Reduction In Thermal Conductivity Research Articles

Effective Utilization of Bio and Industry Wastes to Produce Thermal Insulation Concrete: A Novel Solution for Energy-Saving Buildings

The research addressed the effective and sustainable ways to enhance the thermal insulation properties of concrete without compromising its structural integrity. Traditional methods of enhancing thermal insulation in buildings, such as using thick layers of insulation materials, can be costly and may not always be practical in certain settings. Additionally, the disposal of waste materials such as date palm fiber, shopping plastic bags, and thermocol beads presents an environmental challenge. Therefore, this study aims to investigate the potential use of these waste materials as additives in concrete to improve its thermal insulation properties while also providing a sustainable solution for waste disposal. Date palm fiber is a natural material that is widely available in the Gulf region. Plastic bags are a huge waste from the shops every day, and from the packing materials, this thermocol is a huge waste product. We have to recycle it very efficiently to protect the environment. Three types of special materials, such as thermocol beads (30%), date palm fiber (3%) & shopping plastic bag fiber (3%), were tested in this research. Thermocol beads, when used, reduce their strength and increase the thermal resistance of concrete, while date palm fiber and shopping bag waste fiber, when used, increase the strength of concrete and also increase the thermal resistance of concrete, so it is an excellent reinforcing material and thermal barrier for shopping plastic bags fiber and date palm fiber. Based on this research result, when thermocol beads are used, they prevent heat by 42 percent, while when added with date palm fiber and plastic fiber, they also block heat by an average of 30% percent; thus, all three ingredients are considered excellent thermal insulation material. The reduction in thermal conductivity was attributed to the formation of air voids and the low thermal conductivity of the waste materials. The density of the concrete decreased with the addition of the waste materials. The study suggests that the incorporation of date palm fiber, shopping bag waste fiber, and thermocol beads can be an effective way to enhance the thermal insulation properties of concrete while also providing an environmentally sustainable solution for waste disposal. It will boost green energy technology in the construction industry.

Incorporating TiO2 nanocages into electrospun nanofibrous membrane for efficient and anti-fouling membrane distillation

In this study, TiO2 nanocages with a hollow structure were integrated into the polyvinylidene fluoride co-hexafluoropropylene (PH) spinning solution, leading to the fabrication of a novel PH/TiO2 electrospun nanofiber membrane (PH/TiO2 ENM) through electrostatic spinning. The incorporation of TiO2 nanocages resulted in the formation of abundant micro-nano structures on the PH nanofiber surface, enhancing membrane roughness and hydrophobicity. Additionally, the hollow nanostructure of TiO2 nanocages effectively reduced the thermal conductivity of the ENMs. This reduction in thermal conductivity mitigated the temperature polarization effect, thereby increasing mass transfer driving force for the ENMs. The maximum water flux of the PH/TiO2 ENM reached ∼57.9 L m−2 h−1 (LMH), which was approximately 3.7 times higher than that of the original PH ENM. In addition to the formation of micro-nano structures on PH nanofibers, the presence of TiO2 nanocages facilitated the attachment of more low-surface-energy FAS molecules, improving the resistance of them to fouling and anti-wetting properties against both inorganic and organic contaminants, even in the presence of SDS, in a composite feed solution during the DCMD process. Moreover, even after prolonged exposure to a composite salt solution, this membrane also exhibited exceptional anti-fouling properties and stable desalination performance during a 168 h long-term stability test.

Effect of van der Waals homogeneous interface on lattice thermal conductivity of Janus WSSe bilayer

Vertically stacked 2D materials have provided an unprecedented platform to identify various physical properties and discover novel interfacial emergent phenomena. In this study, the lattice thermal conductivity of Janus WSSe bilayer, involving diverse interfacial stacking configurations, has been clarified by solving the phonon Boltzmann transport equation based on first-principles calculations. The effect of homogeneously stacking on thermal conductivity and potential modulation approaches has also been revealed for Janus WSSe. Our results indicate that the thermal transport in Janus WSSe bilayer can be suppressed by van der Waals interface, and depends on both the stacking patterns and interfacial compositions (S-S, Se-Se and Se-S interfaces). Moreover, the interface effect can be further modulated by an applied vertical pressure. A further reduction in thermal conductivity can be achieved for Janus WSSe bilayer under vertical pressure, implying great potential for efficient thermal management and sensing applications.

