Diazinon is one of organophosphate pesticides which it is classified as a relatively dangerous substance (Class II by WHO). The PANI/g C3N4/ CeO2 nanocomposite was synthesized by in situ polymerization method to determine the efficiency of photocatalytic degradation of diazinon. The photocatalytic activities efficiencies of the supported and unsupported nanocomposites were evaluated using diazinon as a model pollutant. The superior photocatalytic effect of the PANI/g C3N4/CeO2 nanocomposite is attributed to the synergistic effect of PANI and g C3N4/CeO2 which promotes migration efficiency of the photogenerated carriers on the g C3N4/CeO2 nanocomposite interface. The effects of pH, initial diazinon concentration, catalyst load, hydrogen peroxide as well as effect of other organic compound were investigated using photocatalytic degradation of PANI/g C3N4/CeO2. The results obtained indicate the efficient degradation at pH= 6 which extent to 94.08 %, at 10 ppm extent to 88.9%, at 0.1 g/L extent to 97.48 %; were as increasing the concentration of hydrogen peroxide, the percent of degradation of diazinon increased due to the increased reaction between hydrogen peroxide and electron in the conduction band of PANI/g-C3N4/CeO2. Hydrogen peroxide can effectively inhibited electron hole recombination. Therefore hydrogen peroxide is better electron acceptor than dissolved oxygen; it acts as an alternative electron acceptor to oxygen. The effect of different organic compound on the photocatalytic degradation of diazinon; organic compound such as phenol, citric acid, EDTA and oxalic acid were examined, the result indicated that photocatalytic degradation was negatively affected in the presence of all organic compounds.
{"title":"PANI/g-C3N4/CeO2 Nanocomposite for Photodegradation of Diazinon in Aqueous Solution","authors":"A. Hussen","doi":"10.2139/SSRN.3825594","DOIUrl":"https://doi.org/10.2139/SSRN.3825594","url":null,"abstract":"Diazinon is one of organophosphate pesticides which it is classified as a relatively dangerous substance (Class II by WHO). The PANI/g C3N4/ CeO2 nanocomposite was synthesized by in situ polymerization method to determine the efficiency of photocatalytic degradation of diazinon. The photocatalytic activities efficiencies of the supported and unsupported nanocomposites were evaluated using diazinon as a model pollutant. The superior photocatalytic effect of the PANI/g C3N4/CeO2 nanocomposite is attributed to the synergistic effect of PANI and g C3N4/CeO2 which promotes migration efficiency of the photogenerated carriers on the g C3N4/CeO2 nanocomposite interface. The effects of pH, initial diazinon concentration, catalyst load, hydrogen peroxide as well as effect of other organic compound were investigated using photocatalytic degradation of PANI/g C3N4/CeO2. The results obtained indicate the efficient degradation at pH= 6 which extent to 94.08 %, at 10 ppm extent to 88.9%, at 0.1 g/L extent to 97.48 %; were as increasing the concentration of hydrogen peroxide, the percent of degradation of diazinon increased due to the increased reaction between hydrogen peroxide and electron in the conduction band of PANI/g-C3N4/CeO2. Hydrogen peroxide can effectively inhibited electron hole recombination. Therefore hydrogen peroxide is better electron acceptor than dissolved oxygen; it acts as an alternative electron acceptor to oxygen. The effect of different organic compound on the photocatalytic degradation of diazinon; organic compound such as phenol, citric acid, EDTA and oxalic acid were examined, the result indicated that photocatalytic degradation was negatively affected in the presence of all organic compounds.","PeriodicalId":18341,"journal":{"name":"Materials Science eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91210689","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sheng Fan, D. Prior, A. Cross, D. Goldsby, T. Hager, M. Negrini, Chao Qi
Abstract Dynamic recrystallization is an important mechanical weakening mechanism during the deformation of ice, yet we currently lack robust quantitative tools for identifying recrystallized grains in the “migration” recrystallization regime that dominates ice deformation at temperatures close to the ice melting point. Here, we propose grain boundary irregularity as a quantitative means for discriminating between recrystallized (high sphericity, low irregularity) and remnant (low sphericity, high irregularity) grains. To this end, we analyzed cryogenic electron backscatter diffraction (cryo-EBSD) data of deformed polycrystalline ice, to quantify dynamic recrystallization using grain boundary irregularity statistics. Grain boundary irregularity has an inverse relationship with a sphericity parameter, Ψ , defined as the ratio of grain area and grain perimeter, divided by grain radius in 2-D so that the measurement is grain size independent. Sphericity ( Ψ ) typically decreases with increasing grain size, up to a threshold grain size, above which Ψ either plateaus (at temperature, T -10°C) or increases much more gradually (at T ≥ -10°C). There is no apparent relationship between grain sphericity and grain