Can the lotus of ceramics address the balance problem?

Dear readers, the intention of this post is to explore why rare earth oxides can be the lotus of ceramics due to one of their interesting intrinsic property. Rare earth based magnets are regularly used in wind turbines, nearly in 14% of them [1]. What if there is another use for rare earths in the same device where in winter freezing water films on blades can lead to a disaster? Well, it turns out that rare earth oxides can save those hefty wind turbine blades because they are intrinsically hydrophobic.

Hydrophobicity is usually achieved by polymeric modifier coatings but they suffer degradation in harsh environments. Water repelling surfaces have a gamut of applications in the field of energy, transportation, medicine, corrosion resistance etc [2]. Conventional ceramics like alumina are highly hydrophilic, so why should rare earth oxides, ceramics themselves be hydrophobic?

Water repelling ceramic

Figure: Water repelling REO ceramics [3]

Everything comes down to electronic configuration. Water’s oxygen atoms share some of their electrons with electron deficient aluminum atom and the oxygen in the ceramic shares electron with the hydrogen atom [3] resulting in a hydrophilic hydration structure. But, the unfulfilled 4f electrons of rare earth oxides are shielded from bonding by the full octet of an outer shell. This should make it tough for the water and REOs to form interfacial bonds.

Researchers in MIT have found out that, this property indeed makes the family of rare earth oxides intrinsically hydrophobic [4]. They prepared small discs of these oxides and dropped water on to it. And each one of them indeed repelled the liquid. They characterized the wetting properties of these discs by measuring the contact angle and it was in the range of 100-115, comparable to Teflon when has a contact angle of 119 degree. Interestingly enough, ceria remained hydrophobic even after being subjected to a harsh high temperature environment of 1000 o C. This remarkable property of ceria, if completely harnessed can possibly address the balance problem of lanthanides [5]

Finally, rare earth oxides are one of the important products in the recycling chain of lanthanides and a larger application requirement for it fuels the recycling research with further impetus. I would like to end this blogpost with a beautiful video of a water droplet bouncing off ceria which can be found in the link below.

http://www.nature.com/news/ceramics-surprise-with-durable-dryness-1.12250

  1. Study of rare earths and their recycling, Oko Institut, 2011 report for the Greens/EFA group in the European parliament.
  2. http://newsoffice.mit.edu/2013/ceramic-hydrophobic-materials-0120
  3. Ceramics surprise with durable dryness, Nature news, 20 January 2013

http://www.nature.com/news/ceramics-surprise-with-durable-dryness-1.12250

4. Hydrophobicity of rare-earth oxide ceramics, G.Azimi et al., Nature Materials 12, 315‚Äď320 2013

5. Rare-Earth Economics: The Balance Problem, K.Binnemans et al., JOM, Vol. 65, No. 7, 2013

Quackery and radioactive substances!

QUACKSource: https://embracediabetes.files.wordpress.com/2012/05/quack-doctor.jpg

For a long time we have been talking about rare earths on this blog. Today, we are going to change the direction a bit and we are going to talk about the close neighbors of the rare earths: the actinides. As the rare earths, the group of the actinides is also interesting and well known mostly because of their radioactive properties. In the early 20th century, the quackery involving radioactive substances was very popular. But what is quackery and what is a quack?

Quackery:
1. False pretense to medical skill, knowledge, or qualification; medical charlatanry.
2. The actions or practice of a medical charlatan. [1]

Quack:
n.  1. An untrained person who pretends to be a physician and dispenses medical advice and treatment.
      2. A charlatan; a mountebank. [2]

At the beginning of 1900, the curative waters at Hot Springs, Arkansas, USA, ¬†were the most famous ones. Around that date it was discovered that the waters in many health springs were radioactive because of the presence of radon gas, thus led some people to think that the wonderful curative properties of these waters were related to the presence of radioactivity. In the same way as some years ago it was in to put the name “mini” or “nano” in every ¬†device although they were not mini or nano size, some people thought that it would be cool to use the terms “radioactive” or/and “radium” in their products and claim that they had some curative properties[3]. Here you can find a couple of examples of those products:

- Revigator: the idea behind this invention was to have the possibility of having at home in an accessible way the curative properties of the hot springs. So basically, it was a pot that had a radium-containing ore (Carnotite for example) on the inner walls. Then you could store water in that container overnight and drink it next day and enjoy the healthy properties of radon. The problem with this was not the radiation because it was very low, but the fact that those ores usually contain heavy and hazardous metals.

revigatorhttp://www.cowanauctions.com/itemImages/ggg7649.jpg

-Radithor: advertised as “a cure for the living dead” and “perpetual sunshine”. It was just water containing some radium or thorium or both. You were¬†supposed¬†to drink it directly from the bottle and then wait until it cured all your¬†illnesses. Eben Byers was an¬†athlete who injured his arm and then was suggested to drink radithor as part of his treatment. In that moment no one knew that the creator of radithor was a false doctor. It is believed that Byers drank more than 1400 bottles of raditor[4], he lost his jaw and died of cancer. Byers was well known and his death caught the attention of the press. The Wall Street Journal published an article called “The radium water worked fine until his jaw came off”. With this, the investigations started and also some regulations started to be established.¬†radithorhttp://www.cowanauctions.com/itemImages/ggg7649.jpg

By the way, talking about jaws, there was a radioactive tooth paste that was once commercialized. It’s name was Doramad radioactive toothpaste. It was produced by¬†Auergesellschaft, an industry that was making mantles for gas lights and thus had reserves of rare earths, thorium and uranium compounds. On the back of the toothpaste tube you could read the following:

“What Does Doramad Do?¬†Its radioactive radiation increases the defenses of teeth and gums. The¬†cells are loaded with new life energy, the bacteria¬†are hindered in their destroying effect. This explains the excellent prophylaxis and healing process¬†with gingival diseases. It gently polishes the dental enamel so it turns¬†white and shiny. Prevents dental calculus. Wonderful lather and a new,¬†pleasant, mild and refreshing taste. Can be applied sparingly.”[5]

Feel like reading more about this kind of quackery? https://www.orau.org/ptp/collection/quackcures/quackcures.htm

References

[1]http://www.thefreedictionary.com/quackery
[2]http://www.thefreedictionary.com/quack
[3]https://www.orau.org/ptp/articlesstories/quackstory.htm
[4]https://talesfromthenuclearage.wordpress.com/2010/08/30/drink-radithor/
[5]https://www.orau.org/ptp/collection/quackcures/toothpaste.htm