Related Physical Properties Research Articles

Oxidation effects on the optical and electrical properties of MoS2 under controlled baking temperatures

As silicon-based semiconductor technology scales down to the nanoscale, it encounters significant physical limitations, including reduced electron mobility, short-channel effects, and increased heat generation, which hinder device performance and reliability. Two-dimensional (2D) semiconductors, such as molybdenum disulfide (MoS2), offer great potential with superior electrical properties at the nanoscale, but the issue of excessive heat generation in highly integrated circuits persists. Therefore, it is essential to investigate the thermal durability of MoS2 under various heating conditions and its impact on physical properties and device performance. In this study, we systematically investigated the oxidation behavior and related physical property variations of CVD-grown MoS2 monolayers by baking them at different temperatures. It was clearly revealed that high-temperature baking induces p-doping and structural deformation, significantly altering optical and electrical properties. Despite the degradation in device performance, reduced interfacial Coulomb scattering was observed, suggesting potential for improved device stability. This study underscores the importance of understanding thermal stability to accelerate the development of 2D semiconductors for next-generation electronic devices.

Elevation-dependent dynamics of soil properties in a hilly watershed: a landform-based approach.

Understanding the variation of soil physical properties in relation to land use and elevation is essential for modeling soil-landscape relationships and sustainable land management. Hence, this study investigates the spatio-temporal variability of soil physical properties in a lower Himalayan watershed, where agriculture, forest, and grasslands are dominant. Samples from 104 sites in a 422 km2 watershed were collected using a gridded sampling scheme (2km × 2km resolution) over 57weeks. Spatial patterns were analyzed using the Kriging technique, and Spearman rank correlation was employed to identify landform-dependent correlations between soil properties and elevation. The interdependence of the properties was detected using principal component analysis (PCA), while the random forest (RF) approach explored the factors influencing electrical conductivity (EC), organic content (OC), soil temperature (ST), and soil moisture (SM). The results revealed that forest landforms have higher coarser fractions (40%) compared to other landforms, while grasslands have higher soil fines (66%). A positive correlation was observed for elevation with sand content (0.15*), organic content (0.42*), and specific gravity (0.03), while a negative correlation was observed for silt (0.10), clay (0.21*), bulk density (0.52*), electrical conductivity (0.41*), soil moisture (0.28*), and temperature (0.31*). Elevation, soil texture, and specific gravity were identified as critical controls for EC, OC, ST, and SM, emphasizing the importance of soil properties, especially elevation and texture, in shaping spatial distributions. These findings contribute to creating a high-resolution regional inventory for effective land use management, adaptation to climate change, and improved livelihood, specifically for mountain people.

Optimized Drop-Casted Polyaniline Thin Films for High-Sensitivity Electrochemical and Optical pH Sensors

Conducting polymers used in chemical sensors are attractive because of their ability to confer reversible properties controlled by the doping/de-doping process. Polyaniline (PANI) is one of the most prominent materials used due to its ease of synthesis, tailored properties, and higher stability. Here, PANI thin films deposited by the drop-casting method on fluorine-doped tin oxide (FTO) substrates were used in electrochemical and optical sensors for pH measurement. The response of the devices was correlated with the deposition parameters; namely, the volume of deposition solution dropped on the substrate and the concentration of the solution, which was determined by the weight ratio of polymer to solvent. The characterisation of the samples aimed to determine the structure–property relationship of the films and showed that the chemical properties, oxidation states, and protonation level are similar for all samples, as concluded from the cyclic voltammetry and UV–VIS spectroscopic analysis. The sensing performance of the PANI film is correlated with its relative physical properties, thickness, and surface roughness. The highest electrochemical sensitivity obtained was 127.3 ± 6.2 mV/pH, twice the Nernst limit—the highest pH sensitivity reported to our knowledge—from the thicker and rougher sample. The highest optical sensitivity, 0.45 ± 0.05 1/pH, was obtained from a less rough sample, which is desirable as it reduces light scattering and sample oxidation. The results presented demonstrate the importance of understanding the structure–property relationship of materials for optimised sensors and their potential applications where high-sensitivity pH measurement is required.

