3,107 research outputs found
Ammonia formation caused by the presence of water in the wet grinding of silicon nitride powder
Si3 N4 powder (amorphous, alpha-, and beta-Si3 N4) was mixed with MeOH containing 8.87 mol. % H2O and ground. The NH3 generation rapidly increased after a grinding time of 100 hours. Silicon nitride sintered material was chosen as one of the high temperature, high strength structural materials and studies of the control of the raw material powder, preparation of the sintered body (finding the right assistant, hot press, high pressure sintering, fracture toughness and oxidation at high temperature were performed
Electrochemical synthesis and properties of CoO2, the x = 0 phase of the AxCoO2 systems (A = Li, Na)
Single-phase bulk samples of the "exotic" CoO2, the x = 0 phase of the AxCoO2
systems (A = Li, Na), were successfully synthesized through electrochemical
de-intercalation of Li from pristine LiCoO2 samples. The samples of pure CoO2
were found to be essentially oxygen stoichiometric and possess a hexagonal
structure consisting of stacked triangular-lattice CoO2 layers only. The
magnetism of CoO2 is featured with a temperature-independent susceptibility of
the magnitude of 10-3 emu/mol Oe, being essentially identical to that of a
Li-doped phase, Li0.12CoO2. It is most likely that the CoO2 phase is a
Pauli-paramagnetic metal with itinerant electrons.Comment: 12 pages, 3 figure
Electronic phase diagram of the layered cobalt oxide system, LixCoO2 (0.0 <= x <= 1.0)
Here we report the magnetic properties of the layered cobalt oxide system,
LixCoO2, in the whole range of Li composition, 0 <= x <= 1. Based on
dc-magnetic susceptibility data, combined with results of 59Co-NMR/NQR
observations, the electronic phase diagram of LixCoO2 has been established. As
in the related material NaxCoO2, a magnetic critical point is found to exist
between x = 0.35 and 0.40, which separates a Pauli-paramagnetic and a
Curie-Weiss metals. In the Pauli-paramagnetic regime (x <= 0.35), the
antiferromagnetic spin correlations systematically increase with decreasing x.
Nevertheless, CoO2, the x = 0 end member is a non-correlated metal in the whole
temperature range studied. In the Curie-Weiss regime (x >= 0.40), on the other
hand, various phase transitions are observed. For x = 0.40, a susceptibility
hump is seen at 30 K, suggesting the onset of static AF order. A magnetic jump,
which is likely to be triggered by charge ordering, is clearly observed at Tt =
175 K in samples with x = 0.50 (= 1/2) and 0.67 (= 2/3), while only a tiny kink
appears at T = 210 K in the sample with an intermediate Li composition, x =
0.60. Thus, the phase diagram of the LixCoO2 system is complex, and the
electronic properties are sensitively influenced by the Li content (x).Comment: 29 pages, 1 table, 9 figure
The MacMahon R-matrix
We introduce an -matrix acting on the tensor product of MacMahon
representations of Ding-Iohara-Miki (DIM) algebra
. This -matrix acts on pairs
of Young diagrams and retains the nice symmetry of the DIM algebra under
the permutation of three deformation parameters , and
. We construct the intertwining operator for a tensor product of
the horizontal Fock representation and the vertical MacMahon representation and
show that the intertwiners are permuted using the MacMahon -matrix.Comment: 39 page
Anisotropic Power-law Inflation
We study an inflationary scenario in supergravity model with a gauge kinetic
function. We find exact anisotropic power-law inflationary solutions when both
the potential function for an inflaton and the gauge kinetic function are
exponential type. The dynamical system analysis tells us that the anisotropic
power-law inflation is an attractor for a large parameter region.Comment: 14 pages, 1 figure. References added, minor corrections include
Macdonald operators and homological invariants of the colored Hopf link
Using a power sum (boson) realization for the Macdonald operators, we
investigate the Gukov, Iqbal, Kozcaz and Vafa (GIKV) proposal for the
homological invariants of the colored Hopf link, which include
Khovanov-Rozansky homology as a special case. We prove the polynomiality of the
invariants obtained by GIKV's proposal for arbitrary representations. We derive
a closed formula of the invariants of the colored Hopf link for antisymmetric
representations. We argue that a little amendment of GIKV's proposal is
required to make all the coefficients of the polynomial non-negative integers.Comment: 31 pages. Published version with an additional appendi
Deformations in N=14 isotones
Systematic analysis of deformations in neutron-rich N=14 isotones was done
based on the method of antisymmetrized molecular dynamics. The property of the
shape coexistence in Si, which is known to have the oblate ground state
and the prolate excited states, was successfully described. The results suggest
that the shape coexistence may occur also in neutron-rich N=14 nuclei as well
as Si. It was found that the oblate neutron shapes are favored because
of the spin-orbit force in most of N=14 isotones. moments and
transition strengths in the neutron-rich nuclei were discussed in relation to
the intrinsic deformations, and a possible difference between the proton and
neutron deformations in Ne was proposed.Comment: 13 pages, 7 figures, sumitted to Phys.Rev.
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