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Microstructural interpretation of charge transport dynamics of chemically derived ZnCo2O4 under mechanical milling
摘要： In this work, milling effect on chemically synthesized nanocrystalline Zinc Cobaltite (ZnCo2O4) has been investigated and we report how the structural and electrical properties vary with the milling span. Phase pure ZnCo2O4 has been successfully synthesized via simple and cost-effective co-precipitation method and then it has been milled for one, four and eight hours respectively. XRD confirms formation of single phase cubic structure for both milled and unmilled nano-powders. Different microstructural parameters has been estimated from Rietveld analysis, which shows particle size reduction from ~29.64 nm for unmilled sample to ~18.13 nm for eight hour milled sample. TGA-DSC curve of as prepared sample shows good temperature stability that helps to estimate the appropriate sintering temperature for the samples. TEM analysis also gives values of grain size in agreement with Reitveld analysis. Frequency dependent ac conductivity curve obeys universal Jonscher power law and temperature dependence of frequency exponent is explained by small polaron transaction. Comparable activation energies from hopping mechanism and relaxation process indicates similar transport mechanism. Superimposed scaling spectra obeys TTSP principle. AC conductivity increases with frequency as a result of hopping of the charge carriers. Smaller particles with reduced strain gives enhanced conductivity as well as enhanced value of hopping frequency. This further suggests creation of excess charge carriers in milled samples. Cole-Cole plot shows non-Debye type behavior of the samples. The dielectric loss factor increases with lowering of particle size since smaller grains contributes to faster charge conduction.
关键词： TGA-DSC,Mechanical milling,Electrical characterisation,dielectric loss factor,Microstructure
更新于2025-09-23 15:22:29
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[IEEE 2018 XV International Scientific Conference on Optoelectronic and Electronic Sensors (COE) - Warsaw, Poland (2018.6.17-2018.6.20)] 2018 XV International Scientific Conference on Optoelectronic and Electronic Sensors (COE) - Microsystems for Cell Deformability Measurements
摘要： This paper presents a new technical solution in the form of MEMS-type deformation microcytometer and a new methodology for determining the deformability of animal oocytes. As a reference method compression of the oocyte with commercial micromanipulator will be descried and compared with proposed solution. Preliminary results showing the deformation of porcine oocytes will be presented using both methods to validate the work of the microcytometer.
关键词： mechanical properties of cells,microfluidics,compression and indentation of the cell,deformability of oocytes,microcytometry,microsystem
更新于2025-09-23 15:22:29
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In situ x-ray diffraction analysis of 2D crack patterning in thin films
摘要： In this work, the effect of the loading path on the multicracking of Nickel thin films on Kapton substrate was studied thanks to an experimental set-up combining controlled biaxial deformation, x-ray diffraction and digital image correlation. Samples were biaxially stretched up to 10% strain following either a single equibiaxial path or a complex one consisting of loading successively along each of the axes of the cruciform specimen. While the first path leads to a mud-crack pattern (random), the second leads to a roman-bricks one (square). Moreover, the in situ x-ray diffraction experiments show that the stress field developed in the thin film during the multicracking is clearly dependent on the loading path. By combining the study of stresses and x-ray diffraction peaks linewidth, we evidenced mechanical domains related to initiation of cracks and their multiplication for each loading path. Moreover, stress evolution in the thin film during mud-crack pattern formation is significantly smoother than in the case of roman-bricks one as represented in the plane stress space.
关键词： Synchrotron,Mechanical properties,Flexible substrates,Cracks
更新于2025-09-23 15:21:21
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Mechanically tuned molybdenum dichalcogenides (MoS2 and MoSe2) dispersed supramolecular hydrogel scaffolds
摘要： An intriguing way of tuning the mechanical efficiency of a supramolecular hydrogel network (SHGel) has been achieved by dispersing MoS2 and MoSe2. Depending upon the nature of chalcogens, the rheological properties of molybdenum dichalcogenides dispersed supramolecular hydrogel are varied. According to the variation of rheological properties, the morphologies of diverse molybdenum dichalcogenides dispersed hydrogel networks are changed. MoS2 enhances the mechanical performances of a supramolecular hydrogel. The incorporation of MoSe2 nano-fillers in the MoS2 dispersed supramolecular hydrogel lowers the mechanical properties gradually compared to the dispersion of pure MoS2. The dispersion of pure MoSe2 exclusively lowers the mechanical efficiency of the supramolecular hydrogel resulting in a drastic alteration of the morphological pattern of MoSe2 nano-fillers dispersed hydrogel under ambient condition.
