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The high-temperature corrosion behavior of anode current collectors in liquid Ag under an oxidizing atmosphere was investigated. The weight gain in oxygen was higher than that of liquid Ag because of the effective barrier formed by Ag-rich layer coated on the corrosion layer. The thickness of the corrosion layer under oxygen was approximately twice that of the layer developed under liquid Ag because of the effective barrier originating from the Ag-rich layer. The corrosion products on the surface of the specimens in both oxygen and liquid Ag were Al2O3 and FeAl2O4 from 24 to 168 h. The surface morphology that was developed on the scale of the corroded layer represented a buckle structure in liquid Ag and a convoluted structure in oxygen, which resulted from the lateral growth of the oxide. This study proved the improved stability and cost-effectiveness of using FeCrAl alloy as a current collector in a solid oxide membrane system. [ABSTRACT FROM AUTHOR]

The electroreduction of indium tin oxide (ITO) using a solid oxide membrane anode was investigated in a molten salt of CaF 2 –NaF–CaO at 1150 °C under an inert atmosphere. In the CaF 2 –NaF blank salt, the first reduction peak did not change from −0.25 V (vs. W pseudo reference electrode (R. E.)) for the addition of up to 2 wt% CaO, but the second reduction peak was observed at −0.55 V (vs. W pseudo R. E.) in 1 wt% CaO, and −0.4 V (vs. W pseudo R. E.) in 2 wt% CaO. Cyclic voltammetry analysis was carried out using ITO as the cathode, and a reduction peak was observed at +0.31 V (vs. W pseudo R. E.). This is a positive value about 0.24 V greater than the theoretical value, probably arising because of the increase in the oxygen ion activity of CaO. The optimum ITO particle size was determined to be 600–1000 μm considering the maximum reduction efficiency dependent on the sedimentation rate, specific melt droplet growth, and reduced InSn film formation. The formation of an InSn alloy with almost the same mass ratio as the initial ITO was confirmed by combining the results of X-ray diffraction and energy dispersive X-ray spectroscopy analysis. [ABSTRACT FROM AUTHOR]

Highlights • Corrosion mechanism of Ni-Co-based alloys in LiCl-Li 2 O molten salt is proposed. • Weight loss of alloys with low cobalt was less compared to those with high. • High content of Cr caused intergranular corrosion in the corrosion layer. • Excess Cr has a deleterious effect on kinetics during the hot corrosion process. Abstract In this study, hot corrosion behaviours of Haynes 282 (H282), Nimonic 90 (N90), and Haynes HR160 (HR160) in LiCl-Li 2 O molten salt were investigated at 650 °C under argon atmosphere. The corrosion rate was in the order of H282 < N90 < HR160, depending on the morphology and structure of the scale. H282 showed a localised corrosion behaviour, while N90 showed a uniform corrosion behaviour. For HR-160, intergranular corrosion was observed. The high Cr content caused intergranular corrosion in the corrosion layer. Thus, excess Cr has a deleterious effect on the corrosion kinetics during hot corrosion in LiCl-Li 2 O molten salt. [ABSTRACT FROM AUTHOR]

