This study develops an anisotropic generalization of the volumetric hardening model (VHM) to investigate the governing deformation mechanisms at the onset of yielding of additively manufactured ...lattice structure (AMLS) made of a nickel-based superalloy, Inconel 718 (IN718), under quasi-static loading. The discussion of deformation mechanisms relies on defining a new yield surface using a combination of experimental measurements and finite element simulations that enable the representation of three distinct behavioral features of IN718 lattice structures under mechanical loading including (1) tension-compression asymmetry of strut-level response; (2) tension-compression asymmetry of the aggregate response; and (3) hydrostatic pressure sensitivity of the strut-level response. Typically, the VHM is used to describe the aggregate response of lattice or foam materials to global loading. The VHM model could be directly applied at the strut-level; however, this would assume a one-to-one correspondence between the local and global response. Such an assumption is not justified a priori and could alter the evolution of the local deformation mechanisms and the resulting analysis of failure modes and structural degradation. Therefore, we introduce a modified VHM (or MVHM), which represents a more appropriate yield criterion. The Johnson-Cook damage criterion and damage evolution law, which is based on Hillerborg's fracture energy method, are coupled with the MVHM to investigate the damage initiation and evolution, and their influence on the global stress-strain response using finite element simulations.
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Lithium metal anodes have attracted extensive attention owing to their high theoretical specific capacity. However, the notorious reactivity of lithium prevents their practical applications, as ...evidenced by the undesired lithium dendrite growth and unstable solid electrolyte interphase formation. Here, we develop a facile, cost-effective and one-step approach to create an artificial lithium metal/electrolyte interphase by treating the lithium anode with a tin-containing electrolyte. As a result, an artificial solid electrolyte interphase composed of lithium fluoride, tin, and the tin-lithium alloy is formed, which not only ensures fast lithium-ion diffusion and suppresses lithium dendrite growth but also brings a synergistic effect of storing lithium via a reversible tin-lithium alloy formation and enabling lithium plating underneath it. With such an artificial solid electrolyte interphase, lithium symmetrical cells show outstanding plating/stripping cycles, and the full cell exhibits remarkably better cycling stability and capacity retention as well as capacity utilization at high rates compared to bare lithium.
This study demonstrates a relationship between manufacturing variables including design topology and post-processing heat treatment on the porosity distribution, quasi-static, and dynamic behavior of ...additively manufactured lattice structures (AMLS). Lattice structures were manufactured out of Inconel 718 using selective laser melting technique with four different topologies. The effect of heat treatment on the porosity size and distribution was examined using X-ray computed tomography for as-built (AB), stress relieved (SR), and hot isostatic pressed (HIP) plus solution aged (SA) heat-treatment conditions. It was noticed that reduction of porosity in the as-built samples, as a result of SR, was greater compared the porosity reduction due to the subsequent HIP plus SA. Quasi-static and dynamic loading was conducted and it was found that the deformation trends of each topology were independent of the strain rate. It was also found that the stress relieving heat treatment process enhances the quasi-static and dynamic flow stress after yielding. However, further heat-treating, including HIP and SA, for the same topology were not as effective as the initial SR process. Furthermore, the validity of digital image correlation in measuring average global strain and the validity of using a Kolsky bar for measuring dynamic mechanical behavior of AMLS are discussed.
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In recent years, hybrid perovskite solar cells (HPSCs) have received considerable research attention due to their impressive photovoltaic performance and low‐temperature solution processing ...capability. However, there remain challenges related to defect passivation and enhancing the charge carrier dynamics of the perovskites, to further increase the power conversion efficiency of HPSCs. In this work, the use of a novel material, phenylhydrazinium iodide (PHAI), as an additive in MAPbI3 perovskite for defect minimization and enhancement of the charge carrier dynamics of inverted HPSCs is reported. Incorporation of the PHAI in perovskite precursor solution facilitates controlled crystallization, higher carrier lifetime, as well as less recombination. In addition, PHAI additive treated HPSCs exhibit lower density of filled trap states (1010 cm−2) in perovskite grain boundaries, higher charge carrier mobility (≈11 × 10−4 cm2 V−1 s), and enhanced power conversion efficiency (≈18%) that corresponds to a ≈20% improvement in comparison to the pristine devices.
