炉内成球法制备PVA涂层理论模拟研究

根据炉内成球法制备PVA涂层原理,建立了炉内成球法在PS微球表面制备PVA涂层的数学模型,并利用数值方法进行了求解,研究了初始PS壁厚和直径、载气种类、炉内温度、PVA含量等实验条件的影响。计算结果表明,包裹PS微球的PVA水溶液复合微球在下落过程中速度迅速增加,短时间内达到最大值后又逐渐降低;复合微球的PVA水溶液涂层厚度逐渐减少,微球表观密度降低;炉内温度较低时,PVA涂层不易烘干;空气和纯Ar做炉内气氛时,微球烘干时间延长,而在He和Ar混合气体中,随着He含量增加,微球烘干时间缩短;小直径PS微球及高含量PVA溶液有利于制备厚的PVA涂层。

炉内成球法制备SiC空心陶瓷微球

采用干凝胶法,以聚碳硅烷（PCS）为原料,通过炉内成球技术制备了SiC空心陶瓷微球。并利用TG、IR、SEM、XRD等方法对陶瓷微球进行了成键结构、表面形貌等分析,讨论了有机聚合物的陶瓷化过程机理。结果表明,干凝胶成球技术能利用经纯化处理的聚碳硅烷在500~600℃下得到SiC空心陶瓷微球,采用乙醇作为发泡剂可使PCS凝胶粒子得到良好发泡效果,提高载气中氦气含量至50%~80%可提高干凝胶粒子在吸热阶段的升温速率,微球经辐照后在850℃下碳化生成以β-SiC为主要相结构的球壳,球壳具有较好的表面平整度。

炉内成球技术制备PS-PVA双层球

本工作研究采用炉内成球技术制备惯性约束聚变用靶丸聚苯乙烯-聚乙烯醇（PS-PVA）双层球。以乳液法制备PS微球，利用炉内成球技术在PS微球表面制备PVA层。研究表明，在PVA质量浓度为5%、炉内为空气、炉温473-523 K条件下，可制备出PS-PVA双层球。双层球直径范围250-550μm，PVA层厚度范围1.0-2.4μm，PS-PVA双层球表面光洁度3-10 nm，微球充氩气的最低温度350-360 K，室温条件下对氘气的保气半寿命1-5 h。

煤矸石陶粒滤料的制备及性能研究

以煤矸石为原料,分别采用破碎法和成球法制成滤料生料,经快升温或慢升温焙烧获得陶粒滤料。对所制备陶粒滤料的气孔率、气孔孔径和酸碱可溶率等指标进行了分析比较。结果表明:各种陶粒滤料制品均性能优良;制品的气孔率都随着焙烧温度的升高由小变大,又逐渐降低,成球法制品的气孔率普遍要高于破碎法;快烧制品的气孔孔径分布范围较窄,慢烧制品的气孔孔径分布范围则很宽,2种焙烧方式所得制品中孔径大于100μm的气孔都随着焙烧温度的升高而增加;制品的酸碱可溶率均随焙烧温度的升高而降低。实际生产时,可根据煤矸石特性、产品的性能要求、生产成本等确定煤矸石陶粒滤料的制备工艺。

煤矸石制备轻质骨料的加工试验研究

煤矸石经破碎、粉磨与粉煤灰等其它工业固体废物混合、成球、干燥 ,或煤矸石直接破碎 ,经焙烧、膨胀 ,可制成具有一定孔隙率、技术指标符合要求的轻质骨料。讨论了这两种方法的特点 ,指出破碎法轻质骨料受原料影响较大 ,但成本低 ;成球法 (可塑法 )可根据要求调整配方 ,灵活 ,不受原料限制 ,但成本较高。

激光烧结快速成型用聚丙烯粉末的制备研究

文章采用溶剂沉淀法和诱导成球法制备聚丙烯粉末。采用溶剂沉淀法,以聚丙烯颗粒为原料,当溶剂为甲苯,析出溶剂为无水乙醇16.7%,搅拌速率为430 r/min,得到最佳的聚丙烯粉末产率为0.682和堆积密度为0.223。采用诱导成球法,将外形不规则的聚丙烯粉碎粉制备出形状规则聚丙烯微球粉末,得到的微球粉末的堆积密度比溶剂沉淀粉末和粉碎的无规粉末堆积密度分别提高了0.058和0.035。

