Nature-Inspired Unconventional Approaches to Develop 3D Bioceramic Scaffolds with Enhanced Regenerative Ability

Material science is a relevant discipline in support of regenerative medicine. Indeed, tissue regeneration requires the use of scaffolds able to guide and sustain the natural cell metabolism towards tissue regrowth. This need is particularly important in musculoskeletal regeneration, such as in the case of diseased bone or osteocartilaginous regions for which calcium phosphate-based scaffolds are considered as the golden solution. However, various technological barriers related to conventional ceramic processing have thus far hampered the achievement of biomimetic and bioactive scaffolds as effective solutions for still unmet clinical needs in orthopaedics. Driven by such highly impacting socioeconomic needs, new nature-inspired approaches promise to make a technological leap forward in the development of advanced biomaterials. The present review illustrates ion-doped apatites as biomimetic materials whose bioactivity resides in their unstable chemical composition and nanocrystallinity, both of which are, however, destroyed by the classical sintering treatment. In the following, recent nature-inspired methods preventing the use of high-temperature treatments, based on (i) chemically hardening bioceramics, (ii) biomineralisation process, and (iii) biomorphic transformations, are illustrated. These methods can generate products with advanced biofunctional properties, particularly biomorphic transformations represent an emerging approach that could pave the way to a technological leap forward in medicine and also in various other application fields.

Preparation, microstructure studies and mechanical properties of glazes ceramic sanitary ware based on kaolin

In this paper, the use of local kaolin coming from Djebel Debbagh (denoted DD1) in the composition of ceramic glazes for sanitary ware was examined. Because of its natural abundance, low price and good characteristics, this kaolin represents an interesting economic alternative to other mineral clays. The chemical composition showed that this kaolin contains 38.49 wt.% Al2O3 and 44.85 wt.% SiO2. Two glazes based on kaolin DD1 denoted as GaDD1 and GbDD1 were prepared with conventional ceramic processing techniques at temperature 1250 oC. As a reference, another glaze (Gref) based on kaolin Remblend was also prepared in the same conditions. The samples were characterized with X-ray diffraction and Scanning Electron Microscope. The results revealed that zircon and quartz are the crystalline phases present in these glazes. In the sample GaDD1, it was found that the degree of whiteness is very high and reaches 93.30 %. However, the water absorption coefficient is low which is about 0.19 ? 0.04 %. In addition, the flexural strength and the Vickers microhardness are respectively, about 56.07 ? 5.61 MPa and 7952.80 ? 101.76 MPa. These properties are compatible with those of the glaze reference Gref and commercial sanitary ware glazes, indicating the potential use of kaolin DD1 in the production of glazed ceramic for sanitary ware applications.

Heavily donor-doped, optically translucent ferroelectric barium titanate ceramics through defect chemical engineering

The possibility of preparing translucent ferroelectric heavily donor-doped BaTiO3 ceramics rich in TiO2 has been demonstrated by conventional ceramic processing based on the synthesis via the solid state route and on subsequent sintering and annealing at high levels of oxygen partial pressure.

Positron Annihilation in ZnO Based Varistor Doped with Semiconductor Additives

Coincidence Doppler broadening spectra measurements on ZnO-based varistor doped with semiconductor additives have been investigated, and the proposed samples exhibit different characteristics. The peak of the ratio curve of pure zinc is the highest, the Positron Lifetime in sample a03 doped with ZT is the longest. The maximum probability of the positron-3d electron occurs in sample doped with semi-ZnO (sintered at 1300 °C for 2h with conventional ceramic processing method). The electrical characteristics of the samples and the behavior of positrons in ZnO-based varistor have been discussed.

Effect of Pr6O11 Doping on the Microstructural and Electrical Properties of ZnO-Pr6O11-Co3O4-Cr2O3-SnO2 Varistors

ZnO-Pr6O11-Co3O4-Cr2O3-SnO2 varistors with different doping levels of Pr6O11 (0.25-2 mol%) were prepared at 1300 °C with conventional ceramic processing, and the effect of Pr6O11 doping on the microstructure and electrical properties of the varistor materials were investigated. The results indicated that the doped Pr6O11 basically existed at the boundary of ZnO grains in the varistor ceramics, and SnO2 might enter into the lattice of ZnO grains or precipitate in reaction with Pr6O11 into Pr2Sn2O7 at the gain boundaries particularly where there were three or more ZnO grains. The analysis of scanning electron microscopy further revealed that Pr6O11 doping would inhibit the growth of ZnO grains, resulting in decreasing ZnO grain size with increasing doping level of Pr6O11. The measured electric-field/current-density characteristics of the samples showed that the varistor voltage increased with increasing doping level of Pr6O11 when the doping level was no more than 1.5 mol%, and the nonlinear coefficient of the varistors increased with increasing doping level of Pr6O11 up to no more than 1.0 mol% in the varistors, respectively.

