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This paper brings out an innovation in fabricating porous magnesia‐stabilized zirconia components by infiltrating free‐flowing suspension into polyurethane foam. The process enables the production of samples with different levels of porosity and pore structure by easily controlling the amount of slurry infiltrated into the foam. The process uses Isobam, a nontoxic binder, which makes the fabrication simple and environment‐friendly. Samples with five different levels of total porosity ranging from 41.7% to 62.4% were fabricated. Microstructural studies revealed multimodal pore structure comprising both open and closed porosities. Measurements on thermal properties and compressive strength of the samples showed that the sample with the lowest porosity exhibited a thermal conductivity of 0.495 W/mK and a compressive strength of 45.7 MPa. The measured values of thermal conductivity of the samples with different porosity levels could be described by modified effective medium theory. Present work opens up enormous possibilities for economical industrial production of porous magnesia‐stabilized zirconia components for biomedical and thermal insulation applications. [ABSTRACT FROM AUTHOR]

Although light‐matter interaction and topology of photonic systems have been extensively studied, the topology induced novel light‐matter interaction phenomena in deep‐subwavelength region remain unexplored. Here, based on the non‐trivial topological singularity of 1D photonic crystals (PhCs), novel photonic spin Hall effects and abnormal beam behaviors are revealed in deep‐subwavelength region for the beams with nearly normal incidence, which beyond effective medium theory. The huge photonic spin Hall shift (PSHS) is observed around the singularity in the deep‐subwavelength region. The shape of reflected beam undergoes dramatic changes near the singularity, especially at the singularity, the reflected field is split as dipole‐like distribution for both polarizations. Physically, such a phenomenon is resulted from the destructive interference between the spin‐maintained beam and spin‐flipped beam. Based on these theoretical researches, super‐subwavelength thickness detecting, in which the wavelength is six orders of magnitude larger than the detecting scale, can be designed. Such sensitive detecting can also be applied to dielectric permittivity of PhC and background. Further more, by tuning the distance between two singularities in the deep‐subwavelength region, multi‐frequency channels sensitive detection and broadband platform with huge PSHS can be achieved. This system could be a platform to explore nontrivial light‐mater interaction in deep‐subwavelength region and to design of extremely sensitive detection devices. [ABSTRACT FROM AUTHOR]

In this study, a rapid water content detection method for donkey-hide gelatin was established based on terahertz time-domain spectroscopy in reflection mode. Notably, the effective medium theory, informed by the double-Debye relaxation for free water, was employed to predict the water content in the sample. The water content obtained through effective medium theory was lower than that of the traditional thermogravimetric method due to the existence of bound water. Bound water is invisible in THz spectroscopy due to its slower dynamics. In the frequency range of 0.22–0.48 THz, the offset in measured values between the thermogravimetric method and the THz-based method was fitted by a polynomial function. The results of THz-based method calibrated by polynomial fitting were consistent with the findings of the thermogravimetric method. The water content detection results derived by these two methods demonstrated high correlation values (R2) of 0.9860, 0.9160, and 0.9784, and small root mean square errors (RMSE) of 4.5584, 4.4887, and 5.3657 for three samples, respectively. Moreover, the proposed water content detection method needs to be calibrated only once by the thermogravimetric method. Overall, this study provides a rapid water content detection method and demonstrates the potential of real-time water content detection in donkey-hide gelatin. [ABSTRACT FROM AUTHOR]

The development of bend‐induced effectively single‐mode fiber with a square cross‐section and flat top‐hat intensity distribution is reported using core topology nanostructuring dedicated to femtosecond laser ablation systems. The fiber's core comprises 5419 silica and germanium‐doped silica nanorods with a diameter of 430 nm each arranged into a hexagonal lattice. The distribution of the rods is calculated using in‐house developed code based on the Monte Carlo algorithm to obtain a target shape of mode and intensity distribution. As a proof‐of‐concept, a silica nanostructured fiber with a 24 µm core is developed and verified against the purity of mode guidance, bending, and guiding losses. It is shown that for a wavelength of 1030 nm, the fiber is effectively single‐mode with 96% mode purity when bending with a radius of 20 cm is applied. The fiber has a measured mode area of 360 µm2, numerical aperture of 0.03, and total losses of 0.07 dB m−1. [ABSTRACT FROM AUTHOR]

