Salt Nanocomposites Research Articles

Effect of nanoparticle clusters on the specific heat capacity of a molten carbonate for thermal energy storage

Fused carbonates are promising heat storage materials for next-generation thermal energy storage technologies. Nanocomposite phase change materials (NPCMs) can often improve the thermal performance of a single-phase change material (PCM). In this paper, the effect of nanoparticles (SiO2) on the specific heat capacity (SHC) of molten salt (Na2CO3:K2CO3 = 58:42 mol%) was investigated by molecular dynamics (MD) method, and the intrinsic mechanism of the change of SHC was revealed from a microscopic perspective. The results showed that the SHC first rapidly increased and then gradually decreased with increasing nanoparticle loading. The SHC of the NPCM increased by 0.336 % to 4.299 % with nanoparticle loadings of 0.2–0.8 wt%, and the SHC of the NPCM was as high as 4.299 % with a nanoparticle loading of 0.2 wt%. In addition, Fb is defined in this paper to reflect the effect of the interaction between the nanoparticles and PCM on SHC. The decline in the Fb value with increasing nanoparticle loading indicates that the interaction is enhanced, and enhanced interaction was most clearly observed with a nanoparticle loading of 0.2 wt%. The interaction between nanoparticles and PCM leads to the separation of amorphous carbonate molten cations into different components, and this separation changes the distribution of Ecoul and Elong, which in turn increases the SHC of the NPCM. This work is a key guide for the selection and optimal design of new molten salt nanocomposites.

New insights into the heat capacity enhancement of nano-SiO2 doped alkali metal chloride molten salt for thermal energy storage: A molecular dynamics study

Molten salts and their based nanofluids are important media for heat transfer and thermal energy storage in concentrated solar power (CSP) system. To improve the overall efficiency of the CSP plants, it is important to increase the specific heat capacity of molten salt to the extent possible. Nanomaterials have been doped in molten salt to enhance the specific heat capacity of molten salt; however, the mechanism of enhancement in specific heat capacity caused by doping of nanoparticles in molten salt is still unclear. In this work, the Buckingham force field parameters for alkali metal chloride molten salts (KCl, NaCl, LiCl) were first derived and carefully validated. The specific heat capacities, viscosities, and self-diffusion coefficients of pure molten salts and the specific heat capacities of molten-salt-based nanofluids with SiO2 nanoparticles were investigated by molecular dynamics (MD) simulations. The calculated thermophysical properties of the chloride molten salts using the derived Buckingham potential parameters are in good agreement with the experimental data, and the overall prediction performance is better than that of the BMH potential. Results show that the specific heat capacity of molten salt first increases and then decreases with increasing SiO2 doping ratio, reaching a maximum value at 1 wt%. The specific heat capacities of KCl, NaCl and LiCl nanofluids with 1 wt% SiO2 nanoparticle are increased by 6.2 %, 8.6 % and 19.8 % compared to the base salts, respectively. Number density, radial distribution function, coordination number curves, and energy of the nanofluid system were systematically analyzed. It is found that the increase of the specific heat capacities of the molten salt-based nanofluids can be explained by the energy and coordination number change caused by the number density mismatch of cations and anions. Interestingly, the local delamination of cations around SiO2 nanoparticle surfaces in LiCl-SiO2 nanofluids is clearly observed and visualized for the first time; it is a phenomenon well explained by the analysis of number density and contributes to the further enhancement of the heat capacity. The findings of this work could provide important fundamentals in understanding and designing more efficient molten salt nanocomposites for thermal energy storage in future studies.

Carbon Nanotube/Hygroscopic Salt Nanocomposites with Dual‐Functionality of Effective Cooling and Fire Resistance for Safe and Ultrahigh‐Rate Operation of Practical Lithium‐Ion Batteries

AbstractFire and explosion accidents and reduced energy utilization due to poor cycling stability of lithium‐ion batteries (LIBs) caused by inevitable internal temperature rise during high‐rate operations have become a growing concern. Herein, a dual‐functional carbon nanotube/hygroscopic salt (DFCNT/HS) film with effective passive cooling performance and fire insulation for the safe usage of practical LIBs under extremely fast discharging conditions is reported. The DFCNT/HS film based on the cooling mechanism of self‐adaptive moisture absorption/desorption delivers a high cooling power of 32.9 W m−2 K−1, which can reduce the maximum temperature of a 18650–3.6 V/2.0 Ah LIB by 11.2 and 17.4 °C at discharging rates of 10 and 15 C, respectively. Covering the cooling film, the battery discharges 23.6 Ah more total capacity at 10 within 500 cycles. What is challenging, almost three‐fold extended lifetime of 425 cycles is achieved at 15 C with an extra total capacity of 467.2 Ah. Meanwhile, the developed film also shows an excellent high‐temperature resistance up to 540 °C, which can alleviate the devastating fire propagation. The fast heat dissipation and excellent fire insulation as well as the mechanical flexibility and manufacturing scalability make this new material promising for safe usage of high‐rate LIBs with zero energy consumption.

