Otavio Gomes

• Doctor in Materials Engineering and Metallurgy
• Senior Technological Researcher at Centro de Tecnologia Mineral

In the mining industry, mineral characterization provides data and parameters to support efficient and profitable ore processing. However, mineral characterization techniques usually require extensive image analysis, making manual large-scale image segmentation of mineral phases impractical. Considering the accuracy level currently achieved with de...

Aggregate particles within an asphalt mixture are coated in a thin film of binder. Several studies and even mix design procedures have been based on an implied correlation between the binder film thickness (BFT) and the mechanical properties of these mixtures. Those studies generally define the BFT based on a predictive equation linked to one or mo...

The use of fabric in reinforcing cement-based materials expands their applications for various types of construction elements. Additionally, employing renewable sources of plant-based fabrics contributes to reducing the environmental impact of the construction industry. However, the variability in the properties of plant fibers and fabrics necessit...

This work focuses on the characterization of five palygorskite clays from the Brazilian state of Piaui and their feasibility as eco-friendly adsorbents for the removal of Fe3+ ions from aqueous solutions. For characterization, we applied the techniques of X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy with energy di...

This work focuses on the characterization of five palygorskite clays from the Brazilian state of Piaui and their feasibility as eco-friendly adsorbents for the removal of Fe³⁺ ions from aqueous solutions. For characterization, we applied the techniques of X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy with energy di...

This study provides a microanalytical characterization of pigment fragments from the painting “Allegory to the Arts” and two portraits, “Rubens” and “Tintoretto,” by Léon Pallière. The fragments were surface-analyzed using several near-surface methods to acquire information on the materials and determine the painting techniques utilized before the...

The growing global energy demand requires solutions that improve energy efficiency in all sectors. The civil construction sector is responsible for a large part of global energy consumption. In this context, phase change materials (PCMs) can be incorporated into construction materials to improve the energy efficiency of buildings. The purpose of th...

The main objective of this research was to investigate and discuss the interaction between Eucalyptus sp. cellulose nanofibrils (CNFs) and carboxylated styrene–butadiene rubber (XSBR) to produce composite films with higher deformation capacity. The studied films were evaluated through mechanical, morphological, chemical, and physical analysis. The...

The present work presents a low-cost functional prototype of a device for the automation and digital control of the cathodoluminescence stage, originally manual, installed on an optical microscope. The developed device consists of a mechatronic interface externally coupled to the stage to digitally control its movements. Through commands given by a...

Quantitative morphological analysis of juvenile pyroclasts is commonly used to understand fragmentation mechanisms and eruptive styles. Pyroclast morphology has been chiefly studied on conventional tholeiitic and calc-alkaline suites, while the relationship is more poorly constrained for alkaline melt compositions. Here, we analyze the shape of hig...

This paper evaluates in the short- and long-term the healing products in cementitious systems with a crystalline admixture (CA) healing stimulator and polypropylene (PP) fibers in a thermal-activated environment at 60 ºC. For this purpose, multiple microstructural characterization techniques were employed. Calorimetry tests were performed for up to...

The fine aggregate matrix (FAM) is an important constituent of an asphalt concrete mixture; the FAM is where some key damage phenomena such as cracking start and propagate. The proper design and fabrication of isolated FAM testing samples that are representative of the material existing within asphalt concrete mixtures requires the objective determ...

Inspired by the recent success of deep learning techniques in image interpretation, this work presents a pixel-wise semantic segmentation method for the discrimination of opaque and non-opaque minerals from epoxy resin in reflected light microscopy images, a challenging and classical problem of ore characterization. It evaluates a particular Fully...

This work presents an experimental investigation focused on the mechanical properties of a Textile Reinforced Concrete fabricated with bi-directional sisal fabrics treated with three different procedures. The treatments consisted of immersion in a suspension of nano-silica, mechanical peeling and mechanical peeling followed by immersion in a suspen...

This dataset is composed of 81 pairs of correlated images. Each pair contains one image of an iron ore sample acquired through reflected light microscopy (RGB, 24-bit), and the corresponding binary reference image (8-bit), in which the pixels are labeled as belonging to one of two classes: ore (0) or embedding resin (255). The sample came from an...

This dataset is composed of 121 pairs of correlated images. Each pair contains one image of a copper ore sample acquired through reflected light microscopy (RGB, 24-bit), and the corresponding binary reference image (8-bit), in which the pixels are labeled as belonging to one of two classes: ore (0) or embedding resin (255). The sample came from a...

