Ciência dos materiais é o campo da ciência de caráter interdisciplinar relativo ao estudo das propriedades dos materiais e a relação entre a sua estrutura em escalas atômicas ou moleculares com suas características macroscópicas, incorporando elementos da física e da química como as formas de caracterização e processamento. https://tedebc.ufma.br/jspui/handle/tede/1266 2026-07-14T21:11:00Z 2026-07-14T21:11:00Z FREITAS, Aline Alves de https://tedebc.ufma.br/jspui/handle/tede/7080 2026-07-01T18:08:58Z 2024-06-27T00:00:00Z

Título: ESTUDO DAS PROPRIEDADES MAGNÉTICAS E MAGNETOCALÓRICAS DOS COMPÓSITOS METÁLICOS Dy-Pt-In e Gd-Pt-In Autor: FREITAS, Aline Alves de Primeiro orientador: SILVA, Luzeli Moreira da Abstract: This study presents the synthesis of metallic alloy composites based on Dy-Pt-In and Gd-Pt-In, followed by characterization through X-ray diffraction (XRD), Scanning Electron microscopy (SEM) magnetization, and specific heat measurements. XRD and SEM analysis revealed that the Dy-Pt-In composite consists of DyPtIn, DyPt and DyPt2In phases. Similarly, the Gd-Pt-In composite comprises GdPtIn and GdPt phases. Magnetic properties analysis indicates that both composites exhibit the magnetic transitions corresponding to the crystalline phases present in each material. The Dy composite displays two consecutive ferromagnetic transitions at 32.5 K and 23 K, and an antiferromagnetic transition at 7.5 K, which undergoes a metamagnetic phase transition to the ferromagnetic state upon applying a magnetic field, as demonstrated by specific heat data. Magnetocaloric properties analysis revealed that the three consecutive magnetic transitions extend the magnetocaloric effect (MCE) over a wide temperature range between 2.5 and 57 K for the Dy-Pt-In composite. Although the two ferromagnetic transitions in the Gd-Pt-In composite are relatively close, they are sufficiently broad to promote a significant MCE between 6.0 and 89 K. The maximum values obtained for magnetic entropy change are similar for both composites (6.3 and 6 J/kg. K at ΔH = 50 kOe). However, the relative cooling power is 47% higher in the Gd composite (~327 J/kg) compared to the Dy composite (~221 J/kg). The synthesis and characterization of the metallic composites in this study present promising results for applications in magnetic systems, especially in the context of the magnetocaloric effect. These results highlight the importance of developing composites with magnetic systems, since a material with optimized properties for technological application can be obtained by combining the individual magnetic properties of two or more metallic compounds. Instituição: Universidade Federal do Maranhão Tipo do documento: Dissertação

2024-06-27T00:00:00Z COSTA, Alexandre Saraiva https://tedebc.ufma.br/jspui/handle/tede/7034 2026-06-03T13:24:42Z 2020-09-16T00:00:00Z

Título: Investigação teórica e experimental das propriedades estruturais, eletrônicas e térmicas do cristal de malonato de L-fenilalanina L-fenilalaninium Autor: COSTA, Alexandre Saraiva Primeiro orientador: FAÇANHA FILHO, Pedro de Freitas Abstract: In this work, the structural, electronic and vibrational properties of the crystalline environment of the L-phenylalanine L-phenylalaninium malonate salt were investigated. The synthesis of the compound occurred by the method of slow evaporation of the solvent with a 2: 1 ratio; the pH value measured was 2.61 under ambient conditions of temperature and pressure. The structural characterization by powder X-ray diffraction, combined with the Rietveld refinement method, confirmed that the material crystallized in a monoclinic system with space group P21, containing two molecules per unit cell Z = 2 and with the following network parameters : a = 14.08 Å, b = 5.53 Å, c = 14.65 Å and angle β = 107.39 º. The volume of the unit cell obtained after refinement was 1089.5 Å3 . The structural parameters, lengths and bond angles, analyzed via DFT were described satisfactorily with the LDA exchange and correlation functional. The vibrational properties were analyzed using the density functional theory (DFT) and FTIR and Raman spectroscopy techniques. In addition, to assign the vibrational bands we use the computational approach of calculations with the quantum_ESPRESSO package. Characterizations by thermal analysis Thermogravimetry (TGA), Derivative thermogravimetry (DTG), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC) indicate decomposition of the molecules from 120 ° C and a large endothermic peak around 185 ° C regarding the decomposition of the material, and suggest that the material has five stages of decomposition. The main objective of this work is to investigate the structural and vibrational properties via DFT with those based on the functional B3LYP, B3LYP / PCM and LDA using the quantum-ESPRESSO package. The vibrational study at high temperatures, indicated that the material does not present a phase transition until the melting point, showing only small modifications for smaller wave numbers and a decrease in the relative intensity, showing the decomposition of the NH3 and CO2 groups. Instituição: Universidade Federal do Maranhão Tipo do documento: Dissertação

