Interfacial Zone Research Articles

Mechanical characterization of recycled-PET fiber reinforced mortar composites treated with nano-SiO2 and mixed with seawater

The study investigated the use of polyethylene terephthalate (rPET) fibers for strengthening construction materials. The addition of 0.5 vol% rPET fibers to mortar was studied, but the smooth surface of rPET resulted in weak bonds with the mortar matrix, leading to a decreased interfacial transfer zone (ITZ) compared to the surrounding matrix. To address this issue, nano-particle and NaOH hydrolysis were used to improve the ITZ bond strength and frictional behavior. Additionally, surface treatment of rPET using NaOH and silane coating was performed to enhance the hydrophilicity and bond strength with the matrix. The effects of seawater on the material were also studied using XRD. Additionally, cemGEMS analysis was also conducted. The SEM was used to observe the degree of bonding at the ITZ between rPET and the mortar matrix. The study showed that adding 0.5 vol% of rPET fibers had a significant impact on the tensile strength and fracture energy of mortar, and the fiber dispersibility was a crucial factor in controlling its mechanical properties. The low-cost recycled PET fibers were also found to be effective as a reinforcing agent in seawater-mixed mortar for marine applications, increasing the mortar's fracture energy by 188–802%. Therefore, these fibers can be used in coastal structures requiring impact-resistant non-metallic materials, such as wave-dissipating concrete blocks or marine concrete structures reinforced with non-corrosive materials like FRP.

ULTRA-WIDEFIELD OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IN MILD FAMILIAL EXUDATIVE VITREORETINOPATHY.

To investigate ultra-widefield optical coherence tomography angiography (UWF-OCTA) to detect and evaluate mild familial exudative vitreoretinopathy and compare the detective ratio of UWF-OCTA with ultra-widefield scanning laser ophthalmoscopy and ultra-widefield fluorescein angiography. The patients with familial exudative vitreoretinopathy were included in this study. UWF-OCTA, using a 24- × 20-mm montage, was performed for all patients. All images were independently tested for the presence of familial exudative vitreoretinopathy-associated lesions. Statistical analysis was performed with SPSS V.24.0. Forty-six eyes of 26 participants were included in the study. Ultra-widefield optical coherence tomography angiography was found to be greatly superior to ultra-widefield scanning laser ophthalmoscopy in detecting peripheral retinal vascular abnormality ( P < 0.001) and peripheral retinal avascular zone ( P < 0.001). The detection rates of peripheral retinal vascular abnormality, peripheral retinal avascular zone, retinal neovascularization, macular ectopia, and temporal midperipheral vitreoretinal interface abnormality were comparable with ultra-widefield fluorescein angiography images ( P > 0.05). Furthermore, vitreoretinal traction (17/46, 37%) and small foveal avascular zone (17/46, 37%) were detected effectively on UWF-OCTA. Ultra-widefield optical coherence tomography angiography is a reliable noninvasive tool to detect familial exudative vitreoretinopathy lesions, especially in mild patients or asymptomatic family members. The unique manifestation of UWF-OCTA offers an alternative to ultra-widefield fluorescein angiography for the screening and diagnosis of FEVR.

Effects of fluorine on dynamic reaction interfaces in hydrothermal feldspar alteration