c-axis orientation even at very high temperatures (-4 and -5°C), where GBM dominants, suggesting little crystallographic control on the activity of grain boundary migration (GBM). Decreasing sphericity up to the threshold grain size can be explained by newly-formed, small, spherical recrystallized grains growing via strain-induced GBM and thereby developing increasingly irregular grain boundaries. We suggest that the plateau (or gradual decrease) in sphericity at larger sizes represents a population of original grains (i.e., remnant grains) that becomes increasingly irregular (at similar rates) due to the balance between GBM and nucleation. In this interpretation, the threshold grain size represents the largest grain size reached by a growing recrystallized grain by the end of an experiment. Thus, grain boundary irregularity provides a means for discriminating between recrystallized and remnant grains—a capability that is potentially useful for evaluating dynamic recrystallization processes in ice deformed at temperatures close to the melting point. The threshold grain size and experiment duration can be used to calculate the rates of recrystallization and grain size evolution associated with GBM. Grain size evolution rates are similar at high and low temperatures, suggesting similar GBM rates. Previous studies show that grain boundary mobility decreases with decreasing temperature. The driving force of GBM, on the other hand, has a positive correlation with stress, which increases with a decreasing temperature if strain rate remains unchanged. The balance between boundary mobility and driving force is likely the cause of similar GBM rates between high and low temperatures.
{"title":"Using Grain Boundary Irregularity to Quantify Dynamic Recrystallization in Ice","authors":"Sheng Fan, D. Prior, A. Cross, D. Goldsby, T. Hager, M. Negrini, Chao Qi","doi":"10.2139/ssrn.3762203","DOIUrl":"https://doi.org/10.2139/ssrn.3762203","url":null,"abstract":"Abstract Dynamic recrystallization is an important mechanical weakening mechanism during the deformation of ice, yet we currently lack robust quantitative tools for identifying recrystallized grains in the “migration” recrystallization regime that dominates ice deformation at temperatures close to the ice melting point. Here, we propose grain boundary irregularity as a quantitative means for discriminating between recrystallized (high sphericity, low irregularity) and remnant (low sphericity, high irregularity) grains. To this end, we analyzed cryogenic electron backscatter diffraction (cryo-EBSD) data of deformed polycrystalline ice, to quantify dynamic recrystallization using grain boundary irregularity statistics. Grain boundary irregularity has an inverse relationship with a sphericity parameter, Ψ , defined as the ratio of grain area and grain perimeter, divided by grain radius in 2-D so that the measurement is grain size independent. Sphericity ( Ψ ) typically decreases with increasing grain size, up to a threshold grain size, above which Ψ either plateaus (at temperature, T -10°C) or increases much more gradually (at T ≥ -10°C). There is no apparent relationship between grain sphericity and grain c-axis orientation even at very high temperatures (-4 and -5°C), where GBM dominants, suggesting little crystallographic control on the activity of grain boundary migration (GBM). Decreasing sphericity up to the threshold grain size can be explained by newly-formed, small, spherical recrystallized grains growing via strain-induced GBM and thereby developing increasingly irregular grain boundaries. We suggest that the plateau (or gradual decrease) in sphericity at larger sizes represents a population of original grains (i.e., remnant grains) that becomes increasingly irregular (at similar rates) due to the balance between GBM and nucleation. In this interpretation, the threshold grain size represents the largest grain size reached by a growing recrystallized grain by the end of an experiment. Thus, grain boundary irregularity provides a means for discriminating between recrystallized and remnant grains—a capability that is potentially useful for evaluating dynamic recrystallization processes in ice deformed at temperatures close to the melting point. The threshold grain size and experiment duration can be used to calculate the rates of recrystallization and grain size evolution associated with GBM. Grain size evolution rates are similar at high and low temperatures, suggesting similar GBM rates. Previous studies show that grain boundary mobility decreases with decreasing temperature. The driving force of GBM, on the other hand, has a positive correlation with stress, which increases with a decreasing temperature if strain rate remains unchanged. The balance between boundary mobility and driving force is likely the cause of similar GBM rates between high and low temperatures.","PeriodicalId":18341,"journal":{"name":"Materials Science eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81147833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Moreira, M. Fernandes, Estela O. Carvalho, A. Nicolau, V. Lazić, V. Lazić, J. Nedeljković, S. Lanceros‐Méndez
