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1 – 10 of 118
Article
Publication date: 1 April 1995

M. Nasta and H.C. Peebles

A good solder flux must simultaneously perform a number of important functions. It must promote thermal transfer to the area of the solder joint, enhance wetting of the…

Abstract

A good solder flux must simultaneously perform a number of important functions. It must promote thermal transfer to the area of the solder joint, enhance wetting of the solder on the base metal, and prevent oxidation of the metal surfaces at soldering temperatures. However, its primary task is to remove the tarnish layer from the metal joint that is about to be soldered. Despite the fact that the process of soldering electronic devices is a part of a multi‐billion dollar industry, the actual chemical reactions that occur during this cleaning process are not well documented. In the case of organic acid or water‐soluble fluxes, the flux reactions can be modelled by considering the interactions at the metal/metal oxide/electrolyte solution interface. Although such modelling systems have not frequently been applied to the behaviour of solder and fluxes, they are common for a number of other closely related chemical systems which are of practical interest, e.g., passivation layers on metals, electrochemical cells and metal oxide semiconductors. There are two types of reactions that can occur at the oxide/solution interface: acid‐base reactions and oxidation‐reduction reactions. The factors which affect the reaction rates and mechanisms are such variables as the structure of the metal oxide, temperature, pH, concentration of the electrolyte, and the chemical nature of the solute and solvent. By combining information about flux behaviour with available models of surface reactions, it should be possible to develop the theory of the flux reactions and to gain a better understanding of the factors which control the process.

Details

Circuit World, vol. 21 no. 4
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 April 1981

James C. Swartzell

High density PCB production requires ever closer investigation of the factors which influence the ability to fabricate efficient circuitry. One of these, etching, is…

Abstract

High density PCB production requires ever closer investigation of the factors which influence the ability to fabricate efficient circuitry. One of these, etching, is examined, revealing that even that process alone is subject to the effect of physical, chemical and hydraulic parameters. Physical factors include raw materials, circuit geometry and process equipment, etcher spray systems being discussed at length. The implications of the chemical parameters are specifically linked with etchant formulation. Oxidation reduction potential and etchant density effects are also dealt with before the final section on hydraulic factors, where the importance of the design of the hydraulics system is underlined.

Details

Circuit World, vol. 8 no. 1
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 February 2004

P. Kalenda

This paper presents a method for the determination of the kinetic parameters for the oxidation‐reduction hardening reactions of unsaturated polyesters with styrene. The…

Abstract

This paper presents a method for the determination of the kinetic parameters for the oxidation‐reduction hardening reactions of unsaturated polyesters with styrene. The method was based on the measurement of the change in the specific internal electric resistance during the hardening. This paper discusses the accelerating effects of ferrocene and some of its derivatives (acetylferrocene, benzoylferrocene, 1,1′‐diethylferrocene) on the hardening of unsaturated polyesters.

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Pigment & Resin Technology, vol. 33 no. 1
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 1 June 2004

Cristiano Giacomelli and Almir Spinelli

The behaviour of iron electrodes immersed in pH 8.9‐11.0 Na2HPO4 solutions was studied by potentiodynamic measurements (cyclic voltammetry) and scanning electron…

Abstract

The behaviour of iron electrodes immersed in pH 8.9‐11.0 Na2HPO4 solutions was studied by potentiodynamic measurements (cyclic voltammetry) and scanning electron microscopy (SEM). The influence of proton and phosphate content, scan rate, anodic switching potential and other devised potential/time perturbation regimes were evaluated in order to obtain an understanding of the reactions involved during the passivation process. The oxidation‐reduction peaks were analysed using a thermodynamic approach. It was possible to reveal the most important reactions coming about on the electrode surface, which comprise, initially, the formation of Fe3(PO4)2 and Fe(OH)2 at ca. −0.8 V/SCE. Subsequently, these ferrous species are further oxidized to γ‐FeOOH at ca. −0.36 V/SCE, the latter being transformed into Fe2O3 in the passive region. Depending on the pH value (11.0) and scan rate (slow), Fe3O4 is clearly present as an intermediate oxide structure between the ferrous and ferric species mentioned earlier. In addition, scan rate was discovered to play a remarkable influence on the surface morphology observed during the SEM examinations.

Details

Anti-Corrosion Methods and Materials, vol. 51 no. 3
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 28 November 2018

Qin Xiaoxuan, Hui’e Liang, Xuzhong Su and Xinjin Liu

As a natural fiber, yakwool has attracted much attention in textile processing due to its excellent properties and wearabilities. However, the main colors of yakwool are…

Abstract

Purpose

As a natural fiber, yakwool has attracted much attention in textile processing due to its excellent properties and wearabilities. However, the main colors of yakwool are black and brown. Therefore, for extending the application scopes of the fiber, the decolorization of the yakwool fiber is usually needed, especially for the black fiber. The paper aims to discuss this issue.

Design/methodology/approach

In the paper, the properties of the yakwool fiber were tested first, especially the melanin granules in the fiber. Then, the decolorization of the yakwool fiber was studied using the oxidation–reduction decolorization method, and corresponding optimal process of the decolorization was given. Then, the properties of the decolorized yakwool fiber were tested and compared with those of the original fiber.

Findings

It is shown that, after decolorization, the physical and mechanical properties of the fiber were deteriorated, especially in terms of the strength and elongation. Therefore, the fiber became shorter and thinner, and the scales were damaged. When compared with the yarn spun from the original yakwool fiber, it was observed that the properties of the yarn spun from the decolorized yakwool fiber deteriorated because of the deterioration in the properties of the original fiber.

