Characterization Of Properties Research Articles

Hydrothermal as a synthesis method for characterization of structural, morphological and magnetic properties of Co–Al ferrite nanoparticles

This work provides a set of structural, morphological, and magnetic results for the CoFe2-xAlxO4 (x = 0.00, 0.25, 0.50, 0.75, 1.00 at %) ferrite nanoparticles synthesized by the hydrothermal route. X-ray diffraction analysis (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray Spectroscopy (EDAX), High Resolution Transmission Electron Microscopy (HRTEM), Selected Area Electron Diffraction (SAED) microscopy and Fourier-Transform Infrared Microscopy (FTIR) were used to characterize the structural and morphological features of the prepared magnetic nanoparticles. Rietveld refinement carried out by the Material Analyses Using Diffraction (MAUD) software confirmed the formation of a single-phase spinel structure with no trace of impurity phase. FESEM micrographs showed the appearance of the ferrite nanoparticles with a size distribution in agreement with the data reported by XRD. HRTEM analysis showed the formation of cubic-shaped nanoparticles with dimensions near to the data extracted from XRD. The formation of spinel structure was approved by the FTIR spectra. The magnetic measurements through VSM analysis showed that the incorporation of Al3+ cations into the cobalt ferrite lattices decreases the values of saturation magnetization from about 69 emu/g to near 26 emu/g, which was attributed to the none-magnetic nature of Al3+ cations. The values of the coercive field, on the other hand, indicate a fluctuating trend as a function of Al3+ doping. The coercivity behavior was mainly affected by cation distribution, the variation of anisotropy constant, and the size of crystallites. All the obtained data showed that the magnetic ferrite nanoparticles could be synthesized successfully through the hydrothermal method as a technique that has not been used previously to prepare Co–Al ferrite nanoparticles.

Fungal endophytic species Fusariumannulatum and Fusariumsolani: identification, molecular characterization, and study of plant growth promotion properties

Research on endophytic fungi has gained significant interest due to their potential to enhance plant growth directly by producingphytohormones, solubilizing macronutrients, fixing nitrogen, or indirectly inhibiting phytopathogens growth by producing ammonia, siderophore, hydrogen cyanide, or extracellular enzymes, thereby acting as biocontrol agents. The present study aimed to isolate fungal endophytes from Alternantheraphiloxeroidesand evaluate their plant growth promotion and antimicrobial activity. In total, nine fungal endophytic strains were isolated from different parts of A. philoxeroides such as leaves, roots, and stems. The results demonstrate that the strains MEFAphS1 and MEFAphR3 exhibited positive plant growth promotion properties,including phosphate solubilization, and IAA (Indoleacetic acid) production, and ammonia production. The IAA production was highest for MEFAphS1, with a concentration of 46.635±1.04 µg/mL, while MEFAphR3 displayed the highest ammonia production (0.903±0.01 µg/mL). The phosphate solubilization index (PSI) is the maximum for MEFAphS1 (1.5±0.10). MEFAphS1 also exhibited antibacterial activity against Vibrio vulnificus, Streptococcus pneumoniae, and V.parahaemolyticus,with the most substantial inhibition zone observed against V.vulnificus(28±1 mm). In contrast, MEFAphR3 showed an inhibition zone of 8±1.53 mm against V. parahaemolyticus. Molecular identification revealed the identity of the isolates MEFAphS1 and MEFAphR3 as Fusariumsolaniand F.annulatum. These results thus confirm the possible applications of the fungal endophytes as plant biofertilizers and bio-enhancers to increase crop productivity.