Since the initial discovery of Dyakonov surface waves at a flat infinite interface of two dielectrics, at least one of which is positively anisotropic, extensive research has been conducted towards their theoretical and experimental studies in materials with positive anisotropy. The potential applications of these waves were initially limited due to the stringent conditions for their existence and the requirement for position anisotropy. In our study, we present the theoretical prediction and experimental observation of a novel type of Dyakonov surface waves that propagate along the flat strip of the interface between two dielectrics with negative anisotropy. We demonstrate that the conditions for surface waves are satisfied for negatively anisotropic dielectrics owing to the specific boundaries of the strip waveguide confined between two metallic plates. We study such modes theoretically by using the perturbation theory in the approximation of weak anisotropy and demonstrate that the electromagnetic field distribution in these modes is chiral. Experimental verification of theoretical predictions is made in the microwave range using 3D-printed negatively anisotropic water-dielectric metamaterial slabs. The existence of Dyakonov surface waves in negative crystals prompts a reassessment of the list of materials suitable for practical realization of these waves in the visible and infrared ranges. Due to the ability of the considered modes to transmit chiral light, they have potential in the sensing of chiral organic molecules. [ABSTRACT FROM AUTHOR]

Surface modified ZnS nanoparticles / poly (methylmethacrylate) - (PMMA) nanocomposites were prepared by the solution casting method. The ZnS nanoparticles, as starting materials in the present study, were synthesized mechanochemically and their crystallite size was estimated as 2.3 nm. Surface modification of obtained nanoparticles was performed by 3-Mercaptopropyltrimethoxysilane. We investigate thin samples of the nanocomposite material and pure PMMA (about 290 μm) with a strong interference effect, and corresponding thick samples, as reference. The optical properties of this material were studied by far-infrared spectroscopy. The analysis of the far-infrared reflectivity spectra was made by the fitting procedure, according to the model for a thin plate of nanocomposites in the air. The dielectric function of the nanocomposites was modeled as a mixture of homogenous surface modified ZnS spherical inclusions in PMMA, by the Maxwell-Garnet formula. In the case of a PMMA thin sample, intense, well-defined interference was registered in the range of 90 to 200 cm− 1, while significantly weaker and less well-defined interference was registered in the range around 450 cm− 1. In the thin composite sample, in addition to the interference induced by sample thickness, interference induced by the existence of ZnS nanoparticles was also observed, located between the TO and LO phonons of ZnS. This opens the possibility of applying nanocomposites in interferometry. [ABSTRACT FROM AUTHOR]

With the advancement of urbanization, super high-rise buildings have become an integral part of modern cities. However, these structures face significant challenges due to thermal expansion effects in complex environments, especially considering the substantial impact of temperature-induced thermal expansion of concrete on the stability and safety of buildings. Although existing research has made some progress in exploring thermal expansion effects and their control strategies, traditional methods have limitations in addressing the complexities of super high-rise buildings. This study first solves the thermal expansion coefficient of concrete in super high-rise building structures based on an effective medium theory, providing a more precise calculation method from a microscopic perspective. Secondly, it proposes and validates a set of thermodynamic control strategies for super high-rise building structures to effectively manage the stress and deformation issues caused by temperature changes. The findings of this study will offer scientific support for the design and maintenance of super high-rise buildings, enhancing their overall safety and economic efficiency. [ABSTRACT FROM AUTHOR]