Maghemite (γ-Fe2O3) is a mineral formed from magnetite oxidation at low temperatures, an intermediate metastable term of the magnetite to hematite oxidation and could be mixed with both. It has magnetic susceptibility similar to magnetite, crystal structure close to magnetite with which it forms a solid solution, while compositionally it equals hem...

This work presents an overview of the most relevant studies developed to understand the enhancement promoted by the double effect of the crystalline admixtures (CAs), both as permeability-reducers and as self-healing stimulators in cement-based materials. Thus, an in-depth investigation was carried out of the main mechanisms of CAs disclosed in the...

Maghemite (γ-Fe2O3) is a mineral formed from magnetite oxidation at low temperatures, an intermediate metastable term of the magnetite to hematite oxidation and could be mixed with both. It has magnetic susceptibility similar to magnetite, crystal structure close to magnetite with which it forms a solid solution, while compositionally it equals hem...

The present work evaluates the effect of pyraclostrobin fungicide on the nutritional quality of mulberry leaves, silkworm cocoon production and silk fiber mechanical performance. The evaluation was performed in two consecutive years. In spring 2015, mulberry plants were treated twice with 4 doses of pyraclostrobin (0, 100, 200, and 300 g.ha-1), 30...

O presente trabalho desenvolveu uma solução, utilizando Hadoop e Map Reduce for C (MR4C), capaz de paralelizar a segmentação de fissuras em imagens de partículas minerais. Um conjunto de 221 imagens de tamanhos distintos de partículas de minério de cobre obtidas por microscopia eletrônica de varredura foi utilizado para os testes. A variação do núm...

A maghemita é um mineral formado a partir da oxidação da magnetita em baixas temperaturas, um composto intermediário da oxidação magnetita-hematita. A maghemita pode ser erroneamente identificada como magnetita por difração de raios X e/ou como hematita por análise química pontual em MEV. No entanto, a magnetita não-estequiométrica foi detectada e...

Crystalline admixtures (CAs), categorized as permeability-reducing admixtures, are commercial products employed in low contents in cement-based materials either to improve concrete durability or to stimulate autogenous healing of cracks. This study investigated the effects on crystal formation promoted by CA presence in cementitious pastes by therm...

The influence of elevated temperatures on mechanical behavior was studied for curaua, hemp, and sisal natural fibers. Tensile tests were performed on fibers heated at 100 °C, 150 °C, and 200 °C for 24 h, and reference samples were maintained without thermal treatment for comparisons. The cross sectional area of the fibers was measured using a scann...

The effect of elevated temperatures on a calcium aluminate mortar with clinker aggregates is the subject of this paper. After an exposure period of 3 h at temperatures ranging from 25 to 1000 °C, specimens were tested in residual conditions in order to evaluate changes on the mechanical and microstructural properties. A simplified hydration model b...

Image analysis aiming at process design or control might be based on several types of microscopy, each providing advantages and limitations. Automated mineralogy systems based on SEM are dominant for ore characterization, but there are relevant cases where such systems cannot perform the required characterization, as iron ores and complex multi-met...

In this paper we present the early results of the self-healing analysis of an oil well cement slurry containing 1% by weight of cement of crystalline admixture. The specimens cured in a bath at 60°C were pre-cracked at 7 days by splitting test until crack width of 200 µm. The healing process lasted 66 days in a 60°C water bath to reproduce pre-salt...

The carbonate reservoir rocks of Brazilian pre-salt are characterized by the dominance of stromatolitic limestones, grainstones and microbial laminites with simple mineralogy and a huge heterogeneity of pore systems. This systems can be extremely complex, depending on the desposition textures of the rocks, whitch is later modified by diagnetic proc...

Curso teórico-prático "Processamento de imagem digital com FIJI/ImageJ" ministrado no dia 24/08/2018, no Workshop em Microscopia Eletrônica e por Sonda, do Centro de Microscopia da UFMG. https://sites.google.com/view/workshopmicroscopia/

The influence of different temperatures on the chemical and mechanical behavior of three types of refractory concretes is studied. These materials were formulated using cements and alumina aggregates of different qualities. The alumina content considered is 51, 71 and 90 wt.%. The methodology implemented included: X-ray diffraction (XRD), thermogra...

This paper presents an automatic system for mineralogical and textural characterization of iron ores based on digital microscopy and image analysis. It employs a motorized and computer-controlled reflected light microscope in a correlative approach that combines bright field and circular polarization modes. Mosaic images covering large areas of pol...