Geospatial variation of granitic soil erodibility along a hydrothermal gradient in the gully region

Gully erosion poses a severe threat to ecological security and economic sustainability globally. Soil erodibility, characterizing the susceptibility to gully erosion, is influenced by hydrothermal conditions that control pedogenic processes, especially for soils derived from the same parent rock. Soil erodibility characteristics in gully erosional areas have been widely investigated, particularly at a pedon scale. However, limited information is available on the regulation pathway of hydrothermal conditions on gully erosion. Therefore, gully erosion distributed in the granite weathering mantle was selected due to its increased density and sediment yield from north to south across subtropical China. To evaluate the impacts of granitic soil erodibility on the spatial distribution of gully erosion, a comprehensive soil erodibility index (CSEI) was constructed. This index integrated various soil erodibility indicators, including mean weight diameter (MWD), soil structural stability index (SSSI), penetration resistance (PR), soil erodibility factor (K-factor), and others. These soil erodibility indicators with inconsistent spatial variation across the study area showed the highest values at the sandy horizon (F=1.72 ∼ 6.53, p < 0.05), indicating the critical role of this horizon to gully erosion. While a consistent increasing trend with the increase of hydrothermal condition was observed, this spatial variation showed a less significant difference statistically. Moreover, the CSEI (0.12 ∼ 0.91) was mainly determined by cementation (R2 = 0.65 ∼ 0.83, p < 0.01) and hydrophysical properties (LL, PL, w) (R2 = 0.64 ∼ 0.69, p < 0.01), especially soil organic matter and free iron and aluminum oxides (R2 = 0.91). Furthermore, hydrothermal conditions indirectly determined the spatial variation of CSEI by altering soil cementation (SPC=0.51) and physical-related properties (SPC= − 0.15). Collectively, hydrothermal conditions determine gully erosion by altering granitic soil erodibility in subtropic China, and this alteration was triggered by an indirect way. The obtained results would facilitate a better understanding of gully erosion mechanisms and more effective gully control strategies.

Understanding microwave-assisted extraction of phenolic compounds from diverse food waste feedstocks

Microwave-assisted extraction (MAE) of natural antioxidants from food waste (FW) offers an economically appealing waste management strategy. However, MAE from mixed FW has received limited attention. We characterize five single waste streams (apple, coffee, olive, tomato, and potato peel waste) and study MAE of phenolic acids from select feedstocks and mixtures. This library of materials enables us to unravel the relationship of FW composition and physical properties with dielectric properties, heating, and extractive yields. Protein, ash, and moisture contents affect dielectric properties the most. Our study unveils the significance of moisture in free (> 20 wt%) and bound states (< 20 wt%) on FW dielectric properties, heating, and target acid yields (at least 33 % enhancement). Microwaves primarily heat the solvent (dimethylformamide) due to its superior dielectric properties compared to FW (dry and moist, single and mixtures) at ≤ 0.05 solid-to-liquid ratio (g/mL). High moisture content (> 20 wt%) provides higher phenolic yields at lower temperatures (< 100 °C) and shorter times (≤ 10 min) due to enhanced heat and mass transfer by microwaves. Further, our data indicates significant interactions between mixed FW components that drive 2–3x higher yields than those predicted from a simple additive model from single component results. Our work provides new insights for developing versatile MAE strategies to treat mixed FW feedstocks.

