Hot Disk Method Research Articles

Fired and unfired clay bricks incorporating olive pomace: A comparative study

This work presents a comparative study on clay bricks made with a local soil (Midar, eastern Morocco) incorporating with olive pomace (OP). The effect of olive pomace on the engineering properties of clay bricks before and after baking process was investigated. The main objective is to show the effectiveness of earth bricks bio-based with (OP) in improving the thermal insulation of buildings. The first step was to carry out geotechnical analysis of the soil. Different percentage addition ratios: 0, 5, 10, 15, and 20% in weight of OP were adopted in order to evaluate the thermal impact of olive pomace on fired and unfired clay bricks. The thermal transport properties of prepared specimens were measured using the hot disc method. The particle size distribution showed a clay fraction of 45.2% for the soil. The Atterberg limits show a moderate plasticity for this soil. The X-ray diffraction analysis of the studied soil shows that it is composed of several minerals (Kaolinite, Illite, Quartz, Calcite and Goethite). Thermal analysis by the Hot Disk method showed a reduction of (43.1–39.7%) in thermal conductivity for the clay-olive pomace 20% (dried-baked) composites respectively, compared to earth alone, resulting in a significant increase in thermal resistance. Finally, a comparative analysis at a building-scale using TRNSYS was carried out. Two scenarios were considered: building with (i) conventional fired clay brick walls and (ii) OP-fired clay brick walls. The results respectively show a reduction of 23.7% and 6.3% in the annual heating and cooling loads, confirming the efficiency of the clay-olive pomace composites.

Thermal insulation of mud bricks made with walnut shells: Characterization and simulation study

This work aims to study the thermal performance of a new bio-composite (clay-walnut shell). Firstly, a geotechnical analysis was carried out on the soil. Different percentage additions: 0, 10, and 20% by weight (wt.%) of walnut shells were adopted to evaluate the thermal impact of WS on unfired clay bricks. Then, the thermophysical properties of produced bio-composites were compared with those of clay alone. The thermal transport properties were measured using the hot disk method. Geotechnical analysis showed that the base material (soil extracted from Nador city; eastern Morocco) has a high clay fraction of 51.8 % and moderate plasticity. Thermal analysis showed that WS improves the thermal insulation of mud bricks while reducing the density. Introducing 20 wt% WS decreased the thermal conductivity of clay by 45.22%, resulting in an increase in thermal resistance. Finally, a comparative study on the dynamic thermal behavior of two types of walls (concrete block wall and clay brick wall − 20 % by weight of walnut shells).The numerical findings revealed that the use of the developed composites increased the energy performance of residential buildings allowing respective savings (10.8% − 7.94%) of energy for heating and cooling needs, motivating the proposal to use WS as a new aggregate for construction.

Thermophysical characteristics of cement-based mortar incorporating spent coffee grounds

This work aimed to evaluate the efficacy of recycling Spent Coffee Grounds (SCGs) in cement to prepare bio-based mortars with improved thermal insulation. Different SCGs weight concentrations ranging from 0 to 40wt% were considered as partial replacement ratios for the development of cement mortar composites. The thermophysical performance of prepared formulations was studied experimentally using the hot disk method. In addition, the optimal incorporation rate for suitable SCG-based cement mortars was determined. The results indicated the possibility of recycling up to 30% by weight of coffee waste for mortar production. A significant enhancement in thermal insulation was observed in mortar composites incorporating SCGs. Replacing 30wt% of cement by SCGs showed a decrease of about 70.8% in the mortar’s thermal conductivity and 45.7% in the thermal diffusivity. The experimental investigation revealed that 5wt% SCGs was to be the optimal incorporation rate for designing eco-efficient mortars. Adding only 5wt% SCGs can improve the thermal insulation of mortars by 58% and reduce their thermal diffusivity by 34%. Therefore, SCGs present a promising bio-waste aggregate for developing thermally insulating mortars with low environmental impact at an industrial scale.

