To assess the influence of calcination process on the properties of minimally processed recycled 3Y-TZP, and to compare it with its commercial counterpart.
Non-milled 3Y-TZP waste was collected, ...fragmented and ball-milled to a granulometric < 5 µm. Half of the recycled powder was calcined at 900 °C. Recycled 3Y-TZP disks were uniaxially pressed and sintered to create two recycled groups: 1) Calcined and 2) Non-calcined to be compared with a commercial CAD/CAM milled 3Y-TZP. The microstructure of experimental groups was assessed through density (n = 6), scanning electron microscopy (n = 3) and energy-dispersive X-ray spectroscopy (n = 3); and the crystalline content was evaluated through X-ray diffraction (XRD) (n = 3). Optical and mechanical properties were investigated through reflectance tests (n = 10), and Vickers hardness, fracture toughness (n = 5), and biaxial flexural strength tests (n = 16), respectively. Fractographic analysis was performed to identify fracture origin and crack propagation. Statistical analyses were performed through ANOVA followed by Tukey´s test, and by Weibull statistics.
Particle size distribution of recycled powder revealed an average diameter of ∼1.60 µm. The relative density of all experimental groups was > 98.15 % and XRD analysis exhibited a predominance of tetragonal-phase in both recycled groups, which were similar to the crystallographic pattern of the control group. Cross-section micrographs presented flaws on the non-calcined group, and a more homogeneous microstructure for the calcined and commercial groups. Commercial samples showed lower contrast-ratio and higher translucency-parameter than the recycled groups, where non-calcined presented higher translucency-parameter and lower contrast-ratio than its calcined counterpart. The commercial group presented higher fracture toughness and characteristic strength than the recycled groups. Moreover, the calcined group exhibited higher hardness, characteristic strength, and probability of survival at higher loads than the non-calcined group. Fractographic analysis depicted the presence of microstructural flaws in the non-calcined group, which may have acted as stress-raisers and led to failures at lower flexural strengths values.
The calcination process improved the microstructure, optical, and mechanical properties of the recycled 3Y-TZP.
•Effect of calcination on minimally processed recycled zirconia powder was assessed.•Calcination enhanced the microstructure, optical, and mechanical features of the recycled 3Y-TZP.•Calcination did not promote alterations to the crystalline structure of the recycled 3Y-TZP.•Calcined powder resulted in a more homogeneous microstructure.•Recycled 3Y-TZP demonstrated a potential for applications in reconstructive dentistry.
To enhance the energy absorption capacity of the sandwich structures, the foam filled composite X-core sandwich panels were fabricated by a hot-press molding technology. The bending behaviors of the ...empty and hybrid composite sandwich panels were investigated by the three-point bending tests. Analytical models and finite element models were developed to characterize the bending behaviors and the interaction effect between the foams and composite members. Generally, the specific bending modulus and strength of composite X-core sandwich structures are comparable to that of the competing cellular structures. The theoretical expressions can provide useful predictions of the bending stiffness and initial failure load, whilst the numerical models had a higher accuracy. A failure mechanism map was constructed to highlight the effect of geometry parameters on the failure modes. A minimum weight design was employed to provide a guideline for obtaining the weight-efficient hybrid composite sandwich panels.
The embrittlement of alloy 82 welds exposed to a simulated pressurised water reactor (PWR) environment was analysed and compared with that observed for cathodically hydrogen-precharged specimens. ...Similarities in mechanical behaviour, i.e. the evolution of the constitutive equations with a decrease in flow stress compared with non-precharged specimens, and in the fracture modes, with brittle zones in the outer layer, enabled us to conclude that the embrittlement observed in simulated PWR environment corresponded to a two-step hydrogen-assisted cracking mechanism. The first step corresponded to hydrogen absorption into the surface layer leading to crack initiation, and the second step to hydrogen localisation ahead of the crack tip promoting crack propagation.
•Contribution of H to low temperature embrittlement during PWR exposure of alloy 82.•Embrittlement observed in PWR environment explained by a two-step mechanism.•H uptake during the first step significant enough to promote crack initiation.•Localisation of H ahead of the crack tip promotes crack propagation.•Tensile test in air on cathodically H-charged sample representative of PWR damage.
This study aimed to compare a new multicolored rotary system with four heat-treated rotary instruments using the multimethod approach.
Three-hundred instruments of RCS Rainbow, Rotate, RaCe EVO, ...OneCurve, and ProTaper Ultimate systems were evaluated regarding their design (stereomicroscopy, scanning electron microscopy, and 3D surface scanning), metallurgy, and mechanical performance (cyclic fatigue, torsional resistance, bending and buckling resistance, and cutting ability). Unprepared surfaces after canal preparation of maxillary molars were evaluated using micro-computed tomography. Kruskal-Wallis and one-way analysis of variance post hoc Tukey tests were used for statistical comparisons (α = 5%).