The Influence of Microstructures of Ceramics on the Monitoring of Environmental Humidity

The sensing elements for humidity has been vastly researched to be applied in several areas, since automotive and food industries up to automation in the agricultural production and in the environmental monitoring. In this work, ceramic material are focused, owing to their unique structure, consisting of grains, grain boundaries, surfaces and pores, the control of which allow to obtain suitable microstructure to be used as humidity sensors. In this work, the influence of the relative humidity on the electrical conductivity of the ceramic sensing elements of ZrO2and of TiO2, under specific climatic conditions, is investigated. In this sense, the ceramics used as humidity sensing elements were manufactured through conventional ceramic processing. The sintered ceramics were characterized through X-ray diffractometry techniques, scanning electron microscopy, apparent density by the Archimedes principle and linear retraction. The results showed the development of a solid solution of ZrO2-TiO2. The microstructures presented a homogeneous distribution of pores. The ceramic tablets, sintered at 1100 °C, evidenced a linear behaviour in the curves capacitance versus environment humidity.

Microstructure and nonohmic properties of SnO2–Ta2O5–TiO2 varistor system doped with CuO

The microstructure and nonohmic properties of SnO 2– Ta 2 O 5– TiO 2- CuO varistor system were investigated. The proposed samples were doped with different contents of CuO (0–6 mol%) and sintered at 1400°C for 2 h with conventional ceramic processing method. In all the samples, the commonly identified phase was SnO 2 (rutile); however, with increasing doping amount of CuO , the peaks of CuO phase emerged in the X-ray diffraction (XRD) patterns. Scanning electron microscopy (SEM) examination on the fractured surfaces of the samples revealed that a minor amount of CuO dopant can facilitate the sintering of the varistor ceramics, but excessive CuO would mainly segregate at grain-boundaries. The doped CuO may also act as a modifier in the SnO 2 based varistors. The measured electric-field versus current-density characteristics of the samples indicated that both nonlinear exponent and varistor voltage increased with increasing doping amount of CuO up to 3 mol% and then decreased with excessive CuO .

Microstructure and Electrical Properties of Al2O3-Doped Ba0.9Ca0.1Ti0.8Zr0.2O3 Based Dielectric Ceramics

Al2O3-doped Ba0.9Ca0.1Ti0.8Zr0.2O3(short for BCTZ) based dielectric ceramics were fabricated by sintering samples at 1300°C for 2h with conventional ceramic processing method. The microstructure and electrical properties of the as-prepared samples were investigated. X-ray diffraction analysis showed that after the addition of Al2O3with the amount designed in this study, no new phase was examined in the detection limit. Through scanning electron microscopy it was found that the doping of Al2O3can help the growth of BCTZ grains, and the relative permittivities of the samples. The result of electrical properties indicated that the resistance and the break voltage of the samples could be improved to some extent with appropriate doping amount of Al2O3resulting in the highest dielectric constant ~17000, low dielectric loss <10%, and highest break voltage 8.4 kV/mm, respectively.

Microstructure and Nonohmic Properties of SnO2-Ta2O5-ZnO System Doped with ZrO2

The microstructure and nonohmic properties of SnO2-Ta2O5-ZnO varistor system doped with different amounts of ZrO2(0–2.0 mol%) were investigated. The proposed samples were sintered at 1400°C for 2 h with conventional ceramic processing method. By X-ray diffraction, SnO2cassiterite phase was found in all the samples, and no extra phases were identified in the detection limit. The doping of ZrO2would degrade the densification of the varistor ceramics but inhibit the growth of SnO2grains. In the designed range, varistors with 1.0 mol% ZrO2presented the maximum nonlinear exponent of 15.9 and lowest leakage current of 110 μA/cm2, but the varistor voltage increased monotonously with the doping amount of ZrO2.