Characterization of nanoscale morphology and mechanical properties of conjugated polymer thin films dynamically exposed to a secondary solvent

Solution processing techniques are often used to enhance intra and interchain order in semiconducting conjugated polymer thin films used in the active layer of organic optoelectronic devices. While there has been extensive research into the impact of solution processing on the local structural and electronic properties of these films, the nanomechanical properties of the films are less well understood and are challenging to characterize. We investigate the nanomechanical properties of conjugated polymer thin films arising from solution processing techniques. Our study relies on dynamic secondary solvent dripping to induce subtle changes to the film morphology. We examine thin films of P3HT, PCDTBT, PTB7, and PBDB-T-SF conjugated polymers, commonly used in organic photovoltaics, with the bimodal amplitude modulation-frequency modulation (AM-FM) imaging mode of the atomic force microscopy (AFM) viscoelastic method to probe their local physical and mechanical properties. We find that Young's Modulus data measured by AM-FM AFM can detect additional changes in film properties not discernible by other commonly used bulk thin-film characterization techniques. For PBDB-T-SF, we detect an increase in molecular order that is not noticable by UV–visible absorption spectroscopy, X-ray diffraction or nanoindentation. PCDTBT, the most amorphous of the polymers studied, shows no changes in absorption or X-ray diffraction data, yet clear changes in Young's Modulus were detected by AFM. On the other hand, increases in P3HT order that occurred due to dynamic secondary solvent dripping are detected in both the bulk and AFM measurements. Our study demonstrates the applicability of nanomechanical measurements for characterizing local structural variations in conjugated polymer films. This work is relevant to ongoing efforts to control and understand the complex structure-property-processing relationships of conjugated polymer thin films.

Material properties in regenerating axolotl limbs using inverse finite element analysis

BackgroundThe extracellular mechanical environment plays an important role in the skeletal development process. Characterization of the material properties of regenerating tissues that recapitulate development, provides insights into the mechanical environment experienced by the cells and the maturation of the matrix. In this study, we estimated the viscoelastic material properties of regenerating forelimbs in the axolotl (Ambystoma mexicanum) at three different regeneration stages: 27 days post-amputation (mid-late bud) and 41 days post-amputation (palette stage), and fully-grown time points. A stress-relaxation indentation test followed by two-term Prony series viscoelastic inverse finite element analysis was used to obtain material parameters. Glycosaminoglycan (GAG) content was estimated using a 1,9- dimethyl methylene blue assay. ResultsThe instantaneous and equilibrium shear moduli significantly increased with regeneration while the short-term stress relaxation time significantly decreased with limb regeneration. The long-term stress relaxation time in the fully-grown time point was significantly lower than 27 and 41 DPA groups. The GAG content was not significantly different between 27 and 41 DPA but the GAG content of cartilage in the fully-grown group was significantly greater than in 27 and 41 DPA. ConclusionsThe mechanical environment of the proliferating cells changes drastically during limb regeneration. Understanding how the tissue's mechanical properties change during limb regeneration is critical for linking molecular-level matrix production of the cells to tissue-level behavior and mechanical signals.

The Impact of Operando Analysis in the Understanding of Oxygen Evolution Reaction Ranging from Intrinsic to Technical Scales

The development of state of the art and cost-effective catalyst materials for the sluggish oxygen evolution reaction (OER) is of paramount importance for realizing practical water electrolysis for green hydrogen production. Crucial for this endeavor is the determination of the OER mechanism and a better understanding of all these background processes that affect catalyst activity and stability. Thus, to further elucidate all these processes operando characterization techniques performed dynamically during OER are used as powerful tools which allow monitoring of key reaction intermediates, active sites, charge transfer and material transformation coupled processes etc. In this work we summarize our recent investigations covering noble and 3d transition metal-based OER electrocatalysts by different operando techniques and we show the importance of such techniques in the unraveling catalyst activation/deactivation mechanisms. Thus, our efforts are ranging from half-cell characterization of electrocatalyst intrinsic properties to single-cell analysis of phenomena occurring during their technical operation.Operando techniques like eQCM, XAS, ICP-OES and single cell testing will be presented aiming to emphasize on the critical role of operando in the understanding of fundamental aspects of electrochemistry [1], like intrinsic catalyst properties (Fig. 1a), the effect of electrolyte impurities such as Fe (Fig. 1b-d) on Ni-based electrocatalysts in alkaline environment [2] as well as mechanistic phenomena taking place during catalyst activation (Fig. 1e-f) leading to the formation of the active sites for OER in acidic environment [3].

