The design of 2/8-type high-pressure cell applied to in situ neutron diffraction

The DIA-type Kawai cell possesses a larger volume and a quasi-hydrostatic pressure environment and has been widely used in materials’ synthesis and x-ray diffraction experiments.However, few high-pressure in situ neutron diffraction experiments were performed in the DIA-type Kawai cell because there is no wide window for neutron diffraction and the second-stage anvils and guild block material attenuates the neutron signal significantly.In this work, we tentatively modified the normal DIA-type Kawai cell(MA 2-6-8) into a MA 2-8 mode by removing the six first-stage tungsten carbide anvils.As a consequence, the eight tungsten carbide anvils(Kawai cell) are directly driven by the guide blocks.The results of ex situ and in situ pressure calibration show that the cell pressure can reach 5 GPa with small truncation edge lengths(TEL) of 3 mm even at the load of 300 kN.It suggests that this MA 2-8 cell may open a new way for high-pressure and high-temperature in situ neutron diffraction.

Small-angle neutron scattering study on the stability of oxide nanoparticles in long-term thermally aged 9Cr-oxide dispersion strengthened steel

A 9 Cr-oxide dispersion strengthened(ODS)steel was thermally aged at 873 K for up to 5000 h.The size distribution and chemical composition of the dispersed oxide nanoparticles were analyzed by small-angle neutron scattering under a magnetic field.Combined with transmission electron microscopy,Vickers micro-hardness tests and electron backscattered diffraction measurements,all the results showed that the thermal treatment had little or no effect on the size distributions and volume fractions of the oxide nanoparticles in the ferromagnetic matrix,which suggested excellent thermal stability of the 9 Cr-ODS steel.

Neutron Diffraction of Large-Volume Samples at High Pressure Using Compact Opposed-Anvil Cells

Neutron diffraction techniques of large-volume samples at high pressure using compact opposed-anvil cells are developed at a reactor neutron source, China＇s Mianyang research reactor. We achieve a high-pressure condition of in situ neutron diffraction by means of a newly designed large-volume opposed-anvil cell. This pressure calibration is based on resistance measurements of bismuth and the neutron diffraction of iron. Pressure calibration experiments are performed at room temperature for a new cell using the tungsten carbide anvils with a tapered angle of 30°, Φ4.5 mm culet diameter and the metal-nonmetal composite gasket with a thickness of 2 mm. Transitions in Bi（Ⅰ–Ⅱ 2.55 GPa, Ⅱ–V 7.7 GPa） are observed at 100 and 300 kN, respectively, by resistance measurements.The pressure measurement results of neutron diffraction are consistent with resistance measurements of bismuth.As a result, pressures up to about 7.7 GPa can routinely and stably be achieved using this apparatus, with the sample volume of 9 mm^3.

Recent progress of in-situ characterization of LiNi_(1−x−y)Co_(x)Mn_(y)O_(2) cathodes for lithium metal batteries: A mini review

In the context of the gradual popularity of electric vehicles(EVs),the development of lithium battery systems with high energy density and power density is regarded as the foremost way to improve the range of EVs.LiNi_(1-x-y)Co_(x)Mn_(y)O_(2)(NCM)cathodes have been the focus of researchers due to their high energy density,excellent power performance,and low-temperature resistance.However,the elaboration of the decay mechanism of NCM cathode based on lithium metal batteries(LMBs)is still being restricted to the primary level.In the past decades,the development and application of advanced in-situ characterization tools have facilitated researchers'understanding of the internal operation mechanism of batteries during charging and discharging.In this minireview,the latest progress of in-situ observation of the NCM cathode by X-ray diffraction(XRD),fourier transform infrared(FT-IR)spectroscopy,Raman spectroscopy,atomic force microscopy(AFM),transmission electron microscope(TEM),optical microscope,and other characterization tools is summarized.The mechanisms of structural degradation,cathode-electrolyte interfaces(CEIs)composition,and dynamic changes of NCM,electrolyte breakdown,and gas production are elaborated.Finally,based on the existing research progress,the opportunities and challenges for future in-situ characterization technology in the study of the mechanism of LMBs are discussed in depth.Therefore,the purpose of this minireview is to summarize recent work that focuses on the outstanding application of in-situ characterization techniques in the mechanistic study of LMBs,and pointing the way to the future development of high energy density and power density LMBs systems.