Measurements of heat capacity and thermal conductivity of β-Ga2O3 and β-(AlxGa1–x)2O3 bulk crystals grown by the Czochralski method

One of the application fields of bulk gallium oxide crystals is the manufacture of substrates for epitaxial growth of device structures for power electronics and optoelectronics in the Ga2O3/(AlxGa1–x)2O3 system. For most instrument designs, the substrate serves as a channel for heat removal from the device to an external heat sink. This property stresses the importance of information about the thermal characteristics of bulk crystals of gallium oxide and a solid solution of gallium and aluminum oxide, particularly about the heat capacity and thermal conductivity. In this work, we measured the heat capacity of bulk crystals of the β-modification of pure gallium oxide (β-Ga2O3) obtained by the Czochralski method, as well as of a double solid solution of gallium and alumina oxide β-(AlxGa1–x)2O3 in the range of temperatures from 25 °C to 480 °C and for various values of the Al concentration. Samples of bulk crystals were grown in an industrial installation “Nika-3” by pulling from the melt (Czochralski method). Further, the specific heat was measured on samples specially prepared from bulk crystals by differential scanning calorimetry. The thermal conductivity in the [010] crystallographic direction was measured by the method using a flat heat source (hot disk method). The dependence of the specific heat capacity of β-(AlxGa1–x)2O3 crystals on Al concentration was obtained for the atomic concentration of aluminum ranging from 0 (pure gallium oxide) to 9.11 at.%. The influence of the Al content on the heat capacity of the material is analyzed. The temperature dependence of the thermal conductivity of β-Ga2O3 in the [010] direction (direction of growth) in the temperature range from 43 °С to 120 °С was also obtained. The results of the study can be used to investigate the thermal properties of gallium oxide, as well as to solve the problem of heat removal for electronic devices based on gallium oxide.

Thermal conductivity of biobased insulation building materials measured by hot disk: Possibilities and recommendation

The Hot Disk transient plane source (TPS) method allows characterizing the thermal properties of various materials in a few minutes. Particularly, it is increasingly used for evaluating thermal conductivity of insulation building materials. However, the results of such measurement frequently differ from steady state measurements because of the significance of heat transfer into the Hot Disk sensor. Even if improvements have been proposed for specific cases, they cannot be generalized, especially for heterogeneous materials like biobased building insulation materials. The objective of this study is to evaluate all previously evaluated sources of errors when conducting a measurement with current capabilities of Hot Disk commercial device. Three types of material are tested: conventional isotropic materials (like XPS), compressible anisotropic materials (like wood fiber insulation) and heterogeneous anisotropic materials (like light-earth biobased concrete). The influence of setting parameters (volumetric heat capacity, temporal bound for estimation) is analyzed in light of repeatability and reproducibility errors. The suitability of hot disk method based on isotropic or anisotropic model to characterize non-transverse isotropic heterogeneous materials is discussed and compared with steady state measurements. • Thermal conductivity is measured by hot disk and guarded hot plate. • Accurate results are obtained for isotropic building materials. • Large uncertainties are observed for biobased building materials. • Difficulties arise in evaluating anisotropic thermal behavior. • Source of errors and influencing factors are evaluated.

Comparing the ignition and burning hazards of sugar‐cane bagasse and hemp epoxy composites

SummaryThe feasibility of using sugar‐cane bagasse as a reinforcement for natural fiber composites and the performance of these composites under fire conditions was investigated. Plies were manufactured using a process, which involved alkali‐treating bagasse, blending, pressing, and drying. Soaking durations of 30 minutes and 24 hours were compared. Composites were then made with these plies using a light resin transfer molding process. The composites were characterized and compared to a commercial hemp fabric using thermogravimetric analysis for thermal stability and char yield, isotropic hot disc method for thermal conductivity and specific heat capacity, and cone calorimeter for flammability. The investigation found that bagasse plies could be successfully used in composite manufacture, but posed a greater ignition hazard, and a comparable burning behavior hazard to the commercial product when tested at a radiant heat flux of 35 kW/m2. Thirty minutes treating resulted in a ply, which resulted in a char yield of 28%. Although in the composite form, there were no significant differences between all sample groups. With regards to ignition, the hemp composite had the latest time‐to‐ignition of 137 seconds. Comparison of the thermal properties to the ignition times showed that higher values of thermal properties resulted in later ignition times. The composite with the 30‐minute treated bagasse had a total heat release of 159 MJ/m2 and average heat release rate of 263 kW/m2, while the peak heat release rate was lower for the 24‐hour treated bagasse at 537 kW/m2. Overall, no significant differences in the two treatment durations were observed.

