Magnesium Nitrate Hexahydrate Research Articles

Understanding the Roles of Excipients in Moisture Management in Solid Dosage Forms.

Excipients are ubiquitous in pharmaceutical products, and often, they can also play a critical role in maintaining product quality. For a product containing a moisture-sensitive drug, moisture can be deleterious to the product stability during storage. Therefore, using excipients that interact with moisture in situ can potentially alleviate product stability issues. In this study, the interactive behavior of starch with moisture was augmented by coprocessing maize starch with sodium chloride (NaCl) or magnesium nitrate hexahydrate [Mg(NO3)2·6H2O] at different concentrations (5 and 10%, w/w). The effect of the formulation on drug stability was assessed through the degradation of acetylsalicylic acid, which was used as the model drug. The results showed that coprocessing of the starch with either NaCl or Mg(NO3)2·6H2O impacted the number of water molecule binding sites on the starch and how the sorbed moisture was distributed. The coprocessed excipients also resulted in lower drug degradation and lesser changes in tablet tensile strength during post-compaction storage. However, corresponding tablet formulations containing physical mixtures of starch and salts did not yield promising outcomes. This study demonstrated the advantageous concomitant use of common excipients by coprocessing to synergistically mitigate the adverse effects of moisture and promote product stability when formulating a moisture-sensitive drug. In addition, the findings could help to improve the understanding of moisture-excipient interactions and allow for the judicious choice of excipients when designing formulations containing moisture-sensitive drugs.

Influence of fuel-to-oxidizer ratio, potential of hydrogen and annealing temperature on the structural and optical properties of nanocrystalline MgO powders synthesized by the hydrothermal method

Nanocrystalline magnesium oxide powders (MgO) were prepared using a hydrothermal method. In various fuel-to-oxidizer ratios (F/O) and precursor solutions with pH levels from 8 to 12, magnesium nitrate hexahydrate Mg(NO3)2 was utilized as an oxidizer and polyvinyl alcohol (PVA) as a fuel. To improve crystallinity and phase purity, these materials were annealed for two hours at varied temperatures. XRD, FTIR, EDS, FESEM and DRS were used to study the MgO nanopowders’ structure, vibration, elemental and optical properties. The fuel-to-oxidizer ratios, annealing temperatures and pH values greatly affected the samples’ properties. The synthesized powders had a particle size distribution in the range of 18–49 nm. The XRD results showed that the crystallite percent of the MgO phase grew with an increase in the F/O from 0.5 to 0.75, and then, it decreased at F/O = 1. The maximum percent of crystallites was observed at pH = 8. By increasing the annealing temperatures, the crystallite size of the samples increased from 22.82 nm to 49.06 nm, while the specific surface area and dislocation density decreased from 20.59 m2/g to 7.83 m2/g and 0.0006 nm−2 to 0.0001 nm−2, respectively. FTIR spectra results indicated that the MgO band peaking at (418–688 cm−1) was high at pH value 8, then it reduced at pH 10 and finally, this peak had the smallest size at pH = 12. Further confirmation of MgO presence and its homogeneity in the final product was approved through EDS measurements. DRS spectra were used to obtain energy gap using Kubelka–Munk relation and noticed in the range of 5.72–5.89 eV for MgO NPs.

Development And Characterization of Magnesium Ion Conducting Biopolymer Electrolyte Using Agar and Magnesium Nitrate Hexa Hydrate

The aim of the study was to develop an agar-based biopolymer electrolyte with varying concentrations of Mg(NO3)2.6H2O in double-distilled water as the solvent. To better understand the impact each concentration had on the biopolymer, a range of characterisation techniques were employed - XRD, FTIR, DSC, Ac impedance analysis and transference number measurement being amongst them. XRD was used to determine whether a crystalline or amorphous polymer resulted from the process. Agar and magnesium nitrate may form complexes, according to FTIR. Through the process of differential scanning calorimetery, researchers have pinpointed the glass transition temperatures for a biopolymer electrolyte with superior conductivity. In order to study its performance, a Mg2+ ion primary battery was built using a biopolymer membrane with a highest ionic conducting of 1.74 x 10-4 S cm-1. This electrolyte was comprised of 40% agar and 60% magnesium nitrate in water, and its ionic transference number of Mg2+ had been determined at 0.30 via Evan's methodology.

