two-dimensional thermal finite-element method. In this paper, the six-stacked NI REBCO pancake coil is simulated with several operating temperatures, and the sequential quench is reproduced. The velocity of the sequential quench is also shown.

Methacryloxypropyl-polyhedral oligomeric silsesquioxane (MAP-POSS) was photopolymerized with the tri- or tetra-functional thiol monomer in different stoichiometry. A novel inorganic–organic methacrylate hybrid material with highly cross-linked network and high performance was synthesized by UV-initiated thiol–ene click chemistry. SEM–EDAX images and XRD diffractograms showed that no agglomeration of MAP-POSS was observed, indicating MAP-POSS dispersed uniformly in the hybrid materials. Real-time FTIR was employed to monitor the conversion of thiol and methacrylate as a function of irradiation time, and the results revealed that highly thiolated monomer could promote the conversion of methacrylate effectively because of stronger chain propagation capability. The TGA indicated that the hybrid materials had high thermal stability of which the onset decomposition temperature rose to 350 °C, approximately 50 °C higher than that of the traditional UV-cured epoxy acrylate/triethylene glycol dimethacrylate (EA/TEGDMA, 70:30 w/w) resin. The highest glass transition temperature (Tg) of the hybrid materials was 76.2 °C. Compared with traditional EA/TEGDMA resins, the novel hybrid materials consisted of MAP-POSS had fast curing rate, high mechanical properties and thermal stability which made the wider practical applications of UV-cured hybrid materials feasible.

Metal dodecahydro-closo-dodecaborates have been recently explored as materials for hydrogen storage and as promising ionic conductors. However, their utility as hydrogen storage media is impeded by their high thermal stability, kinetic limitations, and side reactions. The high thermal and chemical stability of these materials makes them interesting for solid battery membrane applications, however more work is needed to understand the complicated phase transitions which occur in many metal dodecahydro-closo-dodecaborates. Recent literature suggests that dodecahydro-closo-dodecaborate species are formed as stable intermediates during the dehydrogenation of metal borohydrides [1]. This hypothesis is especially intriguing in the context of high thermal stability reported for compounds containing icosahedral dodecahydro-closo-dodecaborate anions in the presence of hydrogen gas [2]. Here, a series of multi-component alkali, alkaline-earth and transition metal [B12H12]2- compounds were isolated and characterized by single-crystal and powder X-ray diffraction techniques. Attempts to rehydrogenate M2B12H12 and MB12H12 (where M= alkali or alkaline-earth metal) in the presence of the metal hydrides we made, and several compounds were found to be susceptible to dehydrogenation/rehydrogenation reactions. In addition, selected M2B12H12 compounds were found to display high-temperature phases with increased values of alkali metal ionic conductivity.

High-temperature energy storage polyimide dielectric materials: polymer multiple-structure design

Phosphine-based covalent organic framework for highly efficient iodine capture

A series of Mn4+-activated CaLaMgSbO6 far-red-emitting phosphors were synthesized by a solid-state reaction route and the microstructure and optical characterizations were investigated in detail. Upon excitation at 370 and 469 nm, the samples showed intense far-red emission at about 708 nm originating from the 2Eg → 4A2g transition and the optimal Mn4+ concentration was 0.7 mol%. The as-prepared phosphors also exhibited excellent internal quantum efficiency (88%) and high thermal stability. The emission intensity at room temperature dropped to 54% when the temperature rose to 423 K and the activation energy was 0.34 eV. The outstanding optical properties and the fact that the emission band of the obtained phosphors had a broad overlap with the absorption band of phytochrome PFR demonstrated that the CaLaMgSbO6:Mn4+ phosphors may be promising potential spectral converters for applying to indoor plant cultivation light-emitting diodes.

In this study, a series of composite Ni-based catalytic materials exhibiting high activity, thermal stability, and resistance to carbon deposition have been synthesized via solvent wet mixing and high-temperature calcination using readily available industrial-grade metal powders. Subsequently, the catalyst’s crystal structure and pore type were analyzed using XRD, BET, and other characterization techniques, followed by an investigation into the catalyst’s performance in dry reforming of CO2 methane. The experimental results show that the composite Ni-based catalytic materials maintain more than 95% of the reaction conversion and nearly 100% of the product selectivity during the reaction at 800 °C for nearly 40 hours and have high thermal stability and catalytic activity. The successful construction of this composite Ni-based catalyst provides certain theoretical support and technical support for the subsequent design of composite metal catalysts.

We previously developed a high-magnetic-field REBCO coil for use in medical devices such as medical accelerators and high-magnetic-field MRI. The use of high-temperature superconducting (HTS) coils in such applications necessitates their miniaturization while providing high magnetic fields. However, when the current density is improved by reducing the copper-stabilization-layer thickness in the conventional insulated HTS coil, the thermal stability is lowered, which leads to a tradeoff between high current density and high thermal stability. Therefore, we examine no-insulation (NI) coils that allow compatibility between high current density and thermal stability. Recent research has indicated that NI coils with multiple defects can afford a stable and high critical current (Ic) and operate without serious problems, which makes it possible to produce coils wound with commercial REBCO tapes containing several defects along the tape, which in turn makes fabrication economically viable. However, there are many unknown aspects of the current, magnetic field, and heat behaviors of NI coils with defects, particularly when large currents flow through them. Here, in order to examine the behavior of a multiple-defect NI coil subjected to a large current at the temperature of ~30 K via application of the conduction cooling method, we use a combination of the partial element equivalent circuit method and the finite-element method to investigate the detailed current and thermal behaviors. Our results indicate that defective NI coils can afford a critical current Ic value of ~80% of that of defect-free NI coils, which makes our findings valuable in terms of contributing to further developments in HTS coil applications.