Facile fabrication of carbon nanotubes-encapsulated cobalt (nickel) salt nanocomposites and their highly efficient catalysis in the thermal degradation of ammonium perchlorate and hexogen

For reducing particle aggregation and improving catalytic activities of metal salts in composite solid propellants, ten cobalt and nickel compounds were encapsulated into the channels of oxidized carbon nanotubes (CNTs) by ultrasonication, which was proven by TEM, SEM, XRD, Raman, XPS, etc. The catalytic performances of the nanocomposites for ammonium perchlorate (AP) and hexogen (RDX) thermal degradation were evaluated by the DSC technique and the results revealed that the composites exhibit significant effects on the thermal decomposition of AP and RDX. Among them, 5 wt. % Co(NO3)2@CNTs(D1) as the catalyst increased the released heat of AP from 746.53 J/g to 2489.26 J/g, higher in catalytic efficiency than CoO@CNTs(D1) (1791.29 J/g), and advanced the peak temperature of AP at the high-temperature decomposition stage from 406.6°C to 312.4°C; while 1 wt. % Ni(NO3)2@CNTs(D1) as an additive enhanced the pyrolytic heat of RDX approximately three times and was more active than that of NiO@CNTs(D1). Kinetic studies showed that the activation energies of AP and RDX were sharply decreased with Co(NO3)2@CNTs(D1) and Ni(NO3)2@CNTs(D1) as additives. In addition, the thermal decomposition mechanism of RDX was studied by TG-FTIR-MS and it was found that the as-prepared nanocomposites promoted the cleavage of the C-N bonds of RDX and the generation of N2O gas.

Comprehensive thermal properties of molten salt nanocomposite materials base on mixed nitrate salts with SiO2/TiO2 nanoparticles for thermal energy storage

The purpose of this investigation is to find and prepare novel heat storage materials to meet the requirement of Concentrating Solar Power (CSP) system. This paper focuses on the formulation, fabrication and characterization of a novel molten salt nanocomposite for high-temperature heat energy storage. The molten salt nanocomposite is based on eutectic quaternary salt, and two different concentrations of SiO 2 and TiO 2 nanoparticles are added to improve its specific heat capacity and thermal conductivity by microwave method. Concerning the material characterization, a suite of techniques was used, including simultaneous thermal analysis (STA) and laser flash analysis (LFA). The consequences demonstrate that the melting point and latent heat of molten salt nanocomposites can be reduced by adding two different concentrations of nanoparticles at the same time. The specific heat is 28.1% higher than that of the pure quaternary salt, and 6.3% and 9.8% higher than that of adding SiO 2 and TiO 2 nanoparticles separately when adding 0.1 wt% SiO 2 and 0.9 wt% TiO 2 nanoparticles to the quaternary nitrate. Compared with pure quaternary salt, the thermal conductivity of the molten salt nanocomposites increased by 53.7%, which was 16.8% and 6.3% higher than that of adding SiO 2 and TiO 2 nanoparticles separately. Upon inspection with scanning electron microscopy, a high-density nanostructure and heat transfer channel were observed, which appear to be the reason for the enhancement of specific heat and thermal conductivity of the material. Finally, the molten salt nanocomposite has a broad application prospects in high-temperature thermal storage system. • Novel molten salt nanocomposite is prepared by microwave method for heat storage system. • Two different concentrations of nanoparticles are added to the salt simultaneously. • The specific heat and thermal conductivity of quaternary salt are improved. • The concentration of nanoparticles can affect the thermal properties of molten salt. • The honeycomb structure is the reason for the increase of thermal performance.

