Phonons in low-dimensional structures with feature sizes on the order of the phonon wavelength may be coherently scattered by the boundary. This may give rise to a new regime of heat conduction, ...which can impact thermal energy transport and conversion. Traditional methods used to investigate phonon transport in one-dimensional structures suffer from uncertainty due to contact resistance, defects, and limited control over sample dimensions. We have developed a new batch-fabrication technique for suspended microdevices with integrated silicon nanowires from silicon-on-insulator (SOI) wafers. The nanowires are defect-free and have extremely high aspect ratios (length/critical dimension >2000). The nanowire dimensions (length and critical dimension) can be precisely controlled during fabrication. With these novel devices, phonon transport in silicon nanowires is systematically investigated. The room temperature thermal conductivity of nanowires with critical width around 80 nm is about 20 W/(m K) and much lower than that in smooth VLS wires. This suggests that the surface morphology of the structures has a significant effect on the thermal conductivity, but this phenomenon is not currently understood. This fabrication technique can also be used for thermal transport investigation in a wide-range of low-dimensional structures.
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IJS, KILJ, NUK, PNG, UL, UM
The reduction in harmful destruction of ecosystem and to produce low cost polymeric reinforced composites, the researchers are emerging with policies of manufacturing the composites using natural ...fibres which are entirely biodegradable. These policies had generated safe strategies to protect our environment. The utilization of bamboo fibres as reinforcement in composite materials has increased tremendously and has undergone high-tech revolution in recent years as a response to the increasing demand for developing biodegradable, sustainable, and recyclable materials. The amalgamation of matrix and natural fibres yield composite possessing best properties of each component. Various matrices used currently are soft and flexible in comparison to natural fibres their combination leads to composite formation with high strength-to-weight ratios. The rapid advancement of the technology for making industry products contributes consumer the ease of making a suitable choice and own desirable tastes. Researchers have expanded their expertise in the product design by applying the usage of raw materials like bamboo fibre which is stronger as well as can be utilized in generating high end quality sustainable industrial products. Thereby, this article gives critical review of the most recent developments of bamboo fibre based reinforced composites and the summary of main results presented in literature, focusing on the processing methodology and ultimate properties of bamboo fibres with polymeric matrices and applications in well designed economical products.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This work aims to investigate the thermal comfort behaviour of polyester seamed fabric regarding the change in sewing thread filaments fineness for two different seam classes: seam 514 and seam 607. ...Five seamed fabric samples were constructed with using micro-denier polyester filament of 16.66 tex made of five different filament numbers (38, 48, 108, 144 and 288). It was noticed that the seam thermal properties, air and water vapour permeability, and wicking can be improved if the seam is constructed with using the micro-denier polyester sewing thread. It was also found that the investigated properties increase with the increase in the sewing thread filament fineness on the seam line. The statistical results have also shown that the sewing thread filament fineness is significantly affecting thermal behaviour of the seamed fabric. Keywords: clothing comfort; seams and stitches; thermal behaviour of seams; sewing thread; micro-denier filaments. Cilj ovog rada je ispitivanje svojstava toplotnog komfora poliestarske pletenine sa šavovima izradenim od poliestarskih šivacih konaca razlicite finoce filamenata. Primenjene su dve vrste iz dve razlicite klase šavova - 514 i 607. Konci za šivenje iste finoce 16,66 tex izradeni su od razlicitog broja teksturiranih poliestarskih filamenata (38, 48, 108, 144 and 288). Na taj nacin, eksperimentalni materijal je obuhvatio ukupno 10 razlicitih uzoraka sa šavovima svrstanim u pet grupa (razlicita finoca filamenata) sa po dve vrste šava. Uoceno je da se termicka svojstva, propustljivost vazduha i vodene pare, i kapilarno kvašenje šava mogu poboljšati upotrebom poliestarskog šivaceg konca izradenog od finijih (mikro) filamenata. Takode, utvrdeno je da se sa povecanjem finoce filamenata šivaceg konca povecava propustljivost vazduha i vodene pare, kapilarno kvašenje i sposobnost prenosa toplote na liniji šava. Uticaj finoce filamenata šivaceg konca na toplotni komfor šavova potvrden je statistickom analizom. Kljucne reci: udobnost odece; šavovi i ubodi; termicko ponašanje šavova; konac za šivenje; mikro-dener filamenti
The heat accumulation has become a serious problem due to electronic devices towards high power and intelligence. Highly thermal conductive and electrical insulating polymeric composites are ...potential to solving the overheating problem of electronic devices. Herein, boron nitride nanosheets (BNNSs) were successfully exfoliated by shear forces generated high pressure. Then, BNNSs and sphere BN (S-BN) were added into the polydimethylsiloxane (PDMS) matrix to prepare composites. The thermal conductivity of the BNNSs/PDMS composites achieved 1.16 W m-1 K-1 at 35 wt% fillers, which is almost 5 times that of pure PDMS and higher than that of S-BN/PDMS composites. The efficient thermal paths were constructed by BNNSs in PDMS matrix leading to enhancing the thermal transport in polymer matrix. Meanwhile, the volume resistances and breakdown strength of BNNSs/PDMS composites reach 7.5 × 1013 Ω cm and 39.8 V/μm, which are attributed to the superior electrical insulating properties of BNNSs. The result shows that the excellent thermal conductivity and electrical insulation properties of BNNSs/PDMS make it a promising application in the field of thermal management.