Engineering binary-network structured montmorillonite/silica composite aerogels with improved mechanical strength as water-resistant thermal insulators

Developing clay-based aerogel composites with integrated high strength, low thermal conductivity, and hydrophobicity remains a great challenge. Here, binary-network structured montmorillonite/silica composite aerogels (CSACs) with improved mechanical strength were engineered via the in-situ growth of silica networks in the montmorillonite aerogel scaffolds. Tunable density (0.065–0.149 cm3/g) and porosity (92.3–96.2%) can be achieved by different silica sol volumes (silica network content). The filled silica networks endow aerogels with a complete transition from hydrophilicity to hydrophobicity, showing high water contact angles of >130° and extremely low water absorption of 9.9%. CSACs show enhanced stress transfer and load-bearing capacity, with 2.6 and 4.4 times increased compressive modulus and strength compared to pure montmorillonite aerogel scaffolds. Moreover, a noteworthy reduction in thermal conductivity (0.041 to 0.034 W/(m∙K)), the decreased maximum thermal decomposition rates (dw/dt), increased temperature at the maximum decomposition rates (Tmax), and residues confirm the improved thermal insulation and thermal stability of CSACs, respectively. This research provides new insights into the design of efficient thermal insulation materials for diverse energy-saving scenarios that require excellent combined properties.

Effect of Morphological Characteristics of Aggregates on Thermal Properties of Molten Salt Nanofluids

Molten salt-based nanofluid is a thermal storage and heat transfer medium for concentrated solar thermal power plants formed by adding nanoparticles to molten salt, which can enhance the thermal performance of molten salt. However, the nanoparticles tend to aggregate in nanofluids, causing changes in thermal properties. In this work, molecular dynamics simulations were used to study the effect of morphological characteristics of aggregates on the thermal conductivity and specific heat capacity of molten salt-based nanofluids. The results show that the aggregated nanoparticles cause a greater increase in thermal conductivity and specific heat capacity than dispersed nanoparticles. Additionally, the increase in fractal dimension leads to thermal conductivity reduction, while there is no clear correlation between the fractal dimension and specific heat capacity. New insights into the thermal properties of aggregated nanofluids are provided by analyzing the contribution of material components, heat flux fluctuation modes, and energy compositions. It is found that the thermal conductivity of aggregated nanofluids is mainly dominated by the base liquid and collision term. However, the specific heat is not related to the variation in the contribution of different energy compositions. Moreover, compared to the dispersed nanofluid, the increased specific heat capacity of aggregated nanofluids is attributed to the thicker semi-solid layer. This study provides guidance for the design and control of the thermal properties of molten salt-based nanofluids.

Influence of Particle Size on Compressed Earth Blocks Properties and Strategies for Enhanced Performance

In the context of sustainable building development, Compressed Earth Blocks (CEBs) have garnered increasing attention in recent years owing to their minimal environmental and economic impact. However, owing to the inherent diversity of raw soil and the production process’s reliance on expertise, the properties of these blocks are subjected to multifaceted influences. Among these, the significance of soil particle size variation often remains overlooked, leaving its impact ambiguous. This study endeavours to address this gap in existing research by delving into this aspect. Two distinct batches of CEBs were produced by adjusting the grain size curve of a single type of sieved soil with different maximum mesh openings: 2 mm for R1 CEBs and 12.5 mm for R2 CEBs. Experimental results reveal significant differences in thermophysical characteristics: on average, R1 blocks show superior thermal performance, boasting a 23% reduction in thermal conductivity compared to R2 blocks, and are lighter, with an 8% decrease in dry bulk density. Although no significant changes in mechanical parameters were observed, finer-structured R1 blocks showed a 25% greater tendency to absorb water due to changes in their porous structure. This study sheds light on the sensitivity of thermal parameters to changes in soil particle size and shows that blocks with finer particles exhibit poorer heat conduction and heat diffusion. Besides providing new insights into the literature, this research also provides a strategic approach to optimise the thermophysical properties of CEBs. By understanding the influence of particle size, researchers and practitioners can now develop strategies to enhance these properties and improve the overall performance of CEBs.

