Dissolution of Haematite in Citric Acid-EDTA-Ascorbic Acid Mixtures

This study is related to the development of a suitable mixture of citric acid, EDTA and ascorbic acid (CEA) for dissolving the haematite deposited on the structural surfaces of cooling water circuits in BWRs. The dissolution experiments were performed with synthetically prepared haematite. The dependence of the dissolution rates on each of the constituents of the mixture has been evaluated using a ‘grain model’. It was found to be Langmuirianin the case of citric acid, linear in the case of EDTA and independent of ascorbic acid concentration. The ratio of molar concentration of the ligand to the total iron was varied from 0.5—2.5. Activation energy of the dissolution in a CEA mixture having stoichiometrically excess EDTA has been determined by performing experiments upto 353 K. The highest dissolution was obtained in 11:44:4 mol·m^?3 and 2:55:4 mol·m^?3 CEA mixtures.     

Fatigue Life and Crack Growth Mechanisms of the Type 316LN Austenitic Stainless Steel in 310°C Deoxygenated Water

The low cycle fatigue tests of the type 316LN stainless steel were conducted to investigate the cracking mechanisms in high-temperature water. The fatigue lives of the specimens tested in 310°C deoxygenated water were considerably shorter than those tested in air. For the specimens tested in 310°C deoxygenated water, the evidences for the metal dissolution such as the stream downed feature, the blunt crack shape, and the wider crack opening were observed but rather weakly. In the same specimens, the evidences for the hydrogen-induced cracking such as the coalescence of microvoids and the decrease of the dislocation spacing at the crack tip were observed rather clearly. Therefore, it is thought that the hydrogen-induced cracking is mainly responsible for the reduction in the fatigue life of the type 316LN stainless steel in 310°C deoxygenated water while the effect of metal dissolution is less significant. The hydrogen-induced cracking is more pronounced in the slower strain rates. This behavior is in accordance with the larger reduction in the fatigue life at the slower strain rates. Furthermore, the fatigue life and the dislocation spacing show the minimum value in the strain rate range from 0.008 to 0.04%/s, which indicates the existence of the critical strain rate.     

南梁矿业公司选煤厂煤泥卸料系统的改造实践

针对煤泥卸料系统堆煤能力有限、场地利用率不高、环境污染严重等问题,通过计算分析与研究,对卸料系统实施了改造,将卸料口直接落地改造成了方向可调的溜槽式卸料,最终实现了溜槽旋转卸料、分三个方向的270°储煤,既增加了煤泥储量,又充分利用了场地,达到了减少清理次数、保护环境、增加场地利用率的目的。     

固体有机物合成的低温共熔溶剂的研究及其对纤维素的溶解

对固体有机物尿素、己内酰胺、乙酰胺以不同配比制备的尿素/己内酰胺、尿素/乙酰胺和乙酰胺/己内酰胺3种低温共熔溶剂进行了研究,并考察了其物理化学性质(熔点、电导率等).结果表明,随着物质的量比的不同,低共熔溶剂的熔点不同,最佳物质的量比分别为1∶3、1∶2和1∶1,在最佳物质的量比下的熔点分别为30℃、48℃和18℃.低温共熔溶剂的电导率在10-4～10-5 S/m数量级,随温度的升高,电导率增加,电导率与温度符合Arrhenius方程.IR测试结果显示,固体有机物各自分子内的氢键消失,形成了新的氢键.初步探讨了纤维素在3种体系中的溶解性能,结果显示,3种溶剂对纤维素有一定的溶解能力.通过分析得出,该类共熔体溶剂为酰胺类溶剂,主要通过其羰基上的氧原子和氨基上的氮原子与纤维素上的羟基形成氢键.IR和XRD测试结果表明,纤维素和再生纤维素有相似的结构,但纤维素的晶型从Ⅰ型转变为Ⅱ型.     

Study of Electroless Copper Deposition on Fe Powder

The electrolytic deposition of an electropositive metal is often accompanied by electroless deposition. However, this process is very difficult to control. For that reason, our study has been aimed at the conditions of the electroless deposition of copper coating onto the iron powder particles from sulphate electrolyte. The process consists of two partial reactions; solid iron substrate dissolves into the solution, thus providing the electrons necessary for reduction of copper. The course of the electroless process depends to a large extent on the composition and pH of the electrolyte as well as on the size and concentration of the iron powder particles in the electrolyte. In order to suppress the spontaneous electroless deposition of copper, sodium citrate as complexing agent was used. The following parameters were determined to characterize the reaction course: the heterogeneous rate constant of Fe powder dissolution and degree of Fe conversion as well as thickness of the Cu layer on the Fe powder, both of the latter evaluated upon attaining the stationary state. The main influence exhibited on the reaction course is the efficient surface area available for electroless deposition.     

Co-crystallization for enhanced dissolution rate of bicalutamide: preparation and evaluation of rapidly disintegrating tablets

Objectives: Enhance the dissolution rate of bicalutamide via co-crystallization with sucralose (sweetener), with the aim to develop rapidly disintegrating tablets with subsequent prompt dissolution.

Significance: Bicalutamide is antiandrogenic agent for the treatment of prostate cancer but has low and variable oral bioavailability, mainly attributed to poor dissolution. Co-crystallization with benign excipients is promising for dissolution enhancement with the additive serving dual functions. The benefit will become greater if dissolution enhancement is associated with the development of orodispersible tablets which is suitable for elderly patients who are the most vulnerable for prostate cancer.