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•BNNS filler was a good choice for improving highly thermal conductivity and electrical insulating of PDMS composites..
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Comprehensive review on integrating waste materials in pre-foamed concrete.•Utilization of different types of waste as cement and aggregate substitute.•Effect of various types of waste materials on ...properties of foamed concrete.•Foamed concrete is a promising avenue to incorporate waste materials for sustainability.
Several million tons of different types of wastes are generated every year globally and this is expected to increase in the future. Most of these wastes are dumped via landfilling or incineration which creates environmental concerns. One of the possible methods of utilizing these wastes is by incorporating them as alternatives to common concrete constituents. In this regard, foamed concrete could provide an excellent medium for incorporating these wastes in a large volume primarily due to low strength requirement of foamed concrete. A significant number of research is carried out to explore the idea of integrating waste materials in pre-foamed concrete. However, the limited knowledge available to recognize the utilization of these waste and the influence on foamed concrete limits the adoption of the concept and further development. Hence, this paper compiles and reviews the usage of various types of wastes such as industrial, agricultural, quarry, and construction industry wastes as a potential replacement for cement and fine aggregate in foamed concrete. Due to the unique composition and the resulting chemical and physical properties, as well as the nature of replacement (either as cement or fine aggregate replacement), each type of waste contributes differently to the performance of foamed concrete. Generally, a non-load bearing foamed concrete with low thermal conductivity, low density, and adequate compressive strength can be produced by incorporating the waste materials. This paper also describes the advantages of incorporating waste materials in foamed concrete compared to conventional concrete and proposes the further development of the concept for future application of a more sustainable and eco-friendly foamed concrete.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The 8-hydroxyquinolinium 3,5-dinitrobenzoate crystals were grown using slow evaporation solution technique. The structure was confirmed by single crystal X-ray diffraction and nuclear magnetic ...resonance analyses. The Fourier transform infrared and Raman spectral analyses were carried out to identify the various functional groups present in the title crystal. The optical properties were investigated by means of ultraviolet–visible spectroscopy and Kurtz–Perry powder method. Thermal properties were characterized by thermogravimetry, differential thermal analysis and differential scanning calorimetry. The mechanical strength of the crystal was investigated by Vickers microhardness tester. Additionally, first-order hyperpolarizability, nuclear magnetic resonance, molecular orbitals, electronic excitation and electrostatic potential were calculated theoretically by density functional theory using Gaussian 03 program package.
