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Electrocatalysis plays a significant role in many value-added chemical transformations in advanced clean energy production technologies such as fuel cells and metal–air batteries. Among various catalysts, traditional materials made of noble metals are widely used as electrocatalysts; however, they often suffer from disadvantages such as low abundance, low surface area, and high cost. The intrinsic advantages of metal–organic frameworks (MOFs) have been explored in various application fields. However, their insulating property and poor electrolyte stability limited their utility in desirable technologies such as fuel cells, batteries, and supercapacitors. New designs and synthetic strategies have ushered in a new era of fabricating electrocatalytically active MOFs for energy and environmental concerns. This review details the synthetic approaches to fabricate electrocatalytically active pristine MOFs and their recent progress in electrocatalytic applications such as oxygen reduction, oxygen/hydrogen evolution, and carbon dioxide reduction. The present review assists in advancing MOF research in emergent technologies such as fuel cells and metal–air batteries. [ABSTRACT FROM AUTHOR]

We report epitaxially grown new two-dimensional metal–organic framework (MOF) thin films on a self-assembled monolayer (SAM). We fabricated these epitaxial thin-films using stepwise layer-by-layer seeding followed by solvothermal treatment. The MOF thin films exhibit ultrafast structural flexibility (through breathing) compared to their bulk samples upon uptake of organic guest molecules. [ABSTRACT FROM AUTHOR]

Inspired by copper‐based oxygen reduction biocatalysts, we have studied the electrocatalytic behavior of a Cu‐based MOF (Cu‐BTT) for oxygen reduction reaction (ORR) in alkaline medium. This catalyst reduces the oxygen at the onset (Eonset) and half‐wave potential (E1/2) of 0. 940 V and 0.778 V, respectively. The high halfway potential supports the good activity of Cu‐BTT MOF. The high ORR catalytic activity can be interpreted by the presence of nitrogen‐rich ligand (tetrazole) and the generation of nascent copper(I) during the reaction. In addition to the excellent activity, Cu‐BTT MOF showed exceptional stability too, which was confirmed through chronoamperometry study, where current was unchanged up to 12 h. Further, the 4‐electrons transfer of ORR kinetics was confirmed by hydrodynamic voltammetry. The oxygen active center namely copper(I) generation during ORR has been understood by the reduction peak in cyclic voltammetry as well in the XPS analysis. [ABSTRACT FROM AUTHOR]

Here we report a new three-dimensional nickel-based hybrid structure [Ni3(BTB)2(BPE)4(H2O)2]·2DMF·2H2O, 1 [where BTB = 1,3,5-tris(4-carboxyphenyl)benzene and BPE = 1,2-bis((4-pyridyl)ethane)], which exhibits long-range ferromagnetism and semiconductor behavior. The dipolar interaction between the magnetic spins is suggested to explain the development of long-range ferromagnetic ordering, where the superexchange interaction can be unwanted due to the large distance between the magnetic spins. Optical band gap and resistance vs. temperature measurements reveal the semiconductor nature of this compound. The density of states calculations shed light towards the origin of the low band gap value. [ABSTRACT FROM AUTHOR]

Abstract We have synthesized three new cobalt based inorganic-organic hybrid materials by solvothermal method, these structure have either angular or linear trimeric cobalt cluster as a secondary building unit. In case of compounds 1 and 2 , the cobalt centers were corner shared through common bridging –OH group to form the triangular cluster. Interestingly in compound 1 , the monomeric cobalt center is linked with framework while in compound 2 the monomeric cobalt unit is trapped inside the pore of the framework. In compound 3 , the cobalt centers are corner shared to form the linear trimeric cluster. These trimeric cobalt clusters are connected through BTB ligands to form two-dimensional coordination polymer structure. All three structures have common BTB (1,3,5-Tris(4-carboxyphenyl)benzene) ligand, whereas in case of compound 1 and 2 , BPE (1,2-bis (4-pyridyl) ethane) and for 3 , DPB (1,4-Di(4-pyridyl)benzene) have been used as co-ligand. The magnetic measurements revealed the large and positive values of θ CW in compounds 1 and 2. This implies that the dominant interaction between the Co spins are antiferromagnetic in nature. In case of compound 3, the structure is quite different from the other two compounds. In compound 3 the coupling between the Co-atoms drastically reduce compared to compounds 1 and 2 , respectively, resulting in a paramagnetic behavior. We have also measured the optical band gap energy for all three compounds and results show that the band gap is relatively low and it is in the range of 1.82 eV to 1.89 eV. Graphical abstract We synthesized three new cobalt based inorganic-organic hybrid materials, in which compound 1 and 2 contains triangular Co2+ clusters while compound 3 has linear Co2+ clusters. The magnetic measurements revealed that the triangular based clusters show strong antiferromagnetic whereas the linear cluster is weak antiferromagnetic behavior. fx1 Highlights • Three new cobalt-based hybrid materials were obtained by solvothermal method. • Compound 1 and 2 contain triangular Co2+ clusters while compound 3 has linear Co2+ cluster. • The triangular based clusters show strong antiferromagnetic and the linear cluster show weak antiferromagnetic behavior. [ABSTRACT FROM AUTHOR]