Study on the ablation process and failure mechanism of the buffer layer in high-voltage XLPE cable

In recent years, the frequent occurrence of ablation faults in the buffer layers of high-voltage cross-linked polyethylene (XLPE) cables has significantly undermined the stability of power grid operations. However, existing research cannot fully explain the failure mechanism and transformation of related physical and chemical properties of high-voltage cable buffer layer. To address this, the paper have constructed an integrated analysis framework that includes multiphysics field simulations, an equivalent electrical network model, and simulated ablation experiments to comprehensively reveal the complete ablation failure mechanisms. Firstly, this study conducted a comparative analysis of the voltage distribution and temperature changes in the buffer layer using electro-thermal coupling simulations and an equivalent electrical network model. This analysis provides a detailed study of the dynamic development process of buffer layer ablation and identifies key electrical parameters. Subsequently, it verified the accuracy of the simulations through experiments on temperature variation characteristics, changes in hydrogen content, and other gas concentrations by constructing a simulated buffer layer ablation experimental platform. Finally, based on the study of the mechanisms of the buffer layer ablation failure process, this study divided it into three stages: initial electrochemical corrosion, appearance of white powder, and the onset of ablation discharge in the buffer layer. The comparison of experimental results with simulation data from the first two stages further validated the effectiveness and robustness of our analysis framework. In summary, this study provides a comprehensive analysis of the failure process in high-voltage cable buffer layers through simulation and experimental validation. This study provides a methodological basis for preventing cable ablation faults and detecting and evaluating the status of high-voltage XLPE cable buffer layers.

Wenzhou TE: A First-Principle-Calculated Thermoelectric Materials Database.

Since the implementation of the Materials Genome Project by the Obama administration in the United States, the development of various computational materials' databases has fundamentally expanded the choice of industries such as materials and energy. In the field of thermoelectric materials, the thermoelectric figure of merit (ZT) quantifies the performance of the material. From the viewpoint of calculations for vast materials, the ZT values are not easily obtained due to their computational complexity. Here, we show how to build a database of thermoelectric materials based on first-principle calculations for the electronic and heat transport of materials. Firstly, the initial structures are classified according to the values of bandgap and other basic properties using the clustering algorithm K-means in machine learning, and high-throughput first principle calculations are carried out for narrow-bandgap semiconductors which exhibit a potential thermoelectric application. The present framework of calculations mainly includes a deformation potential module, an electrical transport performance module, a mechanical and a thermodynamic properties module. We have also set up a search webpage for the calculated database of thermoelectric materials, providing search facilities and the ability to view the related physical properties of materials. Our work may inspire the construction of more computational databases of first-principle thermoelectric materials and accelerate research progress in the field of thermoelectrics.

Physical, Thermal, and Optical Properties of Mn2+ and Nd3+ Containing Barium Phosphate Glasses.

This work reports on various properties and analysis of optical interactions in phosphate glasses containing red-emitting Mn2+ and near-infrared (NIR)-emitting Nd3+ ions, which are of interest for energy applications and solar spectral converters. The glasses were made by melting with 50P2O5-(48 - x)BaO-2MnO-xNd2O3 (x = 0, 0.5, 1.0, and 2.0 mol %) nominal compositions and characterized by X-ray diffraction, density and related physical properties, differential scanning calorimetry, dilatometry, UV-vis-NIR optical absorption, and photoluminescence spectroscopy with decay kinetics analysis. The glasses were X-ray amorphous, wherein the physical and thermal properties of the Mn2+/Nd3+-codoped glasses were largely impacted by Nd2O3 contents. The optical absorption spectra supported the occurrence of Mn2+ ions and the lack of Mn3+ in the codoped glasses, while the absorption due to Nd3+ ions increased steadily with Nd2O3 contents. Analyzing the glass absorption edges via Tauc and Urbach plots was further pursued for a comparison. The photoluminescence evaluation showed a consistent suppression of the emission from Mn2+ ions with increasing Nd3+ concentration, while the decay kinetics revealed shorter lifetimes in connection with increased Mn2+ → Nd3+ transfer efficiencies. Excitation of Mn2+ at 410 nm, however, led to the Nd3+ NIR emission being most intense for 1.0 mol % Nd2O3, despite the 4F3/2 emission decay analysis showing lifetime shortening throughout. Considering the compromise between red and NIR emissions, the Mn-containing glass doped with 0.5 mol % Nd2O3 is put in perspective with the concept of solar spectral conversion.