The search for novel antimicrobial strategies capable of avoiding resistance mechanisms in bacteria are highly needed due to the alarming emergence of antimicrobial resistance. The application of physical stimuli as a mean of sensitizing bacteria for the action of antimicrobials on otherwise resistant bacteria or by allowing the action of an extremely low quantity of antimicrobials may be seen as a breakthrough for such purpose. This work proposes the development of antibacterial nanocomposites using the synergy between the electrically active microenvironments, created by a piezoelectric polymer (poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE)), with green-synthesized silver nanoparticles (AgNPs). The electrical microenvironment is generated via mechanical stimulation of piezoelectric PVDF-TrFE/AgNPs films using a lab-made mechanical bioreactor. The generated material’s electrical response further translates to bacterial cells, which in combination with AgNPs and the specific morphological features of the material induce important antibacterial and antibiofilm activity. Both porous and non-porous PVDF composites have shown antibacterial characteristics when stimulated at a mechanical frequency of 4Hz being the effect boosted when AgNPs were incorporated in the nanocomposite, reducing in more than 80 % the bacterial growth in planktonic and biofilm form. The electroactive environments sensitize the bacteria allowing the action of extremely low doses of AgNPs. Importantly, the material did not compromise the viability of mammalian cells, thus being considered biocompatible. The piezoelectric stimulation of PVDF-based polymeric films may represent a breakthrough in the development of antibacterial coatings for devices used at hospital setting, taking advantage on the use of mechanical stimuli (pressure/touch) to exert antibacterial and antibiofilm activity.
{"title":"Exploring Electroactive Microenvironments in Polymer-Based Nanocomposites to Sensitize Bacterial Cells to Low Doses of Antimicrobials","authors":"J. Moreira, M. Fernandes, Estela O. Carvalho, A. Nicolau, V. Lazić, V. Lazić, J. Nedeljković, S. Lanceros‐Méndez","doi":"10.2139/ssrn.3805156","DOIUrl":"https://doi.org/10.2139/ssrn.3805156","url":null,"abstract":"The search for novel antimicrobial strategies capable of avoiding resistance mechanisms in bacteria are highly needed due to the alarming emergence of antimicrobial resistance. The application of physical stimuli as a mean of sensitizing bacteria for the action of antimicrobials on otherwise resistant bacteria or by allowing the action of an extremely low quantity of antimicrobials may be seen as a breakthrough for such purpose. This work proposes the development of antibacterial nanocomposites using the synergy between the electrically active microenvironments, created by a piezoelectric polymer (poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE)), with green-synthesized silver nanoparticles (AgNPs). The electrical microenvironment is generated via mechanical stimulation of piezoelectric PVDF-TrFE/AgNPs films using a lab-made mechanical bioreactor. The generated material’s electrical response further translates to bacterial cells, which in combination with AgNPs and the specific morphological features of the material induce important antibacterial and antibiofilm activity. Both porous and non-porous PVDF composites have shown antibacterial characteristics when stimulated at a mechanical frequency of 4Hz being the effect boosted when AgNPs were incorporated in the nanocomposite, reducing in more than 80 % the bacterial growth in planktonic and biofilm form. The electroactive environments sensitize the bacteria allowing the action of extremely low doses of AgNPs. Importantly, the material did not compromise the viability of mammalian cells, thus being considered biocompatible. The piezoelectric stimulation of PVDF-based polymeric films may represent a breakthrough in the development of antibacterial coatings for devices used at hospital setting, taking advantage on the use of mechanical stimuli (pressure/touch) to exert antibacterial and antibiofilm activity.","PeriodicalId":18341,"journal":{"name":"Materials Science eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84623676","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An important group of NiTi-based alloys employed in applications exhibits an intermediate R-phase transformation, which substantially modifies the material’s thermomechanical response. Finite element analysis of products from such alloys requires a constitutive model covering the two-stage transformation sequence in its full thermodynamic nature. We propose an enhanced constitutive model for NiTi-based alloys, which incorporates R-phase as a distinctive phase with loading-dependent transformation strain. We validate the model on a newly acquired extensive experimental dataset on the thermomechanical response of Ni48 Ti49 Fe3 shape memory alloy and illustrate the capabilities of its implementation into finite element software on a computational structural analysis of a tightening ring.