Numerical simulation and optimization of compact latent heat exchanger with micro-channel plate in shape-stabilized composite phase change material

To enable the rapid provision of domestic hot water, this study presents the independent design of a plate heat exchanger featuring a large heat exchange area and a compact structure. Utilizing a sandwich structure, the thermal storage unit integrates two shaped composite phase change materials (CPCM), namely sodium acetate trihydrate (SAT)/expanded graphite (EG) blocks of identical thickness — in conjunction with a micro-channel heat exchange plate. Multiple thermal storage units are stacked to create the heat exchanger. Experimental validation of the heat transfer performance of this thermal energy storage heat exchanger is conducted, accompanied by the establishment of a heat transfer model elucidating the interaction between the phase change material (PCM) and the fluid. The investigation explores the impact of varying thicknesses of shape-stabilized CPCM, thermo-physical parameters of CPCM, and flow rates on enhancing the thermal efficiency of the thermal energy storage heat exchanger. Results indicate a competitive relationship between the phase change enthalpy and thermal conductivity of CPCM under constant density. Increasing the mass fraction of SAT effectively boosts its heat storage density. However, this improvement is counterbalanced by a reduction in CPCM's thermal conductivity, resulting in diminished heat transfer rates within the material and reduced efficiency in transferring heat between the material and the fluid. Optimal performance is achieved when the mass fraction of sodium acetate trihydrate is 80 wt% and the CPCM thickness is 20 mm. At these parameters, the thermal energy storage heat exchanger exhibits the highest heat transfer efficiency. Furthermore, the heat exchanger is capable of producing 197.86 kg of hot water in 1365 s at an inlet flow rate of 300 L/h, achieving an impressive discharging efficiency of 82.73 %. These findings underscore the feasibility of employing the mini-channel plate thermal energy storage heat exchanger for the rapid preparation of domestic hot water.

Highly tailorable thermomechanical properties of nanograined silicon: Importance of grain size and grain anisotropy

Nanocrystalline silicon can have unique thermal transport and mechanical properties governed by its constituent grain microstructure. Here, we use phonon ray-tracing and molecular dynamics simulations to demonstrate the largely tunable thermomechanical behaviors with varying grain sizes (a0) and aspect ratios (ξ). Our work shows that, by selectively increasing the grain size along the heat transfer direction while keeping the grain area constant, the in-plane lattice thermal conductivity (kx) increases more significantly than the cross-plane lattice thermal conductivity (ky) due to anisotropic phonon–grain boundary scattering. While kx generally increases with increasing ξ, a critical value exists for ξ at which kx reaches its maximum. Beyond this transition point, further increases in ξ result in a decrease in kx due to substantial scattering of low-frequency phonons with anisotropic grain boundaries. Moreover, we observe reductions in the elastic and shear modulus with decreasing grain size, and this lattice softening leads to significant reductions in phonon group velocity and thermal conductivity. By considering both thermal and mechanical size effects, we identify two distinct regimes of thermal transport, in which anisotropic phonon–grain boundary scattering becomes more appreciable at low temperatures and lattice softening becomes more pronounced at high temperatures. Through phonon spectral analysis, we attribute the significant thermal conductivity anisotropy in nanograined silicon to grain boundary scattering of low-frequency phonons and the softening-driven thermal conductivity reduction to Umklapp scattering of high-frequency phonons. These findings offer insights into the manipulation of thermomechanical properties of nanocrystalline silicon via microstructure engineering, carrying profound implications for the development of future nanomaterials.

Multiscale Length Structural Investigation and Thermoelectric Performance of Double-Filled Sr0.2Yb0.2Co4Sb12: An Exceptional Thermal Conductivity Reduction by Filler Segregation to the Grain Boundaries.

Among thermoelectric materials, skutterudites are the most prominent candidates in the mid-temperature range applications. In the multiple-filled Sr0.2Yb0.2Co4Sb12 skutterudite, with Sr and Yb as fillers, we have enhanced the thermoelectric performance of CoSb3 through the reduction of lattice thermal conductivity and the optimization of carrier concentration and electrical conductivity. The high-pressure synthesis of the double-filled derivative promotes filling fraction fluctuation. This is observed by high angular resolution synchrotron X-ray diffraction, showing a phase segregation that corresponds to an inhomogeneous distribution of the filler atoms, located at the 2a positions of the cubic space group Im3̅. In addition, scanning transmission electron microscopy (STEM) combined with EELS spectroscopy clearly shows a segregation of Sr atoms from the surface of the grains, which is compatible with the synchrotron X-ray powder diffraction results. Mean square displacement parameters analysis results in Einstein temperatures of ∼94 and ∼67 K for Sr and Yb, respectively, and a Debye temperature of ∼250 K. The strong effect on resonant and disorder scattering yields a significantly lower lattice thermal conductivity of 2.5 W m-1 K-1 at 773 K. Still, good weighed-mobility values were obtained, with high filling fraction of the Yb and Sr elements. This drives a reduced electrical resistivity of 2.1 × 10-5 Ω m, which leads to a peak zT of 0.26 at 773 K. The analysis and results performed for the synthesized (Sr,Yb)-double filled CoSb3, shed light on skutterudites for potential waste-heat recovery applications.