Fluid-induced mineral reactions exert an important control on the physico-chemical properties of the crust and hydrothermal plumbing systems. Feldspars are the most abundant minerals in the Earth's crust and a major host of the main cations found in geofluids (Na, K, Ca). In previous work, we discovered that K-feldspar-albite-sanidine zonation textures developed dynamically when sanidine ((K,Na)AlSi3O8) was reacted with NaCl or NaF in H216O- and H218O-enriched solutions at 600 °C and 2 kbar in a closed system. Based on a detailed SEM and TEM characterisation, the present study aims to constrain the reaction mechanism and the effect of fluorine on reaction kinetics and overall reaction textures in alkali feldspar replacement reaction interfaces. Replacement of high-sanidine (Sa) by albite (Ab) and/or K-feldspar (Kfs) proceeded via an interface-coupled dissolution-reprecipitation reaction, with the products preserving the crystallographic orientation of the parent Sa in both NaCl- and NaF-bearing solutions. Mineral interfaces with different micro-textures were observed depending on the nature of the interface (Ab-Sa, Kfs-Ab, Kfs-Sa) and whether the reaction occurred in NaCl-only or NaF-bearing solutions. Abundant amorphous domains (25–50 nm thick) occur both within Ab and at Ab-Sa and Kfs-Ab interfaces formed in NaF-bearing solutions. At the Kfs-Sa interface formed in NaCl-only solutions, a complex interfacial zone characterised by a high density of defects may represent sealed fluid pathways. These results reveal that the nature of the reaction interface depends on both mineral properties, in particular microtextures (i.e. polysynthetic twinning in Ab); and solution chemistry; this directly affects porosity development, the chemical environment at the interface, and chemical exchanges between the reaction front and the bulk solution. Fluorine aids the formation of amorphous layers that modify nucleation mechanisms; and facilitates element transport by forming Na-Si-Al-fluoride complexes, resulting in accelerated reaction rates relative to chloride-solutions. These nm- to μm-level processes contribute to efficient coupling between fluid-flow and mass transfer, explaining why sodic and potassic alteration associated with metal and fluid transport in some of the world's largest ore deposits can develop extensively, and subsequently access metals locked within silicate mineral assemblages.

Could secondary flows have made possible the cross-strait transport and explosive invasion of Rugulopteryx okamurae algae in the Strait of Gibraltar?

Presently, the Strait of Gibraltar is undergoing an unprecedented invasion of the alien alga Rugulopteryx okamurae of North Pacific origin. According to the scarce literature, the algae first settled in the south shore, probably following commercial exchanges with French ports where it was accidentally introduced together with Japanese oysters imported for mariculture. There is no certainty, however, that the algae first colonized the south shore of the Strait and, from there, spread to the north. It could well have been the opposite. Whatever the case, it spread all over the Strait and surrounding areas with amazing rapidity. Human-mediated vectors (algae attached to ship hulls or fishing nets, for example) can be behind the spread from the shore initially settled to the algae-free shore on the opposite side. But it could also have happened by means of hydrodynamic processes without direct human intervention. This possibility is assessed in this paper by revisiting historical current meter profiles collected in the Strait of Gibraltar searching for secondary cross-strait flows. All the stations present an intermediate layer of northward cross-strait velocity near the interface of the mean baroclinic exchange along with a surface layer above of southward velocity, whose lower part also overlaps the interface zone. The first one would back the south-to-north transport of algal fragments, the second one, the north-to south. In both cases, algae must reach the depth of the interface. The vertical velocity field in the area, which far exceeds the small sedimentation velocity of the algae, allows their vertical displacements throughout the water column. Its endurance to survive under the weak or no light conditions that will prevail during the cross-strait transport and its capability of reactivating the metabolism after this unfavorable period, offers chances for colonizing the opposite shore. Therefore, the propagation of the algae by hydrodynamic processes, without human intervention, cannot be ruled out.

Acoustic effect on the joint quality and process of friction stir lap welding of aluminum to steel

To gain a high strength-to-weight ratio and economic viability for multiple industrial applications, the Al and steel need to be joined successfully. In the present work, we used conventional friction stir welding (FSW) and ultrasonic vibration enhanced friction stir welding (UVeFSW) techniques to obtain high-strength industrial-grade dissimilar joints of Al and steel. The effects of acoustic energy on the joint quality and welding process were investigated. Macrographs of the joints revealed that ultrasonic vibrations could effectively promote the material flow and increase the mixing degree and width of the Al/steel interface. Steel strips' fragmentation and intermixing with the Al substrate were enhanced under ultrasonic effects. The tool torque, axial force, and spindle power were significantly decreased with ultrasonic vibration. Acoustic assistance was found beneficial to increase the joints’ failure load and change the fracture mechanism. The microhardness of acoustically treated regions was found to be higher compared to its counterparts. The thinning of the brittle intermetallic compounds (IMCs) layer at the interface of the UVeFSW joint was caused by decreased peak temperature during welding. In UVeFSW, when the welding speed was 50 mm/min, the maximum failure load of the joint was obtained under the joint action of the macro interlocks (interface zone), the thinner IMCs layer, and the micro interlocks (laminated structure). When the welding speed was 100 mm/min, the failure load of the joint was improved by 25.8% compared with conventional FSW.