关键词： MoSe2,Mechanical tuning,MoS2,Hydrogel,Microstructure
更新于2025-09-23 15:21:21
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Ultrathin Flexible Carbon Fiber Reinforced Hierarchical Metastructure for Broadband Microwave Absorption with Nano Lossy Composite and Multi-scale Optimization
摘要： The implementation of thin structure for broadband microwave absorption is challenging due to requirement of impedance match across several frequency bands and poor mechanical properties. Herein, we demonstrate a carbon fiber (CF) reinforced flexible thin hierarchical metastructure (HM) composed of lossy materials including carbonyl iron (CI), multiwall carbon nanotube (MWCNT) and silicone rubber (SR) with thickness of 5mm and optimal concentration selected from twelve formulae. Optimization for the periodical unit size is applied and impacts of structural sizes on absorption performance is also investigated. An effective process combining the vacuum bag method and the hand lay-up technique is used to fabricate the HM. Experimental reflectivity of the absorber achieves broadband absorption below -10dB in 2-4GHz and 8-40GHz. Full band in 2-40GHz is covered below -8dB. Yielding stress of the HM is increased to 24MPa with attachment of CF while the fracture strain of the composite reaches 550%. The soft HM is suitable to adhere to curved surface of objects needed to be protected from microwave radiation detection and electromagnetic interference. Enhanced mechanical properties make it possible for further practical applications under harsh service environment such as ocean and machines with constant vibration.
关键词： broadband microwave absorption,hierarchical metastructure,dielectric-magnetic lossy material,flexible,mechanical properties
更新于2025-09-23 15:21:21
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Optimization of laser welding process parameters in dissimilar joint of stainless steel AISI316/AISI1018 low carbon steel to attain the maximum level of mechanical properties through PWHT
摘要： In this investigation, laser welding process parameters have been optimized for austenitic stainless steel (AISI316) and low carbon steel (AISI1018) materials by using Taguchi based grey relational analysis. Butt joint trials were carried out using 3.5 kW di?usion-cooled slab CO2 laser by varying laser power, welding speed, and focal distance. The optimum parameters have been derived by considering the responses such as tensile strength and microhardness. The optimal parameters are laser power 2600 W, welding speed 1.5 m/min and focal distance 20 mm. The responses of the optimized parameters obtained using the grey relational analysis has been veri?ed experimentally. Formerly, the e?ect of post weld heat treatment (860 °C and 960 °C) on the mechanical properties, microstructure and chemical composition of weld zone of the optimal welded joint was investigated by using tensile test, microhardness, bend test, optical microscope, SEM and EDS. The results show that the optimal welded joint had good mechanical properties after post weld heat treatment so that the best tensile strength 475.112 MPa was obtained at 960 °C. Due to the elimination of chromium carbide and reduce grain size, the heat treated samples show high corrosion resistance at 960 °C in comparison to 860 °C.
关键词： Metallurgical properties,Laser welding,Mechanical properties,Dissimilar metals,PWHT,GRA
更新于2025-09-23 15:21:21
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Experimental evaluation of volumetric solar absorbers – Ceramic foam vs. an innovative rotary disc absorber concept
摘要： This paper presents the experimental evaluation of two volumetric solar absorber concepts. It compares the thermal performance of conventional foam absorbers with that of an innovative rotary disc absorber design. The moving absorber showed advantages regarding air temperature stability at the outlet and better operability compared to the foam absorber. Unfortunately, it is shown that the innovative rotary disc design in its present form is not competitive, neither in terms of thermal performance, nor regarding mechanical reliability and robustness. The future task is therefore to optimize the mechanical design regarding thermal fatigue, in order to obtain a robust and durable rotary absorber that can be thoroughly evaluated experimentally.