SuperCAM CO(3-2) APEX survey at a 6 pc resolution in the Small Magellanic Clouds

The Small Magellanic Cloud (SMC) is an ideal laboratory for studying the properties of star-forming regions thanks to its low metallicity, which has an impact on the molecular gas abundance. However, a small number of molecular gas surveys of the entire galaxy have been carried out in the last few years, limiting the measurements of interstellar medium (ISM) properties in a homogeneous manner. We present the CO($3-2$) APEX survey at a $6$ pc resolution of the bar of the SMC, observed with the SuperCAM receiver attached to the APEX telescope. This high-resolution survey has allowed us to study certain properties of the ISM and to identify CO clouds in the innermost parts of the H$_2$ envelopes. We black adopted the CO analysis in the SMC bar comparing the CO($3-2$) survey with that of the CO($2-1$) of a similar resolution. We studied the CO($3-2$)-to-CO($2-1$) ratio ($R_ $), which is very sensitive to the environment properties (e.g., star-forming regions). We analyzed the correlation of this ratio with observational quantities that trace the star formation such as the local CO emission, the Spitzer color $ $, and the total IR surface brightness measured from the Spitzer and Herschel bands. For the identification of the CO($3-2$) clouds, we used the CPROPS algorithm, which allowed us to measure the physical properties of the clouds. We analyzed the scaling relationships of such physical properties. black We obtained $R_ 0.02$ for the SW bar and a slightly higher ratio 0.1,$ for N66 in the SMC. We found that $R_ $ varies from region to region, depending on the star formation activity. In regions dominated by HII and photo-dissociated regions (e.g., N22, N66) $R_ $ tends to be higher than the median values. Meanwhile, lower values were found toward quiescent clouds. We also found that $R_ black is correlated with the IR color $ $ and the total IR surface brightness. This finding indicates that $R_ $ increases with environmental properties, such as the dust temperature, total gas density, and radiation field. We identified $225$ molecular clouds with sizes of $R &gt; 1.5$ pc and signal-to-noise ratios (S/N) of $&gt; 3$ black of which only $17$ black are well resolved CO($3-2$) clouds black with S/N $ 5$. These $17$ clouds follow consistent scaling relationships to the inner Milky Way clouds but with some departures. For instance, CO($3-2$) tends to be less turbulent and less luminous than the inner Milky Way clouds of similar sizes. Finally, we estimated a median virial-based CO($3-2$)-to-H$_2$ conversion factor of for the total sample.

Utilization of Aluminosilicate Industrial Wastes as Precursors in CO2-Cured Alkali-Activated Precast Concrete Pavement Blocks

This research focuses on the utilization of recently investigated aluminosilicate industrial wastes as precursors to produce non-structural precast alkali-activated concrete pavement blocks. For this purpose, conventional blocks (200 mm × 100 mm × 80 mm) were produced using electric arc furnace slag and municipal solid waste incineration bottom ashes as the sole binders. Portland cement and fly ash blocks were produced as references. The blocks underwent a curing regimen comprising thermal, dry, and carbonation curing stages. Control uncarbonated specimens were subjected to dry curing instead of CO2-based curing to evaluate the influence of carbonation on the blocks’ strength development. The specimens were subsequently examined following EN 1338, which is the European standard for assessing and ensuring the conformity of conventional concrete pavement blocks. The carbonated blocks revealed improved mechanical and physical properties in relation to the uncarbonated ones. All blocks met standard dimensions, showed minimal skid potential (most indicating extremely low potential for slip for reporting unpolished slip resistance values exceeding 75), and had enhanced abrasion resistance due to carbonation, showing 30% and 11% less volume loss due to abrasion for fly ash and bottom ash, respectively. Carbonated blocks performed better than non-carbonated ones, displaying lower water absorption (0.58% and 0.23% less water absorption for bottom ash and slag, respectively) and higher thermal conductivity (20%, 13%, and 8% increase in values for fly ash, slag, and bottom ash, respectively). These results confirm the effectiveness of the accelerated carbonation curing technique in improving the block’s performance. Despite the promising outcomes, further optimization of the alkaline solution and carbonation curing conditions is recommended for future research.