(Invited) Formation and Characterization of Fe-Silicide Nanodots for Optoelectronic Application

Light emission from group-IV based nanostructures has been attracting much attention in the field of Si-based photonics because of its potential to combine photonic processing with electronic processing on a single chip [1]. Among various Fe-silicides, semiconducting β-FeSi2 shows light emission in the near-infrared region [2, 3] and is one of promising materials in optoelectronic application from viewpoints of tuning emission energy and improving luminous efficiency by means of quantized structures. In this work, we focus on low temperature formation of β-FeSi2 nanodots (NDs) over ~1011 cm-2 in areal density on SiO2 and the characterization of light emission properties of β–FeSi2 NDs.After conventional wet-chemical cleaning steps of p-type Si(100) substrates, a ~300-nm-thick SiO2 layer was grown at 1000°C in dry O2 and followed by dipping shortly in a dilute HF solution to make uniform surface termination with Si-OH bonds. After that, Fe films in the thickness range from 1.0 to 3.0 nm were formed on the OH-terminate SiO2 layer by electron beam evaporation without any extra heating. And then, the Fe–films were exposed to remote plasma of pure H2 (H2-RP) at 400°C to form highly-dense Fe-NDs [4]. Subsequently, so-prepared Fe-NDs were exposed to pure SiH4 at 400°C while controlling the amount of SiH4 exposure by duration and pressure.AFM images taken after exposure of Fe-films to H2-RP confirm the high-density formation of well-defined NDs. In the cases of H2-RP exposure of 1.3-nm-thick and 3.0-nm-thick Fe-films, the areal dot densities as high as ~1.1 × 1011 and ~1.3 × 1011 cm−2 were obtained, respectively, in which the average dot-heights of self-assembled Fe-NDs were determined to be ~5.3 and ~10.9 nm, respectively, by fitting a log-normal function to each measured size distribution. Notice that AFM images taken after SiH4 exposure show almost no change in the areal dot density while a slight increase in the average dot height. From cross-sectional transmission electron microscope images, we have also verified the formation of distorted-spherical shape NDs with a lattice spacing of ~0.18 nm associated with β-FeSi2. And the result is well consistent with the chemical composition of NDs after SiH4 exposure as evaluated by x-ray photoelectron spectroscopy. In addition, with 976 nm light excitation using a semiconductor laser, the NDs after the SiH4 exposure show stable photoluminescence (PL) signals in the energy region from ~0.7 to ~0.9 eV even at room temperature. On the other hand, no PL signals were detected from the NDs before the SiH4 exposure and after Ar anneal at 400°C. Also, when the size of the Fe-silicide NDs was increased from ~5.3 to ~10.9 nm in average dot height by increasing the initial Fe-film thickness, a distinct red-shift in PL was clearly observed. Thus, the observed PL can be interpreted in terms of radiative recombination of photogenerated carriers through quantized states of β-FeSi2 NDs. These results indicate that SiH4 exposure to Fe-NDs formed on SiO2 is a very promising technique for the low-temperature fabrication of luminescent FeSi2 NDs.AcknowledgementThis work was supported in part by Grant-in-Aid for Scientific Research (A) 21H04559 of MEXT Japan, and the Cooperative Research Project Program of the Research Institute of Electrical Communication, Tohoku University.

New Insights and Strategies for the Efficient Use of Conjugated Porous Polymers in Photoelectrochemical Solar Fuel Production

