Exfoliation of titanium nitride using a non-thermal plasma process.

In this study, we present a novel approach for the exfoliation of titanium nitride (TiN) powders utilizing a rapid, facile, and environmentally friendly non-thermal plasma method. This method involves the use of an electric arc and nitrogen as the ambient gas at room temperature to generate ionized particles. These ionized species interact with the ceramic crystal of TiN, resulting in a pronounced structural expansion. The exfoliated TiN products were comprehensively characterized using transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. Remarkably, the cubic crystal structure of TiN was effectively retained, while the (200) crystal plane d-spacing increased from 2.08 to 3.09 Å, accompanied by a reduction in crystallite size and alterations in Raman vibrational modes. Collectively, these findings provide compelling evidence for the successful exfoliation of TiN structures using our innovative non-thermal plasma method, opening up exciting possibilities for advanced material applications.

Dental zirconia microwave-sintering followed by rapid cooling protocol.

OBJECTIVES: This study aimed to evaluate the effect of microwave sintering temperature and cooling rate (MS) on 3Y-TZP ceramics and its influence on the ceramic microstructure and mechanical properties. Specifically, to optimize the sintering process, reducing the total sintering time compared to conventional sintering. MATERIALS AND METHODS: Eighty-four pre-sintered Y-TZP discs (Vipi block Zirconn, VIPI) (ISO 6872) were divided into seven groups (n = 12) according to the sintering conditions: conventional sintering (CS) at 1530 °C for 120 min and microwave sintering at 1400 °C (MS1400) and 1450 °C (MS1450) for 15 min followed by different cooling conditions: rapid cooling (RC), cooling at 400 °C (C400) and 25 °C (C25). The specimens were submitted to apparent density measurements, X-ray diffraction analysis (XRD), scanning electron microscopy, and biaxial flexural strength test. Data was statistically analyzed through two-way ANOVA, Tukey, Sidak, Dunnett and Weibull (α = 0.05). RESULTS: All MS1400 groups presented lower density values than the CS and MS1450 groups. Two-way ANOVA revealed that the MS temperature and cooling rate affected the biaxial flexural strength of the Y-TZP (p < 0.01). Group MS1400RC presented lower biaxial flexural strength values (681.9 MPa) than MS1450RC (824.7 MPa). The cooling rate did not statistically decrease the biaxial strength among the groups submitted to microwave sintering at 1450 °C. XRD analysis showed that the sintering and cooling temperature did not induce tetragonal to monoclinic phase transformation. CONCLUSIONS: Microwave sintering at 1450 °C for 15 min followed by rapid cooling can be a viable fast alternative protocol for Y-TZP sintering, compared with the conventional sintering, reducing the total sintering time by 75% and reducing the energy used for the sintering process without affecting the Y-TZP biaxial flexural strength and relative density compared to the conventional sintering. Moreover, the microwave technique promoted smaller grains and did not induce monoclinic phase formation.

Development of Y-TZP/MWCNT-SiO2 nanocomposite for dental protheses.

Y-TZP/MWCNT-SiO2 nanocomposite was synthesized by co-precipitation and hydrothermal treatment methods. After the characterization of the MWCNT-SiO2 powder, specimens were obtained from the synthesized material Y-TZP/MWCNT-SiO2 by uniaxial pressing for a second characterization and later comparison of its optical and mechanical properties with the conventional Y-TZP. The MWCNT-SiO2 was presented in bundles of carbon nanotubes coated by silica (mean length: 5.10 ± 1.34 µm /D90: 6.9 µm). The composite manufactured was opaque (contrast ratio: 0.9929 ± 0.0012) and had a white color with a slightly difference from the conventional Y-TZP (ΔE00: 4.4 ± 2.2) color. The mechanical properties of Y-TZP/MWCNT-SiO2: vickers hardness (10.14 ± 1.27 GPa; p = 0.25) and fracture toughness (4.98 ± 0.30 MPa m1/2; p = 0.39), showed no significant difference from the conventional Y-TZP (hardness: 8.87 ± 0.89; fracture toughness: 4.98 ± 0.30 MPa m1/2). However, for flexural strength (p = 0.003), a lower value was obtained for Y-TZP/MWCNT-SiO2 (299.4 ± 30.5 MPa) when compared to the control Y-TZP (623.7 ± 108.8 MPa). The manufactured Y-TZP/MWCNT-SiO2 composite presented satisfactory optical properties, however the co-precipitation and hydrothermal treatment methods need to be optimized to avoid the formation of porosities and strong agglomerates, both from Y-TZP particles and MWCNT-SiO2 bundles, which lead to a significant decrease in the material flexural strength.

Physico-chemical characterization and biocompatibility of hydroxyapatite derived from fish waste.

