Tl-based high-Tc superconducting films prepared by aerosol deposition

The deposition of aqueous aerosols of nitrates led to precursor films with a thickness of 3–5 μm. The Ba–Ca–Cu–O and Pb–Sr–Ba–Ca–Cu–O as-deposited layers were calcined at 850–870°C. Thallination of Ba–Ca–Cu–O precursors at relatively high Tl₂O partial pressure resulted in Tl-2212 films with preferred c-axis orientation. Partial substitution of Pb for Tl and of Sr for Ba yielded randomly oriented Tl-1212 films. Deposition of Ba(II)-, Ca(II)- and Cu(II)-bis(2,4-pentanedionates) on polycrystalline silver tapes produced — after subsequent thallination — textured Tl-2223 films with a thickness of about 1 μm. Some aspects of the chemical reactions proceeding during the aerosol deposition and in the thallination step are discussed on the basis of thermogravimetric measurements.     

Magnetic field dependence of the critical current density for the bismuth-based bulk high-Tc superconductors

Three types of bismuth-based bulk samples were prepared through uniaxial pressing at room temperature, hot isostatic pressing (HIP) and drawing and rolling. Transport current properties were characterized in a steady field up to 1.12 T at 77 K (T/T _c=0.75). The Josephson weak-link decoupling fields have been found to be 5 mT for the cold-pressed pellet and 30 mT for the HIPed pellet and the rolled tape. At the decoupling field the transport critical current density,J _c, drops 80% from 124 (OT) to 29 A cm^–2 (5 mT) for the cold-pressed pellet, 80% from 582 (OT) to 126 A cm^–2 (30 mT) for the HIPed sample and 50% from6500 (0 T) to 2850 A cm^–2 (30 mT) for the rolled tape. In the flux flow regime, whereB is perpendicular to thec-axis a modified Kim's modelJ _c=(/B ₀)/[(1+B/B ₀)] ⁿ can be used to describe the field dependence of the critical current density, J_c, in the field range 0.2–1.12 T. The effective upper critical fields were estimated to be 0.98, 1.54 and 1.94 T for the three types of samples, respectively. An adjustable range ofB _c2 for bismuth-based bulk highT _c superconductors is given. Flux shear may operate in these materials. The prediction of this pinning mechanism is yielded from fitting the equation qualitatively. WhenB is parallel to thec-axis, the absence of strongly intragranular flux-pinning is emphasized by the poor flux flow regime for the rolled tape sample.     

Preparation of free-suspended polyelectrolyte multilayer films using an alginate scaffold and their ion permeability

Free-suspended polyelectrolyte multilayer (PEM) films were prepared over an aperture (diameter, 1 or 3 mm) in a glass plate to study ion permeation across the PEM films. PEM films were successfully constructed by layer-by-layer deposition of poly(allylamine hydrochloride) and poly(styrene sulfonate) on the surface of glass plate whose aperture had been filled with an alginate gel, followed by dissolution of the alginate gel in an ethylenediaminetetraacetic acid solution. PEM films thus prepared showed selective permeability for inorganic salts such as NaCl, KCl, CaCl₂, Na₂SO₄, K₃[Fe(CN)₆], and K₄[Fe(CN)₆]. The results were rationalized based on the size and charge of the ions and the thickness and surface charges of films.     

Insulin-loaded nanoparticles are prepared by alginate ionotropic pre-gelation followed by chitosan polyelectrolyte complexation

Alginate nanoparticles were prepared from dilute alginate sol by inducing a pre-gel with calcium counter ions, followed by polyelectrolyte complex coating with chitosan. Particles in the nanometer size range were obtained with 0.05% alginate and 0.9 mM Ca2+. The mean particle size was influenced by time and stirring speed of nanoparticle preparation, by alginate guluronic acid content and chitosan molecular weight and by the initial alginate:chitosan mass ratio. The association efficiency of insulin into alginate nanoparticles, as well as loading capacity were mainly influenced by the alginate:chitosan mass ratio. Under optimized size conditions, the association efficiency and loading capacities were as high as 92% and 14.3%, respectively. Approximately 50% of the protein was partially retained by the nanoparticles in gastric pH environment up to 24 hours while a more extensive release close to 75% was observed under intestinal pH conditions. Mild formulation conditions, optimum particle size range obtained, high insulin entrapment efficiency, and resistance to gastrointestinal release seem to be synergic and promising factors toward development of an oral insulin delivery form.     