Corrosion Resistance and Titanium Ion Release of Hybrid Dental Implants.

One of the strategies for the fight against peri-implantitis is the fabrication of titanium dental implants with the part close to the neck without roughness. It is well known that roughness favors osseointegration but hinders the formation of biofilm. Implants with this type of structure are called hybrid dental implants, which sacrifice better coronal osseointegration for a smooth surface that hinders bacterial colonization. In this contribution, we have studied the corrosion resistance and the release of titanium ions to the medium of smooth (L), hybrid (H), and rough (R) dental implants. All implants were identical in design. Roughness was determined with an optical interferometer and residual stresses were determined for each surface by X-ray diffraction using the Bragg-Bentano technique. Corrosion studies were carried out with a Voltalab PGZ301 potentiostat, using Hank's solution as an electrolyte at a temperature of 37 °C. Open-circuit potentials (Eocp), corrosion potential (Ecorr), and current density (icorr) were determined. Implant surfaces were observed by JEOL 5410 scanning electron microscopy. Finally, for each of the different dental implants, the release of ions into Hank's solution at 37 °C at 1, 7, 14, and 30 days of immersion was determined by ICP-MS. The results, as expected, show a higher roughness of R with respect to L and compressive residual stresses of -201.2 MPa and -20.2 MPa, respectively. These differences in residual stresses create a potential difference in the H implant corresponding to Eocp of -186.4 mV higher than for the L and R of -200.9 and -192.2 mV, respectively. The corrosion potentials and current intensity are also higher for the H implants (-223 mV and 0.069 μA/mm2) with respect to the L (-280 mV and 0.014 μA/mm2 and R (-273 mV and 0.019 μA/mm2). Scanning electron microscopy revealed pitting in the interface zone of the H implants and no pitting in the L and R dental implants. The titanium ion release values to the medium are higher in the R implants due to their higher specific surface area compared to the H and L implants. The maximum values obtained are low, not exceeding 6 ppb in 30 days.

Multiscale mechanical evolution of the interface between self-compacting concrete and steam-cured concrete

The long-term performance of the bonding interface between self-compacting concrete (SCC) and steam-cured concrete is crucial to the safety and reliability of high-speed railway structures. In this study, During the entire curing cycle, the macroscopic mechanical properties of the bonding interface between SCC and steam-cured concrete were studied. The entire process of interfacial bonding failure at various curing ages was monitored by an acoustic emission test. The failure modes were determined after the splitting tensile test based on 3D laser scanning. The evolution mechanism of mechanical properties was discussed from the perspective of the microstructure of the bonding interface. Results indicate that the time-dependent law of the splitting tensile strength of the bonding interface presented three stages in the investigated curing age (0–90 days). The time-varying law prediction model of the mechanical properties was established based on the time-varying law prediction model of concrete compressive strength. The microhardness of the bonding interface zone presented a significant gradient change at an early age (1–7 days).

Gradient microstructure and strain field at interfacial zone between cement-based repair and concrete substrate

For concrete repair, due to the discontinuity of the interface microstructure, stress concentration easily occurs at the interface between repair material and substrate, which leads to debonding failure. In this study, interface with gradient microstructure between cement-based repair and substrate was built up by using waterborne epoxy resin (WER) to modify the repair material. 1H low field nuclear magnetic resonance (1H LF-NMR) tests showed that WER in the cement-based repair permeated into the substrate and distributed in gradient along the permeating direction. The permeating depth of WER increased from 6 mm to 10.5 mm when the WER dosage in the repair increased from 5% to 20% (by weight of cement). The porosity at the zone below the interface in the substrate decreased by more than 40% and the micromechanical properties were thereby obviously improved, when the repair mortar was modified with 15% WER. As a result, the strain concentration at the interfacial zone was significantly mitigated by the WER and the bonding strength was enhanced by more than 80%.

