论文标题
TI3ALC2最大相位的局部化学键合和结构特性，TI3C2TX MXENE通过Ti 1s X射线吸收光谱探测
Local chemical bonding and structural properties in Ti3AlC2 MAX phase and Ti3C2Tx MXene probed by Ti 1s X-ray absorption spectroscopy
论文作者
论文摘要
通过X射线吸收接近边缘结构（XANES）和扩展的X射线吸收良好结构（EXAFS）光谱镜研究，研究了过渡金属材料内的化学键合时TI3ALC2和MXENE TI3C2TX。最大相是固有的纳米胶合材料，由Mn+1xn的交替层和来自IIIA或IVA基团的A-元素的单层层组成，其中M是过渡金属，X是碳或氮。用表面终止物种替换A元素TX将分离Mn+1xn层，形成Mn+1xNTX的二维（2D）片。对于TI3C2TX，TX对应于覆盖每个2D MN+1xn-Flake的两侧的氟（F）和氧（O）。 Ti3Alc2和Ti3c2tx的Ti K-Edge（1s）Xanes表现出特征性的C 2P-Ti 3D杂交和清晰的晶体景观裂解的特征性前边缘吸收区，而Main-Edge吸收特征则来自Ti 1s-> 4P激发，仅在ti 1s-> 4p激发中表现出终结的范围降低了fccientivitivition for fccientivition fastientivition fastientivity fastientiation fastientiation for fccientiation。从EXAFS获得的协调数表明，Ti3Alc2和Ti3c2TX具有高度各向异性的，对Ti的平面内贡献很强，并且分别具有AL单层和终止物种的动态外部贡献。如温度依赖性测量所示，O贡献转移到较短的键长，而F随温度从室温升高至750°C时，F降低。
The chemical bonding within the transition-metal carbide materials MAX phase Ti3AlC2 and MXene Ti3C2Tx is investigated by X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies. MAX phases are inherently nanolaminated materials that consist of alternating layers of Mn+1Xn and monolayers of an A-element from the IIIA or IVA group in the periodic table, where M is a transition metal and X is either carbon or nitrogen. Replacing the A-element with surface termination species Tx will separate the Mn+1Xn-layers forming two-dimensional (2D) flakes of Mn+1XnTx. For Ti3C2Tx the Tx corresponds to fluorine (F) and oxygen (O) covering both sides of every single 2D Mn+1Xn-flake. The Ti K-edge (1s) XANES of both Ti3AlC2 and Ti3C2Tx exhibit characteristic pre-edge absorption regions of C 2p - Ti 3d hybridization with clear crystal-field splitting's while the main-edge absorption features originate from the Ti 1s -> 4p excitation, where only the latter shows sensitivity towards the fcc-site occupation of the termination species. The coordination numbers obtained from EXAFS show that Ti3AlC2 and Ti3C2Tx are highly anisotropic with a strong in-plane contribution for Ti and with a dynamic out-of-plane contribution from the Al monolayers and termination species, respectively. As shown in the temperature-dependent measurements, the O contribution shifts to shorter bond length while the F diminishes as the temperature is raised from room temperature up to 750 °C.