Thermal conductivity reduction in highly-doped cubic SiC by phonon-defect and phonon-electron scattering

We calculate the thermal conductivity (κ) of highly N- and B-doped cubic silicon carbide (SiC) with defect concentrations (Cdef) from 1016 to 1021 cm−3 and compare the relative importance of the extrinsic phonon-electron and phonon-defect scattering mechanisms. Whereas phonon-electron scattering dominates over phonon-defect scattering at low Cdef up to about 1020 cm−3 at room temperature in N-doped SiC, phonon-defect scattering determines the thermal conductivity reduction in the B-doped case. This strong contrast between the electron- and hole-doped cases is related to the much higher ionization energy of B acceptors as compared to that of N donors, and to the resonant scattering caused by B substitution, not present for the N impurity. The similar features can be found in hexagonal phase 4H–SiC. Our results highlight the importance of considering the phonon-electron scattering mechanism together with other phonon scattering processes when calculating the thermal conductivity of doped semiconductors.

Numerical thermal assessment and theoretical analysis of horizontal-hole interlock composite insulation blocks

In this paper, the thermal performance of 54 horizontal-hole interlocking composite insulation blocks was numerically analyzed based on the steady-state heat transfer model, the regulations were found, and prediction models for the thermal parameters of the blocks were established based on the parallel network thermal resistance model. The influence of block types and block materials on the thermal performance was studied, and it was found that the thermal performance of H-shaped interlocking insulation blocks was better than that of crossed-shaped ones, and the lower the thermal conductivity of block materials, the better the thermal performance of blocks, among which the reduction of thermal conductivity of concrete materials improved the thermal performance of blocks the most. The simulated values of thermal conductivity of H-shaped interlocking insulation blocks and thermal conductivity under the parallel network thermal resistance model were highly linearly correlated with correlation coefficients as high as 0.998 and 0.999. This finding enables the prediction models of thermal parameters of H-shaped interlocking insulation blocks to be established with high accuracy and provides an effective guide for the energy-saving design of interlocking insulation blocks wall.

Effect of feedstock powder size on the microstructure and thermal conductivity of quasi-eutectic LaYbZr2O7 TBCs

The effect of average feedstock powder size on the evolution of microstructure and thermal conductivity are comprehensively analyzed. It was found that the porosity and thermal conductivity of the LaYbZr2O7 coatings were positively correlated with the average powder size. The conventional notion that higher porosity results in lower thermal conductivity is challenged by the above results. The abnormal porosity and thermal conductivity relationship can be ascribed to the density of horizontal cracks which dominates the thermal conductivity reduction. Reducing the average powder size leads to a greater concentration of horizontal cracks and hence reduced thermal conductivity. Moreover, the LaYbZr2O7 coatings not only show significantly lower initial thermal conductivity of under 0.70 W m−1 K−1, but also exhibit stronger sintering resistance in terms of porosity stability and thermal insulation ability compared to the conventional YSZ coatings. The present work affords a new insight in developing advanced thermal barrier coatings with ultralow thermal conductivity.

Substrate-induced asymmetric charge distribution tuning the thermal transport and electronic properties of two-dimensional GaX (X=S and Se)

GaS and GaSe, as members of the III-VI group compounds, have garnered significant attention due to their excellent optoelectronic properties. Recent studies have highlighted the low lattice thermal conductivity (TC) and excellent thermoelectric properties of two-dimensional (2D) GaX (X=S and Se). However, these investigations have focused on free-standing GaX, overlooking the substrate effect. In our study, we conducted first-principles calculations to assess the thermal transport and electronic properties of 2D free-standing and supported GaX (X=S, Se). In terms of thermal transport properties, our findings reveal a significant reduction in the lattice TC of 2D GaS and GaSe when supported on substrates. When supported on the h-BN (0001) substrate, the reductions are 68.01 % and 80.34 %, respectively. Similarly, when supported on the β-Si3N4 (0001) substrate, the lattice TC of 2D GaS and GaSe decreases by 74.60 % and 88.73 %, respectively. The significant decrease in lattice TC is primarily from the asymmetric bonding of GaX induced by the substrates, which enhances phonon anharmonicity and reduces phonon lifetime. In the realm of electronic properties, our investigations reveal that the influence exerted by the h-BN substrate upon the energy band structure of supported GaX is minimal, whereas β-Si3N4 substrate has a greater effect on the energy band structure of the supported GaX due to its high and low undulating atomic surface. Our findings underscore the remarkable tunability of both lattice TC and electronic properties in 2D GaX by selecting different substrates, which holds significant promise for the future applications of 2D GaX in emerging technologies.