Thermal conductivity of insulating refractory materials: Comparison of steady-state and transient measurement methods

Measurements of thermal conductivity with the heat flow meter, laser flash method, hot disk method and hot wire method are compared on two kinds of refractory materials: Insulating Boards and Insulating Fireclay Bricks. Heat losses, humidity, anisotropy and heterogeneity can explain the variation in thermal conductivity values obtained with the different techniques. If they are taken into account in the analysis, discrepancy within 10% can be found. The choice of the technique depends on the investigated material and on the level of information required.

Morocco’s housing challenge: Effect of current marketed building materials on the energy performance of residential buildings

The paper provides a research on the energy performance of current marketed building materials used for household construction in eastern Morocco. Firstly, the characterization of the thermophysical properties of commonly used building materials (cement, plaster, hollow bricks and insulation boards) was carried out using the Hot Disk method. A local building material database of eastern Morocco region was developed. It was found that the thermal conductivity of the most affordable insulation boards was of 0.03 W/mK, while the thermal conductivity of cement-based products ranged from 0.65 to 0.7 W/mK. The experimental results show that the Moroccan market of building materials cannot participate in promoting eco-construction and designing efficient lightweight building envelopes at local level. Therefore, a strong focus on the development of local low-cost insulation materials for building applications are needed. The numerical building performance analysis shows that available building practices are only efficient for passive heating. Further studied on passive cooling techniques are greatly required for designing low energy buildings in Morocco.

Mechanical, Thermal and Thermomechanical Properties of Sponge Iron Slag filled Needle-Punched Nonwoven Jute Epoxy Hybrid Composites

In the present research work, the needle-punched nonwoven jute epoxy composites are fabricated by varying the weight percentages of sponge iron slag in vacuum assisted resin transfer molding technique. This study examines the physical, mechanical and thermomechanical properties (i.e., density, water absorption, tensile, flexural, inter-laminar shear strength, compression, impact, fracture toughness and dynamic mechanical analysis) of unfilled and 8 wt.%, 16 wt.% and 24 wt.% of sponge iron slag filled composites under controlled operating conditions. Moreover, it is shown that all the mechanical properties improved with the increased in sponge iron slag content except for tensile strength which increased only upto 16 wt.%. This study also attempted for the analysis of thermal conductivity of the unfilled and particulate filled composites in experimentally by hot disc method. This work also presents both existing empirical models and numerical simulation analysis to evaluate the thermal conductivity of the developed composites. The numerical simulation values of the thermal conductivity demonstrated good agreement with the experimental values. At the end, Cole-Cole plot is drawn between loss modulus and storage modulus to understand the nature of the proposed composites.

Thermal properties of wood measured by the hot-disk method: comparison with thermal properties measured by the steady-state method

The hot-disk method is a transient method for the measurement of thermal properties. This method can measure both the thermal conductivity and thermal diffusivity in a short time for isotropic materials. To establish a method for measuring the thermal properties of wood by the hot-disk method, the relationship between the thermal properties of wood obtained by the hot-disk method and those obtained by the steady-state method was investigated. The thermal properties were measured by the hot-disk method using small pieces of kiri (Paulownia tomentosa), sugi (Cryptomeria japonica), hinoki (Chamaecyparis obtusa), yachidamo (Fraxinus mandshurica), and buna (Fagus crenata) when the hot-disk sensor was in contact with the cross section, radial section, and tangential section. The thermal conductivities in the longitudinal, radial, and tangential directions were also measured by the comparison method using the same specimen. The thermal properties obtained by the hot-disk method and the steady-state method were compared, based on the assumption that the thermal diffusivity measured by the hot-disk method was the geometric mean of that in the two main directions in the plane of the sensor, and the thermal conductivity measured by the hot-disk method was a power of that in three main directions. As a result, the thermal conductivity obtained by the hot-disk method was 10–20% higher than that obtained by the steady-state method; the thermal diffusivity measured by the hot-disk method was equal to that obtained by the steady-state method on average, while in the former thermal diffusivity varied widely. These results were found to be explainable in terms of the Dufour effect, which is the heat flow induced by the mass flow caused by the heating of the sensor, and the existing findings on the time dependence of the sensitivity coefficient in the hot-disk method. The present study proposed two methods for calculating the thermal properties of wood from the hot-disk method were proposed, and it was found that the errors between the obtained thermal properties and those obtained by the steady-state method differed depending on the calculation method.

