Rare Earth and Ignition

Auermetal was discovered by Carl Auer von Welsbach, an Austrian chemist in 1903. He found that Ferro cerium produces powerful sparks when scraped against a rough surface. Ferrocerium is a man-made metallic material which composed of iron and cerium. One of the applications of ferrocerium is the cigarette lighter flints. In modern times what is commonly called “flint” is actually ferrocerium or Auermetal. This metal is used in lighters as the initial ignition source for the fuel. The first factory of Auermetal production was opened in 1907.

Zippo_Detail

Cigarette lighter flint

 

Ferrocerium has the same function as the steel had in traditional fire stating by natural flint and steel. Lighters using ferrocerium, have a tube containing the ferrocerium and a disc or wheel against which the ferrocerium is. The wheel acts by friction upon the ferrocerium and it should be moved quickly enough to create heat by friction. The ignition temperature originated by cerium has the temperature between 150-180°C.

 

Recent ferrocerium metals produced mostly of iron with an alloy of rare earth metals called cerium mischmetal. The composition consist of approximately 50% cerium, 45% lanthanum, and small amounts of neodymium and praseodymium. This rare earth alloy is too soft to give good sparks, hence 20% iron oxide and 2% magnesium oxide are used to form a harder material. The composition is:

 

Iron: 19%
Cerium: 38%
Lanthanum: 22%
Neodymium: 4%
Praseodymium: 4%
Magnesium: 4%

 

Michmetals are used in Steel industry as an additive for steel treatment as well as in water equipment industry. They have lots of other applications as alloying elements, however traditional and most common use of michmetal is in lighter flints production.

 

References:

 

http://www.toledo-bend.com/VCL/articles/index.asp?request=lighterHistory

http://www.jxmetals.com/sdp/316680/4/cp-1271724/0.html

The contradiction in using green technologies

Dear readers,

One of the main reasons to the increasing applications of rare earth metals is the growing importance of green technologies to save on energy and resources for the sake of the environment. However, as long as no efficient and reliable recycling process is developed, to obtain these rare earths from waste streams, the environmental benefit of such green technologies can be undermined due to the environmental impacts of obtaining rare earths as well as disposing of them.

It is important that with pursuing our dream to green societies and shining futures, we do not make huge sacrifices like what happened to Baotou, China. Baotou is still the world’s biggest supplier of rare earth minerals and today, it’s hell on earth. The winning of rare earth metals is a classic example to show that the cost of destroying the environment is very low in China.

The Toxic Lake of Black Sludge in Baotou

The Toxic Lake of Black Sludge in Baotou

With this blog entry I wanted to draw attention to the fact that we are not only trying to find a way to conquer the shortage of these materials in Europe but in one way or another we are also saving the environment by lowering the need of mining rare earth metals!

More information and insights to this problematic can be find through following links.

http://science.opposingviews.com/rare-earth-metals-green-technology-23284.html

http://www.news.com.au/travel/world-travel/asia/baotou-is-the-worlds-biggest-supplier-of-rare-earth-minerals-and-its-hell-on-earth/news-story/371376b9893492cfc77d23744ca12bc5

http://www.nrc.nl/handelsblad/2014/06/28/kanker-en-gif-de-prijs-van-zeldzame-metalen-in-ch-1394188

Zn-Ce redox flow batteries and the balance problem

Dear readers,

One of the key issues of rare earth elements supply chain is that of the balance problem. Lesser used but naturally abundant materials like cerium and yttrium get stockpiled over the period of time and creates a supply-demand imbalance.

This blogpost deals with a redox flow battery which in part uses cerium as one of its active components. A redox flow battery is different from conventional rechargeable batteries (say Li-ion) in the sense that their active components are more often than not liquids stored in tanks that are pumped into the electrochemical reactor. This gives a way to decouple power and energy output of the battery: energy is how much of active components you can store in a tank and power is how fast your battery stack can delivery that energy. As you could imagine, this makes flow batteries unique in their field of applications. They can be used in large scale stationary applications like grid storage, load balancing, storage device for solar panels etc.

 zncefig

Fig.1: The main species and electrode reactions in a proton exchange membrane Zn-Ce flow battery on charge1

Zn-Ce flow batteries have a relatively high cell voltage (2.2 V) due to the nature of the choice of redox couples used. Such a high cell voltage is also achieved because of the choice of electrolyte: methanesulfonic acid which helps cross the normal water decomposition voltage (1.23 V). The chemistry in itself is easy to remember: during discharge, zinc oxidizes in the positive electrode and cerium gets reduced in the negative electrode. The reverse happens during charge as shown in Fig.1. The redox reaction happens in separate compartments separated by a cation exchange membrane.     The advantages of this system are: relatively high cell voltage for an aqueous system, moderately high energy densities  (25-35 W h/dm3), the chemistries of zinc deposition/stripping as well as cerium redox reactions are well known.

Nevertheless, there are quite a few challenges as well which are listed in a review by Frank.C.Walsh et al. 2 . The oxidation of cerium III/IV  takes place at a relatively high voltage and parasitic reactions like oxygen evolution can lower its efficiency. The anodes used for this reaction are rather expensive like Ti/Pt system and the precious metal coating can wither off over time due to acidic environments. Electrode to membrane gap gets altered due to change of shape in zin electrode during deposition and stripping and there too, hydrogen evolution during charge is a parasitic reaction.