Cu-Al-Ni and Cu-Al-Ni-Mn shape memory alloys are deposited on Kapton polyimide sheets by a physical evaporation technique. Detailed investigations on the morphological, structural and thermal behaviour of the ternary and quaternary alloys are conducted. The developed samples exhibit an increase in martensite structures and decrease in transformation temperatures after Mn additions. Furthermore, the suppression of Cu 3 Al precipitates was evident from XRD analysis. The thermomechanical behaviour was analysed by actuating the bimorphs through Joule heating under varying mechanical loads. Fatigue analysis of the bimorphs reveals a superior performance for Cu-Al-Ni-Mn, exhibiting less than 30% loss in displacement after 15,000 cycles. [ABSTRACT FROM AUTHOR]

For the first time, NiTi shape memory alloy was successfully joined by Friction Stir Welding (FSW). The weld showed significant grain refinement without formation of detrimental phases. The yield strength of the weld joint increased by 17% as compared to the base metal without substantial change in shape memory behaviour. [ABSTRACT FROM AUTHOR]

In this work, a two-way displacing Cu-Al-Ni/Polyimide shape memory alloy bi-morph without any post processing has been developed. The forward stroke was achieved with shape memory effect and the return stroke was due to the influence of flexible polyimide substrate. A custom made setup with electrical heating was developed to investigate the life cycle of the bi-morph at different voltages, ranging from 2 V to 3 V. The austenite transformation temperatures of the bi-morph, was found to be A s = 215 °C and A f = 240 °C. Shape recovery ratio was calculated and the shape memory alloy deposited on 75 μm thick polyimide sheet exhibited better recoverability than 50 μm thick sheets. Further, maximum displacement of 19 mm was observed from the edge of the bi-morph through plate heating. The effect of substrate thickness on the life cycle behavior of the bi-morph was investigated. The bi-morph showed minor signs of deformation when actuated at 0.5 Hz after 500 cycles. In addition the structural, morphological and thermal behavior of the SMA bi-morph has been investigated in detail. [ABSTRACT FROM AUTHOR]

Background: Application of e-learning and e-modules in medical education has been shown to have a positive impact on learning outcomes among all types of learners, across diverse educational settings. Despite its benefits, e-learning and e-modules has not yet reached its full potential in medical education in India. Objective of this study is to evaluate the perception of undergraduate students regarding e-learning and e-modules using an appreciative inquiry tool SOAR (Strengths, Opportunities, Aspirations, Results) analysis, and to identify the barriers and challenges for the same. Methods: This longitudinal study was conducted among participants from three consecutive batches (n = 250 x 3) of first-year medical students and two consecutive batches (n = 100 x 2) of first-year dental students. The sample was selected using a purposive sampling method. Two structured and validated questionnaires were developed for this study based on the modified Zhou's Mixed Methods Model; the 'Knowledge, Attitude and Practice' Questionnaire (KAPQ) on e-learning and the feedback questionnaire (FBQ) on e-modules. The questionnaires were administered via MOODLE / hard copy, before and after the implementation of e-modules, respectively. Identified strengths, potential opportunities, probable aspirations and likely results for e-learning and e-modules were tabulated based on the qualitative analysis of perceptions of large number students sampled across three years. Results: Six hundred and ninety students returned both questionnaires representing a response rate of 76.6%. Nine themes were identified in the "Strengths" domain as follows: Regular Update of Knowledge, Innovative Learning, Availability, Knowledge Sharing, Abundance of Information, Accessibility, Source of Knowledge, Creativity, and Increased Engagement. Eleven themes were identified in the "Opportunities" domain as follows: Clinical Skills training, Timesaving, Flexibility, Creativity, Increased engagement, Standardized content, Capacity building for students, Capacity building for faculty, Skills training, and Self-assessment. Thirteen themes were identified under the "Aspirations" domain with the three key themes being "maintaining and building on current strengths", "increasing potential opportunities", and "addressing the barriers and challenges identified in the responses to the KAPQ and FBQ questionnaire". Four themes identified for 'Barriers' were eye strain, distractions, preference for conventional methodologies, and internet connectivity. Conclusions: The findings of this qualitative study are based on the responses received from first-year medical and dental students of a Private University in Chennai, India. In this population of students, implementation of e-learning as blended learning using structured and interactive e-modules may provide more engagement during learning as well as support self-directed learning (SDL) directly or indirectly. Adoption of blended learning with e-modules as an integral part of curriculum planning may be beneficial for the achievement of Competency-Based Medical Education (CBME) goals in India. [ABSTRACT FROM AUTHOR]

