亚微米高氯酸铵的制备及性能研究

采用LG-1型立式搅拌研磨机,以仲丁醇作为分散介质,通过控制研磨时间、转速、物料浓度等因素,制备了亚微米高氯酸铵(AP),并采用真空冷冻干燥技术对研磨浆料进行干燥得到产品。通过马尔文激光粒度仪、场发射扫描电子显微镜(FESEM)、X射线衍射仪(XRD)分别对制备的AP样品的粒度分布、颗粒大小和晶型进行表征,同时对制备的亚微米AP样品的摩擦感度、撞击感度以及热分解特性进行了表征。结果表明,所制备的AP样品平均粒径为460 nm;与普通工业级微米AP相比,亚微米AP样品的摩擦感度和撞击感度分别升高了20.0%和18.7%,高温分解峰峰温提前了60.1℃(升温速率10℃/min),表观活化能降低了27.3 k J/mol。同时,催化剂对亚微米AP的催化效果优于普通工业级微米AP。     

高温气-固反应水解制备八面体形四氧化三钴粉末

提出了一种以CoCl2·xH2O为原料,高温气.固反应水解制备四氧化三钴粉末的新方法,实验考察了反应温度、氯化钴结晶水含量及惰性分散介质的添加对产物的影响.采用X射线衍射、扫描电镜、激光粒度分析对样品的物相、形貌、粒度等进行了表征.结果表明:制备的粉末颗粒由{111}晶面所包围,呈八面体形貌,粒度在亚微米至微米级;反应温度越高,产物粒子的粒径越大;以CoCl2·2H2O为原料制备的粉末粒径分布范围较窄;惰性分散介质的添加改善了粉末的单分散性.简要分析了形成八面体形貌的原因及各因素对粉末形貌与粒度的影响.     

球形NH4FePO4·H2O的制备

以柠檬酸铵作络合剂通过控制结晶法制备了的球形NH4FePO4·H2O,用扫描电镜观察了颗粒的形貌和分布.通过研究加料方式、反应温度、滴加速度、搅拌速度、反应物浓度等对颗粒形态的影响,得到了制备球形NH4FePO4·H2O的最佳工艺条件.     

高温气-固反应水解制备八面体形四氧化三钻粉末

提出了一种以CoCl2·xH2O为原料,高温气-固反应水解制备四氧化三钴粉末的新方法,实验考察了反应温度、氯化钴结晶水含量及惰性分散介质的添加对产物的影响.采用X射线衍射、扫描电镜、激光粒度分析对样品的物相、形貌、粒度等进行了表征.结果表明：制备的粉末颗粒由{111}晶面所包围,呈八面体形貌,粒度在亚微米至微米级;反应温度越高,产物粒子的粒径越大;以COCl2·2H2O为原料制备的粉末粒径分布范围较窄;惰性分散介质的添加改善了粉末的单分散性.简要分析了形成八面体形貌的原因及各因素对粉末形貌与粒度的影响.     

重结晶制备超细HMX

叙述了溶剂-非溶剂法重结晶制备超细HMX.通过实验研究分析了单一改变重结晶过程中的温度、搅拌速度、溶液过饱和度等因素,对HMX晶体粒径的影响.采用粒度分析仪分析各影响因数水平下结晶体颗粒的大小,结果表明:随着重结晶过程温差越大HMX粒度越小;随着重结晶搅拌速度的增加,结晶晶体的粒径逐渐减小;随着溶液过饱和度的提高结晶体粒度越小,分布均匀;而且与溶剂的化学性质密切相关,其中温度对结晶颗粒粒径的影响最为明显.从而为制备超细HMX,进一步改善HMX化学性能提供相关资料.     

硝基胍真空结晶工艺技术研究

针对军用棒状硝基胍现有喷雾结晶制造工艺存在的平均粒度粗、粒度分布较宽、晶型规整性不好的状况,以及针状晶型不适合在发射药中应用的技术问题,对硝基胍结晶特性、晶型转变原理、结晶工艺条件进行了分析研究,提出了采用真空结晶代替喷雾结晶制取粉状硝基胍的工艺技术途径。结果表明:采用合适的抑制剂聚乙烯醇、分散剂十二烷基苯磺酸钠,同时控制硝基胍溶液浓度,可以促进结晶向棒状形貌有效转化;采用抑制剂质量分数0.05%~0.08%、分散剂质量分数0.1%、结晶真空度0.096 MPa、结晶温度33℃、直喷闪蒸结晶法等工艺条件,可制备平均粒度3.3μm以下的棒状硝基胍晶体。     

