High Conductivity Values Research Articles

Effective Thermal Conductivity and Borehole Thermal Resistance in Selected Borehole Heat Exchangers for the Same Geology

Investigating the constructions of borehole heat exchangers with high efficiency (unit heat transfer between the heat carrier and ground) is important. One of the means to improve efficiency is the use of the most efficient construction of the borehole heat exchanger. The paper describes research on borehole heat exchangers’ thermal efficiency, which is mainly characterized by parameters obtained from a thermal response test: effective thermal conductivity and borehole thermal resistivity. The borehole heat exchangers of the Laboratory of Geoenergetics in Poland were studied. Based on thermal response test interpretation and empirical equations, one of which is proprietary, the heat transfer is calculated independent of the duration of the thermal response test. Other conditions for using borehole heat exchangers in downtowns are discussed. The research aims to determine the best borehole heat exchanger design from five basic possibilities studied. A lack of unequivocal statements regarding this matter in the literature was observed. The influence of the interpretation method on the research results is determined. A single U-tube system filled with gravel is shown to be the most advantageous design by a very small margin. The applied interpretation methods, however, confirm the hitherto ambiguity in the selection of the best construction. The maximum heat carrier temperature at the end of thermal response tests was 32 °C for a geological profile mostly made up of clay (low thermal conductivity) and 23 °C for Carpathian flysch (sandstones and shales, with a higher value of conductivity).

Influence of Annealing Temperatures on the Structural Behaviour and Electrical Properties of La(FeSi)<sub>13</sub> Alloys

This paper study the effect of structural behaviour and electrical properties in cubic NaZn13-type La (FeSi)13 compounds annealed at different high temperatures from 1000oC to 1200oC. The Raman spectroscopy measurement revealed a different level of coexistence of La (FeSi)13-type phase and α-Fe in 1000oC, 1100oC and 1200oC annealed samples. The different level coexistence of the phases suggested that the samples show a significant phase change with different annealing temperature methods. This finding has also supported by impedance analyzer measurement, where the pattern shows that the 1000oC and 1100oC samples have similar behaviour waveform pattern compared to the 1200oC, which has different behaviour. Besides, the impedance pattern clearly shows that the propagation of the signal for the 1000oC and 1100oC before it arrives in the conductor state (R=0.00) has high resistive values compared to 1200oC annealed samples. Further investigation on the electrical properties was done with the conductivity and tan delta measurements. The results show that 1200oC annealed sample have a high value of conductivity (S=18μ S/m) compares with 1100oC (S= 0.1μ S/m) and 1000oC (S=4.89n S/m). The tan delta measurements found that samples annealed at 1200oC temperature has low value of resistivity (tan ɗ = 0.117) compares with 1100oC (tan ɗ = 0.335) and 1000oC (tan ɗ = 0.482) respectively.

Thermal structure of the African continent based on magnetic data: Future geothermal renewable energy explorations in Africa

The defractal method was applied to the observed magnetic data and was used to estimate Curie point depth (CPD) i.e., depth to the base of magnetic sources (DBMS), near-surface geothermal gradient (GG), surface heat production and bulk crust thermal conductivity of Africa. A range of window sizes was tested using different values of the fractal parameter (α). The calculated DBMS ranges from 19 km to 112 km in Africa, and the GG varies from 15.9 °C/km to 30 °C/km (averaging 25 °C/km). Surface heat production values vary between 0.2 μW/m2 to 5.6 μW/m2, averaging 2.5 μW/m2. The calculated bulk crust thermal conductivity ranges from 1.4 W/mK to 3.4 W/mK with an average of 2.6 W/mK. In general, shallow DBMS, high GG, and high surface heat production coincide with known geothermal, volcanic, and seismic regions in Africa. Shallow DBMS, high GG, and high surface heat production were encountered in southeastern Africa, northeastern Africa (Egypt and Red Sea), and northern Africa (Hoggar region). High bulk crust thermal conductivity values are encountered in northern Africa (Algeria, Morocco, Libya), southeastern Africa and the East African Rift (EAR) regions.

Pressure-Responsive Conductive Poly(vinyl alcohol) Composites Containing Waste Cotton Fibers Biochar.