Instruments exhibited variations in active blade length, number of spirals, and cross-sectional designs. RCS Rainbow showed specific phase transformation temperatures, highest bending (400.5gf) and buckling (286gf) resistance values, and lowest mean angle of rotation (529°) (P < .05). OneCurve exhibited superior cutting ability (8.4 mm) and longer time to fracture (112s). RaCe EVO displayed the lowest time to fracture (51s), maximum torque (1.2 N.cm), buckling (174gf), and bending resistance (261gf) values (P < .05). ProTaper Ultimate showed the highest torque (1.6 N.cm) and angle of rotation (611°) (P < .05), while its bending load (262gf) was comparable to RaCe EVO (P > .05). Rotate instrument showed intermediate values in the mechanical tests. No difference was observed regarding the unprepared canal surfaces (P > .05)
RCS Rainbow demonstrates a trade-off between flexibility and other mechanical properties. Its dimensions exceeded those of other instruments, affording it higher torque resistance, yet concurrently reducing its flexibility, angle of rotation, and cutting ability. OneCurve stands out as a well-balanced choice by integrating geometric design and mechanical performance.
Abstract
Although welcomed and used as storage materials by many museums, camphor wood shows a potential risk to museum collections due to its strong smell. Camphor wood was proved harmful to metals ...in the author’s previous studies, but since the last study about camphor wood reported by the author, the camphor wood samples have not experienced the Oddy test again for two years, so their harm to metals is unknown at the current stage. Meanwhile, there is no standard or specific method for learning the materials’ effect on organics. The present work focuses on the above situation. Camphor wood samples of different species and aged for different years were tested in this study. Their effect on metals was assessed by performing the Oddy test. On the other hand, a series of mechanical tests were conducted to learn the camphor wood samples’ effect on paper samples commonly used in Chinese calligraphy and painting and the corresponding restoration. The results show that the camphor wood samples are still significantly volatile and harmful to both metal and paper. This work would be meaningful to museum curators and conservators as a reference for making correct judgments when camphor wood is included in the potential material list.
In the last few decades nanofibers have been developed and introduced in a vast number of industrial and research applications. One of their most effective use is as interleaved reinforcement for ...composite laminate materials against delamination. Nanofibrous mats have the ideal morphology to be embedded between two plies of a laminate, and a vast and deep research has been carried out investigating their effect on the global behaviour of a composite laminate.
This review is the first of its kind to date which presents a detailed state-of-the-art on the effect of nanofibrous interleaves into composite laminates with focus on the mechanical performances and behaviours of nanomodified materials. A detailed description of the working mechanisms of the nanointerleave under different load cases is presented, and a comparative analysis between papers in literature will provide readers with a powerful tool to understand and use nanofibers for reinforcing purposes.
We propose a new approach for data-driven automated discovery of isotropic hyperelastic constitutive laws. The approach is unsupervised, i.e., it requires no stress data but only displacement and ...global force data, which are realistically available through mechanical testing and digital image correlation techniques; it delivers interpretable models, i.e., models that are embodied by parsimonious mathematical expressions discovered through sparse regression of a large catalogue of candidate functions; it is one-shot, i.e., discovery only needs one experiment — but can use more if available. The problem of unsupervised discovery is solved by enforcing equilibrium constraints in the bulk and at the loaded boundary of the domain. Sparsity of the solution is achieved by ℓp regularization combined with thresholding, which calls for a non-linear optimization scheme. The ensuing fully automated algorithm leverages physics-based constraints for the automatic determination of the penalty parameter in the regularization term. Using numerically generated data including artificial noise, we demonstrate the ability of the approach to accurately discover five hyperelastic models of different complexity. We also show that, if a “true” feature is missing in the function library, the proposed approach is able to surrogate it in such a way that the actual response is still accurately predicted.
•We propose a new approach for data-driven automated discovery of constitutive laws.•The approach is unsupervised, i.e. it needs only displacement and global force data.•The approach is interpretable, i.e. it discovers parsimonious laws through sparse regression.•The approach is one-shot, i.e. it only needs one experimental dataset.•Sparse regression is empowered by domain knowledge.
Abstract
Constructing stable electrodes which function over long timescales at large current density is essential for the industrial realization and implementation of water electrolysis. However, ...rapid gas bubble detachment at large current density usually results in peeling-off of electrocatalysts and performance degradation, especially for long term operations. Here we construct a mechanically-stable, all-metal, and highly active CuMo
6
S
8
/Cu electrode by in-situ reaction between MoS
2
and Cu. The Chevrel phase electrode exhibits strong binding at the electrocatalyst-support interface with weak adhesion at electrocatalyst-bubble interface, in addition to fast hydrogen evolution and charge transfer kinetics. These features facilitate the achievement of large current density of 2500 mA cm
−2
at a small overpotential of 334 mV which operate stably at 2500 mA cm
−2
for over 100 h. In-situ total internal reflection imaging at micrometer level and mechanical tests disclose the relationships of two interfacial forces and performance of electrocatalysts. This dual interfacial engineering strategy can be extended to construct stable and high-performance electrodes for other gas-involving reactions.
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