PPGCEM https://repositorio.ufpb.br/jspui/handle/tede/440 2026-04-12T22:07:06Z 2026-04-12T22:07:06Z Diniz, Rayane Karoline Melo https://repositorio.ufpb.br/jspui/handle/123456789/37896 2026-04-02T06:07:15Z 2020-12-15T00:00:00Z

Título: Caracterização e estudo do potencial de uso do residuo de gesso para a fabricação de gesso acartonado (drywall) Autor(es): Diniz, Rayane Karoline Melo Orientador: Lima Filho, Marçal Rosas Florentino Abstract: Gypsum is an industrial mineral produced worldwide. It is estimated that the generation of gypsum waste exceeds the amount of 15 million tons, which are dumped in landfills; furthermore, there are many other environmental impacts related to its production, usage and dumping. In view of the growing inclusion and influence of sustainability in the civil industries, the National Environment Council - CONAMA Resolution 307/2002), reclassified the plaster waste to Class B - waste that can be recycled to other destinations. In this way, this work proposes to investigate a new alternative for the reuse of gypsum residues, from the production of a drywall sealing element, without calcination, evaluating physical, mechanical, and microstructural properties. The raw materials used were kraft paper, plaster glue, commercial gypsum, and gypsum waste. The residue was comminuted and processed in a disc mill. The powders were characterized by XRF, XRD and laser granulometer. The XRF revealed the percentage of SO3 and CaO, which have limits determined by the standard. The XRD revealed to us the phases both qualitatively and quantitatively, indicating the quality of the material that resulted in the waste as well as the hydration process. The granulometry helped to determine the water/gypsum ratio for making the boards, which had the following variables: thickness of 9.5 and 15.0 mm, weight of 0 and 70 kg during molding, and curing temperature at 25° C and 50°C. The different boards were analyzed according to their geometric and visual characteristics, surface density, flexural strength, and SEM/EDS. The geometric and visual characteristics exposed the character of shrinkage, which was associated with the appearance of defects and influence on the boards interface. The surface density indicated to us how much the grain size of the gypsum residue (7,98 μm) can influence this characteristic, as well as the flexural strength. In the SEM/EDS analysis, it was observed the interface and its adhesion, the microstructure of the plaster residue resembling that of the commercial plaster, and also indicated the concentration of the components along the boards, mainly sulfur (S) and calcium (Ca), which are the main elements of the composition of plaster and gypsum. All these results indicate the possibility of reusing plaster waste with low energy expenditure. Editor: Universidade Federal da Paraíba Tipo: Dissertação

2020-12-15T00:00:00Z Silva, Thamyscira Herminio Santos da https://repositorio.ufpb.br/jspui/handle/123456789/37811 2026-03-06T06:09:38Z 2022-12-14T00:00:00Z

Título: Produção, caracterização e estudo catalítico de nanofibras cerâmicas produzidas por Solution Blow Spinning, aplicadas como catalisadores heterogêneos a base de níquel nos processos de reforma do metano para produção de hidrogênio Autor(es): Silva, Thamyscira Herminio Santos da Orientador: Macedo, Daniel Araújo de Abstract: The production of hydrogen and synthesis gas through catalytic methane reforming processes was carried out using fibrous catalysts prepared by the Solution Blow Spinning technique. Nickel-based catalyst nanofibers were produced with different types of supports, characterized, and compared with their counterparts prepared by conventional synthesis techniques. The influence of the preparation method was studied under methane reforming reaction conditions, and the experimental results were separated into three chapters, according to the type of support used. The Ni- CeO2 fibrous catalyst produced by SBS showed good catalytic activity and stability of 30 hours in the dry reforming reaction of methane when compared to a conventional catalyst prepared by wet impregnation of the same composition. Characterizations by XRD, SEM, and XPS evidenced that the good performance of the nanofiber catalyst is due to the good metal-support interaction, high thermal stability, and good oxygen mobility associated with the use of CeO2, which prevent the formation of deposits and growth of metal particles. In the second study, Ni/Co-MgAl2O4 bimetallic catalysts prepared by SBS were compared with catalysts of the same composition prepared by thermal decomposition of hydrotalcites synthesized by co-precipitation. The preparation method influenced the performance of the catalysts in both steam reforming and dry methane reforming reactions. The nanofibers presented good surface and reduction properties, and a mixture of oxides with strong interaction that ensured good catalytic performance compared to the other samples, as well as greater resistance to deactivation by deposition of crystalline carbon. Finally, calcium aluminate nanofiber supports were obtained at a lower calcination temperature than supports produced by solid-state reaction. An industrial waste from the shellfish sector was used as a source of CaCO3 for solid-state synthesis, with the aim of adding value to the waste. The supports were wet impregnated to produce nickel-based catalysts for applications in steam reforming of methane. Regardless of the type of support preparation, the catalysts showed methane conversion above 80% and remained stable throughout the 8-hour tests. Thus, based on the results obtained from XRD, SEM, TPR, XPS, N2 adsorption, and thermal analysis characterization tests, the viability of producing ceramic nanofibers prepared by SBS and the positive impact of their use as fibrous catalysts in heterogeneous methane catalysis was verified. When compared to conventional preparation methods under different methane reforming reaction conditions, the nanofibers showed good catalytic activity, high thermal resistance to prevent particle sintering, and little impact of crystalline carbon deposits that could result in catalyst deactivation. Editor: Universidade Federal da Paraíba Tipo: Tese

