Ni-Co合金快淬过程的分子动力学模拟

采用分子动力学模拟熔体旋淬技术的合金快淬过程,在不同的冷却速度下研究Ni-Co合金在快淬后的结构特征.模拟发现:Ni-Co二元合金的凝固过程对冷却速率的变化较为敏感,体系对形成非晶对冷却速率要求较高,约在80 K/ps以上,可以采用增加添加元素的方法来降低材料对冷却速率的要求;在75 K/ps的冷却速率下合金最终完全晶...     

溅射功率对Mo薄膜微结构和性能的影响

 实验采用直流磁控溅射沉积技术在不同溅射功率下制备Mo膜,研究了不同溅射功率下Mo膜的沉积速率、表面形貌及晶型结构,并对其晶粒尺寸和应力进行了研究。利用原子力显微镜观察样品的表面形貌发现随着溅射功率的增加,薄膜表面粗糙度逐渐增大。X射线衍射分析表明薄膜呈立方多晶结构,晶粒尺寸为14.1～17.9 nm;应力先随溅射功率的增大而增大,在40 W时达到最大值(2.383 GPa),后随溅射功率的增大有所减小。     

Amphiphilic phosphoprotein-controlled formation of amorphous calcium carbonate with hierarchical superstructure

Amorphous calcium carbonate (ACC) plays important roles in biomineralization, and the phosphoproteins extracted from biogenic stable ACC can induce and stabilize synthetic ACC in vitro. Here, mineralization of square-shaped ACC plates with micrometer-sized channels has been reported in the presence of the amphiphilic phosphoprotein casein. Casein can be assumed to take a key role during ACC plate formation, where it serves as an effective stabilization agent for ACC and assembles spherical ACC particles into ACC plates. The stabilizing effect of casein arises from the electrostatic attraction between phosphate groups as well as carbonate groups (especially the former) and the calcium ions, preventing the transformation from unstable ACC to the more stable crystalline phase of CaCO(3). The assembling effect of casein mainly comes from the hydrophobic interaction between casein molecules bound on CaCO(3) particle surface. The inclusion of casein in ACC plates revealed by the thermogavimetric analysis confirms the proposed stabilizing and assembling mechanism. The ability to fabricate such novel hierarchical structured ACC holds the promise for creating more complex micro- and nanostructured materials by use of biological proteins with special structure.     

Effects of molecular weight,heating rate,synthetic temperature and sintering duration on electrochemical properties of a LiFePO<Subscript>4</Subscript>/C cathode material pyrolyzed from lithium polyacrylate

A LiFePO₄/C composite was obtained by a polymer pyrolysis reduction method, using lithium polyacrylate (LiPAA) as carbon source and fractional lithium source, and FePO₄·2H₂O as iron and phosphorus source. The structure of the LiFePO₄/C composites was investigated by X-ray diffraction (XRD). The micromorphology of the precursors and LiFePO₄/C powders was observed using scanning electron microscopy (SEM). Laser particle analyzer and BET were also used to characterize the materials. It was found that the micromorphology, particle size distribution and specific surface area of LiFePO₄/C composites were greatly influenced by the molecular weight of LiPAA. The electrochemical properties of the LiFePO₄/C composites were evaluated by cyclic voltammograms (CVs), electrochemical impedance spectra (EIS) and constant current charge/discharge cycling tests. The results showed that the molecular weight of LiPAA, heating rate, synthetic temperature and sintering duration directly affected the electrochemical properties of LiFePO₄/C composites. The sample with the optimized electrochemical properties were obtained in the following conditions, i.e., LiPAA with the molecular weight of 20,000, heating rate of 10 °C min⁻¹, synthetic temperature of 700 °C and sintering duration of 15 h.     