Correction for 'Organic guest molecule induced ultrafast breathing of an epitaxially grown metal–organic framework on a self-assembled monolayer' by Purna Chandra Rao et al., Chem. Commun., 2021, DOI: 10.1039/d1cc03721h. [ABSTRACT FROM AUTHOR]

The viability of utilizing electron beam evaporation technique for the development of NiTi shape memory alloy (SMA) thin films on kapton polyimide (flexible substrate) has been investigated. The actuation characteristics of the SMA/polyimide structure were evaluated using shape recovery analysis and electrical actuation. The maximum shape recovery ratio of 1.375 was attained with butterfly configuration during shape recovery analysis. The SMA/polyimide stimulated via Joule heating has displayed a maximum displacement of 0.9 mm at 3 V. The surface morphology examined through scanning electron microscope shows the smooth surface without any pores. The thermal stability analyzed using thermogravimetric analysis shows the NiTi SMA thin film can withstand higher temperature above 550 °C without any damage to the SMA/polyimide structure. The stress/strain behavior of the SMA/polyimide structure was analyzed as a function of temperature. The differential scanning calorimetry has showed that the austenite phase transformation temperature lies in the range of 45°C-95 °C. The temperature sweep test performed using dynamic mechanical analyzer recorded a drastic drop in storage modulus in the same phase transformation temperature range as that of DSC. The UV–Vis spectroscopy reveals the NiTi/polyimide structure has high reflective surface in the visible region which aids in the application of reflectors. SMA/polyimide structure can be used as a smart optical mirror in interferometry technique owing to its optical reflectivity. • NiTi Shape Memory Alloy thin film was fabricated using E-beam evaporation technique. • Maximum shape recovery ratio of 1.375 was obtained with butterfly configuration. • Electrical actuation was realized at two different frequencies such as 0.125 Hz and 0.25 Hz. • A maximum displacement of 0.9 mm was obtained through electrical actuation. [ABSTRACT FROM AUTHOR]

Post‐synthetic modification (PSM) of metal–organic framework (MOF) compounds is a useful technique for preparing new MOFs that can exhibit or enhance many of the properties of the parent MOFs. PSM can be carried out by a number of approaches such as modifying the linker (ligand) and/or metal node, and adsorption/exchange of guest species. The surface environment of the MOF can be modified to increase structural stability as well as introducing desired properties. There is considerable scope in widening the applications of the MOF with compatible metal or ligand employing the PSM. This review focuses on the recent developments of modified materials through PSM, which augers well for the chemical modification and functionalization of MOFs. In this review, different types of PSM methods are presented in an orderly manner, and the diverse applications of resultant frameworks are described and discussed. [ABSTRACT FROM AUTHOR]

Abstract: A series of lanthanide(III) based coordination polymers have been synthesized using chelidamic acid (CA) as a ligand, [Ln(C7H2NO5)(H2O)3].H2O (Ln = Eu, Gd, Tb, and Dy). All the compounds were prepared by solvothermal technique using H2O-DMF as solvents (4:1, volume ratio). Compounds were characterized through various instrumental techniques such as single-crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, IR spectroscopy, etc. In all the cases lanthanide ion adopts distorted dodecahedron geometry. And these dodecahedrons are connected through chelidamic acid ligand to form the two-dimensional structure. These layers are H-bonded to form the three-dimensional supramolecular structure. The optical band gap energy measurements exhibit that the variation of the band gap energy is independent of the f-electrons. This is due to the weak bonding connectivity between the metal ion and ligands, which could not perturb the density of states significantly. The variable-temperature magnetic measurements exhibit the paramagnetic behavior of all the compounds though the effective magnetic moments rise with increasing number of f-electrons. The present study illustrates the usefulness of the lanthanides for the structure building as well as the role of f-electrons for opto-electronic behaviors.Graphical Abstract: SYNOPSIS A series of two-dimensional isostructural Lanthanum coordination polymers have been synthesized and comparisons of various properties have been made. Figure shows the reaction scheme for the observed coordination polymer. [ABSTRACT FROM AUTHOR]

