Reduction In Fracture Strength Research Articles

Mechanical Behaviors of the Single Crystal Two-Dimensional Silicon Carbide (SiC): A Molecular Dynamics Insight

This paper focuses on the two-dimensional silicon carbide (2D-SiC), which has an excellent opportunity to be used as an alternative to graphene in nanotechnologies such as in nanoelectronics, nanoelectromechanical systems (NEMS), nano-sensors, nano-energy harvesting devices, and nano-composites due to its unique structural, mechanical, electronic, and thermal properties. Their mechanical properties characterize the stability of the nanodevices. This study performs molecular dynamics (MD) simulation to examine the mechanical properties based on optimized Tersoff potential of the single crystal 2D-SiC at different temperatures, strain rates, point vacancies, and edge cracks. At room temperature (300 K), the obtained elastic modulus and fracture strength are 423 GPa and 68.89 GPa, respectively, along the armchair direction. As the temperature rises from 100 K to 800 K, the fracture stress falls by 21.96% and the fracture strain by 36.90%. An approximate linear reduction in fracture strength is noticed as the temperature rises from 100 K to 800 K. The elastic modulus also falls as the temperature rises but is not significant. Although the elastic modulus is unchanged, the fracture stress increases by 1.84% while the fracture strain increases by 5.84% for a change in strain rate from 0.0001 ps-1 to 0.005 ps-1. The fracture stress and strain are significantly reduced, primarily due to the edge crack, as the concentration of point vacancy grows from 0.1% to 0.6% and the edge crack size increases from 0.5 nm to 1.5 nm. Moreover, anisotropic behavior is also evaluated at 300 K temperature and 0.001 ps-1 strain rate. These findings would offer a deep understanding of the fracture mechanics of 2D-SiC and also help to address the mechanical instability issue with SiC-based nanodevices.

Fracture strength and bonding interface morphology of CAD/CAM-fabricated ceramic laminate veneers on bleached enamel treated with two different antioxidants.

This study aimed to investigate the effects of two antioxidants and their application time on the fracture strength of computer-aided design and computer-aided manufacturing (CAD/CAM)-fabricated ceramic laminate veneers to bleached enamel, as well as their effects on the bonding interface micromorphology. Eight groups were set: Group NC (without bleaching and antioxidant treatment); Group NA (bleaching without antioxidant treatment); Group SA30, SA60, SA120 and Group PAC30, PAC60, PAC120 (bleaching and treating with sodium ascorbate or proanthocyanidins for 30, 60, and 120 min, respectively). After cementation of veneers, fracture strength values and failure modes were analyzed. The bonding interface morphology was observed by confocal laser scanning microscopy. The fracture strength was impaired when cementation procedure was performed immediately after bleaching. This reduction in fracture strength was reestablished with antioxidant treatment, and an extended treatment time contributed to better improvement. The resin tags at the bonding interfaces of the bleached enamel were impaired. Antioxidant treatments were able to reverse this unfavorable trend.

Influence of the biomechanical behavior of TiO2 and ZrO2 implants after implantoplasty.

Peri-implantitis occurs around dental implants, and implantoplasty has been used to address this ongoing disease; however, the changes to the physical properties of an implant after implantoplasty have not been well documented. This in vitro study aimed to investigate the effect of implantoplasty on fracture strength and the load required for plastic deformation after fatigue cyclic. Twenty Yt-tria-stabilized Zirconia implants (ZrO2 group; Ø 4.1 x 10 mm, Straumann) and commercially pure titanium implants (TiO2 group; Ø 4.1 x 10 mm, Straumann, control group) implants were placed in polyurethane blocks with 5mm supracrestal. After that, 10 Zirconia and 10 Titanium implants were submitted to implantoplasty in the supracrestal portion using a high-speed handpiece with dia-mond burs. Then 4 groups (n=10) based on material and implantoplasty treatment were: Ti-Before (titanium implant control group), Zr-Before (zirconia implant control group), Ti-After (titanium implant test group with implantoplasty), and Zr-After (zirconia implant test group with implan-toplasty). Each implant received its respective titanium abutment system (Purebase or Variobase), installed with a torque of 35 N.cm using a digital torque wrench. The specimens of each group were submitted to step stress test (30°; 10 Hz; 2 million cycles) until failure and the fracture strength (FS) values were recorded. Two-way ANOVA and parametric comparisons with control were adopted. The FS values for Ti-Bef, Zr-Bef, Ti-Aft, and Zr-Aft were 703.6 ± 68.1 N, 1225 ± 123.8 N, 956.6 ± 86.4 N, and 1035.1 ± 85.7 N, respectively. The number of cycles for Ti-Bef, Zr-Bef, Ti-Aft, and Zr-Aft was 379,323 ± 9,354; 564,779 ± 29,903; 351,451 ± 9,904; 467,009 ± 17,641, respectively. The Ti-Bef and Zr-Bef groups showed a significant FS and a number of cycles than the test groups (P<0.05). Both implants investigated (TiO2 and ZrO2) showed reduced fracture strength after implantoplasty and cyclic loading.

