Local Atomic Arrangements and Band Structure of Boron Carbide.
Boron carbide, the simple chemical combination of boron and carbon, is one of the best-known binary ceramic materials. Despite that, a coherent description of its crystal structure and physical properties resembles one of the most challenging problems in materials science. By combining ab initio computational studies, precise crystal structure determination from diffraction experiments, and state-of-the-art high-resolution transmission electron microscopy imaging, this concerted investigation reveals hitherto unknown local structure modifications together with the known structural alterations. The mixture of different local atomic arrangements within the real crystal structure reduces the electron deficiency of the pristine structure CBC+B12 , answering the question about electron precise character of boron carbide and introducing new electronic states within the band gap, which allow a better understanding of physical properties.
The origin of the n-type behavior in rare earth borocarbide Y1-xB28.5C4.
Synthesis conditions, morphology, and thermoelectric properties of Y1-xB28.5C4 were investigated. Y1-xB28.5C4 is the compound with the lowest metal content in a series of homologous rare earth borocarbonitrides, which have been attracting interest as high temperature thermoelectric materials because they can embody the long-awaited counterpart to boron carbide, one of the few thermoelectric materials with a history of commercialization. It was revealed that the presence of boron carbide inclusions was the origin of the p-type behavior previously observed for Y1-xB28.5C4 in contrast to Y1-xB15.5CN and Y1-xB22C2N. In comparison with that of previous small flux-grown single crystals, a metal-poor composition of YB40C6 (Y0.71B28.5C4) in the synthesis successfully yielded sintered bulk Y1-xB28.5C4 samples apparently free of boron carbide inclusions. "Pure" Y1-xB28.5C4 was found to exhibit the same attractive n-type behavior as the other rare earth borocarbonitrides even though it is the most metal-poor compound among the series. Calculations of the electronic structure were carried out for Y1-xB28.5C4 as a representative of the series of homologous compounds and reveal a pseudo gap-like electronic density of states near the Fermi level mainly originating from the covalent borocarbonitride network.
Women and Gender in Islam: Historical Roots of a Modern Debate
PART I: The Pre-Islamic Middle East Chapter 1 Mesopotamia Chapter 2 The Mediterranean Middle East PART II: Founding Discourses Chapter 3 Women and the Rise of Islam Chapter 4 The Transitional Age Chapter 5 Elaboration of the Founding Discourses Chapter 6 Medieval Islam PART III: New Discourses Chapter 7 Social and Intellectual Change Chapter 8 The Discourse of the Veil Chapter 9 The First Feminists Chapter 10 Divergent Voices Chapter 11 The Struggle for the Future Conclusion Notes Index.