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To evaluate the effect of the ceramic processing and aging method on the microstructure, optical, and mechanical properties of a third generation ultra-translucent zirconia, yttria ...partially stabilized zirconia (5Y-PSZ).
In-house discs were obtained through uniaxial and isostatic pressing an ultra-translucent Y-PSZ powder and sintering at 1450 °C for 2 h. As control, a commercial disc was milled from pre-sintered blocks fabricated with the same 5Y-PSZ powder through isostatic pressing and sintered under the same protocol. Discs were allocated into three groups according to aging condition as immediate (non-aged) and aged using autoclave or hydrothermal reactor at 134ºC for 20 h at 2.2 bar. Crystalline content and microstructure were evaluated using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Optical properties were determined using reflectance data to calculate the contrast ratio (CR) and translucency parameter (TP). Mechanical properties were assessed by Vickers hardness, fracture toughness and biaxial flexural strength tests.
XRD spectra revealed a prevalence of cubic (70%) and tetragonal (30%) phases, and the SEM images showed a dense fully crystalline ceramic matrix for both materials. Crystalline content and microstructure of the in-house and commercial 5Y-PSZs were not affected by aging. As-sintered 5Y-PSZs demonstrated similar CR (~0.6) and TP (~18) values, as well as Vickers hardness (~14 GPa) and fracture toughness (~3.8 Mpa.m1/2), with no significant alteration after both aging methods. In-house and commercial Y-PSZs Weibull moduli ranged from 3.0 to 5.3. 5Y-PSZ processing methods resulted in similar characteristic strength after sintering (592–618 Mpa). While commercial 5Y-PSZ showed no significant influence of aging on strength, hydrothermal reactor aging significantly decreased the in-house Y-PSZ characteristic strength (474 Mpa). Both 5Y-PSZs demonstrated high reliability up to 300-Mpa strength missions, with no detrimental effect of aging (88–100%).
Irrespective of the processing method, ultra-translucent 5Y-PSZ showed high aging resistance and translucency stability, as well as strength corresponding to the indication up to short-span anterior prostheses.
Highlights • The feldspathic and polymer infiltrated ceramics (Enamic) have completely different microstructures. The former present crystals while the latter is amorphous. • The lithium dissilicate ...and the Zirconia-reinforced lithium silicate presented greater susceptibility to stress corrosion than the other ceramics. • The zirconia present in the lithium silicate is tetragonal zirconia.
•Fully crystallized materials presented higher hardness and flexural strength.•The harder microstructure created after firing led to a difficulty in polishing.•After firing, zirconia was dispersed in ...the glass phase and decreased in size.
The aim of this study was to characterize the microstructure of two zirconia-reinforced lithium silicate (ZLS) glass-ceramics and evaluate their mechanical properties before and after the crystallization firing process (CFP).
Field emission-scanning electron microscope (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were performed for microstructural characterization. To evaluate the pattern of crystallization and the molecular composition of ZLS glass-ceramics, was used X-ray diffraction (XRD). Vickers hardness, fracture toughness by the indentation method, and biaxial flexural strength were also measured. One hundred and forty ceramic discs were produced (diameter=12mm; thickness=1.2mm) and allocated among four groups (n=30): Sfir, Sunf-ZLS Vita Suprinity; and Cfir and Cunf-ZLS Celtra Duo; fired and unfired, respectively. Statistical analysis was performed and Weibull failure probabilities were calculated.
Cfir showed the highest characteristic strength (251.25MPa) and hardness (693.333±10.85GPa). Conversely, Sunf presented the lowest characteristic strength (106.95MPa) and significantly lowest hardness (597.533±33.97GPa). According to Weibull analysis, Sunf had the highest structural reliability (m=7.07), while Sfir presented the lowest (m=5.38). The CFP was necessary to crystallize zirconia in the partially crystallized ZLS glass-ceramics. Sfir had a lower percentage of crystallized zirconia than did Cfir. Fractographic analyses showed that all failures initiated from an inherent critical defect in Sunf and from processing defects in the remaining groups.
The CFP had a direct influence on the flexural strength and microstructural characteristics of both ZLS materials.
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•FRC contained epoxy resin matrix with 30% inorganic compound and 45% glass fiber.•Continuous regular glass fibers were parallelly distributed in a bidirectional way.•FRC FDPs showed ...high reliability for a masticatory load in the posterior region.•Extended FRC framework resulted in higher reliability than conventional framework.•Veneering composite cohesive or adhesive fractures were the chief failure modes.
To characterize the physicochemical and mechanical properties of a milled fiber-reinforced composite (FRC) for implant-supported fixed dental prostheses (FDPs).
For FRC characterization, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction, Fourier-transformed infrared spectrometry, simultaneous thermogravimetric analysis and differential scanning calorimetry were performed. For fatigue testing, 3-unit FRC frameworks were fabricated with conventional (9 mm2 connector area) and modified designs (12 mm2 connector area and 2.5 mm-height lingual extension). A hybrid resin composite was veneered onto the frameworks. FDPs were subjected to step-stress accelerated-life fatigue testing until fracture or suspension. Use level probability Weibull curves at 300 N were plotted and the reliability for 100,000 cycles at 300, 600 and 800 N was calculated. Fractographic analysis was performed by stereomicroscope and SEM.