塑料微球表面制备聚乙烯醇涂层研究进展

在聚苯乙烯(PS)-聚乙烯醇(PVA)-碳氢聚合物(CH)三层球的设计中制备PVA涂层的方法主要包括乳液微封装法、炉内成球涂层法、浸(旋)涂法、界面缩聚法及喷涂法等,前三种方法目前最为常用。总结了前三种制备PVA涂层方法的优缺点及目前的研究和制备现状。乳液微封装法适合于500μm以下小尺寸双层球的制备,具有微球成活率高、产品质量较好等优点,但制备过程受人为因素影响较大,且不易制备大直径双层球。炉内成球涂层法也适用于小尺寸双层球的制备,其制备周期短,但液滴发生器的设计苛刻,PVA层的均匀性差,且不易制得较大尺寸的双层球。浸(旋)涂法可制备1000μm以上的大直径双层球,但该方法中影响PVA涂层铺展的因素较多,得到的PVA涂层均匀性较差,且涂层很薄。

Morphology-controlled synthesis and photocatalytic properties of K_(1.9)Na_(0.1)Ta_2O_6·2H_2O

The controllable synthesis of tantalate K1.9Na0.1Ta2O6·2H2O has been successfully achieved by a two-step technique,namely,the molten salt and hydrothermal methods,at a low temperature. By simply varying the KOH concentration in the hydrothermal process,K1.9Na0.1Ta2O6·2H2O particles with spherical,cuboctahedral,and durian-like morphologies were synthesized. The photocatalytic activity of the obtained samples for the degradation of rhodamine B was studied under ultraviolet light,which indicates that the photocatalytic properties of the samples are highly dependent on their morphologies. The K1.9Na0.1Ta2O6·2H2O nanospheres,with rough surfaces and the highest specific surface area,exhibit the best performance. The present work provides a unique approach for the controlled synthesis of tantalate photocatalysts,which are difficult to achieve through other synthetic approaches.

Influence of chloride salts on hydrogen generation via hydrolysis of MgH_2 prepared by hydriding combustion synthesis and mechanical milling

The effects of chloride salts(NaCl,MgCl2and NH4Cl)on the hydrolysis kinetics of MgH2prepared by hydridingcombustion synthesis and mechanical milling(HCS+MM)were discussed.X-ray diffraction(XRD)analyses show that high-purityMgH2was successfully prepared by HCS.Hydrolysis performance test results indicate that the chloride salt added during the millingprocess is favorable to the initial reaction rate and hydrogen generation yield within60min.A MgH2?10%NH4Cl composite exhibitsthe best performance with the hydrogen generation yield of1311mL/g and a conversion rate of85.69%in60min at roomtemperature.It is suggested that the chloride salts not only play as grinding aids in the milling process,but also create fresh surface ofreactive materials,favoring the hydrolysis reaction.

The spatial distribution characteristics of shallow fissures of a landslide in the Wenchuan earthquake area

Shallow fissures, being the main infiltration paths of fluid on the surface of a slope, played an important role in the whole process of a landslide. However, the spatial distribution characteristics of fissures in the slope are difficult to be determined. In this study, we attempted to characterize the variation pattern of slope fissures along depth in the Wenchuan earthquake area in Sichuan Province by combining engineering geological investigation, geomorphologic analysis and geophysical investigation. The geophysical methods that were used in this study include Multichannel Analysis of Surface Wave(MASW), Ground Penetrating Radar(GPR) and Electrical Resistivity Tomography(ERT). The results suggested that geophysical parameters(shear wave velocity, electromagnetic signals attenuation and resistivity) could provide valuable information for the spatial network of shallow fissures. Through the verification by engineering geological survey and geophysical sensitivity analysis, this work highlighted that MASW was the most appropriate technique to delineate the propagation of shallow fissures in a gravel soil slope.