In this investigation, a shape memory alloy (SMA) based aerodynamic composite fin has been developed. Under optimized condition, SMA based composite fin structure shows maximum deflection of 65 mm before the failure condition, where the diameter of 5 % pre-strained SMA wire was 0.5 mm at 6 % of SMA to Composite ratio (volume of SMA/volume of composite). [Display omitted] • Smart composite fin for aerodynamic application. • Investigation of actuation behaviour of SMA based adaptive composite structure. • Optimization of the process parameters of SMA composite structure development. • Composite fin shows a maximum deflection of 65 mm before failure point, under optimized condition. In this investigation, a shape memory alloy (SMA) based aerodynamic composite Fin has been developed. In general, the missile fins play a crucial role in changing the direction of a conventional missile using motor arrangement. Therefore, SMA-based composite Fin might be a promising alternative to control the direction without using the motor. The composite Fin is made of laminated fiber polymer and SMA wire. Initially, rectangular composite structures have been developed with different wire prestraining percentages, lengths, diameters, and configurations to understand their electrical actuation behavior. Based on the experiments, optimized parameters have been derived and applied to the composite fin. Adaptive composite actuation was performed via selective joule heating on the composite fin. Under optimized conditions, SMA-based composite structure shows maximum displacement of 65 mm with a maximum angle of 60 degrees before failure, where the diameter of 5 % pre-strained SMA wire was 0.5 mm at 6 % of SMA to Composite ratio (volume of SMA/volume of composite). Maximum displacement and failure analysis of the composite structure has been analyzed at optimized parameters. [ABSTRACT FROM AUTHOR]

• Cu based Shape Memory Alloy coated optical fiber sensor was designed and fabricated. • Higher sensitivity of Cu-Al-Mn-Ni SMA coated fiber sensor for more than 1000 cycles. • Enhanced ductility and phase transformation temperature with Mn and Ni addition. • Austenite transformation temperature was found to be A s = 250 °C and A f = 350 °C. • The SMA coated fiber optic sensor was proposed to monitor temperature in 3D printer. Copper based Shape Memory Alloy (SMA) coated optical fiber sensors have been developed for temperature dependent applications. Cu-Al-Mn-Ni (79.6%-11.9%-5%-3.5%) shape memory alloy has been coated over optical fiber using flash evaporation based physical vapour deposition technique. In order to obtain uniform coating and introduce strain during fiber fabrication process, an in-situ fixture with rotating drive assembly had been designed. SEM, XRD and DSC results have confirmed the uniformity, crystallinity and phase transformation of the SMA coated optical fiber. Phase transformation has been confirmed using DSC at 350 °C. The developed sensor has been characterized for the entire working range of 250 °C to 350 °C with a resolution of 0.5 °C. Losses in optical fiber signal during actuation have been measured indirectly using equivalent displacement obtained against change in temperature profile. Application of the developed smart optical fiber sensor for condition monitoring of additive manufacturing machine has been explored. [ABSTRACT FROM AUTHOR]

In this work, the thermomechanical behavior of NiTi, NiTiCu, CuAlNi, CuAlNiMn shape memory alloy (SMA) thin films deposited on Kapton polyimide substrate has been investigated. The actuation characteristics were studied using plate heating and Joule heating. Plate heating was utilized to realize the curvature/shape change of the developed SMA/Kapton composites during heating and cooling cycles. The SMA/Kapton composite developed with copper based SMA displayed rapid shape change beyond 150 °C and exhibited substantial displacement, which was not observed with NiTi based alloys. However, the hysteresis observed with NiTi SMA/Kapton composites was negligible as compared to CuAlNi alloys. Parameters such as voltage, load, and frequency were varied with Joule heating in order to analyze the thermomechanical properties in detail towards real time applications. Further the actuation behavior was corroborated with material properties such as surface morphology and stress-strain behavior. A conceptual design for Stewart platform and SMA belt exploiting the SMA/Kapton composite actuation behavior was proposed for various functional applications. [ABSTRACT FROM AUTHOR]