O-rings made from foam rubber are often used in sealing applications. Foam rubber have low (macroscopic) elastic modulus E 0 resulting in a low nominal contact pressure when squeezed against a countersurface. In most cases the foam rubber is covered by a thin surface film with the effective elastic modulus E 1 > E 0 . We show that the nominal contact pressure may not be high enough for the contact area to percolate and the O-ring seal will leak. For the leakage calculations we use the Persson multiscale contact mechanics theory, and the (modified) Bruggeman effective medium theory for the fluid flow conductivity. The experimental input for the theory are surface roughness power spectrum, which was obtained from stylus topography measurements, and the elastic properties ( E 0 and E 1 ) of the rubber O-ring. As an application of this calculation method, we have used the preliminary as well as the final results of the laboratory gas tightness tests of the 136 New Small Wheel Micromegas Quadruplets performed at CERN, from February 2019 to May 2021, in the framework of the ATLAS Experiment upgrade. In the integration quality control, a novel method for gas tightness measurement, that we have called "Flow Rate Loss", has been used as a baseline method. [ABSTRACT FROM AUTHOR]

This study unveils an advanced methodology for characterizing various types of cow's milk based on their optical properties, aiming to establish a straightforward yet comprehensive method. This study uses fundamental principles such as Snell's Law and Fresnel coefficients to determine and demonstrate critical angles for total internal reflection and reflectance at p polarization. Notably, milk composition, particularly fat content, significantly and remarkably influences its refractive index, with higher fat content leading to elevated values. Additionally, the extinction coefficient, derived through the Beer–Lambert law, provides valuable and essential information regarding light absorption and scattering within the milk samples. The significance of this research relies upon its ability to comprehensively analyze various optical properties of milk, including critical angles, reflectance, and extinction coefficients. By doing so, it offers an exhaustive and detailed understanding of how milk responds to light across different wavelengths and angles of incidence. Moreover, the technique effectively distinguishes milk types based on their fat content and particle characteristics. This novel characterization technique holds promise for various applications within the dairy industry, such as milk quality control, classification, and adulteration detection, which is crucial for maintaining consumer trust and safety. [ABSTRACT FROM AUTHOR]

Abstract The development of bend‐induced effectively single‐mode fiber with a square cross‐section and flat top‐hat intensity distribution is reported using core topology nanostructuring dedicated to femtosecond laser ablation systems. The fiber's core comprises 5419 silica and germanium‐doped silica nanorods with a diameter of 430 nm each arranged into a hexagonal lattice. The distribution of the rods is calculated using in‐house developed code based on the Monte Carlo algorithm to obtain a target shape of mode and intensity distribution. As a proof‐of‐concept, a silica nanostructured fiber with a 24 µm core is developed and verified against the purity of mode guidance, bending, and guiding losses. It is shown that for a wavelength of 1030 nm, the fiber is effectively single‐mode with 96% mode purity when bending with a radius of 20 cm is applied. The fiber has a measured mode area of 360 µm2, numerical aperture of 0.03, and total losses of 0.07 dB m−1.

Directional control of thermal emission over its broad wavelength range is a fundamental challenge. Gradient epsilon-near-zero (ENZ) material supporting Berreman mode has been proposed as a promising approach. However, the bandwidth is still inherently limited due to the availability of ENZ materials covering a broad bandwidth and additional undesired omnidirectional modes in multilayer stacking with increased thickness. Here, we show that broadband directional thermal emission can be realized beyond the previously considered epsilon-near-zero and Berreman mode region. We then establish a universal approach based on effective medium theory to realizing ultra-broadband directional thermal emitter. We numerically demonstrate strong (emissivity >0.8) directional (80 ± 5°) thermal emission covering the entire thermal emission wavelength range (5–30 μm) by using only two materials. This approach offers a new capability for manipulating thermal emission with potential applications in high-efficiency information encryption, energy collection and utilization, thermal camouflaging, and infrared detection. [ABSTRACT FROM AUTHOR]