Enhanced thermoelectric performance of TiS2 via large thermal conductivity reduction by solid solution alloying with TiSe2

Enhanced thermoelectric performance of TiS2 via large thermal conductivity reduction by solid solution alloying with TiSe2

Realizing an ultralow thermal conductivity via interfacial scattering and rational-electronic band reformation in p-type Mg3Sb2

Eco-friendly Magnesium antimonide (Mg3Sb2) has been extensively investigated as a promising and low-toxic thermoelectric material for intermediate (500–900 K) thermoelectric applications. Herein, p-type Zn-incorporated Mg3Sb2 was prepared by hot press technique, and its thermoelectric transport properties were investigated. The formation of Mg3−xZnxSb2 solid-solution plays a significant role in enhancing electrical conductivity of 34.59 S cm−1 due to the increased carrier concentration and reduced energy gap. Reduction in lattice thermal conductivity of 0.46 W m−1 K−1 at 753 K was obtained for Mg3−xZnxSb2 (x = 0.15) by combined scattering effect of dislocations, lattice strain, and interfaces, which is clearly seen in HR-TEM and strain analysis. These favorable conditions lead to an enhanced thermoelectric figure-of-merit (zT) of 0.25 at 753 K, which is 400% improved compared to the pure Mg3Sb2 sample.

In situ observation of electrical resistivity increase via creep-induced dislocations in n-type PbTe

A decrease in electrical conductivity is measured in situ in n-type PbTe during dislocation-climb creep deformation at 673 K. Transmission electron microscopy reveals the accumulation of high density of immobile dislocations that form stable subgrains which increase in density with increasing strain from 8 to 20%. At a constant applied stress, we conclude the increase in immobile dislocation density is primarily responsible for the continuous increase in the electrical resistivity with strain. With the assumption of constant dislocation velocity at a constant applied stress, the mobile dislocation density is a constant so the increase of immobile dislocation density with strain should dictate the total dislocation density increase during creep deformation. This effect of creep deformation on electrical conductivity, and thermoelectric properties in general, should help design materials and operational conditions to limit such adverse effects on device efficiency while engineering thermal conductivity reductions.

Interfacial thermal conductance of gallium nitride/graphene/diamond heterostructure based on molecular dynamics simulation

<sec>Gallium nitride chips are widely used in high-frequency and high-power devices. However, thermal management is a serious challenge for gallium nitride devices. To improve thermal dissipation of gallium nitride devices, the nonequilibrium molecular dynamics method is employed to investigate the effects of operating temperature, interface size, defect density and defect types on the interfacial thermal conductance of gallium nitride/graphene/diamond heterostructure. Furthermore, the phonon state densities and phonon participation ratios under various conditions are calculated to analyze the interface thermal conduction mechanism.</sec><sec>The results indicate that interfacial thermal conductance increases with temperatures rising, highlighting the inherent self-regulating heat dissipation capabilities of heterogeneous. The interfacial thermal conductance of monolayer graphene structures is increased by 2.1 times as the temperature increases from 100 to 500 K. This is attributed to the overlap factor increasing with temperature rising, which enhances the phonon coupling between interfaces, leading the interfacial thermal conductance to increase.</sec><sec>Additionally, in the study it is found that increasing the number of layers of both gallium nitride and graphene leads the interfacial thermal conductance to decrease. When the number of gallium nitride layers increases from 10 to 26, the interfacial thermal conductance decreases by 75%. The overlap factor diminishing with the layer number increasing is ascribed to the decreased match of phonon vibrations between interfaces, resulting in lower thermal transfer efficiency. Similarly, when the number of graphene layers increases from 1 to 5, the interfacial thermal conductance decreases by 74%. The increase in graphene layers leads the low-frequency phonons to decrease, consequently lowering the interfacial thermal conductance. Moreover, multilayer graphene enhances phonon localization, exacerbates the reduction in interfacial thermal conductance.</sec><sec>It is found that introducing four types of vacancy defects can affect the interfacial thermal conductance. Diamond carbon atom defects lead its interfacial thermal conductance to increase, whereas defects in gallium, nitrogen, and graphene carbon atoms cause their interfacial thermal conductance to decrease. As the defect concentration increases from 0 to 10%, diamond carbon atom defects increase the interfacial thermal conductance by 40% due to defect scattering, which increases the number of low-frequency phonon modes and expands the channels for interfacial heat transfer, thus improving the interfacial thermal conductance. Defects in graphene intensify the degree of graphene phonon localization, consequently leading the interfacial thermal conductance to decrease. Gallium and nitrogen defects both intensify the phonon localization of gallium nitride, impeding phonon transport channels. Moreover, gallium defects induce more severe phonon localization than nitrogen defects, consequently leading to lower interfacial thermal conductance.</sec><sec>This research provides the references for manufacturing highly reliable gallium nitride devices and the widespread use of gallium nitride heterostructures.</sec>