The development of responsive composite materials is among the most interesting challenges in contemporary material science and technology. Nevertheless, the use of highly expensive nanostructured fillers has slowed down the spread of these smart materials in several key productive sectors. Here, we propose a new piezoresistive PVA composite containing a cheap, conductive, waste-derived, cotton biochar. We evaluated the electromagnetic properties of the composites under both AC and DC regimes and as a function of applied pressure, showing promisingly high conductivity values by using over 20 wt.% filler loading. We also measured the conductivity of the waste cotton biochar from 20 K up to 350 K observing, for the first time, hopping charge transport in biochar materials.

The Effect of Tharthar-Tigris Canal on the Environmental Properties of the Tigris River Northern Baghdad, Iraq

The present study is considered the first on this sector of the Tigris River after 2003. It is designed for two aims, the first is to demonstrate the seasonal variations in physicochemical parameters of Tharthar-Tigris Canal and Tigris River; the second is to explain the possible effects of canal on some environmental properties in the Tigris River. Water samples were being collected monthly. Six sampling sites were selected, two on Tharthar Canal and four along the Tigris River, one before the confluence as a control site and the others downstream the confluence with the canal. For a period from January to December 2020, nineteen physicochemical parameters were investigated including air and water temperature, turbidity, electrical conductivity, salinity dissolved oxygen, percent oxygen saturation, biological oxygen demand, pH, total hardness, calcium, magnesium, sulphate, total dissolved solids, total suspended solids, total alkalinity, bicarbonate, nitrate and phosphate. The results showed that air and water temperatures were close in both Tigris and canal. The waters were well aerated, slightly alkaline and over saturation was recorded several times, while biological oxygen demand values did not exceed 5 mg/L along study period. The high values of conductivity, salinity, total dissolved solids, total hardness, calcium and sulphate ions in Tharthar water increased in the Tigris River below the confluence. Whereas, the low values of turbidity, TSS, total alkalinity and bicarbonate in the arm diluted in the main river. It has been concluded that Tharthar Canal affected the Tigris River by either increasing or diluting of the Tigris chemical components.

XPS studies on silver ion conducting solid electrolyte SbI3-Ag2MoO4

The silver ion conducting solid electrolyte containing antimony triiodide and silver molybdate synthesized by rapid melt quenching method in different stoichiometric compositions exhibits a high ionic conductivity value of 4.1 × 10−3 S cm−1 in a particular stoichiometric composition (SbI3)0.3-(Ag2MoO4)0.7. Generally, High ionic conductivity values in silver ion conductors may be due to the formation of silver iodide, AgI. The reason for high conductivity values was analyzed in terms of structural changes in this synthesized compound. In the present study, the expected presence of Ag+ and I- ions with their due binding energy and orbital state in XPS spectra were analyzed. In this XPS investigation, the presence of Ag metal in 3d3/2 and 3d5/2 states with a binding energy value of 373.8 and 367.8 eV respectively were ascertained. Similarly, I2 is in a 3d orbital state with 3d3/2 and 3d5/2 states with a binding energy value of 631.3 and 619.8 eV respectively. Respective photoemission values of Ag and I2 were found to be 6.0 and 11.5 eV. These values are in very good agreement with reference values quoted in the literature.

Manufacturing method of BSCF cathode for low-temperature solid oxide fuel cell-A review

The fuel cell is a device used to convert chemical energy to electrical energy through the electrochemical process. It does not involve any intermediate step of direct combustion and gives higher conversion efficiency when compared to a conventional system. Solid oxide fuel cell is a type of fuel cell which involves oxide-ion conducting electrolytes. It has several advantages in higher efficiency, lower sensitivity to fuel impurities, and inexpensive materials. Nowadays, Low-Temperature Solid Oxide (LT-SOFC) Fuel Cell is attracted due to its lower operating temperature range of 500–800 °C. The various advantages of LT-SOFC are reducing the degradation of components involved, cell durability improvement, and reducing the cost involved. In solid oxide fuel cells, cathode plays an essential role in the electrochemical reduction. Common cathode materials are yttria-stabilized zirconia, scandia-stabilized zirconia, Samaria-doped ceria (SDC), gadolinia-doped ceria (GDC), and lanthanum strontium gallium magnesium oxide (LSGM). These cathodes have a high value of ionic conductivity at low temperatures. Recently, BSCF type cathode is attempted by researchers due to its attractive performance in LT-SOFC. The main objective of this article reviews the manufacturing method of BSCF cathode and its fabrication route on LTSO fuel cells. The result of this review article is observed to acquire knowledge of various manufacturing method of BSCF cathode in LT-SOFC fuel cell.