Solar energy conversion into fuels such as hydrogen through photoelectrochemical (PEC) cells is an attractive way to solve the problems present in the actual energetic system. (1) Despite the advances that have been made in this line, it is still necessary to develop new materials and cell configurations to take this technology to a higher scientific level. The application of organic polymers in PEC is a hot topic that continues to grow due to the promising optoelectronic properties of this class of semiconductors. Conjugated polymers exhibit advanced properties because of it particular conjugation that confers it a huge conductivity through the whole structure. (2) In particular, Conjugate Porous Polymers (CPP) offers a higher photostability and robustness that is fundamental for long term application, but their synthesis often leads to a large-particle powder, unsuitable for preparing thin films, key to preparing high-quality thin films, limiting its applicability in PEC.(3)In this work, we present two innovative strategies that allow the efficient use of these materials in photoelectrochemical cells. The first consists of a synthetic route through mini or ultra-mini emulsion synthesis that provides particles from 500 nm to 20 nm, adequate for thin film preparation. The second consists in the design of suitable monomers to be electropolymerised, obtaining high quality thin films and highly controlled thickness. These strategies allow the complete characterization of the optoelectronic properties of the CPPs, since the thin films obtained are of high quality and stable over time. In this way, several polymers have been prepared and the electronic structure was determined by a combination different techniques such as XPS, electrochemistry and UV-VIS spectroscopy, revealing the suitability to be used as photoelectrodes.The photoelectrochemical properties were analyses by means of linear sweep voltammetry, chronoamperometry, and Photopotential measurements suggesting its potentiality for solar energy conversion. In addition, attending o the conductivity type and electronic properties, both photoelectrodes and tandem cells have been designed by combining them with different materials such as TiO2. The formed hybrid photoelectrodes have been characterized by X-ray diffraction, SEM, EDX and AFM. A series of photoelectrochemical measurements have been performed in a three electrode cell configuration, using the hybrid materials as working electrodes. (4)Hybrid photoelectrodes present improved photovoltages and photocurrents compared to TiO2 and CPP alone, confirming adequate light absorption and charge transfer between them. Besides, Electrochemical Impedance Spectroscopy (EIS) was performed to confirm the improved charge transfer observed when illuminating the hybrid photoelectrodes. Furthermore, the designed tandem cells were connected to a gas chromatograph and the hydrogen evolution was confirmed and quantified. Keywords: Photoelectrochemistry, Solar fuels, Organic materials, Conjugate Porous Polymers, References M. Grätzel, Photoelectrochemical cells. Nature. 414, 338–344 (2001).M. Liras, M. Barawi, V. A. de la P. O’Shea. Chem. Soc. Rev. 48, 5454–5487 (2019).M. Barawi, L. Collado, M. Gomez-Mendoza, F. E. Oropeza, M. Liras, V. A. de la P. O’Shea, C. Adv. Energy Mater. 18, 2101530 (2021).M. Barawi, E. Alfonso-González, C.G. López-Calixto, A. García, A. García-Sánchez, I. J. Villar-García, M. Liras, V.A. de la Peña O'Shea. Small, 18, 37. 2201351 (2022). Acknowledgements This work was supported by the Spanish national project NovaCO2 (PID2020-118593RB-C22) and ERC POC (NanoCPP). M.B thanks the Juan de la Cierva Incorporación grant (IJC2019 – 042430 –I).

Synthesis and Characterization of Optical Properties of Carbon Quantum Dots (CQD) Based on Mustard Green (Brassica juncea L) Leaf with Urea Addition

Carbon quantum dots (CQDs) are a class of fluorescent carbon nanomaterials. Carbon quantum dots (CQDs) were synthesized in this work from Mustard Leaves (Brassica juncea L) with the Addition of Urea via a microwave-assisted reflux method. This research aims to characterize CQDs' optical properties, energy gap, and emission under UV light computationally and experimentally. The studied optical properties obtained the maximum absorption peak observed from the UV-Vis spectrum of CQDs without urea shown at 233 nm. The UV-Vis spectrum of CQDs with the addition of urea (1 g, 1.5 g, and 2 g urea) has maximum absorption peaks at 424 nm, 422 nm, and 418 nm. The addition of urea causes a shift in the peak of the UV-Vis absorption spectrum towards red wavelengths (redshift). CQDs display bright green emissions when exposed to UV irradiation. In this work, the structures of CQDs of various forms (CQD-24, CQD-54, CQD-24-NH2, CQD-54-NH2) are theoretically studied in detail, and the results present both models (CQD-24, CQD-54) shows that the calculation results are in accordance with the experimental results, namely having a maximum UV-Vis absorption at 233 nm and in the range 200-400 nm. The results of calculations based on experiments show the same trend, namely that with the addition of urea, there is a shift in the absorption peak (redshift). The gap energy obtained also decreased with the addition of urea. CQDs solution emits yellow-green light.