Electrical conductivity upon sintering of pure Cu produced by material extrusion additive manufacturing: Effects of pore, grain size, and impurity

This study investigates the development of pores and microstructures at each processing step and sintering conditions in the material extrusion additive manufacturing process, examining their correlation with related physical properties. This is achieved by fabricating copper parts using material extrusion (MEX) and examining the primary factors that impact the electrical characteristics of the MEX parts. Initially, the application of solvent debinding to MEX-produced Cu parts effectively removes a portion of the binder, forming printing-pattern–induced pores and ineffectual pore channels. Subsequently, thermal debinding eliminates the remaining binder and promotes neck formation between the Cu particles. The process proceeds to a subsequent sintering step, where even after the final sintering, some pores remain. These pores are categorized as sintering-induced and printing-pattern–induced pores. The relatively large pore size due to the printing pattern is identified as the main reason for reduced density of MEX parts, especially those influenced by the contour pattern. As the sintering progresses, the grain size increases, with the overall grain size and shape becoming uniform during extended sintering periods. Impurities, specifically carbon and oxygen, are detected in the sintered part, and their concentrations rise with longer sintering times. After examining the variation in porosity, grain size, and impurity content with respect to sintering time, it becomes evident that porosity plays a pivotal role in influencing electrical conductivity. Consequently, the densest 48 h sintered sample, with a relative density of 95.5 %, achieves the highest electrical conductivity at 94.6 % IACS. This demonstrates that MEX can be effectively employed to craft complex-shaped Cu parts with outstanding electrical properties. In summary, densification is crucial for enhancing the electrical properties of Cu parts produced through MEX, achieved by minimizing printing-pattern–induced pores, the primary contributor to density reduction. This study is poised to advance the manufacturing of high-performance, intricate Cu components by providing insights into the development and locations of primary pores through detailed microstructural investigations.

Exploring the structural stability and related physical properties of FePt2 alloys

The current work presents a theoretical study of the physical properties of several FePt2 ordered structures through first-principles calculations, including structural, magnetic, electronic, mechanical, phonon and thermal properties. The structural stabilities are certified by the enthalpies of formation, elastic constants, and phonon dispersion relationships. The tetragonal I4/mmm structure is energetically favorable compared to other types FePt2 structures including Cmcm, Immm, P63/mmc and P4/nmm structures. The electronic density of states and the contributions of each d-orbital electron to the magnetic moment are analyzed to understand their magnetism. The bulk modulus B values of these FePt2 structures are similar, but the Young's modulus E and shear modulus G as well as the elastic anisotropy are quite different. The thermal properties at finite temperature are estimated by the quasi-harmonic approximation. The I4/mmm structure has higher isothermal bulk modulus, lower thermal expansion coefficient and weaker thermal expansion anisotropy, which is more suitable for high temperature applications than other structures. Also, the sequence of thermal expansion anisotropy is P4/nmm > Immm > Cmcm > I4/mmm (≈P63/mmc).

