Márcio Roberto da Rocha

Study of Adsorption Kinetics of Heavy Metals in Acid Drainage from Coal Mining in Type A Zeolites

The present work studied the adsorption of ions of iron and manganese of the effluent from coal acid mine drainage (AMD), located in South of the Santa Catarina using for this purpose type 4A zeolite. Were tested the Langmuir adsorption isothermal model. Tests of adsorption of heavy metals were performed by varying the adsorption time and the ratio of the volume of effluent and the amount of adsorbent. The results showed the efficiency of kinetic adsorption of iron and manganese ions by the zeolite.

Influence of High Energy Milling on the Airflow Sensorproperty of the NBCa Ceramic

Some materials have been applied in many surrounding conditions as sensors, electronic devices and other applications. Inexpensive and reliable temperature and flow measurement are important in many applications including, for example, environmental monitoring and control, indoor air conditioning, weather forecasting, automotive and aerospace systems. Special ceramics are an example of such materials. Neodymium-Barium-Copper is a special ceramic that has high electrical conductivity and airflow sensor characteristics. This property is influenced by high energy milling of the powder, when it is not sintered. To evaluate the influence of this type of milling it was carried out an analysis of particle size as a function of milling time. SEM images and granulometric analysis showed significant reduction of particle size with the increase of milling time. For longer times of milling the mixture of precursor powders is favored, resulting in better homogeneity of the ceramic. This is reflected in the properties of airflow sensor.

Evaluation of the Accelerated Degradation of Mortar in a Ceramic Coating Facade System

In Brazil, ceramic plates are widely used in the construction industry for both small and large constructions in view of their advantages compared with other coating systems [1]. These advantages include ease of maintenance, durability, impermeability, and ease of cleaning. Despite these favorable characteristics, problems occur due to aging of a building. The most common of these problems is the loss of adhesion of ceramic tiles with facades [2]. It is commonly observed that after a few years of use the plates begin to loosen, thereby endangering individuals and properties.

Effect of sensitization on tribological behavior of AISI 304 austenitic stainless steel

Abstract This paper aims to evaluate the dry sliding wear of AISI 304 austenitic stainless steel as a function of the applied load. Samples of AISI 304 were heat treated (sensitized) to precipitate Cr23C6 carbides in the grain boundaries, and the resulting microstructure was compared to that of the non-sensitized samples. Wear testing was carried out at room temperature of 25°C and a relative humidity of about 60% using a pin-on-disk apparatus. The load applied was varied from 10 to 30 N at a constant sliding velocity of 0.5 m s–1. Wear particles were analyzed by means of scanning electron microscopy and X-ray diffraction. The results showed that the dynamic friction coefficient remained effectively constant with increasing applied load. The surface hardness measured after the wear process generally increased at higher loads due to subsurface strain-hardening, and deformation-induced martensitic transformation occurred during the wear process. Surface roughness and weight losses were found to increase with increasing the load for both sensitized and non-sensitized samples. In addition, a great amount of Cr23C6 carbides in the grain boundaries favored a size reduction of the debris generated due to wear.

Evaluation of Behavior of Aluminium-CNT Composite on the Equal-Channel Angular Extrusion

Metal matrix composites (MMCs) are relatively new materials on science and materials engineering. In this work was used single-walled carbon nanotube (SWNT) as reinforcement in an aluminum matrix. For this purpose, 0.75% (by weight) of SWNT was dispersed with isopropanol using ultrasonication and mixed with particles of aluminum powder. The samples with and without SWNT were dried and compacted at room temperature with a pressure of 400 MPa for obtain a billet with 4,8x4,8x25,0 mm3. These compacted billet were subjected to Equal-Channel Angular Extrusion - ECAE (Φ=90 °) at room temperature. The influence of the presence of SWNT, of the number of extrusion passes (0, 1, and 3 passes), of the extrusion route (A or BC) and of the use of back pressure (0-65 MPa) in densification and hardness of the composite was evaluated. Optical microscopy was used to characterize the morphology of the aluminum grains, the dispersion of SWCNT and present pores in the samples. The results indicated that the density and hardness of the samples are increased with the increase in the number of extrusion passes and the use of back pressure. The microstructures showed alignment of the aluminum grains and of the CNT clusters in a direction close to the shear imposed by the ECAE process and increase of the dispersion because of the necking and defragmentation of the CNT clusters.