A surpassingly stiff yet lossy multiscale nanocomposite inspired by bio-architecture

Common microstructural features inspired by bones, including the moduli-mismatching interface and the intramolecular dangling chains, are employed in designing and fabricating our bio-inspired nanocomposite in order to defeat the conflict of stiffness versus damping. The epoxy vitrimer is itself chosen to construct the intramolecular dangling chains, and then mixed with multi-walled carbon nanotubes (MWCNTs) to form the moduli-mismatching interface. Experimental and theoretical research is performed to elucidate the role of the common microstructural features on the damping of our bio-inspired nanocomposite. Dangling chains improve damping, although they are negative for moduli. The high modulus of MWCNTs not only enlarges the modulus of composites but also causes a stress jump phenomenon at the interfacial zone, which induces the irreversible production process of inelastic strain at the interface to dissipate mechanical energy. The loss modulus of MWCNTs-reinforced epoxy nanocomposites is found to reach as much as 738 MPa, which exceeds the limit of 600 MPa for traditional materials (including bones), although the common microstructural features are inspired by bones. The synergistic enhancement mechanism caused by the intramolecular dangling chains and the moduli-mismatching interface is responsible for the surpassingly stiff yet lossy performances.

Evidence-based uncertainty quantification for bending properties of bimetal composites

Bimetal or laminated metal composites consisting of several metal or alloy layers can efficiently absorb the advantageous properties of each metal when utilised as raw materials for future remanufacturing. Their mechanical response characteristics and failure modes face uncertain challenges during the processing owing to the existence of heterogenous interfacial transition zones between layers. This work aims to study the uncertainty quantification in bending processing of a novel bimetal composite as a result of uncertain interfacial zones using an efficient evidence-based reliability analysis method. An analytical model for bending characteristics of bimetal composite was first established based on the deterministic material properties of each component layer, and it was employed to quantitatively analyse the bending uncertainty properties of 2205 duplex stainless steel/AH36 carbon steel bimetal composite (2205/AH36 BC) considering the epistemic uncertainty in geometric dimensions and mechanical properties of component 2205 and AH36 layers. The variation ranges of tangential stress and bending moment along the thickness direction of composite during bending process were effectively estimated, and the confidence level of each possible in the corresponding upper and lower boundaries was given for the tangential stress at each position. The analysis results illustrated that the uncertainty quantification for bending deformation properties of bimetal composite can more comprehensively understand the mechanical behaviors of composite, and provide an effective guidance for the forming fabrication of bimetal composite structure.

Epithelial-mesenchymal Transition Factor and Its Association With Mammographic Density and Breast Cancer Prognosis.

The tumor microenvironment influences tumor progression, invasion, and metastasis. This study determined the expression levels of epithelial-mesenchymal transition (EMT) factors according to zone and their correlation with mammographic breast density and investigated the prognostic value of EMT factors. The clinical and pathological data of invasive carcinoma and ductal carcinoma in situ were reviewed. Primary breast tissue samples were evaluated using immunohistochemistry (IHC) staining of the EMT-associated markers, including α-SMA, vimentin, MMP-9, and CD34. The expression levels were analyzed in three areas: the tumor center, interface, and distal zones. EMT factors were correlated with mammographic breast density and oncologic outcomes. An overall EMT phenotype conversion from positive to negative was seen in 55.7% of α-SMA- and 34.4% of MMP-9-positive cells between the tumor center and interface zones, which was significantly different (p<0.05). Most changes in EMT expression from the center to the distal zone were from positive to negative, but 23.0% of CD34-expressing cells showed negative to positive conversion. The proportion of α-SMA, vimentin, and MMP-9 expression was higher in the non-dense breast group compared to the dense breast group in the interface and distal zones (p<0.05). CD34 expression in the distal zone was an independent favorable prognostic factor for disease-free survival (p=0.039). The differential expression of EMT markers in each zone suggests heterogeneous cancer cell populations within each zone of breast cancer. EMT factor expression can also interplay between breast density stroma and geographical tumor zone.