关键词： volumetric solar absorbers,ceramic foam,thermal performance,rotary disc absorber,mechanical reliability
更新于2025-09-23 15:21:21
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The electronic and elasticity properties of new half-metallic chalcogenides Cu <sub/>3</sub> TMCh <sub/>4</sub> (TM?=?Cr, Fe and Ch?=?S, Se, Te): an <i>ab initio</i> study
摘要： The ternary copper-based chalcogenides Cu3TMCh4 (TM = Cr, Fe and Ch = S, Se, Te), which have simple cubic (SC) crystal structure and conform to P(cid:1)43m space group with 215 space number, have been investigated by spin-polarised generalised gradient approximation (GGA) in the framework of density functional theory (DFT). All systems have been considered in ferromagnetic (FM) order. The mechanical and thermal properties and the electronic band structures of these systems have been investigated after the well-optimised structural parameters have been obtained. The spin-polarised electronic band structures of all the systems exhibit half-metallic behaviour with band gaps in minority spin channel from 0.29 eV for Cu3FeTe4 to 1.08 eV for Cu3CrS4, while metallic band structures are observed for majority spins. This agrees with the calculated total magnetic moments which are close to integer values. The calculated negative formation enthalpies indicate the energetic and thermodynamic stability of these compounds. Moreover, the calculated elastic constants verify that these materials are stable mechanically due to satisfying Born stability criteria. The estimated anisotropy shear factors show that Cu3FeS4, Cu3FeSe4 and Cu3CrSe4 systems have nearly isotropic character with 1.004, 0.910, and 0.958 values, respectively, whereas other compounds have relatively low anisotropic behaviour.
关键词： electronic structure of bulk materials,density functional theory,chalcogenides,Half-metallic,mechanical properties of solids
更新于2025-09-23 15:21:21
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Potential Dependence of Mechanical Stability and Electronic Coupling of Single S-Au Bonds
摘要： Providing a mechanically stable and electronically efficient coupling between a molecule and an electrode is critical to the study of charge transfer and conductance of the molecule. A common method is to link the molecule to Au electrodes via a linker (e.g., thiol terminal of the molecule). Here we study the mechanical stability and electronic coupling of S-Au bond in single molecule junctions over a broad range of electrode potential. Our results show that the mechanical and electromechanical properties of molecule-electrode contact undergo a systematic change with the potential involving Au oxidation at positive potentials and S protonation at negative potentials. The study establishes the potential range for a stable S-Au bond and determines the potential dependence of the mechanical and electromechanical properties of the molecule-electrode contact, which is crucial to the interpretation of potential dependent charge transfer in electrochemistry and electrochemical gating of charge transport in molecular electronics.
关键词： molecule-electrode contact,electronic coupling,electrode potential,S-Au bond,mechanical stability
更新于2025-09-23 15:21:21
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Non-Invasive Detection of Mechanical Alternans Utilizing Photoplethysmography
摘要： Background and Significance: Mechanical alternans (MA) is a biomarker associated with mortality and life-threatening arrhythmias in heart failure patients. Despite showing prognostic value, its use is limited by the requirement of measuring continuous blood pressure (BP), which is costly and impractical. Objective: To develop and test, for the first time, non-invasive MA surrogates based on photoplethysmography (PPG). Methods: Continuous BP and PPG were recorded during clinical procedures and tests in 35 patients. MA was induced either by ventricular pacing (Group A, N=19) or exercise (Group B, N=16). MA was categorized as sustained or intermittent if MA episodes were observed in at least 20 or between 12 to 20 consecutive beats, respectively. Eight features characterizing pulse morphology were derived from the PPG and MA surrogates were evaluated. Results: Sustained alternans was observed in 9 patients (47%) from Group A, whereas intermittent alternans was observed in 13 patients (68%) from Group A and in 10 patients (63%) from Group B. The PPG-based MA surrogate showing the highest accuracy, V’M, was based on the maximum of the first derivative of the PPG pulse. It detected both sustained and intermittent MA with 100% sensitivity and 100% specificity in Group A and intermittent MA with 100% sensitivity and 83% specificity in Group B. Furthermore, the magnitudes of MA and its PPG-based surrogate were linearly correlated (R2=0.83, p<0.001). Conclusion: MA can be accurately identified non-invasively through PPG analysis. This may have important clinical implications for risk stratification and remote monitoring.
关键词： Blood pressure (BP),cardiac alternans,photoplethysmography (PPG),hemodynamic instabilities,mechanical alternans (MA)
更新于2025-09-23 15:21:21