Originality/value

In the paper, for extending the application scopes of the yakwool fiber, the decolorization of the yakwool fiber was studied.

Details

International Journal of Clothing Science and Technology, vol. 31 no. 1
Type: Research Article
ISSN: 0955-6222

Keywords

Book part
Publication date: 29 January 2021

Robin Goldberg and Vicki Chandler

There is strong agreement among educators at universities and colleges worldwide about the importance of assessing and measuring student learning. Yet, putting those best…

Abstract

There is strong agreement among educators at universities and colleges worldwide about the importance of assessing and measuring student learning. Yet, putting those best intentions into practice can be daunting within existing institutions. At Minerva, we had the luxury of starting a new college from scratch. We designed the institution to deliver specific student outcomes, and built all the operating practices and systems needed to support faculty and students in this pursuit. In this chapter, we share how Minerva defined what we teach, how we teach, and how our practices enable us to measure whether our students are indeed achieving the outcomes we had intended for them. We hope you might be inspired by learning about our approach, as we do believe that much of what we have put into place can be incorporated by other institutions to help their students achieve their learning outcomes.

Details

Learning Gain in Higher Education
Type: Book
ISBN: 978-1-83867-280-5

Keywords

Article
Publication date: 1 October 2003

Xu Chunchun and Wang Julin

This paper describes a study on the corrosion behaviour of archaeological bronze in simulated groundwater by means of a simulated occluded cell. The study revealed…

Abstract

This paper describes a study on the corrosion behaviour of archaeological bronze in simulated groundwater by means of a simulated occluded cell. The study revealed migration, enrichment and deposition patterns of ions in the environment and the cations produced by anodic dissolution during localised corrosion of bronze. The cycle voltametry technique was utilised for the first time on the study of electrochemical behaviour of the bronze/simulated occluded solution interface. The potential and current peaks of oxidation‐reduction at the cathode and anode in the occluded solutions at various time intervals facilitated a study of the corrosion products formation processes and their formation speeds.

Details

Anti-Corrosion Methods and Materials, vol. 50 no. 5
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 24 October 2021

Mulayam Singh Gaur, Rajni Yadav, Mamta Kushwah and Anna Nikolaevna Berlina

This information will be useful in the selection of materials and technology for the detection and removal of mercury ions at a low cost and with high sensitivity and…

85

Abstract

Purpose

This information will be useful in the selection of materials and technology for the detection and removal of mercury ions at a low cost and with high sensitivity and selectivity. The purpose of this study is to provide the useful information for selection of materials and technology to detect and remove the mercury ions from water with high sensitivity and selectivity. The purpose of this study is to provide the useful information for selection of materials and technology to detect and remove the mercury ions from water with high sensitivity and selectivity.

Design/methodology/approach

Different nano- and bio-materials allowed for the development of a variety of biosensors – colorimetric, chemiluminescent, electrochemical, whole-cell and aptasensors – are described. The materials used for their development also make it possible to use them in removing heavy metals, which are toxic contaminants, from environmental water samples.

Findings

This review focuses on different technologies, tools and materials for mercury (heavy metals) detection and remediation to environmental samples.

Originality/value

This review gives up-to-date and systemic information on modern nanotechnology methods for heavy metal detection. Different recognition molecules and nanomaterials have been discussed for remediation to water samples. The present review may provide valuable information to researchers regarding novel mercury ions detection sensors and encourage them for further research/development.

Details

Sensor Review, vol. 41 no. 6
Type: Research Article
ISSN: 0260-2288

Keywords

Article
Publication date: 1 March 1985

H.O. Ali and I.R.A. Christie

The literature on electroless gold deposition processes is reviewed both with respect to bath formulation and the kinetics of the electrochemical reduction and oxidation…

Abstract

The literature on electroless gold deposition processes is reviewed both with respect to bath formulation and the kinetics of the electrochemical reduction and oxidation reactions involved. Some modified formulations are discussed in more detail and components processed by the use of electroless gold deposition are illustrated.

Details

Circuit World, vol. 11 no. 4
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 March 1999

S.M.E. Meehan, T.R. Weaver and C.R. Lawrence

Cyanide is extremely toxic to both human and aquatic life and exists as a contaminant in soils and groundwater at decommissioned gasworks sites due to past industrial…

Abstract

Cyanide is extremely toxic to both human and aquatic life and exists as a contaminant in soils and groundwater at decommissioned gasworks sites due to past industrial practices. This included the processing and disposal of gas purification wastes which contained cyanide. The biodegradability of cyanide at gasworks sites in south‐eastern Australia is investigated to determine the viability of in situ bioremediation. Two study sites show cyanide concentrations in groundwater of up to 5,300mg/L CN (total) in the vicinty of these sites. Laboratory experiments using column microcosms indicate both aerobic and anaerobic biodegradation of cyanide in water. Rates of degradation are typically first order with degradation microbiologically driven and are not simple oxidation‐reduction reactions. The rate of degradation is variable, depending on the existence of microbes, concentration and temperature. Even though both sites have cyanide contamination, only one requires remediation. In situ bioremediation is possible at this site thus providing an acceptable outcome to both site owner and the environment.

Details

Environmental Management and Health, vol. 10 no. 1
Type: Research Article
ISSN: 0956-6163

Keywords

1 – 10 of 118