Spatiotemporal Distribution of Cladocera and Rotifer of the Mangrove Waters of Mouanko (Coastal Cameroon): Influence of Some Abiotic Variables

The Mouanko mangrove is subjected to major anthropogenic activities such as agriculture, fishing and deforestation, hence information on Cladocerans and Rotifers amongst other aquatic organisms in order to monitor and manage this ecosystem is vital. The aim of this work is to study the physicochemical parameters of the environment that influence the diversity and spatiotemporal distribution of Cladocerans and Rotifers in the mangrove waters of Mouanko. This study was carried out from November 2019 to October 2020 at 8 sampling stations. Both biological and physico-chemical sampling and analyses were done following standard recommendations. The results of the phyico-chemical analyses revealed that the waters of the Mouanko mangroves were slightly basic (7.64 ± 0.71 UC), moderately oxygenated (69.56% ± 14.29%) with low levels of nutrients [ NO -2 (0. 06 ± 0.05 mg/L), NH+4 (0.39 ± 0.3 mg/L) and PO3-4 (up to 0.12 mg/L)] and high values of electrical conductivity (up to 6531.04 μS/cm), salinity (up to 3.71‰). 15 species of Cladocerans and 30 species of Rotifers were identified accounting for a total abundance of 612 ind/L. The species richness was higher in freshwater influenced zones (40 taxa) compared to marinewater influenced zones (17 taxa). Among these species, the Cladocera, Penilia avirostris was the most abundant in marinewater influenced zones (84 ind/L) while the Rotifer, Keratella tecta was the most abundant in freshwater influenced zones (64 ind/L). Shannon-Weaver’s diversity and Pielou’s equitability indices indicated that freshwater influenced zones host a diverse community with a tendency towards equi-partition of species while marinewater influenced zones revealed the opposite. The low levels of organic pollution indicator variables recorded and the high diversity of the freshwater influenced zones population studied attested to the low level of anthropization in this environment. High salinity and electrical conductivity values influence the distribution of these organisms.

One Step Fabrication of Aligned Carbon Nanotube Sheet via FC‐CVD Technique

The rising need for lightweight and strong mechanical structures has contributed significantly towards the development of CNT macrostructures; however, the interplay of parameters and their discontinuous synthesis have obstructed their delivery to commercial level. Herein, floating catalyst chemical vapor deposition technique (FC‐CVD) has been employed for the fabrication of 90 cm long CNT sheet via continuous production of CNT aerogel. High degree of graphitization, thermal stability and purity have been indicated by Raman spectroscopy (IG/ID = 10.03), thermogravimetric analysis, and SEM studies. Continuous winding of CNT aerogel has increased the alignment into the sample which resulted into high electrical conductivity value of 21400 S/m. Furthermore, the alignment has been quantified by calculating optical anisotropic ratio via polarized Raman technique and conductivity anisotropic ratio κ‖ /κ⊥ which were calculated to be 4.63 and 3.4, respectively, and show reasonable agreement. These findings indicate that a well correlation of synthesis parameters results in highly aligned CNT sheet structure in a single step.

Numerical modelling of a deep closed-loop geothermal system: evaluating the Eavor-Loop

<abstract> <p>Conventional geothermal energy systems are limited by hydrogeological conditions and environmental risks, and wind/solar solutions have issues with intermittency and the need for grid storage. Deep closed-loop geothermal systems such as the Eavor-Loop are championed as scalable, dispatchable, zero-emission alternative energy technologies, but as yet they are largely untested. A series of numerical models are created using the finite element method to evaluate the power output claims made by Eavor. The models use typical parameter values to create a simplified study domain. The modelling results show that the power output claims are plausible, although the upper range of their predictions would likely require production temperatures in excess of 150 ℃. The technology is shown to be scalable by adding additional lateral wellbore arrays, but this leads to a reduction in efficiency due to thermal interference. It is demonstrated that the presence of groundwater can improve power output at relatively high hydraulic conductivity values. Doubt is cast on the likelihood of finding such values in the deep subsurface. Flow rate is shown to increase power output, but the practicality of using it to follow energy demand is not established. Various limitations of the study are discussed, and suggestions are made for future work which could fill in the remaining knowledge gaps.</p> </abstract>