Evaluation of Er,Cr:YSGG laser irradiation for debonding of zirconia hybrid abutment crowns from titanium bases.

To evaluate the efficacy of Er,Cr:YSGG laser irradiation on the removal of zirconia hybrid abutment crowns (HAC) from ti-bases and investigate the effects of laser output power and zirconia generation on debonding time and fracture resistance of crowns. A hundred monolithic zirconia HACs were fabricated by using 4Y-TZP and 5Y-TZP materials and subsequently cemented onto the ti-bases with a resin luting agent. Each zirconia group was further divided into 5 subgroups according to the debonding procedure as control (no debonding), 4.5W-, 5W-, and 6W-laser irradiation, heat processed (n = 10). Er,Cr:YSGG laser (Waterlase MD; Biolase Technology Inc., Irvine, CA) was used on a noncontact hard tissue mode at a 20-Hz repetition rate and 140-μs pulse duration with 50% water and 50% air. Debonding durations were recorded for each specimen, and modes of failure were investigated. Crowns were re-cemented on their corresponding ti-bases, and HACs were subjected to fracture strength test. Debonding duration and fracture strength data were statistically analyzed. Fractured zirconia crown surfaces of ti-bases were examined under the scanning electron microscope. 5Y-TZP crowns were debonded from ti-bases in significantly lower durations in comparison with 4Y-TZP crowns for all output powers [4.5W (P = 0.001), 5W (P = 0.002), and 6W (P = 0.0014)]. For both 4Y-TZP and 5Y-TZP materials, debonding duration was significantly decreased with the increase in laser output power (P ≤ 0.001 for 4Y- and 5Y-TZP). In comparison with 4Y-TZP heat-processed group to the 4Y-TZP laser-irradiated groups, no significant differences were detected in terms of fracture strength (P > 0.05), while heat-processed crowns exhibited significantly lower fracture strength values than those of control group (P = 0.006). All debonding procedures significantly reduced fracture strength values of 5Y-TZP crowns in comparison with the control group (P ≤ 0.001). The common failure type was the adhesive failure between the zirconia crown and resin cement for all groups. SEM evaluation showed no visible damage caused by laser irradiation or heat application. The use of Er,Cr:YSGG laser irradiation is an efficient way to retrieve zirconia crowns from ti-bases. The higher the output power of the laser, the shorter the bonding procedure. The debonding duration and fracture strength of the crown were affected by the zirconia generation. Debonded 5Y-TZP zirconia crowns should not be reused due to the decrease in mechanical strength values.

Layer-dependent fracture strength of few-layer WS2 induced by interlayer sliding: a molecular dynamics study

Understanding the relationship between interlayer interactions and the mechanical properties and behaviors of two-dimensional layered materials is critical in the development of related nanodevices. Nevertheless, it is still challenging due to difficulties in experiments. In this work, nanoindentation simulations on few-layer WS2 were conducted by varying the tip radius, suspended membrane radius, and membrane size using a molecular dynamics simulation. Consistent with our previous experimental results, few-layer WS2 exhibited a layer-dependent reduction in fracture strength owing to the uneven stress distribution among individual layers induced by interlayer sliding under out-of-plane deformation. Furthermore, apparent curve hysteresis was observed due to interlayer sliding in the supported region when a large tip radius and membrane radius were employed. However, instead of the supported part, the interlayer sliding within the suspended part resulted in reduced fracture strength with the increase of layer number. These findings not only provide an in-depth comprehension of the influence of interlayer sliding on fracture strength of few-layer WS2, but also suggest that the role of interlayer interactions should be seriously considered during nanodevice design.

Reduced Fracture Strength of 2D Materials Induced by Interlayer Friction.