Utilization of Activated Carbon/Magnesium(II) Composites in Decreasing Organic Materials

<div><table cellspacing="0" cellpadding="0" align="center"><tbody><tr><td align="left" valign="top"><p>This study aimed to determine the characteristics, adsorption capacity, and isotherm of the adsorbent AC/Mg(II) composite in decreasing organic matter in peat water. Activated carbon was produced from empty fruit bunches of oil palm containing high levels of lignocellulose. Carbon was synthesized through the carbonization process and then activated with CH<sub>3</sub>COONa. The activated sample was composited with magnesium nitrate hexahydrate through an in-situ method under alkaline conditions using NaOH. The adsorbent AC/Mg(II) composite that had been prepared was characterized using FTIR, showing the presence of Mg-O bonds at the absorption wave number of 403.12 cm<sup>-1</sup>. The results showed that the moisture content of the adsorbent was lower compared to activated carbon, namely 1.30%. Furthermore, the best mass was 2 g AC/Mg(II) with an adsorption of 2.26 mg/g and an organic matter adsorption percentage of 14.41%. Furthermore, the optimum contact time was 15 minutes with an adsorption of 2.42 mg/g and a percentage of 17.15%. The mechanism occurring in the AC/Mg(II) composite with peat water organic matter followed the Langmuir isotherm equation, which formed a monolayer. The equation gave R<sup>2</sup>, adsorption capacity (Qo), and adsorption constant (k) values of 0.9994, 0.2340 mg/g, and 0.0047, respectively.</p></td></tr></tbody></table></div>

Impact of tetra ethyl ortho-silicate and magnesium nitrate hexahydrate on dielectric characteristics of forsterite powder

Forsterite powder with different compositions of tetra ethyl ortho-silicate (TEOS) and magnesium nitrate hexahydrate (MNH) is synthesized using the sol-gel method. X-ray Diffraction (XRD) technique is used for structural analysis and phase identification for forsterite powder. Surface morphology and elemental composition of forsterite samples are also investigated using scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) techniques. In addition, an extensive study is performed to estimate the dielectric properties (dielectric constant, dielectric loss, alternating current conductivity and loss tangent) and their relationship with frequency at room temperature in the frequency range of 200 MHz–20 GHz using a vector network analyzer (VNA) assembly. Furthermore, the intense effect of TEOS and MNH on surface morphology and dielectric properties of forsterite powder is also discussed in detail by focusing on the application in medical implants.

Characterization and mechanisms of the phase's formation evolution in sol-gel derived mullite/cordierite composite

In this work, mullite/cordierite precursor powder was prepared through a technology of low-temperature synthesis by using the sol-gel process, tetraethyl orthosilicate (TEOS) as a source of silicon oxide SiO2, and aluminum nitrate nonahydrate Al (NO3)3.9H2O as a source of aluminum oxide (Al2O3) and magnesium nitrate hexahydrate Mg (NO3)2.6H2O as a source of magnesium oxide MgO was used as raw materials to synthesize mullite/cordierite precursor gel with a concentration (sample containing 50 wt% of cordierite and 50 wt% of mullite) and named as (MC50). The objective of this study is to find a suitable kinetic model to study the phases and the mechanisms of their formation in mixtures, with the prediction of the system's behavior under selected thermal conditions, including finding the kinetic and thermodynamic media that describe these interactions. To follow and characterize the crystalline phases and their transformation as a function of temperature utilizing differential thermal analysis (DTA), Dilatometry (DIL), and powder X-ray diffraction (XRD). The results show that the crystallization process occurred in the temperature interval between (900–1350) °C. In the temperature range of (900–1000) °C, spinels between Al–Si and Al–Mg with the chemical formulas (Al4Si3O12 and MgAl2O4) were formed. When the thermal treatment temperature increases from (1000–1100) °C, mullite is produced. As the temperature increases, the amount of Mg–Al spinel decreases to form amorphous silica, and μ-cordierite has appeared at 1250 °C. With an increase in temperature up to 1350 °C, α-cordierite appeared as a stable phase. The reason for this is the presence of the spinel (Al–Mg) phase that helped it form.To determine the reaction kinetics of these transformations at high temperatures, the mixture 50/50 mullite/cordierite was selected to study its kinetics. The activation energy values (Ea/Tm) (Tm is the maximum temperature of the transformation, i.e., the maximum peak temperature is not related to the crystallization fraction α) calculated by Ozawa, Boswell, and Kissinger methods are in good agreement with the evident activation energy (Eα/Tα) (Tα is the degree of the heat of transformation in terms of crystallization fraction α changes from 0<α < 1) calculated using the KAS and FWO methods.For the purpose of calculating the interaction model and finding the media that determine the interaction model based on the experimental data, Malék's methodology method was used. The best kinetic model is the Šesták - Berggren model to describe the reaction process to form spinel, mullite, and α-cordierite. From the SB model, the equations Kinetics and all kinetic parameters (n, m, ln(k0)) that describe the kinetics of the reactions and mechanisms of formation of spinel, mullite, and α-cordierite in the mixture are, respectively, (2.14, 0.023, 65.21), (1.62, 0.1232, 81.76), and (1.41, 0.2859, 91.13). While the values of Gibbs free energy ΔG#, enthalpy ΔH#, and entropy ΔS# were as follows: 407.254 kJ mol−1, 976.756 kJ mol−1 and 415.561 J mol−1K−1 for Mullite formation, and 471.64 kJ mol−1, 1255.16 kJ.mol-1 and 491.75 J mol−1K−1 for the formation of α-cordierite.Comparison of simulation curves with experimental data obtained at different temperatures gives good agreement with the thermal analysis data (Experimental), which indicates that the Model of Šestak − Berggren, is the best suitable kinetic model for studying and describing the reaction technique for MC50 prepared by the sol-gel method.

