Características microestruturais do diamante carbonado produzido com grafite brasileiro

Abstract

RESUMOCarbonado é a denominação de um diamante policristalino opaco e de cor escura, naturalmente encontrado no Brasil e na República Central Africana. Artificialmente é possível produzir-se um diamante sintético policristalino do tipo carbonado. Devido a sua microestrutura constituída de muitos grãos, este diamante é mais duro e mais tenaz que os comuns. Assim, pode ser usado com vantagens em brocas para perfuração de petróleo e outras ferramentas resistentes à abrasão. O objetivo deste trabalho foi, pela primeira vez, produzir o carbonado no Brasil e apresentar suas características microestruturais. Este carbonado foi sintetizado a altas pressões e temperaturas utilizando grafite brasileiro no setor de Materiais Superduros da UENF. As características avaliadas o colocam como um material compatível para utilização em ferramentas de corte e perfuração.Palavras chaves: Diamante policristalino sintético, carbonado, microestrutura, resistência à abrasão, materiais superduros. Microstructural characteristics of brazilian graphite produced carbonado diamond ABSTRACTCarbonado is the name given to a polycrystalline, opaque and dark color diamond, which is naturally found in Brazil and in the Central Republic of Africa. Artificially, it is possible to produce a carbonado type synthetic polycrystalline diamond. Owing to its microstructure, which is constituted by many grains, this diamond is harder and tougher than the common ones. Therefore, it can be used with advantage in petroleum perforation drill and other wear resistant tools. The objective of this work was, for the first time, to produce a synthetic carbonado in Brazil and to present its microstructural characteristics. This carbonado was synthesized at high pressure and high temperature, using Brazilian graphite, at the sector of Superhard Materials of the State University of the Northern Rio de Janeiro, UENF. The evaluated characteristics indicated that this carbonado is a proper material for cutting and drilling tools.

The Electricity Policy Debate in Brazil’s Economic Epistemic Community: the 1945-1964 Period

“…By then, Brazil lacked a national capital goods industry capable of supplying the equipment and services and the capital markets required for these industries' setup. In the late 19 th and early 20 th centuries, foreign utilities offered a convenient policy solution to the problem due to their sheer financial power and organizational capacities under conditions that were very unfavorable from the domestic point of view (Rangel, 1963). 7 However, as the economic conditions had changed during the 1940s-1950s period, the operation of these ventures under frankly unfavorable 7 See also Branco (1975).…”

“…The only objective bottleneck is the supply of financial resources. This problem can be resolved if Brazilian companies can also have access to more favorable financial-economic conditions and if the country manages to establish a more solid capital market (Rangel, 1963).…”

“…For Rangel (1963), inflation is an institutional fix for capital accumulation and growth in an imperfect developmental setting. In the unique circumstances in which Brazil's capitalism is unleashed, a high rate of labor exploitation prevails, and wages do not increase according to productivity growth.…”

“…Moreover, the issuance of new money generates a new source of revenue for the government, such that there ensues an income transfer of subjects with low consumption propensity to the public sector, whose consumption propensity is more elevated. Nonetheless, Rangel sees with some skepticism the thesis that "inflation is good", for he is worried that the acceleration of inflation reduces inflation's efficiency as a compensating mechanism, rendering inflation a policy tool that must be used with care (Rangel, 1963).…”

“…Accordingly, "widespread inflationary pressures became the inevitable concomitant of modern industrialization" (Hewlett, 1980, p. 90). It is in that vein that Rangel sees inflation arising from the electricity sector fundamentally in a positive light, as electricity tariffs' indexation enabled Brazil's modern cities' construction, systematic electrification, and heavy industry implantation (Rangel, 1963(Rangel, , 1985.…”