The potential applications of 2D layered materials (2DLMs) as the functional membranes in flexible electronics and nano-electromechanical systems emphasize the role of the mechanical properties of these materials. Interlayer interactions play critical roles in affecting the mechanical properties of 2DLMs, and nevertheless the understanding of their relationship remains incomplete. In the present work, it is reported that the fracture strength of few-layer (FL) WS2 can be weakened by the interlayer friction among individual layers with the assistance of finite element simulations and density functional theory (DFT) calculations. The reduced fracture strength can be also observed in FL WSe2 but with a lesser extent, which is attributed to the difference in the interlayer sliding energies of WS2 and WSe2 as confirmed by DFT calculations. Moreover, the tip-membrane friction can give rise to the underestimation of the Young's modulus except for the membrane nonlinearity. These results give deep insights into the influence of interfacial interactions on the mechanical properties of 2DLMs, and suggest that importance should be also attached to the interlayer interactions during the design of nanodevices with 2DLMs as the functional materials.

Fracture resistance of cement-retained and screw-cement–retained milled posterior crowns with screw-access hole preparations before and after firing: An in vitro study

Statement of problemWhen a cement-retained lithium disilicate crown needs to be removed, perforation is needed to reach the abutment screw. How this process affects its strength is unclear. PurposeThe purpose of this in vitro study was to evaluate the fracture strength of milled lithium disilicate implant crowns with screw-access holes created before and after the firing stages. Material and methodsNine implant replicas with stock abutments were embedded in acrylic resin. Forty-five lithium disilicate (IPS e.max CAD) crowns were designed, milled, and divided into groups. The control group had no screw access, the blue state group had the screw access created in the intermediate phase of the ceramic, and the postfiring group had the screw access created after firing. The crowns were cemented with a self-adhesive resin cement, placed in an incubator for 24 hours and then thermocycled. The screw-access holes were sealed with composite resin. The crowns were loaded to failure with a universal testing machine using a 1- mm-diameter ball at a crosshead speed of 0.5 mm/min and a 5-kN cell load. Data were analyzed by ANOVA and the Tukey post hoc test (α=.05). ResultsScrew-access holes created before and after firing stages had a significant effect on the fracture resistance of lithium disilicate crowns (P=.002). No difference in fracture resistance was observed between the control group and the blue state group (P>.05), while the fracture resistance of the postfiring group was significantly lower than that of the control group and the blue state group (P<.05). ConclusionsThe fracture strength of lithium disilicate crowns was not affected by a screw-access hole created during the blue state of the ceramic followed by repair with composite resin. Creating a screw-access hole after firing the ceramic reduced fracture strength.

Metal pollution as a potential threat to shell strength and survival in marine bivalves

Marine bivalve molluscs, such as scallops, mussels and oysters, are crucial components of coastal ecosystems, providing a range of ecosystem services, including a quarter of the world's seafood. Unfortunately, coastal marine areas often suffer from high levels of metals due to dumping and disturbance of contaminated material. We established that increased levels of metal pollution (zinc, copper and lead) in sediments near the Isle of Man, resulting from historical mining, strongly correlated with significant weakening of shell strength in king scallops, Pecten maximus. This weakness increased mortality during fishing and left individuals more exposed to predation. Comparative structural analysis revealed that shells from the contaminated area were thinner and exhibited a pronounced mineralisation disruption parallel to the shell surface within the foliated region of both the top and bottom valves. Our data suggest that these disruptions caused reduced fracture strength and hence increased mortality, even at subcritical contamination levels with respect to current international standards. This hitherto unreported effect is important since such non-apical responses rarely feed into environmental quality assessments, despite potentially significant implications for the survival of organisms exposed to contaminants. Hence our findings highlight the impact of metal pollution on shell mineralisation in bivalves and urge a reappraisal of currently accepted critical contamination levels.

High‐temperature performance of two‐layered ceramics and the implications for Roman crucibles

Roman metalworking crucibles are frequently characterized by an extra outer layer of clay, applied to a pre‐formed vessel. Three‐point bending and standardized dead‐weight loading tests were conducted to determine the advantages offered by the extra outer layer. Deformation and fracture behaviour, at temperatures up to 1100°C, of two‐layer, monolithic and tempered‐monolithic briquettes were compared. Measurements indicated that the two‐layer briquettes were more resistant to fracture at high temperatures: &gt; 850°C they showed more extensive plastically deformed regions than monolithic briquettes. The influence of temper was consistent with previous results: tempering caused quasi‐stable fracture and reduced fracture strength. The results suggest extra outer layers assisted in preventing catastrophic failure.