The aim of this study was to synthesize hydroxyapatite (HAP) powder from fish waste. The powder was characterized through X-ray diffraction, Fourier transform infrared spectroscopy, ion exchange chromatography, scanning electron microscopy and plasma emission spectrometry. The cyto- and genotoxicity was carried out to demonstrate biocompatibility in vivo by means of rat subcutaneous tissue test. The results showed that the visible crystalline nature of typical apatite crystal structure when they were calcined at 800 °C. Infrared spectroscopy analysis showed similar composition to HAP standard with the presence of carbonate ion demonstrated by wave number values of 871 cm-1 and 1420 cm-1 for calcinations at 800 °C. The scanning electronmicrographies depicted the crystal morphology and porous nature with average pore size of ~10 µm. Plasma emission spectrometry and ion exchange chromatography confirmed the presence of Ca and P in the samples. The mean of calcium content was 36.8; Mg was 0.8, Na was 0.7 and K was 0.5. Rat subcutaneous tissue test revealed that HAP presented biocompatibility. Furthermore, the lack of cyto- and genotoxicity in blood, liver, kidney and lung were noticed after 30 days of HAP implantation. Taken together, our results demonstrated that HAP from fish waste exhibits a great potential for using as biomaterial since is represents a simple, effective, low-cost process and satisfactory degree of biocompatibility.

Effect of titania content and biomimetic coating on the mechanical properties of the Y-TZP/TiO2 composite.

OBJECTIVE: To investigate the effect of titania addition (0, 10 and 30mol%) on the microstructure, relative density, Young's modulus (E), Poisson's ratio (υ), mechanical properties (flexural strength, σf, and Weibull modulus, m) of a Y-TZP/TiO2 composite. The effect of the presence of a biomimetic coating on the microstructure and mechanical properties was also evaluated. METHODS: Y-TZP (3mol% of yttria) and Y-TZP/TiO2 composite (10 or 30mol% of titania) were synthesized by co-precipitation. The powders were pressed and sintered at 1400°C/2h. The surfaces, with and without biomimetic coating, were characterized by X-ray diffraction analysis and scanning electron microscopy. The relative density was measured by the Archimedes' principle. E and υ were measured by ultrasonic pulse-echo method. For the mechanical properties the specimens (n=30 for each group) were tested in a universal testing machine. RESULTS: Titania addition increased the grain size of the composite and caused a significant decrease in the flexural strength (in MPa, control 815.4a; T10 455.7b and T30 336.0c), E (in GPa, control 213.4a; T10 155.8b and T30 134.0c) and relative density (control 99.0%a; T10 94.4%c and T30 96.3%b) of the Y-TZP/TiO2 composite. The presence of 30% titania caused substantial increase in m and υ. Biomimetic coating did not affect the mechanical properties of the composite. SIGNIFICANCE: The Y-TZP/TiO2 composite coated with a layer of CaP has great potential to be used as implant material. Although addition of titania affected the properties of the composite, the application of a biomimetic coating did not jeopardize its reliability.

Surface roughness and volumetric contraction of a Y-TZP ceramic sintered by microwave energy and by resistive heating / Rugosidade da superfície e contração volumétrica de uma cerâmica Y-TZP sinterizada por energia de microondas e por aquecimento resistivo

Objectives: The aim of this study was to evaluate a Y-TZP ceramic sintered by a microwave protocol on volume shrinkage and surface roughness. Material and Methods: Twenty four (N=24) Y-TZP discs were fabricated by milling in CAD/ CAM for size standardization. The mean final dimensions of the specimens were 15 mm X 1.6 mm. Samples were divided into 2 groups (n=12): conventional resistive heating sintering protocol (C - Control) and microwave sintering protocol (MO - experimental). For the characterization of the specimens, surface roughness (Ra and Rz parameters) was evaluated with a roughness tester, and volume shrinkage was measured with a hand micrometer. Data were statistically evaluated by Student's t and Mann-Whitney U tests (α=0.05). Results: The roughness results were: 0.25 µm ± 0.02 (Ra) and 2.68 µm ± 0.666 (Rz) for the MO samples; 0.26 µm ± 0.04 (Ra) and 2.73 µm ± 0.461 (Rz) for the C group (Ra: p = 0.19; Rz: p = 0.81). The shrinkage results was: MO (21.02% ± 2.70) and C (20.10% ± 0.52) (p = 0.274). Conclusion: The conventional and microwave sintering methods were similar regarding surface roughness and volume shrinkage of Y-TZP dental ceramic (AU)