Coexistence of superconductivity and antiferromagentic order in Er_(2)O_(2)Bi with anti-ThCr_(2)Si_(2) structure

We investigated the coexistence of superconductivity and antiferromagnetic order in the compound Er_(2)O_(2)Bi with anti-ThCr_(2)Si_(2)-type structure through resistivity,magnetization,specific heat measurements and first-principle calculations.The superconducting transition temperature Tc of 1.23 K and antiferromagnetic transition temperature TN of 3 K are observed in the sample with the best nominal composition.The superconducting upper critical field H_(c2)(0)and electron-phonon coupling constantλe−ph in Er_(2)O_(2)Bi are similar to those in the previously reported non-magnetic superconductor Y_(2)O_(2)Bi with the same structure,indicating that the superconductivity in Er_(2)O_(2)Bi may have the same origin as in Y_(2)O_(2)Bi.The first-principle calculations of Er_(2)O_(2)Bi show that the Fermi surface is mainly composed of the Bi 6p orbitals both in the paramagnetic and antiferromagnetic state,implying minor effect of the 4f electrons on the Fermi surface.Besides,upon increasing the oxygen incorporation in Er_(2)O_(x)Bi,Tc increases from 1 to 1.23 K and TN decreases slightly from 3 K to 2.96 K,revealing that superconductivity and antiferromagnetic order may compete with each other.The Hall effect measurements indicate that hole-type carrier density indeed increases with increasing oxygen content,which may account for the variations of Tc and TN with different oxygen content.

Enhanced piezo-response in copper halide perovskites based PVDF composite films

In-situ fabricated perovskite nanocrystals in polymeric matrix provide new generation composite materials for plenty of cutting edge technology. In this work, we report the in-situ fabrication of copper halide perovskite(MA_2CuCl_4, MA:CH_3NH_3^+) embedded poly(vinylidene fluoride)(PVDF) composite films. The optimized MA_2CuCl_4/PVDF composite films exhibit greatly enhanced piezo-response in comparasion with pure PVDF films. The enhancements were invesitgated and explained by applying piezo-response force microscopy(PFM) measurements and density functional theory(DFT) caculations. We proposed that the high piezoelectric properties of MA_2CuCl_4/PVDF composite films could be related to the large Cu off-centering displacement, the strong interactions between MA_2CuCl_4 and PVDF as well as large stress concentration around the MA_2CuCl_4 particles in the films. These piezoelectric composite films are expected to be suitable functional materials for flexible and/or wearable piezoelectrics.

Sr阳离子和O阴离子空位缺陷调控工程提升钙钛矿Sr_(x)VO_(3-δ)储锂性能

钙钛矿结构氧化物的空位缺陷调控工程在催化和太阳能电池等领域被广泛研究应用,本文进一步拓展了钙钛矿材料空位缺陷工程在储能领域的应用.使用钙钛矿Sr_(x)VO_(3-δ)材料为研究材料,通过调控溶胶燃烧过程中Sr/V化学计量比和还原温度,精确控制样品中的Sr阳离子和O阴离子的空位浓度,并且保持了Sr_(x)VO_(3-δ)材料的钙钛矿结构.电化学研究结果表明,通过提高Sr阳离子和O阴离子空位缺陷浓度,Sr_(x)VO_(3-δ)电极比容量和倍率性能显著提升.其中,Sr空位缺陷的引入为锂离子提供了额外储锂位点和扩散通道,而O空位缺陷的引入则显著提升了Sr_(x)VO_(3-δ)电极的电导率和锂离子扩散系数.因此,空位缺陷工程为钙钛矿结构储能材料电化学性能的提升和设计提供了新思路.