Innovative and cost-effective nanodiamond based molten salt nanocomposite as efficient heat transfer fluid and thermal energy storage media

Novel and efficient molten salt nanocomposites as heat transfer nano-fluids and thermal energy storage materials have been developed. Cost-effective detonation nanodiamonds (NDs) of an average particle size of 10 nm were uniformly dispersed in binary nitrate molten salt using the ultrasonication process to achieve well dispersion of NDs. NDs mass loadings were varied and optimized, furthermore, the optimized mass loading of NDs was dispersed using solid state method for comparison. The thermo-physical properties of the developed ND-molten salt nanocomposites were studied in terms of melting point temperature, thermal stability temperature, thermal conductivity, volume heat capacity and thermal diffusivity and were enhanced in terms of their applications as heat transfer nano-fluids and thermal energy storage media. Therefore, melting point was reduced by 16 °C and the thermal stability was improved by 35 °C displayed enhanced temperature range compared to base binary molten salt. On other hand, the thermal conductivity and volume heat capacity were significantly improved achieving enhancement by 93 and 38% respectively, compared to base binary molten salt. Furthermore, the thermal diffusivity of developed ND based molten salt was enhanced by 43% compared to blank molten salt recorded superior values among reported nano-fluids. The surface morphology and dispersion of NDs in binary nitrate molten salt was studied and visualized using SEM and TEM.

Study on preparation and thermophysical characteristics of molten salt nanocomposite by microwave method

Molten salts are widely applied as heat transfer and thermal storage medium for solar thermal power. In order to research the effect of preparation conditions and the types of nanoparticles on the thermophysical properties of molten salt nanocomposite, different molten salt nanocomposites were developed by mixing the nitrates (Ca (NO3)2·4H2O–KNO3–NaNO3–NaNO2) with 1.0 wt% of SiO2, MgO, TiO2 and CuO nanoparticles using a microwave method, which was a new preparation process of molten salt nanocomposite based on high temperature mixing without water. The effect of different microwave heating temperature (250, 350 and 450 °C) and heating time (30, 60, 90 and 120 min) were experimentally studied. The melting point, latent heat and specific heat of the samples were analyzed by differential scanning calorimeter (DSC). The morphology was observed by scanning electron microscope (SEM). The results showed that the nanoparticles induced a decrease of the melting point of 0.1–2.4% while the latent heat decreased by 3.3–7.9%. Compared with other molten salt nanocomposites, the molten salt with the addition of SiO2 nanoparticles had the biggest increase in specific heat, which increased by 7.7% in solid state and 21.0% in liquid state after heating for 90 min at 250 °C. The total heat storage density could reach to 783.0 J/g between 30 and 500 °C, which was 13.3% higher than the base salt. In addition, according to the morphology of the samples, network nanostructures were observed in the molten salt nanocomposite doped with SiO2.

Nanoscale Calcium Salt-Based Formulations As Potential Therapeutics for Osteoporosis.

Osteoporosis causes severe bone damage, posing potential risks to human health, patient quality of life, and society. Calcium has been widely shown to enhance bone density and prevent osteoporosis-related bone fractures. Here, we focused on calcium salt formulations containing natural substances and their possible therapeutic effects on osteoporosis. In particular, we developed a nanoscale calcium salt of natural origin and formulated nanocomposite tablets supplemented with vitamin D (Vit D), herb Rhodiola rosea (R. rosea) and natural mineral Shilajit that are known to be antiosteoporotic. The calcium salt nanocomposites exhibited no toxicity, and particularly the formulation containing R. rosea stimulated osteogenic differentiation. The calcium salt nanocomposites inhibited osteoclastic activity, including RANKL expression, as shown by a decrease in tartrate-resistant acid phosphatase (TRAP)-positive cells. When administered orally to osteoporotic rats for 45 days, the calcium salt nanocomposites reduced bone resorption, as evidenced by the significantly higher bone volume and density, increase in osteoblasts and decrease in osteoclasts compared to those in nontreated control rats. Systemic administration of the nanocomposites caused no severe stomach toxicity or damage over the test period, during which no renal stone growth was observed. On the basis of their significant bilateral effects in stimulating osteoblasts and inhibiting osteoclasts and the resultant efficacy in an osteoporotic model, the nanocomposite tablets composed of a calcium salt and natural products can be considered novel nanotherapeutics for osteoporosis treatment.

