Showing papers by "Timothy J. Mason published in 2008"

Sonoelectrochemical (20 kHz) production of Co65Fe35 alloy nanoparticles from Aotani solutions

Abstract: This paper describes the production of alloy nanoparticles of Co:Fe ratio 65:35 from Aotani solutions in the presence of high power ultrasound (20 kHz). The production of this new type of alloy nanoparticles was performed potentiostatically and galvanostatically at (298 ± 1) K using a newly designed experimental set-up i.e. a ‘sonoelectrode’ producing short applied current pulses triggered and followed immediately by ultrasonic pulses. It was shown that cathode efficiencies decreased with increasing current densities and high nanoparticle yields were obtained at low current densities. Morphological and structural studies of the produced nanoparticles were performed by TEM, SEM, XRD, and SAED, and showed that the strongly aggregated Co65Fe35 alloy nanoparticles were predominantly formed, with prevalent body-centered cubic bcc crystalline structure; no redissolution of the nanoaggregates was observed and no separate Fe and Co metallic nanoparticles were produced sonoelectrochemically. The experimental value of the lattice parameter for bcc Co–Fe alloy was 2.85 A and was in excellent agreement with literature values.

The sonochemical surface modification of materials for electronic manufacturing. The effect of ultrasonic source to sample distance

Abstract: Purpose – To build on the results detailed in the previous paper where it was shown that sonochemical surface modification could be achieved in water. This paper aims to look at one of the factors affecting sonochemical surface modification, namely the ultrasonic source to sample distance.Design/methodology/approach – Ultrasound was applied through deionized water for the surface modification of three materials: a high Tg PCB laminate (Isola 370HR), a polyphenylene ether – polystyrene polymer (Noryl HM4025) and an acrylonitrile‐butadiene‐styrene/polycarbonate (Cycolac S705). The efficacy of the treatment was determined by weight loss, scanning electron microscopy, contact angle, roughness and tape testing after electroless copper plating.Findings – The study confirmed, and extended the previous findings, that a range of substrates could be sonochemically surface modified in water, even though in this work the ultrasonic horn had a larger tip size and produced a different ultrasonic intensity. Although the...

Nanoparticle synthesis and formation of composite solder for harsh environments

Abstract: The demand for electronics capable of operating at high ambient temperatures above 150degC is increasing in the oil/gas drilling and automotive industries in particular. These demands have accelerated the progress of materials development and processing technology. Nanoparticle enhanced solders have been reported to have superior creep and reliability properties compared to simple alloyed materials. The nanoparticles, typically added at 1-2 vol% concentrations into the solder serve to harden the solder, stabilize the microstructure and improve reliability in high temperature environments. The nanoparticles may be added to the solder before production of solder particles, or added as a separate ingredient of the solder paste. This paper explores the latter approach.

The evaluation of sonochemical techniques for sustainable surface modification in electronic manufacturing

Abstract: Purpose – This paper sets out to give an introduction to sonochemistry and the effects brought about by the application of ultrasound that might be useful in surface modification; and to show the feasibility of sonochemical surface modification in water on a range of materials employed in electronic manufacturing.Design/methodology/approach – Ultrasound was applied through DI water for the surface modification of four materials: a ceramic, a polyphenylene ester (polystyrene polymer (Noryl HM4025)), an acrylonitrile‐butadiene‐styrene/polycarbonate (ABS/PC‐Cycolac S705), and an FR4 laminate (Isola Duraver 104). The efficacy of the treatment was determined by weight loss, scanning electronic microscopy, contact angle and roughness.Findings – Ceramic and Noryl materials can be surface modified sonochemically in DI water. Weight loss results suggested that, this was also the case for the Duraver laminate but the ABS/PC substrate was least affected by treatment in an ultrasonic field under these benign processi...

Sonochemistry — a sound approach to surface modification

Abstract: The surface modification of dielectric materials is required throughout the electronics industry. Traditional chemical methods however tend to be characterised by the use of hazardous substances, high temperature operation and long process times. Previous work has shown that significant surface modification of substrates used in electronic manufacturing can be achieved by applying ultrasound of an appropriate frequency through liquids as benign as water. In this work a number of factors which can affect the phenomenon of acoustic cavitation are investigated along with their subsequent impact on surface modification. It was found that all the process variations considered caused a greater weight loss compared to the standard sonochemical technique. However, adding a small amount of a surfactant containing product also increased roughness, improved wettability and produced samples with a dramatic change in morphology.

Effect of ultrasound treatment on particle size distribution and protein composition of soy protein isolate & concentrate suspensions

Abstract: Humans can hear the sound which has the frequencies in the range of 20 Hz-20 kHz. Ultrasound is the sound whose frequency is too high for humans to hear, i.e., the frequency of ultrasound is above 20 kHz. In this work both low-intensity ultrasound (40 and 500 kHz) and the high-intensity ultrasound (20 kHz probe) were used. 10 % (on dry matter) protein model suspensions of soy protein isolate (SPI) and soy protein concentrate (SPC) were treated with ultrasound probe (20 kHz for 15 and 30 minutes) and ultrasound baths (40 and 500 kHz for 15 and 30 minutes). The aim of this study was to observe the effect of ultrasound and sonication on particle size distribution and protein composition of soy proteins. Effect of ultrasound treatment on pH and temperature changes during treatments was also observed. The protein fractions were analyzed by SDS-PAGE electrophoresis, and particle size was determined by laser light scattering using a Mie scattering model. The particle size reduction in protein samples is caused by the ultrasonic cavitation that increases the surface area of proteins. With results of electrophoresis one can conclude that ultrasound treatment induces protein composition changes in isolates and concentrates, and it depends on used frequency and intensity of ultrasound and also on time of treatment. pH didn’ t change significantly upon ultrasound treatments. Temperature increased for all treatments with highest increase was observed for 20 kHz/30 minutes treatment.