Highly efficient synthesis of titanium phosphate precursor for electroactive materials

In recent years titanium phosphates (TiPs) have aroused considerable interest as multi-functional materials. Known methods of TiPs synthesis are rather complicated because they are based on wet chemistry in terms of which one-step synthesis of pure TiP fails. It is highly welcomed to develop a new approach to TiP production. In this work the novel minimalistic approach to the synthesis of two titanium phosphates of different composition from a solid TiOSO 4 ·H 2 O precursor has been proposed. Despite the fact that the TiOSO 4 solutions are widely used for the synthesis of titanium phosphates, the solid compound as a titanium source has never been used before. The new mechanochemistry-based synthesis provides easy access to obtaining TiO(OH)(H 2 PO 4 )·H 2 O and Ti(HPO 4 ) 2 ·H 2 O (α-TiP) for 3 h and 5 h, respectively. The substitution of protons in α-TiP with Li + and Al 3+ by ion-exchange reactions provide the formation of Li 1.5 Al 0.5 Ti 1.5 (PO 4 ) 3 which is electroactive material. The proposed synthesis procedure is more technologically attractive compared with traditional methods, and enables direct production of highly dispersed monophasic powder (100–300 nm) of desired composition at 823 K. The material obtained demonstrates high conductivity value of 7.8·10 −4 S cm −1 at 298 K, low activation energy of 0.27 eV, and can be used as a solid electrolyte for practical application in all-solid-state lithium batteries.

ANALISIS PENGARUH NILAI KONDUKTIVITAS HIDRAULIK DAN DISPERSIVITAS DINAMIK TERHADAP REMEDIASI AIR TANAH MENGGUNAKAN SIMULASI NUMERIK

Groundwater remediation is one of the solutions to restore the contaminated groundwater. This study was conducted to determine the effect of hydraulic conductivity and dynamic dispersivity on the groundwater remediation effectiveness. As a case study, in 2020, in an area located in Balikpapan, groundwater remediation will be carried out by injecting water containing NaOH through five wells and pumping it back through five wells to form a cycle. The method used is a numerical simulation consisting of groundwater flow simulation, mass transport, and sensitivity analysis. The results show that it takes 124 to 300 days for the injected NaOH to arrive at the pumping wells. The sensitivity analysis results show that when the hydraulic conductivity value is ten times greater, the time required is reduced to 84 to 172 days. Meanwhile, when the dynamic dispersivity is twice larger, the time required is reduced to 75 to 189 days. These results indicate that the groundwater remediation method will be effective for aquifers with high hydraulic conductivity and dynamic dispersivity values. For the study area, the groundwater remediation is suggested to be carried out by increasing the number of injection and pumping wells with a relatively close distance, i.e., around 10 meters, so that NaOH arrives at the pumping wells more quickly.Keywords: groundwater, remediation, hydraulic conductivity, dynamic dispersivity, numerical simulation

CHEMICAL CHARACTERISATION OF ACID MINE DRAINAGE FROM VALEA ȘESEI TAILING DAM (NW OF ROMANIA) AND ITS IMPACT ON SURFACE WATER QUALITY

The acid mine drainage (AMD) can be a major source of water and soil pollution. To evaluate the chemical composition of the AMD and its impact on surface waters, a total of 132 water samples, both surface and waste waters, were collected during four field campaigns in November 2018, December 2018, March 2019 and April 2019. There were also collected several samples from the tailing dam material and sediments from the rivers where acidic waters are discharged. The physico-chemical parameters (pH, redox potential, electrical conductivity, total dissolved salts and salinity) were measured by a portable multiparameter (WTW multi350i, Germany), while the dissolved ions (NO2-, NO3-, Br-, F-, Cl-, PO43-, SO42-, Li+, Na+, NH4+, K+, Mg2+ and Ca2+) were analysed by ion chromatography and the metal content (Cu, Zn, Fe, Cr, Cd, Ni, Pb) was determined by atomic absorption spectrometry. Most of the water samples had an acidic pH, with high electrical conductivity values (up to 9,360 µS/cm). The waters had a high level of SO42- (up to 8141.8 mg/l), Fe (up to 1,216.2 mg/l), Cu (up to 71.9 mg/l) and Zn (up to 61.98 mg/l). The tailing dam material was characterised by high levels of Fe (39.87 – 40.72 g/kg), Zn (81.3 – 241.1 mg/kg), Cu (343.5 – 942.3 mg/kg) and Pb (41.4 – 77.1 mg/kg). The analyses indicated the negative impact of AMD discharge in surface waters, which proved to have high levels of SO42- and heavy metals.