2022-12-14T00:00:00Z Muniz, Denise Dantas https://repositorio.ufpb.br/jspui/handle/123456789/37657 2026-02-20T06:07:58Z 2020-08-11T00:00:00Z

Título: Compósitos poliméricos reforçados com resíduos de siderurgia e fibra de piaçava Autor(es): Muniz, Denise Dantas Orientador: Barbosa, Normando Perazzo Abstract: Abstract: The natural sources used in the basic productive sectors of the economy, which are extracted in significant volumes, show signs of exhaustion around the world, which leads to the need to develop materials that can perform properties similar to conventional ones and also provide adequate destination for the waste generated. In this way, the use of steelmaking residues, such as electric arc furnace – EAF – dust, as well as the use of leftovers from the production of non-wood forest products such as piassava shavings, are possible alternatives for different sectors of the economy, such as civil construction and agriculture, in the form of co-products for the production of wall coverings in internal and external areas. This thesis aims to analyze the technical and economic feasibility of using these residues, performing the tests of X-Ray Diffratometry, Fourier Transform InfraRed spectroscopy, Scanning Electronic Microscopy, granulometry, bulk density, Dynamic Thermal Analysis, Thermogravimetric Analysis and X-Ray Fluorescence in the residues. For the characterization of the composites, the residues were incorporated in a polymeric matrix of epoxy resin and the Shore hardness tests, Izod impact, 3 point flexion, traction, compression, abrasion, moisture absorption, post- aging test, Ashby‟s analysis method and TEVS – Technical-Economic Viability Study. The results obtained indicate an excellent interface promoted between the residues and the resin, guaranteeing excellent wettability and mouldability of the composite in volumes of complex geometry, but which requires specific conditions to guarantee a lower percentage of pores and, consequently, better material distribution. It is observed that the ideal grain size for working with the resin is less than 200 MESH, so that the stress concentrations in the material can be distributed in a more isotropic way. The percentage of heavy metals in the EAF dust stands out, indicating that its use requires care in the mixing procedure so as not to generate contamination to the user, but that it brings socioenvironmental benefits by removing a class I slag from the environment and applying it in a high-level added value industrial process. The results indicate that the use of fiber particles and EAF dust generate isotropic stress distribution, making it possible to have a considerable energy absorption capacity over the occupied surface area. It was also observed a good resistance to the flammability of the EAF dust when submitted to temperatures above 1000 oC, allowing indicating the material as flame retardant. Another relevant factor is the mechanical properties of hybrid composites, whose mixture of components promoted gains in resistance to abrasion compared to the benchmarks. About the analyzed compositions, each one presented mechanical for the production and commercialization process and the one that had the set with more optimized properties was the 15% piassava reinforced – resistance to abrasion, 3-point push-up, post-aging and compression resistance, whose properties frame them as composites of polymeric type. EAF dust composites also performed well in traction resistance, hardness, impact and water absorption. Economic feasibility analysis was carried out and products for wall and ceiling cladding have been proposed. Detach the production cost, where its cost is close R$ 18.99/piece for simulated planning with 90% efficiency production and safety sale price at R$ 25.70/piece, which leads to a degree of economic sustainability in approximately 19 months, making it a viable product in the technical, environmental and economic aspects. Editor: Universidade Federal da Paraíba Tipo: Tese

2020-08-11T00:00:00Z Ribeiro, Gildo Machado https://repositorio.ufpb.br/jspui/handle/123456789/37525 2026-02-07T06:06:42Z 2025-10-14T00:00:00Z

Título: Avaliação do efeito da adição de b4c nas propriedades estruturais, microdureza e comportamento a corrosão da liga Cu–11,8Al–0,58Be Autor(es): Ribeiro, Gildo Machado Orientador: Oliveira, Danniel Ferreira de Abstract: Shape memory alloys (SMAs) based on the Cu–Al–Be system exhibit promising functional properties; however, they are highly sensitive to grain growth, which promotes intergranular fracture and limits their applicability. This study investigated the influence of boron carbide (B₄C) addition as an inoculant in the Cu–11.8Al–0.58Be alloy, focusing on its effects on microstructure, mechanical properties, and corrosion behavior. Thermodynamic simulations performed using the Pandat software indicated that B₄C promotes the formation of boron- and carbon-rich phases (graphite, B₄C, and AlB₁₂), reducing the fraction of the Bcc matrix phase and increasing microstructural complexity under non-equilibrium solidification conditions. Experimentally, the addition of 0.05 wt.% B₄C acted as an effective grain refiner, producing a more homogeneous equiaxed structure. However, higher additions (≥0.15 wt.%) led to columnar grain growth and reduced structural uniformity. Microhardness measurements showed a decreasing trend with increasing B₄C content, consistent with the Hall–Petch relationship due to grain coarsening. Conversely, electrochemical tests revealed that the addition of 0.10 wt.% B₄C provided the best corrosion resistance, with higher polarization resistance, lower corrosion current density, and a more stable passive film formation. Electrochemical impedance spectroscopy (EIS) analyses confirmed that the ceramic reinforcement significantly affects the capacitive behavior of the metal/electrolyte interface, with the constant phase element (CPE) circuit best fitting the experimental data. In conclusion, controlled addition of small amounts of B₄C improves both the microstructural and corrosion properties of Cu–Al–Be alloys, provided its content remains within moderate levels. These results contribute to the development and optimization of copper-based shape memory alloys with enhanced structural and functional performance for technological applications. Editor: Universidade Federal da Paraíba Tipo: Tese

2025-10-14T00:00:00Z