Nd3+ doped Bi2ZnB2O7 crystals (NdxBi2-xZnB2O7) with varying doping concentrations were grown using the Kyropoulos method. The crystal structure of NdxBi2-xZnB2O7 were evaluated through powder X-ray diffraction. The segregation coefficients of Nd3+ were determined by XRF to be 0.82 and 0.79 for 2 at.% and 5 at.% Nd: BZBO crystals, respectively. The full-width at half-maximum (FWHM) of the 2 at.% and 5 at.% Nd: BZBO crystals were 55.8 and 37.7 arcsec, respectively. The transmission, absorption and fluorescence spectra were measured. Moreover, the continuous-wave (CW) laser performance was investigated for the 2 at.% Nd: BZBO crystals. All the results indicated that the Nd:BZBO crystal chould potentially serve as a laser matrix.

High specific surface area carbon aerogel is a kind of adsorption material with excellent comprehensive performance, while its large-scale application is faced with the bottleneck problems including high material cost and complex manufacturing process. Herein, the controllable stripping of the surface micro-scale macropore structure is realized by the control of the activation degree for polyacrylonitrile fiber, the activated fibers with microscale macropore structure is completely etched and stripped into three-dimensional frame structured carbon aerogel particles. The prepared carbon aerogel particles have ultra-high surface area (2732.18 m2 & sdot;g- 1) and pore volume (1.13 cm3 & sdot;g- 1) arising almost entirely from micropores (near 90 %), along with abundant surface heterogeneous elements composed by N (10.97 at%) and O (29.67 at%). Attributed to the synergistic effect of physisorption by micropore structure and chemisorption by O/N-containing surface groups, the carbon aerogel particles exhibit excellent hydrogen storage density of 3.17 wt% under ambient pressure. The facile construction strategy for carbon aerogel is proposed from ameliorative activation technology that has been industrialized, which avoids the time-consuming drying process and strict drying conditions in traditional preparation process.

As an important branch of hydrogen storage materials, adsorptive materials have unique advantages such as high reversibility, fast adsorption rate and mild release conditions, etc. At present, the research on adsorptive hydrogen storage materials mostly focus on the pressure conditions of 30-300 bar, while the atmospheric hydrogen storage performance of adsorptive materials needs to be further enhanced. Based on the sonication-assisted activation process, micro-nano scale synchronous "carving" of viscose fiber was achieved in activation process for viscose fiber after carbonization, and petaloid activated carbon fibers (FL-VACFs) and rod-shaped activated carbon fibers (RL-VACFs) were constructed. Specific surface area of FL-VACFs and RL-VACFs can reach 1085.77 m(2) g(-1) and 956.81 m(2) g(-1) respectively, and the ultramicropore relative contents can reach 44% and 52.08% respectively. Under the synergistic action of abundant ultramicropores and oxygen-containing functional groups, FL-VACFs and RL-VACFs exhibit excellent hydrogen storage density of 2.04 wt% at77 K, 1 bar. Additionally, Multisite-Langmuir model (N = 3) model is discovered more suitable for accurate describing the hydrogen adsorption process of FL-VACFs and RL-VACFs under atmospheric pressure.

Zero thermal expansion (ZTE) borate crystal Zn4B6O13 (ZBO) has excellent optical properties and good thermal stability. In this study, pure and Ni2+-doped ZBO crystals along the [100] and [110] directions were grown using the top-seeded solution growth (TSSG) method. The effect of Ni2+ on the thermal expansion coefficient, electro-elastic constants and their temperature dependence of ZBO crystal was investigated. Furthermore, the absorption spectrum of Ni: ZBO crystal was subjected to analysis. The as-grown single crystals with different growth directions were found to have a small full width at half maximum (all were less than 65"), the high crystal quality was suitable for implementing experimental measurements. The thermal expansion behavior of ZBO was detected from room temperature to high temperature (670 oC), with the average thermal expansion coefficients of the pure and Ni2+-doped ZBO crystals were 4.92 × 10-6 K-1 and 5.72 × 10-6 K-1, respectively. The piezoelectric coefficient d14 of ZBO and Ni: ZBO crystals was measured by the impedance method and the values were on the order of 1.23 pC/N and 1.32 pC/N, respectively. Furthermore, the results of the temperature-dependent tests indicated that Ni2+-doped significantly enhances the piezoelectric stability of the crystals. The absorption spectrum was interpreted using the Tanabe-Sugano diagram. In the tetrahedral approximation of Ni2+, the crystal field parameters Dq=1061 cm-1, B=556 cm-1, and C=2457 cm-1 were determined. The calculated energy levels exhibited a high degree of correlation with the experimental absorption spectrum, thereby providing a theoretical basis for the application of the crystals in lasers.