Preparation of cross-linked sodium alginate microparticles using glutaraldehyde in methanol

Polymeric sodium alginate microparticles were prepared by precipitating sodium alginate in methanol, followed by cross-linking with glutaraldehyde. The extent of cross-linking was controlled by the time of exposure to glutaraldehyde. The topology of microparticles was characterized by scanning electron microscopy (SEM), which indicated smooth surfaces. The equilibrium swelling experiments were carried out in water to observe the effect of cross-linking and drug loading for better utility of microparticles. It was found that swelling decreased, but drug loading increased, with an increase in cross-linking of the matrix.     

海藻酸钠／累托石插层复合高吸水性树脂制备及性能

以海藻酸钠(SA)与钠化累托石(Na REC)为原料通过水溶液法制备插层纳米复合材料(SA/Na REC),再以此作为第二组分加入到部分中和的丙烯酸中进行接枝共聚制备SA/Na REC-g-PAA复合高吸水性树脂.研究了SA/Na REC复合材料用量、引发剂用量、交联剂用量、中和度等影响高吸水性树脂吸水性能的主要因素.结果表明,产品吸水率达到657g/g,吸盐水率达到118g/g,与同工艺条件的SA-g-PAA高吸水性树脂相比,吸水率提高136g/g、吸盐水率提高14g/g、凝胶模量提高0.5×10-5Pa、干树脂在功率为320W紫外灯照射30d的失重率减少4.2%、水凝胶在70℃,8h后保水率提高4.6%,且吸水速率快,避免了在吸水过程中产生面团现象.XRD表明Na REC在接枝共聚物基体中部分被剥离,形成插层型复合高吸水性树脂,SEM显示SA/Na REC-g-PAA复合高吸水性树脂具有多孔的层状结构.     

膜技术处理褐藻酸钠废水

介绍了采用预处理-超滤-纳滤工艺处理褐藻酸钠生产过程中排放的含钙废水的试验研究结果．结果表明，该废水经处理后，产水可作为生产工艺用水回用，回用率≥75％，浓缩液和废渣可制取海藻生物肥，实现清洁生产，环境效益和经济效益显著．     

Fabrication of single-crystalline gallium nitride nanowires by using alginate as template

Hexagonal gallium nitride nanowires were synthesized successfully by solvothermal method with alginate as template. The microstructure, morphologies and compositions of the as-prepared product were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM), and energy dispersive X-ray (EDX). Results suggested that the rod-like nanowires were hexagonal single-crystalline GaN growing along [001] direction. The photoluminescence spectra (PL) of the GaN revealed that the as-synthesized sample possesses excellent optical properties.     

以柠檬酸钠为分散剂一步法合成Cu-水导热纳米流体

以柠檬酸钠为分散剂,KBH4为还原剂,CuSO4·5H2O为氧化剂,采用一步法直接合成了Cu-水导热纳米流体。其最佳合成工艺条件为:n(CuSO4·5H2O)∶n(KBH4)=2.5∶1,柠檬酸钠的用量为0.07mol/L,温度为40℃,反应时间为100 min。TEM表征表明该导热纳米流体中Cu纳米粒子分散较均匀;经激光光散射仪粒度分析得其分散粒子平均尺寸为1.1nm;在25℃时测得该导热纳米流体的导热系数为0.7812 W/(m·K),比纯水的导热系数提高30%。     

Synthesis of highly ordered and hydrothermally stable mesoporous materials using sodium silicate as a precursor

Highly ordered mesoporous silica and aluminosilicate materials with extremely high hydrothermal stability have been synthesized successfully at a high hydrothermal treatment temperature of 200 °C by using inexpensive sodium silicate and sodium aluminate as the silica source and alumina source, respectively. The resultant mesoporous materials possess a hexagonal mesostructure and extraordinary stability towards the steam treatment at 800 °C for 2 h. In addition, the direct incorporation of Al into the mesoporous framework can further enhance the hydrothermal stability of ordered mesoporous materials. Our contribution provides a commercially important approach to synthesize ordered mesoporous materials with highly hydrothermal stability, which may find potential applications for the catalytic cracking in the petroleum industry.     

