EM - Escola de Minas

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6

Notícias

A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.

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Filtros

2016 - 201992020 - 202316

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Autor: search.filters.author.Silva, Guilherme Jorge Brigolini

Resultados da Pesquisa

Agora exibindo 1 - 10 de 25
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    Evaluation of the microstructure and micromechanics properties of structural mortars with addition of iron ore tailings.
    (2023) Almada, Bruna Silva; Silva Neto, Gilberto Alves da; Prado, Dyala Fraga do; Aguilar, Maria Teresa Paulino de; Garcia, Dayana Cristina Silva; Silva, Guilherme Jorge Brigolini; Santos, White José dos
    The Interfacial Transition Zone (ITZ) between the cement paste and aggregates is a region of great interest for concretes because it is the composites’ weakest region. ITZ presents a great amount of large calcium hydroxide and ettringite crystals, with the porosity being able to be up to 2.5 greater than that the rest of the paste. The microstructure, and consequently the ITZ, can be improved by mineral addition. These materials fill the pores in the composite, influence the hydration process and densify the matrix. Therefore, mineral additions, such as iron ore tailings (IOT), can modify microstructure of composites. There are few studies on the assessment of IOT heterogeneity on the microstructure and hardness of structural mortar. Thus, the present study analyzes the properties influences of four IOT types on the microstructure, porosity, and thickness of the structural mortars’ Interfacial Transition Zone (ITZ) with IOT addition, by different evaluation methods. The composites were characterized through the Scanning Electron Microscope by backscattered electrons (SEM-BSE), line scan by Energy Dispersive Spectroscopy and nanoindentation. Results presented that IOT improved particle packing and tended to reduce the ITZ. The IOT improved nucleation since it reduces the amount of anhydrous cement particles and increases the amount of calcium hydroxide particles in the cement matrix. The nanoindentation showed that IOT-added matrix presented greater hardness and indentation module. It can be concluded that the IOT heterogeneity may affect microstructural properties and that the methods presented can be good ways to evaluate the parameters.
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    Alkali-activated materials produced using high-calcium, high-carbon biomass ash.
    (2022) Silva, Thiago Henrique; Lara, Luis Felipe dos Santos; Silva, Guilherme Jorge Brigolini; Provis, John Lloyd; Bezerra, Augusto Cesar da Silva
    Eucalyptus ash (EA) was used in this study as a high calcium ash (HCA) precursor for alkali-activated binders. The EA used also has high carbon unburned (High loss on ignition). This type of ash is one of the waste products from biomass-fuelled thermoelectric plants, and annually thousands of tons are discarded as a by-product of the energy generation process in Brasil, but it is rich in unburnt carbon which means that it is challenging to use in cementitious systems. Eucalyptus is a biomass that removes CO2 from the atmosphere by photosynthesis and part of this carbon content remains in the ashes, generating CO2 capture when EA is incorporated in the production of alkali-activated binders. The objective of the present study was to evaluate the properties of the material obtained by the alkali-activation of the high-calcium high-carbon biomass ash to generate a cementitious binder, with different pastes proportions of EA and silica fume (SF), activated by sodium hydroxide. With the different pastes, mortars were produced using standardized sand. The results obtained from the pastes and mortars were satisfactory in several aspects. The mechanical results of the alkali-activated mortars were comparable those of Portland cement mortars. Mortars degraded methylene blue more efficiently in illuminated conditions, even after high adsorption for 24 h in the dark. The content of leached ions in the remaining solutions met potability standards.
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    Effects of glass wool residue recycled admixtures on the properties of portland cement-based composites.
    (2022) Silva, Keoma Defáveri do Carmo e; Cotta, Jéssica Fernandes; Elói, Fernanda Pereira da Fonseca; Carvalho, José Maria Franco de; Peixoto, Ricardo André Fiorotti; Silva, Guilherme Jorge Brigolini
    In this study, the effects of a recycled mineral admixture based on glass wool residue (GWR) in microstructural and mechanical properties of ordinary portland cement (OPC)-based composites are examined. The GWR was dried and milled into a fine powder, whereby it was physicochemically characterized. Physicomechanical tests, quantitative X-ray diffraction, and scanning electron microscope observation were performed in pastes and mortars at 28, 56, and 90 days of age. Moreover, the potential application of the GWR was evaluated by determining the pozzolanic activity and the fiber reinforcement effect. The results showed that the partial replacement of cement by 25% by weight of GWR presented no reductions in flexural strength at 28 and 56 days of curing, whereas the long-term flexural strength increased by 17%. This replacement also increased the long-term compressive strength of the composites—reaching a strength activity index of 1.06. The results also showed that GWR presented some fiber reinforcement effect—depending on the particle size. Promising properties were observed for samples blended with GWR, yielding technical, environmental, and economic benefits.