Stability and Thermo-Physical Properties of Ethylene Glycol Based Nanofluids for Solar Thermal Applications

This article summarizes research involving the evaluation of the thermo-physical properties of ethylene- glycol-based solar thermic fluids oxidized multi-walled carbon nanotubes. Nanofluids were prepared with Ethylene glycol and water as base fluids in 100:0, 90:10 and 80:20 ratios. Base fluids of three categories were dispersed with surfactant-assisted multi-walled carbon nanotubes (MWCNTs) and oxidized MWCNTs in the weight fractions of 0.125, 0.25, and 0.5 percentages to check the influence of surface modification technique on the thermophysical properties. The variation in zeta potential is studied to examine the dispersion stability during 2 months. Thermal conductivity and dynamic viscosity were measured by hot disk method and Anton paar viscometer, respectively. Significant enhancement of thermal conductivity by 15 to 24 % was observed when the base fluids are dispersed with oxidized MWCNTs. In the case of nanofluids dispersed with surfactant-assisted MWCNTs, the improvement is significantly less compared to oxidized MWCNTs. Nanofluids' dynamic viscosity is found to be higher compared to base fluids in the temperature range of 50 to 70 oC. A comprehensive mathematical equation suitable for all weight fraction of MWCNTs and volume percentages of Ethylene glycol was developed, which can forecast the temperature range. The correlation could fit well with the experimental data in reasonable limits.

MOC Cement-Based Composites with Silica Filler and Wood Chips Ash Admixture

As Portland cement and cement-based materials are the most widespread materials in construction industry, there is a concern to develop and search cement alternative materials with similar or better functional properties and a lower negative environmental impact. Magnesium oxychloride cement (MOC) is considered as low-energy and low-carbon binder possessing some advantageous properties superior to Portland cement. Therefore, lightweight MOC-based composites were designed and tested in the presented study. As filler, silica sand was used in composition of control composite mix. Later, it was partially replaced with wood chips ash coming from bioenergy production from biomass. The chemical composition and morphology of wood chips ash were characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) analyses. For the hardened composites, bulk density, specific density, and total open porosity were measured. Among mechanical parameters, flexural and mechanical strengths were tested. The thermal performance of composites was studied using a transient hot disk method and the assessed parameters were thermal conductivity and volumetric heat capacity. The use of fly ash led to the great decrease in porosity compared to the control materials with silica sand as only filler. The mechanical strength of all developed materials was high. Both the compressive strength and flexural strength decreased the dosage of wood chips ash in composite mix. However, the decrease in mechanical resistance was lower than the send replacement ratio. It clearly proved assumption of filler function of fly ash, whereas its assumed reactivity with MOC cement components was not proven. The heat transport was partially mitigated by wood chips use, similarly as heat storage. Based on the obtained data, the developed composites were considered as alternative low-carbon materials possessing interesting functional properties for construction practice. Moreover, the reuse of by-product from biomass bioenergy treatment can be considered as an environmentally friendly solution for production of sustainable advanced building materials.

Evaluation of measuring thermal conductivity of isotropic and anisotropic thermally insulating materials by transient plane source (Hot Disk) technique

The transient plane source (TPS) technique, also referred as the Hot Disk method, has been widely used due to its ability to measure the thermal properties of an extensive range of materials (solids, liquids, and powder). Recently, it has been recognized that typical Hot Disk sensors can influence TPS results of thermally insulating materials and lead to an overestimation of thermal conductivity. Although improvements have been proposed, they have not yet been implemented in the commercial TPS, leaving researchers with non-standardized modifications or options provided by a commercial Hot Disk apparatus. An empirical study of thermally insulating materials such as extruded polystyrene (XPS) and aerogel blanket is conducted in order to address the factors that affect the reliability of thermal conductivity k obtained using the commercial TPS apparatus. Sensor size, input power, duration of the measurements, applied pressure, and, in the case of anisotropic materials, heat capacity are investigated, and the results are compared with those using a Heat Flow Meter apparatus. The effect of sensor size on the k value is ascribed to heat loss through connecting leads and is more pronounced in smaller sensors and in materials with lower k values. In the case of XPS and aerogel, the effect becomes minimal for sensors with a radius r ≥ 6.4 mm. The low input power yields a high scattering of the results and should be avoided. Applied contact pressure and the tested region of the specimen play an important role in experiments with low-density fibrous materials due to the large percentage of heat being transferred by radiation and the heterogeneous nature of the samples, respectively. Additionally, the sensitivity of anisotropic measurements to the value of the material’s volumetric heat capacity (ρCp) is shown, emphasizing the need for the precise determination.