Fire and mechanical properties of DGEBA-based epoxy resin cured with a cycloaliphatic hardener: Combined action of silica, melamine and DOPO-derivative

The effect of the addition of additives such as melamine (Mel), silica nanoparticles and a phosphorus-based compound, i.e. 3-(6-oxidodibenzo[c,e][1,2]oxaphosphinin-6-yl)propenamide (DA), on the fire and mechanical performance of a bisphenol A diglycidyl ether (DGEBA)-based epoxy resin cured with isophoronediamine has been investigated. A UL 94-V0 classification was achieved for epoxy resin containing DA at 2 wt% of phosphorus loading. However, addition of silica nano particles was necessary to avoid melt dripping. The incorporation of DA and Mel to the epoxy resin promoted a remarkable reduction (48% to 70%) in the heat release rate (HRR) values, a significant delay (up to 47%) in the ignition time in cone calorimetry experiments, and thus an increase (~75%) in the time to flashover. Evolved gas, thermal and fire analysis was used to propose the combined mode of action of DA, Mel and silica in the fire performance improvement of the epoxy system. Tensile and three-point bending flexural tests showed that the addition of DA increases the rigidity of the resin, resulting in a strong increase in the Young's modulus (up to 34%) and in a slight reduction in fracture strength, elongation break and toughness which is typical for non-reactive additives.

Analysis of quenching heat treatment, martemper on structure micro and hardness in SCMn3 steel.

Microstructure analysis and hardness analysis has been carried out on cast steel for components of soil digging machines due to heat treatment of quench, and martemper. The presence of residual austenite causes wear resistance and reduced fracture strength in the earth quarry component to function as a support for the designed arm. In its manufacture, it uses metal casting technology and heat quenching treatments and templates in suitable cooling media, to meet standard requirements. The temperature treatment of austenite 875 °C temperature was held for 90 minutes, and then quenched with variations in the cooling media of water, oil, and salt bath. Furthermore, the martemper process at 425 °C for 90 minutes is cooled to air to room temperature. Microstructure testing and weight percent composition using SEM-EDX and Brihnell scale hardness test. The analysis shows that the hardness value (388 HB) of cast steel quenched in salt bath media is greater than ordinary water (299 HB) and oil (260 HB). However, after the martemper process the value of hardness drops to (342 HB) in the salt water medium, which remains larger than ordinary water (264 HB) and oil (233 HB). This is due to the faster cooling speed in brine and produces martensitic microstructure and residual austenite after being observed with SEM-EDX. The results of this study meet the quality requirements according to the JIS G5111 standard where the minimum hardness value is 222 HB, to be used as a component in excavator.

Mixed Mode I/II Fracture Strength of Modified HMA Concretes Subjected to Different Temperature Conditions

Abstract In this article, the effects of fixed and variable temperature conditions on the fracture toughness of three different hot mix asphalt (HMA) concretes were investigated. The first HMA concrete contained a normal binder, the second one was modified with crumb rubber (CR), and the third mixture was modified with styrene-butadiene-styrene (SBS). The pure mode I, pure mode II, and three different mixed mode I/II fracture toughness values were calculated by performing fracture experiments on the semicircular bend specimens made of the aforementioned HMA concretes. The results displayed that the variable temperature condition reduced fracture strength of the HMA concretes. Moreover, the addition of SBS and CR improved the fracture strength of HMA concretes significantly, such that the CR enhanced the fracture strength between 2 and 22 % depending on the loading mode and environmental conditions. These values were between 6 and 34 % for the HMAs modified by SBS. Therefore, the fracture strength of HMA was more improved by the SBS than the CR. Furthermore, the HMA concretes were subjected to a critical condition under mixed mode I/II loading rather than pure mode I.

A molecular dynamics study of the mechanical properties of h-BCN monolayer using a modified Tersoff interatomic potential

Using molecular dynamics (MD) simulations, we investigate the mechanical properties of hexagonal BCN monolayer, a newly synthesized two-dimensional material with an atom ratio of B/C/N = 1:1:1. The Tersoff potential is modified to get good agreement between predicted and measured fracture strengths of graphene. With this modified Tersoff potential, we perform extensive MD simulations to study the effect of temperature, strain rate and vacancy defect on the mechanical properties of h-BCN. It is found that h-BCN is a strong material with fracture strength of 81.4–93.5 GPa, albeit ∼35% lower than that of graphene. Similar to graphene, temperature has strong effect on the mechanical properties of h-BCN. As the temperature increases from 10 K to 1300 K, the fracture strength and strain of h-BCN drops by 55% and 62%, respectively. The strain rate is found to have a moderate effect. When the strain rate increases from 0.00002 to 0.0125 ps−1, the fracture strength and strain of h-BCN increases 6.1% and 12%, respectively. As for the atomic defect, a very small concentration (0.028%) of vacancy in h-BCN is able to cause a 28% reduction in fracture strength and a 35.5% reduction in fracture strain. These findings have significance for its future applications in nanodevices.

