Lithiated Graphite in Fusion Reactors

Nuclear fusion powers the stars and could be used to supply clean energy on Earth. A nuclear fusion plant would produce ten times more energy than a conventional nuclear fission reactor.

Scientists have been investigating the "plasma-material interface", the region in a fusion reactor where the inner lining cones into contact with the extreme heat of the plasma. A major challenge in finding the right coatings to line fusion reactors is that the material changes due to extreme conditions inside the reactors where temperatures can reach millions of degrees.

One such lining material uses lithium which is applied to the inner graphite wall of the reactor and diffuses into the graphite creating an entirely new material called lithiated graphite.
During a fusion reaction, some of the deuterium fuel atoms strike the inner walls of the reactor and either "pumped", causing them to bind with the lithiated graphite, or returned to the core and recycled back to the plasma.
The intense thermal energy inside the reactor causes tiny micro- and nano- scale features to "self-organise" on the surface of the lithiated graphite under normal plasma-surface interaction conditions. The surface only continues pumping for a few seconds before being compromised by damage induced by the extreme internal conditions.

Reference:
Purdue University (2010, July 27). Promise for nuclear fusion test reactors, findings show. ScienceDaily. Retrieved July 28, 2010, from http://www.sciencedaily.com­ /releases/2010/07/100727142415.htm

Study Questions

1. Define nuclear fusion.
2. Write an equation to represent a nuclear fusion reaction that might take place in a sun.
   
3. Define nuclear fission.
4. Write an equation to represent the nuclear fission of uranium-235.
   
5. How are deuterium atoms similar to hydrogen atoms?
6. How are deuterium atoms different to hydrogen atoms?
7. Name another isotope of hydrogen and give its symbol.
8. Name two allotropes of carbon.
9. Discuss the ways in which the two allotropes are the same.
10. Discuss the ways in which the two allotropes are different.
    
11. Draw a structure for graphite.
12. Use the drawing above to describe how lithiated graphite might be formed.
13. Discuss how deuterium atoms in the fuel plasma could bind to lithiated graphite.
    

Buckyballs in Space

In 1970, Japanese professor Eiji Osawa predicted the existence of buckyballs.
In 1985, Buckminster Fullerenes were first observed in the laboratory.
In 1996, Sir Harry Kroto, Bob Curl and Rick Smalley shared the Nobel Prize in chemistry for the discovery of buckyballs.
They were named after the architect Buckminster Fuller because they resemble his geodesic domes which have interlocking circles on the surface of a partial sphere. Buckyballs, 60 carbon atoms arranged into a three-dimensional spherical structure resembling a soccer ball, are allotropes of carbon.
Buckyballs have been found on Earth in candle soot, layers of rock and meteorites.

Astronomers using NASA's Spitzer Space Telescope have now discovered buckyballs in space, in a planetary nebula named Tc 1. Planetary nebula are the remains of stars that shed their outer layers of gas and dust as they age. A compact, hot star, or white dwarf, at the centre of the nebula illuminates and heats these clouds of discarded material. The buckyballs were found in these clouds when the astronomers used Spitzer's spectroscopy instrument to analyze infrared light from the planetary nebula and see the spectral signatures of the buckyballs. The data from Spitzer were compared with data from laboratory measurements of the same molecules and showed a perfect match.

Reference:
Jan Cami, Jeronimo Bernard-Salas, Els Peeters, and Sarah Elizabeth Malek. Detection of C₆₀ and C₇₀ in a Young Planetary Nebula. Science, 2010; DOI: 10.1126/science.1192035

Study Questions:

1. What is an allotrope?
2. Name two naturally occurring allotropes of carbon other than buckminster fullerenes.
3. In what ways are these allotropes above the same?
4. In what ways are these allotropes above different?
5. It has been suggested that buckyballs could be used in armour, drug delivery, and, superconductors. What do you think the physical and chemical properties of buckyballs are likely to be?
   
6. Name the other allotrope of oxygen besides (bi)molecular oxygen.
   
7. In what ways are the two allotropes of oxygen the same?
8. In what ways are the two allotropes of oxygen different?
9. There are several allotropes of phosphorus. Discuss the similarities and differences of these allotropes.
   

Nanoparticles in Sunscreens

Titanium dioxide and zinc oxide are currently used for sunscreens because they absorb and scatter light. University of Tennessee, Knoxville, scientists have found that nanoparticles found in ivy may protect skin from UV radiation at least four times better.