Application of Very Low Frequency (VLF) Method for Estimating Karst Underground River in Tanjungsari District

Drought is the main problem for clean water needs in Tanjungsari district. This research aims to provide information on the existence of underground river for deep well drilling. The methods used are geologic-structural analysis and application of Very Low Frequency (VLF) methods. Strike and dip measurements of 150 joints were conducted in the research area. Analysis using rosette diagram shows that the main geologic-structure orientation has a direction of Northwest - Southeast and Northeast – Southwest. Very Low Frequency (VLF) acquisition was measured across the possible occurrence of subsurface water flow directions predicted from geologic-structural analysis. The length of the VLF acquisition line is 2500 meters with 30 m spacing and 108 points acquisitions. The direction of VLF line is N 2700 E. The result shows that there are 2 locations that have high conductivity values, appearing at 1800 meters and 2200 meters. The results of this structural and VLF analyses indicate the existence of underground river at the location of 454326 N, 9105870 E.

Physical properties of double perovskites Rb2XCl6 (X= Sn, Te, Zr): Competitive candidates for renewable energy devices

Ab-initio computations are performed to analyze the Lead-free double perovskites Rb2XCl6 (X = Sn, Te, Zr) for solar cells and renewable energy. The FP-LAPW method has been adopted to compute the mechanical, optoelectronic and thermoelectric properties. The stability of the three compounds is verified through the elastic constants ensuring the ductility and the anisotropic nature of the double perovskites compounds. Both compounds Rb2TeCl6 and Rb2ZrCl6 have indirect band gap equal 2.54 eV, 3.46 eV respectively, but Rb2SnCl6 compound have direct band gap equal to 2.40 eV in the near visible region, which make them potential candidates for visible light solar cells. The optical spectra have been elaborated in terms of dielectric constants, absorption of light, refractive index, and reflection of light. The maximum absorption bands are recorded in the wavelength range of 620 nm–310 nm. Finally, thermoelectric properties are calculated by BoltzTraP code, which depicts high values of Seebeck coefficient and low thermal conductivity. Therefore, the above said parameters ensure their importance for renewable energy.

Anisotropically thermal transfer improvement and shape stabilization of paraffin supported by SiC-coated biomass carbon fiber scaffolds for thermal energy storage

Phase change materials (PCMs) play a promising application in the field of heat management and energy storage, which are restricted by the problems of low thermal conductivity and leakage. In this work, 3D porous carbon scaffolds as-consisted of SiC-wrapped biomass carbon fibers were prepared, which were used as the thermal conductive skeleton and shape stabilizer for paraffin PCM. In particular, the porous carbon scaffolds were designed with 1D arranged carbon fibers and hierarchical pore structure, thereby the resulting composite PCMs indicate anisotropically improved heat transfer and good anti-leakage properties. High thermal conductivity values of 0.61 W m−1 k− 1 in the axial direction (> 3 times of paraffin) and 0.48 W m−1 k−1 in the lateral direction were obtained for the composite with a filler ratio of 10.4 wt%. The composite also presented well-behaved thermal cycling stability and high heat storage capacity (186 J g−1). With a high heat storage capability and anisotropically improved heat transfer properties, the biomass carbon supported PCMs indicate enormous potentials in thermal management applications.

