Posts Tagged ‘coating’
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February 5th, 2010
Oxidized gold thin films
This is an area of research I wasn’t previously familiar with…oxidised thin films. They are claimed to have been shown to function as a direct drop-in replacement for the normal indium tin oxide anode in high-performance flexible organic light-emitting diodes fabricated on plastic substrates (as shown). The authors of this research claim the thin films offer a new materials technology for roll-to-roll processing of next-generation flexible organic optoelectronics. Which could be used in applications such as solid-state lighting. Promising stuff…. -
January 22nd, 2010
Fault current limiters using gold-alloy coatings
Some months ago I blogged on the use of superconductors for fault current limiters devices. These require the use of a metallic shunt top layer to give a degree of thermal and electrical protection should a fault in the superconducting tape develop. This metallic layer is typically 50-100nm thick and must be resistant to oxidation at the high temperatures which can arise during both processing steps and in service during current overload situation. It must also serve as a barrier to prevent ingress of moisture into the YBCO superconductor. This story (although from last year – I’ve only just been told about here in Japan) shows the use of silver-gold alloy layers in a practical example of this technology.
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January 13th, 2010
Seeing through gold
Chemical and Engineering News is reporting that thin layers of evaporated gold are being used to help study the layer-dependent surface property of graphene. Advances in graphene technology have been hampered by the small number of microscopy and spectroscopy techniques capable of “seeing” graphene and distinguishing between samples of various thicknesses. The research from the National Center for Nanoscience & Technology, in Beijing has been published in JACS.
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October 27th, 2009
Ford Motor Company and Au Nanoclad™
Some weeks ago I posted on the subject of fuel cell separator plates and how gold-coated stainless steel was proven to be the best material for this application, in terms of conductivity and durability. The only issue was cost – what was need was a reduced thickness gold coating, still displaying the performance of a thicker coating.
Well, according to a presentation to be made at Fuel Cells Durability & Performance 2009 (December 8-9, 2009 · Alexandria, VA USA) The Ford Motor Company is to present on ”Nanometer Range Gold Coated Stainless Steel for Automotive Polymer Electrolyte Membrane Fuel Cell Bipolar Plate”.
Apparently, Ford is currently developing metallic bipolar plate technology with thin gold-coated stainless steel (under the brand name Au Nanoclad™) provided by Daido Steel. They claim that the use of nanometer range gold coating delivers the required electrical conductivity and corrosion resistance with least impact of cost of gold. Additionally, gold-coated stainless steel shows anodic passivation, thereby exhibiting robustness towards coating defects including surface scratches during the manufacturing of the bipolar plate. Apparently the presentation at the conference will include the ex-situ and in-situ testing data for this material.Looks like a potentially fantastic new use for gold if the fuel cell market takes off…..
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October 23rd, 2009
New Gold Solar-Reflective Window Coatings?
‘Gold’ in this story could just relate to the colour rather than the metal itself but, although it doesn’t say it specifically, I suspect this might actually be a new market niche for gold. The story says:Gold aircraft window coatings by PPG Industries’ aerospace transparencies group are being introduced at the National Business Aviation Association (NBAA) annual meeting and convention offer aircraft manufacturers aesthetic choices in solar-reflective coating technology. PPG’s solar-reflective coatings for glass and plastic aircraft windows reduce the amount of infrared energy entering the cockpit and cabin for cooler temperatures and reduced air-conditioning load.
Gold’s role in glazing applications has been known for a long time (see this Gold Bulletin paper here). I imagine this technology maybe based on the application of gold nanoparticles – as highlighted in this other Gold Bulletin paper- rather than the more traditional sputtered coatings.
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September 11th, 2009
New PCB finishes
The demand for improved multifunctional, high reliability printed circuit board (PCB) finishes is growing. Another product has been added to the market; Dow Electronic Materials has just announced its latest offering -Aurolectroless™ SMT immersion gold for ASIG (autocatalytic silver immersion gold) final finish process.Gold wire bonding is claimed to show exceptional bond strengths when using the complete ASIG process
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August 28th, 2009
Carbon nanotubes and toxicity – can gold lend a hand?
Carbon nanotubes (CNTs) are truly extraordinary materials. Many of you reading this will already know a fair bit about them I’m sure, but for those that don’t I suggest you take a quick look at this page which summarises their uses and potential well. There have, however, always been concerns about potential toxicity of these nanomaterials – because of their diminutive size, CNTs have been shown to be able to accumulate in cells, eventually leading to cell death.
This is clearly a significant issue for utilising CNTs in certain fields. One such field in molecular therapeutics and imaging – indeed CNTs have been shown to hold great promise as contrast agents for photoacoustic detection and photothermal killing of individual bacteria in blood system. However, they were never fully developed as such because of the ongoing concerns around toxicity…
It’s for this reason I was impressed by this recent publication in Nature Nanotechnology. The team, led by Jin-Woo Kim and Vladimir Zharov of the University of Arkansas, have addressed this problem by depositing a thin layer of gold around the carbon nanotubes. The gold layer enhanced absorption of laser radiation and reduced toxicity. In vitro tests showed only minimal toxicity associated with the golden nanotubes. Compared to existing nanoparticles, the golden nanotubes also exhibited high laser absorption at a miniscule diameter. The golden nanotubes required extremely low laser-energy levels for detection, and low concentrations were required for effective diagnostic and therapeutic applications.
For more information see the University of Arkansas press release
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August 18th, 2009
Superconducting and Element 79
I really like some of the technology perspectives offered by the Scientist NZ blog.
This one, on superconductivity, reminded me of some work World Gold Council carried out looking at gold’s use in this field. In turns out that in one use of superconductors (in the fault current limiters application), the most recent generation of materials that are able to operate at higher temperatures, such as YBCO (YBa2Cu3O7), require the use of a metallic shunt top layer to give a degree of thermal and electrical protection should a fault in the superconducting tape develop. This metallic layer is typically 50-100nm thick and must be resistant to oxidation at the high temperatures which can arise during both processing steps and in service during current overload situation. It must also serve as a barrier to prevent ingress of moisture into the YBCO superconductor.
We found research that showed that sputtered silver, gold and silver-gold alloy layers have so far shown the best combination of properties for this applications including electrical and thermal conductivities, contact resistance, specific heat capacities, oxidation potential, lattice constant, and coefficient of linear expansion (High-power-density fault-current limiting devices using YBa2Cu3O7 superconducting films and high resistivity alloy shunt layers, H Yamasaki, M Furuse and Y Nakagawa, Appl. Phys. Lett., 2004, 85, 4427)
By the way, the superconducting properties of gold intermetallics themselves were reviewed by Khan and Raub in Gold Bulletin, although no intermetallic compound of gold has yet been found to exhibit sufficient superconductivity to make it industrially interesting.
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April 29th, 2009
Fire Protection
This piece in the UK’s Daily Telegraph features the launch of a new advanced fireman helmet. Traditional it isn’t and the story likens the helmet to the head gear of a Star Wars stormtrooper.
The visor of the helmet has a gold-plated coating. The high reflectivity and low emissivity of gold, as well as its lack of tarnishing mean the metal is used in a number of applications in the control of radiant energy. Papers published in Gold Bulletin provide a good explanation of the science behind this here and here ……….
Richard Holliday
Trevor Keel
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