Electrochemical Scanning Probe Microscopy Evaluation of Li-Ion Battery Cathode Degradation through in Situ Oxygen Evolution Measurement and Interfacial Property Characterization

Degradation processes involving oxygen evolution significantly limit the performance, reversibility, and capacity of high energy density Li-ion battery (LiB) cathodes. In addition, oxygen evolution processes create hazardous conditions for LiB operation. Despite the importance of these processes, characterization of evolved O2 with sufficient spatial and temporal versatility is hampered by the complex setups required to perform electrochemical mass spectrometry, the gold standard for evaluating this process. Recently, we introduced a scanning electrochemical microscopy (SECM) approach that enables in-situ, real-time (i.e., few ms temporal resolution), chemically selective detection of O2.[1] Measurements were accomplished by positioning an SECM probe (i.e., an Au ultramicroelectrode) near operating cathode surfaces for detecting O2 via the oxygen reduction reaction (ORR). The superior signal-to-noise of this method enabled the observation of two peaks corresponding to a steady-state evolution at high voltage and a transient O2 evolution at low voltage on materials such as lithium cobalt oxide (LCO) and NMC electrodes.Here, we expand the capabilities of our technique by incorporating correlated measurements aimed at understanding how oxygen evolution profiles are related to surface electrochemical and mechanical properties. Specifically, we will focus on the use of feedback-mode SECM and the use of reactive mediators to evaluate the changes in the rates of electron transfer measured on materials undergoing O2 and after structural degradation. Furthermore, the use of electrochemical AFM allows us to measure the mechanical properties of these interfaces, in an attempt to tie the structural changes and the evolution of oxidizing species with the formation of cathode-electrolyte interfaces. Altogether, these multimodal SECM and AFM methods elucidate the manifold chemical, structural, and performance changes underpinning LiB cathode operation.[1] Mishra, A.; Sarbapalli, D.; Hossain, M.S.; Gossage, Z.T.; Li, Z.; Urban, A.; Rodríguez-López, J. Highly Sensitive Detection and Mapping of Incipient and Steady-State Oxygen Evolution from Operating Li-Ion Battery Cathodes via Scanning Electrochemical Microscopy. J. Electrochem. Soc., 2022, 169, 086501. Figure 1

Electrochemical Peroxide Generation for in Situ Disinfection

Among the numerous technological advances sought in order to facilitate human exploration and habitation outside of earth’s atmosphere, solutions and innovations are needed for processing resources locally to support sustainable and long duration space missions. Such in-situ resource utilization (ISRU) is aimed at reducing the payload mass during launch and eliminate the need for ground support for long-term missions and ultimately space colonization. Disinfection needs is an area of particular need, which is currently accomplished through the use of pre-packaged, disposable, wetted disinfection wipes. These items represent an appreciable carry-along mass and disposal/replacement burden requiring ground support. Therefore, a system is desired that could utilize onboard utilities to create disinfecting solutions to eliminate storage/disposable problems of the wetted wipes and further reduce the astronaut’s dependence on earth-based supplies.Faraday Technology Inc. is addressing this challenge by demonstrating an in-situ approach, which utilizes on-board supplies of air and water for on demand electrochemical generation of hydrogen peroxide. Hydrogen peroxide is well-established disinfectant with non-toxic decomposition products (viz., O2 and H2O), that is safe enough for human contact to be sold commercially as a 1-5 w/w% solution, which makes it an ideal disinfecting solution for closed space environments. Faraday has continued to improve the TRL by scaling the electrochemical peroxide generation system from a sub-scale to alpha-scale process in order to deliver 1 L per day of ~2 w/w% hydrogen peroxide for disinfectant applications from DI water feed-stream with air as a feed source[1],[2],[3],[4]. These electrolytes were then sent to NASA for microbial control property characterization.This system eliminates the need to ferry disinfectant wipes to manned space capsules and is a critical enabling technology for future moon-based missions and beyond. Specifically, this talk will discuss the results of these advancements. Acknowledgements: Financial support of NASA Contracts NNX16CA43P, NNX17CJ12C, 80NSSC20C0070, and 80NSSC23CA036 is acknowledged.