Abstract A lot of efforts being invested into producing efficient thermoelectric devices based on Bi 0.5 Sb 1.5 Te 3 materials for room temperature applications. Key research achievements of these efforts that incorporation of oxide nanoparticles into Bi 0.5 Sb 1.5 Te 3 materials exhibit higher thermoelectric performance in nano-composite form. Here, we prepared Bi 0.5 Sb 1.5 Te 3 nanocomposite incorporated with TeO 2 nanoparticles (NPs) by high energy ball milling and spark plasma sintering, where in-situ Sb 2 O 3 phase and triple functional interfaces were developed. The formation mechanism of in-situ Sb 2 O 3 phase in the Bi 0.5 Sb 1.5 Te 3 /TeO 2 composites was explored by the thermodynamic calculations; microstructural features and material composition in the bulk samples were investigated using high-resolution transmission electron microscopy (HRTEM) coupled with energy dispersive X-ray spectroscopy (EDS). The formation of interfaces between in situ senarmontite Sb 2 O 3 nanophase and Bi 0.5 Sb 1.5 Te 3 matrix causes an enhanced Seebeck coefficient by ∼20% due to increase of carrier energy filtering and significant reduction of thermal conductivity by ∼77% ascribed to intensified phonon scattering or trapping at 350 K. As a result, an improved dimensionless figure of merit (ZT) of 1.07 at 350 K was achieved in a Bi 0.5 Sb 1.5 Te 3 /3 wt%TeO 2 composites. The proposed in-situ reaction and interface formation mechanisms are expected to open the possibility of further increases in ZT. Graphical abstract Image 1 Highlights • Formation of in-situ Sb 2 O 3 phase in the Bi 0.5 Sb 1.5 Te 3 /TeO 2 composites was explored. • Sb 2 O 3 phase is obtained by in-situ reaction of Sb with TeO 2 during milling and SPS. • The Seebeck coefficient was enhanced owing to increase of energy filtering effect. • Thermal conductivity was reduced (77%) due to phonon scattering at interfaces. [ABSTRACT FROM AUTHOR]

Abstract This study investigated the high-temperature stability of CSZ, YSZ, and MSZ specimens in a CaCl 2 -CaF 2 -CaO molten salt at 1200 °C for the application of the materials as oxygen-ion-conducting solid-oxide membrane anodes in the electroreduction process of metal oxides. YSZ exhibited the lowest degradation among the tested specimens in a high-temperature stability test, whereas CSZ showed the highest degradation. The weight loss was not severe with concentrations of CaO up to 10 wt%. CSZ showed peaks for m-ZrO 2 , YSZ showed peaks for t-ZrO 2 and CaZrO 3 , and MSZ showed peaks for t-ZrO 2 and m-ZrO 2 in 0 wt% CaO. In the case of 5 wt% CaO, all specimens exhibited m-ZrO 2 and CaZrO 3 peaks, In the cases of 10 wt% and 20 wt% CaO, CSZ and MSZ showed peaks for CaZrO 3 , and YSZ showed peaks for m-ZrO 2 and CaZrO 3. While CSZ and MSZ became significantly looser as the CaO concentration was increased to 10 wt%, YSZ became significantly denser due to the formation of a protective layer and attack dependent on the solubility of CaO in the molten CaCl 2. In terms of long-term operation, YSZ was demonstrated to possess superior high-temperature stability compared to CSZ and MSZ, and CaO concentrations from 5 wt% to 10 wt% were found to be significantly more stable than other concentrations. Highlights • The degradation mechanism of CSZ, YSZ, and MSZ in CaCl 2 -CaF 2 -CaO molten salt is proposed. • The formation of CaZrO 3 acts as a protective layer. • YSZ shows high degradation resistance to CaCl 2 -CaF 2 molten salt that contains up to 10 wt% of CaO. • In view of long-term operation, YSZ is demonstrated to possess superior high-temperature stability compared to CSZ and MSZ. [ABSTRACT FROM AUTHOR]

Abstract The adiabatic temperatures and equilibrium phases in the FeTiO 3 - α Mg-C(B, Si)- k NaCl system (where α = 0.2–15, k = 0–3) were analyzed to predict the formation of fine powders of titanium compounds from natural ilmenite sand. From the parametric study, the critical variables were identified and optimized for the synthesis of FeTi, TiC, TiB 2 , and TiFeSi 2 under a combustion regime. The experimentally measured temperatures were in good agreement with those predicted from thermochemical calculations in the 900–1800 °C range. The purified products were characterized using X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The fine powders of titanium compounds were mainly single phase with a purity of at least 95 wt%. Considering the various stages of the synthetic process, a mechanism is proposed to explain how the process of ilmenite recovery occurred. Graphical abstract Image Highlights • Natural ilmenite was used as a precursor for synthesizing Ti compounds. • Combustion temperatures and phases were determined in FeTiO 3 -αMg-C(B, Si)- k NaCl system. • The effect of Mg and NaCl concentration on the combustion temperature was revealed. • The ilmenite was converted into FeTi, TiC, TiB 2, and FeTiSi 2 fine powders. • A reduction pathway in the synthesis of Ti compounds was proposed. [ABSTRACT FROM AUTHOR]

