喷雾热解法制备红色发光粉LiEu(SiO2)1/6W2O8的研究

采用喷雾热解法制备红色荧光粉LiEu(SiO₂)_1/6W₂O₈。研究了反应温度、前驱体溶液浓度、载气流速对实验结果的影响。通过扫描电镜、X射线衍射、激发和发射光谱对所制样品进行了研究,发现样品颗粒呈实心类球形、结晶度好、表面光滑、发光强度较高、粒径平均1.5μm左右且分布较窄。该类荧光粉激发主峰位于396nm,发射主峰位于615nm。LiEu(SiO₂)_1/6W₂O₈发光的色坐标为:x=0.667 9,y=0.3310,与NTSC的红色标准基本一致,该荧光粉色纯度非常高,适用于制造紫光芯片激发的白光LED。用喷雾热解法制备红色荧光粉LiEu(SiO₂)_1/6W₂O₈的研究尚未见报道。     

喷雾热解法制备的SrWO4膜的阴极射线发光

利用超声喷雾热解法制备了钨酸锶SrWO₄多晶发光膜,并研究了制备条件及掺杂对其阴极射线发光特性的影响.生成的发光膜在300℃以上退火后具有白钨矿结构,其阴极射线发光为一宽带的蓝光,包括一个位于448nm的蓝色发光带和一个位于488.6nm的蓝绿色发光带,是由阴离子络合物WO₄^2-的电荷转移跃迁引起的.发光强度随着退火温度的升高而增强,而退火气氛对其影响不大.在SrWO₄膜中掺入银离子Ag⁺和镧离子La³⁺后,不影响其发光特性,但铕离子Eu³⁺的掺入对发光特性有影响.     

Tl-based superconducting films prepared by aerosol spray deposition and thallinated in an open system

Superconducting Tl-based films were prepared on a LaAlO₃ single crystal substrate. Spray pyrolysis of Ba, Ca and Cu nitrate solutions was used for deposition of the precursor films. They were subsequently ex-situ thallinated in flowing oxygen (open system). While the superconducting Tl-2212 phase formed at an annealing temperature of 880°C, thallination at 900°C led to the formation of a Tl-2223 /Tl-2212 mixture. The amount of Tl-2223 increased with prolonged thallination, whereas the Tl-2212 phase progressively disappeared. Films prepared in such a manner were c-oriented and contained only low amounts of non-superconducting impurities. The resulting samples were characterized by XRD and SEM and their T _C values were determined by resistive four-point measurements. They showed critical temperatures in the range of T _ON = 125–135 K, T _C0 = 91–93 K. Differences between the composition and properties of the obtained films and those thallinated in closed systems under 50 kPa of oxygen are discussed in this paper. Results show that the Tl-2212 → Tl-2223 transformation proceeds at a slower rate under flowing oxygen than in a closed system. Presented at 5-th International Conference Solid State Surfaces and Interfaces, November 19–24, 2006, Smolenice Castle, Slovakia.     

傅里叶变换红外光谱法研究核辐照对三七总皂苷粉成分的影响

采用傅里叶变换红外光谱(卷积谱)法对经不同剂量y-射线核辐照的三七总皂苷粉进行了对比研究.辐照剂量不高于9kGy时,三七总皂苷粉样品的化学成分几乎没有发生变化;三七总皂苷粉样品经15kGy及以上的辐照剂量辐照后,可能产生新的化学成分;经21kGy的剂量辐照,三七总皂苷粉产生了人参、三七粉所含的普通成分(非三七总皂苷成分...     

生物柴油高压共轨喷雾特性的试验研究

应用高速摄影系统与高压共轨系统,在高压定容器内研究了生物柴油的喷雾特性,并与柴油进行了对比。结果表明,生物柴油油束形态比柴油细且长,喷雾贯穿距离比柴油大,喷雾锥角比柴油小;高的运动黏度与表面张力导致生物柴油雾化性能比柴油差。随着喷油压力的升高,生物柴油喷雾贯穿距离变长,喷雾锥角增大;随着背压的升高,生物柴油喷雾贯穿距离...     