Large-sized and high-quality Er: Bi2ZnB2O7 (Er: BZBO) single crystal has been grown using the Kyropoulos method. The crystal structure is refined by the Rietveld method, Er: BZBO belongs to the orthorhombic system and space group Pba2, lattice parameters: a = 10.811(1) & Aring;, b = 11.006(1) & Aring;, c = 4.8817(4) & Aring;, which are slightly reduced after doping with Er3+. The thermal expansion anisotropy is studied and shows a decrease with coefficients of alpha(11) = 7.69(1) x 10(-6) K-1, alpha(22) = 9.90(9) x 10(-6) K-1, and alpha(33) = 1.98(8) x 10(-6) K-1, respectively. The relative dielectric constants are found to be epsilon(T)(11)/epsilon(0) = 32.8(1), epsilon(T)(22)/epsilon(0) = 17.2(1), and epsilon(T)(33)/epsilon(0) = 17.0(9), respectively. The dielectric, elastic, and piezoelectric constants for the Er: BZBO crystal are determined by the impedance method, with the piezoelectric coefficients d(15), d(24), d(31), d(32) and d(33) are measured as 1.1(9), -5.4(2), 1.8(7), -5.9(1) and 1.1(5) pC/N, respectively. Furthermore, the temperature dependence of the piezoelectric coefficients from room temperature to 500 degrees C is evaluated, showing good temperature stability for d(24) and d(32) with variations were -7 % and 13 %, respectively.

As the cardinal part of capacitive deionization apparatus, the performance of electrode directly determines the capacitive deionization's adsorption rate, adsorption capacity and selectivity. However, the adsorptivity and reusability of electrode material for special adsorbate need to be developed urgently for the application of capacitive deionization in wastewater purification. In this research, we successfully enhanced the Cu(II) adsorptivity of activated carbon fiber felt (ACFF) to 23 mg/g (4.47 times of ACFF0) by the sonication-assisted chemical reactivation process with the solution of 20 wt % NaOH used as activator (ACFF-N20). As ACFF-N20 used as cathode, the Cu(II) electro-adsorptivity of ACFF-N20 under a current of 0.15 A is 84 mg/g for 130 mg/L Cu(II) standard working fluid. For the Cu(II) wastewater with a concentration of 50 mg/L, it can be purified to 0.14 mg/L by one step of capacitive deionization, which below the drinking standard of World Health Organization. By the technology of low-temperature pickling regeneration, the regeneration rates of ACFF-N20 are 102 %-106 % for five recycling times of Cu(II) electrosorption process. Based on fitting analysis of adsorption processes using different kinetic models, it was found that Langmuir model is more convergent than Freundlich model to the adsorption isotherms. Additionally, Bangham adsorption kinetic model and pseudo-first order adsorption kinetic model have the best fitting correlation for the Cu(II) static adsorption and electrosorption of ACFFs. Based on the sonication-assisted chemical reactivation process, the Cu(II) adsorptivity of activated carbon fiber felt (ACFF) is successfully enhanced to 23 mg/g. As it used as Flexible self-Supporting electrodes in capacitive deionization, 50 mg/L Cu(II) wastewater can be purified to 0.14 mg/L (below the drinking standard of World Health Organization) by one step of capacitive deionization.image

Catalysts with hydrogen spillover mechanisms can significantly enhance the hydrogen storage density of carbon-based porous materials under ambient conditions, attributed to its hydrogen adsorption energy improving by cracking hydrogen molecules into active hydrogen (hydrogen ions or hydrogen radicals), which is considered as a promising strategy for optimizing hydrogen storage performance of porous materials. The developing of non-noble metal based catalysts with hydrogen spillover mechanisms is currently a research hotspot and development direction. Based on this, the catalyst research progresses based on the non-noble metal materials are summarized to clarifies the factors affecting the hydrogen spillover effect of non-noble metal based catalysts. This article looks forward to the research and development direction of non-noble metal based catalysts for carbon-based porous materials, which hope to promote the development of non-noble metal based catalysts and accelerate the industrial application of porous solid hydrogen storage materials.

A novel Tm3+-doped YSr3(PO4)(3) (Tm:YSP) crystal with a disordered crystal structure was grown by using the Czochralski pulling method. The single crystal growth, structure, absorption and emission spectra were systematically analyzed. The absorption bandwidth at similar to 792 nm was found to be 21 nm, showing that the Tm:YSP crystal was very suitable for commercial laser diodes pumping of AlGaAs. Furthermore, the maximum emission cross section centering at 1835 nm was determined to be 0.86 x 10(-20) cm(2) with an emission bandwidth of 202 nm, which indicates the promising applications in the fields of ultrafast and tunable lasers. In addition, Spectroscopic parameters, containing Judd - Ofelt intensity, line strengths, radiative transition probabilities, fluorescence branching ratio and radiative lifetime, were analyzed by using the Judd - Ofelt theory. All above results showed that the Tm:YSP crystal with a disordered structure was a potential laser medium in the similar to 2 mu m region.