Anti‐corrosion improvement of epoxy coating by the synergistic effect of barrier shielding and slow‐release based on phytic acid intercalated hydrotalcite

AbstractEpoxy resin has been widely applied in coating preparation, due to its excellent properties. The anti‐corrosion performance improvement of epoxy‐based coatings has attracted much attention. The synergistic effect of the barrier function of two‐dimensional fillers and the slow release of inhibiter has been proven to be an effective way to improve the anti‐corrosion of coatings. In this work, the phytic acid (PA) intercalated hydrotalcite (HT) was fabricated by a one‐pot method. First, HT was synthesized by magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) and aluminum nitrate nonahydrate (Al(NO3)3·9H2O) in the water solution. Subsequently, PA was added to the dispersion to obtain PA intercalated HT fillers (PA‐HT). The obtained PA‐HT fillers were incorporated into the epoxy resin (EP) to prepare the anti‐corrosion coating (PA‐HT/EP). The prepared PA‐HT/EP coating exhibits excellent anti‐corrosion properties at 1 wt% filler loading that the impedance modulus maintains above 109 Ω cm2 after 30 days of soaking in 3.5 wt% NaCl solution. Moreover, the anti‐corrosion mechanism of the synergy of the physical barrier of two‐dimensional fillers and the release slow of inhibitors was thoroughly discussed, particularly the formation and anti‐corrosion mechanism of the passivation protection film constituted by PA.

The application of magnesium nitrate hexahydrate/hybrid carbon material phase change composites in solar thermal storage

AbstractBackgroundIn this study, a series of phase change composites were developed. Phase change materials (PCMs) are substances with a high heat of fusion, thereby possessing great potential for solar thermal storage. However, their disadvantages, such as low thermal conductivity, phase separation, and supercooling, limit their further applications.ObjectiveIn this study, magnesium nitrate hexahydrate (MNH) was used as the phase change material, and different proportions of photothermal materials were added to improve the thermally conductive property and solar thermal storage efficiency of MNH.MethodsThis study used magnesium nitrate hexahydrate (MNH) as the substrate. In addition, different proportions of photothermal materials (carbon nanotubes, nano‐graphite, graphene, and partially reduced graphene oxide) were added to promote the efficiency of thermal energy storage. Additionally, a fixed ratio of carboxy methyl cellulose (CMC) was added. The phase change temperature and enthalpy change of the phase change material samples were explored and analyzed by differential scanning calorimeter (DSC). In addition, the thermophysical properties, photothermal storage performance, and thermal reliability analysis of the samples were investigated.ResultsThe results showed that the PCM composites prepared with nano‐graphite have higher latent heat and longer time of phase change. However, the composites prepared with carbon nanotubes (CNTs) have lower latent heat and a shorter time of phase change. Therefore, the partially reduced graphite oxide (PRGO)‐containing composites can retain the latent heat storage capacity of nano‐graphite and decrease the time of phase change, thereby improving the photothermal storage efficiency. The results reveal that the solar thermal storage efficiency of the composite with both CNTs and PRGO could reach up to 0.716.ConclusionsMCGOT‐1 and MCGOT‐2 have high latent heat values, and the phase transition time is short. Therefore, the thermal energy storage efficiency can be as high as 0.716. In addition, compared with related literature, the photothermal storage efficiency of MCGOT‐2 increased by about 2 times. Therefore, the environmentally friendly composites developed in this study have a high potential to be used in solar energy storage and energy‐saving systems.

