A New process for the enrichment of nickel in Sukinda chromite overburden ore

Chrontite Over Burden (COB) ore from .Sukinda taller, Orissa is too lean in nickel concentration to he exploited for the extraction of nickel. The average nickel concentration in the COB ore lies in the range of 0.4-0.6%. An acid leaching route at atmospheric prsssure has been developed for screening out silica as insoluble. Metal values in the leach liquor are retrieved as hydroxides by appropriate manoeuvring of pH. The metal hydroxides are converted to corresponding oxides by calcining at 900°C. The resultant nickel content in the mixed oxide has been consistent1 ' .found to he 1.6% and above. This product star he directly used as a starting material for the preparation of ferro-nickel

Nanostructuring with Structural-Compositional Dual Heterogeneities Enhances Strength-Ductility Synergy in Eutectic High Entropy Alloy

A lamellar (L12 + B2) AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) was severely deformed by a novel hybrid-rolling process. During hybrid-rolling, the deformation was carried out in two stages, namely cryo-rolling followed by warm-rolling at 600 \ub0C. The strain (ε) imparted in each of these steps was identical ~1.2, resulting in a total strain of ε~2.4 (corresponding to 90% reduction in thickness). The novel processing strategy resulted in an extremely heterogeneous microstructure consisting of retained lamellar and transformed nanocrystalline regions. Each of these regions consisted of different phases having different crystal structures and chemical compositions. The novel structure-composition dual heterogeneous microstructure originated from the stored energy of the cryo-rolling which accelerated transformations during subsequent low temperature warm-rolling. The dual heterogeneous microstructure yielded an unprecedented combination of strength (~2000 MPa) and ductility (~8%). The present study for the first time demonstrated that dual structure-composition heterogeneities can be a novel microstructural design strategy for achieving outstanding strength-ductility combination in multiphase high entropy alloys

A Break in the Highest Energy Cosmic Ray Spectrum: A Signature of New Physics?

Recent experimental data from the Fly's Eye and the Akeno array seem to indicate significant structure in the ultrahigh energy cosmic ray spectrum above 10^{18}\eV. A statistically significant dip has been established at about 5\times10^{18}\eV. In addition, each experiment observed a different superhigh energy event above 10^{20}\eV separated from the rest of the data by about half a decade in energy. In this article we discuss what this implies for the existence or non-existence of the ``Greisen-Zatsepin-Kuz'min cutoff'', a long lasting and still open question in cosmic ray physics. This cutoff, caused by energy losses in the cosmic microwave background, is predicted to occur at a few times 10^{19}\eV if cosmic rays are produced by shock acceleration of lower energy particles at extragalactic distances. We show that from the spectral point of view, sources nearer than a few \Mpc are still consistent with the data at the $1\sigma$ level, provided these sources accelerate particles beyond 3\times10^{20}\eV. However, persistence of the apparent gap in the existing data at the level of a 4 times higher total exposure would rule out a wide range of acceleration models at $98\%$ C.L., whether they rely on nearby or extragalactic sources. This might hint to the existence of a ``top down'' mechanism which produces an additional hard component of ultrahigh energy particles directly, say, by decay from some higher energy scale in contrast to bottom up acceleration of charged particles. In this scenario a cutoff followed by a pronounced spectral flattening and possibly even a gap could naturally be formed.Comment: 12 latex pages, 2 figures added via figures comman

BL Lacertae are probable sources of the observed ultra-high energy cosmic rays

We calculate angular correlation function between ultra-high energy cosmic rays (UHECR) observed by Yakutsk and AGASA experiments, and most powerful BL Lacertae objects. We find significant correlations which correspond to the probability of statistical fluctuation less than $10^{-4}$, including penatly for selecting the subset of brightest BL Lacs. We conclude that some of BL Lacs are sources of the observed UHECR and present a list of most probable candidates.Comment: Replaced with the version accepted for publication in JETP Let

A magnetic model for the incommensurate I phase of spin-Peierls systems

A magnetic model is proposed for describing the incommensurate I phase of spin-Peierls systems. Based on the harmonicity of the lattice distortion, its main ingredient is that the distortion of the lattice adjusts to the average magnetization such that the system is always gapful. The presence of dynamical incommensurabilities in the fluctuation spectra is also predicted. Recent experimental results for CuGeO_3 obtained by NMR, ESR and light scattering absorption are well understood within this model.Comment: 8 pages, 3 figures, Latex with EPL style files all include

Ultra-high energy cosmic rays may come from clustered sources

Clustering of cosmic-ray sources affects the flux observed beyond the cutoff imposed by the cosmic microwave background and may be important in interpreting the AGASA, Fly's Eye, and HiRes data. The standard deviation, sigma, in the predicted number, N, of events above 10^{20} eV is sigma/N = 0.9(r_0/10 Mpc)^{0.9}, where r_0 is the unknown scale length of the correlation function (r_0 = 10 Mpc for field galaxies). Future experiments will allow the determination of r_0 through the detection of anisotropies in arrival directions of ~ 10^{20} eV cosmic-rays over angular scales of Theta ~ r_0/30 Mpc.Comment: Accepted for publication in Astrophysical Journa

A New process for the Enrichment of Nickel in Sukinda Chromite Overburden ore

Chromite Over Burden (COB) ore from Sukinda valley, Orissa is too lean in nickel concentration to be exploited for the extraction of nickel.The average nickel concentration in the COB are lies in the range of 0.4-0.6%. An acid leaching route at atmospheric prsssure has been developed for screening out silica as insoluble. Metal values in the leach liquor are retrieved as hydroxides by appropriate nia manoeuvring of pH. The metal hydroxides are converted to corresponding oxides by calcining at 900°C. The resu-ltant nickel content in the mixed oxide has been consist-ently found to be 1.6% and above. This product may be directly used as a starting material for the preparation of ferro- nickel