Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chemical Instability of the Cobalt Oxyhydrate Superconductor under
  Ambient Conditions   The layered sodium cobalt oxyhydrate superconductor Na0.3CoO2*1.4H2O is shown
through X-ray diffraction and thermogravimetric studies to be one of a series
of hydrated phases of Na0.3CoO2. Further, it is shown that the material is
exceptionally sensitive to both temperature and humidity near ambient
conditions, easily dehydrating to a non-superconducting lower hydrate. The
observation of this stable lower hydrate with c=13.8 angstroms implies that the
superconductivity turns on in this system between CoO2 layer spacings of 6.9
and 9.9 angstroms at nominally constant chemical doping.

37
The categories of this paper are: supr-con
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an