RELATIVE PRINCIPLE COMPONENT AND RELATIVE PRINCIPLE COMPONENT ANALYSIS ALGORITHM

In this letter,the new concept of Relative Principle Component (RPC) and method of RPC Analysis (RPCA) are put forward. Meanwhile,the concepts such as Relative Transform (RT),Ro-tundity Scatter (RS) and so on are introduced. This new method can overcome some disadvantages of the classical Principle Component Analysis (PCA) when data are rotundity scatter. The RPC selected by RPCA are more representative,and their significance of geometry is more notable,so that the application of the new algorithm will be very extensive. The performance and effectiveness are simply demonstrated by the geometrical interpretation proposed.

Shallow Donor Impurity Ground State in a GaAs/AlAs Spherical Quantum Dot within an Electric Field

Using the configuration-integration methods （CI） [Phys. Rev. B 45 （1992） 19], we report the results of the Hydrogenie-impurity ground state in a GaAs/AIAs spherical quantum dot under an electric field. We discuss the variations of the binding energies of the Hydrogenic-impurity ground state as a function of the position of impurity D, the radius R of the quantum dot, and also as a function of electric field F. We find that the ground energy and binding energy of impurity placed anywhere depend strongly on the position of impurity. Also, electric field can largely change the Hydrogenic-impurity ground state only limiting to the big radius of quantum dot. And the differences in energy level and binding energy are observed from the center donor and off-center donor.

Conceptual Framework for an Integrated Method to Optimize Sustainability of Engineering Systems

It is necessary to change the current dynamic of growth, to assure that future generations can satisfy their needs. Sustainable development and global sustainability are two concepts that have achieved great importance in almost every sector of activity. There is a wide range of methods and models for sustainability assessment. Nevertheless, it is necessary to go beyond evaluation, looking for sustainability optimization. In spite of this, little work has been done on the latter field. The authors present here a conceptual proposal for an integrated method to optimize sustainability of engineering systems, based on the MIVES （integrated value method for evaluating sustainability） method. For a better understanding of the method, its essential steps for optimizing an energy sub-system are summarized （shell-and-tube heat exchanger）.

Genesis and Quality of Groundwater in the Southeastern Region of Southern Vietnam

The origin and quality of groundwater in the Southeastern region （belongs to Southern Plain） were identified by using isotopic techniques and geochemical analysis. Groundwater samples were collected from 7 aquifers： the Holocene, upper Pleistocene, middle Pleistocene, lower Pleistocene, upper Pliocene, middle Pliocene and Miocene aquifers. The water isotopic compositions （82H and 8180） were determined to elucidate the origin and the interaction between surface water and groundwater studies. Transit time （age） of the groundwater samples was determined to explain the direction of groundwater flow. The dating techniques included 3H and ^14C isotopes measurement, followed by a correction for the initial ^14C-activity by the ^13C-composition （^13C） in TDIC （Total Dissolved Inorganic Carbon）. Geochemical parameters of the groundwater samples were measured either directly in the field or in the laboratory. The results showed that the groundwater from the Holocene and upper Pleistocene aquifers was most recharged from the local meteorological and hydrological systems, including local precipitation, fiver and reservoirs. Thus, it has short transit time and its stable isotopic composition is spread around the local meteoric waterline and lines for rivers or reservoirs water. The groundwater in the deeper aquifers： middle and lower Pleistocene, and Neogene aquifers has old age up to 22.5 ka BP. Its water seems to be recharged from the areas with an altitude from 600 to 700 m higher to the Neogene deposit layer altitude. The groundwater in the SE SP （South-Eastern Southern Plain） region has a high quality. The water type is Na-Ca-Mg-HCO3 with low content of chloride and TDS （Total Dissolved Solids）. Calcite/dolomite and gypsum dissolution, organic matter decomposition and sequence of red-ox reactions proceeding through different electron acceptors sediment were controlled the chemistry of the groundwater in the study region.