Preliminary laser treatment of materials for diffusion bonding in space and aviation technologies

The paper investigates the possibility of improving the technology of diffusion welding, which can be used both for joining dissimilar materials for the manufacture of complex devices in the aerospace industry on the ground, and for repair and design in outer space. A laser treatment by nanosecond laser pulses of the ultraviolet range was carried out for surface modification of industry alloys (CrNi55CuВZn, steel AISI 316, Cu–Cr bronze) used in space technology due to high values of thermal and electrical conductivity. It was shown that the preliminary laser treatment leads to an improvement in the properties of the weld: an increase in tensile strength by more than 10%, and tensile strain by more than 20% for certain joints of materials. Also, laser pre-processing can improve the productivity of the welding process, in particular, reduce the temperature and shorten the welding time.

Ab-initio study of lead-free double Perovskites Cs2AgZBr6 (Z = Bi, Sb) for Solar cells and other renewable energy applications

Ab-initio computations are performed to analyze the Lead-free double perovskites Cs2AgZBr6 (Z ​= ​Bi, Sb)for solar cells and renewable energy. Modified Becke and Johnson potential (TB-mBJ) has been adopted to compute the electronic and optical properties. The computed lattice constants are found in good agreement with the reported experimental data. Band gaps calculations for Cs2AgBiBr6 and Cs2AgSbBr6 reveal their indirect nature and are quantified 2.0 ​eV and 1.39 ​eV which make them potential candidates for visible light solar cells. The optical spectra have been elaborated in terms of dielectric constants, absorption of light, refractive index, and reflection of light. The maximum absorption bands are recorded in the wavelength range of 620 ​nm–310 ​nm. Finally, thermoelectric properties are calculated by BoltzTraP code, which depicts high values of Seebeck coefficient and low thermal conductivity. Thus, performed theoretical calculations suggest the studied materials for potential application in renewable energy field.

Synthesis and characterization of triazole based nanocrystalline cellulose solid proton conductors

• Successful preparation protocol of the anhydrous nanocomposite proton conductor. • The U.S. Department of Energy durability standards for fuel cell membranes met. • Proton transport determined by the molecular reorientation of the triazole ring. We designed and synthesized new proton-conducting materials (CNC-Tri) based on natural polymer composed of nanocrystalline cellulose (CNC) doped with different concentrations of 1 H -1,2,3 triazole (Tri). The CNC functionalization with Tri does not affect cellulose structure. The material has the form of semitransparent polymer film. The presence of Tri in the CNC matrix was confirmed by the infrared spectra. The activation energies for the desorption of water, triazole evaporation, and the degradation of the CNC matrix, were evaluated. The proton conduction takes place under anhydrous conditions up to 180 °C and the highest value of conductivity is equal to 4.0 × 10 -4 S/m at 160 °C. The behavior of conductivity is consistent with the Grotthuss mechanism and proton transport is conditioned by the triazole ring reorientation revealed by the solid-state 1 H- 13 C CPMAS NMR. CNC-Tri was found to show better thermal properties when compared to the previously tested CNC doped with imidazole (Im), but with lower conductivity. Possible reasons for these differences are discussed in this article.

High dielectric flexible thin films based on cellulose nanofibers and zinc sulfide nanoparticles

Nanocomposites have become potential candidate materials for integration into high-frequency electronics. In the current work, ZnS nanocomposite films were successfully prepared from cellulose nanofibers (CNF) - isolated from bagasse pulp- with different weight ratios of ZnS nanoparticles (ZnS NPs). The structure was characterized by infrared and ultraviolet–visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM)/ Energy dispersive X-ray spectroscopy (EDX). Infrared spectroscopy proved the presence of interactions between cellulose and ZnS nanoparticles. The SEM and EDX analysis showed that ZnS nanoparticles were well dispersed in the cellulose matrix. Band gap width of Zn/CNF nanocomposites film calculated from UV–Vis spectra was 2.64 eV which is lower than pure CNF (4.5 eV). Electrical properties were investigated within the frequency range of 100 Hz−5 MHz, and temperature range of 25–120 °C. DC- electrical conductivity was investigated and the activation energy Ea was estimated from the Arrhenius relation. The effect of wt. % of ZnS nanoparticles on electrical properties as dielectric constant, and ac-electrical conductivity (σac) were studied. The results showed that the all ZnS/CNF nanocomposite thin films had semiconductor properties and the 5 wt% ZnS NP sample had the highest conductivity value. The results indicate that the prepared flexible ZnS/ CNF nanocomposites thin films are promising candidates for semiconductor materials used in electronic devices.