Tuning correlative atomic scale fluctuation and related properties in Ni–Nb–Zr metallic glasses

Herein, we systematically investigated how to tailor correlative fluctuation and related properties in Ni–Nb–Zr metallic glasses (MGs). The Ni60Nb40-xZrx MGs (x = 0–20 at.%) with Nb–Zr atomic pair (ΔHmix=+4 kJ/mol) exhibited correlative atomic scale fluctuations in composition and topological orders upon Zr addition up to 20 at.% in XAFS analysis, which would, in turn, lead to fluctuations in local elastic properties. Interestingly, a statistical analysis of strain burst sizes along with in situ bending test showed that more effective elastic interaction between weak spots upon loading is promoted in Ni60Nb20Zr20, due to correlative atomic scale fluctuations, thereby resulting in multiple shear bands. The bulk specimens (d = 1 mm) for 8 and 10 at.% of Zr with increased glass-forming ability (GFA) exhibited enhanced plasticity without the reduction of fracture strength, implying cooling rate effect on fluctuation-induced plasticity. We believe that the results of this study would provide an effective guideline for tuning correlative fluctuation and related properties in MGs via manipulation of enthalpy relationship and cooling rate.

Impact of stem taper damage on the fracture strength of ceramic heads with adapter sleeves

BackgroundUsing a new ceramic head with a titanium adapter sleeve offers the possibility of maintaining a well fixed stem when conducting cup revision of a total hip arthroplasty. The aim of this study is to test the impact of stem taper damage on the fracture strength of sleeved ceramic heads. MethodsPristine zirconia-toughened alumina heads with titanium adapter sleeves (BIOLOX®OPTION System) were tested on damaged Ti-4Al-6V stem tapers in accordance with ISO7206-10. Four distinctive damage types classified as intolerable by the manufacture were investigated, representing various reductions in contact area between the stem taper and sleeve taper as well as damage incurred from previous ceramic head fracture. FindingsThe largest reduction in fracture strength occurred for a loss of contact for the entire length of the stem taper. Nonetheless, the fracture strength in all investigated cases was several times higher than that defined by the FDA standards. InterpretationThe use of a titanium sleeve recreates a uniform contact situation between the ceramic head and the outer sleeve taper in situations of damaged stem tapers. For the investigated damage types a high fracture strength of the ceramic head was maintained. This study supports the clinical use for sleeved ceramic heads in instances of greater damages of stem tapers than previously defined in order to spare patients from stem removal.

Tuning Correlative Heterogeneity and Related Properties in Ni-Nb-Tm (Tm=Zr, Y, Gd) Metallic Glasses

Herein, we systematically investigated how to tailor correlative heterogeneity and related properties in Ni-Nb-(Zr, Y, Gd) metallic glasses (MGs). The Ni60Nb40-xZrx MGs (x=0-20 at.%) with Nb-Zr atomic pair (〖∆H〗mix=+4 kJ/mol) exhibited correlative atomic scale chemical and topological heterogeneities upon Zr addition, which can be evaluated by EXAFS analysis. Interestingly, a statistical analysis of strain burst sizes along with in situ bending test showed that the easier nucleation of chaotic shear bands is promoted with the aid of stress localization induced by the heterogeneities. The bulk specimens (d=1 mm) for 8 and 10 at.% of Zr with increased glass-forming ability (GFA) exhibited enhanced plasticity without the reduction of fracture strength, implying cooling rate effect on heterogeneity-induced plasticity. Contrastively, the Ni60Nb40-y(Y, Gd)y MGs with Nb-Y or Nb-Gd atomic pair (〖∆H〗mix=+30 kJ/mol) showed hierarchically correlative nanoscale phase separated microstructures, which can be carefully interpreted by construction of metastable miscibility gap. The microstructures rely on four different variables (the composition, the symmetry of a miscibility gap, the critical temperature and the GFA of each phase) and provide a weak interface resulting in extreme brittleness as well as drastically decreased GFA. We believe that the results of this study would provide an effective guideline for tuning correlative heterogeneity and related properties in MGs via manipulation of enthalpy relationship and cooling rate.