Nitinol, a shape-memory alloy (SMA), is gaining popularity for use in various applications. Machining of these SMAs poses a challenge during conventional machining. Henceforth, in the current study, the wire-electric discharge process has been attempted to machine nickel-titanium (Ni55.8Ti) super-elastic SMA. Furthermore, to render the process viable for industry, a systematic approach comprising response surface methodology (RSM) and a heat-transfer search (HTS) algorithm has been strategized for optimization of process parameters. Pulse-on time, pulse-off time and current were considered as input process parameters, whereas material removal rate (MRR), surface roughness, and micro-hardness were considered as output responses. Residual plots were generated to check the robustness of analysis of variance (ANOVA) results and generated mathematical models. A multi-objective HTS algorithm was executed for generating 2-D and 3-D Pareto optimal points indicating the non-dominant feasible solutions. The proposed combined approach proved to be highly effective in predicting and optimizing the wire electrical discharge machining (WEDM) process parameters. Validation trials were carried out and the error between measured and predicted values was negligible. To ensure the existence of a shape-memory effect even after machining, a differential scanning calorimetry (DSC) test was carried out. The optimized parameters were found to machine the alloy appropriately with the intact shape memory effect. [ABSTRACT FROM AUTHOR]

The influence of growth substrate temperature on the development of CuAlNi shape memory alloy (SMA) over Kapton Polyimide sheet and its effect on tuning the thermomechanical behavior has been investigated. The SMA bi-morph was synthesized at varying substrate temperatures ranging from 100 °C–200 °C. Two-way shape memory effect could be demonstrated by the bi-morps without any post-processing and training, due to pre-straining of the flexible substrates. The deposited SMA film was responsible for the forward displacement and the return was achieved because of flexible kapton polyimide substrate. To investigate the life cycle behavior of the as developed SMA bi-morph, an in-house life cycle setup was developed with Joule heating as the actuation source. The cyclic behavior was investigated for 500 cycles, at three varying voltages of 2 V, 2.5 V and 3 V with an actuation frequency of 0.5 Hz. The film deposited with growth substrate temperature of 100 °C and 200 °C showed a maximum displacement of 0.6 mm and 0.9 mm, whereas samples prepared with substrate heating at 150 °C showed a maximum displacement of 2.6 mm with actuation voltage of 3 V. To probe the influence of substrate temperature in tuning the thermomechanical behavior, an analysis on the structural, morphological, and thermal properties of the bi-morphs has been investigated in detail. [ABSTRACT FROM AUTHOR]

• Stages on ε(T) curve are caused by various composition of NiTi phase in the layers. • WAAM sample demonstrates only 3% of recoverable strain due to a texture. • Cracks form in brittle Ti 2 Ni precipitates that leads to sample failure. Peculiarities of the recoverable strain variation on cooling and heating under a stress was studied in the NiTi sample produced by wire arc additive manufacturing (WAAM). The strain variation occurred in some stages due to the layers underwent the martensitic transformations at different temperatures. The recoverable strain on cooling and heating under a stress of the NiTi WAAM sample was three times less than in the alloys produced by conventional technology. This may be caused by texture that is characterized by the smallest recoverable strain. The sample fracture occurred on cooling under 400 MPa in the middle part of the second layer due to the formation of cracks in the brittle Ti 2 Ni precipitates. [ABSTRACT FROM AUTHOR]

In this work, we have a demonstrated zinc oxide (ZnO) polymer-based ecofriendly piezoelectric nanogenerator (PENG) on a paper substrate for an energy harvesting application. The ZnO thin film is developed on the paper substrate, where different doping concentrations of Sn have been investigated systematically to validate the effect of doping towards enhancing the device performance. The piezoelectric potential of the fabricated device is evaluated by applying three different loads (4 N, 8 N, 22 N), where the source of the corresponding mechanical loads is based on the object of a musical drum stick. The results suggest that the pristine ZnO PENG device can generate a maximum output voltage and current of 2.15 V and 17 nA respectively. Moreover, the ZnO PENG device doped with 2.5% Sn achieved an even higher voltage (4.15 V) and current (36 nA) compared to pristine ZnO devices. In addition, the hydrothermal growth technique used to develop Sn-doped ZnO has the benefits of high scalability and low cost. Hence, the Sn-doped PENG device is a suitable candidate for energy harvesting applications operating in both uniform and non-uniform loading conditions. [ABSTRACT FROM AUTHOR]