Mechanical properties characterization of Ti-6Al-4 V grade 5 (recycled) additively manufactured by selective electron beam melting (EB-PBF)

Additive manufacturing, a rapidly expanding technology, enables the production of intricate parts through the successive layering of materials. However, there remains a dearth of research on the viability of incorporating recycled powder into this process, with the potential to decrease expenses and enhance sustainability. This study's objective is to investigate the ramifications of employing recycled Titanium Ti-6Al-4 V alloy powder, for up to ten cycles, without the addition of virgin powder, in the context of additive manufacturing. The findings reveal that the mechanical properties of the material experience an approximate 40 % degradation in comparison to virgin powder. In ultrasonic very high-cycle fatigue tests (VHCF), the failure stress in the Z direction for additive manufacturing EB-PBF equals or surpasses 245 MPa. This research makes a significant contribution to the sustainable advancement of additive manufacturing, as it demonstrates the potential for recycling Titanium Ti-6Al-4 V grade 5 powder for the production of new items. This not only reduces costs but also serves the environment by circumventing unnecessary material disposal. Consequently, the outcomes of this investigation underscore the promising prospects of additive manufacturing with recycled powder, ushering in fresh opportunities for the industry, especially with regards to sustainability and environmental responsibility.

Intrinsically self-healing ethylene-anisylpropylene copolymer as a candidate material for innovative electrical insulation layers

A novel ethylene-anisylpropylene copolymer was tested as a candidate material for intrinsically self-healing electrical insulation layers. In addition to the thermal and mechanical properties, the dielectric properties were studied before and after induced mechanical and electrical damage to the specimens. The material was tested according to the standards for electrical insulating materials, which require a detailed characterization of the dielectric properties. Nonstandardized tests of self-healing were also included in the testing. The results revealed that the tested material exhibited excellent dielectric parameters and reasonable thermal and mechanical properties. The self-healing tests of the material revealed a 38 % efficiency for recovery of the mechanical properties after the first damage, and this remained almost unchanged after the second and third damage. The first initial results also indicated that the material recovered, to some extent, its electrical insulation properties even after electrical breakdown. By comparing the dielectric strength of the pristine and self-healed specimens, a promising self-healing efficiency of 63 % was determined.

Characterization of the electrical properties of MPS schottky structures incorporating Fe doped polyvinyl chloride (PVC)

This paper explores the effects of the organic interfacial layer on the electrophysical characteristics of Schottky barrier diodes (SBDs). Three types of SBDs were fabricated: Au-Si (referred to as MS), Au/PVC/Si (referred to as MPS1), and Au-/PVC:Fe/Si (referred to as MPS2). Fe nanopowders were subjected to analysis using XRD, SEM, and EDX techniques to investigate their structural and optical characteristics. To investigate the conduction mechanisms of these diodes, I-V characteristics were examined using thermionic-emission (TE), Cheung, and Norde functions. The surface-state density (N ss ) distribution of energy was determined by analyzing the current–voltage (IF-VF) curve under forward bias conditions. This analysis considered the voltage-dependent barrier height (BH) and ideality factor (n(V)). The results demonstrated that the polymeric interlayer without Fe nanoparticles reduced N ss by a factor of 7, while the presence of Fe nanoparticles led to a two-order magnitude decrease, resulting in improved efficiency in comparison with MS structures. The obtained results indicated that including a polymeric layer in MPS structure enhanced their electrophysical features compared to MS diodes, and significantly increased rectification by 15–45 times. In summary, the existence of an organic interfacial layer significantly altered the conduction mechanisms and electrophysical characteristics of MPS diodes. It was found that the addition of Fe nanoparticles in the interlayer resulted in substantial improvements in N ss , efficiency, rectification, and conduction characteristics compared to MS diodes.