•Single crystal XRD and NMR studies confirm the formation of the title compound.•SHG efficiency was found to be two times greater than that of urea.•First-order hyperpolarizability (β) was found to be 5.05630×10−30esu.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The thermal properties of Sn.sub.2P.sub.2S.sub.6 single crystals doped with Ge, Te, and Sb have been studied in the neighborhood of the ferroelectric to paraelectric second-order phase transition by ...means of ac photopyroelectric calorimetry, measuring thermal diffusivity. A detailed study of the critical behavior of the transitions has been undertaken using different theoretical models to study the influence of the dopants and the physical mechanisms activated. Ge strongly favors the stereoactivity of the material, which is revealed in the increase of the critical temperature and the sharpening of the transition; this is due to the strengthening of the sp.sup.2 electronic orbitals hybridization. Sb has a small influence on the stereoactivity while Te virtually none. In all cases, the ferroelectric phases are well described using the phenomenological Landau model, while for the paraelectric ones, a combination of two mechanisms is needed: first-order fluctuations of the order parameter plus the presence of charged defects, ruling out other possible mechanisms. The relative importance of the presence of these defects increases with increasing contents of Ge and Sb, while in the case of Te, there is only a slight increase with respect to the undoped sample.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The surfactants of sodium dodecylbenzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS) are used in multi-walled carbon nanotubes (MWCNT) aqueous solution respectively due to the hydrophobic ...nature of MWCNT. Thermal conductivities of nanofluid solutions are measured via the LAMBDA measuring system by transient hot wire method and compared as function of dispersing two different surfactants. MWCNT (hereinafter sometime referred to as CNTs) nanofluid gets a good dispersion and long time stability with both surfactants within 3/1 relative ratio mixture. However, the thermal conductivity of nanofluid decreases with increasing the concentration of both surfactants, and CNT nanofluid with SDBS exhibits better thermal conductivity than that with SDS dispersant. Finally the proper mixture ratio of CNT nanofluid with SDBS and pH value is examined and results show that 0.5wt.% CNT nanofluids with 0.25wt.% SDBS, at pH≈9.0 condition display the best thermal performance which increases by 2.8% totally on thermal conductivity compared with that of base fluid distilled water (DW).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This study adopts an alumina (Al2O3) and titania (TiO2) nano-coolant (NC) to enhance the heat dissipation performance of an air-cooled radiator. The two-step synthesis method is used to produce ...different concentrations of Al2O3 and TiO2/water (W) nanofluid by using a 0.2 wt.% chitosan dispersant, and the nanofluid is mixed with ethylene glycol (EG) at a 1:1 volume ratio to form NC1 to NC6. The experiments were conducted to measure the thermal conductivity, viscosity, and specific heat of the NC with different concentrations of nanoparticles and sample temperatures, and then the NC was used in an air-cooled radiator to evaluate its heat dissipation capacity, pressure drop, and pumping power under different volumetric flow rates and heating temperatures. Finally, this study evaluates the relationship of the heat dissipation capacity and pumping power by using the efficiency factor (EF). The experimental results show that the heat dissipation capacity and the EF of the NC are higher than EG/W, and that the TiO2 NC is higher than the Al2O3 NC according to most of the experimental data. The maximum enhanced ratios of the heat dissipation capacity, pressure drop, pumping power, and EF for all the experimental parameters are approximately 25.6%, 6.1%, 2.5%, and 27.2%, respectively, compared with EG/W. Overall, the NC improves the heat dissipation capacity and EF of the cooling system; however, the enhanced ratio of the pressure drop and pumping power is not obvious in this study.
•We employed oxide nano-coolant (NC) in air-cooled radiator for heat dissipation.•We produced the Al2O3 and TiO2 NC by the two-step synthesis method.•The heat dissipation capacity and the EF of the NC are higher than EG/W.•The enhanced ratio of the pressure drop and pumping power is not obvious.•The maximum enhanced ratios of EF for TiO2-NC6 was 27.2% compared with EG/W.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Conductive elastic composites have been used widely in soft electronics and soft robotics. These composites are typically a mixture of conductive fillers within elastomeric substrates. They can sense ...strain via changes in resistance resulting from separation of the fillers during elongation. Thus, most elastic composites exhibit a negative piezoconductive effect, i.e. the conductivity decreases under tensile strain. This property is undesirable for stretchable conductors since such composites may become less conductive during deformation. Here, we report a liquid metal-filled magnetorheological elastomer comprising a hybrid of fillers of liquid metal microdroplets and metallic magnetic microparticles. The composite's resistivity reaches a maximum value in the relaxed state and drops drastically under any deformation, indicating that the composite exhibits an unconventional positive piezoconductive effect. We further investigate the magnetic field-responsive thermal properties of the composite and demonstrate several proof-of-concept applications. This composite has prospective applications in sensors, stretchable conductors, and responsive thermal interfaces.
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