2020-09-16T00:00:00Z PEREIRA, Andrea Ferraz Silva https://tedebc.ufma.br/jspui/handle/tede/6890 2026-04-08T11:49:09Z 2026-04-02T00:00:00Z

Título: ESTUDO DE VIDROS BOROFOSFATOS DO SISTEMA B₂O₃–P₂O₅– CaF₂–Na₂O MODIFICADOS COM K₂O E Li₂O PARA APLICAÇÕES COMO BIOMATERIAIS REGENERATIVOS: Da síntese aos testes in vitro Autor: PEREIRA, Andrea Ferraz Silva Primeiro orientador: PEDROCHI, Franciana Abstract: The development of bioactive materials is guided by the continuous demand for effective solutions for tissue repair and regeneration, especially in cases of bone diseases, trauma, or infections. In this context, the incorporation of elements with physiological importance constitutes a promising strategy to adjust properties such as bioactivity, degradation rate, and cytocompatibility. This work aimed to synthesize and characterize borophosphate glasses with the composition 50B2O3–20P2O5–15CaF2–(15–x)Na2O–xMO (MO = K2O or Li2O, between 0– 15 mol%), using the melt-cooling method, to evaluate their potential as biomaterials. The study was developed in two stages. In the first, the progressive substitution of Na2O by K2O (0–15 mol%) was investigated, evaluating its effects on physical, structural, vibrational, and thermal properties, as well as on in vitro bioactivity behavior and cytocompatibility. In the second stage, the partial substitution of Na2O by Li2O (0–10 mol%) was analyzed, focusing on the physical, structural, thermal, mechanical, and bioactive properties of the glasses, as well as cytocompatibility and antibacterial activity. The samples were characterized by volumetric density, molar volume, oxygen packing density (OPD), powder X-ray diffraction (PXRD), FTIR spectroscopy, DTA, DSC, SEM-EDS, and Vickers microhardness (Hv). In vitro assays included bioactivity tests in SBF solution for 28 days, cell viability, and antibacterial activity. In the glass series containing K2O, structural expansion, depolymerization of the glass network, increased glass transition temperature (Tg), and high thermal stability were observed. Higher concentrations of K2O promoted increased reactivity in SBF and rapid formation of calcium phosphate and boric acid phases. Compositions containing both Na2O and K2O exhibited nonlinear behavior in the N4 fraction, indicating the occurrence of the mixed alkali effect (MAE). Furthermore, increasing K2O improved bioactive behavior, and the simultaneous presence of alkali oxides in the network favored cell viability. For the glass series containing Li2O, the occurrence of MAE was also observed in the physical properties, structural depolymerization, accompanied by a reduction in Tg. Increasing the Li2O concentration resulted in an increase in Vickers microhardness (Hv), indicating improved mechanical strength of the glasses. All compositions containing Li2O showed bioactivity, confirmed by PXRD and FTIR, and antibacterial activity. Finally, the results demonstrate that incorporating different alkali oxides in the structure of borophosphate glasses is a promising strategy for adjusting structural, mechanical, and bioactive properties, highlighting the potential of these glasses for applications as regenerative biomaterials. Instituição: Universidade Federal do Maranhão Tipo do documento: Tese; Trabalho sob Sigilo. O motivo do sigilo: O pedido de patente BR 10 2024 020751 3 encontra-se dentro dos 18 meses de sigilo no INPI (período contado a partir da data de depósito). Além disso, o sigilo é necessário para preservar a originalidade do artigo científico, oriundo da tese, que se encontra em elaboração para publicação em periódico indexado. Solicitação de patente: BR 10 2024 020751 3 DOI: https://doi.org/10.1016/j.ceramint.2025.12.242