Comparative characterisation of structural, physicochemical and digestive properties of rice starches isolated from novel high‐amylose mutants

SummaryNovel high‐amylose rice mutants with unique starch properties were developed from a low‐amylose rice variety. The objective of this study was to explore the impacts of apparent amylose content and amylopectin structure on the physical and nutritional properties of rice starch by comparing novel mutants with conventional rice varieties. The rice mutants demonstrated a specific amylopectin characteristic, indicating an extremely lower portion of short chains (15.2%–16.5%) than the other rice varieties (27.3%–31.1%). The starch gel prepared from the rice mutant exhibited significantly higher compressive and breaking stress than the other high‐amylose rice variety with a higher apparent amylose content, indicating that amylopectin characteristics markedly influenced the starch gel structure. The rice mutant demonstrated the highest content of undigested starch after 120 min of digestion in raw starch (50.5%) and starch gel (53.0%). The starch from newly developed rice mutants were found to have markedly high resistance to digestion due to its amylopectin structure and formation of harder gel.

Dynamic micromechanical measurement of the flexural modulus of micrometre-sized diameter single natural fibres using a vibrating microcantilever technique

Abstract The dynamic response of a structure is a manifestation of its inherent characteristics, including material density, mechanical modulus, thermo- and viscoelastic properties, and geometric properties. Together, these factors influence how the material behaves in dynamic scenarios, dictating its damping properties and behaviour under varying forces. In this study we present a novel approach to accurately determine the flexural (bending) modulus of microscopic diameter natural fibres (flax) using microcantilever vibration analysis. Traditionally, the characterisation of the mechanical properties of fibres has relied on macroscopic methods such as tensile testing, which often results in high scatter in measurement data; furthermore, tensile testing does not accurately represent microscale or dynamic conditions and can be complex in terms of sample preparation and loading. To address this, we have developed a microscale technique involving the fabrication of microcantilevers using flat polypropylene support chips, inspired by microelectromechanical systems approaches. Our method provides a refined method for accurately characterising the mechanical modulus of flax fibres, with reduced data dispersion compared to traditional macroscopic testing. Furthermore, by reducing the influence of inherent fibre defects and maintaining homogeneity along the length of the fibre, our micro-scale technique provides reliable modulus determination. This work opens avenues for improved understanding and application of natural and man-made fibres, such as glass and optical fibres, in a variety of fields.

Characterization of the nonlinear optical properties of Zn and Ag nanoparticles using light at 1550 nm

Nonlinear optical properties of metallic and oxide metallic nanoparticles have been extensively studied as saturable absorbers in fiber-optic lasers in the infrared region for the generation of short and/or ultrashort pulses. In this paper, we report an experimental study of the nonlinear optical response of silver and zinc nanoparticles for continuous-wave illumination at 1550 nm. Nonlinear absorption was investigated using the power-dependent transmission and Z-scan techniques. The results obtained from the first technique showed that the zinc and silver particles behave like saturable absorbers, the modulation depths obtained were 15 % and 32 %, respectively. The Z-scan technique showed the presence of nonlinear refraction and absorption in both samples, the open aperture configuration confirmed the behavior of the materials as saturable absorbers. Additionally, the nonlocality of the nonlinear response was analyzed using a numerical model.

Resonance, Velocity, Dispersion, and Attenuation of Ultrasound-Induced Shear Wave Propagation in Blood Clot In Vitro Models.

Improve the characterization of mechanical properties of blood clots. Parameters derived from shear wave (SW) velocity and SW amplitude spectra were determined for gel phantoms and in vitro blood clots. Homogeneous phantoms and phantoms with gel or blood clot inclusions of different diameters and mechanical properties were analyzed. SW amplitude spectra were used to observe resonant peaks. Parameters derived from those resonant peaks were related to mimicked blood clot properties. Three regions of interest were tested to analyze where resonances occurred the most. For blood experiments, 20 samples from different pigs were analyzed over time during a 110-minute coagulation period using the Young modulus, SW frequency dispersion, and SW attenuation. The mechanical resonance was manifested by an increase in the number of SW spectral peaks as the inclusion diameter was reduced (P < .001). In blood clot inclusions, the Young modulus increased over time during coagulation (P < .001). Descriptive spectral parameters (frequency peak, bandwidth, and distance between resonant peaks) were linearly correlated with clot elasticity values (P < .001) with R2 = .77 for the frequency peak, .60 for the bandwidth, and .48 for the distance between peaks. The SW dispersion and SW attenuation reflecting the viscous behavior of blood clots decreased over time (P < .001), mainly in the early stage of coagulation (first minutes). The confined soft inclusion configuration favored SW mechanical resonances potentially challenging the computation of spectral-based parameters, such as the SW attenuation. The impact of resonances can be reduced by properly selecting the region of interest for data analysis.