Due to the active chemical properties of hydrogen at room temperature, the efficient and safe storage technology of hydrogen is the main bottleneck problem in the large-scale application of hydrogen energy, while solid hydrogen storage materials are anticipated to be the solution to the transportation and storage of hydrogen. Similar to normal temperature superconducting materials, solid hydrogen storage materials with excellent hydrogen storage performance under ambient condition are one of the commanding heights of future hydrogen storage technology, which can realize leapfrog effect on the large-scale application of hydrogen energy industry. As a typical adsorptive hydrogen storage material, metal-organic frameworks (MOFs) mostly achieve hydrogen saturated adsorption under the saturated adsorption pressure of 30-300 bar, the research on hydrogen storage performance under ambient condition needs to be further enhanced. In view of the hydrogen storage application of MOFs, the structural controllability of MOFs formed by mainstream synthesis methods, key physical and chemical parameters affecting the hydrogen storage performance and hydrogen storage application of MOFs under ambient condition are analyzed systematically. Furthermore, it provides theoretical support and research prospects for the controllable synthesis strategy of MOFs and the application of hydrogen storage under ambient conditions. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Polyacrylonitrile-based nascent fibers (PAN-NFs) with skin–core structure are commonly inferior fiber or waste fiber, which often abundanted in the industrial production process of polyacrylonitrile (PAN)-based carbon fibers. At present, the related research about the skin–core structure of PAN fiber mainly focuses on its regulation and elimination. Based on the different activation difficulty between skin part and core part, we proposed a new way to prepare activated carbon hollow fiber from PAN-NFs with skin–core structure. Phosphoric acid activation process is used in the facile fabrication of nitrogen, oxygen co-doped activated carbon hollow fiber (N/O-ACHF). The synthetic N/O-ACHF has the structural characteristics of smooth outer wall, while the inner wall is densely covered with micrometer-scale macropores (0.31–2.18 μm) and abundant micropores/mesopores (0–6 nm), which provides excellent structural conditions for hydrogen storage at atmospheric pressure. SBET, micropore volume, surface oxygen heteroatom content and surface nitrogen heteroatom content of N/O-ACHF are 545.72 m2/g, 0.188 cm3/g, 15.26 at% and 4.06 at%, respectively. The multistage pore structure and abundant surface functional groups provide excellent physical structure conditions for hydrogen storage. The preparative N/O-ACHF delivers a high hydrogen storage density of 1.35 wt% at atmospheric pressure.

Rare-earth calcium oxyborate crystals (RECa4O(BO3)3, RECOB, RE: rare-earth elements) are a kind of multifunctional crystal materials. In this work, the temperature dependent behaviors of the electro-elastic constants of NdCOB crystal were investigated over the temperature range of-80-200 degrees C, and their temperature coefficients were evaluated. It is found that NdCOB crystal possesses minimal variation of relative dielectric permittivities (<3%). The temperature coefficient of frequency for ZY cut with width shear vibration mode is in the order of 0.07 x 10-4/degrees C. The temperature coefficients of the elastic compliances are obtained to be in the range of-33.0 x 10-4/degrees C-32.2 x 10-4/degrees C. Particularly, the s44 and s66 were found to show low temperature coefficients of the elastic compliances, i.e. 1.0 x 10-4/degrees C and-0.4 x 10-4/degrees C, respectively, indicating the existence of zero temperature coefficient of frequency crystal cut. Furthermore, the electromechanical coupling factors and piezoelectric coefficients as a function of temperature were studied. The electromechanical coupling factor k26 and piezoelectric co-efficient d26 are determined to be-30.8% and-15.2 pC/N at room temperature, respectively. The large piezoelectric response and zero temperature coefficient of frequency indicate the potential usage of NdCOB crystal for piezoelectric frequency devices over a wide temperature range.(c) 2021 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.

Lithium niobate crystals (LiNbO3, LN) are multifunctional crystal materials with many outstanding properties. In this work, the electro-elastic properties of LN single crystals were explored at temperatures from −150 °C to 150 °C. The temperature dependences of dielectric permittivities, elastic compliances, electromechanical coupling factors and piezoelectric coefficients were determined using the impedance method. The LN crystals possessed large dielectric permittivities, the ε11T/ε0 and ε33T/ε0 were 83.2 and 29.4 at room temperature, respectively. The elastic compliances s11, s13, s33 and s44 presented a positive increase as the temperature increased, and the variations were 5.0%, 8.2%, 4.6% and 5.4%, respectively, showing a good temperature stability. Moreover, the temperature dependence of the electromechanical coupling factors and piezoelectric coefficients for different vibration modes were studied with a temperature range from −150 °C to 150 °C, where the thickness shear vibration mode d15 presented a large piezoelectric response and minimal temperature variation.

