Estudo da utilização de ferramentas a base de nitreto de silício (Si3N4) e alumina (Al2O3) na usinagem do ferro fundido vermicular

Machining is one of the most commonly manufacturing processes used in the modern world, consuming millions of dollars annually. Because of this, it is crucial for the automotive industry to reduce costs on their heat-resistant alloy machining processes, such as compacted graphite iron (CGI), which has shown an increasing trend of its application in diesel engine blocks, brakes disks, among other applications, due to its superior mechanical properties to gray cast iron. Despite this advantage, its use is still limited due to its difficulty of machining, moreover, cutting tools are displayed as the main factor in increasing the machining cost. Seeking an alternative to a better machinability of CGI, this paper aims to study two types of ceramic tools developed in Brazil, and benchmark their performance by dry turning. For this, were used CGI class 450 and two tools: ceramic of silicon nitride (Si3N4) and alumina-based (Al2O3), with a cutting speed (Vc) of 300, 400 and 500 m / min; feed (f) of 0.2 mm / rev and depth of cut (ap) of 0.5 mm, using three replicates and starting with new cutting edges. The results showed that the Al2O3 tool had the best performance in Vc of 500 m / min, while the Si3N4 tool had the best results in Vc of 300 m / min. This can be explained by the tool of Si3N4 based include soft intergranular phase, called amorphous, while alumina has higher abrasion resistance due to its high refractoriness. The results make it clear that the tools have significant potential for machining of compacted graphite iron, being necessary a strict control of the cutting parameters used

Desenvolvimento de sensores de gás a partir de óxido semicondutor nanoestruturado

The present work aims to study one-dimensional nanomaterials semiconductors grown via by phase systems Grande oxides Technological Interest for applications in gas sensors. The Used material was tin oxide (SnO2) for their functional properties, and the grow method was the Polymeric Precursors. The films grown were the nanomaterials about substrates of alumina, deposited via spin coating technique, followed by heat treatment at 300C for 1 hour and 650C for 2 hours. Later the films of Performance sensors (sensitivity, speed response, selectivity, and stability) will be in avaliated in a hermetic chamber with controlled atmosphere and temperature. The synthesized materials were its structural and morphological properties characterized in atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (not have this result with Me). We sought to investigate one influence of different conditions for obtaining films (Variation Layers number) in structural and microstructural properties of semiconductors oxides. The synthesis method proved very effective, generating films with micro definitely, uniformity of the nanoparticles and hum high level of porosity, what makes the material of a viable final paragraph applicability

Aplicação de carbono vítreo monolítico para produção de eletrodos a partir da resina furfurílica com diferentes variações de pH

Nowadays, we live in a time of rapid research for technological advances, in a way that this pursuit of new technologies is deeply connected to the diversity of new materials that have been developed by mankind. It deals with issues such as materials with enhanced properties which offer better quality, less cost and high performance, while they are accessible both in their production and moment of operation. In this context, it was required to develop electrodes that were easy to prepare as well as which present high electric conductivity and good mechanic proprieties by using carbonaceous material as basis. For this reason, the best parameters of the furfuryl resin cures were established with different pH variations through viscosimetric measurements and differential scanning calorimetry. By scanning electron microscopy (SEM) was possible to identify an increased porosity in the samples with pH 7 and pH 8, as compared to samples with lower pH content. After carbonization of the material, the characterization of monolithic glassy carbon was held by means of FT-IR techniques, Raman spectroscopy, X-ray diffraction and cyclic voltammetry. The spectra showed that the change in pH does not have significant influence on the crystallographic ordering of the material and its structural characteristics. As for the electrochemical character, the CVM electrodes showed excellent response, with good reversibility and wide potential window. Some voltammetric curve deviations were only observed for the sample with pH 4, which may be related to processing parameters adopted