{"title":"Experimentally Validated Constitutive Model for NiTi-based Shape Memory Alloys Featuring Intermediate R-phase Transformation: A Case Study of Ni 48 Ti 49 Fe 3","authors":"Mark. Frost, Alan Jurysta, L. Heller, P. Sedlák","doi":"10.2139/ssrn.3805227","DOIUrl":"https://doi.org/10.2139/ssrn.3805227","url":null,"abstract":"An important group of NiTi-based alloys employed in applications exhibits an intermediate R-phase transformation, which substantially modifies the material’s thermomechanical response. Finite element analysis of products from such alloys requires a constitutive model covering the two-stage transformation sequence in its full thermodynamic nature. We propose an enhanced constitutive model for NiTi-based alloys, which incorporates R-phase as a distinctive phase with loading-dependent transformation strain. We validate the model on a newly acquired extensive experimental dataset on the thermomechanical response of Ni<sub>48</sub> Ti<sub>49</sub> Fe<sub>3</sub> shape memory alloy and illustrate the capabilities of its implementation into finite element software on a computational structural analysis of a tightening ring.","PeriodicalId":18341,"journal":{"name":"Materials Science eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82335016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We investigated the effect of twin Schmid factor on the tension twinning of individual grains in deformed textured Mg-3Al-1Zn samples. The samples were deformed to ~3% strain (normal-direction compression and tension, rolling-direction compression and tension, and 45 o compression). Statistical analyses on the electron backscatter diffraction results revealed tension twinning generally obeys the Schmid law for individual grains, regardless of whether the global stress state favors tension twinning or not. The strong dependence of tension twinning on Schmid factor is in contrast to the reported weak correlation of dislocations and Schmid factor in the same material system. Such observations are anticipated to advance the understanding of the Schmid factor effect on the deformation behavior of polycrystalline Mg alloys.
{"title":"Effect of Twin Schmid Factor on the Tension Twinning Activities in a Highly Textured Mg-3Al-1Zn","authors":"Dexin Zhao, Jiaqi Dong, K. Xie","doi":"10.2139/ssrn.3805155","DOIUrl":"https://doi.org/10.2139/ssrn.3805155","url":null,"abstract":"We investigated the effect of twin Schmid factor on the tension twinning of individual grains in deformed textured Mg-3Al-1Zn samples. The samples were deformed to ~3% strain (normal-direction compression and tension, rolling-direction compression and tension, and 45 o compression). Statistical analyses on the electron backscatter diffraction results revealed tension twinning generally obeys the Schmid law for individual grains, regardless of whether the global stress state favors tension twinning or not. The strong dependence of tension twinning on Schmid factor is in contrast to the reported weak correlation of dislocations and Schmid factor in the same material system. Such observations are anticipated to advance the understanding of the Schmid factor effect on the deformation behavior of polycrystalline Mg alloys.","PeriodicalId":18341,"journal":{"name":"Materials Science eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77810770","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Eleana Manousiouthakis, Junggeon Park, John G Hardy, Jae Young Lee, Christine E Schmidt
Carbon-based conductive and electroactive materials (e.g., derivatives of graphene, fullerenes, polypyrrole, polythiophene, polyaniline) have been studied since the 1970s for use in a broad range of applications. These materials have electrical properties comparable to those of commonly used metals, while providing other benefits such as flexibility in processing and modification with biologics (e.g., cells, biomolecules), to yield electroactive materials with biomimetic mechanical and chemical properties. In this review, we focus on the uses of these electroconductive materials in the context of the central and peripheral nervous system, specifically recent studies in the peripheral nerve, spinal cord, brain, eye, and ear. We also highlight in vivo studies and clinical trials, as well as a snapshot of emerging classes of electroconductive materials (e.g., biodegradable materials). We believe such specialized electrically conductive biomaterials will clinically impact the field of tissue regeneration in the foreseeable future. STATEMENT OF SIGNIFICANCE: This review addresses the use of conductive and electroactive materials for neural tissue regeneration, which is of significant interest to a broad readership, and of particular relevance to the growing community of scientists, engineers and clinicians in academia and industry who develop novel medical devices for tissue engineering and regenerative medicine. The review covers the materials that may be employed (primarily focusing on derivatives of fullerenes, graphene and conjugated polymers) and techniques used to analyze materials composed thereof, followed by sections on the application of these materials to nervous tissues (i.e., peripheral nerve, spinal cord, brain, optical, and auditory tissues) throughout the body.
