Submissões Recentes
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Livro IPEN-doc 31685 Radiografia industrial
2025 - LEVY, DENISE
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Livro IPEN-doc 31684 Irradiação de alimentos
2025 - VILLAVICENCIO, ANNA L.C.H.; LEVY, DENISE
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Artigo IPEN-doc 31550 Antibacterial resin composites with sustained chlorhexidine release
2025 - GONCALVES, FLAVIA; SILVA, LARISSA S.T.; ROSCHEL, JULIA N.; SOUZA, GRECA de; CAMPOS, LUIZA de P. M.; VARCA, GUSTAVO H.; PARRA, DUCLERC; PEREZ, MIRKO A.; GORDILHO, ANTONIO C.; BRANDT, WILLIAM C.; BOARO, LETICIA
Background: The addition of chlorhexidine in dental restorative materials is a promising strategy to reduce the recurrence of tooth decay lesions. However, the main challenge is to develop materials with antimicrobial activity in the long term. Objective: This study analyses the effect of filler type and concentration of resin composites supplemented with chlorhexidine loaded in carrier montmorillonite particles (MMT/CHX) regarding their chemical, physical, and short- and long-term antimicrobial proprieties. Materials: Experimental composites were synthesized with 0, 30, or 60% filler in two ratios, 70/30 and 80/20, of barium glass/colloidal silica, respectively, and 5 wt% MMT/CHX. Conversion was measured using near Fourier-transform infrared spectrometry. Sorption and solubility were determined by specimen weight before and after drying and immersing in water. Flexural strength (FS) and elastic modulus (E) were determined by three bending tests using a universal test machine. Chlorhexidine release was monitored for 50 days. Streptococcus mutans UA159 was used in all microbiological assays. Inhibition halo assay was performed for 12 months and, also, biofilm growth for the specimens and colony-forming unit (CFU). Remineralization assay was used on restored teeth using measurements of microhardness Knoop and CFUs. Results: Conversion, sorption, and solubility were not affected by filler type and concentration. FS and E increase with the filler concentration, independent from filler type. Chlorhexidine was significantly released for 15 days for all experimental materials, and the increase in filler concentration decreased its release. Halo inhibition was observed for a longer time (12 months) in materials with 60 wt% filler at 70/30 proportion. Also, 60 wt% filler materials, independent from the filler ratio, reduced the CFU in relation to the control group from 8 to 12 months. In the remineralization assay, besides the absence of differences in hardness among the groups, after biofilm growth, the CFU was also significantly lower in materials with 60 wt% filler. Conclusions: Materials with 60% filler, preferentially with 70% barium glass and 30% silica, and 5% MMT/CHX particles demonstrated long-term antimicrobial activity, reaching 12 months of effectiveness. Also, this formulation was associated with higher mechanical properties and similar conversion, sorption, and solubility compared to the other materials.
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Artigo IPEN-doc 31507 The impact of sintering and Mg doping on the ionic conductivity of Sm2Zr2O7 pyrochlores
2025 - BLASCO-ZARZOZO, SILVIA; SANTOS-VEIGA, EMERSON L. dos; CHUNG, U-CHAN; FOURCADE, SEBASTIEN; ELISSALDE, CATHERINE; MAUVY, FABRICE; CORDONCILLO, ELOISA; BELTRAN-MIR, HECTOR
Pyrochlore structures based on Sm2Zr2-xMgxO7-x (x = 0, 0.1, 0.15 and 0.2) were synthesized by hydrothermal method at 180 °C and the resulting powders fired at 1200 °C for 2h. Two sintering methods were employed: Conventional Sintering (CS) with uniaxial pressing and Spark Plasma Sintering (SPS), both at 1350 °C. Resulting pellets had relative densities of ∼70 % (CS) and ∼97 % (SPS), with nano-size grains. Electrochemical Impedance Spectroscopy (EIS) was performed under various atmospheres to assess the impact of sintering on electrical properties. All samples exhibit ionic conductivity, with Mg-doped compositions showing the highest conductivity whatever the sintering process used. SPS samples showed higher conductivity than those sintered by CS, with the x = 0.10 composition (SMZ01) exhibiting the highest conductivity. The overall conductivity was unaffected by atmosphere (air, N2 and H2–N2), indicating good stability and resistance to reduction/oxidation. Notably, SMZ01 sintered by SPS exhibits total conductivity comparable to Yttria-Stabilized Zirconia (YSZ), a standard electrolyte in oxide-ion conducting applications. These Mg-doped ceramics, especially when processed by SPS, offer excellent relative density and conductivity, making them promising candidates for use in Solid Oxide Fuel Cells (SOFCs), Solid Oxide Electrolysis Cells (SOECs), gas sensors, and other clean energy technologies requiring thermal and physical stability.