Pressure-induced magnetic phase transition and related physical properties in Z1-Fe3Pd alloy

A Z1-type Fe3Pd alloy with negative enthalpy of formation at ambient pressure has been discovered recently, however, its physical properties under high pressures remain unclear. In this work, the effect of pressure on the magnetic, electronic, lattice dynamic, mechanical and thermal properties of the Z1-Fe3Pd are investigated thoroughly by the first-principles methods. Under high pressures, the Z1-Fe3Pd are energetically favorable compared to other types Fe3Pd structures. A pressure-induced magnetic phase transition from ferromagnetic (FM) to ferrimagnetic (FIM) state are found, and the FM and FIM states are dynamically and mechanically stable under high pressures. The electronic density of states for both the FM and FIM states are analyzed to understand their magnetism. These two magnetic configurations are ductile, but their elastic properties and anisotropy are quite different. Additionally, the FM and FIM states have high uniaxial magnetocrystalline anisotropy, the FM state is a semi-hard magnet, and the FIM state undergoes a transition from hard magnet to semi-hard magnet with pressure. Finally, the volume and linear thermal expansion coefficients under high pressure are calculated, and the anisotropy of thermal expansion is also discussed in detail.

Production, characterization and performance of green geopolymer modified with industrial by-products

Industrial by-products; have received a lot of attention as a possible precursor for cement and/or concrete production for a more environmentally and economically sound use of raw materials and energy sources. Geopolymer is a potentially useful porous material for OPC binder applications. The use of industrial wastes to produce a greener geopolymer is one area of fascinating research. In this work, geopolymer pastes were developed using alkali liquid as an activator and metakaolin (MK), alumina powder (AP), silica fume (SF), and cement kin dust (CKD) as industrial by-products. Several geopolymer samples have been developed. Research has been carried out on its processing and related physical and mechanical properties through deep microstructure investigation. The samples were cured in water by immersion with relative humidity (95 ± 5%), and at room temperature (~ 19–23 °C) prior to being tested for its workability and durability. The effect of the different composition of precursors on water absorption, density, porosity, and the compressive strength of the prepared geopolymers have been investigated. The results showed that the compressive strength of geopolymers at 28 days of curing is directly proportional to the ratio of the alkali liquid. Ultimately, the best geopolymer paste mixture (GPD1 and GPD2), was confirmed to contain (15% of CKD + 85% MK and Alumina solution (55 wt%)) and (25% of CKD + 75% MK + Alumina solution (55 wt%)) respectively, with 73% desirability for maximum water absorption (~ 44%) and compressive strength (4.9 MPa).

Relationship of Physical Properties and Macronutrient Composition with Carotenoid Profile in Maize Hybrids

Maize hybrids with higher vitreousness contain a higher carotenoid content; however, the relationship between the carotenoid profile and the physical and chemical properties related to vitreousness has not been investigated. The aim of this study was to investigate the relationship among the physical properties (kernel size, hardness, density and bulk density), macronutrient composition (crude protein and fat, starch, amylose, amylopectin and zein) and carotenoid profile (individual, total, α- and β-branch carotenoids and xanthophylls) in the grain of 15 maize hybrids. The tested hybrids displayed high variability for most analyzed traits. Three hybrids were characterized by the predominance of β-branch over α-branch carotenoids, while others showed a more uniform content of both fractions. The kernel hardness was associated with the bulk density, flotation index, kernel sphericity, crude protein and zein content. Hybrids with a higher kernel hardness and associated traits had a higher content of zeaxanthin and other β-branch carotenoids, as well as the total carotenoids. In contrast, lutein and α-branch carotenoids were related to the crude protein and amylopectin content only. The findings of the present study confirmed that kernel hardness is associated with β-branch carotenoids and provided further insight into the relationship between the carotenoid profile and commonly analyzed grain quality properties in maize hybrids. The production of higher quality maize hybrids implies a higher nutritional value of the grain due to the higher carotenoid content.

The Relationship of Physical Properties of Rock to The Slope Stability of The Progo River Cliff in Sentolo-Sedayu, Kulon Progo, Yogyakarta, Indonesia

To support the increasingly advanced development of the Kulon Progo area, road access via the Progo River bridge needs to be maintained in instability. To support this, an engineering geological survey was carried out to find out the relationship between the physical properties of rocks and the stability of slopes on the cliffs of the Progo River. The research method begins with a field survey to obtain lithology and slope geometry data. Scanlines at selected locations were carried out to determine discontinuity areas and interpret rock weathering using a Schmidt hammer. Physical laboratory tests are useful for determining the bulk density and porosity of rocks, while from rock mechanical tests (shear strength) cohesion and friction angle values are obtained. The results of the safety factor analysis using the Slide program show that the slopes generally have a medium-high level of severity (Fk 1.2), supported by quite a lot of joint areas, varying porosity (4.12 – 25.10%) and the level of weathering is at level III-IV. Rock porosity is less related to slope strength, while weathering generally reduces slope stability.