Pyroelectric properties of orthorhombic Bi2ZnB2O7 (BZBO) crystals were investigated by using the charge integration method. The primary and the secondary pyroelectric coefficients of BZBO crystals were found to be 6.4 and −6.5 µC/(m2·°C), respectively. The pyroelectric performance was evaluated by different figure of merits (FOMs), where BZBO crystals possessed relatively high current responsivity Fi (10.38 pm/V), and detectivity Fd (11.31 × 10−5/Pa1/2). In addition, the temperature dependent behaviours of primary pyroelectric coefficients and FOMs were studied from 15 °C to 155 °C; the pyroelectric properties were found to decrease with increases in temperature.

Bulk LiNbO3 (LN) crystals could maintain their electrical and electro-elastic properties even under hard irradiation.

YCa4O(BO3)(3) (YCOB) and GdCa4O(BO3)(3) (GdCOB) crystals are promising piezoelectric materials for high-temperature sensing applications. The high-temperature condition is accompanied by hard irradiation, such as in a nuclear power plant. In this study, the electroelastic properties of YCOB and GdCOB crystals irradiated by different doses of 6 MeV Xe23+ (10(13), 10(15), and 10(16) ions/cm(2)) were studied in the temperature range of 25-850 degrees C. YCOB and GdCOB crystals exhibit good electrical resistivity stability with irradiation, where the resistivity of >10(8) Omega center dot cm is achieved @700 degrees C. Meanwhile, the electroelastic properties are found to maintain similar values, with variations being less than 8% after irradiation. The band gaps of the YCOB and GdCOB crystals are narrowed upon irradiation, leading to a slight decrease in electrical resistivity, while the slight increase in the dielectric permittivity after irradiation is associated with the irradiation-induced distortion of the structure and weakening of chemical bonding. All the irradiation resistant properties demonstrate that the bulk YCOB and GdCOB crystals are good candidates for use in high-temperature piezoelectric sensing under harsh environments including hard irradiation.

The BZBO crystals were found to present good temperature stability of elastic compliances.

The NYAB crystal shows relatively high resistivity and good temperature stability of piezoelectric activity, potential for high temperature piezoelectric applications.

Two noncentrosymmetric orthophosphate crystals, YSr3(PO4)(3) and YBa3(PO4)(3), with melting points over 1800 degrees C have been grown by using the Czochralski technique. The YSr3(PO4)(3) and YBa3(PO4)(3) crystals were determined to possess cubic symmetry with a space group of I (4) over bar 3d. The cell parameters were determined tobe a = b = c = 10.081(9) angstrom, V = 1024.6(3) angstrom(3), and Z = 4 for YSr3(PO4)(3); and a = b = c = 10.452(2) angstrom, V = 1141.9(7) angstrom(3), and Z = 4 for YBa3(PO4)(3) crystal. Both the YSr3(PO4)(3) and YBa3(PO4)(3) crystals were found to show disordered occupations between Sr (or Ba) and Y. Thermal properties were also characterized, where the thermal conductivity values were 1.53 W.m(-1).K-1 and 1.39 W.m(-1).K-1. The YSr3(PO4)(3) and YBa3(PO4)(3) crystals were confirmed to possess a broad transmittance range with an optical absorption edge shorter than 190 nm. In addition, the laser-damage thresholds of YSr3(PO4)(3) and YBa3(PO4)(3) crystals were evaluated at wavelengths of 1064 nm using a 10 ns Nd:YAG laser and found to be on the order of 1150 MW/cm(2) and 680 MW/cm(2), respectively. The YSr3(PO4)(3) and YBa3(PO4)(3) single crystals were shown to be good multifunctional crystals for potential opto-electric applications.

The trigonal lithium niobate crystal (LiNbO 3 , LN) is a multi-functional material, which possesses excellent pyroelectric and piezoelectric properties as well as the nonlinear optical properties etc. In this paper, the stability of electro-elastic properties of LN crystal irradiated by the 6MeV Xe 23+ ions were evaluated for potential piezoelectric applications in harsh environment. the electrical resistivity of the irradiated LN was found to decrease with increasing irradiation dose. In contrast to the electrical resistivity, the relative dielectric permittivity ε 22 /ε 0 of LN sample was found to increase with increasing irradiation dose. The values of electromechanical coupling factor k 21 , the elastic compliance s 11 and the piezoelectric coefficient d 21 for the irradiated samples were determined and found that the irradiated LN crystal could maintain its electro-elastic properties similar to the pristine crystal.