Fracture behavior of metal oxide/silver nanowire composite electrodes under cyclic bending

The mechanical responses under cyclic bending of Ag nanowire composite electrodes coated with various metal oxide films of different thicknesses were explored, in an attempt to evaluate their applicability to flexible transparent electrodes. Al2O3, HfO2, and TiO2 films were deposited onto Ag nanowire electrodes by atomic layer deposition at a low temperature of 100 °C, and cyclic bending tests with in situ resistance measurements were conducted for up to 300,000 cycles. Thicker metal oxide films resulted in greater increases in the resistances of the composite electrodes under cyclic bending due to the reduced fracture strength of the films. Regardless of the type of metal oxide, however, similar tendencies were observed in the resistance changes in response to cyclic bending. It was found that the critical thickness calculation based on the Griffith theory for the evaluation of the brittle-to-ductile transition was not applicable to the metal oxide/Ag nanowire composite electrodes. By correlating the mechanical, ambient, and thermal reliability test results with those of optoelectrical property evaluations, the optimal thickness of Al2O3 film, as a representative metal oxide film, was determined to be 3–5 nm for Ag nanowire composite flexible transparent electrodes.

Fracture strength of veneered translucent zirconium dioxide crowns with different porcelain thicknesses

Objective: To evaluate fracture strength of veneered translucent zirconium dioxide crowns designed with different porcelain layer thicknesses.Materials and Methods: Sixty crowns, divided into six groups of 10, were used in this study. Groups were divided according to different thicknesses of porcelain veneer on translucent zirconium dioxide cores of equal thickness (0.5 mm). Porcelain thicknesses were 2.5, 2.0, 1.0, 0.8, 0.5 and 0.3 mm. Crowns were artificially aged before loaded to fracture. Determination of fracture mode was performed using light microscope.Results: Group 1.0 mm showed significantly (p ≤ .05) highest fracture loads (mean 1540 N) in comparison with groups 2.5, 2.0 and 0.3 mm (mean 851, 910 and 1202 N). There was no significant difference (p>.05) in fracture loads among groups 1.0, 0.8 and 0.5 mm (mean 1540, 1313 and 1286 N). There were significantly (p ≤ .05) more complete fractures in group 0.3 mm compared to all other groups which presented mainly cohesive fractures.Conclusions: Translucent zirconium dioxide crowns can be veneered with minimal thickness layer of 0.5 mm porcelain without showing significantly reduced fracture strength compared to traditionally veneered (1.0–2.0 mm) crowns. Fracture strength of micro-veneered crowns with a layer of porcelain (0.3 mm) is lower than that of traditionally veneered crowns but still within range of what may be considered clinically sufficient. Porcelain layers of 2.0 mm or thicker should be used where expected loads are low only.

Graphene Coatings as Barrier Layers to Prevent the Water-Induced Corrosion of Silicate Glass.

Corrosion-protective coatings for silicate glass based on the transfer of one or two layers of graphene grown on copper by chemical vapor deposition have been demonstrated. The effectiveness of graphene to act as a glass corrosion inhibitor was evaluated by water immersion testing. After 120 days of immersion in water, bare glass samples had a significant increase in surface roughness and defects, which resulted in a marked reduction in fracture strength. In contrast, the single- and double-layer graphene-coated glasses experienced negligible changes in both fracture strength and surface roughness. The anticorrosion mechanism was also studied.

Atomic vacancies significantly degrade the mechanical properties of phosphorene

Due to low formation energies, it is very easy to create atomic defects in phosphorene during its fabrication process. How these atomic defects affect its mechanical behavior, however, remain unknown. Here, we report on a systematic study of the effect of atomic vacancies on the mechanical properties and failure behavior of phosphorene using molecular dynamics simulations. It is found that atomic vacancies induce local stress concentration and cause early bond-breaking, leading to a significant degradation of the mechanical properties of the material. More specifically, a 2% concentration of randomly distributed mono-vacancies is able to reduce the fracture strength by ∼40%. An increase in temperature from 10 to 400 K can further deteriorate the fracture strength by ∼60%. The fracture strength of defective phosphorene is also found to be affected by defect distribution. When the defects are patterned in a line, the reduction in fracture strength greatly depends on the tilt angle and the loading direction. Furthermore, we find that di-vacancies cause an even larger reduction in fracture strength than mono-vacancies when the loading is in an armchair direction. These findings provide important guidelines for the structural design of phosphorene in future applications.