A New Laser-Combined H-Type Device Method for Comprehensive Thermoelectrical Properties Characterization of Two-Dimensional Materials.

Two-dimensional nanomaterials have obvious advantages in thermoelectric device development. It is rare to use the same experimental system to accurately measure multiple thermoelectrical parameters of the same sample. Therefore, scholars have developed suspended microdevices, T-type and H-type methods to fulfill the abovementioned requirements. These methods usually require a direct-current voltage signal to detect in Seebeck coefficient measurement. However, the thermoelectric potential generated by the finite temperature difference is very weak and can be easily overwritten by the direct-current voltage, thereby affecting the measurement accuracy. In addition, these methods generally require specific electrodes to measure the thermoelectric potential. We propose a measurement method that combines laser heating with an H-type device. By introducing a temperature difference in two-dimensional materials through laser heating, the thermoelectric potential can be accurately measured. This method does not require specific electrodes to simplify the device structure. The thermoelectrical parameters of supported graphene are successfully measured with this method; the results are in good agreement with the literature. The proposed method is unaffected by material size and characteristics. It has potential application value in the characterization of thermoelectric physical properties.

Characterization of Viscoelastic Properties Considering the Nonrelaxation for Filled Rubber

The influence of nonrelaxation on the Payne effect of carbon black-filled rubber is studied. The prestrain is introduced in the Kraus model in the form of exponential growth. Combined with studies of temperature correlations, an explicit model for predicting the Payne effect at different prestrains and temperatures is developed. Dynamic mechanical analyses are performed to determine model parameters and validate the proposed model. To further verify the proposed model, the heat buildup of rubber columns under dynamic tensile load is tested and simulated. The comparison between simulated and measured data shows that the simulation considering nonrelaxation is more accurate than without considering. With the increase of prestrain, the accuracy of considering nonrelaxation becomes more obvious.

Characterization of functional properties of edible methylcellulose films containing Momordica charantia L. ethanolic extract

Bu çalışmada, Momordica charantia L. etanol ekstraktının (ME) farklı konsantrasyonları (% 0.25, 0.50, 0.75 ve 1) kullanılarak metilselüloz yenilebilir filmler (MC) üretilmiştir. MC filmlerin fizikokimyasal özellikleri ile antimikrobiyal (Bacillus cereus, Escherichia coli ATCC 25922, Staphylococcus aureus 6538 IP, Staphylococcus epidermis ATCC 1228, Vibrio parahemolyticus ATCC 17802, Yersinia pseudotuberculosis ATCC 911, Listeria monocytogenes, Enterococcus faecalis ATCC 29212, Salmonella Typhimurium ATCC 14028, Klebsiella pneumonia, Proteus vulgaris ATCC 13315'e karşı) ve antioksidan aktiviteleri açısından analizleri yapılmıştır. Fourier dönüşümlü kızılötesi (FTIR) spektroskopisi analizi, polimer ve ME arasındaki fonksiyonel grup etkileşimlerini belirlemede kullanılırken, termal gravimetrik analiz (TGA) ve diferansiyel taramalı kalorimetri analizi ise fizikokimyasal karakterizasyonu tanımlamada kullanılmıştır. Kontrol filmlere kıyasla, 24 saat sonunda en yüksek antimikrobiyal etki Proteus vulgaris'e karşı (yaklaşık 1.93 log KOB/mL) %1 ME içeren MC filmlerinde elde edilmiştir. ME konsantrasyonunun artması ile film mukavemeti arasında ters bir ilişki gözlemlenirken, su buharı geçirgenlik değerlerinde önemli bir azalma, temas açısı değerlerinde iyileşme ve hidrofilik özelliklerde belirgin bir artış tespit edilmiştir. Tüm bu sonuçların ışığında, MCME film örnekleri biyolojik olarak parçalanabilir özellikte ve yenilebilir gıda ambalajlama uygulamaları için uygun bileşenler olarak nitelendirilmiştir.