A novel material called phenylhydrazinium iodide (PHAI) is effective for defects minimization, surface passivation, and efficient charge transportation in hybrid perovskite solar cells. It plays multiple roles in controlled crystallization, stabilizing under‐coordinated ions, and as a self‐supported moisture barrier in perovskite films.
•Investigated origin of high carrier mobility and low residual stress in AZO thin films for next generation flexible devices.•Superimposing RF power onto DC Power controlled energy and flux of ...incident ions during sputtering process.•Mixed RF/(RF+DC) sputtering process results in better crystallinity and low residual stress.•XPS study shows a variation in defect density in AZO thin film with different RF/(RF+DC) ratios.•The defects finally migrate to grain boundaries and controls the carrier mobility.
In this work, the energy and flux of high energetic ions were controlled by RF superimposed DC sputtering process to increase the grain size and suppress grain boundary potential with minimum residual stress in Al doped ZnO (AZO) thin film. AZO thin films were deposited at different RF/(RF + DC) ratios by keeping total power same and were investigated for their electrical, optical, structural and nanoscale grain boundaries potential. All AZO thin film showed high crystallinity and orientation along (002) with peak shift as RF/(RF + DC) ratio increased from 0.0, pure DC, to 1.0, pure RF. This peak shift was correlated with high residual stress in as-grown thin film. AZO thin film grown at mixed RF/(RF + DC) of 0.75 showed high electron mobility, low residual stress and large crystallite size in comparison to other AZO thin films. The nanoscale grain boundary potential was mapped using Kelvin Probe Force Microscopy in all AZO thin film and it was observed that carrier mobility is controlled not only by grains size but also by grain boundary potential. The XPS analysis confirms the variation in oxygen vacancies and zinc interstitials which explain the origin of low grain boundaries potential and high carrier mobility in AZO thin film deposited at 0.75 RF/(RF + DC) ratio. This study proposes a new way to control the grain size and grain boundary potential to further tune the optoelectronic-mechanical properties of AZO thin films for next generation flexible and optoelectronic devices.
This focused review attempts to capture and collate some of the key advancements achieved on two vital components: charge transport (hole/electron) layers and contact electrodes in flexible ...perovskite photovoltaics.
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Perovskite-based photovoltaic materials have been attracting attention for their strikingly improved performance at converting sunlight into electricity. The beneficial and unique optoelectronic characteristics of perovskite structures enable researchers to achieve an incredibly remarkable power conversion efficiency. Flexible hybrid perovskite photovoltaics promise emerging applications in a myriad of optoelectronic and wearable/portable device applications owing to their inherent intriguing physicochemical and photophysical properties which enabled researchers to take forward advanced research in this growing field. Flexible perovskite photovoltaics have attracted significant attention owing to their fascinating material properties with combined merits of high efficiency, light-weight, flexibility, semi-transparency, compatibility towards roll-to-roll printing, and large-area mass-scale production. Flexible perovskite-based solar cells comprise of 4 key components that include a flexible substrate, semi-transparent bottom contact electrode, perovskite (light absorber layer) and charge transport (electron/hole) layers and top (usually metal) electrode. Among these components, interfacial layers and contact electrodes play a pivotal role in influencing the overall photovoltaic performance. In this comprehensive review article, we focus on the current developments and latest progress achieved in perovskite photovoltaics concerning the charge selective transport layers/electrodes toward the fabrication of highly stable, efficient flexible devices. As a concluding remark, we briefly summarize the highlights of the review article and make recommendations for future outlook and investigation with perspectives on the perovskite-based optoelectronic functional devices that can be potentially utilized in smart wearable and portable devices.
Objectives
The aim was to analyze clinical parameters of peri‐implantitis in human subjects exposed and non‐exposed to use of systemic statins.