Dielectric Performance of Forsterite-Coated Titanium Substrate-Based Medical Implant

Forsterite solutions with variable concentrations of tetra ethyl ortho-silicate (TEOS) and magnesium nitrate hexahydrate (MNH) are prepared using the sol-gel method. The dip coating method is applied to coat forsterite solution on a titanium (Ti) substrate. Forsterite coated Ti substrates are subjected to structural analysis and phase identification using the X-ray Diffraction (XRD) technique. Surface morphology and elemental composition of coated Ti substrates are also investigated using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques. An extensive study is also conducted with the help of a vector network analyzer (VNA) assembly to determine the dielectric properties (dielectric constant, dielectric loss, alternating current conductivity, and loss tangent) and their relationship with frequency at room temperature in the frequency range of 200 MHz - 20 GHz. Furthermore, focusing on their use in medical implants, the impact of TEOS and MNH on the surface morphology and dielectric characteristics of forsterite coated Ti substrate is also examined in detail. Results proved that forsterite coated Ti substrate with a higher composition of TEOS and MNH performs better than others.

Water Activity Prediction and Moisture Absorption Isotherms in Plant Food Preservation

The fraction of the water content in a meal (P) to the humidity of pure water is used to represent water activities (aw) (P0). It foretells if water would likely transfer from the packaged food into any potential microorganisms' cells. aw= P/P0. The difference in between vapour temperature of the meal when it is in perfect equilibrium with the air waves around it and the vapour pressure of distilled water in the same circumstances is the food's moisture activities (aw). SPSS statistics is a lithium chloride monohydrate, Potassium acetate, Magnesium nitrate hexahydrate, Sodium chloride, Cadmium Chloride, Potassium Chromate, Lithium sulfate, Sodium hydrogen phosphate, potassium sulfate. The Cronbach's Alpha Reliability result. The overall Cronbach's Alpha value for the model is 0.424 which Indicates 40 % reliability. From the literature review, the above 40% Cronbach's Alpha value model can be Considered for analysis. the outcome of Cronbach's alpha reliability Models is of total cranberry Alpha score is 0.424, which Denotes a 40% dependability level. The 40% Cronbach's Alpha value model mentioned above from the literature Review may be used for analysis.

Parametric analysis of the coating thickness development of electrophoretically deposited carbon nanotube coatings

In this study, the coating thickness evolution of pristine and oxidized carbon nanotubes (CNT) on stainless steel substrates is investigated. Potentiostatic electrophoretic deposition (EPD) is used as a coating technique with two different additives, triethylamine (TEA) and magnesium nitrate hexahydrate (Mg-Nit). Moreover, the depositions are conducted at different voltages (50, 100 and 150 V). Confocal laser scanning microscopy is used to determine the thickness of the CNT depositions after 1, 2, 5, 10, 20 and 30 min. Furthermore, the ability of Hamaker's law to accurately predict coating thickness development is investigated for the thickness evolution on stainless steel. Independent of the additive, the results show that higher voltages lead to increased deposition rates. Comparing the two additives, Mg-Nit generally allows for a higher CNT deposition rate than TEA and forms thicker layers. Coating thickness development can be approximated as linear during the initial 5 min with Mg-Nit and during the initial 20 min with TEA. Finally, Hamaker's law allows for a fairly accurate approximation for the thickness development of CNT coatings with TEA on stainless steel.

