Bubble generation in refractory porous plugs: The role of the ceramic surface composition Luís Otávio Zaparoli Falsetti, Dereck Nills Ferreira Muche, Marcello Rubens Barsi Andreeta, Murilo Henrique Moreira, Victor Carlos Pandolfelli International Journal of Ceramic Engineering and Science, 2022 Porous ceramic plugs are refractory devices applied in the steel ladle to inject gas bubbles into the liquid metal, aiming at its chemical and thermal homogenization, and the removal of non‐metallic inclusions. Regarding its wear and corrosion resistance, the plug composition typically exhibits a low wettability by liquid steel to limit its infiltration into the porous structure. However, an additional aspect for the performance of plugs is their ability to control the size of the generated bubble, maximizing the likelihood of capturing inclusions. Based on the importance of this process to attain high‐performance materials, this work studied the injection of gas into liquid media through ceramic capillary structures, focusing on the influence of the pore diameter and the contact angle upon the size of the generated bubble. The available models in the literature were analyzed and compared to the experimental results for a water–air system. As an outcome, a shape‐corrected model for bubbling is proposed highlighting the region where the material dominates over the pore diameter to dictate the bubble size. Extending the model to the steel ladle, the results suggest the composition of the ceramic plug's surface as a key aspect to improve the cleanliness of the molten steel.
Oriented Crystal Growth of La0.557Li0.330TiO3in Bulk Ceramics Induced by LaAlO3Single-Crystal Fibers Tao Wang, Rafael B. de Oliveira, Marcello R. B. Andreeta, Haoyuan Wang, Zhitai Jia, Xutang Tao Crystal Growth and Design, 2021 Perovskite La0.557Li0.330TiO3 (LLTO) has been considered as one of the most promising solid-state electrolytes for lithium-ion batteries because of its high bulk ionic conductivity at room temperat...
Viscosity and liquidus-based predictor of glass-forming ability of oxide glasses Jeanini Jiusti, Edgar D. Zanotto, Daniel R. Cassar, Marcello R. B. Andreeta Journal of the American Ceramic Society, 2020 Glass‐forming ability (GFA) is a measure of the easiness to vitrify a given substance. Theoretically, it is possible to make a glass from any liquid provided it is quenched from its liquidus temperature with a cooling rate above a critical value Rc to avoid crystallization. However, measuring GFA is a laborious and time‐consuming task. Moreover, predicting the GFA of substances that have never been vitrified is of greater interest. Here, we propose and evaluate a new parameter that can predict the glass forming ability of oxide mixtures. We derived a mother parameter, GFA = 1/Rc [U(Tmax) × TL]−1, where U(Tmax) is the maximum crystal growth rate, and TL is the liquidus temperature, which strongly correlates with the experimental critical cooling rates of oxide glass‐formers. A simplified version derived from the mother parameter—which does not need (scarce) crystal growth rate data and only relies on viscosity η and TL, GFA [η(TL)/]—also correlates well with the Rc of several oxide compositions. This new GFA parameter, dubbed Jezica, works when heterogeneous nucleation prevails. It corroborates the widespread concept that substances having high viscosity at TL, and a low TL can be easily vitrified, and provides a powerful tool for the quest and design of novel glasses.
Co2 laser for dental alumina ceramic framework welding Ricardo Sgura, André Guaraci DeVito Moraes, Stephane Silva Reis, Adriana Rios Mafra Ferrari, Marcello Rubens Barsi Andreeta, Igor Studart Medeiros Brazilian Dental Science, 2019 Objective: Despite the increase of all-ceramic prosthesis in dental practice there is no evidence of the possibility of welding these structures if necessary. The objective of this study was to use CO2 laser (?=10.6µm) as a welding agent to fuse dental polycrystalline alumina ceramic. Methods: Ceramic blocks of pre-sintered alumina were sectioned into 20 bars (10.0 x 1.5 x 1.5mm) and sintered to the final cross?section dimension of 1.2 x 1.2mm. The bars were adapted to an LHPG (Laser Heated Pedestal Growth) system device where the bars could be fixed in pairs and have their ends irradiated with CO2 laser to fusion. The ring-shaped laser beam (300 µm thickness) was directed with the aid of mirrors to reach samples’ ends. The laser was continuously applied (40W nominal power, 5 seconds). After welding, the samples were analyzed in stereomicroscope and SEM. A diffraction analysis was carried out with one sample. Results: The ceramic bars were successfully fused, but some of them showed some shape distortion in the fusion zone. The aspect of the fused alumina differed in color and translucency from the original sintered material. SEM evidenced the presence of porosity and voids in the center of the fusion zone. X-ray diffraction pointed to a reduction in crystallite size by two to four times in the welded region of samples. Conclusions: This study points to CO2 laser as a possible welding agent to polycrystalline alumina dental ceramic. Porosity observed in the molten zone gives cause for concern regarding weld resistance.
Innovative Design for the Enhancement of Lithium Lanthanum Titanate Electrolytes Rafael B. de Oliveira, Marcello R. B. Andreeta, Dulcina M. P. F de Souza, João E. F. S. Rodrigues, Paulo S. Pizani Crystal Growth and Design, 2019 The high ionic conductivity in lithium lanthanum titanate perovskite ceramics, Li3xLa(2/3)-xTiO3 (LLTO), is well-known for the x ≈ 0.11 lithium concentration. The grain conductivity is approximatel...
Laser-heated crystallization of eutectic composition glass Angela Santana Nunes, Rafael Bonacin de Oliveira, Marcello Rubens Barsi Andreeta Crystengcomm, 2019 Laser-heated microstructure crystallization control of a eutectic composition Li2O–CaO–SiO2 glass system.
Growth, characterization and magnetic properties of polycrystalline fibers of electron doped manganites Doping Properties Mechanisms and Applications, 2013
Precision micromachining of carbon nanotubes composites Proceedings of the 9th International Conference of the European Society for Precision Engineering and Nanotechnology Euspen 2009, 2009
