Decompression-induced disorder to order phase transition in low-melting ionic liquid [OMIM][PF6]

In situ pressure-induced Raman spectral changes of 1-octyl-3-methyl imidazolium hexafluorophosphate （[OMIM][PF6]） have been investigated under the pressure up to 5.86 GPa at room temperature. The results indicated that [OMIM][PF6] experienced a phase transition at about 4.12 GPa during compression, and it was thought as a phase transition of liquid to a superpressurized glass. Upon decompression, from the obvious change of Raman spectra of [OMIM][PF6] at about 0.48 GPa, it could be inferred that a decompression-induced disorder to order phase transition in [OMIM][PF6] occurred. The phase behavior of [OMIM] [PF6] at low temperature under atmospheric pressure was also investigated in detail. The result showed that Raman spectra of [OMIM][PF6] varied slightly and no crystallization occurred upon cooling. These facts suggested that a disorder to order phase transition was induced by decompression in [OMIM][PF6], and [OMIM][PF6] served as a superpressurized glass under the pressure above 4.12 GPa, which was similar to the glassy state at low temperature.     

High-pressure storage of hydrogen fuel: ammonia borane and its related compounds

As a promising candidate material for hydrogen storage, ammonia borane（NH3BH3） has attracted significant interest in recent years due to its remarkably high hydrogen content. Subjecting this material to high pressure not only enables the formation of novel phases and compounds with exotic properties, but also improves our basic understanding of material’s behavior at different levels of atomic and molecular interactions. This review focuses on the perspective of high-pressure chemical hydrogen storage related to NH3BH3-based materials. Four main aspects are discussed： the structures and bonding of NH3BH3 over a wide pressure–temperature space, thermolysis of NH3BH3 at high pressure, the formation of a novel high-pressure H-rich compound as a result of storage of additional molecular H2 in NH3BH3, and the potential rehydrogenation of the thermally decomposed NH3BH3 under the extreme of pressure.     

NH4Cl的高压相变及弹性性质实验研究

在高压环境下, 对天然卤砂(NH₄Cl)进行同步辐射单晶X射线衍射(XRD)、拉曼光谱和红外光谱分析。结果表明, NH₄Cl在13.6 GPa 发生相变, 从IV相(空间群为)变为V相(空间群为P4/nmm); IV相和V相NH₄Cl的三阶Birch-Murnaghan状态方程参数分别为 K₀=24.9(1) GPa, V₀=56.4(1) ų, K₀′=5.5以及K₀=35(25) GPa, V₀=110(11) ų, K₀′=3.8(13)。NH₄Cl的拉曼光谱在13.7 GPa出现新峰和不连续变化, 其拉曼位移与压强呈现线性关系, 据此获得IV相和V相NH₄Cl各拉曼振动的位移量随压强的变化, 并计算格林乃森参数。NH₄Cl的红外光谱在11.7~14.8 GPa出现N—H振动峰分裂。NH₄Cl, NH₄Br和NH₄I的IV-V相变压强依次降低, 表现出与阴离子半径成反比的规律。     

Synthesis of boron-doped diamond with laser heated diamond anvil cell

Boron-doped diamond has been synthesized from graphite mixed with different ratio of B₄C at high pressure high temperature (HPHT) using laser heated diamond anvil cell. The starting composition was transformed to diamond compound at pressure ∼9 GPa, 2300–2400 K as indicated by the in-situ X-ray diffraction pattern with synchrotron radiation source. Raman spectrum of the recovered specimen from HPHT state confirmed that boron has been doped into diamond lattice.     

光谱在晶体材料测试方面的应用

总结了目前用于检测晶体材料的四种常用的光谱分析方法:晶体衍射谱、红外光谱、拉曼光谱和THz光谱,及其各自的材料应用范围.分析实验所得的LiTaO3和LiNbO3拉曼光谱图,并计算LN晶体中Li的组分含量.     

高温高压下ZnO的相变及热力学性质研究

本文通过平面波赝势密度泛函理论研究了ZnO岩盐(B1)结构、CsCl(B2)结构、闪锌矿(B3)结构和纤锌矿(B4)结构的相变和热力学性质.通过计算得到了晶格常数、体弹模量及体弹模量对压强的一阶导数,与实验值和其他计算结果都符合地较好.根据等焓原理,发现从B4和B3结构到B1结构的相变压强分别约为8.9GPa和7.8GPa.通过准德拜模型,成功得到B4结构的热力学性质,包括不同压强和温度下的状态方程、热膨胀系数和热容.     

