Che 20032 chemistry of technology presentation
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Transcript of Che 20032 chemistry of technology presentation
CHE-20032: SUSTAINABLE CHEMISTRY
THE CHEMISTRY BEHIND SOME MODERN TECHNOLOGICAL APPLICATIONS
Dr Rob Jackson
Office: LJ 1.16
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
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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.
10
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.