Lanthanum carbide
Encyclopedia
Lanthanum carbide 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 nanotube
s.
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 buckyballs, which they dubbed 'buckyjars'.
C2
) 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. 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’. 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.
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. 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.
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.
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.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
. One way in which it is manufactured is through a process of diffusion and evaporation of graphite
Graphite
The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...
and lanthanum
Lanthanum
Lanthanum is a chemical element with the symbol La and atomic number 57.Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is the first element of the lanthanide series. It is found in some rare-earth minerals, usually in combination with cerium and...
metal in a DC arc furnace. Researchers use it to study the manufacture of certain types of superconductors and nanotube
Carbon nanotube
Carbon nanotubes are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1, significantly larger than for any other material...
s.
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 buckyballs, which they dubbed 'buckyjars'.
Background
Lanthanum Carbide (LaLanthanum
Lanthanum is a chemical element with the symbol La and atomic number 57.Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is the first element of the lanthanide series. It is found in some rare-earth minerals, usually in combination with cerium and...
C2
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
) 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. 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’. 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.
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. A 2008 study by Lu et al. showed that La2C72 do not adhere to the isolated pentagon rule (IPR)
Fullerene chemistry
Fullerene chemistry is a field of organic chemistry devoted to the chemical properties of fullerenes. Research in this field is driven by the need to functionalize fullerenes and tune their properties. For example fullerene is notoriously insoluble and adding a suitable group can enhance...
, 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.
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 SQUIDSQUID
A SQUID is a very sensitive magnetometer used to measure extremely weak magnetic fields, based on superconducting loops containing Josephson junctions....
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
Magnetic moment
The magnetic moment of a magnet is a quantity that determines the force that the magnet can exert on electric currents and the torque that a magnetic field will exert on it...
per LaC82 was found to be 0.38μB.
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.