超重力反应结晶法制备纳米ZnS正交试验研究

本文采用超重力反应结晶法制备纳米硫化锌粒子,以反应物浓度、反应温度、初始pH值、RPBR转速、气液流量比为影响因素,分别选取2个水平,进行正交试验研究,考察了各因素对产品粒径影响的程度.结果表明:各因素对产品粒径影响的显著性顺序为:反应温度＞气液流量比＞RPBR转速＞初始pH值＞反应物浓度.其中,反应温度和气液流量比对产品粒径有显著影响,RPBR转速和初始pH值对产品粒径有一定影响,而反应物浓度则基本无影响.这为制备可控粒径的纳米ZnS提供了理论依据.     

亚微米级钛酸钡的晶相与形貌调控及其立方-四方晶相转变

以α钛酸和八水合氢氧化钡为原料,采用低温固相法制备出均一性良好的亚微米级四方相钛酸钡,研究了焙烧工艺(焙烧温度、焙烧时间、升温速率和焙烧方式)对钛酸钡微观形貌结构、晶相含量、晶粒大小和晶相转变温度的影响。通过SEM、XRD和Raman等手段对钛酸钡样品进行了表征,其结果表明四方相钛酸钡晶粒大小为亚微米级,在300℃由亚稳态立方相钛酸钡晶相转变而来,600℃时钛酸钡晶粒以立方体形貌为主,700℃时钛酸钡粉体中以四方相钛酸钡为主。无论是晶相转变温度还是焙烧温度均较传统温度显著降低。     

前驱体对纳米AlOOH水热制备过程中团聚的影响

为了提高水热产物的分散性,消除水热合成过程中纳米AlOOH颗粒的软团聚和硬团聚,采用振动搅拌的方式制备了前躯体,在水热合成之前进行了离心处理,制备了分散性良好的纳米AlOOH晶粒。用高分辨透射电镜观察了样品形貌,用衍射仪分析了纳米AlOOH晶体点阵结构,用亚微米粒度及电位分析仪检测产物颗粒的表观团聚平均粒径及其分布,以此评价颗粒的团聚行为。通过分析研究探讨了前躯体制备方式对水热产物形貌的影响机理,揭示了化学位差和纳米粒子具有的较高的表面能是导致软团聚的根本原因,指出了杂质离子在结晶过程中的极性配位是导致硬团聚的实质所在。     

中空纤维膜促进成核的冷却结晶过程

利用中空纤维膜组件的高单位体积换热面积和优异的传热能力,实现膜界面骤冷促进成核,并利用膜界面流场的综合作用力,完成溶液冷却结晶的自动成核和晶种添加功能.以硫脲水溶液作为研究体系,研究PTFE中空纤维膜促进冷却结晶过程.结果表明,利用膜诱导晶核产生的时间为195 s,无膜参与的自发成核冷却结晶诱导时间为280 s.同时,在相同的温度、原料浓度以及搅拌速度下,由于利用膜促进成核的冷却结晶能够有效调控晶种产生的速率和数量并实现自动输送,制备的晶体产品形貌完整、纯度高(99.5%)、平均粒径大(1.35 mm,相比于其他无膜技术提高30%以上)且粒径分布集中.     

Preparation,characterization and dissolution behavior of artemisinin microparticles

In the present study, a modified 4-fluid nozzle spray drier was used to prepare microparticles of a poorly water soluble drug, artemisinin with the aim of improving its solubility. We also investigated the effect of process variables on the physical properties and dissolution rate of spray dried artemisinin. A full factorial experimentally designed study was performed to investigate the following spray drying variables: inlet temperature and feed concentration. The artemisinin powder and spray dried artemisinin microparticles were characterized by scanning electron microscopy (SEM), differential scanning calorimetric (DSC), X-ray diffraction (XRD) and dissolution. SEM study suggested that the inlet temperature and feed concentration impacted on the particle size of the spray dried particles. The crystallinity of spray dried particles was slightly decreased with increasing inlet temperature and concentration. The dissolution of spray dried particles was markedly improved as compared to commercial artemisinin. A dissolution surface-response model was used to elucidate the significant and direct relationships between drug feed concentration and inlet temperature on one hand and dissolution on the other hand. The best dissolution was found to be 117.00 ± 5.15 μg/mL at the drug feed concentration of 10 g/L and inlet temperature of 140 °C.     