A correlative approach employing optical microscopy and scanning electron microscopy is proposed for the quantification of phases and pores in iron ore pellets. Combining mosaic images covering the full cross-sections of pellets, obtained with both techniques, it is possible to improve the discrimination of pores, quartz and silicates. First, the i...

This paper presents an experimental investigation on the applicability of the Barcelona (BCN) test to evaluate the mechanical properties of a macro-synthetic fiber reinforced concrete (MSFRC) submitted to high temperature environments (up to 600 °C). BCN tests demonstrated that the MSFRC gradually loses tensile strength an energy consumption densit...

Water contaminated by oil poses challenges to the management of water resources. Magnetic nanoparticles has been issue of different potential applications including remotion oil from water. Magnetic polystyrene–palygorskite nanocomposites were prepared by a heterogeneous phase polymerization for the removal of organic contaminants from water. The o...

Ore characterization comprises a set of methods, from beneficiation operations to instrumental analysis, employed to study ores in order to evaluate possible products and routes for processing. Among these methods, ore microscopy plays an essential role as there are important ore characteristics, such as mineral assemblage, its associations, textur...

Resumo Na formulação e preparo de pastas cimentícias destinadas ao revestimento de poços de petróleo é imperativo que seja levado em conta o conjunto de condições associadas ao ambiente da prospecção. Este estudo experimental tem por objetivo investigar a interação entre halita e pasta cimentícia, no âmbito da exploração das reservas do pré-sal bra...

Phosphorus in iron ores is considered as a deleterious component to iron making reflecting in cold shortness of the produced steel. The present study investigates the phosphorus migration pattern resulting from thermal treatment of an oolitic-type iron concentrate with and without additives. To this end focused mineralogical and microscopic observa...

Biomass ash is a solid waste generated in large quantities in stand-alone boilers for the generation of power and heat. The cocoa industry, which uses cocoa almond bark (20%) and eucalyptus wood (80%) as fuel, generates fly and bottom ash. The fact that the properties of the ash are little known limits its correct provision and application. In this...

One of the main steps in the quality control of iron ore involves the analysis of images obtained under the optical microscope (OM). Traditionally, the experienced technician visually distinguishes the main phases, estimating their surface fractions and, in certain cases, crystal or particle sizes and shapes. The main phases present in Brazilian ir...

The most important iron bearing mineral in Brazilian ores, hematite, appears in different textures that are hard to distinguish. Typically, hematite is classified as either Compact (CP) or non-Compact (nCP). CP hematites are polycrystalline, each particle formed of differently shaped crystals. nCP hematites are divided into microcrystalline and Mar...

The current work reports on a new approach for copper bioleaching from Printed Circuit Board (PCB) by moderate thermophiles in a rotating-drum reactor. Initially leaching of PCB was carried out in shake flasks to assess the effects of particle size (-208μm+147μm), ferrous iron concentration (1.25-10.0g/L) and pH (1.5-2.5) on copper leaching using m...

The work in hand presents the results of an experimental investigation on the thermo-mechanical properties of a textile refractory composite reinforced with polymer coated basalt fibers under tensile loading. The composites were produced as a laminate material using basalt bi-directional fabric layers as reinforcement. A high alumina cement matrix...

Pitinga used to be the world's largest cassiterite mine, and still is one of the major tin and tantalum/niobium suppliers. It also hosts the largest reserves for heavy rare earth elements worldwide, with an estimate of over 70 kt of contained Y, and highly above average HREE/Y. The most important HREE carrier is xenotime, but gagarinite-(Y) and...

In this work it was studied the influence of recycled fine aggregate obtained from construction and demolition waste (CDW) on the rheological properties of Portland cement mortars. The CDW was initially separate in their main constituents (mortar, ceramic and concrete debris) at the laboratory and then grinded separately to the sand size in order t...

Heap bioleaching is gaining importance as a low cost technology for processing low grade ores and tailings. Furthermore, it can be employed to process large particles and aggregates. Nevertheless, only grains at the surface are exposed to the leaching solution. The present work aims at investigating the effect of different crushing methods in the g...

Printed circuit boards (PCB) are particularly problematic to recycle because of the heterogeneous mix of organic materials, metals, and glass fiber. PCBs are found in almost every electro-electronic equipment and their recycling process involves a pre-treatment to separate the products which contain targeted metals. In this work, a physical process...