A versatile cooperative template-directed coating method to synthesize hollow and yolk-shell mesoporous zirconium titanium oxide nanospheres as catalytic reactors

The design of hollow mesoporous nanostructures for cascade catalytic reactions can inject new vitality into the development of nanostructures. In this study, we report a versatile cooperative template-directed coating method for the synthesis of hollow and yolk-shell mesoporous zirconium titanium oxide nanospheres with varying compositions （ZrO2 content from 0 to 100%）, high surface areas （465 m2·g-1） and uniform mesopores. In particular, the hexadecylamine （HDA） used in the coating procedure serves as a soft template for silica@mesostructured metal oxide core-shell nanosphere formation. By a facile solvothermal treatment route with an ammonia solution and calcination in air, the silica@mesostructured zirconium titanium oxide spheres can be converted into highly uniform hollow zirconium titanium oxide spheres. By simply replacing hard template silica nanospheres with core-shell silica nanocomposites, the synthesis approach can be further used to prepare yolk-shell mesoporous structures through the coating and etching process. The approach is similar to the preparation of mesoporous silica nanocomposites from the self-assembly of the core, the soft template cetyltrimethylammonium bromide （CTAB） and a silica precursor and can be extended as a general method to coat mesoporous zirconium titanium oxide on other commonly used hard templates （e.g., mesoporous silica spheres, mesoporous organosilica ellipsoids, polymer spheres, and carbon nanospheres）. The presence of highly permeable mesoporous channels in the zirconium titanium oxide shells has been demonstrated by the reduction of 4-nitrophenol with yolk-shell Au@mesoporous zirconium titanium oxide as the catalyst. Moreover, a cascade catalytic reaction including an acid catalyzed step and a catalytic hydrogenation to afford benzimidazole derivatives can be carried out very effectively by using the accessible acidity of the yolk-shell structured mesoporous zirconium titanium oxide spheres containing a Pd core as a bifunctional catalyst, which makes the hollow zirconium titanium oxide spheres a practicable candidate for advanced catalytic systems.

Enhanced electrochemical performance in lithium ion batteries of a hollow spherical lithium-rich cathode material synthesized by a molten salt method

A high voltage layered Li1.2Ni0.16Co0.08Mn0.56O2 cathode material with a hollow spherical structure has been synthesized by molten-salt method in a NaCI flux. Characterization by X-ray diffraction and scanning electron microscopy confirmed its structure and proved that the as-prepared powder is constituted of small, homogenously sized hollow spheres （1-1.5 μm）. The material exhibited enhanced rate capability and high first cycle efficiency due to the good dispersion of secondary particles. Galvanostatic cycling at different temperatures （20, 40, and 60 ℃） and a current rate of 2 C （500 mA.g-1） showed no significant capacity fade.

Hollow and hierarchical Na_2Li_2Ti_6O_(14) microspheres with high electrochemical performance as anode material for lithium-ion battery

Relying on a solvent thermal method, spherical Na2Li2Ti6O14 was synthesized. All samples prepared by this method are hollow and hierarchical structures with the size of about 2-3 μtm, which are assembled by many primary nanoparticles （-300nm）. Particle morphology analysis shows that with the increase of temperature, the porosity increases and the hollow structure becomes more obvious. Na2Li2Ti6Ol4 obtained at 800℃ exhibits the best electro- chemical performance among all samples. Charge-discharge results show that Na2Li2Ti6O14 prepared at 800℃ can delivers a reversible capacity of 220.1, 181.7, 161.6, 144.2, 118.1 and 97.2 mA h g-1 at 50, 140, 280, 560, 1400, 2800 mA g-1. How- ever, Na2Li2Ti6O4-bulk only delivers a reversible capacity of 187, 125.3, 108.3, 88.7, 69.2 and 54.8 mA h g-1 at the same current densities. The high electrochemical performances of the as-prepared materials can be attributed to the distinctive hollow and hierarchical spheres, which could effectively reduce the diffusion distance of Li ions, increase the con- tact area between electrodes and electrolyte, and buffer the volume changes during Li ion intercalation/deintercalation processes.

Re-examining Photodetachment of H^- near a Spherical Surface using Closed-Orbit Theory

Photodeachment of H^-near a reflective spherical surface was studied by Haneef et al.[J.Phys.B:At.Mol.Opt.Phys.44(2011)195004]using a theoretical imaging method.The total cross section displays interesting oscillations.Here we re-examine the total photodetachment cross section of this system by directly applying the standard closed-orbit theory.Our result for the total cross section differs from the result obtained by Haneef et al.The difference between the two results vanishes in the limit of large radius of the reflective sphere.We argue that the theoretical imaging method developed originally for photodetachment near a Hat surface can not be directly applied to the present system.