Lowered total solidification time and increased discharge rate of reduced graphene oxide-solar salt composites: Potential for deployment in latent heat thermal energy storage system

Solar salt is a useful energy storage medium and a heat transfer fluid for concentrated solar thermal applications. The present work explores the use of reduced graphene oxide (rGO) nanostructures as an additive to solar salt, to improve its thermophysical properties. Reduced graphene oxide nanostructures at weight fractions of 0.125 wt% and 0.5 wt% were added to the solar salt, leading to rGO-solar salt composites. The thermophysical characterization experiments revealed that the specific heat in the 0.5 wt% rGO-solar salt nanocomposite was elevated by 6% over the temperature range of 50–270 °C. The time required for complete solidification of 0.125 wt% and 0.5 wt% was reduced by 43% and 49%. In the discharge cycle, the heat transfer rate was amplified by 90% and 138% respectively for 0.125 wt% and 0.5 wt% rGO-solar salt nanocomposites, attributable to thermal conductivity enhancement, specific heat augmentation and heterogeneous nucleation. Thus, rGO-solar salt composites are suitable for use as latent heat thermal energy storage medium in solar thermal applications.

Rheological Characteristics of Molten Salt Seeded with Al2O3 Nanopowder and Graphene for Concentrated Solar Power

HITEC salt (NaNO2-NaO3-KNO3) and solar salt (NaO3-KNO3) are typical molten salts used in concentrated solar power. Adding nanoparticles is an effective method to improve the thermo-physical properties of pure salt. It is indispensable to experimentally study the rheological behaviours of salt seeded with nanoparticles, which can increase the specific heat capacity of pure salt. In this work, the viscosities of HITEC salt were measured with different shear rates in the temperature range of 200 °C to 450 °C firstly, while those of solar salt were measured in the temperature range of 250 °C to 500 °C. The experimental data showed reasonable agreement with the literature correlations, which verify the Newtonian behaviours of pure salts. The evolutions of the viscosities of nanocomposites in the same temperature range were measured and analysed, where the nanocomposites were synthesized with 1 wt.% or 2 wt.% Al2O3 nanopowder and graphene, respectively. Results showed that the addition of Al2O3 nanopowder had relatively little effect on viscosity, and the variations were about −35.4%~8.1% for the HITEC salt nanocomposites and −9.2%~68.1% for the solar salt nanocomposites. While graphene would apparently increase the viscosities of HITEC salt and solar salt, HITEC salt with the addition of graphene showed slight non-Newtonian fluid behaviour.

Effect of SiO2 nanoparticles on specific heat capacity of low-melting-point eutectic quaternary nitrate salt

In order to evaluate the effect of nanoparticles on the specific heat capacity of a low-melting-point eutectic quaternary nitrate salt, 1.0 wt% SiO2 nanoparticles with an average size of 20 nm was doped into the mixed salt Ca(NO3)2·4H2O-KNO3-NaNO3-LiNO3. A mechanical dispersion mixer was developed to prepare molten salt nanofluids. The effects of the mixing time (15, 45, 90, 120, and 150 min) and stirring rate (600, 750, and 1000 rpm) on the specific heat capacity of the nanofluids were analyzed using a differential scanning calorimeter. The results showed that the specific heat capacity of the nanofluids varied with the mixing time and stirring rate. It increased by ~ 17.0% at a mixing time of 15 min and stirring rate of 750 rpm. Microstructural characterization of the molten salt nanocomposites was performed using scanning electron microscopy, which showed that special nanostructures, which resemble chain-like nanostructures, were formed on the surface of the solid nanofluids. The special nanostructures with a large specific surface area and high surface energy could increase the specific heat capacity of the molten salt nanofluids.

Synthesis of phenols by using aryldiazonium silica sulfate nanocomposites

The hydrolysis of a new type of diazonium salt immobilized on the surface of silica sulfuric acid was studied in this work. By using diazonium salt nanocomposites, a number of phenol derivatives were synthesized in good yields. In contrast to the previous works, the present procedure was conveniently carried out under mild and solvent-free conditions. The effects of solvent and temperature were studied on the dediazoniation products. The notable advantages of this methodology were operational simplicity, availability of reactants, short reaction time and easy work-up.

Controlled release and long-term antibacterial activity of reduced graphene oxide/quaternary ammonium salt nanocomposites prepared by non-covalent modification

In order to control the long-term antibacterial property of quaternary ammonium salts, dodecyl dimethyl benzyl ammonium chloride (rGO-1227) and rGO-bromohexadecyl pyridine (rGO-CPB) were self-assembled on surfaces of reduced graphene oxide (rGO) via π-π interactions. The obtained rGO-1227 and rGO-CPB nanocompounds were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM).The antibacterial activities were evaluated on Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Both rGO-CPB and rGO-1227 reduced the cytotoxicity of the pure antimicrobial agents and presented strong antimicrobial properties. Especially, CPB could be loaded efficiently on the surface of rGO via π-π conjugate effect, which resulted in a nanocomposite presenting a long-term antibacterial capability due to the more important quantity of free π electrons compared to that of 1227. When comparing the advantages of both prepared nanocomposites, rGO-CPB displayed a better specific-targeting capability and a longer-term antibacterial property.