Mechanical properties and durability of injected SCC panels by epoxy against freezing and thawing

Repairing cracks in concrete structures exposed to freezing and thawing cycles by injecting epoxy resin and the main factors affecting it, such as epoxy viscosity, crack width, and the crack's moisture content, has been studied in a few research.This paper utilized commercial epoxy resins with high, medium, and low viscosities to inject through simulated cracks. In addition, repair methods were tested and evaluated by injecting epoxy resins in dry, damp, wet, and water-filled conditions. Furthermore, two crack widths (0.5 and 0.8 mm) were simulated on the specimens, and the effects of the repairing materials' thickness on the rehabilitation success were examined. The specimens’ durability with 24 cycles of freezing and thawing was investigated.Results demonstrate that water's presence in different situations, especially the water-filled ones in the interfacial zone, deteriorates the bond characteristics; Contrastly, the results were better in the wet situation. It can be concluded that injecting in the dry situation is optimized. The results showed that curing in lower temperatures takes longer than in higher temperatures. Moreover, a correlation was observed between the viscosity and its effect on tensile bond strength and actual shear strength in the slant shear test. It was found that the low-viscosity resin showed better performance than the high-viscosity resin overall. Moreover, the low-viscosity resin achieved 25% more shear strength in the slant shear test than the high-viscosity. In the freezing and thawing cycles, the injection was stable only in dry cracks, and in other moist conditions, the samples failed the freezing and thawing cycles.

Crystallographic and TEM Features of a TBC/Ti2AlC MAX Phase Interface after 1300 °C Burner Rig Oxidation

A FIB/STEM interfacial study was performed on a TBC/Ti2AlC MAX phase system, oxidized in an aggressive burner rig test (Mach 0.3 at 1300 °C for 500 h). The 7YSZ TBC, α-Al2O3 TGO, and MAXthal 211TM Ti2AlC base were variously characterized by TEM/STEM, EDS, SADP, and HRTEM. The YSZ was a mix of “clean” featureless and “faulted” high contrast grains. The latter exhibited ferro-elastic domains of high Y content tetragonal t″ variants. No martensite was observed. The TGO was essentially a duplex α-Al2O3 structure of inner columnar plus outer equiaxed grains. It maintained a perfectly intact, clean interface with the Ti2AlC substrate. The Ti2AlC substrate exhibited no interfacial Al-depletion zone but, rather, numerous faults along the basal plane of the hexagonal structure. These are believed to offer a means of depleting Al by forming crystallographic, low-Al planar defects, proposed as Ti2.5AlC1.5. These characterizations support and augment prior optical, SEM, and XRD findings that demonstrated remarkable durability for the YSZ/Ti2AlC MAX phase system in aggressive burner tests.

An atomistic study of plastic deformation of SmCo5 by amorphous shear bands

Recently, SmCo5 was found to be capable of forming amorphous shear bands to induce dislocation-free plastic deformation at large strains. The formation of shear band is energetically more favorable compared to cracking and the small density variation in shear bands is not likely to induce high local stress that assists crack opening. However, the related mechanism of crystalline-to-amorphous transition during shear-band formation at the atomic level remains unclear. In this paper, the shear deformation of SmCo5 is investigated by molecular dynamics simulations and we discuss the behavior of shear-band formation by exploring the atomic packing in the interfacial zone between crystal matrix and shear band. The stress-strain curves of SmCo5 show anisotropy with respect to formation of amorphous shear band. The analysis of atomic packing indicates that the behavior of Sm is critical to the atomistic amorphization path and thus accounts for the mechanical anisotropy of the material. Temperature calculations show that the material is not subject to shear melting during deformation that would otherwise lead to embrittlement.

Ex vivo demonstration of canine corneal pre-Descemet’s anatomy using pneumodissection as for the big bubble technique for deep anterior lamellar keratoplasty