Stepwise reduction of graphene oxide and studies on defect-controlled physical properties

Graphene oxide (GO) is a monolayer of oxidized graphene which is a convenient and potential candidate in a wide range of fields of applications like electronics, photonics, optoelectronics, energy storage, catalysis, chemical sensors, and many others. GO is often composed of various oxygen-containing groups such as hydroxyl, carboxyl, and epoxy. One appealing method for achieving graphene-like behavior with sp2 hybridized carbon is the reduction of GO i.e. formation of reduced graphene oxide (RGO). A stepwise reduction GO to form a family of RGO, containing various quantities of oxygen-related defects was carried out. Herein, the defects related chemical and physical properties of GO and the RGO family were studied and reported in an effort to understand how the properties of RGO vary with the reduction rate. Although there are several reports on various features and applications of GO and RGO but a systematic investigation of the variation of the physical and chemical properties in RGO with the varying quantities of oxygeneous defects is imperative for the engineered physical properties in achieving the desired field of applications. We have attempted to look at the role of sp2 and sp3 carbon fractions, which are present in RGO-based systems, and how they affect the electrical, optoelectronic, and adsorption characteristics.

Adhesion properties of MoS&lt;sub&gt;2&lt;/sub&gt;/SiO&lt;sub&gt;2 &lt;/sub&gt;interface: Size and temperature effects

The interface adhesion properties are crucial for designing and fabricating two-dimensional materials and related nanoelectronic and nanomechanical devices. Although some progress of the interface adhesion properties of two-dimensional materials has been made, the underlying mechanism behind the size and temperature dependence of interface adhesion energy and related physical properties from the perspective of atomistic origin remain unclear. In this work, we investigate the effects of size and temperature on the thermal expansion coefficient and Young’s modulus of MoS&lt;sub&gt;2&lt;/sub&gt; as well as interface adhesion energy of MoS&lt;sub&gt;2&lt;/sub&gt;/SiO&lt;sub&gt;2&lt;/sub&gt; based on the atomic-bond-relaxation approach and continuum medium mechanics. It is found that the thermal expansion coefficient of monolayer MoS&lt;sub&gt;2&lt;/sub&gt; is significantly larger than that of its few-layer and bulk counterparts under the condition of ambient temperature due to size effect and its influence on Debye temperature, whereas the thermal expansion coefficient increases with temperature going up and almost tends to a constant as the temperature approaches the Debye temperature. Moreover, the variations of bond identity induced by size effect and temperature effect will change the mechanical properties of MoS&lt;sub&gt;2&lt;/sub&gt;. When the temperature is fixed, the Young’s modulus of MoS&lt;sub&gt;2&lt;/sub&gt; increases with size decreasing. However, the thermal strain induces the volume expansion, resulting in the Young’s modulus of MoS&lt;sub&gt;2&lt;/sub&gt; decreasing. Furthermore, the size and temperature dependence of lattice strain, mismatch strain of interface, and Young’s modulus will lead the van der Waals interaction energy and elastic strain energy to change, resulting in the change of interface adhesion energy of MoS&lt;sub&gt;2&lt;/sub&gt;/SiO&lt;sub&gt;2&lt;/sub&gt;. Noticeably, the interface adhesion energy of MoS&lt;sub&gt;2&lt;/sub&gt;/SiO&lt;sub&gt;2&lt;/sub&gt; gradually increases with MoS&lt;sub&gt;2&lt;/sub&gt; size decreasing, while the thermal strain induced by temperature causes interface adhesion energy of MoS&lt;sub&gt;2&lt;/sub&gt;/SiO&lt;sub&gt;2&lt;/sub&gt; to decrease with temperature increasing. In addition, we predict the conditions of the interface separation of MoS&lt;sub&gt;2&lt;/sub&gt;/SiO&lt;sub&gt;2&lt;/sub&gt; under different sizes and temperatures. Our results demonstrate that increasing both size and temperature can significantly reduce the interface adhesion energy, which is of great benefit in detaching MoS&lt;sub&gt;2&lt;/sub&gt; film from the substrate. Therefore, the proposed theory not only clarifies the physical mechanism regarding the interface adhesion properties of transition metal dichalcogenides (TMDs) membranes, but also provides an effective way to design TMDs-based nanodevices for desirable applications.