Polymer thermal conductivities play an important role for their potential use in industrial applications. Therefore, great efforts have been made to investigate fundamental structure–property relationships to understand and predict thermal conductivities for polymers and their composites. The review summarizes selected well-proven microscopic theoretical approaches to calculate thermal conductivities such as EMD, NEMD, EMT, and BTE, and cites examples to focus on different qualitative aspects of recent polymer theoretical research. Examples other than polymer materials are given as supplemental information to support the general discussion of heat transport phenomena in solid materials. [ABSTRACT FROM AUTHOR]

Polymer thermal conductivities play an important role for their potential use in industrial applications. Therefore, great efforts have been made to investigate fundamental structure–property relationships to understand and predict thermal conductivities for polymers and their composites. The review summarizes selected well-proven microscopic theoretical approaches to calculate thermal conductivities such as EMD, NEMD, EMT, and BTE, and cites examples to focus on different qualitative aspects of recent polymer theoretical research. Examples other than polymer materials are given as supplemental information to support the general discussion of heat transport phenomena in solid materials.

The representation of three-dimensional integrated photonic structures in two-dimensional designs has been investigated through finite element analysis using COMSOL Multiphysics. The accuracy of the effective index method for various waveguide designs is studied. An alternative to the effective index method, here named the inverse effective index method, is derived in this paper. The results indicate that the commonly used effective index method has a deviation in propagation constant up to 17%, where the error is largest for low-confinement factor waveguides. The inverse effective index method vastly reduces this error to $< $0.01% for low confinement-factor geometries. This enables an accurate simulation in two-dimensions while retaining the waveguiding properties of the third dimension. As with the effective index method, the inverse effective index method does not require proprietary software.

The development of a flexible and robust metamaterial absorber is a great motivation for the new generation of microwave absorbers covering any conformal shape. Ceramic–polymer composites with variable dielectric constant within the microwave frequencies are proposed as a flexible middle dielectric spacer (MDS) layer to provide an additional degree of design freedom for metamaterial absorber applications. By varying the dielectric constant of the MDS layer, the resonance band of the metamaterial absorber can be tuned while retaining a low profile in addition to enhancing its electromagnetic performance for transverse magnetic (TM) polarized waves. To formulate these composites, tetragonal structured barium titanate (BaTiO3) powder is selected as an excellent candidate when mixed with elastomer polydimethylsiloxane (PDMS), resulting in high mechanical strength substrates. Experimentally, samples with a range of dielectric permittivity from 2.81 to 5.67 were obtained for a 0%–20% volume fill fraction of BaTiO3 in PDMS. The obtained dielectric permittivities are consistent with the Bruggeman effective medium theory. Utilizing an optimized composition (10% BaTiO3), resulting in ϵ r = 4 substrate, an X-band flexible absorber is designed and fabricated to absorb more than 90% of incident electromagnetic waves within a frequency band of 8.16–12.12 GHz. [ABSTRACT FROM AUTHOR]

Particle shape variability is a key to understanding the rich behavior of granular materials. Polyhedra are among the most common particle shapes due to their ubiquitous origins in nature such as rock fragmentation and mineral crystallisation. Because of their faceted shape, polyhedral particles tend to assemble in jammed structures in which face-face and face-edge contacts between particles control the packing-level properties. In this paper, we use tri-periodic particle dynamics simulations to derive for the first time a generic analytical expression of the elastic moduli of polyhedral and spherical particle packings subjected to triaxial compression as a function of two contact network variables: (1) a "constraint number" that accounts for the face-face and edge-face contacts between polyhedra and is reduced to the coordination number in the case of spherical particles, and (2) the contact orientation anisotropy induced by compression. This expression accurately predicts the simulated evolution of elastic moduli during compression, revealing thereby the origins of the higher elastic moduli of polyhedral particle packings. We show that particle shape affects the elastic moduli through its impact on the contact network and the level of nonaffine particle displacements is the same for the simulated shapes. Its nearly constant value during compression underlies the constant values of our model parameters. By connecting the elastic moduli to the contact network through parameters that depend on particle shape, our model makes it possible to extract both the connectivity and anisotropy of granular materials from the knowledge of particle shape and measurements of elastic moduli. [ABSTRACT FROM AUTHOR]