{"title":"Towards the Translation of Electroconductive Organic Materials for Regeneration of Neural Tissues","authors":"Eleana Manousiouthakis, Junggeon Park, John G Hardy, Jae Young Lee, Christine E Schmidt","doi":"10.2139/ssrn.3802820","DOIUrl":"https://doi.org/10.2139/ssrn.3802820","url":null,"abstract":"Carbon-based conductive and electroactive materials (e.g., derivatives of graphene, fullerenes, polypyrrole, polythiophene, polyaniline) have been studied since the 1970s for use in a broad range of applications. These materials have electrical properties comparable to those of commonly used metals, while providing other benefits such as flexibility in processing and modification with biologics (e.g., cells, biomolecules), to yield electroactive materials with biomimetic mechanical and chemical properties. In this review, we focus on the uses of these electroconductive materials in the context of the central and peripheral nervous system, specifically recent studies in the peripheral nerve, spinal cord, brain, eye, and ear. We also highlight in vivo studies and clinical trials, as well as a snapshot of emerging classes of electroconductive materials (e.g., biodegradable materials). We believe such specialized electrically conductive biomaterials will clinically impact the field of tissue regeneration in the foreseeable future. STATEMENT OF SIGNIFICANCE: This review addresses the use of conductive and electroactive materials for neural tissue regeneration, which is of significant interest to a broad readership, and of particular relevance to the growing community of scientists, engineers and clinicians in academia and industry who develop novel medical devices for tissue engineering and regenerative medicine. The review covers the materials that may be employed (primarily focusing on derivatives of fullerenes, graphene and conjugated polymers) and techniques used to analyze materials composed thereof, followed by sections on the application of these materials to nervous tissues (i.e., peripheral nerve, spinal cord, brain, optical, and auditory tissues) throughout the body.","PeriodicalId":18341,"journal":{"name":"Materials Science eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82026720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Zhao, X. Jia, Chen Chen, Fucheng Zhang, Tiansheng Wang
Ultrafine ferrite with a grain size range of 0.5-2 μm was introduced into low-temperature bainitic medium-carbon high-silicon steel through partially austenitization of cold-rolled tempered troostite followed by austempering at temperatures of 10 °C above martensite starting temperature. The microstructures and mechanical properties were studied and compared with conventional low-temperature bainitic steel obtained by full austenitization of cold-rolled tempered troostite followed by austempering at a temperature of 10 °C above martensite starting temperature. The results show that introduction of ~4 vol% ultrafine ferrite into low-temperature bainite can simultaneously enhance the ultimate tensile strength, yield strength, and impact toughness to 1614 MPa, 1074 MPa, and 52 J (half-width Charpy U-notch specimen) without loss of ductility, increasing by approximately 6.5%, 12.5%, and 62.5%, respectively.