The FRC consisted of an epoxy resin (∼25%) matrix reinforced with inorganic particles and glass fibers (∼75%). Multi-layer continuous regular-geometry fibers were densely arranged in a parallel and bidirectional fashion in the resin matrix. Fatigue analysis demonstrated high probability of survival (99%) for FDPs at 300 N, irrespective of framework design. Conventional FDPs showed a progressive decrease in the reliability at 600 (84%) and 800 N (19%), whereas modified FDPs reliability significantly reduced only at 800 N (75%). The chief failure modes for FRC FDPs were cohesive fracture of the veneering composite on lower loads and adhesive fracture of the veneering composite at higher loads.
Milled epoxy resin matrix reinforced with glass fibers composite resulted in high probability of survival in the implant-supported prosthesis scenario.
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The effect of synthesis medium (ethanol and water) on ZnO/Carbon xerogel photocatalysts was studied in order to increase the efficiency of the photocatalytic degradation of ...4-chlorophenol and bisphenol A. The use of carbon xerogel is justified due to its excellent electrical conductivity, high surface area and porosity. The effect of the carbon content in the composites was also evaluated. The composites were characterized using scanning electron microscopy, transmission electron microscopy, dispersive energy spectrometry, X-ray diffractometry, infrared spectroscopy, nitrogen isotherms, differential scanning calorimetry, thermogravimetry, electrochemical impedance spectroscopy and Raman spectroscopy. All materials present the hexagonal crystalline structure of zinc oxide. Materials without carbon in their composition also presented the zinc hydroxychloride monohydrate phase. X-ray diffractograms and bandgap values obtained confirm the incorporation of carbon in the crystalline structure of zinc oxide. Materials produced in ethanol medium have lower values of crystallite and particle size, as well as higher graphite contents in their composition and higher specific surface area. All materials displayed photocatalytic activity when subjected to visible and solar radiation. Materials produced in ethanol displayed superior performance when compared to those synthesized in aqueous medium. The maximum values found for the degradation of 4-chlorophenol and bisphenol A were 88% and 78%, respectively, after 5 h. The mechanism of photocatalysis is strongly influenced by the generation of hydroxyl radicals and the materials were stable for three cycles of reuse. The electrochemical impedance spectroscopy confirms that the charge separation efficiency was optimized in the presence of the carbon xerogel and when the composite was produced in ethanol medium.
Purpose: This paper presents the concept of an Employee Suggestion System (ESS) that integrates a strategy originated from Neuro-Linguistic Programming with application in Coaching (Disney Strategy) ...to face the human challenges of Industry 4.0.Design/methodology/approach: A four-phase methodology was followed, starting with a systematic literature review of the ESS to obtain a theoretical perspective about this concept and its characteristics. Subsequently, 30 interviews were carried out to recognize the ESSs of three partner companies and, as well as to perceive the receptivity of the new concept of ESS. Finally, the concept of the system was modelled, prototyped and tested and combines the Japanese (Kaizen Teian) and American ESS (Kaizen Teian adapted to the western industry) approaches.Findings: Given the existing systems in organizations, the platform presented brings more maturity to the suggestions made (through the Disney strategy applied in Coaching), greater visibility of their status and evaluation, and greater promotion of workforce engagement (through the promotion of voice behaviour). At the same time, it supports the collection of tacit ideas from employees, preserving organizational knowledge and, therefore, a source of competitive advantage.Originality/value: This paper presents a digital tool with Lean origins, which includes Coaching principles, essential in empowering the workforce (through the voice behaviour) and preserving organizational knowledge. It is a platform built in a way adapted to today's Lean shop floor and intends to prove itself as a resource to promote happy, engaged and committed employees.
The aim of this study was the development of low-cost tannin-formaldehyde xerogel/TiO
2
(XTi-w) and carbon xerogel/TiO
2
(XTiC-w) photocatalysts. The materials used as precursors were recycled ...titanium scraps and black wattle tannin extract, highlighting the low-cost approach employed in the synthesis. The materials were characterized by diffuse reflectance spectroscopy, scanning electron microscopy, dispersive energy spectrophotometry, X-ray diffractometry, infrared and Raman spectroscopy. X-ray diffractometry showed that the XTiC-w have tetragonal crystalline structure (anatase), whereas the XTi-w has an amorphous structure. The Raman and infrared analysis also showed the presence of titanium dioxide in the composition of both XTi-w and XTiC-w. XTi-w and XTiC-w showed photocatalytic activity at the visible wavelength. Titanium dioxide displayed no photocatalytic activity at the visible wavelength. The XTi-60 composite displayed the highest efficiency in the removal of the methylene blue from the system, as well as good reusability properties. The radicals with higher influence in the photocatalytic reaction mechanism are the photo generated electron and the singlet oxygen molecule. The effect of the heat treatment is negative on the photocatalytic properties of the hybrids produced, due to the removal of acid sites, adsorbed water and OH surface groups.