Preparation and properties of nano-MgO/HDTMS super hydrophobic multifunctional cotton

First, nano-sized magnesium oxide (MgO) particles were prepared with magnesium nitrate hexahydrate as raw material and plant extract Angelica dahurica as a protective agent and dispersant. Then, MgO nano particles (MgO NPs) were loaded on the cotton fabric surface by dipping method. Finally, using hexadecyl trimethoxysilane (HDTMS) as a modifier and ammonia as a catalyst, the cotton fabric was hydrophobically modified to prepare a super hydrophobic multifunctional cotton fabric. FTIR indicated that long carbon chain silane was successfully introduced onto cotton fabric. SEM and XRD analysis showed that the micro-nano rough structure was formed on the MgO/HDTMS/cotton fabric surface, and its crystal structure was unchanged. The water contact angle of cotton fabric modified by MgO/HDTMS reached 153°, which made it super hydrophobic. Moreover, MgO/HDTMS/cotton fabric has excellent antibacterial properties with the antibacterial rates against S. aureus and E. coli of 95.50% and 95.30%, respectively. After 10 times of cyclic washing, both the water contact angle and the antibacterial rate for S. aureus and E. coli of the fabric showed a slight decrease, which indicated that it has good washing durability.

Influence of Bath pH values on the Structural and Optical Properties of Electrodeposited MgO Thin Films for Optoelectronic applications

This paper investigates the influence of bath pH values on the structural and optical properties of magnesium oxide (MgO) thin films synthesized using electrodeposition technique. The films were deposited on conductive fluorine tin oxide (FTO) substrates using magnesium nitrate hexahydrate as a precursor material. The structural, morphological and optical properties of the electrodeposited films were examined by scanning electron microscopy (SEM), X-ray diffraction and UV-Vis spectrophotometer. The morphology and optical properties of the films were found to vary with bath pH values. The band gap decreased as the bath pH values increased. The deposited MgO films exhibited average transmittance of 80%, 50%, and 25% with thicknesses 400 nm, 480 nm, and 540 nm for bath pH values of 2.0, 5.0, and 9.0, respectively. The results obtained indicate that bath pH values play significant role in the formation of MgO films and can be used to tune the material into useful optoelectronic applications.

A novel hydrated salt-based phase change material for medium- and low-thermal energy storage

Magnesium nitrate hexahydrate (MNH) was considered as a promising medium- and low-temperature phase change material (PCM) owing to high latent heat, weak corrosion, and low price. While supercooling performance greatly restricted the application of such PCM. In this work, MNH-based composite PCM containing a novel nucleating agent was prepared. Supercooling behavior and thermophysical properties of composites were analyzed. Additionally, thermal performance of composites in a fin-plate heat storage unit was investigated. Results showed that 2 wt% magnesium sulfate heptahydrate (MSH) effectively suppressed supercooling performance and was chemically compatible with MNH. Composites containing 2 wt% MSH and 2 wt% sodium carboxymethyl cellulose (CMC) performed favorable thermal properties, including supercooling degree of 0.6 °C, phase change temperature of 89 °C, latent heat of 166.88 J/g, and heat storage density of 220.78 J/g. Effective working temperature of the composite should be no more than 140 °C. Magnesium sulfate tetrahydrate (MST) was actually the real component in MSH that inhibited the supercooling of MNH. Compared with paraffin, encapsulated MNH-based composite PCM with a 6720 kJ higher heat storage capacity possessed a much shorter charging/discharging time due to the higher thermal conductivity. The results might provide a foundation for the practical application of MNH.

Experimental study on phase change heat storage of valley electricity and economic evaluation of commercial building heating