Objetivo: avaliar uma cerâmica de zircônia estabilizada com óxido de ítrio (Y-TZP) sinterizada por um protocolo em micro-ondas quanto à contração volumétrica e a rugosidade superficial. Material e Métodos: Vinte e quatro discos (n = 24) de Y-TZP foram fresados em CAD / CAM para padronização do tamanho. A dimensões finais médias dos corpos de prova foram de 15 mm X 1,6 mm. As amostras foram divididas em 2 grupos (n = 12): protocolo de sinterização convencional por aquecimento resistivo (C - Controle) e protocolo de sinterização por microondas (MO - experimental). A caracterização das amostras foi realizada pela avaliação da rugosidade superficial, com um rugosímetro (parâmetros Ra e Rz) e da contração volumétrica, medida com um micrômetro manual. Os dados foram estatisticamente avaliados pelos testes de t-Studant e U-Mann-Whitney (α=0,05). Resultados: Os resultados de rugosidade foram: 0,25 µm ± 0,02 (Ra) e 2,68 µm ± 0,666 (Rz) para o MO; e 0,26 µm ± 0,04 (Ra) e 2,73 µm ± 0,461 (Rz) para o grupo C (Ra: p = 0,19; Rz: p = 0,81). A contração volumétrica foi de: MO (21,02% ± 2,70) e C (20,10% ± 0,52) (p = 0,274). Conclusão: os métodos de sinterização convencionais e de microondas são semelhantes, no que diz respeito à rugosidade superficial e retração de volume da cerâmica dental Y-TZP. (AU)

Physico-chemical characterization of zirconia-titania composites coated with an apatite layer for dental implants.

OBJECTIVES: To investigate the crystalline phases, morphological features and functional groups on the surface of sintered Y:TZP/TiO2 composite ceramics before and after the application of a biomimetic bone-like apatite layer. The effect of TiO2 content on the composite's characteristics was also evaluated. METHODS: Samples of Y:TZP containing 0-30mol% TiO2 were synthesized by co-precipitation, followed by filtration, drying and calcination. The powders were uniaxially pressed and sintered at 1500°C/1h. To obtain biomimetic coatings the samples were exposed to sodium silicate solution and then to a concentrated simulated body fluid solution. The surfaces, before and after coating, were characterized by diffuse reflectance infrared Fourier transformed spectroscopy, X-ray diffraction analysis and scanning electron microscopy. RESULTS: The surfaces of all Y:TZP/TiO2 samples were covered with a dense and uniform calcium phosphate layer with a globular microstructure. This layer was crystalline for specimens with 30% of TiO2 and amorphous for specimens with 0 and 10% of TiO2. Chemical analysis indicated that this layer was composed of type A carbonate apatite. Among the materials tested, the composite with 10% of TiO2 showed the best overall chemical and physical features, such as higher density and more cohesive amorphous apatite layer. SIGNIFICANCE: Y-TZP-based materials obtained in the present investigation by means of the successful association of a calcium phosphate biomimetic layer with small amounts TiO2 should be further explored as an option for ceramic dental implants with improved bioactivity.

Y-TZP ceramic processing from coprecipitated powders: a comparative study with three commercial dental ceramics.

OBJECTIVES: (1) To synthesize 3mol% yttria-stabilized zirconia (3Y-TZP) powders via coprecipitation route, (2) to obtain zirconia ceramic specimens, analyze surface characteristics, and mechanical properties, and (3) to compare the processed material with three reinforced dental ceramics. METHODS: A coprecipitation route was used to synthesize a 3mol% yttria-stabilized zirconia ceramic processed by uniaxial compaction and pressureless sintering. Commercially available alumina or alumina/zirconia ceramics, namely Procera AllCeram (PA), In-Ceram Zirconia Block (CAZ) and In-Ceram Zirconia (IZ) were chosen for comparison. All specimens (6mmx5mmx5mm) were polished and ultrasonically cleaned. Qualitative phase analysis was performed by XRD and apparent densities were measured on the basis of Archimedes principle. Ceramics were also characterized using SEM, TEM and EDS. The hardness measurements were made employing Vickers hardness test. Fracture toughness (K(IC)) was calculated. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey's test (alpha=0.05). RESULTS: ANOVA revealed that the Vickers hardness (p<0.0001) and fracture toughness (p<0.0001) were affected by the ceramic materials composition. It was confirmed that the PA ceramic was constituted of a rhombohedral alumina matrix, so-called alpha-alumina. Both CAZ and IZ ceramics presented tetragonal zirconia and alpha-alumina mixture of phases. The SEM/EDS analysis confirmed the presence of aluminum in PA ceramic. In the IZ and CAZ ceramics aluminum, zirconium and cerium in grains involved by a second phase containing aluminum, silicon and lanthanum were identified. PA showed significantly higher mean Vickers hardness values (H(V)) (18.4+/-0.5GPa) compared to vitreous CAZ (10.3+/-0.2GPa) and IZ (10.6+/-0.4GPa) ceramics. Experimental Y-TZP showed significantly lower results than that of the other monophased ceramic (PA) (p<0.05) but it showed significantly higher fracture toughness (6.0+/-0.2MPam(1/2)) values when compared to the other tested ceramics (p<0.05). SIGNIFICANCE: The coprecipitation method used to synthesize zirconia powders and the adopted ceramic processing conditions led to ceramics with mechanical properties comparable to commercially available reinforced ceramic materials.