Feasibility of xanthan gum–sodium alginate as a transdermal drug delivery system for domperidone

The present investigation comprises the formulation and in vitro evaluation of domperidone loaded transdermal drug delivery system (TDDS) for controlled release. The polymer membranes were prepared using xanthan gum (XG) and sodium alginate (SA) by varying the blends compositions viz., 10:0, 8:2, 6:4, 5:5, 4:6, 2:8, and 0:10 (XG/SA, wt/wt, %). The drug loaded membranes were evaluated for thickness, content uniformity, tensile behaviours, and in vitro drug release studies. Domperidone was found to be compatible with the prepared formulation as revealed by Fourier transform infrared (FTIR) spectroscopy studies. In vitro release studies were carried out in open glass diffusion cell for a period of 8 h and it showed controlled release of drug from the XG/SA matrix. The present study concludes that, the prepared transdermal films can be used to achieve controlled release of drug and improved bioavailability.     

Layer-by-layer deposition of polyelectrolyte nanolayers on natural fibres: cotton

The layer-by-layer (LbL) deposition of poly(sodium 4-styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) over cotton fibres is reported. Cotton fibres offer unique challenges to the deposition of nanolayers because of their unique cross section as well as the chemical heterogeneity of their surface. Cationic cotton substrates were produced by using 2,3-epoxypropyltrimethylammonium chloride. Attenuated total reflectance FTIR, x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) were used to validate the presence of the nanolayers as well as to corroborate their self-organized structure. TEM images indicated conformal and uniform coating of the cotton fibres. XPS spectral data were found to be in quantitative agreement with previous published work that studied the LbL deposition of PSS and PAH over synthetic substrates.     

Synthesis of sodium magnesium iron sulfate rod-likes as NASICON using the precipitation method

Sodium magnesium iron sulfate rod-likes were synthesized using the tailing by the precipitation method. The density of the tailing sample was determined as 3.45 g/cm³ and 85% of the particle sizes are < 300 μm. In the course of synthesis, the tailing dissolved in the sulfuric acid. The solution was participated using sodium hydroxide. The precipitate was calcinated at 500 °C in the furnace without special atmosphere. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to characterize the prepared product. XRD results showed that sodium magnesium iron sulfate is the desired material. Also, the sample contains a small amount of sodium sulfate. The SEM image proved that the morphology of the sample is rod-like. It was observed that the diameter of the rod-likes was about 100-250 nm.     

Synthesis of nano-sized ceria powders by two-emulsion method using sodium hydroxide

In the present study, nano-sized ceria powders were prepared by the two-emulsion method in the presence of aqueous sodium hydroxide. The effect of the ceria precursor concentration and the addition of an aqueous sodium hydroxide on the crystallite size, the size distribution and the morphology of the synthesized powders were investigated. The precipitates were obtained by mixing two water-in-oil emulsions with kerosene containing cerium nitrate aqueous solution and sodium hydroxide aqueous solution. The synthesized ceria powders were characterized by XRD and TEM. The synthesized ceria powders had nearly spherical shape and a uniform crystallite size in a range of 10 to 20 nm depending on the concentration of precursor solution and an addition amount of mineralizer.     

Regenerating the strength of thermally recycled glass fibres using hot sodium hydroxide

Results are presented from the ReCoVeR project on the regeneration of the strength of thermally conditioned glass fibres. Thermal recycling of end-of-life glass fibre reinforced composites or composite manufacturing waste delivers fibres with virtually no residual strength or value. Composites produced from such fibres also have extremely poor mechanical performance. Data is presented showing that a short hot sodium hydroxide solution treatment of such recycled fibres can more than triple their strength and restore their ability to act as an effective reinforcement in second life composite materials. The implications of these results for real materials reuse of recycled glass fibres as replacement for pristine reinforcement fibres are discussed.