{"title":"Simultaneously Improved Strength and Impact Toughness by Introducing Ultrafine Ferrite in Low-Temperature Bainitic Steel","authors":"T. Zhao, X. Jia, Chen Chen, Fucheng Zhang, Tiansheng Wang","doi":"10.2139/ssrn.3797416","DOIUrl":"https://doi.org/10.2139/ssrn.3797416","url":null,"abstract":"Ultrafine ferrite with a grain size range of 0.5-2 μm was introduced into low-temperature bainitic medium-carbon high-silicon steel through partially austenitization of cold-rolled tempered troostite followed by austempering at temperatures of 10 °C above martensite starting temperature. The microstructures and mechanical properties were studied and compared with conventional low-temperature bainitic steel obtained by full austenitization of cold-rolled tempered troostite followed by austempering at a temperature of 10 °C above martensite starting temperature. The results show that introduction of ~4 vol% ultrafine ferrite into low-temperature bainite can simultaneously enhance the ultimate tensile strength, yield strength, and impact toughness to 1614 MPa, 1074 MPa, and 52 J (half-width Charpy U-notch specimen) without loss of ductility, increasing by approximately 6.5%, 12.5%, and 62.5%, respectively.","PeriodicalId":18341,"journal":{"name":"Materials Science eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82986069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pengcheng Zhu, Yajie Zhao, Shradha Agarwal, J. Hay, J. Henry, S. Zinkle
Estimations of bulk hardness from nanoindentation data are frequently subject to considerable uncertainties, due to indentation size effects, potential pileup effects, and potential influence of surface quality or test methods. In this study, we examined materials science principles of nanoindentation test methods to enable accurate prediction of bulk hardness for a series of high purity Fe and Fe alloys containing 3-25 wt. %Cr. These materials were tested in as-annealed and thermally aged (100-900 hours at 475 oC for 14-25 wt. %Cr) conditions to produce Cr-rich a’ precipitates of varying size and density (bulk Vickers hardness values of ~50 to 350 VHN). Nanoindentation performed with a Berkovich indenter using constant strain rate (0.05 to 0.5 /s) and constant loading rate test methods provided comparable bulk equivalent hardness (H0) extracted by Nix-Gao model, indicating a weak strain rate sensitivity of the investigated materials at room temperature. Results from electropolished and fine mechanically polished samples were found to give comparable measured hardness. Conversely, material pileup adjacent to the indented area produced a 7-20% correction to the indent contact area. The Nix-Gao fitted nanoindentation H0 after pileup corrections agreed quantitatively better with the bulk Vickers hardness than the uncorrected H0 values. The model-predicted (dispersed barrier hardening superposition) and measured strength values agreed for aged Fe18Cr, indicating that Nix-Gao model combined with pileup corrections significantly improved the accuracy of hardness evaluation by nanoindentation. Analytic and experimental analyses demonstrate that inappropriate methods such as hardness ratios or changes at a reference depth (applied in many prior nanoindentation studies) can cause quantitative errors in bulk hardness estimates as large as 60% due to indentation size effects.
{"title":"Challenges to Accurate Evaluation of Bulk Hardness from Nanoindentation Testing at Low Indent Depths","authors":"Pengcheng Zhu, Yajie Zhao, Shradha Agarwal, J. Hay, J. Henry, S. Zinkle","doi":"10.2139/ssrn.3793936","DOIUrl":"https://doi.org/10.2139/ssrn.3793936","url":null,"abstract":"Estimations of bulk hardness from nanoindentation data are frequently subject to considerable uncertainties, due to indentation size effects, potential pileup effects, and potential influence of surface quality or test methods. In this study, we examined materials science principles of nanoindentation test methods to enable accurate prediction of bulk hardness for a series of high purity Fe and Fe alloys containing 3-25 wt. %Cr. These materials were tested in as-annealed and thermally aged (100-900 hours at 475 oC for 14-25 wt. %Cr) conditions to produce Cr-rich a’ precipitates of varying size and density (bulk Vickers hardness values of ~50 to 350 VHN). Nanoindentation performed with a Berkovich indenter using constant strain rate (0.05 to 0.5 /s) and constant loading rate test methods provided comparable bulk equivalent hardness (H0) extracted by Nix-Gao model, indicating a weak strain rate sensitivity of the investigated materials at room temperature. Results from electropolished and fine mechanically polished samples were found to give comparable measured hardness. Conversely, material pileup adjacent to the indented area produced a 7-20% correction to the indent contact area. The Nix-Gao fitted nanoindentation H0 after pileup corrections agreed quantitatively better with the bulk Vickers hardness than the uncorrected H0 values. The model-predicted (dispersed barrier hardening superposition) and measured strength values agreed for aged Fe18Cr, indicating that Nix-Gao model combined with pileup corrections significantly improved the accuracy of hardness evaluation by nanoindentation. Analytic and experimental analyses demonstrate that inappropriate methods such as hardness ratios or changes at a reference depth (applied in many prior nanoindentation studies) can cause quantitative errors in bulk hardness estimates as large as 60% due to indentation size effects.","PeriodicalId":18341,"journal":{"name":"Materials Science eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79925153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Efforts to enhance the solar conversion efficiency have prevailed for decades. There is a growing interest in improving the spectral response of solar modules, especially in harvesting UV photons, which offer intense energy in a narrow wavelength range. To harvest UV photons and reduce reflection without interfering with the formulas and manufacturing process of solar cells, in this work, thin films that possess downshifting and antireflection capabilities were fabricated on the cover glass of multicrystalline Si solar cells. The thin films were composed of graded index layers of europium-doped yttrium orthovanadate (YVO4:Eu) and hollow silica nanoparticles (HSNPs). The design of the composite thin films was assisted by the FDTD mathematical model that simulated the refractive index and thickness of each layer to obtain the optimum transmittance. The cover glass with multifunctional thin films harvested more than 30% of UV photons and enhanced the solar conversion efficiency by 4.12% at normal incidence compared to the uncoated cover glass.
