Dextran-modified iron oxide nanoparticles

Dextran-modified iron oxide nanoparticles were prepared by precipitation of Fe（Ⅱ） and Fe（Ⅲ） salts with ammonium hydroxide by two methods. Iron oxide was precipitated either in the presence of dextran solution, or the dextran solution was added after precipitation. In the second method, the iron oxide particle size and size distribution could be controlled depending on the concentration of dextran in the solution. The nanoparticles were characterized by size-exclusion chromatography, transmission electron microscopy and dynamic light scattering. Optimal conditions for preparation of stable iron oxide colloid particles were determined, The dextran/iron oxide ratio 0-0,16 used in precipitation of iron salts can be recommended for synthesis of nanoparticles suitable for biomedical applications, as the colloid does not contain excess dextran and does not coagulate.     

La1-xNdxSrCoO4催化剂的合成及其催化性能

采用聚丙烯胺溶胶-凝胶法制备了类钙钛矿La1-xNDxSrCoO4(x=0.1～0.9)复合氧化物催化剂,考察了其对CO和C3H8的催化氧化活性,并运用XRD、IR和TPR等手段对催化剂进行了表征.结果表明,所制备的样品均具有K2NiF4型结构,适量Nd2O3的加入增加了LaSrCoO4的催化活性,使LaSrCoO4催化剂粒度变小、晶格畸变率变大及与氧的结合能力减弱,从而有利于CO和C3H8氧化活性的提高.     

不同溶剂体系中改性氢氧化镁的分散行为

研究了不同的表面改性剂对超细氢氧化镁的表面改性.并分别以水和乙醇为溶剂,研究了表面改性后氢氧化镁的分散行为.实验结果表明,以水为溶剂的体系,六偏磷酸钠分散性能最好,而以乙醇为溶剂,硅烷偶联剂KH-550分散性能最好,其用量为基体量的5%左右,可使制备的超细氢氧化镁粒径达到0.2 μm尺度以下.试验结果对进一步认识超细氢氧化镁的性质及其应用具有重要意义.     

纳米碳酸锌的制备和热分解动力学参数的测定

Nanosized zinc carbonate was prepared in the droplet of nano-reactor based on microemusion. The influences of the concentration of the surfactant and reactant on the diameter of nanoparticles were studied and the kinetic pa-rameters of thermal decomposition reaction were determined. It can be shown from experimental results， the di-ameter of the droplet in the microemulsion which have dissolved reactant zinc nitrate and sal volatile is between 4.9nm and 7.7nm， 6.2nm and 12.4nm， respectively. Nanosized zinc carbonate prepared by the method of mi-croemusion has shown good dispersion， narrow distribution and light agglomeration. The particle size of nanosized zinc carbonate is between 5nm and 40nm， and its kinetic parameters of thermal decomposition reaction-activation energy E and reaction order n are 110kJ·mol^-1 and 0.9， respectively.     

WS2 超细粉体的固相法合成

WS2 超细粉体的固相法合成;WS2;固相反应;过硫系数;高能球磨;粒度     

碳酸氢铵沉淀法制备氧化钇粉体时反应条件对产物粒度的影响

研究了碳酸氢铵沉淀法的反应条件对氧化钇粒度的影响,探讨了粒度变化规律。发现在沉淀反应中,晶型碳酸钇铵的形成与否是影响氧化钇粒度的关键因素。在较低的反应温度下,当碳酸氢铵和氯化钇的浓度大于0.25mol·L-1,摩尔比大于5,陈化时间大于60min时得到碳酸钇铵沉淀,经煅烧可获得粒度(D50)大于1μm的氧化钇。当反应物浓度较低、摩尔比小,陈化时间较短时得到无定型碳酸钇沉淀,煅烧沉淀可获得粒度(D50)小于0.5μm的氧化钇。实验证明选择适当的沉淀反应条件,可制备D50在0.3～10μm范围内的不同粒度级别的氧化钇粉体。     

氧化钇粒度控制与测定

用氨水或碳酸氢铵与氯化钇溶液反应生成沉淀，煅烧沉淀制备了D50为0．45μmt 2-10μm的各种粒径的氧化钇粉末。分别采用Coulter MultisizerⅡ和90Plus粒度仪测定微米和亚微米级氧化钇粉体粒度，研究了分散剂，待测样品量，分散时间等因素对亚微米级氧化钇粉体粒度测量精度的影响。     

Nd-Fe-B磁体烧结过程晶粒长大行为的研究

定量描述了Nd-Fe-B磁体烧结过程晶粒长大行为，分析了烧结温度、烧结时间、合金粉末粒度及其分布对烧结过程晶粒长大的影响，讨论了烧结过程晶粒长大机制。在Nd-Fe-B磁体烧结过程开始之后的0—1h时间区段，晶粒长大迅速；随着烧结时间的延长，晶粒长大速度减小。合金粉末平均粒度增大，或者合金粉末粒度分布范围增宽，显著促进Nd-Fe-B磁体烧结过程中晶粒的长大。在Nd-Fe-B磁体的烧结过程中，存在两类晶粒长大机制，即Nd2Fe14B颗粒的溶解与析出、Nd2Fe14B颗粒的并合与长大。Nd2Fe14B颗粒的并合与长大不仅使磁体的平均晶粒尺寸增大，也使晶粒尺寸分布范围增宽，是烧结Nd-Fe-B磁体显微组织中出现异常大晶粒的根本原因。     

Preparation of Small Particle Sized ZnAl-Hydrotalcite-Like Compounds by Ultrasonic Crystallization

Ultrasonic technology has been intensively studied recently due to its special features. In this paper, an ultrasonic crystallization method was introduced for the preparation of ZnAl-Hydrotalcite-Like compounds (ZnAl-HTLcs). Samples with high crystallinity, small particle size and narrow particle size distribution were obtained and fully characterized using conventional techniques of XRD, FT-IR and TGDTA. The results prove that both ultrasonic frequency and ultrasonic power have effects on the sizes of the product particles. By varying the ultrasonic power from 250 W to 88 W, with the ultrasonic frequency fixed at 59 kHz, the median particle size of the samples increased from 0.37 μm to 0.82 μm. By altering the hydrothermal treatment time from 1 h to 5 h at 110℃, the median particle size of ZnAl-HTLcs synthesized via ultrasonic crystallization increased from 0.88 μm to 1.11 μm.     

烟叶样品在进行近红外分析测试前的样品处理方法

本发明涉及烟叶样品在进行近红外分析测试前的样品处理方法，属烟草样品的近红外光谱分析测试技术领域。本发明的烟叶样品在进行近红外分析测试前的样品处理方法包括干燥粉碎及压样三步骤，其中：a．粉碎步骤为：将干燥的样品取出并静止10S后放入家用食物搅拌器中进行粉碎处理，粉碎时间为20-30S，粉碎粒度达375μm以下；b．压样步骤为：将质量为300g的重锤自然平稳置入装有粉碎后样品的样品杯中，取出重锤，随后将样品杯放入仪器样品池内进行测量10min就能完成一个烟叶样品的测试工作。本发明具有操作简单、节省时间、成本低、效率高等优点。