Che 20032 chemistry of technology presentation

CHE-20032: SUSTAINABLE CHEMISTRY

THE CHEMISTRY BEHIND SOME MODERN TECHNOLOGICAL APPLICATIONS

Dr Rob Jackson

Office: LJ 1.16

[email protected]

http://www.facebook.com/robjteaching

http://twitter.com/robajackson, #che20032

Plan of session

• Timetable• Overall aims and assessment• Resources• Possible applications• Discussion of some applications• Global sustainability issues

CHE-20032 Chemistry of Technology

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Timetable

• Lecture: 28/03/14, 14:00-16:00 (CBA 2.017)• Drop-in session to finalise poster titles , 04/04/14,

12:00-13:00 (CBA 1.074/5)• Reserve: 09/05/14, 14:00-16:00 (CBA 2.017)• Poster Session: 16/05/14, 14:00-16:00 (Multy Lab)• Planned poster size: A1• Poster titles/topics needed by 04/04/14• Posters to be submitted by e-mail to me as PDF files

by 17:00 08/05/14


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Overall aims and assessment

• To investigate the chemistry behind some modern technological applications.

• To consider environmental issues (mineral resources, recycling).

• To prepare and present a poster explaining a material or application in detail (25% of module).

• At the poster session you will answer questions about your posters, and posters will be marked using a scheme (to be put on the KLE).


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Resources

• Most information will come from the web.

• Web links will be listed on the slides and added to my teaching pages.

• Key links will also be put on Twitter (#che20032).


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Some possible topics(see also: http://www.bbc.co.uk/news/science-environment-

20084285)

• Li ion batteries (mobile phones, laptops etc.)• Li air batteries• Photovoltaic materials (used in solar power)• Smart screen materials (OLED, plasma, LCD)• Solid Oxide Fuel Cell (SOFC) materials• Graphene as a silicon replacement in circuits• Lightweight materials for vehicles


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Lithium ion batteries

• Lithium ion batteries are widely used in mobile electronic devices from phones to laptops.

• They are continually being developed and improved; some of the latest research is described here:http://chemistry.st-and.ac.uk/staff/pgb/group/


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How lithium ion batteries work – (i)

• Their design is based on intercalation compounds (compounds formed by the reversible addition of ‘guest’ ions to a host lattice).

• The electrolyte is a conducting polymer such as polyacetylene:

n (H-CC-H)


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How lithium ion batteries work – (ii)

• The anode is composed of Li embedded in graphitic carbon, forming LixC6.

• The cathode is made from Li combined in an intercalation compound with a transition metal oxide like CoO2, forming LixCoO2.

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Lithium ion battery diagram



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Improvements to the lithium ion battery

• There is much current research on improving the performance of lithium batteries (e.g. link on slide 7)

• These have focussed on using nanostructured materials for the cathode and anode.– The rationale is that the ‘hopping distance’

for the Li+ ions is reduced.

Lithium air (oxygen) batteries(potentially higher energy density than Li ion batteries)


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The anode is either lithium metal or a lithium containing compound. The anode is made of mesoporous carbon containing a catalyst to enhance lithium reduction from Li+ to Li. http://chemistry.st-and.ac.uk/staff/pgb/group/lio.html

The Li+ ions combine with O2- ions at the cathode; the process is reversed on charging.

Photovoltaic materials

• Photovoltaic materials are used in solar power devices, e.g. solar panels, to produce electric current from sunlight.


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http://www.technologystudent.com/energy1/solar5.htm

The photovoltaic effect is the creation of an electric current in a material when exposed to light.

Organic photovoltaic materials


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http://en.wikipedia.org/wiki/Organic_solar_cell#Organic_photovoltaic_materials

Some organic photovoltaic materials

A single layer photocell

Smart screen materials

• Smart screen technology is developing fast.

• The latest, including the curved screens being marketed by Samsung, use OLEDs (organic light-emitting diodes).

• Other materials used include ‘plasmas’ and liquid crystals.


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A curved OLED screen

OLED screens

• OLEDs* work on the principle that certain organic molecules emit light when an electric current is passed through them. No backlight is required.

• An example of a molecule used in OLED devices is Al(C9H6NO)3, which is often abbreviated to Alq3


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*PLEDs work on the same principle with polymers.

Solid oxide fuel cells (SOFCs)

• Fuel cells convert the chemical energy from a fuel into electricity via a chemical reaction (usually oxidation).

• Solid oxide fuel cells have solid oxide electrolytes, e.g. Y2O3 stabilised ZrO2.

• Cathode and anode materials have particular properties as well.


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In this example, the fuel is H2, which is oxidised by the incoming O2- ions, releasing electrons.

http://en.wikipedia.org/wiki/Solid_oxide_fuel_cell

Solid oxide fuel cell materials

• Research is being done to improve the performance of SOFCs– This includes improving the materials used

to reduce the running temperature.– Also proton-conducting SOFCs are being

developed, where protons are transported through the electrolyte instead of O2- ions, which also reduces the running temperature.


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Graphene as a silicon replacement in circuits

See: http://www.bbc.co.uk/news/science-environment-25944824

• Graphene is being investigated as an alternative to silicon in integrated circuits:


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• The paper describes how the problems with using graphene in circuit design has been overcome

Lightweight materials for vehicleshttp://www.boeing.com/commercial/aeromagazine/articles/qtr_4_06

/article_04_2.html

• This is a slightly less ‘chemical’ topic, but composite materials are increasingly being used in vehicle construction.– For example, the Boeing 787 Dreamliner only has

10% steel, and the rest of it is constructed from: 15% Ti, 20% Al and 50% composite materials.

– (More research needed to identify ‘composite materials’!)


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Rare earth (RE) elements and resource issues

• The ‘rare earth’ elements are widely used in modern technological devices. They are more often called lanthanides now.

• They are not all ‘rare’; Ce is the 25th most common element on the planet!

• However there are supply problems with some.


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The varied colours of the RE nitrates


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http://www.bbc.co.uk/news/magazine-26687605

Pm (promethium) is missing as it doesn’t occur naturally

Some applications of the RE elements

• Neodymium is magnetic (10 times as powerful as iron magnets): used in computer hard drives and miniature speakers.

• Dysprosium is used in control rods in nuclear reactors

• Erbium is for sending signals along optical fibres – it produces light in the near IR.

• Europium is used for anti-counterfeiting in Euro notes (the blue-pink stars on the €20 note contain Eu!).


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Resourcing issues with RE elements


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More than 85% of the world's supply of rare-earth metals comes from China, including almost 100% of the ‘heavy’ ones. In 2010 China started controlling output, with a dramatic effect on prices.

Che 20032 chemistry of technology presentation

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