Removal of Acid Violet 17 from aqueous solutions by adsorption onto activated carbon prepared from sunflower seed hull

The adsorption of Acid Violet 17 (AV17) was carried out using various activated carbons prepared from sunflower seed hull (SSH), an agricultural solid waste by-product. The effect of parameters such as agitation time, initial dye concentration, adsorbent dosage, pH and temperature were studied. The Langmuir and Freundlich isotherm models were applied and the Langmuir model was found to best report the equilibrium isotherm data. Langmuir adsorption capacity was found to be 116.27 mg/g. Kinetic data followed pseudo-second-order kinetics. Maximum colour removal was observed at pH 2.0. It was observed that the rate of adsorption improves with increasing temperature and the process is endothermic. The adsorbent surface was analysed with a scanning electron microscope. The results indicate that activated sunflower seed hull could be an attractive option for colour removal from dilute industrial effluents.     

Toluidine red nanoparticles and their application in electrophoretic display

Toluidine red pigment nanoparticles were prepared by anti-solvent precipitation and were modified by different surfactants aimed to use as the electrophoretic particles. Experimental conditions have been discussed in this paper including the effect of different surfactants, the concentration of surfactants, the reaction temperature and the agitation rate. Binary mixtures of organic solvents have been selected as suspending medium to improve the dispersion stability of the prepared particles. The produced nanoparticles have been characterized by scanning electron microscopy, laser diffractometer and electrophoretic display measuring system. The results indicated that the prepared particles modified by alkyl hydroxy oximido acid are in the average size of 80 nm with a spherical shape within narrow particle size distribution. The optimum content of AHOA, reaction temperature agitation rate are 3.75 g/L, 20 degrees C and 900 rpm, respectively. The prepared nanoparticles exhibit superior electrophoretic properties. Finally, the sedimentation of prepared particles dispersed into binary mixtures of tetrachloroethylene (C2Cl4) and cyclohexane is 4.76% for 2 months.     

超临界水热制备LiFePO4及煅烧碳包覆改性研究

本文以FeSO_4、H_3PO_4和LiOH为原料,采用超临界水热过程制备了亚微米级LiFePO_4颗粒.在此基础上,为了提升制备的LiFePO_4正极材料的物理和电化学性能,对其进行了后续煅烧碳包覆改性研究.同时,通过XRD、SEM、充放电测试、CV和EIS测试手段,对LiFePO_4正极材料改性前后的结构、形貌和电化学性能进行了表征.结果表明:后续固相煅烧碳包覆改性能够显著改善LiFePO_4的结晶性能,减小颗粒粒径,降低电荷传递阻抗,以及大幅度地提升放电容量和循环性能;以PVP为模板剂、蔗糖为碳源,700℃煅烧1 h得到的LiFePO_4/C颗粒粒径小、分布均一,室温0.2 C倍率的首圈放电比容量为153.1 mAh/g,1 C倍率充放电时,放电比容量可保持在144.2 mAh/g,1 C循环50次,容量保持率达到97.1%.     

Co-deposited Zn-submicron sized Al2O3 composite coatings: Production,characterization and micromechanical properties

In this study, co-deposition of zinc (Zn)-submicron sized alumina (Al₂O₃) particles via electrodeposition method was investigated. Composite coatings were produced using different coating parameters such as current density, pH, temperature, agitation type, and ceramic powder content of the bath solution. Structural and microstructural properties of the coatings were characterized by X-ray diffractometer (XRD) and scanning electron microscopy with electron dispersive spectroscopy (SEM–EDS). Mechanical properties of the coatings were evaluated by dynamic ultra-micro hardness (DUH) tester, a micro-indentation technique, in detail. It was found that, co-deposition of submicron sized Al₂O₃ particles and Zn metal was successfully achieved via electrodeposition method without any chemical interaction between the ceramic particles and the electrolyte. Comparison of SEM images belonging to the coatings fabricated to those of the reference coatings revealed that homogenous grain structure was obtained. Finally, a boost in the micromechanical properties of the coatings was gained by changing the effective co-deposition parameters such as current density and particle content in the electrolyte.     