• A composite PCM of Mg (NO 3 ) 2 6H 2 O/NaNO 3 for an electric boiler was developed. • A modular PCHS unit was constructed and tested, showing stable heating performance. • The heating tests in commercial buildings show 53% savings in operating costs. • The valley power PCHS heating technology shows good application prospects. The application of valley power phase change heat storage (PCHS) in commercial building heating has practical significance for the city's sustainable development. In this study, the experimental study on valley power PCHS is carried out, focusing on the winter heating of a commercial building. An inorganic hydrated salt phase change material (PCM) of magnesium nitrate hexahydrate and sodium nitrate (mass ratio, 92:8) with a phase change temperature of 80–83 °C for an electric boiler was developed. A modular PCHS unit was constructed and tested for 2.5 months from 2018 to 2019 and 4.5 months from 2020 to 2021. The results show that the PCM is stable at about 81 °C after 240 cycles. Moreover, the heat storage and the exothermic power of the PCHS unit reached 10.95 kW and 10.15 kW in the 9-hour test, respectively. The 12-day trial of an office shows that the indoor temperature was maintained at 22–24 °C stably during the daytime working hours (7:00–17:00). Furthermore, the two-year test of the building heating shows that the valley power PCHS can effectively adapt to the outdoor environment changes. The power consumption of the PCHS unit has a negative linear correlation with the ambient temperature. In addition, the operating cost of the PCHS unit system is only 3.5 RMB/month/m 2 , which is less than half of the municipal central heating system cost of 7.5 RMB/month/m 2 , reflecting good economy, and the advantages of energy-saving, emission reduction, and environmental benefits are obvious. The findings of this study provide a valuable supplement for the heating mode and low-carbon energy utilization of urban buildings.

Encapsulation of hygroscopic liquids via polymer precipitation in non-aqueous emulsions

HypothesisEncapsulation of ionic liquids (ILs) and phase change materials (PCMs) can overcome limitations associated with bulk materials, e.g., slow mass transfer rates, high viscosities, or susceptibility to external environment. Single step soft-templated encapsulation methods commonly use interfacial polymerization for shell formation, with a multifunctional monomer in the continuous phase and another in the discontinuous phase, and thus do not give pristine core material. We posit that polymer precipitation onto emulsion droplets in non-aqueous emulsions could produce a robust shell without contamination of the core, ideal for the encapsulation of water-sensitive or water-miscible materials. ExperimentsSolutions of commodity polymers were added to the continuous phase of non-aqueous Pickering emulsions stabilized by alkylated graphene oxide (GO) nanosheets such that the change in solubility of the polymer led to formation of robust shells and the production of capsules that could be isolated. FindingsWe demonstrate that a polymer precipitation approach can produce capsules with pristine core of the IL 1-ethyl-3-methylimidazolium hexafluorophosphate [Emim][PF6] or the salt hydrate PCM magnesium nitrate hexahydrate (MNH) and shell of nanosheets and polystyrene, poly(methyl methacrylate), or polyethylene. The capsules are approximately 80 wt% [Emim][PF6] or >90 wt% MNH, and the core can undergo multiple cycles of solidification and melting without leakage or destruction. This novel, single-step methodology provides a distinct advantage to access capsules with pristine core composition and is amenable to different core and shell, paving the way for tailoring capsule composition for desired applications.

A Wide Bandgap Semiconducting Magnesium Hydrogel: Moisture Harvest, Iodine Sequestration, and Resistive Switching.

Water harvesting from the ubiquitous moisture is pivotal for delivering fresh water to earth's arid/semiarid regions, and sequestration of iodine from the solution is crucial for environmental safety due to its severe effect on human metabolic processes. In this context, herein, a multifunctional supramolecular metallohydrogel (Mg@TAEA) is synthesized through direct mixing of magnesium nitrate hexahydrate and the low molecular weight gelator tris(2-aminoethyl)amine. Electron microscopy reveals that Mg@TAEA is sculptured in vertically grown well-oriented micrometer-sized flakes. The porous crystalline material (52 m2/g) was found to be an efficacious host matrix for water harvesting from moisture (847 mg/g). Mg@TAEA shows effective (513 mg/g) iodine sequestration from solution and adsorption of carbon dioxide (15 mg/g). The wide bandgap semiconducting Mg@TAEA (3.6 eV) material is a potential candidate for building memory devices, and the Ion/Ioff ratio of the device based on the indium tin oxide (ITO)/Mg@TAEA/Ag heterostructure was found to be ∼62. We further extended our work by analyzing the charge transport properties of the system and found space charge limited conduction (SCLC) and trap-filled SCLC to be responsible for the nonlinear transport behavior observed in the device.