Well-designed sandwich-like structured graphene/emeraldine salts prepared by inverse microemulsion polymerization with particle-on-sheet and sheet-on-sheet morphologies

In this work, nanocomposites with well-designed sheet-on-sheet and particle-on-sheet structures consisting of emeraldine salt and graphene were prepared via in situ inverse microemulsion of aniline monomers by well-dispersed graphene as efficient template. Influences of the weight percentage of graphene on the morphology and electrical conductivity property of the resulting sandwich-like structures were discussed. All the materials were characterized by XRD, FTIR, DSC, Raman and UV–Vis spectroscopy techniques. The formation of emeraldine salt (ES) shell layer on the exterior of graphene was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The thermal stability, electrical conductivity and electrochemical property of the graphene/emeraldine salt nanocomposites were examined by thermogravimetric analysis (TGA), conventional four-probe method and cyclic voltammetry, respectively. In comparison with the pure emeraldine salt, the graphene/emeraldine salt sandwich-like structures showed enhanced electric conductivity, thermal stability and electrochemical property. A high specific capacitance of 1,615.42 F/g was obtained for graphene/emeraldine salt nanocomposites with sheet-on-sheet morphology at scan rate 5 mV/s which is superior to any studied graphene/emeraldine salt composites, up to now. Improvement in these properties is arisen from the fact that the π-bonded surface of the graphene sheet interacts strongly with the conjugated structure of the emeraldine salt sheet and increases relative amounts of quinoid rings to benzoid rings in sandwich-like structure of graphene/emeraldine salt nanocomposite.

A Study of Thermal Stability and Electromaganetic Shielding Behavior of Polyaniline-P-Toluene Sulfonic Acid/Montmorillonite Nanocomposites

Intrinsically conductive polymer-Polyaniline had high conductivity and many other properties, such as environmental stability and rather simple synthesis. In addition, doping with organic acids could enhance its processing, so it had wide range of applications, such as solar cells, antistatic and electromagnetic interference shielding. In this study, the organic amine 1-Dodecylamine (DOA) modification of sodium montmorillonite (NA+-MMT), and conducting polymer / layered silicate salt nanocomposites (PANI-PTSA/DOA-MMT) had been prepared by doping aniline with organic acid (PTSA), then added organic clay. The thermal, electrical properties and EMI effects of nanocomposites had discussed by XRD, TEM, EMI, TGA analysis, conduction measure and EMI tested. The results indicated the organo-clay interlayer distance expanded from 1.29 to 1.8 nm, and DOA-MMT dispersed in the material, that formed an exfoliated nanocomposite. The thermal stability of nanocomposites depended on content of DOA-MMT, material had the better thermal stability when DOA-MMT load was 5 wt. %. The nanocomposites had the best conductivity when DOA-MMT load was 1 wt. % as well as the electromagnetic shielding effectiveness was increase with increase in conductivity. In addition, the electromagnetic shielding of nanocomposites also depended on thickness and frequency of electromagnetic wave, the electromagnetic shielding was increased with increase in thickness and frequency.

ChemInform Abstract: Synthesis and Thermal Stability of Cubic ZnO in the Salt Nanocomposites.

AbstractMetastable cubic ZnO is synthesized from monodispersed nanoparticles of wurtzite ZnO in the presence of NaCl under a pressure of 7.7 GPa (700—900 K, 15 min).

Synthesis and thermal stability of cubic ZnO in the salt nanocomposites

Cubic zinc oxide (rs-ZnO), metastable under normal conditions, was synthesized from the wurtzite modification (w-ZnO) at 7.7 GPa and ∼800 K in the form of nanoparticles isolated in the NaCl matrix. The phase transition rs-ZnO → w-ZnO in nanocrystalline zinc oxide under ambient pressure was experimentally studied for the first time by using differential scanning calorimetry and high-temperature X-ray diffraction analysis. It was shown that the transition occurs in the temperature range from 370 to 430 K and its enthalpy at 400 K is −10.2 ± 0.5 kJ mol−1.