Med Library . org

Open Source Encyclopedia

Lanthanum carbide

Welcome to MedLibrary.org. For best results, we recommend beginning with the navigation links at the top of the page, which can guide you through our collection of over 14,000 medication labels and package inserts. For additional information on other topics which are not covered by our database of medications, just enter your topic in the search box below:

Lanthanum carbide[1]
Identifiers
CAS number 12071-15-7 Yes
PubChem 123280
ChemSpider 109890 Yes
Jmol-3D images Image 1
Properties
Molecular formula LaC2
Molar mass 162.927 g/mol
Appearance tetrahedral crystals
Density 5.29 g/cm3, solid
Melting point

2360°C
Structure
Crystal structure Tetragonal
Space group D174h, I4/mmm, tI6
Coordination
geometry		 6
 Yes (verify) (what is: Yes/?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Lanthanum carbide (LaC2) is a chemical compound. One way in which it is manufactured is through a process of diffusion and evaporation of graphite and lanthanum metal in a DC arc furnace. Researchers use it to study the manufacture of certain types of superconductors and nanotubes.[2]

In 1993, scientists at Wellesley College discovered a way to make lanthanum carbide sealed in a fullerene cage. This led to a compound which was not as susceptible to moisture and air. This made use of the compound possible for containers in which to hold Buckminsterfullerenes, which they dubbed 'buckyjars'.[3]

Contents

Background

Lanthanum Carbide (LaC2) is made by putting graphite and lanthanum in a DC arc furnace. A method for making macroscopic quantities of C60 and the confirmation of the hollow, cagelike structures was published in 1990 by Kratschmer and co-workers.[4] This was followed by the publication of methods for higher fullerenes (C70 and higher). In 1993, scientists discovered how to make a compound which is not as susceptible to moisture and air. They made containers to hold buckminsterfullerenes, or buckyballs; therefore they nicknamed the containers ‘buckyjars’.[3] A few US patents were issued to universities in the mid-1990s; experiments with manufacturing techniques have continued at universities around the globe, including India, Japan, and Sweden.[5]

In LaC72, the lanthanum appears to stabilize the carbon cage. A 1998 study by Stevenson et al. verified the presence of LaC72 as well as La2C72, but empty-cage C72 was absent, based on laser desorption mass spectrometry and UV−vis spectroscopy.[6] A 2008 study by Lu et al. showed that La2C72 do not adhere to the isolated pentagon rule (IPR), but has two pairs of fused pentagons at each pole of the cage and that the two La atoms reside close to the two fused-pentagon pairs. This result lends additional support to the idea that the carbon cage is stabilized by the La atoms.[7]

Properties

In addition to the properties included in the table at right, the magnetic properties of bulk amounts of LaC82 (isolated from various hollow fullerenes) have been tested. Magnetization data for an isolated LaC82 isomer were obtained using a SQUID magnetometer at temperatures ranging from 3 to 300 K. For LaC82 the inverse susceptibility as a function of temperature was observed to follow a Curie-Weiss law. The effective magnetic moment per LaC82 was found to be 0.38μB.[8]

Lanthanum carbide has also shown superconductive properties when converted into a layered lanthanum carbide halide La2C2X2 (X=Br,I). Investigations using high-resolution neutron powder diffraction measurements from room temperature to 1.5 Kelvin showed that it has superconductive properties at about 7.03 Kelvin for X=Br and at about 1.7 Kelvin for X=I, respectively.[9]

References

  1. ^ Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, FL: CRC Press. pp. 4–64. ISBN 0-8493-0594-2 [Amazon-US | Amazon-UK].
  2. ^ Awasthi, Kalpana; Singh, A. K.; Srivastava, O. N. (2002). "Synthesis and Characterization of Lanthanum Carbide Nanotubes". Journal of Nanoscience and Nanotechnology 2 (1): 67–71. doi:10.1166/jnn.2002.078. PMID 12908323.
  3. ^ a b Wellesley Web Page
  4. ^ Kratschmer W, Lamb, LD, Fostiropoulos K, Huffman, DR, Nature 1990, 347:354; Kratschmer W, Fostiropoulos K, Huffman DR, Chem Phys Lett 1990, 170:167; see also Liu M and Cowley JM, Encapsulation of lanthanum carbide in carbon nanotubules and carbon nanoparticles, Carbon 33(2):225-232, 1995.
  5. ^ Awasthu K, Singh AK, Srivastava ON, Synthesis and characterization of lanthanum carbide nanotubes, Journal of Nanoscience and Technology 2(1):67-71, 2002; Lassesson A, Gromov A, Lehlig K, Taninaka A, Shinohara H, Campbell EEB, Formation of small lanthanum carbide ions from laser-induced fragmentation of LaatC82, Journal of Chemical Physics 119(11):5591-5600, 2003 doi 10.1063/1.1599833
  6. ^ Stevenson S, Burbank P, Harich K, Sun Z and Dorn HC, Metal-mediated stabilization of a carbon cage, Journal of Physical Chemistry A 102(17):2833-2837, 1998 doi 10.1021/jp980452m
  7. ^ Lu X, Nikawa H, Nakahodo T, Tsuchiya T, et al., Chemical understanding of a Non-IPR metallofullere: stabilization of encaged metals on fused-pentagon bonds in La2C72, Journal of the American Chemical Society 130(28):9129-9136, 2008
  8. ^ Funasaka H, Sugiyama K, Yamamoto K, Takahashi T, Magnetic properties of rare-earth metallofullerenes, Journal of Physical Chemistry 99(7), 1995 doi 10.1021/j100007a005
  9. ^ Ahn K, Kremer RK, Mattausch H, Simon A, Superconductivity in layered lanthanum carbide halides, Journal of Alloys and Compounds 303-304:257-261, 2000

External links