In this work, the adsorption of Fe(III) onto Brazilian palygorskite nanoparticles was investigated and the modifications of the mineral-aqueous solution interface properties were evaluated. We also investigated the influence of the adsorbent concentration and the best contact time for the adsorption to occur. The results showed that an increase in...

An automatic method for the classification of crystals of iron oxides, including the measurement of oxide crystal size and shape, by a digital microscopy procedure involving image acquisition, processing, analysis, and classification is described

A digital microscopy and image analysis routine was developed to automate the process of iron ore sinter characterization by optical microscopy. An image mosaic is captured using a motorized microscope controlled by software in order to cover an entire section of the sinter sample. This mosaic goes through an image processing and analysis routine t...

Brazilian iron ores are composed predominantly by hematite, but they have different textures. Traditionally, in the mining industry, the microstructural characterization of iron ores is manually performed, by analyzing samples under a reflected light microscope to identify mineral and textural phases and estimate their fractions. This procedure is...

In the present work the morphology of natural fibers was correlated with their mechanical properties via image analysis. Jute, sisal, curaua, coir and piassava fibers were tested under direct tension in a universal testing machine and the cross-sectional areas of the fibers were calculated using images obtained in a scanning electron microscopy. Fo...

Policrystalline anisotropic minerals can be classified by the shape and sizes of their crystals. In optical microscopy, circularly polarized light is more effective to create contrast between adjacent crystals than the traditional linear polarization scheme. This allows image processing algorithms to detect crystal edges, and image analysis to meas...

O Theatro Municipal do Rio de Janeiro foi inaugurado em 1909. A construção inclui muitos elementos metálicos, com destaque para uma escultura monumental de Águia que encima o prédio em sua fachada frontal. A partir de 2008, foi iniciado o processo de restauração da edificação, finalizado em 2010. Nesse âmbito, foi realizada uma pesquisa interdiscip...

Brazilian iron ores are predominantly hematitic and may have different textures. In the mining industry, their microstructural characterization is manually performed, by analyzing samples under an optical microscope to identify the hematite phases and estimate their fractions. This procedure is performed few times a day and, hence, susceptible to f...

Esse trabalho tem como objetivo relacionar a morfologia de diferentes fibras naturais com suas propriedades mecânicas. Fibras de juta, sisal, curauá, coco e piaçava foram testadas sob tração direta em uma máquina de ensaios universais. Para cada tipo de fibra foram realizados 15 testes em amostras com comprimento de 40 mm, sob controle de deslocame...

This article proposes a simple methodology for the morphological characterization of sand particles through scanning electron microscopy (SEM) and image analysis. It was tested on comparison of natural sands, and artificial sands composed by construction and demolition waste (CDW) from mortar, ceramic, and concrete.The samples were segregated by a...

The recognition of hematite grains is an intermediate task that aids the texture characterization of iron ores. Hematite is a strongly anisotropic mineral. Thus, the combined use of a polarizer and an analyzer in reflected light microscopy (RLM) can be used to obtain images that present sufficient contrast to differentiate grains. The present work...

Resumo Os resíduos de construção e demolição (RCD) tornaram-se, em todo mundo, um dos principais problemas ambientais das cidades. A classificação e separação das partículas de RCD constituem-se na principal dificuldade para sua reciclagem. O presente trabalho propõe uma metodologia para a classificação morfológica de partículas de areias reciclada...

The recognition of hematite grains is an intermediate task that aids the texture characterization of iron ores. Hematite is a strongly anisotropic mineral. Thus, the combined use of a polarizer and an analyzer in reflected light microscopy (RLM) can be used to obtain images that present sufficient contrast to differentiate grains. The present work...

The identification of hematite grains is an intermediate task that aids the texture characterization of iron ores, a key step in quality control. The present paper proposes an image acquisition and analysis methodology for identifying hematite grains in images obtained with reflected light microscopy (RLM). Two images were then acquired with polari...

A methodology for quantitative microstructural characterization of iron ore sinters is proposed. Sinter samples with ≈3 cm diameter were mounted in resin, ground and polished. For each sample, mosaic images covering the entire sample were acquired (5× objective lens). An automatic image analysis routine was employed to measure the area fraction of...

The identification of hematite grains is an intermediate task that aids the texture characterization of iron ores, a key step in quality control. The present paper proposes a simple methodology for identifying hematite grains in images obtained by reflected light microscopy, with promising results. An automatic image processing routine segments hem...

Construction and demolition waste (CDW) has become one of the most important environmental problems in large and medium-sized cities around the world. The classification and segregation of CDW particles constitute the main difficulties for their recycling. The present paper proposes a methodology for classification of particles from CDW that consis...