Abstract This paper reports the preparation of Ti microparticles that are angular and spherical in shape through the combustion of a TiO 2 + αCa (where α is moles of Ca) exothermic mixture in an inert atmosphere. The relationship between the combustion parameters and the properties of the resultant Ti particles is discussed with consideration of the effect of Ca concentration. Using excess amounts of Ca in the experiment was effective in modifying the shape of the particles from angular to spherical. The Ti powder was found to be well-dispersed and the diameter of individual particles ranged from 5 µm to 50 µm. Based on the combustion parameters, the activation energy for the redox reaction was calculated as ∼ 138 kJ/mol. This paper discusses the chemistry of the reduction process and highlights the effects of combustion temperature and the amount of liquid calcium on the characteristics of the Ti particles. Graphical abstract The combustion process in TiO 2 + Ca mixture developed a maximum temperature of about 1820 °C and resulted in Ti spherical particles. fx1 [ABSTRACT FROM AUTHOR]

Abstract We developed an attractive combustion approach for synthesizing uniformly shaped AlN dendritic crystals by combustion of Al + 0.1AlF 3 + k Al 2 O 3 powder mixtures in a nitrogen atmosphere. The combustion temperature measured for various k values was between 1650 and 1750 °C and the micro-droplets of Al formed in the beginning stages of the process were enveloped by the solid layers of Al 2 O 3 , and the subsequent multipoint nucleation and crystallization produced morphologically and size uniform dendritic crystals. We proposed a theoretical model for calculating the thickness and the number of Al 2 O 3 layers around of Al microdroplets at known concentration of Al 2 O 3. Depending on the concentration of Al 2 O 3 , these structures were simple stars with six points and stellar dendrites with multiple petals. [ABSTRACT FROM AUTHOR]

Abstract: The high‐temperature stability of YSZ and MSZ specimens was investigated in CaF2–MgF2–MgO molten salt at 1200°C. YSZ was mostly composed of m‐ZrO2 and a small part of YF3 in the early stages. The formation of YF3 was attributed to the chemical reaction between Y2O3 and MgF2, which can lead to the leaching of Y2O3 from YSZ. With an increase in exposure time, the degraded surface was coarser, and considerable amount of cracks, pores, and spallations were formed. Furthermore, no Y2O3 was found up to 120 μm of the YSZ bulk in the early stages. MSZ was composed of t‐ZrO2 after 24 hours. However, the volume fraction of m‐ZrO2 was 72% after 72 hours, and CaZrO3 was formed by the chemical reaction between CaO and ZrO2 after 168 hours. In addition, the volume fraction of m‐ZrO2 was 60% in 2.5 wt% MgO and 49% in 10 wt% MgO. In 5 wt% MgO, CaZrO3 was formed. We demonstrate that the high‐temperature stability of MSZ was better than that of YSZ, and that 10 wt% MgO was much more stable than the other concentrations of MgO. [ABSTRACT FROM AUTHOR]

We have developed a controllable method for high density of ultrafine gold nanoparticles (NP) and their uniform aggregates on exfoliated nanosheet of layered double hydroxide (LDH). The LDH nanosheet effectively supports the growth of ultrafine gold NP because the freshly exfoliated hydroxide prevents the formation of large and irregular aggregation of gold NP. We found that the reduction conditions allowed controlling the sizes and morphologies of gold NP during their growth on LDH layers. Additionally, pre-added ascorbic acid effectively induced a narrow distribution of gold NP during their reduction reactions by NaBH 4 or hydrazine hydrate. This hybrid material exhibited excellent durability and catalytic activity (>99% conversion efficiency) in the reduction of p -nitrophenol. The nanoscopic nature of exfoliated LDH nanosheets affects the catalytic performances of the hybrid catalyst, such as a high positive charge for strong binding to gold NP, and a fresh hydroxide surface for a good dispersion of the hybrid catalyst in reacting solutions. Our method can be very useful to make stable and reusable Au/LDH nanohybrids for a variety of applications. [ABSTRACT FROM AUTHOR]