Material and methods
This retrospective cohort pilot ...study compared patient records of 60 exposed individuals to 196 non‐exposed individuals as of 2011 throughout 2017. Source of records were specialist and general dentistry clinics in Public Dental Service, Stockholm County, Sweden. Extent/severity of peri‐implantitis and peri‐implant bone loss were registered as well as intake of systemic statins. Background variables considered were bleeding on probing, bone‐loss, age, gender, earlier periodontitis, prosthetic quality, and smoking. Stepwise linear and logistic regression analysis at the individual level was adopted in order to study the influence of statin use on the severity of peri‐implantitis and the incidence of peri‐implant bone loss. Results were considered statistically significant at p < 0.05.
Results
Peri‐implant bone loss was significantly correlated to use of statin after compensation for age and sex.
Conclusions
The results render an actual effect of statins on peri‐implant bone loss plausible. Further research is warranted.
Organic-inorganic perovskite cell has shown a great deal of interest in past few years due to its ability to achieve high power conversion efficiency (PCE). Use of charge transport layers such as ...n-type TiO2 and p-type doped spiroOMeTAD in a n-i-p device architecture has shown enhanced perovskite solar cell device performance. Use of doped spiroOMeTAD as hole transport layer in the n-i-p device structure has been effective but possess disadvantages such as complex processing, use of corrosive additives, processing in ambient air for efficient hole doping. Here we report the study of solution processed benzodithiophene based polymer PBDTT-FTTE as an alternative hole transport layer to doped small molecule spiroOMeTAD. PBDT-FTTE doped with 3% DIO (diiodooctane) achieved PCE of 11.6% which was comparable to matching PCE of 11.6% obtained from using spiroOMeTAD as hole transport layer. We showed that unlike spiroOMeTAD, polymer PBDTT-FTTE is processed inside N2 filled glove box and is easier to process as compared to spiroOMeTAD which requires processing in ambient humid air and is doped with additives mixed in corrosive solvent, causing degradation to perovskite layer underneath.
PBDT-FTTE doped with 3% DIO (diiodooctane) achieved PCE of 11.6% which was comparable to matching PCE of 11.6% obtained from using spiroOMeTAD as hole transport layer. Display omitted
•Polymer PBDTT-FTTE was used as hole transport layer (HTL) to replace spiro-OMeTAD for perovskite solar cells.•Polymer PBDTT-FTTE based solar cells achieved comparable performance (11.6%) as that (11.6%) of spiro-OMeTAD based cells.•Use of benzodithiophene based polymer PBDTT-FTTE does not require processing HTL in air.•Processing polymer PBDTT-FTTE as HTL involves single dopant as compare to multiple dopants in spiro-OMeTAD as HTL.
Organic solar cells have received a lot of attention in the last few decades. Extensive experimental work has been conducted to improve organic solar cell performance. However, a much more realistic ...and accurate model needs to be developed that can simulate and predict photovoltaic performance for organic solar cells. In this work, a Kinetic Monte Carlo (KMC) model was developed to simulate the morphological variation of organic solar cells and its effects on photovoltaic parameters. This model is currently based on P3HT: PCBM system and can be easily extended to any low bandgap polymer solar cells. The novelty and advancement of this work is that this new KMC simulation model can simulate three different parameters including domain size, donor-acceptor ratio and active layer thickness in the same model and predict the efficiency of organic solar cells on the variation of these parameters. This simulation model has been validated by photovoltaic performance from fabricated devices. The optimized parameters of simulation and fabrication are correlated and the simulation results are in agreement with the experimental results. With the assistance from this model, researchers may be able to simplify the complex fabrication processing by identifying optimal conditions such as domain size, donor-acceptor ratio and active layer thickness via this new simulation model.
The novelty and advancement of this work is that this new KMC simulation model can simulate three different parameters including domain size, donor-acceptor ratio and active layer thickness in the same model and predict the efficiency of organic solar cells on the variation of these parameters. Display omitted
•Kinetic Monte Carlo (KMC) model simulates effects of morphological variation on the performance of organic solar cells.•The KMC model simulates three parameters: domain size, donor-acceptor ratio and active layer thickness.•Identifying the optimal parameters using the reported model would simplify the complex fabrication processing.•Optimized parameters from simulation and fabrication are correlated with good agreement.
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