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.


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.






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.




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.


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