Hugo. P. A. Alves

In this study, we report an experimental investigation of the structural, morphological, and electrical properties of the ZrO₂-Ag-Graphene sheet. In particular, we use the tape casting technique to produce the flexible ZrO₂ ceramic sheet and impregnation and magnetron sputtering techniques to incorporate graphene and silver. Structural and morphological analyses indicate the presence of graphene and silver in the ceramic matrix, confirming the methods efficiency. We noticed that with the deposition of graphene and silver on the ZrO₂ sheet, there is a decrease in electrical resistance. This fact is associated with the crystalline structure and morphology of graphene and silver, which makes sheets attractive in electrical applications. Thus, our results become fascinating for specific technological applications.

The mineralization process to reach Tungsten (W) involves several steps to reduce the impurities (residues), which makes the process more expensive. However, it is possible to explore the pure scheelite (CaWO₄) and residue doped-CaWO₄ on flexible sheets using the Tape Casting technique. In particular, the high frequency dielectric properties of flexible multilayers have an increased appeal in the electronics industry. In this study, we present a systematic investigation of structural, morphological, electrical and high-frequency dielectric properties of flexible ceramics sheet multilayers composed of pure CaWO₄ and residue-doped CaWO4. Our findings demonstrate that the dielectric constant has a small dependence on the residue amount, but a remarkable modification in the dielectric constant as the number of layers increases. Here we achieved a 34% increase in the dielectric constant for pure CaWO₄ flexible ceramic sheets when the number of layers increased from 1 to 3.

This work presents a novel tape‐casting method for producing flexible, graphene‐enhanced diatomite ceramic sheets. These sheets target dielectric substrates for applications in the critical yet under‐explored, high‐frequency range. Structural and morphological analyses confirmed the incorporation of graphene nanoplatelets into the ceramics matrix, validating the efficiency of the tape‐casting process. The results show the crucial role of the composite's crystalline structure in its dielectric response, where oxygenated functional groups within the graphene nanoplatelets act as intrinsic barriers to restrict leakage current, resulting in low dielectric loss. Doping of flexible ceramic plates with graphene nanoplatelets led to significant dielectric variations of approximately 100% over a wide frequency range. The capacitance increased by 215.35 with the addition of 10 wt. graphene compared to pure diatomite. Our results demonstrate the ability to adapt the framework's structural, morphological, and dielectric properties through doping with graphene in diatomite, offering promising prospects for applying flexible ceramic sheets at high frequency.

In this study, we produced, through hot pressing (HP) and spark plasma sintering (SPS) techniques, Al₂O₃-NbC composites for applications in machining processes. We report an experimental investigation of sintered composites’ structural, thermal, morphological, physical, and mechanical properties. The results confirm that the Al₂O₃-NbC composite sintered by both techniques presents a heterogeneous microstructure with distinct grain sizes and irregular geometries. Another stimulating factor is the increase of 25.86% in Vickers hardness, 14.89% in Young’s modulus, and 16.52% in mechanical strength of the composite sintered by SPS about the composite sintered by HP. Thus, our results can be used to address material properties targeting the needs of specific technological applications.

Incorporating magnetic materials in ceramic matrices becomes an attractive topic due to its versatility and wide range of applications. Therefore, this work aims to produce zirconia‐magnetic particles and zirconia‐graphene composites, investigating their structural and magnetic properties. The ceramic composites were produced by the tape casting technique and characterized by X‐ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and magnetic measurements. The microstructural characterization showed monoclinic and tetragonal zirconia phases from the zirconia powder and the magnetite and hematite phases from the magnetic particles. Three peaks of characteristics known as band D, G, and 2D evidenced the presence of graphene. The morphology of the zirconia‐magnetic particles and zirconia‐graphene composites showed grains with irregular shapes and varying sizes; however, the zirconia‐graphene composite showed the presence of pores and agglomerates due to the plasma heat‐treatment process. The uniform dispersion of the elements in both ceramic composites confirmed the efficiency of the applied method. The magnetic characterizations of the green and sintered zirconia‐magnetic particles and zirconia‐graphene composites were studied in a wide range of magnetic fields and temperatures (5 to 300 K). Before sintering, the magnetite phase commanded the magnetic response of the zirconia‐magnetic particles composite, showing a ferrimagnetic behavior, after sintering, the hematite phase content increased by approximately 27%, causing a change in the ferrimagnetic order to antiferromagnetic. It was found that the 1% graphene insertion in the zirconia ceramic composite was responsible for the ferromagnetic behavior of the sintered composite. Ceramic composites become future candidates for technological applications in spintronic devices and magnetic storage.

High‐temperature co‐fired ceramic (HTCC) technology aims to incorporate fluxing materials into ceramic tapes to decrease the sintering temperature. In this context, we incorporate waste from sugarcane bagasse ash (SCBA) into alumina (Al ₂ O ₃ ) tapes. We report an experimental investigation of the structural, physical, mechanical, and dielectric properties of the Al ₂ O ₃ tape with the addition of the SCBA waste. The tape casting technique prepared the ceramic tape. The materials under study were characterized by rheology, thermogravimetry, dilatometry, X‐ray diffraction, scanning electron microscopy, relative density, Vickers microhardness, mechanical resistance, and dielectric measurements. The dilatometry results confirm that the addition of the SCBA waste remarkably reduces the sintering temperature of the Al ₂ O ₃ tape to 1200 ° C. The physical, mechanical, and dielectric properties are improved with the addition of the SCBA waste, which makes our discoveries attractive from an environmental and economic point of view. Besides, the stabilization and high dielectric constant of the Al ₂ O ₃ ‐SCBA tape becomes a promising material for aircraft turbine applications.