However, the Zn-Ce flow battery research community is trying to solve these problems with different strategies such as 3D porous carbon foam or felt electrodes, electrolyte additive to reduce stress in zinc electrode, use of multiphase modelling to optimize the operating parameters etc.

In a nutshell, Zn-Ce flow batteries are very intriguing in part due to cerium’s high oxidation potential from which the battery derives its high operating voltage. It would be very interesting to observe how the challenges thrown up by the system are tackled as handling cerium is a key to addressing the balance problem.

  1. Li X, Pletcher D, Ponce de Léon C, Walsh FC, Wills RGA. (2015) Redox flow batteries for energy storage using zinc electrodes, Menictas C, Skyllas-Kazacos M, Mariana Lim T (eds), Advances in batteries for large- and medium-scale energy storage: Applications in Power systems and electric vehicles, Woodhead Publishing, 293-315.
  2. Walsh, F. C., Ponce de Léon, C., Berlouis, L., Nikiforidis, G., Arenas-Martínez, L. F., Hodgson, D. and Hall, D. (2015), The Development of Zn–Ce Hybrid Redox Flow Batteries for Energy Storage and Their Continuing Challenges. ChemPlusChem, 80: 288–311. doi: 10.1002/cplu.201402103

 

Rare earths… in your kitchen!

jeroenPicture taken from: http://www.molsequizzen.be/quiz_afbeelding/quiz106_ronde697_18082011095550_dagelijkse%20Kost.png

Dear reader,

At this point I think we are all familiar with the fact that rare earths are employed in a wide range of electronics of different sizes and applications but probably what you didn’t know is that they may be in your in your oven!

Cerium oxides Ce2O3 and CeO2  are usually present in the walls of self-cleaning ovens. Self-cleaning ovens are relatively new so not everybody is familiar with them but they are gaining popularity as they make your life easier (if you are too lazy and feel very sad whenever you have to clean your oven).This kind of ovens operate at 500-600 Celsius degrees in order to burn off the leftovers and spills from baking without using any other kind of instrument or chemical product.

In the self-cleaning ovens that use rare earths, the walls have porous enamel coats. On these walls particles of catalytic cerium (IV) oxide can be found which have the function of help reduce the leftovers to ashes at high temperatures. The only thing that you have to do after the cleaning is finished is clean the ashes that were generated.

If you are curious and want to see more about how these self-cleaning devices work, check this patent out https://www.google.com/patents/US3266477

 

 

Rare-Earth Magnets: An alternative technology for Magnetic Resonance Imaging Scanners

Magnetic Resonance Imaging scanners (MRI) are composed of three basic magnetic field sources (the polarizing magnet, the gradient coils and the excitation coil) which are used to manipulate the magnetic moments of the hydrogen atoms in the body. This article will focus on the main component which is the polarizing magnet.
There are three basic types of magnets used in MRI systems:
Resistive magnets consist of many windings or coils of wire, wrapped around a cylinder, through which an electric current is passed. This causes a magnetic field to be generated. If the electricity is turned off, the magnetic field dies out. These magnets tend to be relatively inexpensive to construct, but require significant amounts of electricity (up to 50 kilowatts) to operate because of the natural resistance in the wire.
Superconducting solenoid electromagnets (made of alloys such as niobium/titanium or niobium/tin surrounded by copper) are the most commonly used. These alloys have the property of zero resistance to electrical current when cooled down to about 10 K so they are cooled with liquid helium. The power supply is connected on either side of a short heated segment of the coil and the current to the coil is gradually increased over several hours until the desired magnetic field is reached. The heated segment is allowed to cool to superconducting temperature and the power supply removed and taken away. The current continues in the closed loop of the coil for years without significant decline. A resulting property is that the magnetic field (typically 1 – 3 T fields) is always present. This makes these systems more economical to operate, but they are still very expensive to build.

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New MRI units constructed with rare-earth permanent magnets are the so called low-field “open” MRI scanners (0.2 – 0.3 T) and they are used as an alternative to the superconducting MRIs. Rare earth permanent magnets generate a high strength permanent magnetic field that does not require electricity, so there is no cost to maintain the field. These magnets are temperature sensitive as any change in temperature will affect the magnetization therefore permanent magnets have a high temperature control requirement. Closed loop temperature control systems with a precision of 0.1 ºC often accompany these MRI units.
Open MRI scanners are available in C-shaped and two-legged designs which can be beneficial at the time of installation and provide a more confortable experience for patients (i.e. less claustrophobic and more quiet).
Low-field MRI scanners have decreased image quality and require a longer scan time compared to high-field MRI scanners. Another drawback is the weight of the currently produced systems for whole-body imaging although the use of Neodymium-Iron-Boron (NdFeB) permanent magnets have cut down the weight of permanent systems from 100 tons to less than 20 tons. These new MRI units are getting lighter with each new generation.

[1] Rakesh K. Gupta and Sunil Kumar, Ed. Magnetic Resonance Imaging of Neurological Diseases in Tropics, Jaypee Brothers Medical Publishers(P) Ltd., New Delhi, India 2014;
[2] http://magnetic-resonance.org/