限流沿对撞壁射流近壁区混合过程影响的实验研究(一)

本文研究了射流气体撞壁后在放有条形障碍物(以下称之为限流沿)的壁面上的发展过程．实验发现：在限流沿高度合适的情况下，射流气体与限流沿相撞后会脱离壁面形成空间流动。其中，限流沿高度、射流入射角度是决定射流气体撞击限流沿后的发展过程的重要参数，限流沿的存在成功地防止了近壁处的浓混合气层的形成．     

水雾红外隐身的冷/热目标效应

人工水雾对抗红外成像制导导弹时,会因为蒸发对流强、辐射热流弱而使水雾形成冷目标;也可能因为辐射热流过强、散热弱而形成热目标。为详细揭示该现象,以Mie理论为基础,通过辐射传递方程和能量守恒方程的耦合计算,建立了水雾红外隐身产生冷目标或热目标效应的数学模型。应用蒙特卡洛法与本文算法作对比,验证了模型的正确性;将水雾视为吸收、发射、各向异性散射介质,考虑水雾自身辐射、多重散射和各种换热过程,比如辐射热流、两相流的热传导、热对流、紊流热扩散以及雾滴蒸发等,反映了水雾热遮蔽所产生的冷/热目标效应。     

火焰原子吸收光谱法测定中草药丹参不同部位金属元素的含量

采用HNO₃-HClO₄(4∶1)混酸消化丹参的根、茎和叶,利用火焰原子吸收光谱法对消化液中的五种人体必需的金属元素K,Cu,Zn,Fe,Mg进行了测定。该方法的标准曲线的相关系数为0.998 7～0.999 7,加标回收率为99.7％～104.4％,相对标准偏差(RSD)小于2％。结果显示：K,Cu,Zn,Fe,Mg在丹参根、茎和叶的含量均有以下次序：K＞Mg＞Fe＞Zn＞Cu。丹参叶的K,Cu,Fe,Mg的含量大于根和茎。根、茎、叶中的锌铜比值均较小。该测定结果为研究金属元素K,Cu,Zn,Fe,Mg在丹参中的分布以及金属元素的含量与丹参药效之间的关系提供了有用的数据。     

Homogeneous ZnO Nanoparticles by Flame Spray Pyrolysis

Zinc oxide (ZnO) nanoparticles were made by flame spray pyrolysis (FSP) of zinc acrylate–methanol–acetic acid solution. The effect of solution feed rate on particle specific surface area (SSA) and crystalline size was examined. The average primary particle diameter can be controlled from 10 to 20nm by the solution feed rate. All powders were crystalline zincite. The primary particle diameter observed by transmission electron microscopy (TEM) was in agreement with the equivalent average primary particle diameter calculated from the SSA as well as with the crystalline size calculated from the X-ray diffraction (XRD) patterns for all powders, indicating that the primary particles were rather uniform in diameter and single crystals. Increasing the solution feed rate increases the flame height, and therefore coalescence and/or surface growth was enhanced, resulting in larger primary particles. Compared with ZnO nanoparticles made by other processes, the FSP-made powder exhibits some of the smallest and most homogeneous primary particles. Furthermore, the FSP-made powder has comparable BET equivalent primary particle diameter with but higher crystallinity than sol–gel derived ZnO powders.     

Spray Freeze-drying – The Process of Choice for Low Water Soluble Drugs?

Most of the novel highly potent drugs, developed on the basis of modern molecular medicine, taking into account cell surface recognition techniques, show poor water solubility. A chemical modification of the drug substance enhancing the solubility often decreases the pharmacological activity. Thus, as an alternative an increase of the solubility can be obtained by the reduction of the size of the drug particles. Unfortunately, it is often difficult to obtain micro or nanosized drug particles by classical or more advanced crystallization using supercritical gases or by milling techniques. In addition, nanosized particles are often not physically stable and need to be stabilized in an appropriate matrix. Thus, it may be of interest to manufacture directly nanosized drug particles stabilized in an inert hydrophilic matrix, i.e. nanostructured and nanocomposite systems. Solid solutions and solid dispersions represent nanostructured and nanocomposite systems. In this context, the use of the vacuum-fluidized-bed technique for the spray-drying of a low water soluble drug cosolubilized with a hydrophilic excipient in a polar organic solvent is discussed. In order to avoid the use of organic solvents, a special spray-freeze-drying technique working at atmospheric pressure is presented. This process is very suitable for temperature and otherwise sensitive drugs such as pharmaproteins.