Design and rheological behaviour of lactic acid based cholesteric liquid crystalline materials with hydroquinone unit in the molecular core

In order to contribute to molecular structure – physical property relationship for chiral self-assembling materials, two chiral compounds derived from the lactic acid have been designed. Mesogenic core of materials consists of two benzoate units and one hydroquinone unit connected by the ester linkage groups and two flexible alkyl chains. Different lengths of the chiral alkyl chain were tested, while the length of the achiral alkyl was kept same for all materials. The mesomorphic properties were established by polarizing optical microscopy and differential scanning calorimetry. Both materials possess reasonably broad and stable cholesteric (N*) phase down to room temperature. The rheological characterisation was performed in the N* phase on the compound with shorter chiral alkyl chain using a rotational rheometer in a plate/plate geometry with and without external electric field applied perpendicularly to the flow direction. The results reveal a shear thinning behaviour, even without electric field applied. The N* phase exhibits a slight electrorheological effect, at low shear rates, that continuously decrease with the increase of the shear rate, due to the competition of the flow and electric fields. The mesomorphic behaviour of the designed materials was compared to structurally similar materials. Quite broad temperature range of the N* phase down to room temperature makes studied lactic acid derivatives as suitable chiral dopants for design of new multicomponent mixtures targeted for various applications in photonics and optoelectronics.

Symmetry Properties of Models for Reversible and Irreversible Thermodynamic Processes

The problem of formulating variational models for irreversible processes of media deformation is considered in this paper. For reversible processes, the introduction of variational models actually comes down to defining functionals with a given list of arguments of various tensor dimensions. For irreversible processes, an algorithm based on the principle of stationarity of the functional is incorrect. In this paper, to formulate a variational model of irreversible deformation processes with an expanded range of coupled effects, an approach is developed based on the idea of the introduction of the non-integrable variational forms that clearly separate dissipative processes from reversible deformation processes. The fundamental nature of the properties of symmetry and anti-symmetry of tensors of physical properties in relation to multi-indices characterizing independent arguments of bilinear forms in the variational formulation of models of thermomechanical processes has been established. For reversible processes, physical property tensors must necessarily be symmetric with respect to multi-indices. On the contrary, for irreversible thermomechanical processes, the tensors of physical properties that determine non-integrable variational forms must be antisymmetric with respect to the permutation of multi-indices. As a result, an algorithm for obtaining variational models of dissipative irreversible processes is proposed. This algorithm is based on determining the required number of dissipative channels and adding them to the known model of a reversible process. Dissipation channels are introduced as non-integrable variational forms that are linear in the variations of the arguments. The hydrodynamic models of Darcy, Navier–Stokes, and Brinkman are considered, each of which is determined by a different set of dissipation channels. As another example, a variational model of heat transfer processes is presented. The equations of heat conduction laws are obtained as compatibility equations by excluding the introduced thermal potential from the constitutive equations for temperature and heat flux. The Fourier and Maxwell–Cattaneo equations and the generalized heat conduction laws of Gaer–Krumhansl and Jeffrey are formulated.