https://ri.ufs.br/jspui/handle/riufs/2440 2026-04-04T22:45:20Z 2026-04-04T22:45:20Z Silva, Myllena Vieira https://ri.ufs.br/jspui/handle/riufs/24418 2026-01-27T19:32:38Z 2025-08-22T00:00:00Z

Título: Avaliação do duplo ataque ácido em ligas de titânio para uso em implantes dentários Autor(es): Silva, Myllena Vieira Abstract: Double acid etching is a well-established method of surface modification for implants, although there are few studies on its application in newly developed alloys. The topography and surface composition influence the long-term success of dental implants, favoring fixation and osseointegration. Titanium alloys β emerge as an alternative with low modulus of elasticity, high resistance to corrosion and better mechanical properties, in addition to being composed of biocompatible elements, if compared to the most commonly used alloys today, Ti (cp-grade 2) and Ti-6Al-4V. Promising new alloys based on niobium and tin have been researched. In the present research, the influence of the double acid etching process on Ti-xNb-ySn alloys (x= 35 and 42 and y= 0 and 2) only cold-deformed, cold-deformed and aged was studied. The samples were subjected to surface acid attack in two steps of different acids HCl, HNO3 and H2SO4). The surface roughness parameters were quantified by roughness meter, while topography was studied by scanning electron microscopy, and wettability was determined by the sessile drop method. The results revealed that the two-step acid treatment altered the topography, increasing the surface area and consequently the potential for osseointegration. Attack A (HCl and HNO3) was more efficient for alloys with lower niobium content, while attack B (HCl and H2SO4) stood out as the most balanced in terms of roughness, surface energy and topography. Attack D (HCl, HNO3 and H2SO4) proved to be less efficient.

2025-08-22T00:00:00Z Silva, Paulo Roberto Rego https://ri.ufs.br/jspui/handle/riufs/23933 2025-11-26T13:39:06Z 2025-08-29T00:00:00Z

Título: Efeito da microestrutura e temperatura na resistência à corrosão de aços inoxidáveis em fluido a base de iminodiacetato dissódico Autor(es): Silva, Paulo Roberto Rego Abstract: The corrosion of stainless steels in alkaline solutions containing organic complexing agents represents a challenge in various industrial applications. In this thesis, the effect of microstructure and temperature on the corrosion resistance of AISI 316L, 2205, and 430 stainless steels in a medium containing disodium iminodiacetate was evaluated. Electrochemical tests were carried out to investigate the stability of the passive film, complemented by microstructural analyses for phase identification and morphological changes. The results indicate that the duplex stainless steel 2205 exhibits superior behavior, with greater passive film stability even at temperatures of 80 °C and 100 °C. On the other hand, 316L and 430 showed higher susceptibility to localized corrosion and the formation of microcracks and porosity. This study deepens the understanding of the role of microstructure and temperature in corrosion mechanisms and provides relevant information for material selection and mitigation of corrosion in alkaline media.

2025-08-29T00:00:00Z Batista, Joana Sueveny Barbosa https://ri.ufs.br/jspui/handle/riufs/23484 2025-10-14T19:41:24Z

Título: Desenvolvimento e avaliação do desempenho de filme compósito anticorrosivo reforçado de forma sustentável com resíduo de casca de arroz Autor(es): Batista, Joana Sueveny Barbosa Abstract: This study investigated the incorporation of rice husk ash (CCA) ranging from 5 to 40% into a poly(vinyl alcohol) (PVA) matrix for the development of composite films aimed at improving the corrosion resistance of SAE 1020 carbon steel. The results indicated that films with 40% CCA exhibited the best protective performance, with no visible corrosion on the substrate after 72 hours of exposure in a 3.5% NaCl solution. Scanning electron microscopy (SEM), confocal microscopy, and atomic force microscopy (AFM) analyses revealed that films with 40% CCA presented better surface uniformity with two distinct micro-regions. Fourier-transform infrared spectroscopy (FTIR) demonstrated interactions between the PVA matrix and CCA particles, with shifts in the hydroxyl group peak and changes in bands related to particle-polymer matrix interactions. Differential thermal analysis (DTA) and thermogravimetry (TG) showed that CCA is thermally stable, with mass loss associated with free water evaporation and organic compound decomposition. Electrochemical tests confirmed that films with 40% CCA exhibited superior corrosion resistance compared to both pure PVA and uncoated steel substrates. Wettability tests demonstrated a decrease in hydrophilicity as CCA concentration increased, and adhesion tests confirmed excellent adhesion at all tested concentrations. Additionally, the films were able to reduce mass loss by 20.7% compared to the uncoated substrate and by 8.5% compared to PVA without additives after 15 days of exposure, suggesting that PVA-CCA composite films are promising for corrosion protection of metallic substrates.

Nascimento, Elvia Soraya Santos Nascimento https://ri.ufs.br/jspui/handle/riufs/23477 2025-10-14T19:46:09Z 2025-07-17T00:00:00Z

Título: Estudo da influência da incorporação de resíduo de gesso nas características do tijolo solo-cimento Autor(es): Nascimento, Elvia Soraya Santos Nascimento Abstract: This dissertation investigated the use of recycled gypsum waste as a partial replacement for cement in the production of soil-cement composites, focusing on the evaluation of physical-mechanical performance and the environmental feasibility of the proposed solution. The soil used was characterized in terms of particle size distribution, chemical composition, and consistency limits. Portland cement CP V-ARI was selected for its high early strength, suitable for the experimental schedule. Improper disposal of gypsum waste poses a growing environmental concern, particularly due to the potential release of sulfates into soil and water bodies. This study aimed to mitigate such impacts by reusing this waste in soil-cement formulations. The gypsum was dried, ground, and sieved prior to incorporation in varying proportions. The materials were characterized using XRF, XRD, FTIR, and SEM/EDS. Cylindrical specimens were molded with 0%, 10%, 20%, and 40% gypsum replacing cement, and were tested for compressive strength and water absorption after 7 and 28 days of curing. Composites with up to 20% gypsum showed compressive strength of up to 3.87 MPa at 28 days and water absorption below 18%, meeting performance requirements for non-structural applications. In contrast, the 40% gypsum formulation exhibited significant strength reduction and microstructural degradation, with excessive ettringite formation confirmed by XRD and SEM. These findings highlight the need for careful control of gypsum content to ensure composite stability. It is concluded that incorporating up to 20% recycled gypsum is a technically viable, environmentally strategic, and economically feasible solution, capable of converting an environmental liability into a sustainable input for civil construction.

2025-07-17T00:00:00Z