Effect of particle size on the in vitro bioactivity,hydrophilicity and mechanical properties of bioactive glass-reinforced polycaprolactone composites

Polycaprolactone (PCL) composite films containing 5 wt.% bioactive glass (BG) particles of different sizes (6 μm, 250 nm, < 100 nm) were prepared by solvent casting methods. The ultra-fine BG particles were prepared by high-energy mechanical milling of commercial 45S5 Bioglass® particles. The characteristics of bioactive glass particles were studied by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and X-ray diffraction (XRD) methods. In vitro bioactivity of the PCL/BG composite films was evaluated through immersion in the simulated body fluid (SBF). The films were analyzed by FE-SEM, energy dispersive spectrometry (EDS), XRD, and atomic force microscopy (AFM). The mechanical properties of highly-porous PCL/BG composites were examined on cylindrical specimens under quasi-static compression load. It was found that partial crystallization of amorphous BG particles during a prolonged mechanical milling occurred and calcium silicate (CaSiO₃) and sodium calcium silicate (Na₂CaSiO₄) phases were formed. The introduction of submicron BG particles (250 nm) was shown to improve the bioactivity of PCL films. In contrast to BG microparticles, the submicron BG particles were distributed on the film surfaces, providing a high surface exposure to SBF with an improved nanotopography. A notable increase in the stiffness and elastic modulus of the composite was also obtained. As compared to submicron BG particles, lower bioactivity and elastic modulus were acquired for PCL/BG nanoparticles. It was also shown that in spite of high specific surface area of the nanoparticles, partial crystallization during mechanical milling and agglomeration of the nanoparticles during processing decrease the bioactivity, hydrophilicity and mechanical response of the BG-reinforced PCL composites.     

Size control for fullerene C60 nanocrystals during the high temperature and high pressure fluid crystallization process

The preparation and size control for mono-dispersed fullerene C₆₀ fine particles was successfully achieved during the high temperature and high pressure fluid (HTPL) crystallization process, in which acetone was used as the HTPL solvent and pure water or the mixture of acetone and water as the cooling solvent. The prepared fullerene C₆₀ particles had spherical shape and narrow size distribution with the average size ranging from 44 nm to 110 nm depending on the various experimental conditions, such as fluid temperature, solvent flow rate, system pressure and the ratio of acetone and water in cooling solvent. The products were characterized by using X-ray powder diffraction (XRD), scan electron microscopy (SEM), dynamic light scattering technique (DLS) and UV–VIS spectrum, respectively. And the size effect of such fullerene C₆₀ nanocrystals was confirmed.     

Seed layer-free electrodeposition of well-aligned ZnO submicron rod arrays via a simple aqueous electrolyte

A potentiostatic electrodeposition technique was used to directly fabricate large-scale, well-aligned, and single-crystalline submicron ZnO rod arrays on tin doped indium oxide glass substrate without a pre-prepared seed layer of ZnO from an aqueous solution only containing zinc nitrate. The effects of electrochemical parameters, such as electrodeposition potential, electrodeposition duration, solution temperature, and precursor concentration, on the orientation, morphology, aspect ratio, and growth rate of ZnO rod arrays were systematically investigated. Results show that submicron ZnO rod arrays with (0 0 0 2) preferred orientation and perfect crystallization were obtained when electrodeposition potential was in the range from −0.6 to −1.1 V and solution temperature was controlled above 60 °C. Both high solution temperature and low precursor concentration resulted in the decrease in rod diameters. Photoluminescence measures showed that small diameter and nanotips of ZnO rod arrays should be responsible for strong and sharp ultraviolet emission in the room temperature photoluminescence spectra.     

Effect of structural transformation on the electrical properties for Ge1Sb2Te4 thin film

Dependence of electrical properties of phase change Ge₁Sb₂Te₄ thin film on structural transformation was investigated. The electrical resistivity of the film decreases with increasing annealing temperature with a steep drop at ∼ 230 °C (the second crystallization temperature), at which the structure of Ge₁Sb₂Te₄ changes from face-centered cubic to trigonal state. The steep drop of resistivity at the second crystallization temperature is mainly due to the increase of hole density within the p-type film, according to Hall measurement. The crystallization process has been followed by in situ resistance measurement at various annealing temperatures. Transmission electron microscope and atomic force microscope were also employed to study the film.