The recent discovery and characterization of pre-Descemet’s layer (PDL; also termed the Dua’s layer or the Dua-Fine layer) has advanced the understanding of various posterior corneal pathologies and surgeries in human. This study aimed to characterize the ultrastructure of the posterior stroma and interfacial zone of Descemet’s membrane (DM) in canine eyes. Eighteen canine corneo-scleral discs were included. Intrastromal air injection resulted in the formation of type 1 big bubble (BB) in 73% (n = 11/15) of corneas, with a mean diameter of 11.0 ± 1.3 mm. No type 2 BB was created. Anterior segment optical coherence tomography, histology and transmission electron microscopy confirmed that the wall of BB was composed of DM, in contact with remaining stroma (canine PDL; cPDL). The cPDL was populated with keratocytes, of varying thickness of 16.2 ± 4.2 µm in close apposition to the DM, and composed of collagen bundles arranged in transverse, longitudinal and oblique directions. The interfacial zone, between DM and cPDL, showed fibril extension in all three directions, predominantly longitudinal. Irregular extensions of DM material into cPDL stroma were observed. No long-spaced collagen was detected. In conclusion, there exists a well-defined cleavage plane between the posterior stroma and cPDL, with similar but not identical characteristics as in humans, that is revealed by pneumodissection. This adds to our understanding of the anatomy of the posterior most canine cornea, which will have significant clinical impact on posterior corneal surgery and understanding of corneal pathology in dogs.

Development of a novel rapid repairing agent for concrete based on GFRP waste powder/GGBS geopolymer mortars

The use of waste glass fiber-reinforced polymer (GFRP) powder as a binding agent in the synthesis of geopolymers offers an eco-friendly solution for managing GFRP waste. The aluminosilicate present in GFRP powder can be activated by an alkaline solution to produce a sustainable geopolymer. In this study, a novel rapid repairing material was developed from partially-replaced ground granulated blast furnace slag (GGBS) by GFRP waste powder as precursors in geopolymer mortar (GM). The effect of GFRP powder replacement and mix proportions on the fresh and hardened properties of GMs were evaluated. It was found that an increase in GFRP powder replacement led to an increase in the setting time and a decrease in workability. The highest 28-day compressive strength was obtained at a 20% replacement of GGBS with GFRP powder. At this optimal mixture, the GMs achieved a compressive strength of 15.2 MPa after 6 h and 35.7 MPa after 1 day. Results from the slant shear test revealed that the failure pattern of the GM-repaired concrete samples changed from interface failure to monolithic failure and explosive spalling in the concrete substrate (CS), when the test duration increased from 3-days to 7-days and 28-days, respectively. This was attributed to the formation of a compact interfacial zone with prolonged testing duration, leading to increased bond strength. The developed GMs demonstrate a short setting time, excellent flowability, high early mechanical strength and superior bond properties, and thus can be applied as rapid concrete repair materials or as protective coatings for concrete in corrosive environments.

Shear behavior and damage evolution of the interface between rough rock and cemented tailings backfill

The shear behavior of the interface between rock and cemented tailings backfill (CTB) is extremely critical to the backfill design and stability of the backfilled underground mined-out areas. The corresponding shear behavior and surface damage can be significantly affected by the roughness of the rock surfaces. In our study, sandstone with the same rough surface were prepared using rock engraving technology. The direct shear tests on the rough rock-CTB interfaces were carried out under four different normal stresses and six different roughness of the rock surfaces. The interfacial shear strength and corresponding surface damage were analyzed. A new shear strength criterion of the rough rock-CTB interface was then proposed and verified. Our study shows that the compressive deformation of the combined specimen is much larger than that of dilatancy under a higher normal stress. The residual shear strength is less affected by the rock surface roughness under lower normal stress. The corresponding shear strength of the rough rock-CTB interface does not necessarily increase with the rock surface roughness due to the large strength difference between the sandstone and CTB. The interfacial damaged zones, which increase with the normal stress, are roughly concentrated in the larger concave section of the corresponding 2D profiles. The established shear strength criterion of the rock-CTB interface consists of basic mechanical and morphology parameters which can be easily estimated by the general laboratory tests. The findings obtained from this study can be used to quantify the effect of the rough rock-CTB interface on the stability of CTB.