Development of polyurethane foam incorporating phase change material for thermal energy storage

The major aim of the present study is to improve the thermal characteristics of polyurethane foams (PUFs) that have been almost exclusively used for thermal insulation purposes but can also play a role in potential thermal energy storage components as a matrix material.To overcome the low thermal conductivity of the of PUFs matrix, a synthesized phase change material (PCM) based on paraffin and calcium carbonate (CaCO3) has been developed to enhance the thermal conductivity and thus achieve a more effective charging and discharging process. The synthesized PCM (PCM@CaCO3) exhibited a good phase change performance with significant thermal storage capacity and thermal stability compared to commercial based PCM (PCM@BASF).Different PUFs formulations incorporating PCM (PCM@CaCO3 and PCM@BASF) were used to produce PUFs panels (rigid and soft PUFs panels). The thermal conductivity of the PUFs panels was measured using the transient plane heat source method (HotDisk Analyser, TPS 2500 S) and the thermal flux metre method (steady-state method). The results obtained revealed that, regardless of the method used, the thermal conductivity profile has a similar increasing trend before and after the bounds of the PCM phase change transition zone, whilst during PCM phase transition both methods showed a decreasing trend of the thermal conductivity as the temperature increased.In addition, this work presents and discusses the limitation of the HotDisk method to analyse panels composed by multilayers.

Enhanced Figure of Merit in Bismuth-Antimony Fine-Grained Alloys at Cryogenic Temperatures

Thermoelectric (TE) materials research plays a vital role in heat-to-electrical energy conversion and refrigeration applications. Bismuth-antimony (Bi-Sb) alloy is a promising material for thermoelectric cooling. Herein, a high figure of merit, ZT, near 0.6 at cryogenic temperatures (100–150 K) has been achieved in melt-spun n-type Bi85Sb15 bulk samples consisting of micron-size grains. The achieved ZT is nearly 50% higher than polycrystalline averaged single crystal ZT of ~0.4, and it is also significantly higher than ZT of less than ~0.3 measured below 150 K in Bi-Te alloys commonly used for cryogenic cooling applications. The improved thermoelectric properties can be attributed to the fine-grained microstructure achieved from rapid solidification, which not only significantly reduced the thermal conductivity but also mitigated a segregation effect. A record low thermal conductivity of ~1.5 W m−1 K−1 near 100 K was measured using the hot disk method. The thermoelectric properties for this intriguing semimetal-semiconductor alloy system were analyzed within a two-band effective mass model. The study revealed a gradual narrowing of the band gap at increasing temperature in Bi-Sb alloy for the first time. Magneto-thermoelectric effects of this Bi-Sb alloy further improved the TE properties, leading to ZT of about 0.7. The magneto-TE effect was further demonstrated in a combined NdFeB/BiSb/NdFeB system. The compactness of the BiSb-magnet system with high ZT enables the utilization of magneto-TE effect in thermoelectric cooling applications.

Effect of heat treatment on the thermophysical properties of copper-powder-filled polycarbonate and polycarbonate containing paraffin

Abstract In this study, the effect of paraffin (PR) and copper (Cu) incorporation in polycarbonate (PC) was investigated using differential scanning calorimetry (DSC). The effect of PR incorporation in PC was investigated using thermogravimetric analysis (TGA). The effect of thermal treatments on thermophysical properties was studied in PC/PR and PC/Cu composites by using the hot-disk method and a periodic method (DICO). Specimens were heated at 160°C (Tg + 15°C), then two different cooling methods were employed: furnace cooling (annealing) and water cooling (quenching) at 0°C and 35°C. The DSC results showed that a solid-liquid transition occurred in all PR formulations, as well as showed the plasticizing role of the PR additive. Thermal stability decreased with the addition of PR. Thermal conductivities (λ) increased with increasing Cu content and decreased with PR additive content, and the annealed samples showed a higher thermal conductivity (λ) than quenched ones. Meanwhile, a small difference between the thermal conductivity of the DICO samples and the hot-disk samples was noticed.