The severe climate and energy issues require more environmentally friendly and efficient cooling methods. Radiative cooling offers a cooling solution with significant advantages. However, current radiative cooling technologies focus primarily on seeking perfect materials to achieve complete wavelength absorption. However, numerous research studies have shown that achieving such a perfect scenario is not feasible. Here, inspired by the surface of the Cerambycini Latreille, the inherent mechanism of radiative cooling functionality in the unique structure of these hairs is revealed using effective medium theory and Finite Difference Time Domain (FDTD) optical simulation analysis. Through alkaline etching and template methods, a biomimetic radiative cooling film (BRCF) was successfully fabricated. The BRCF not only efficiently reflects solar radiation but also enhances absorption in the atmospheric window wavelength range. The radiative cooling mechanism proposed in this study and the BRCF presented here may inspire researchers to further explore the field of structural radiative cooling. [ABSTRACT FROM AUTHOR]

This study unveils an advanced methodology for characterizing various types of cow’s milk based on their optical properties, aiming to establish a straightforward yet comprehensive method. This study uses fundamental principles such as Snell’s Law and Fresnel coefficients to determine and demonstrate critical angles for total internal reflection and reflectance at p polarization. Notably, milk composition, particularly fat content, significantly and remarkably influences its refractive index, with higher fat content leading to elevated values. Additionally, the extinction coefficient, derived through the Beer–Lambert law, provides valuable and essential information regarding light absorption and scattering within the milk samples. The significance of this research relies upon its ability to comprehensively analyze various optical properties of milk, including critical angles, reflectance, and extinction coefficients. By doing so, it offers an exhaustive and detailed understanding of how milk responds to light across different wavelengths and angles of incidence. Moreover, the technique effectively distinguishes milk types based on their fat content and particle characteristics. This novel characterization technique holds promise for various applications within the dairy industry, such as milk quality control, classification, and adulteration detection, which is crucial for maintaining consumer trust and safety.

The severe climate and energy issues require more environmentally friendly and efficient cooling methods. Radiative cooling offers a cooling solution with significant advantages. However, current radiative cooling technologies focus primarily on seeking perfect materials to achieve complete wavelength absorption. However, numerous research studies have shown that achieving such a perfect scenario is not feasible. Here, inspired by the surface of the Cerambycini Latreille, the inherent mechanism of radiative cooling functionality in the unique structure of these hairs is revealed using effective medium theory and Finite Difference Time Domain (FDTD) optical simulation analysis. Through alkaline etching and template methods, a biomimetic radiative cooling film (BRCF) was successfully fabricated. The BRCF not only efficiently reflects solar radiation but also enhances absorption in the atmospheric window wavelength range. The radiative cooling mechanism proposed in this study and the BRCF presented here may inspire researchers to further explore the field of structural radiative cooling.