掺La铁酸铋粉体的晶体结构

用溶胶凝胶法成功制备Bi1-xLaxFeO3(BLFO,x=0.00～0.40)粉体样品,用X射线衍射谱和拉曼光谱表征样品的结构,并用Rietveld精修法拟合样品的XRD谱.结果显示随着掺La量x的增加,晶格常数逐渐减小,晶胞体积线性减小,当掺杂量增加到x=0.30时,BLFO粉体样品的晶体结构由R3c的三角相转变为Amn2的正交相结构.     

碳化树木的微结构特征研究

对浙江温岭火山角砾岩中的碳化树木进行了高分辨电子显微镜、X粉晶衍射和激光拉曼光谱研究。高分辨电子显微像表明火山角砾岩中的碳化树木相当于微柱石墨—柔绉石墨过渡阶段。碳化树木的一级拉曼光谱D峰波数在1359.7～1369.2cm^-1之间,O峰波数在1594.5～1603.4cm^-1之间。根据峰面积比A_D/(A_D+A_O)计算得出其L_a在7.6～11.8nm之间,与高分辨电子显微像观察结果一致。     

Compression behavior of Sm）2Ti2O7-pyrochlore up to 50 GPa：single-crystal X-ray diffraction and density functional theory calculations

Single-crystal X-ray diffraction at pressures up to 50 GPa has been employed to study the compression behavior of Sm2Ti2O7-pyrochlore. In contrast to earlier reports, we observed no pressure-induced amorphization or pressure-induced anion disorder up to 50 GPa. The experimental study has been complemented by density functional theory-based calculations. A combination of the theoretical and experimental data yields a bulk modulus of 185 GPa, significantly higher than a value which had been reported earlier. In comparison to earlier work, the current study provides more reliable data due to the use of neon as a pressure medium, which provides a more hydrostatic pressure than the aluminum, which had been employed as a pressure medium in the earlier studies. An analysis of the compressibility of Al2B2O7 pyrochlores shows an approximately linear dependence of the bulk modulus on the unit cell volume.     

P2O5对氟镓铟基玻璃析晶稳定性和结构的影响

以20GaF3-15InF3-20CdF2-15ZnF2-10SnF2-20PbF2(GICZSP)为基玻璃,用P2O5替代等摩尔含量CdF2,以改善玻璃的抗析晶能力.利用差示扫描量热分析、拉曼光谱和X射线衍射分析手段,表征不同含量P2O5对玻璃抗析晶性能及结构的影响.结果表明,P2O5的引入提高了玻璃的析晶稳定性.P2O5在玻璃中以不含P＝O双键的[PO(4-)4,Q0]四面体存在.随着P2O5量的增加,新出现了M[O,F]6八面体结构.     

浮区法制备金红石单晶及其光谱特性

采用锐钛矿型二氧化钛为原料, 通过浮区法制备金红石型二氧化钛单晶. 通过X射线衍射（XRD）和拉曼散射（Raman）测试, 对单晶体的结构进行表征, 表明晶体为典型的金红石相. 在Raman光谱中可观测B_1g(143 cm^-1),E_g(446 cm^-1),A_1g(605 cm^-1)和B_2g(826 cm^-1)4个Raman活性模, 并观测到可能属于2级Raman散射峰, 如273,316,327,519,700 cm^-1.     

金刚石膜微结构分析

对在Si(100)基底上利用化学汽相沉积(CVD)法制备的金刚石膜,采用X—射线衍射(XRD)技术和正电子湮没谱学(PAS)原理进行了有关物相成分和微结构的测量分析．研究发现,在金刚石膜中微观缺陷的产生取决于薄膜生长过程的控制和基底表面局域生长环境的条件差异．结果表明,金刚石膜体和表面的结晶、微晶和非晶结构与正电子谱分析的3种正电子态相符合．     

锌镍合金镀层的组成与相结构的关系

用Ｘ射线衍射等方法，研究了从碱性镀液电沉积的锌镍合金镀层的化学组成与相结构，晶粒尺寸，显微硬度的关系。结果表明，随着合金镀层中镍含量的提高，合金镀层由η和ｒ－相共存转变为只有ｒ－相；镀层的织构相应地由六方结构的（１００）择优面转变为立方结构的（３３０）择优面。η－和ｒ－相的晶粒尺寸随镀层镍含量的提高而降低；只有ｒ－相时，晶粒尺寸降低更为显著。镀层的显微硬度当镍含量为９．０ｗｔ．％时呈现一极小点。     

