Page 12 - PARVEEN, S
P. 12
019 SAHA, D.K. (Material Science Division, metals is linear in the Cauchy deviation C* = (C 12
Atomic Energy Centre, Ramna, Dhaka). LONG- − C 44)/(C I2 +C 44), such linearity is also seen in bcc
RANGE ORDER PARAMETER OF Cu-21.6 transition elements. Finally via elastic constants
AT.% Pd ALLOY. J. Bang. Acad. Sci., 2007, mass density and atomic volume, a correlation
31(2), 197-201. between C* and the Debye Ω temperature has been
established for the five fcc transition elements.
Order-disorder phases of Cu-21.6 at.% Pd alloy This correlation indirectly sets up a relation
have been studied by in situ high temperature between transition temperature and elastic
camera attached to a X-ray diffractometer. The constant.
experiment has been performed within the
0
temperature range of 30-700 C. Two-step of 021 TALUKDER, M.R. (Dept. of Applied
0
ordering at 520 and 250 C has been observed. In Physics and Electronics, University of Rajshahi,
0
the temperature range from 520 - 300 C, complex Rajshahi-6205). A COMPARATIVE STUDY OF
superstructure of pseudotetraagonal type has been N2 AND H2 DISCHARGES PLASMAS BY
identified and that of temperature range 250 - PROBE TECHNIQUE. J. Bang. Acad. Sci., 2006,
0
30 C, face centered tetragonal (fct) structure of 30 (1), 15-27.
periodic one dimensional anti-phase domain (1D-
APD) type has been observed. In the disordered Microwave excited medium pressure nonthermal
0
state of the alloy above 520 C, fcc structure was atmospheric plasmas are produced inside a
observed. Lattice parameter of the disordered alloy rectangular waveguide. Electrostatic probe
a o=3.6856 Å and that of ordered alloy = a o3.6904 technique is used iteratively to characterize plasma
Å, and c 0= 3.6760 Å, where Cola 0, ratio 0.9961 has parameters. Evolutions of electron concentrations
been determined The average value of long-range and temperatures with increasing pressure and
order parameter S was determined as 0.93. It was microwave power have been studied. It is found
also found that out of 1000 Pd sites in ihe crystal, that electron concentration increases linearly with
945 Pd atoms occupied their places and the rest 55 increasing microwave power and pressure for
Pd sites were occupied by Cu atoms in addition to hydrogen plasma, but it decreases for nitrogen
the own sites of Cu atoms. plasma at 20 Torr. Explanations have been offered
for this reduction. Electron temperature increases
020 SALAM, M. A. ; BARUA, B.P. (BCSIR with increasing microwave power due to heating
Laboratories, Chittagong) & UDDIN, M.M. (Dept. by electromagnetic fields, because concentration of
of Physics, Chittagong University, Chittagong). electrons are lower than that of critical
Studies on Transition Temperature of the concentration for 1 and 5 Torr both for hydrogen
Superconducting Materials Related to Elastic and nitrogen plasmas. On the other hand, electron
Constants. Bang. J. Sci. Ind. Res., 2007, 42 (2), temperatures inside the plasma column start to
203-212. decrease from 10 Torr with increasing microwave
power due to the screening of microwaves, because
For a face-centered-cubic structure crystal the electron concentrations exceed the critical
parameters like atomic mass M, atomic number Z, concentration.
lattice spacing are the important factors in the
determination of a many body Hamiltonian H. 022 TALUKDER, M.R. (Dept. of Applied
Instead of using fcc lattice spacing the scientists Physics & Electronic Engineering, University of
can also utilize atomic volume Ω. Using the Rajshahi, Rajshahi). EFFECT OF METASTABLE
superconducting transition temperature expressed ATOMS ON PROBE DIAGNOSTICS IN LOW
(M)
as T c=T c (Z, Ω), a well defined region in PRESSURE HELIUM DISCHARGE PALSMAS.
superconducting elements is possible, T c may also J. Bang. Acad. Sci., 2007, 31 (1), 33-44.
be related to BCS theory through Debye
temperature. This Debye temperature is related to Secondary electrons arc emitted from the metal
elastic constants C 11, C 12 and C 44, atomic weight surface due to the Auger neutralization of ions or
and atomic volume. Also T c for five fcc transitions Auger deexcitation of metastable atoms. Such
5