A yellowish material is secreted by the ivy to aid it in clinging to surfaces. Nanoparticles within this material create the ability for the vine leaves to hold almost 2 million more times than its weight as well as provide the ability to absorb and disperse light due to their large surface-to-volume ratio. Sunscreens made with ivy nanoparticles would probably not need to be re-applied after swimming because the nanoparticles are more adhesive, and, while metal-based sunscreens give the skin a white tinge, the ivy nanoparticles are virtually invisible.

The study indicates that ivy nanoparticles are less toxic to mammalian cells than small-scale metal oxides, have a limited potential to penetrate through human skin, and are easily biodegradable.

Reference:
University of Tennessee at Knoxville (2010, July 19). Nanoparticles in English ivy may hold the key to making sunscreen safer and more effective. ScienceDaily. Retrieved July 22, 2010, from http://www.sciencedaily.com­ /releases/2010/07/100719162955.htm

Study Questions

1. Write the formula for titanium dioxide and for zinc oxide.
2. Give the oxidation state (number) for titanium and zinc in the compounds above.
3. What is a nanoparticle?
4. Explain the term surface-to-volume ratio.
5. Why do nanoparticles have a large surface-to-volume ratio?
6. How is the scattering of light affected by differences in surface-to-volume ratio?
7. Why are titanium dioxide and zinc oxide the preferred metal oxides for use in sunscreens?
   

Growing Glycine Crystals

Chemists from New York University and St. Petersburg State University have been observing the growth of crystals of hippuric acid, a derivative of the amino acid glycine, and have discovered a new crystal growth phenomenon, a crystal that continually changes shape as it grows!

As molecules were added to the end of fine crystalline needles, stresses built up at the tips of the crystals resulting in a helical twist, just like you find in DNA's helix.
The twisiting process was reversed when the crystals thickened from the opposite end of the growing tip, ie, the crystals stiffened, undoing the twisted formations because the elasticity of the crystals decreases as they become thicker and this squeezes out the deformations formed at the growing tip.
The competition between twisting and untwisting creates needles with a rainbow of colours, characteristic of tightly wound helices and untwisted ribbons.

Reference:
New York University (2010, July 17). Chemists grow crystals with a twist -- and untwist. ScienceDaily. Retrieved July 19, 2010, from http://www.sciencedaily.com­ /releases/2010/07/100716125641.htm

Study Questions

1. What is the abbreviation for glycine?
2. Give the formula for glycine.
3. Why is glycine considered to be an amino acid?
4. Explain why glycine would be considered to be amphiprotic.
5. Write an equation to show how glycine could act as an acid.
6. Write an equation to show how glycine could act as a base.
7. Write an equation to show the formation of a cation from glycine in acidic solution.
8. Write an equation to show the formation of an anion from glycine in basic solution.
9. Compare the description of crystal growth as given in the article with what we consider to be the more "traditionally accepted" view of crystal growth.
   

Topological Insulators

In an electrical conductor, negatively charged electrons can hop between atoms and move freely in their interior or on the surface. These free electrons are responsible for the generation of electric current. For most metals, electrons in the interior carry most of the current, while surface electrons are only weakly mobile. Some materials, such as glass, have structures that impede electron flow and are called insulators.

A topological insulator is a substance that acts as an insulator in its interior while permitting the movement of charges on its boundary. This can occur when a perpendicular magnetic field is applied, this is known as the quantum Hall effect.
Princeton scientists have discovered a new type of typological insulator, an antimony crystal, which does not require the application of a magnetic field.

Reference:
Jungpil Seo, Pedram Roushan, Haim Beidenkopf, Y. S. Hor, R. J. Cava, Ali Yazdani. Transmission of topological surface states through surface barriers. Nature, 2010; 466 (7304): 343 DOI: 10.1038/nature09189

Study Questions

1. What is required in order for a material to be considered an electrical conductor.
2. Give three examples of good electrical conductors.
3. Give three examples of electrical insulators.
4. In general, what type of substances conduct electricity?
5. In general, what type of substances do not conduct electricity?
6. If electrons are negatively charged, why are atoms considered to be neutral?
7. Why do you think electrons are more free to move within the interior of a material compared to its surface?
   

Growing Egg Shells

For a long time scientists have believed that a chicken egg shell protein called ovocledidin-17 (OC-17) played a part in the formation of egg shells. This protein is only found in the mineral region of the egg which is the hard part of the shell, and, it appears to influence the transformation of amorphous calcium carbonate into calcite crystals by acting as a catalyst for crystal growth.