(Fe Cr)_(83)B_(17)非晶合金结构及其晶化相变的研究

本文用DTA和X射线衍射技术,研究了(FeCr)_(83)B_(17)非晶合金晶化相变全过程。说明该非晶体系的晶化相变过程中,原子键力是晶化相变的驱动力。从“t-x”关系表明,在我们实验条件下(x=5％,15％,25％),高熔点的Cr含量(x)增大所引起晶化峰位向高温方向增大值具有良好的线性关系。实验指出,(Fe_(1-x)Cr_x)_(83)B_(17)非晶合金淬火态的结构单元是Fe_3B局域9原子多面体结构的原子团。     

纳米α-Fe_2O_3的制备及其正电子湮没谱学研究

对氧化铁颗粒进行了X射线衍射谱(XRD)测量和正电子湮没寿命谱(PALS)测量,分别运用Jade和Lifetime软件拟合数据,研究了纳米氧化铁颗粒的结构、缺陷以及自由电子密度.XRD测量结果表明了氧化铁是简单六方晶系,空间群是R-3c(167),其相应的点阵常数分别是三个基矢的长度a=b=0.530 42 nm,c=1.374 60 nm.PALS测量结果表明了正电子在氧化铁材料中的寿命成分有三种,值分别约是τ_1=150.7 ps,τ_2=333.0 ps,τ_3=725.0 ps,主要寿命成分是短寿命τ_1和中等寿命τ_2两种,分别对应的缺陷种类是近似单空位大小的自由体积缺陷和微孔洞缺陷,且其对应的强度比I_1/I_2值为1.52,表明实验试样的界面缺陷以单空位为主,验证了正电子的寿命越短,湮没率越大,则自由电子密度越大.     

高速钢激光相变硬化层组织的X射线分析

本文用X射线衍射法研究了高速钢激光相变硬化层组织,以及激光工艺参数和原始组织对残余奥氏体含量的影响;并对激光相变硬化机理进行了分析。结果表明,激光相变硬化层组织由马氏体、残余奥氏体和合金碳化物组成。随着激光功率增加,扫描速度降低,残余奥氏体含量增加。激光相变硬化的本质仍然是马氏体相变。同时,晶粒细化强化,碳化物弥散强化以及激光淬火前的原始组织中的强化因素的遗传性等多种强化因素对超高硬度的获得也有贡献。     

Effects of Alkali Treatment on the Structure of Tencel Fibers

Alkali treatment can change the structures and properties of cellulosic fibers. The aim of this work was to study the mechanism of structure changes of Tencel fibers treated with different alkali concentration and two treatment methods. Raman spectrum showed that the molecular conformation of Tencel fibers remained unchanged. XRD (X-ray diffraction) indicated that the crystallinty of Tencel fibers in original length increased while that of fibers in relaxation condition remained unchanged. The average crystallite size increased and the orientation index decreased. The quasi-crystallite disassociation and recrystallization in the quasi-crystalline phase during the process of alkali treatment lead to the changes of the crystallinity and the orientation index of Tencel fibers.     

Synchrotron X-ray diffraction techniques for in situ measurement of hydride formation under several gigapascals of hydrogen pressure

The high-pressure technique is a fundamental tool for realizing novel phase transitions, chemical reactions, and other exotic phenomena. Hydrogenation is one example of a high-pressure reaction; at high pressures of several gigapascals, hydrogen becomes chemically active and reacts with metals and alloys to form hydrides. This paper covers a high-pressure study of the hydrogenation process and the synthesis of hydrides using a cubic-type multi-anvil apparatus. The experimental details of a hydrogenation cell assembly, high-temperature and highpressure generation, and an in situ observation technique are presented. These experiments are conducted with the aid of in situ synchrotron radiation X-ray diffraction measurements operated in an energy-dispersive mode in the conventional manner for time-resolved measurements and a newly developed angle-dispersive mode for observation of the crystal growth process during formation of metal hydrides. Two successful cases of high-pressure hydrogenation are presented： aluminum hydride, Al H3, and an aluminum-based alloy hydride, Al2 Cu Hx, which are potential candidates for hydrogen storage materials.     

拉曼光谱在古陶片研究中的应用

利用LRS-Ⅱ型激光拉曼光谱仪对不同年代的古陶片进行了测试研究,用X射线衍射图谱分析确定了古陶片的主要成分。测试结果表明不同年代的古陶片的主要成分相同;从所获得的拉曼光谱图可以看出,随着地质年代的不同,拉曼光谱图向高波数方向移动,对其确定古陶片的历史年代提供了很重要的依据。