Band structure and high pressure study of Rh 3Sc, Rh 3Y and Rh 3La

The electronic structure of the Rhodium based intermetallic compounds (A 3B) such as Rh 3Sc, Rh 3Y and Rh 3La are studied by the Self Consistent Tight Binding Linear Muffin Tin Orbital (TB-LMTO) method. In the present work, an attempt has been made to understand why the compounds namely Rh 3Y and Rh 3La crystallize in hexagonal structure, rather than the cubic structure, where as some of the similar rhodium based A 3B compounds namely Rh 3Ti, Rh 3Zr, Rh 3Hf, Rh 3V, Rh 3Nb, Rh 3Ta and Rh 3Sc are found to stabilize in cubic structure. In this work a prediction has been made about the structural phase transition in Rh 3Y and Rh 3La, from Hexagonal phase to Cubic phase. A report of the lattice constant, bulk moduli, cohesive energy and electronic specific heat coefficient is made and is compared with the available experimental data. Band structure and density of states histograms are also plotted. An electronic topological transition is predicted in Rh 3La, which may lead to the changes in the Fermi surface topology and hence changes the physical properties of Rh 3La. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2006

Fabrication and characterization of porous scaffolds for bone replacements using gum tragacanth

The practice of bone implants is the standard procedure for the treatment of skeletal fissures, or to substitute and re-establish lost bone. A perfect scaffold ought to be made of biomaterials that duplicate the structure and properties of natural bone. However, the production of living tissue constructs that are architecturally, functionally and mechanically comparable to natural bone is the major challenge in the treatment and regeneration of bone tissue in orthopaedics and in dentistry. In this work, we have employed a polymeric replication method to fabricate hydroxyapatite (HAP) scaffolds using gum tragacanth (GT) as a natural binder. GT is a natural gum collected from the dried sap of several species of Middle Eastern legumes of the genus Astragalus, possessing antibacterial and wound healing properties. The synthesized porous HAP scaffolds were analyzed structurally and characterized for their phase purity and mechanical properties. The biocompatibility of the porous HAP scaffold was confirmed by seeding the scaffold with Vero cells, and its bioactivity assessed by immersing the scaffold in simulated body fluid (SBF). Our characterization data showed that the biocompatible porous HAP scaffolds were composed of highly interconnecting pores with compressive strength ranging from 0.036 MPa to 2.954 MPa, comparable to that of spongy bone. These can be prepared in a controlled manner by using an appropriate binder concentration and sintering temperature. These HAP scaffolds have properties consistent with normal bone and should be further developed for potential application in bone implants

The Role of Cellulose in the Formulation of Interconnected Macro and Micoporous Biocompatible Hydroxyapatite Scaffolds

International audienceIn bone tissue engineering, ceramics are widely used as implant material to enhance bone growth formation or as drug release vehicle. In the existing work porous Hydroxyapatite scaffolds were prepared by polymeric replication method using Cellulose as a binding agent. The influence of binder on various sintering temperature were evaluated. The Hydroxyapatite scaffold sintered at 1150°C was characterized for phase purity, structural analysis and porosity measurements. Hence, it is possible to produce Hydroxyapatite scaffolds with highly inter connecting macro and micro pores with an apparent density of 0.944g/cm 3 corresponding to 75% porosity

Band structure and transport studies of half Heusler compound DyPdBi: An efficient thermoelectric material

The discovery of Heusler alloys has revolutionized the research field of intermetallics due to the ease with which one can derive potential candidates for multifunctional applications. During recent years, many half Heusler alloys have been investigated for their thermoelectric properties. The f-electron-based rare-earth ternary half Heusler compound DyPdBi has its f energy levels located close to the Fermi energy level. Other research efforts have emphasized that such materials have good thermoelectric capabilities. We have explored using first principles the electronic band structure of DyPdBi by use of different exchange correlation potentials in the density functional theoretical framework. Transport coefficients that arise in the study of thermoelectric properties of DyPdBi have been calculated and have illustrated its potential as an efficient thermoelectric material. Both the theoretically estimated Seebeck coefficient and the power factor agree well with the available experimental results. Our calculations illustrate that it is essential to include spin–orbit coupling in these models of f-electron half Heusler materials