In this study, a single-step combustion process for the synthesis 1-D, 2-D, and 3-D micro and nanostructures of AlN was developed. The structures were grown by combustion of Al+ k AlF 3 (or ZnF 2 )+ m NH 4 Cl reaction mixture under 4.0 MPa nitrogen atmosphere. Based on experimental data, the growth conditions, morphology, and composition, optical, and thermal properties of AlN micro and nanostructures were determined. The formation of structures was associated with the combustion temperature, liquid and gas-phase reactions, and the type of additives used in the experiments. The new insight, we gleaned from this study may help in the selective growth of AlN micro and nanostructures of different morphology, enhancing their functionality. [ABSTRACT FROM AUTHOR]

In this study, we examined the effect of potassium perchlorate (KClO 4 ) and magnesium hydroxide (Mg(OH) 2 ) additives on the combustion behavior of a ZrO 2  + 2Mg mixture to produce a fine powder of zirconium metal. The results of thermodynamic analysis and experiments imply that nearly 0.04 mol of KClO 4 is needed to initiate a combustion reaction in the ZrO 2  + 2Mg system. As the amount of KClO 4 increases from 0.04 to 0.1 mol, the combustion temperature increases from 1250 to 1850 °C. This results in formation of fine zirconium powder with a typical particle size of less than 5 µm, and with 1.4–2.2 wt% residual oxygen. Subsequent reduction of particle size to 100–500 nm, and oxygen content to <1.0 wt% was achieved by adding Mg(OH) 2 . The as-prepared Zr powder was mixed with nitrocellulose and printed onto 10–100 µm thin-layers to study their burning stability. The wave propagation in a thin layer was on the order of 0.35–30 cm/s, which is suitable for applications requiring localized power generation. [ABSTRACT FROM AUTHOR]

Combustion of inorganic powder mixtures is not only one of the chemical routes of fabrication of advanced inorganic materials but is also drawing attention as a high-temperature process to grow inorganic nanocrystals of various shapes and morphologies. Here, we demonstrate the formation of AlN 3-D structures with diverse morphologies: from 6-fold patterned crystals to multilayer hierarchical structures. We examined the possible chemical mechanisms governing the formation of AlN crystals and the growth behaviour based on FESEM and TEM observations. [ABSTRACT FROM AUTHOR]

The purification of a LiCl-KCl salt mixture was carried out by a zone-refining process. To improve the throughput of zone refining, three heaters were installed in the zone refiner. The zone-refining method was used to grow pure LiCl-KCl salt ingots from a LiCl-KCl-CsCl-SrCl 2 salt mixture. The main investigated parameters were the heater speed and the number of passes. From each zone-refined salt ingot, samples were collected axially along the salt ingot and the concentrations of Sr and Cs were determined. Experimental results show that the Sr and Cs concentrations at the initial region of the ingot were low and increased to a maximum at the final freezing region of the salt ingot. Concentration results of the zone-refined salt were compared with theoretical results furnished by the proposed model to validate its predictions. The k eff values for Sr and Cs were 0.55 and 0.47, respectively. The correlation between the salt composition and separation behavior was also investigated. The k eff values of the Sr in LiCl-KCl-SrCl 2 and the Cs in LiCl-KCl-CsCl were found to be 0.53 and 0.44, respectively, by fitting the experimental data into the proposed model. [ABSTRACT FROM AUTHOR]

The isothermal and cyclic corrosion behaviors of magnesia-stabilized zirconia in a LiCl-Li 2 O molten salt were investigated at 650 °C in an argon atmosphere. The weights of as-received and corroded specimens were measured and the microstructures, morphologies, and chemical compositions were analyzed by scanning electron microscopy, X-ray energy dispersive spectroscopy, and X-ray diffraction. For processes where Li is formed at the cathode during electrolysis, the corrosion rate was about five times higher than those of isothermal and thermal cycling processes. During isothermal tests, the corrosion product Li 2 ZrO 3 was formed after 216 h. During thermal cycling, Li 2 ZrO 3 was not detected until after the completion of 14 cycles. There was no evidence of cracks, pores, or spallation on the corroded surfaces, except when Li was formed. We demonstrate that magnesia-stabilized zirconia is beneficial for increasing the hot corrosion resistance of structural materials subjected to high temperature molten salts containing Li 2 O. [ABSTRACT FROM AUTHOR]