2026-04-02T00:00:00Z MOURA, Geanso Miranda de https://tedebc.ufma.br/jspui/handle/tede/6793 2026-02-25T11:52:31Z 2025-06-30T00:00:00Z

Título: Estudo teórico baseado na teoria do funcional da densidade das propriedades estruturais, eletrônicas e ópticas dos cristais de sarcosina e DL-alanina em função da pressão Autor: MOURA, Geanso Miranda de Primeiro orientador: ANDRADE FILHO, Tarciso Silva de Abstract: The study of the structural and electronic properties of amino acid crystals under different pressure conditions is highly relevant, as these materials have potential for technological applications. Understanding how pressure influences the characteristics of organic crystals can lead to significant advances in the development of new compounds and the optimization of industrial processes. Thus, this research not only advances theoretical knowledge about these systems but also paves the way for technological innovations. The methodology adopted for the computational calculations in this study is based on Density Functional Theory (DFT), using the Quantum ESPRESSO software. The Projector Augmented Wave (PAW) method was employed to perform the computational calculations, and the exchange- correlation components were described using the Perdew-Burke-Ernzerhof (PBE/GGA), PBE for solids (PBEsol/GGA), revised PBE (revPBE/GGA), and the non-local van der Waals correlation functional (vdW-DF). Additionally, the Grimme D3 dispersion term was applied in conjunction with all GGA functionals to correct for dispersion interactions. Geometry optimization was considered converged at 10−3 eV· Å−1 . In this research, the structural and electronic properties of sarcosine and DL-alanine crystals were investigated under extreme hydrostatic pressure conditions, with special attention to lattice parameters and hydrogen bond behavior. For sarcosine, discrete pressure points ranging from 0.0 to 3,7 GPa were used, while for DL-alanine the applied pressure ranged from 0,0 to 18 GPa. The computational results for the optimized lattice parameters a, b, and c and the volume of sarcosine at ambient pressure show deviations of less than 2% compared to experimental values reported in the literature. Regarding electronic properties, sarcosine exhibits a direct band gap at ambient pressure (along the Γ point). The calculated band gap was approximately 5.20 eV, indicating insulating behavior in this configuration. Under pressure, sarcosine displays anisotropic behavior and a theoretical bulk modulus B0 of about 6.98 GPa. Furthermore, the band gap of sarcosine does not decrease monotonically with pressure; it initially decreases from 5,20 eV to 4,90 eV up to approximately 1,4 GPa, then slightly increases, reaching 5,05 eV at 3,7 GPa. This non-linear behavior is interpreted as a result of competition between unit cell contraction and molecular rotation within the crystal. In terms of optical properties, the static dielectric constant showed values of 2,08 in the xx plane, 2,47 in the yy plane, and 2,17 in the zz plane, with the highest polarity in the yy plane, reinforcing the system’s anisotropic behavior. Strong absorption in the ultraviolet region indicates potential application as ultraviolet light polarizers. For DL-alanine, the computational results for the optimized lattice parameters and unit cell volume decrease continuously with increasing pressure, showing excellent agreement with available experimental data. Additionally, the b parameter decreased by approximately 14%, indicating greater flexibility of the crystal in this direction. Under pressure up to 18 GPa, DL-alanine exhibits anisotropic behavior and a theoretical bulk modulus B0 of about 8.48 GPa. Regarding the theoretical value of the crystalline dipole moment, the value obtained at ambient pressure was approximately 75 Debye, while above 15 GPa a sharp drop is observed, reaching approximately 38 Debye at 17,5 GPa. The voids are also drastically minimized, ranging from 84,76 Å3 at ambient pressure to values below 3,94 Å3 at pressures above 16,4 GPa - a reduction of approximately 95%. The results presented here are essential for a deeper understanding of the potential technological applications of sarcosine and DL-alanine in different scenarios, highlighting the relevance of theoretical studies dedicated to the investigation of crystalline systems under high- pressure conditions. This research deepens the understanding of intermolecular interactions, as well as the optical, structural, and electronic properties of organic crystals, establishing a solid foundation for future investigations in the field of materials science. Instituição: Universidade Federal do Maranhão Tipo do documento: Tese

2025-06-30T00:00:00Z