Sustainable utilization of fly ash for phase-change geopolymer mortar reinforced by fibers

The utilization of geopolymer mortar (GPM) made from fly ash (FA) as a sustainable construction material with minimal carbon footprint is a viable option. Incorporating microencapsulated phase change materials (mPCM) into GPM presents a promising solution to reduce the energy consumption of buildings. In this study, phase-change GPM (PC-GPM) was manufactured using FA as the main raw material. The thermal conductivity and latent heat of PC-GPM were improved through addition of mPCM, and the mechanical properties were enhanced through inclusion of basalt fiber (BF) and polypropylene fiber (PF). The mineral components and microstructural characteristics of PC-GPM reinforced by fibers were also investigated. The results indicate that an increase in the mPCM content led to a reduction in the dry density and compressive strength of PC-GPM. The addition of mPCM contributed to an increase in water absorption and a reduction in thermal conductivity. The physical-mechanical properties of PC-GPM were dependent on the content, length and type of fibers. The latent heat of PC-GPM was observed to be approximately 7.7kJ/kg. The formation of sodium-alumina-silicate-hydrate (N-A-S-H) and calcium-alumina-silicate-hydrate (C-A-S-H) gels was found to enhance the mechanical properties of PC-GPM. The PC-GPM sample achieved a maximum compressive strength of 36.86MPa, associated with a thermal conductivity of 1.198W/(m·K) when the mPCM and BF contents were 25% and 0.75%, respectively. The experimental findings can offer valuable contributions to the advancement of environmentally friendly and sustainable phase-change building materials.

Thermoelectric characterization of crystalline nano-patterned silicon membranes.

Research towards efficient and environmentally friendly thermoelectrics proposes silicon nanostructures as possible candidates through reduction of the phononic thermal conductivity. However, there is scarce literature about experimental measurements of the thermoelectric figure-of-merit zT on actual crystalline silicon devices. This article reports on the fabrication and full thermoelectric characterization of crystalline 60 nm thick membranes. To that end, an experiment with four types of built-in devices was designed using a silicon-on-insulator substrate to extract the Seebeck coefficient, electrical conductivity and thermal conductivity. The results show indeed a reduced thermal conductivity of 31 W m-1 K-1 for a 60 nm thick Si membrane and κ = 18 W m-1 K-1 for a porous Si membrane. This reflects an 88% reduction in thermal conductivity compared to the bulk Si material and a 42% reduction compared to plain Si membranes. In terms of power generation, the power factor of the fabricated devices surpasses that of state-of-the-art silicon thin films at room temperature. Notably, a zT figure of merit of 0.04 is reported for a 60 nm thick phonon-engineered Si membrane, which is considerably higher than that of bulk Si(0.001) but lower than previously reported results on other types of nano-objects.

Unexpected reduction in thermal conductivity observed in graphene/h-BN heterostructures.

Heterostructures find wide-ranging applications in fields such as thermal management, thermoelectric energy conversion, and nanoelectronics. This study provides new insights into the thermal conductivity of parallel heterointerfaces by investigating a longitudinal heterostructure composed of graphene and hexagonal boron nitride (h-BN) using molecular dynamics simulations. Interestingly, it is observed that this unique heterostructure possesses a lower thermal conductivity compared to pure h-BN. The analysis reveals that phonon scattering is enhanced by stress at the interface of the heterostructure and the mass distribution through it. The heterostructure model introduced in this study presents new insights for controlling phonon transportation in nanoscale structures.