Silver nanoplates: controlled preparation, self-assembly, and applications in surface-enhanced Raman scattering

Silver nanoplates were prepared in a dual reduction system with NaBH₄ and sodium citrate both as reducing agents. And then the as-prepared nanoplates could be growing up through multistage growth methodology. The average edge length of Ag nanoplates can be tailored from 40 nm to 260 nm without changing their shape, crystallinity, and the average thickness. Furthermore, the effectiveness of these silver nanoplates as substrates prepared by the silanization self-assembly method toward surface-enhanced Raman scattering (SERS) detection was evaluated by using 4-aminothiophenol (4-ATP) and rhodamine 6G (R6G) as probe molecules. It was found that the enhancement ability of the silver nanoplates film is remarkable lower than that of the spherical silver nanoparticle film. The reason is attributed to the electromagnetic mechanism and chemical mechanism. This work will be of great significance in understanding the SERS enhancement mechanism and in the fabrication of nanoparticle films for biosensing.     

三聚氰胺-甲醛气凝胶模板的结构与热稳定性

采用溶胶-凝胶法合成出三聚氰胺-甲醛（MF）有机气凝胶,并通过N2吸附、红外光谱以及热重-质谱联用等实验技术对该气凝胶的多孔形态、结构特性和热稳定性进行了表征。结果表明:MF气凝胶是一种连续的、相互贯通的3维多孔网络结构材料,比表面积约842 m2/g,平均孔径为16 nm左右;热解产生了NO, H2O, NH3, NO2, CO2和CH4气体,很好地诠释了各阶段失重,其总失重高达97%,有望作为制备3维nm级多孔材料的模板。     

ICF冷冻靶微管充气过程中气体压力测量

利用自主设计的冷冻靶微管充气系统,通过在常温环境下向靶盒注入氘气,研究了充气管两端压强差与充气管长度、充气速率及充气时间之间的相互关系。研究表明:微管注入法充气过程中,充气管两端的压强差先增大然后减小最终趋于0;充气管长度越小,充气速率越大,充气管两端压强差达到平衡所需的时间越短。该实验结果与根据修正后的Hagen-Poiseuille方程所得到的理论计算值相吻合。     

超高效液相色谱-串联质谱联用法同时检测降糖类和减肥类保健品中20种非法添加的化学降糖药物

建立了一种利用超高效液相色谱-质谱联用同时快速筛查、检测降糖类和减肥类保健品中20种非法添加化学成分的方法。试样用甲醇提取后,经Poroshell 120 EC-C18柱(100 mm×2.1 mm,2.7 μm)分离,以5 mmol/L乙酸铵和乙腈为流动相梯度洗脱,采用电喷雾离子源正、负离子模式切换、多反应监测模式检测。20种非法添加化合物的峰面积与质量浓度均呈良好的线性关系,相关系数均大于0.99,回收率均在75.9%~114.0%范围内,相对标准偏差均不高于11.3%,检出限均在0.3~1.5 μg/L范围内。该方法快速、简便、灵敏、重现性好,为打击降糖类和减肥类保健品中非法添加化学降糖药提供了有力的依据。     

全长粘结锚杆在岩质边坡中的受力形式分析

基于空间一点受力的位移解形式--Mindlin 位移解, 结合已有文献对节理面位置处全长粘结锚杆受力的假想形式, 将边坡下滑力简化为作用在锚杆上的集中力, 推导出锚杆沿杆长方向的轴力、剪应力的表达形式. 将推导结果在岩质边坡中进行应用, 得出不同岩体类型岩质边坡锚杆沿杆长方向受力的轴力、剪应力图示.     

间苯三酚-乙醛有机气凝胶的制备与表征

 以碳酸钠为催化剂,乙醇为溶剂,间苯三酚 乙醛为反应前躯体,经溶胶 凝胶、交联老化、二氧化碳超临界干燥制备出间苯三酚-乙醛(PA)有机气凝胶。扫描电镜观察和N2吸附测试结果表明：气凝胶具有较高的比表面积,是一种连续nm级３维网络结构的多孔材料,其比表面积为1 210 m²/g,平均孔径为11 nm,与传统有机气凝胶相比,提高了比表面积,一定程度上实现有机气凝胶的扩孔。