Design of an ion-selective electrode analytical system for monitoring copper in electrochemical reactors

A flow-through cell using ion-selective electrodes has been designed for continuous on-line monitoring of electrochemical reactors. A full range of design considerations is discussed and the characteristics of the cell investigated. Optimal operating conditions are found, of which solution flow rate and constancy of temperature are particularly important. The cell was also designed to have a rapid response time and minimal dead volume so as to give continuous measurements of gradually changing metal ion concentrations. Performance has been evaluated using laboratory-simulated conditions and pilot-plant operation of the Ecocell, a rotating-cylinder electrode reactor for the electrowinning of copper from dilute solutions (10–1000 ppm).Nomenclature C ₀ initial metal ion concentration (ppm) - C _t metal ion concentration at timet (ppm) - E potential (V) - E ^{0, 1} a constant potential (V) - F Faraday constant (= 96498 C) - k apparent rate constant (s^–1) - r volumetric flow rate (cm³ s^–1) - R universal gas constant (= 8.314 J K^–1) - T absolute temperature (K) - t time (s) - V volume of gradient device (cm³) - relaxation time (s)     

In vivo characterisation of a novel bioresorbable poly(lactide-co-glycolide) tubular foam scaffold for tissue engineering applications

Polylactide-co-glycolide (PLGA) foams of tubular shape were assessed for their use as soft-tissue engineering scaffolds in vitro and in vivo. Porous membranes were fabricated by a thermally induced phase separation process of PLGA solutions in dimethylcarbonate. The parameters investigated were the PLGA concentration and the casting volume of solution. Membranes produced from 5 wt/v % polymer solutions and a 6 ml casting volume of polymer solution were selected for fabricating tubes of 3 mm diameter, 20 mm length and a nominal wall thickness of 1.5 mm. Scanning electron microscopy revealed that the structure of the tubular foams consisted of radially oriented and highly interconnected pores with a large size distribution (50-300 microm). Selected tubes were implanted subcutaneously into adult male Lewis rats. Although the lumen of the tubes collapsed within one week of implantation, histological examination of the implanted scaffolds revealed that the foam tubes were well tolerated. Cellular infiltration into the foams, consisting mainly of fibrovascular tissue, was evident after two weeks and complete within eight weeks of implantation. The polymer was still evident in the scaffolds after eight weeks of implantation. The results from this study demonstrate that the PLGA tubular foams may be useful as soft-tissue engineering scaffolds with modification holding promise for the regeneration of tissues requiring a tubular shape scaffold such as intestine.     

Development of the Eco-Cascade- cell reactor

The development of multicompartment rotating cylinder electrode reactors for the removal of metal from aqueous solutions is described. Such reactors approximate to a cascade of continuously stirred tank reactors and the results illustrate that, for electrodeposition of copper powder from acid sulphate solutions, high overall conversions (about 98%) may be realised, with low exit metal concentrations (about 1 mg dm^–3) and reasonable current efficiencies (65–87%).Nomenclature A electroactive surface area (cm²) - C _in inlet concentration of metal (mg dm^–3) - C _out outlet concentration of metal (mg dm^–3) - C _reactor reactor concentration of metal (mg dm^–3) - f _R fractional conversion - (f _R)n overall fractional conversion - F Faraday=96 500 (C mol^–1) - I _L limiting current (A) - k _l mass transfer coefficient (cms^–1) - m weight of metal (g) - M molecular weight of metal - n number of reactor elements in the cascade - N volumetric flow rate (cm³ s^–1) - z electron change - dm/dt rate of removal of metal (gs^–1) This paper was presented, in part, at the Electrochemical Reaction Engineering Symposium, Southampton University, April (1979).     

设计的复杂性呼唤系统级设计

以自然语言编写的产品规范的含糊其辞，常常会带来设计缺陷，而这种缺陷直到较晚阶段才会被发现，从而使解决方案变得更加昂贵。     

A contribution to the understanding of a.c. anodizing of aluminium

Commercial aluminium has been anodized in 10% v/v sulphuric acid using alternating current. At 20 V no significant differences in colour and thickness between specimens anodized at the neutral and live terminals were detected. At higher voltages the oxide on the neutral specimens was always more yellow and thinner than that on the live specimens. The colouration was attributed to the reduction of sulphate to sulphide during the cathodic half-cycle, no other sulphur-containing species being detected by XPS. EPMA has shown that the total sulphur distribution across the film was practically uniform and independent of the operating conditions, except in thin films, where it was greatest at the free surface. With additions of ferric sulphate to the solution the reduction to sulphide was inhibited and the differences between live and neutral specimens were avoided. The total amount of sulphur remained unchanged at approximately 5% weight and no iron was incorporated in the film.     

Deposition thickness based high-throughput nano-imprint template

International Technology Roadmap for Semiconductors 2003 projected nano-imprint lithography has the potential of high throughput, sub-20 nm resolution, and low cost [S.Y. Chou, P.R. Krauss, P.J. Renstrom, Appl. Phys. Lett. 67 (1995) 3144; Science 272 (1996) 85, J.A. Rogers, C. Mirkin, Mater. Res. Bull. 26 (2001)]. For nano-imprint lithography, a template with 1X resolution is required. The existing industrial infrastructure for supporting deep ultra violet 4X photo masks by e-beam and/or a laser beam scanning writer does not offer pitch (center-to-center distance of an array of patterned lines) less than ∼60 nm [<http://public.itrs.net/2003ITRS>]. For nano-imprint lithography to be accepted across the industry, a reproducible simple fabrication process to make a high resolution, single emboss template is essential [L. Jay Guo, J. Phys. D: Appl. Phys. 37 (2004) R123-R141]. Here we show, a general fabrication method and fabricated nano-imprint templates with sub-15 nm template line width and 10 nm pitch length through out the entire 200 mm wafer, varying the deposition thickness of multiple alternate films, using atomic layer deposition. Although multilayer nano-imprint templates and their exciting use have been demonstrated, [W.J. Dauksher et al., J. Vac. Sci. Technol. B 22 (2004) 3306, B. Heidari, et al., The 49th international conference on electron, ion and photon beam technology and nanofabrication, Orlando, Florida, 2005, William M. Tong, et al., Proc. SPIE 5751 (2005) 46-55, N.A. Melosh, A. Boukai, F. Diana, B. Gerardot, A. Badolato, P.M. Petroff, J.R. Heath, Science 300 (2003) 112] such a small pitch was not shown and either complex lattice mismatch-based epitaxially grown films or unconventional etch chemistry was used. The bare necessity was a simple and economical fabrication process for a high throughput nano-imprint template. In that context, we have developed a template fabrication process using classical micro-fabrication techniques. Successful use of these techniques made the template fabrication process simple, economical, and expedient. Also a novel technique to provide flexible and accurate alignment for nanowire patterning has been described. In this technique, nanowire patterning is accomplished on the entire wafer with a single impression. Industry level batch-fabrication of our scheme illustrates its reproducibility and manufacturability. We anticipate, this simple, economical and time saving technique will help researchers and developers to perform their experiment on nano-scale feature patterned substrates easily and conveniently.