Scientists have now created simulations to show how the protein binds to the amorphous calcium carbonate surface using two clusters of arginine residues located on two loops of the OC-17 protein and creating a chemical clamp to nano sized particles of calcium carbonate. While clamped in this way, the OC-17 protein encourages the nanoparticles of calcium carbonate to transform into calcite crystallites that form the tiny nucleus of crystals that can continue to grow on their own. When the crystal nucleus is sufficiently large to grow on its own, the OC-17 protein desorbs, or, falls off. This frees up the OC-17 protein to promote yet more crystallization.

Reference:
Colin L. Freeman, John H. Harding, David Quigley, P. Mark Rodger. Structural Control of Crystal Nuclei by an Eggshell Protein. Angewandte Chemie International Edition, 2010; 49 (30): 5135 DOI: 10.1002/anie.201000679

Study Questions

1. What are the elements common to all proteins?
2. Proteins are actually polymers. What is the name given to the monomers that make up a protein?
3. What kind of bond binds these monomers together within the protein?
4. What is the formula for arginine?
5. Would the "loops" referred to in reference to the structure of OC-17 be part of its primary, secondary or tertiary structure? Explain your answer.
6. What does the term amorphous mean?
7. How does amorphous calcium carbonate differ from calcite crystals?
8. What is the definition of a catalyst?
9. Do you think OC-17 could be accurately described as a catalyst? Explain your answer.
   

Stripping Neon

The Linac Coherent Light Source (LCLS) delivers an intense pulse of X-rays designed to image atoms and molecules.
When the LCLS X-rays are tightly focused by mirrors, each pulse destroys any sample it hits.

LCLS pulses have been used to strip electrons away from atoms of neon one at a time.
Using a shorter pulse, fewer electrons are stripped away and less damage is done.
By varying the photon energies of the pulses, the electrons can be removed from the outside in, or, from the inside out creating so-called " hollow atoms".

The 2 electrons in the innermost electron shell closest to the nucleus are the hardest to strip away, but they also most readily absorb photons of X-ray light and so are the most vulnerable to being stripped away by intense X-rays. At low photon energies, the outer electrons are removed, leaving the inner electrons untouched. At higher photon energies the inner electrons are the first to be ejected, then the outer electrons cascade into the empty inner core, only to be kicked out by later parts of the same X-ray pulse.

Reference:
L. Young, E. P. Kanter, B. Krässig, Y. Li, A. M. March, S. T. Pratt, R. Santra, S. H. Southworth, N. Rohringer, L. F. DiMauro, G. Doumy, C. A. Roedig, N. Berrah, L. Fang, M. Hoener, P. H. Bucksbaum, J. P. Cryan, S. Ghimire, J. M. Glownia, D. A. Reis, J. D. Bozek, C. Bostedt, M. Messerschmidt. Femtosecond electronic response of atoms to ultra-intense X-rays. Nature, 2010; 466 (7302): 56 DOI: 10.1038/nature09177

Study Questions

1. What is the name given to the removal of electrons from a gaseous atom?
2. What is the charge resulting from the removal of an electron from a neon atom?
3. Write the electron configuration for the neon atom and for the species produced after an electron has been removed.
   
4. Write an equation to show the removal of an electron from a gaseous neon atom.
5. In a similar set of experiments, nitrogen was used instead of neon. Write the electron configuration of a nitrogen atom and of the species produced after an electron has been removed.
6. Do you think it would be easier to remove an electron from an atom of neon or from an atom of nitrogen? Explain your answer.
7. Why do you think the researchers chose to use neon and nitrogen gases for these experiments?
   

Lunar Graphite

Scientists have been analyzing 3.8 billion year old Mare Serenitatis lunar samples brought back to Earth by astronauts in 1972. Raman spectroscopy of the sample allowed scientists to create an image of the minerals it contained. The scientists were surprised to find graphite and graphite whiskers, formed under very hot conditions between 1273K and 3900K. The graphite whiskers appeared to be a few microns in diameter and up to 10 microns long.
The scientists believe that the carbon they detected came either from the object that made the impact crater, or, that it condensed from the carbon-rich gas that was released during the impact.

Reference:
A. Steele, F. M. McCubbin, M. Fries, M. Glamoclija, L. Kater, and H. Nekvasil. Graphite in an Apollo 17 Impact Melt Breccia. Science, 2010; 329 (5987): 51 DOI: 10.1126/science.1190541

Study Questions:

1. Carbon is present on Earth in different forms. What is the term given to these different forms?
2. Name two different natural forms of carbon found on Earth.
3. In what ways are the two different forms of carbon named above similar?
4. In what ways are the two different forms of carbon named above different?
   
5. Name two different synthetic forms of carbon.
6. Give a use for each synthetic form of carbon named above.
7. Why do you think the scientists were surprised to find graphite in these lunar samples?