DAILY NEWS Dec 28, 2012 7:00 AM - 0 comments

Big future for titanium compounds in new electronics

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By: Peter Harrop, chairman, IDTechEx
2012-12-28

This article shares some of the research carried out for an IDTechEx report requested by several of the world’s largest chemical companies, seeking to de-risk their materials development programs concerned with electrically functional elements and compounds.

These firms wish to do this by understanding what basic families of formulation will be most widely employed in the new electronics and electrics from Nano Electromechanical Devices (NEMS) to completely re-invented large lithium-ion batteries in electric cars and consumer electronics and wide area, flexible solar cells. Firstly, and uniquely, IDTechEx has taken a very close look at all this from the viewpoint of what high-value-added electrical materials will be needed over the coming decade. Secondly, we have looked at which families of compound are the most electronically and electrically versatile making them widely attractive to device designers and which families of compound are likely to sell in the largest gross value into these new markets.

The report is called ‘Most-Needed Chemicals for New Disruptive Electronics and Electrics: De-risk Your Investment’ . It establishes the most widely-demanded electrically-functional elements and compounds in three categories – inorganic elements and compounds, carbon isomers and organic compounds. Thirty-seven families of device are investigated from a chemical viewpoint, looking particularly at 28 important elements, compounds and carbon isomers in the world of the new devices. For example, we group fuel cells and lithium-metal rechargeable batteries (as opposed to lithium-ion) because both need highly sophisticated separator membranes – a major part of their cost. On the other hand, the new nano-lasers, flexible Organic Light Emitting Diodes (OLEDs), printed inorganic Light Emitting Diodes (LEDs) and printed Liquid Crystal Device (LCD) displays are in something of a world of their own when it comes to chemistry.

Many Applications for Titanium

One interesting result is good news for those skilled in the chemistry of titanium. Titanium compounds perform an ever wider variety of electrical and electronic functions – far broader than silicon compounds, for instance. Titanium compounds can be piezoelectrics, even printed to become piezo energy harvesters and sensors. They can be dielectrics in capacitors and transistors, sensitised scaffolds turning light into electricity, electrically-moved pigments and superior anodes and cathodes in lithium-ion batteries intercalating lithium ions. For example, Toshiba, Altairnano and Enerdel batteries have exceptional tolerance of fast charge and discharge in electric vehicles thanks to lithium titanate anodes. Lithium manganese titanium spinel has benefitted energy density when used by others in cathodes. One patent reveals a method of making an effective a spinel compound of formula Li4Ti5O12 for this purpose, for example.

When modified to have a non-stoichiometric layer, titanium dioxide exhibits memristor action, mimicking the human brain. It remembers the current that used to pass through. Titanium salts act as electrets, storing charge on the surface, and some can be micro-machined to perform the many electronic and electrical functions at nano scale. The compounds that are so useful include the oxide, lithium titanates and complex metalloids with other metals in active electrodes of lithium-ion batteries and supercabatteries (Asymmetric Electrochemical Double Layer Capacitors (AEDLC), notably lithium-ion capacitors). Barium titanate is another useful formulation, in this case seen as high-permittivity dielectric, for example in experimental printed field-effect transistors and then there is lead zirconate titanate which is the archetypal piezoelectric. New forms of all these often include inks used in electronics and planned for batteries, and some even demonstrated in circuits printed on paper. Titanium metal also has some new electrical uses.

The hugely popular e-readers, such as the Amazon KindleTM, read as easily as a newspaper, becoming even clearer in sunshine. This is in contrast to a laptop, tablet or even a mobile phone with its LCD or OLED display wiped out. It is because the electrophoretic display electrically moves the same pigments used in newspapers – carbon for black and titanium dioxide for white. By contrast, a Dye Sensitised Solar Cell (DSSC) employs a titanium dioxide scaffold sensitised by a ruthenium based dye to capture light and thus release electrons by a photo-electrochemical reaction not the pn junction familiar in all other forms of solar cell. The result is a flexible solar cell that works well with low levels of light, polarised light as with reflections off snow, water or windows and light at very narrow angles as in the Arctic/Antarctic. Cost can be very competitive. The University of Notre Dame, USA, even has a photovoltaic solar paint based on titanium dioxide. Another breakthrough from the USA is invisible photovoltaic surfaces on windows based on a transparent conductor made of a mixture of silver nanowire and titanium dioxide nanoparticles.

Titanium Nitride and Supercapacitors

Titanium nitride may have a place. Researchers at the University of Maryland and the Korea Advanced Institute of Science and Technology have developed an electrostatic capacitor with 10 billion nanoscale capacitors per square centimeter, giving it 250 times greater surface area than that of a conventional capacitor of comparable size. The misleadingly called Nano Supercapacitor (it is not an EDLC) was being developed primarily as part of a hybrid battery-capacitor system for electric cars but nothing has reached the market yet.

Current commercial supercapacitors range from 0.5 to 40 Wh/kg, yet they think they can reach 3000 Wh/kg, a huge tenfold increase on even the best lithium-ion batteries in the laboratory today. For example, the range of a pure electric car could be 1600 km (1000 miles) vs 160 km (100 miles) today. Each nanopore created in aluminium is 50 nanometers in diameter and up to 30 micrometers deep. Next a sandwich of two layers of titanium nitride (TiN) metal separated by an insulation layer are deposited using Atomic Layer Deposition (ALD) into the pores topped with another layer of aluminium foil.

The versatility of inorganic titanium dioxide matches that of the organic gymnast of electronic and electrical properties, polyvinylidene difluoride (PVDF), though they rarely compete in device application. Both are even used as fillers and binders in new electrical and electronic devices and they are certainly among the compounds likely to be most widely used in the new electronics and electrics over the coming years. Nonetheless, our analysis has revealed even more popular chemistries in the future scenario.

www.idtechex.com



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