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    Equisetum hyemale‑derived unprecedented bioactive composite for hard and soft tissues engineering.
    (2022) Silva, Rosangela Maria Ferreira da Costa e; Diniz, Ivana Márcia Alves; Gomes, Natália Aparecida; Silva, Guilherme Jorge Brigolini; Ferreira, José Maria da Fonte; Freitas Filho, Rubens Lucas de; Freitas, Erico Tadeu Fraga; Martins, Darliane Aparecida; Domingues, Rosana Zacarias; Andrade, Ângela Leão
    Although Bioactive Glasses (BGs) have been progressively optimized, their preparation often still involves the use of toxic reagents and high calcination temperatures to remove organic solvents. In the present work, these synthesis related drawbacks were overcome by treating the ashes from the Equisetum hyemale plant in an ethanol/water solution to develop a bioactive composite [glass/ carbon (BG-Carb)]. The BG-Carb was characterized by scanning electron microscopy, and transmission electron microscopy; and its chemical composition was assessed by inductively coupled plasmaoptical emission spectroscopy. Brunauer–Emmett–Teller gas adsorption analysis showed a specifc surface area of 121 m2 ­g−1. The formation of hydroxyapatite (HA) surface layer in vitro was confrmed by Fourier-transform infrared spectroscopy analysis before and after immersion in simulated body fuid (SBF) solution. The Rietveld refnement of the XRD patterns and selected area electron difraction analyses confrmed HA in the sample even before immersing it in SBF solution. However, stronger evidences of the presence of HA were observed after immersion in SBF solution due to the surface mineralization. The BG-Carb samples showed no cytotoxicity on MC3T3-E1 cells and osteodiferentiation capacity similar to the positive control. Altogether, the BG-Carb material data reveals a promising plant waste-based candidate for hard and soft tissue engineering.
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    Characterization of magnetic tailings from phosphate-ore processing in Alto Paranaíba.
    (2023) Silva, Fernando Brandão Rodrigues da; Araújo, Fernando Gabriel da Silva; Krüger, Fernando Leopoldo von; Silva, Guilherme Jorge Brigolini; Batista, Ronaldo Junio Campos; Manhabosco, Taíse Matte
    The characterization studies of tailings from mining are crucial for the development of its reuse processes and the reduction of impacts caused by its conditioning on the earth’s surface. This study characterizes the magnetic tailings from phosphate-rock processing using X-ray diffraction, X-ray fluorescence spectrometry and quantitative electron microscopy techniques. Samples were obtained from the magnetic tailings deposit of a mining company in the Alto Paranaíba region, Minas Gerais. The tailings are mainly composed of hematite/magnetite (74.92%), ilmenite (8.91%), fluorapatite (8.8%), anatase (3.07%), calcite (1.67%), goethite (1.62%), and quartz (1.02%). The particle size of the tailings is smaller than that specified for the production of sinter feed. The hematite/magnetite phase is strongly associated with ilmenite and fluorapatite. New stages of comminution and separation are needed due to the low degree of liberation of these minerals for a possible reuse of the components.
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    Study of mechanical, durability and microstructural properties of cementitious composite with addition of different iron ore tailings from Brazil.
    (2022) Almada, Bruna Silva; Melo, Henrique da Silva Silveira; Duarte, Marlo Souza; Aguilar, Maria Teresa Paulino de; Garcia, Dayana Cristina Silva; Silva, Guilherme Jorge Brigolini; Santos, White José dos
    Brazil is the second-largest global iron ore producer in the world. Consequently, a large volume of iron ore tailings (IOTs) is generated, which is associated with environmental impacts. IOTs present potential to be used as an addition in cementitious compounds, however, few studies assess how the heterogeneity of this waste can limit its utilization as a building material. Thus, the present study aims to assess whether the heterogeneity of IOTs influences mechanical, durability, and microstructural properties when added to the cementitious composite. Four IOTs samples from different origins were collected and added to cementitious composite at 40% addition content. Composites’ mechanical (compressive strength and modulus of elasticity) and durability properties (water absorption, porosity, electrical resistivity, carbonation, and pH pore solution) were correlated to the microstructure of the IOTs. Results showed that the IOTs from different mines exhibited different physical properties and chemical/mineralogical compositions. Moreover, the higher the degree of ore processing, the lower the heterogeneity, iron content, and specific gravity. Although the IOT samples are heterogeneous, this type of tailing can be used as a filler addition in structural mortars. IOT addition tends to improve the mechanical and durability properties. Heterogeneity most significantly influenced the properties in the fresh state, durability, and microstructural properties. The microstructure of the cement matrix tends to be denser in the IOT-added with higher SSA and silica content. Was observed higher-porosity in regions close to the interfacial transition zone in the samples with coarser IOT.
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    Comparison between hydroxyapatite/soapstone and hydroxyapatite/ reduced graphene oxide composite coatings : synthesis and property improvement.