We employed the p-type semiconductor InTe as an extrinsic phase mixing in the GeTe matrix for thermoelectric properties investigations on the (GeTe) 1-x (InTe) x (x=0, 0.02, 0.04, 0.06, and 0.08) composites. We observed notable phenomena that a small amount of InTe has a significant influence on the thermoelectric properties as the primary host matrix in the (GeTe) 1-x (InTe) x (x=0.02, 0.04, 0.06, and 0.08) composites. Even for small concentrations of InTe which possess lower thermal and electrical conductivities compared to those of GeTe, the thermoelectric properties of the (GeTe) 1-x (InTe) x (x=0.02, 0.04, 0.06, and 0.08) composites are primarily influenced by the properties of InTe. We systematically elucidated the electrical conductivity of the (GeTe) 1-x (InTe) x (x=0.02, 0.04, 0.06, and 0.08) composites through the application of effective medium theory (EMT). It is found that the effective media of the (GeTe) 1-x (InTe) x (x=0.02, 0.04, 0.06, and 0.08) composites is an asymmetric medium insulator. The addition of InTe into GeTe reveals a significant decrease in total thermal conductivity due to reductions in both electronic and lattice thermal conductivity. Particularly, the decrease in lattice thermal conductivity was attributed to an increase in internal strain within the lattice induced by the addition of InTe. Consequently, the ZT values of the composite significantly increase across all temperature ranges. This study suggests that developing composites is an effective approach for enhancing thermoelectric performance, comparable to elemental doping, and demonstrates the ability to analyze the electrical properties of composite materials using EMT. • We synthesized the extrinsic phase mixing composite of (GeTe)1-x(InTe)x. • Small InTe concentration significantly changes thermal and electrical transport properties. • Effective medium theory states that the composite follows an asymmetric medium insulator. • Decrease of lattice and electronic thermal conductivities enhances ZT value over a wide temperature range. [ABSTRACT FROM AUTHOR]

Plasmonic anisotropic nanocomposites containing in particular nanorods and nanowires are gaining increasing interest due to their remarkable physical and optical properties. In this paper, we introduce a novel effective medium theory which we call "Orientation and Shape Distributions Effective Medium Theory" (OSDEMT), to describe the optical properties of a 3D arrangement of metallic nanorods in a dielectric matrix. The effective dielectric properties of plasmonic nanocomposites containing nanorods with different shape and orientation configurations were simulated and analyzed using OSDEMT. We demonstrate that the amplitudes of the longitudinal and transverse surface plasmonic resonances depend on the orientation distribution of the nanostructures, when their positions remain unchanged. Moreover, we show that the anisotropic properties of the nanocomposites are very sensitive to the aspect ratios of the nanorods so that even spherical-centered shape distributions exhibit anisotropic properties when oriented. Finally, we confront the OSDEMT to UV–visible extinction measurements conducted on gold nanorods in a toluene suspension. [ABSTRACT FROM AUTHOR]

With the increasing demand for sensing platforms operating across UV, visible, and near-infrared wavelengths, nanoporous gold has emerged as an ideal substrate for rapid, quantitative detection of analytes with excellent specificity and high sensitivity. This study investigates thickness-mediated compositional changes and their impact on scattering characteristics of thin nanoporous gold films fabricated using selective chemical etching. Specifically, we observe thickness-induced morphological and structural changes across different fabricated samples from 25 to 100 nm in thickness. Upon their optical characterization across UV-VIS-NIR spectral regime, we notice that the constitutional differences among samples manifest distinctively & deterministically in their total optical scattering response. In order to gain insights into these observed scattering responses and to fathom the subtle connections between structural properties of NPG films and their optical response, a hybrid theoretical model comprising Maxwell-Garnett & Bruggeman effective medium approximations has been adopted. Our approach not only allows to appropriately account for the inhomogeneous nature of these films, but also corroborates well with the atomic force microscopy characterizations of the fabricated samples. Furthermore, tracing such a theoretical model is important as it helps in systematically ascertaining additional loss terms emerging in the complex dielectric function of films due to their nanoscale porosity & roughness, permitting a good reproduction of measured optical spectra. We believe, our approach will not only facilitate accurate regulation of losses in NPG thin films but will also aid in deriving customized optical performance from them, thereby advancing their potential applications in sensing and beyond., (© 2024 IOP Publishing Ltd.)