{"title":"Downshifting and Antireflective Thin Films for Solar Module Power Enhancement","authors":"Yujuan He, Jie Liu, S. Sung, Chih-hung Chang","doi":"10.2139/ssrn.3805247","DOIUrl":"https://doi.org/10.2139/ssrn.3805247","url":null,"abstract":"Abstract Efforts to enhance the solar conversion efficiency have prevailed for decades. There is a growing interest in improving the spectral response of solar modules, especially in harvesting UV photons, which offer intense energy in a narrow wavelength range. To harvest UV photons and reduce reflection without interfering with the formulas and manufacturing process of solar cells, in this work, thin films that possess downshifting and antireflection capabilities were fabricated on the cover glass of multicrystalline Si solar cells. The thin films were composed of graded index layers of europium-doped yttrium orthovanadate (YVO4:Eu) and hollow silica nanoparticles (HSNPs). The design of the composite thin films was assisted by the FDTD mathematical model that simulated the refractive index and thickness of each layer to obtain the optimum transmittance. The cover glass with multifunctional thin films harvested more than 30% of UV photons and enhanced the solar conversion efficiency by 4.12% at normal incidence compared to the uncoated cover glass.","PeriodicalId":18341,"journal":{"name":"Materials Science eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88085779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. McCue, B. Gaskey, Michael C. Brupbacher, W. M. Buchta, A. Chuang, K. Xie, W. Kuo, J. Erlebacher
We present a new dealloying-based technique to form fully-dense and high-hardness metal composite coatings. By depositing then heat treating a TiCr alloy coating on a Ni-base superalloy, a eutectic reaction occurs at the coating/substrate interface, which drives spontaneous pattern formation in both alloys analogous to liquid metal dealloying. The coating exhibits a significantly higher hardness (15 GPa) than both the starting alloy (3.7 GPa) and precursor coating (6 GPa), measured by micro- and nanoindentation, while maintaining the ability to plastically deform during micro-indentation experiments without apparent cracking or spallation. The flexibility and scalability of the dealloying process used here demonstrates a promising route towards protective coatings for structural alloys.
{"title":"Self-Organized High-Hardness Thermal Spray Coatings","authors":"I. McCue, B. Gaskey, Michael C. Brupbacher, W. M. Buchta, A. Chuang, K. Xie, W. Kuo, J. Erlebacher","doi":"10.2139/ssrn.3793930","DOIUrl":"https://doi.org/10.2139/ssrn.3793930","url":null,"abstract":"We present a new dealloying-based technique to form fully-dense and high-hardness metal composite coatings. By depositing then heat treating a TiCr alloy coating on a Ni-base superalloy, a eutectic reaction occurs at the coating/substrate interface, which drives spontaneous pattern formation in both alloys analogous to liquid metal dealloying. The coating exhibits a significantly higher hardness (15 GPa) than both the starting alloy (3.7 GPa) and precursor coating (6 GPa), measured by micro- and nanoindentation, while maintaining the ability to plastically deform during micro-indentation experiments without apparent cracking or spallation. The flexibility and scalability of the dealloying process used here demonstrates a promising route towards protective coatings for structural alloys.","PeriodicalId":18341,"journal":{"name":"Materials Science eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77420389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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