The graphical abstract displays an illustration of the materials obtained in this work and their respective efficiency in the adsorption and photocatalytic degradation of methylene blue under visible light.
Highlights
Hybrids were produced using low-cost materials, such as titanium scraps and tannin
Both hybrid materials showed photocatalytic activity at the visible wavelength
Heat treatment is negative on the photocatalytic properties of the hybrids
Reaction mechanism is controlled by trapped electrons and singlet oxygen molecules
Biomaterials may be useful in filling lost bone portions in order to restore balance and improve bone regeneration. The objective of this study was to produce polycaprolactone (PCL) membranes ...combined with two types of bioglass (Sol–Gel and melt-quenched) and determine their physical and biological properties. Membranes were produced through electrospinning. This study presented three experimental groups: pure PCL membranes, PCL-Melt-Bioglass and PCL-Sol-gel-Bioglass. Membranes were characterized using Scanning Electron Microscopy, Fourier Transform Infrared Spectrophotometry (FTIR), Energy-Dispersive Spectroscopy and Zeta Potential. The following in vitro tests were performed: MTT assay, alkaline phosphatase activity, total protein content and mineralization nodules. Twenty-four male rats were used to observe biological performance through radiographic, fracture energy, histological and histomorphometric analyses. The physical and chemical analysis results showed success in manufacturing bioactive membranes which significantly enhanced cell viability and osteoblast differentiation. The new formed bone from the in vivo experiment was similar to that observed in the control group. In conclusion, the electrospinning enabled preparing PCL membranes with bioglass incorporated into the structure and onto the surface of PCL fibers. The microstructure of the PCL membranes was influenced by the bioglass production method. Both bioglasses seem to be promising biomaterials to improve bone tissue regeneration when incorporated into PCL.
Calcium silicate-based cements have diverse applications in endodontics. This study aimed to evaluate the antibiofilm action, biocompatibility, morphological structure, chemical composition and ...radiopacity of Five Mineral Oxides (5MO), Mineral Trioxide Aggregate Repair High Plasticity (MTA Repair HP), and Mineral Trioxide Aggregate (MTA) cements. MTT analysis was used to test the antibiofilm action of these cements against five anaerobic microorganisms, and test their biocompatibility with mouse macrophage (RAW 264.7) and osteoblasts (MG-63) cultures. Their morphological structure and chemical composition were evaluated by scanning electron microscopy (SEM) coupled to energy dispersion X-ray spectroscopy (EDX), and the phase analysis was performed by X-ray diffraction (XRD). Conventional radiography was used to assess the radiopacity of the cements. 5MO, MTA Repair HP and MTA were effective against Porphyromonas gingivalis, Parvimonas micra, Fusobacterium nucleatum and Prevotella intermedia, they were biocompatible with macrophages and osteoblasts after 5 min of contact, and they had adequate radiopacity to be used clinically. Bismuth oxide (Bi2O3) is used as a radiopacifier in MTA and 5MO, and calcium tungstate, in MTA Repair HP. Titanium dioxide (TiO
) (ANATASE) is responsible for the antimicrobial action and biocompatibility of 5MO.
Super hydrophilic scaffolds of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with 3 wt % of acetylated (CNC-Ac) and PEGylated (CNC-PEG) cellulose nanocrystals (CNC) were prepared. PHBV, ...PHBV/CNC-Ac, and PHBV/CNC-PEG scaffolds were characterized with respect to their morphology by scanning electron microscopy (SEM) and X-ray microtomography. The crystallinity was evaluated by differential scanning calorimetry (DSC) and the mechanical properties by uniaxial compression tests. The presence of residual solvent was identified by gas chromatography (GC), wettability measured by static contact angle and aqueous adsorption by gravimetry. All the scaffolds showed porous morphology, being that, for neat PHBV the morphology was more regular with oriented pores. The porosity was reduced by 26% with the introduction of CNC-Ac and CNC-PEG, and the compression modulus increased by 25% and 72% for PHBV/CNC-Ac and PHBV/CNC-PEG scaffolds, respectively, compared to neat PHBV. Even with lower porosities, PHBV/CNC-Ac and PHBV/CNC-PEG adsorbed 16% and 67% more water than PHBV scaffold, following the intraparticle diffusion model for all the samples. No residual solvents were found and the crystallinity was slightly increased upon addition of CNC-Ac and CNC-PEG. Therefore, the addition of CNC-Ac and CNC-PEG can improve both compressive modulus and water uptake, turning PHBV nanocomposite scaffolds suitable for tissue engineering applications.
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•Super hydrophilic scaffolds of PHBV with functionalized cellulose nanocrystals were produced.•The addition of functionalized cellulose nanocrystals enhanced not only the water uptake, but also the compression modulus.•For all the conditions, porous and with no residual solvent scaffolds were obtained.•Scaffolds with reinforced mechanical and improved water adsorption properties were described.
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