Evaluation of the thermal performance of different cold materials for urban paving

The phenomenon of the warming of cities at high temperature levels, the so-called “heat island”, has been studied around the world. Apart from generating thermal discomfort, this urban phenomenon has been causing an increase in the demand for energy for cooling the environments. In response to the environmental impact generated by this phenomenon, researchers from different nations have developed techniques for warming mitigation, developing new materials, technologies, and constructive systems. In this context, urban paving is responsible for a significant contribution to the occurrence of heat islands in cities. The use of pavements called “cold materials”, which help to lower the surface temperature, constitutes an important solution to mitigate the effects of the heat flow in cities and the planet. Thus, the purpose of this study was to develop, test and evaluate new cold materials for use in paving. Such cold materials proved to present better thermal performance than conventional ones, such as asphalt and reference concrete (commercial paver). In fact, this work showed that the composition with 90% concrete+10% talc can be considered cold material, with energy savings of up to 16% in comparison to asphalt.

Thermal Characterization of Neodymium-Barium-Copper Ceramic (NBCo Ceramic) Synthesized from Barium Carbonate

This work presents a study about thermal properties of a ceramic material based on NdBaCu system sintered with barium carbonate. These specialized ceramics are manufactured under special conditions and due to its unique electrical and thermal properties are frequently used by the electronic industry. Ceramics containing neodymium-barium-copper (NdBaCu) exhibit high conductivity at low temperatures. In this work, the ceramic samples were sintered with different percentage of barium carbonate, cupric and neodymium oxide and were characterized with Termogravimetric Analysis (TGA), Differential Scanning Calorimetric (DSC), Thermal Dilatometric Analysis (TDA) and X-Ray Diffraction Analysis (DRX). The results showed that the electrical conductivity of NdBaCu system is dependent on the calcination temperature. In turn, the complete calcination is dependent on the barium percentage and the thermal treatment conditions.

Synthesis of 4A-Zeolite for Adsorption of CO2

The gas separation is a very expensive step in the chemical industry and unquestionable relevance. In this work, was verified the efficiency of the use of type A-zeolites in the separation of CO2 in a gas mixture containing 25% CO2, 4% O2 and 71% N2. These concentrations are similar to the effluent gases from combustion processes. To this end, was synthesized type A-zeolites using commercial kaolin and mounted to an adsorption column to test the effectiveness of zeolites in the adsorption of CO2. The synthesized zeolites had surface area equal to 66.22 m2/g. The CO2 concentration was determined by gas chromatography with TCD detector. After adjusting the data to the Langmuir model, it was obtained the kinetic parameters of adsorption. Based on these parameters was found the ability of the zeolite to adsorb CO2, using a column of 0.461285 mg/g. The adsorption results have proved promising and showed maximum adsorption of 78.4% after a time of 10 seconds.

Adsorption of iron and manganese from acid mine drainage using 4A-zeolite synthesised from waste with high kaolin concentrations

This research analysed the behaviour of heavy metals adsorption by zeolites and their associated applicability for treating acid mine drainage (AMD). The type 4A zeolite used was synthesised by a hydrothermal reaction using kaolin derived from the waste pulping process of white paper. For the development of kinetic studies of adsorption, samples were collected from AMD that were located in the southern State of Santa Catarina, Brazil. The optimal conditions for the removal of iron and manganese have been investigated by testing the adsorption, varying both the mass of zeolites used and adsorption times for a quantity of 1 litre of AMD. Adsorption studies have shown that in the first 15 minutes, approximately 80% of Fe was adsorbed. The adsorption of Mn was also efficient. Kinetic parameters were determined by the Langmuir isotherm, which allowed for the calculation of the theoretical adsorption of metals as a function of time.

Evaluation of Changes in Microstructural Coatings Deposited by Thermal Spray

In this work, microstructural changes in coatings deposited by hypersonic thermal spraying technique (HVOF) were subjected to adhesive wear tests. Materials subjected to wear lose efficiency, increase costs and direct or indirect way can stop large production systems. The mechanisms involved in this type of wear can be minimized by the microstructural changes that in many cases reduces or stops the loss of material. To perform this assessment coatings compounds of Cr3C225 (80 Ni-20 Cr) e Al2O3.TiO2 (87-13) investigated had similar hardness values (1000 HV) and chemical characteristics. Were subjected to the ASTM G99 using commercial hard metal pin 2 mm, load 50N force and tangential velocity of 0.5 m/s. Worn surfaces and debris were analyzed by optical microscopy, scanning electron microscope and mass loss. The results show high resistance sprayed coatings worn surfaces and debris were fragile nature with little loss of material during the tests.