Understanding the stress-dependent elastic moduli of fractured rocks is essential for monitoring geopressure and tectonic stress. The elastic nonlinearity with finite strains can be described by the theory of acoustoelasticity through the third-order elastic constants (3oECs) that are strictly valid for an isotropic homogeneous medium. The extension to fractured rocks becomes particularly interesting because of the sensitivity of fractures to prestress, but remains largely unaddressed. We address this issue through theoretical modeling with confirmed validity by considering a group of homogeneously distributed fractures (ellipses) embedded into a homogeneous background medium subject to a uniform confining pressure. We incorporate both the David-Zimmerman (DZ) and Mori-Tanaka (MT) models into the theory of acoustoelasticity. The DZ model accounts for the closure influence of cracks with different aspect ratios, whereas the MT model is used to estimate the combining effect of the background acoustoelasticity and the elastic nonlinearity due to the closure of cracks. We validate the acoustoelastic DZ-MT model of fractured rocks by experiment data with Fontainebleau and Vosges sandstones. We show that the effective elastic moduli of fractured rocks mainly depend on the background acoustoelasticity and nonlinear elastic deformations induced by closing cracks. The inclusions inside fractures have too low 3oECs that the associated acoustoelastic effect could be neglected for both interconnected and isolated cracks. The effective elastic moduli of rocks change significantly during the closing period of cracks with increasing pressure under low pressure. The influence of cracks can be reduced only when cracks are closed completely, where, unlike the theoretical prediction by the DZ model, the effective elastic moduli of rocks still increase along with increasing pressure because of the acoustoelastic effect of the background. [ABSTRACT FROM AUTHOR]

• The influence of surface functional groups with varying grafting ratios on the interfacial thermal conductivities between h-BN and epoxy was studied by MD simulation. • KH550 showed better interfacial thermal enhancement than dopamine and hydroxyl. • The thermal conductivities of h-BN/epoxy composites were investigated via effective medium theory and experimental verification. Electronic equipment generates a significant amount of heat during operation with the trend of integrated circuit chips and electronic components towards miniaturization and multi-functionality. Consequently, guaranteeing safe and dependable functioning while appropriately dispersing heat has become a critical challenge in the development of the microelectronics sector. The emergence of thermal interface materials (TIMs) with high thermal conductivity can effectively address this issue. In this study, simulations and experiments were used to investigate the effects of functional groups, including hydroxyl (-OH), dopamine (DA) and silane coupling agent (KH550), and their grafting ratios on the thermal conductivity of hexagonal boron nitride/epoxy (h-BN/EP) composites. The interface thermal conduction results demonstrated that the modification of functional groups with a higher grafting ratio exhibited a larger enhancement, and KH550 outperformed DA and -OH in terms of the enhancing effect. Moreover, according to the effective medium theory (EMT), the simulated thermal conductivity of BN-KH550/EP composite (2 % grafting ratio of KH550, 10 vol% filling ratio of BN) was 0.692 W·m−1·K−1, 224.9% higher than that of pure epoxy resin. Additionally, the experimentally measured thermal conductivity was 0.703 W·m−1·K−1, showing good agreement with the simulation result and indicating EMT's accurate prediction for the h-BN/EP composites. [ABSTRACT FROM AUTHOR]