Physico-chemical, thermal, thermodynamic and kinetic characterization of a porous material (Di-calcium phosphate)

The sorption isotherms of di-calcium phosphate (DCP) were determined using the gravimetric method at four temperatures. The sorption curves were fitted by the Guggenheim-Anderson-deBoer (GAB) model. The dehydration process was studied by means of X-ray diffraction. Thermo-gravimetric /differential thermal analyses (TGA / DTA) were used to record the loss of water and the nature of the products was studied by Fourier Transform Infrared Spectroscopy. The morphology of DCP was tested using the electronic scanning morphology (SEM). The thermal conductivity was determined using Hot Disk method. DCP convective drying kinetics modeling was conducted by the experimental study of the aero-thermal condition effects. The drying characteristic curves were then modeled using the nonlinear regression functions of MATLABR2013a. The curves predicted by the GAB model coincide well with the majority of the experimental points of the sorption isotherms. The net isosteric heat is mathematically expressed by second-order exponential function of the water content. SEM shows the presence of anhydrate and di-hydrate forms of DCP. DCP loses molecules of water when heated in two stages. Hot Disk method shows that the thermal conductivity depends heavily on the drying temperature and the product moisture. Midilli-kucuk is considered the most suitable model for the experimental results.

A new method for measuring the thermal conductivity of small insulating samples.

Due to the limited size of samples prepared at the lab scale, characterizing the thermal properties of new materials may be problematic, and this makes it all the more difficult to optimize them. This statement especially applies to the development of innovative thermal (super)insulators. In this work, we demonstrate that the hot disk method, which might be preferred for such kinds of studies because of the low sample size it can allow in practice, is unable to provide realistic values of thermal conductivity in the case of insulators. A new method was thus developed, called Calibrated Tiny Hot Plate (CTHP). The corresponding heat transfers were modeled, and the two unknowns of the model were obtained by calibration with insulating samples whose thermal conductivity was precisely measured with a reference (guarded hot plate) method. We show that the CTHP is able to estimate conductivities within the range 0.014-0.2 W m-1 K-1 based on samples having thicknesses ranging from 3 to 9 mm and diameters as low as 15 mm. The accuracy was generally much better than 10%, which is a remarkable result for characterizing so small insulating materials.

Numerical investigation of mechanical and thermal characteristics of binary-sized pebble beds using discrete element method

The characteristic identification of the functional materials is important in predicting the performance of a breeding blanket, which is one of the main components of the fusion power plant. The functional materials of the solid-type ceramic breeding blanket are mainly used in the form of pebble beds. Various experimental methods such as laser flash, hot wire, and hot disk method have been utilized to assess the thermal properties of the pebble bed. In recent years, numerical techniques have been also introduced to evaluate mechanical characteristics as well as thermal characteristics of pebble beds. In this study, the mechanical and thermal behaviors of the binary-sized pebbles in a cuboidal container are simulated considering the contact interaction of the pebbles by means of discrete element method. Through a series of numerical simulations of pouring the pebbles into the vibrating container, we investigate the effect of the size difference of the binary-sized pebbles on the packing structures of the pebble beds. The connectivity of binary-sized pebbles is also discussed in terms of the average contact force of the pebbles. Furthermore, heat conduction between the pebbles is considered based on the packing configurations obtained from the mechanical analysis, and the thermal properties of the pebble beds are qualitatively evaluated in terms of the effective thermal conductivity of the pebble beds.

Thermoelectric characterization of nickel-nanowires and nanoparticles embedded in silica aerogels

Embedded nickel nanowires (NiNWs) and nickel nanoparticles (NiNPs) in silica aerogels at three different concentrations are characterized by scanning thermal microscopy, a Hot disk method and four probe measurements to consider them as potential thermoelectric materials. NiNW samples exhibit 9 orders of magnitude improvement in thermoelectric figure of merit while the embedded NiNPs samples show a 6 orders of magnitude improvement when the concentrations are increased from 0 to 700 ppm. The electrical resistivity is highly sensitive to the concentration of NiNWs and NiNPs in the silica aerogels, while the thermal conductivity remains largely unchanged over temperature range 300 to 420 K. The electrical conductivity σ follows a percolation scaling law of the form σ ∝ (W − Wc)t with critical weight fraction (Wc) to form a conductive network at range 0.04-0.06 Wt% and 0.08-0.1 Wt% for embedded NiNWs and NiNPs, respectively. The investigation suggest that further optimization of the concentration of nanomaterials in aerogels could yield promising thermoelectric properties.