Fe _x Cu _{100- x} metastable alloys were prepared by pulsed electrodeposition for 5≪ x ≪85 . The Fe-rich alloys crystallize in the bcc structure of α -Fe and the Fe-poor ones in the fcc structure of Cu. The magnetic properties of the ferromagnetic Fe-rich alloys ( x ≫50) are reminiscent of those observed in Fe–Cu alloys prepar...

A methodology for quantitative microstructural characterization of iron ore sinters was proposed. Sinter samples with ≈3 cm diameter were mounted in resin, ground and polished. For each sample, mosaic images covering the entire sample were acquired (5X objective lens). An automatic image analysis routine was employed to measure the area fraction of...

Vale (previously CVRD – Companhia Vale do Rio Doce) evaluates the microstructure of sinters in order to understand their characteristics and behavior in the agglomeration process, and the correlation with conventional quality parameters. Efforts on image analysis development are in progress between Vale and PUC-Rio in order to improve both the qual...

A new methodology, co-site microscopy, is presented and discussed through a set of case studies, images from the same field, or set of fields, of a sample are acquired with different microscopy techniques, or from the same microscope in diverse contrast modes and/or sample conditions. The obtained data is assembled in a multi-modal database that pr...

Despite progress in Scanning Electron Microscopy (SEM) automatic instruments, these systems are not capable of performing the identification and discrimination of major iron ore minerals (hematite and magnetite). On the other hand, Reflected Light Microscopy (RLM) can easily distinguish these iron oxides by their reflectancies, but it cannot discri...

Vale evaluates the microstructure of iron ore pellets in order to understand their characteristics and behavior in the agglomeration process, and the correlation with conventional quality parameters. Efforts on image analysis development are in progress between Vale and PUC-Rio in order to improve both the qualitative and quantitative characterizat...

Computer-controlled microscopes with digital image acquisition and analysis led to the creation of the new field of digital microscopy. These techniques not only allow a certain degree of automation but have also brought new possibilities to microstructural characterisation. One of these new and promising possibilities is co-site microscopy, which...

The traditional trading of iron ores is based on chemical specifications and particle size distribution. However, recent characterisation studies, that bring additional information like mineralogical composition and microstructural (textural) aspects, have become important. They contribute to determination of the iron ores downstream beneficiation...

Vale (previously CVRD – Companhia Vale do Rio Doce) evaluates the microstructure of sinters in order to understand their characteristics and behaviour in the agglomeration process, and the correlation with conventional quality parameters. Efforts on image analysis development are in progress between Vale and PUC-Rio in order to improve both the qua...

A integração do controle por computador de microscópios com a aquisição e análise digital de imagens levou à criação de uma nova área, denominada Microscopia Digital. Além de permitir um certo grau de automação, a Microscopia Digital abriu possibilidades realmente novas para a caracterização microestrutural. Uma destas novas e promissoras possibili...

The study of automotive catalyst deactivation is associated with technical, economic and environmental problems. The deactivation phenomenon has different origins that can be divided into three groups: thermal, chemical and mechanical deactivation. In this work, nine commercial catalysts were analyzed, seven of them aged in an engine bench. A study...

A method for automatic classification of the shape of graphite particles in cast iron is proposed. In a typical supervised classification procedure, the standard charts from the ISO-945 standard are used as a training and validation population. Several shape and size parameters are described and used as discriminants. A new parameter, the average i...

Automatic Classification of the Shape of Graphite Particles in Cast Iron - Volume 9 Issue S02 - O. F. M. Gomes, S. Paciornik

Dielectric properties of resin/carbon-black nanocomposites were measured and shown to differ from results given by a random sets modeling approach. The origin of the discrepancies was traced back to the presence of sets of carbon planes, detached from the carbon-black particles during the composite preparation. These planes are dispersed in the res...

Using digital image processing and pattern recognition techniques, a supervised classification procedure of bamboo vascular bundles was developed and tested on polished cross sections of bamboo culms from four different species. Results obtained for same species samples were similar and were consistent with visual observations

A presente dissertação consiste no estudo de três casos de caracterização automática de materiais, através do emprego de técnicas de Processamento e Análise Digital de Imagens (PADI). Cada caso envolve uma escala diferente (milimétrica, micrométrica e nanométrica) e apresenta complexidade em um diferente aspecto de PADI. Deste modo, juntos, estes t...