Transparent magnesium aluminate spinel ceramics obtained by one-step spark plasma reaction sintering of a sol-gel precursor powder

Transparent magnesium aluminate spinel (MAS) was obtained by one-step spark plasma reaction-sintering (SPRS) of a nanosized sol-gel powder. The sol-gel powder was processed to obtain three powders as precursors materials with different characteristics. The first powder (HT0) was the as-synthesized sol-gel powder, comprising poorly crystallized boehmite and residual magnesium nitrate hexahydrate. The second powder (HT450) was obtained by calcination of the sol-gel powder at 450 °C to produce an incipient formation of MAS. The third powder (HT850) was calcined at 850 °C to produce spinel with low crystallinity. The powders were deagglomerated and then consolidated in one step using a spark plasma sintering (SPS) machine at temperatures ranging from 1260 to 1350 °C to suit their different properties. The one-step SPRS was achieved with relative densities up to 99.98 % and submicron-sized grains. However, transparent ceramics were obtained only with the HT450 and HT850 powders. The ceramic produced from the HT450 powder achieved a light transmittance of 71 % at λ = 1100 nm, Vickers hardness (HV) of 11.98 GPa, grain size of 604 nm, and relative density of 99.98 %. The ceramic produced from the HT850 powder consolidated by one-step SPRS at 1275 °C achieved a light transmittance of 71 %, HV of 12.71 GPa, grain size of 396 nm, and relative density (RD) of 99.90 %. The results showed that the HT450 powder had better sinterability, attributed to the higher reactivity of the partially reacted sol-gel particles used as precursors in this sample.

Fabrication and characteristics of eutectic hydrated salts/fumed silica composite as form-stable phase change materials for thermal energy storage

In this research, a novel form-stable composite phase change material (PCM) for building envelopes was prepared and evaluated. Calcium chloride hexahydrate (CCH) and magnesium nitrate hexahydrate (MNH) were dissolved and mixed uniformly to obtain the binary eutectic hydrated salt (BEHS) with adjustable phase change temperature. With the increase of MNH content, the phase change temperature and latent heat of BEHS gradually decreased. The BEHS with the onset temperature and peak temperature of 21.26 °C and 27.51 °C and corresponding latent heat of 142.4 J/g was selected as the PCM and combined with the support material SiO 2 to obtain BEHS/SiO 2 composite PCMs，where the minimum SiO 2 content to prevent BEHS from leaking was 25 wt%. The characterization results of SEM, XRD and FT-IR indicated that BEHS was successfully filled into the pore structure of SiO 2 , and there was good compatibility between them. By adding 2.5 wt% strontium chloride hexahydrate as a nucleating agent, the supercooling degree of BEHS/SiO 2 composite PCMs was eliminated. The onset temperature and peak temperature of BEHS/SiO 2 composite PCMs were measured to be 17.85 °C and 27.28 °C, respectively, and the corresponding latent heat was 97.3 J/g. A 300 melting and solidification cycles test proved that it possessed good thermal reliability. Moreover, the numerical simulation was performed to evaluate the effect of BEHS/SiO 2 composite PCMs on the thermal performance and energy performance of the building. The obtained results showed that composite PCMs could effectively reduce room temperature fluctuations and energy consumption. • A new type of eutectic hydrated salts/fumed silica composite PCM is prepared. • The thermal properties of eutectic salts are affected by the content of MNH. • The composite PCM has a small supercooling degree and good thermal reliability. • The composite PCM improves the thermal and energy performance of the building.

Development of MgO nanoparticles via green synthesis at varying concentrations of precursor and mahua flower extract

Green synthesis process has been developed to produce MgO nanoparticles using wet chemical method. In this process, Madhuca longifolia (M. longifolia) flower extracts has been used as a reducing and stabilizing agent and magnesium nitrate hexahydrate is used as a metal precursor. This study exhibits the effect of varied concentrations of metal precursors and flower extracts on the shape and size of the MgO nanoparticles. FTIR, UV vis spectroscopy, SEM, EDS and HRTEM analysis have been carried out to identify the functional groups involved in the reduction process, confirmation of MgO nanoparticles, morphological and elemental analysis of the MgO nanoparticles respectively. The results confirmed the presence of spherical MgO nanoparticles decorated over the surface of MgO microclusters. It is observed that the varying concentration of flower extracts and precursor have a profound effect on morphology of the nanoparticles resulting in the decrease in cluster size with the increase in extract concentration. The nanoparticles were also tested for the presence of antibacterial activity against the bacterial species of Escherichia coli and Staphylococcus aureus.