Viabilidade técnica na incorporação de Cinza de Casca de Arroz, Lodo de Estação de Tratamento de Água e Cinza de Lenha em Massa Cerâmica para Revestimento

Este trabalho tem como objetivo a análise da viabilidade técnica na incorporação de Cinza de Casca de Arroz (CCA), Lodo de Estação de Tratamento de Água (LETA) e Cinza de Lenha (CL) para massa cerâmica utilizada para cerâmica de revestimento. A metodologia consistiu na análise das propriedades tecnológicas de várias composições. Foram confeccionados corpos-de-prova por prensagem, com composições de 0 a 50% de resíduo e 50 a 100% de argila. A queima foi feita em forno tipo mufla. As propriedades analisadas foram solubilidade e lixiviação (caracterização ambiental), absorção de água e módulo de ruptura a flexão. Como resultados, concluiu-se ser viável a utilização de até 25% dos resíduos nas temperaturas de 1000ºC, 1100ºC e 1150ºC.This paper presents a technical feasibility analysis of the incorporation of Rice Husk Ash (RHA), Sludge from Water Treatment Station (SWTS) and Wood Ash (WA) in clay for the mass used in ceramic coating. The methodology involved analyzing the technological properties of various compositions. Samples were prepared for pressing, with compositions from 0 to 50% waste and 50 to 100% clay. The sintering was carried out in a muffle furnace. The properties studied were: solubility and leaching (environmental characterization), water absorption and rupture strength modulus. It was concluded that the best condition was the use of up to 25% of the residuals at temperatures of 1000 ºC, 1100 ºC and 1150 ºC

Mechanical behavior and durability of mortars with quartzite and Portland cement after sulfate attack

The residues of ornamental rocks, especially quartzite, cause great environmental impact. More impulse hasbeen given to research on the recycling of these residues over the last years, particularly for use as aggregatesin concrete and mortar. Nevertheless, the studies conducted so far do not mention the behavior of the mortarblended with aggregates coming from residues of ornamental rocks when under chemical attacks in sulfaterichenvironment. Thus, in the present study it was sought to add quartzite residues to the mortar, verifyingits mechanical behavior and its durability when attacked by sodium sulfate (Na2SO4). The durability of themortar blended with quartzite residues under sulfate attack was evaluated by the dimensional variation of thetest specimens when immersed in sodium sulfate solution, according to the methodology of the NBR 13583standard. Were used the following complementary techniques: simple compressive strength, X-ray diffractionand thermogravimetric and differential analysis. From the tests, it was verified that the mortars, afterattack of sodium sulfate, presented dimensional expansions superior to 0.06%, as well as increased mechanicalstrength. Therefore, although it was found that the specimens incorporated with quartzite residues wereattacked by sulfate, it was observed that it was not able to form sufficient secondary ettringite to mechanicallydamage the specimens submitted to the sodium sulfate attack.Keywords: Alternative materials, quartzite residue, sulfates, durability

Influência de diferentes solventes na síntese de mulita por sol-gel

Mulita é um material que tem recebido atenção especial devido às suas propriedades químicas, físicas e mecânicas, que estão correlacionadas com o método de síntese utilizado. O método sol-gel destaca-se frente aos outros métodos químicos devido à possibilidade de obtenção de materiais com elevado grau de pureza e baixas temperaturas de síntese. Sendo assim, este trabalho teve por objetivo a análise dos solventes água, álcool etílico, álcool isopropílico e tetrahidrofurano, na obtenção de mulita por meio da rota sol-gel. As amostras foram caracterizadas por difração de raios X (DRX), análise termogravimétrica e diferencial (TG/ATD), adsorção de nitrogênio, microscopia eletrônica de varredura (MEV) e microscopia eletrônica de transmissão (MET). Os resultados mostraram que a mulita foi sintetizada com todos os solventes, porém, o uso dos álcoois como solvente proporcionou a obtenção das amostras mais cristalinas, com as menores perdas de massa, com uma morfologia formada por agregados e partículas individualizadas.Palavras-chave: Síntese. Sol-gel.  Mulita.  Solventes.

Tailoring the Hybrid Magnetron Sputtering Process (HiPIMS and dcMS) to Manufacture Ceramic Multilayers: Powering Conditions, Target Materials, and Base Layers

The mechanical and wear behavior of CrN/CrAlN multilayers were improved by tailoring the experimental conditions of a hybrid magnetron sputtering process based on a high-power impulse (HiPIMS) and two direct current magnetron sputtering (dcMS) power supplies. To this end, the influence of the base layer and of the combination of Cr and CrAl targets, which were switched to the dcMS and HiPIMS power supplies in different configurations, were investigated with respect to the growth of ceramic CrN/CrAlN multilayers onto commercial gas-nitrided diesel piston rings. The microstructure, grain morphology, and mechanical properties were evaluated by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and instrumented nanoindentation. Bench wear tests simulating the operation of a combustion engine were conducted against a gray cast iron cylinder liner under reciprocating conditions using 0W20 oil as a lubricating agent enriched with Al$_{2}$O$_{3}$ particles. The results revealed a significant increase in hardness, resistance to plastic strain, and wear resistance when two CrAl targets were switched to a HiPIMS and a dcMS power supply, and a Cr target was powered by another dcMS power supply. The compressive coating stresses were slightly reduced due to the soft Cr base layer that enabled stress relief within the multilayer. The proposed concept of hybrid magnetron sputtering outperformed the commercial PVD coatings of CrN for diesel piston rings manufactured by cathodic arc evaporation

Effects of Processing Variables on the Morphology and Microstructural Characteristics of TiO2 Fibers Produced by Solution Blow Spinning

A factorial design was used to evaluate the effects of processing variables on the morphology and microstructural characteristics of titanium dioxide (TiO2) fibers produced by solution blow spinning (SBS). For this, tests were carried out varying TiO2 precursor content, feed rate, air pressure, polymer, and solvent. The TTIP concentration and feed rate statistically influenced the average diameters of the PVC/TiO2 system. The proper combination between polymer and solvent enables the obtaining of TiO2 nanofibers with similar morphologies either using hydrophilic or hydrophobic polymer, however, fiber diameter is influenced by type of system (polymer/solvent) used. Only the anatase crystalline phase was found in the fibers with the PVC polymer and THF solvent, while two crystalline phases were obtained in the fibers with PVP and alcohol, anatase and rutile, indicating that the variation of the polymer and solvent influences the crystalline phases of the TiO2 fibers studied