Effect of fire exposure on the bonding behavior of hybrid engineered composite systems

When used with self-compacting concrete (SCC) in a fresh state, engineered cementitious composites (ECC) can enhance flexural properties and durability. There is, however, some uncertainty as to whether the composites and their related interfacial bonds will endure high temperatures. This article investigates how fire exposure affects hot-jointed concrete systems (CS) that combine SCC and ECC. Residual flexural and tensile properties and possible degradation/debonding of the interfacial zone after exposure to 800 °C were examined, considering the effect of three different fiber types (i.e. polyvinyl alcohol (PVA), steel (SF), and hybrid PVA/steel fibers) in the tension ECC layer. Visual, microstructural, ultrasonic pulse velocity and mass loss properties were assessed for air- and water-cooled specimens. Also, mathematical models were proposed based on the results of each concrete composite. ECC added to SCC at fresh-to-fresh state significantly increased its flexural and splitting tensile resistance, as well as thermal integrity. All composites were negatively affected by fire, but composite systems maintained their interfacial bond without excessive degradation. It was also determined that fibers at the interface area of composite systems are crucial to preserving their mechanical and physical bonding under fire, thus SF resulted in higher thermal resistance compared to PVA.

High-versus low-viscosity resin cements: Its effect on the load-bearing capacity under fatigue of a translucent zirconia

The purpose of the present study was to characterize the elastic modulus and Poisson’s ratio of a resin cement with distinct viscosities, and to evaluate their impact on the static and fatigue strength of a translucent zirconia (4Y-PSZ) after air-abrasion surface treatment. Bar-shaped specimens of two different viscosities of resin cement (high and low) were obtained (25 × 10 × 3 mm). Sonelastic and Maxwell principles tests were performed to determine the elastic modulus and Poisson’s ratio of each resin cement. Disc-shaped specimens of 4Y-PSZ were made (Ø = 15 mm, 1.2 mm in thickness) for the mechanical tests and allocated into groups according to two factors: surface treatment (presence or absence of air-abrasion with alumina particles; 45 μm grain-size); cement (absence, low or high viscosity). The static (n = 10) and cyclical (n = 15) biaxial flexural strength tests were performed by piston-on-three-balls geometry. A fatigue strength test was executed (20 Hz, initial stress of 60 MPa [12% of the mean static biaxial flexural strength], followed by increments of 25 MPa [5% of the mean static biaxial flexural strength] at each step of 10,000 cycles until the failure). The obtained data were analyzed by Weibull analysis. Survival rates were tabulated by the Kaplan-Meier test. Complementary analyses of surface roughness, topography, cross-sectional interfacial zone, fractography, and zirconia crystalline content (X-ray diffraction) were also performed. The evaluated resin cements with high and low viscosity presented similar elastic modulus (13.63 GPa; 12.74 GPa) and Poisson’s ratio (0.32; 0.30), respectively. The air-abraded groups depicted higher mechanical strength of the zirconia ceramics than non-abraded groups (p˂ 0.05), regardless of the resin cement. 4Y-PSZ adhesively bonded to a high or low viscosity resin cement have statistically similar behavior (p˃ 0.05). The mechanical structural reliability of the 4Y-PSZ was not affected by the factors. Therefore, resin cement with high and low viscosity presented similar properties and potential to fill the zirconia surface, and did not affect the mechanical behavior of 4Y-PSZ. However, the air-abrasion surface treatment increased the static and fatigue flexural strength of the translucent zirconia.

Detection of fault zone head waves and the fault interface imaging in the Xianshuihe–Anninghe Fault zone (Eastern Tibetan Plateau)

SUMMARY Fault zone head waves (FZHWs) are an essential diagnostic signal that provides high-resolution imaging of fault interface properties at seismogenic depth. In this study, we validate the existence of a bi-material interface in the Xianshuihe–Anninghe Fault (XAF) zone around their intersection and determine the cross-fault velocity contrast. We employ a semi-automatic workflow to detect and pick FZHWs and direct P waves. In addition, to improve the identification ability of potential FZHWs in the automatic picking process, we adopt a ‘forward-detecting and backward-picking’ strategy combining the short-term average/long-term average (STA/LTA) algorithm with a kurtosis detector. The polarization and characteristic periods of the waveforms are then used to manually refine the picks and evaluate the quality. The results indicate that the average velocity contrast along the southern Xianshuihe Fault is 3–5 per cent, with the northeast side characterizing a faster P-wave velocity, in agreement with tomographic results. A systematic moveout between FZHWs and the direct P waves over a 100 km long fault segment reveals a single continuous interface in the seismogenic zone. The single bi-material fault structure might be conducive to the preparation of large earthquakes and further influences the corresponding dynamic rupture processes.