    (2021) Nicomedes, Daniel Nilson Nunes; Mota, Laureana Moreira; Vasconcellos, Rebecca; Medrado, Nathanael Vieira; Oliveira, Michelle de; Alvarenga, Érika Lorena Fonseca Costa de; Juste, Karyne Ramos de Campos; Righi, Ariete; Manhabosco, Sara Matte; Silva, Guilherme Jorge Brigolini; Araújo, Fernando Gabriel da Silva; Oliveira, Alan Barros de; Batista, Ronaldo Junio Campos; Soares, Jaqueline dos Santos; Manhabosco, Taíse Matte
    Economic viability and eco-friendliness are important characteristics that make implants available to the pop- ulation in a sustainable way. In this work, we evaluate the performance of a low-cost, widely available, and eco- friendly material (talc from soapstone) relative to reduced graphene oxide as reinforcement to brittle hy- droxyapatite coatings. We employ a low-cost and straightforward technique, electrodeposition, to deposit the composite coatings on the titanium substrate. Corrosion, wear, and biocompatibility tests indicate that the reduced graphene oxide can be effectively replaced by talc without reducing the mechanical, anticorrosion, and biocompatible composite coatings properties. Our results indicate that talc from soapstone is a promising ma- terial for biomedical applications.
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    Mechanical properties and microstructure of epoxy mortars made with polyethylene and poly(Ethylene Terephthalate) waste.
    (2021) Dębska, Bernardeta; Silva, Guilherme Jorge Brigolini
    The article describes the results of a study to determine the simultaneous effect of polyethy- lene terephthalate waste (PET) and polyethylene (PE) on the strength characteristics and bulk density of epoxy mortars. In these mortars, 9 wt.% of the polymer binder was replaced by glycolysate which was made from PET waste and propylene glycol. Additionally, 0–10 vol.% of the aggregate was substituted with PE agglomerate made from plastic bags waste, respectively. The modification of the composition of epoxy mortar has a special environmental and economic aspect. It also allows to protect natural sources of the aggregate, while reducing the amount of waste and reducing problems arising from the need to store them. The resulting composite has very good strength properties. With the substitution of 9 wt.% of resin and 5 vol.% of sand, a flexural strength of 35.7 MPa and a compressive strength of 101.1 MPa was obtained. The results of the microstructure study of the obtained mortars constitute a significant part of the paper.
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    Kinetic studies of the reduction of limonitic nickel ore by hydrogen.
    (2020) Oliveira, Víctor de Andrade Alvarenga; Lana, Renard de Jesus Taveira; Coelho, Henrique Carvalho da Silva; Silva, Guilherme Jorge Brigolini; Santos, Claudio Gouvea dos
    A sample of limonitic nickel ore was characterized by XRD, SEM-EDS, and ICP-OES techniques. The Rietveld refinement method showed that the main mineral constituent of this sample is goethite (55.8 pct). Thermal analysis experiments were performed and the determination of the goethite content in the sample could be confirmed by the mass loss associated to the dehydroxylation of this mineral at temperature of 150 C. After thermal decomposition, the sample was reduced in a rotary kiln using hydrogen and subsequent characterization showed that for low temperatures (400 C £ T< 800 C), metallic iron could be identified in the solid product of the reaction by XRD technique and reduction of hematite to metallic iron was the main chemical reaction identified at this temperature. In addition to metallic iron, tetrataenite was identified and quantified in the reduced sample at high temperature (T>600 C) and the results suggest that most of the nickel is in this mineral phase. The shrinking core model was used for the kinetic studies of the reduction process and for the reduction of hematite to magnetite at low temperature (T £ 550 C). The slow step was diffusion of reagent (H2) or product (H2O) through the reduced solid product layer on the particle surface, the apparent activation energy calculated for the reaction was 46.2 kJ. For the reduction of hematite to metallic iron at high temperature (T ‡ 550 C), the slow step was the reaction of hydrogen with hematite at the reaction surface of the particle, and the apparent activation energy achieved by the chemical reaction was 29.5 kJ.
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    Hydraulic tiles produced with fine aggregates and pigments reclaimed from iron ore tailings.
    (2021) Fontes, Wanna Carvalho; Carvalho, José Maria Franco de; Silva, Keoma Defáveri do Carmo e; Silva, Guilherme Jorge Brigolini; Segadães, Ana Maria Bastos Costa; Peixoto, Ricardo André Fiorotti
    Confronted with the growing ecological awareness of the consumer market, the construction industry has been seeking strategies to promote a higher insertion of waste in the production chain while contributing to the technological improvement of processes and products, as well as mitigation of social and environmental impacts and, at the same time, conferring intangible value to the product. In this sense, the present work describes how iron ore tailings (IOT) can be used in the production of cement-based (hydraulic) tiles. The physical, chemical, and mineralogical characterizations carried out demonstrated that the IOT benefciation (segregation) process resulted in a high-quality siliceous aggregate and a Fe-rich clay. The latter can be used as a pigment, whose pigmentation and cementing potentials improve with calcination and grinding. Compared to hydraulic tiles prepared with conventional materials, those obtained with the IOT-based materials displayed a pleasing appearance and the expected physical–mechanical performance.