Methods: Bicalutamide was dissolved in acetone in the presence of increasing molar ratios of sucralose. The solvent was evaporated while mixing to deposit crystals that were subjected to wet co-grinding until drying. The developed solids were characterized using Fourier transform infrared spectroscopy, differential thermal analysis and X-ray diffraction in addition to monitoring bicalutamide dissolution.

Results: Instrumental analysis provided evidences for co-crystallization which was initiated at 1:1 molar ratio of bicalutamide to sucralose with complete co-crystallization at 1:4 molar ratio. The co-crystals provided faster bicalutamide dissolution compared with the unprocessed drug and that recrystalized from acetone in the absence of sucralose. The formulation containing bicalutamide with sucralose at 1:4 molar ratio was selected for tablet formulation into which superdisintegrants were included. The developed tablets exhibited flash disintegration with subsequent fast dissolution of bicalutamide.

Conclusions: The study introduced co-crystallization of bicalutamide with sucralose as an efficient tool to enhance the dissolution rate and to develop rapidly dissolving tablets for intraoral administration.     

Preparation,characterization, stability and in vitro-in vivo evaluation of pellet-layered Simvastatin nanosuspensions

The objective of the present study was to develop stable pellets-layered Simvastatin (SIM) nanosuspensions with improved dissolution and bioavailability. The nanosuspensions were prepared with 7% HPMC, antioxidant 0.03% butylated hydroxyanisole and 0.2% citric acid (m/v) by low temperature grinding. After that, SDS with SIM was in a ratio of 1:5 (m/m), was evenly dispersed in the nanosuspensions. Then, they were layered on the surface of sugar pellets. The mean particle size of the SIM nanosuspensions was 0.74 µm, and 80.6% of the particles was below 1 µm in size. The pellets could re-disperse into nanoparticle status in the dissolution medium. In 900?mL pH 7.0 phosphate solutions, the dissolution of the layered pellets was better than that of commercial tablets. Also, nearly 100% of the drug dissolved from the pellets within 5?min under sink conditions. During the stability studies, SIM pellets exhibited good physical and chemical stability. The relative bioavailability of SIM and Simvastatin β-hydroxy acid (SIMA) for nanosuspensions layered pellets compared with commercial tablets was 117% and 173%, respectively. The bioavailability of SIMA was improved significantly (p < 0.05), confirming the improvement of bioavailability. Thus, the present study demonstrates that the pellet-layered SIM nanosuspensions improved both the dissolution and bioavailability of SIM.     

A Simple Method to Synthesize Cadmium Hydroxide Nanobelts

Cd(OH)₂ nanobelts have been synthesized in high yield by a convenient polyol method for the first time. XRD, XPS, FESEM, and TEM were used to characterize the product, which revealed that the product consisted of belt-like crystals about 40 nm in thickness and length up to several hundreds of micrometers. Studies found that the viscosity of the solvent has important influence on the morphology of the final products. The optical absorption spectrum indicates that the Cd(OH)₂ nanobelts have a direct band gap of 4.45 eV.     

The effect of the hydrothermal treatment with aqueous NaOH solution on the photocatalytic and photoelectrochemical properties of visible light-responsive TiO2 thin films

The effect of the hydrothermal treatment with aqueous NaOH solution on the photoelectrochemical and photocatalytic properties of visible light-responsive TiO₂ thin films prepared on Ti foil substrate (Vis-TiO₂/Ti) by a radio-frequency magnetron sputtering (RF-MS) deposition method has been investigated. The hydrothermally treated Vis-TiO₂/Ti electrodes exhibited a significant increase in their photocurrent under UV and visible light irradiation as compared to untreated Vis-TiO₂/Ti electrode. SEM investigations revealed that the surface morphology of Vis-TiO₂/Ti are drastically changed from the assembly of the TiO₂ crystallites to the stacking of nanowires with diameters of 30–50 nm with increasing hydrothermal treatment time (3–24 h), accompanying the increase in their surface area. The separate evolution of H₂ and O₂ from water under solar light irradiation was successfully achieved using the Vis-TiO₂/Ti/Pt which is hydrothermally treated for 5 h, while the H₂ evolution ratio was 15 μmol h⁻¹ in the early initial stage, corresponding to a solar energy conversion efficiency of 0.23%.     

Char and Coke Formation as Unwanted Side Reaction of the Hydrothermal Biomass Gasification

The hydrothermal biomass gasification is a promising technology to produce hydrogen and/or methane from wet biomass with a water content of ≥ 80 % (g/g). In the process, the coke formation usually is very low, but already low amounts may cause problems like, e.g., fouling in the heat exchanger. To learn more about the product formation, the results of the hydrothermal treatment (at 400, 500, 600 °C and 1 h) of different biomass feedstocks (artichoke stalk, pinecone, sawdust, and cellulose as model biomass) in a microreactor are compared. The gas composition and the total organic carbon content of the aqueous phase were determined after reaction. The gas formation rises with increasing temperature. The formation of carbon deposits and their characterization has been investigated by scanning electron microscopy (SEM). The variation of the solid morphology during the hydrothermal conversion is discussed based on chemical pathways occurring during hydrothermal biomass degradation.