The incorporation of carbon fillers into geopolymers enhances conductivity, forming intricate networks for integrated energy conversion in construction materials. This study employs a novel computational modeling approach to investigate the electrical conductivity of geopolymer-graphite composites. Utilizing a particle-based Monte Carlo method, percolation thresholds in virtual composite mesostructures are simulated, and Bruggeman's effective medium model is applied to predict conductivity. The research explores how mesostructural characteristics, including pore and particle size distribution, influence percolation and conductivity in multi-phase mixtures. The findings indicate that graphite polydispersity increases the percolation threshold from 10 vol% to 24.4 vol%, while the introduction of two additional (segregated) phases, metakaolin and pores, decreases the percolation threshold to 11.9 vol%. The concept of effective volume fraction is introduced to assess the influence of metakaolin and porosity on the percolation threshold. This enabled to establish a linear relationship between the electrical conductivity and effective volume fraction of graphite with a slope of 2 S/m/vol%. In a three-phase mixture, the percolation threshold is 12.18 vol%, with a 2.35% increase due to capillary water drying, enhancing graphite particle aggregation in the dried pores. Finally, Bruggeman's analytical effective medium model is used to simulate conductivity variation with increasing graphite content, aligning well with conductivity measurements. These findings provide valuable insights into percolation behavior and offer a relatively simple quantitative modeling approach to understand the factors influencing the effective conductivity of geopolymer-graphite composites. [Display omitted] • Multi-phase particle-based computation for percolation and conductivity model. • Segregated phases metakaolin and pores decreased percolation by factor 0.49. • Model using effective graphite fraction in agreement with measured conductivity. • Conductivity transition reveals two-stage threshold with a second slope of 2 S/m/v%. [ABSTRACT FROM AUTHOR]

• Determined experimental effective diffusion coefficients (D eff) under HILIC conditions. • Applied Effective Medium Theory to derive intra-particle diffusion (D part) from D eff. • Analyzed mesopore composition as a function of mobile phase composition. • D part / D m reaches minimum when stationary phase layer thickness is largest. • Proposed model linking mesopore composition, analyte retention and size to D part. A detailed analysis of intra-particle volumes and layer thicknesses and their effect on the diffusion of solutes in hydrophilic interaction liquid chromatography (HILIC) was made. Pycnometric measurements and the retention volume of deuterated mobile phase constituents (water and acetonitrile) were used to estimate the void volume inside the column, including not only the volume of the mobile phase but also part of the enriched water solvent acting as the stationary phase in HILIC. The mobile phase (hold-up) volume accessible to non-retained components was estimated using a homologous series approach. The joint analysis of the different approaches indicated the formation of enriched water layers on the hydrophobic silica mesopore walls with a thickness varying significantly with mobile phase composition. The maximal thickness of the enriched water layers, which corresponded to the minimum void volume accessible to unretained solutes, marked a transition in the retention behavior of the studied analytes. Discrepancies between deuterated solvent measurements and pycnometry were explained by the existence of an irreplaceable water layer adsorbed on the silica surface. Regarding the diffusion behavior in HILIC, peak parking experiments were used to interpret the influence of the acetonitrile content on the effective diffusion coefficient D eff. A systematic decrease in D eff and molecular diffusion D m was observed with decreasing acetonitrile concentration, primarily attributed to variations in mobile phase viscosity. Notably, D eff / D m remained nearly unaffected by variations in mobile phase composition. Finally, the effective medium theory was used to make a comprehensive analysis of D part / D m to study the contribution to band broadening when the solute resides in the mesopores. The obtained data unveiled a curvature with a minimum corresponding to conditions of maximum water-layer thickness and retention. For the weakly retained compounds (k ' < 0.5) the D part / D m -values were found to be relatively high (order of 0.35-0.5), which directly reflects the high γ s D s / D m -values that were observed (order 0.35-7). [ABSTRACT FROM AUTHOR]

Accurate measurements of the thermal conductivity ( κ ) of porous thin films are still limited due to challenges to deposit flat and continuous metal transducers on porous samples, a necessity for many thermal measurement techniques for nanostructures. In this paper, we introduce an approach based on time-domain thermoreflectance (TDTR) to accurately and conveniently measure κ of porous thin films by transferring a flat and smooth metal film unto porous samples as the transducer for TDTR measurements. We demonstrate our approach by measuring κ of a series of microscale holey SiO 2 films with diameters of 1-3.5 μm and porosity of 13-50%. To achieve a measurement uncertainty of <12%, we ensure that the metal transducer films are sufficiently stiff and establish good thermal contact with the holey SiO 2 samples. Our κ measurements agree well with calculations of κ from effective medium theory. Our approach could provide a convenient way to further investigate the thermal transport properties of porous films.