AbstractThe liquid exfoliation of hydrotalcite-like α-Co(OH)2 in formamide produced a new pink β-form of Co(OH)2 nanosheets [Ex-NS-Co(OH)2] with unique nanoscopic properties: a larger surface area of active hydroxides and a much narrower oxidation–reduction potential for the Co2+ ions in the hydroxide layer than those of the bulk α-Co(OH)2. These unprecedented properties of Ex-NS-Co(OH)2 were applied to the topochemical synthesis of crystalline Co3O4 nanocubes (NCs) with clear edges and no impurity phases from an aqueous solution of Co2+ ions at 70 °C. A Co3O4 NC/C catalyst exhibited good catalytic activity for the oxygen reduction reaction (ORR) and higher stability under a continuous electrochemical operation than that of commercial Pt/C. [ABSTRACT FROM AUTHOR]

In this paper we describe a progressive two-step process that allows zirconium fluoride (ZrF 4 ) contained in spent baths for etched zirconium alloys to be effectively recycled on a pilot scale and produce a high purity regenerated pickling acid. In the first step, a spent pickling liquor is treated by a BaF 2 suspension to produce water insoluble Ba 2 ZrF 8 . After filtration of Ba 2 ZrF 8 more than 99.9 wt % purity pickling acid is regenerated. The precipitation mechanism of Ba 2 ZrF 8 is discussed and the role of BaF 2 particles size on the precipitation process is demonstrated. In the second step the as-precipitated Ba 2 ZrF 8 is mixed with Mg and Cu metal powders and heat-treated at 1200 °C (or above) to produce CuZr alloy ingot. The characteristics of the ingot are discussed in regard to Cu concentration and the heating temperature. [ABSTRACT FROM AUTHOR]

The exothermic reduction of oxides mixture (MoO 3 +2SiO 2 ) by magnesium in NaF melt enables the synthesis of nanocrystalline MoSi 2 powders in near-quantitative yields. The combustion wave with temperature of about 1000–1200 °C was recorded in highly diluted by NaF starting mixtures. The by-products of combustion reaction (NaF and MgO) were subsequently removed by leaching with acid and washing with water. The as-prepared MoSi 2 nanopowder composed of spherical and dendritic shape particles was consolidated using the spark plasma sintering method at 1200–1500 °C and 50 MPa for 10 min. The result was dense compacts (98.6% theoretical density) possessing submicron grains and exhibiting hardness of 8.74–12.92 GPa. [ABSTRACT FROM AUTHOR]

In this study, the isothermal and cyclic corrosion behaviors of custom-made nickel-based alloys (N105, N107, and N108) with various elemental compositions in a LiCl-Li 2 O molten salt were investigated at 650 °C in argon atmosphere. The isothermal and cyclic corrosion behaviors were studied by measuring the mass changes, surface morphologies, cross-sectional morphologies with elemental distribution, and the compositional changes of the subscale and substrate as well as the spalled oxide scale. Under the isothermal and cyclic corrosion test, the corrosion rate was in the order of N108 < N105 < N107, and N107 < N105 < N108, respectively, which depended on the morphology and structure of the crystals formed on the surface of the outer scale in contact with the molten salt, and was also related to the region of Al and Cr depletion. After the isothermal corrosion test, the hot corrosion products formed in N105 were Cr 2 O 3 , NiCr 2 O 4 , and Li 2 Ni 8 O 10 and those in N107 were Cr 2 O 3 and NiCr 2 O 4 , while Cr 2 O 3 , NiCr 2 O 4 , and LiTiO 2 were identified as the hot corrosion products of N108. However, the hot corrosion products of N105, N107, and N108 were Cr 2 O 3 , NiCr 2 O 4 , and LiFeO 2 after the cyclic corrosion test. [ABSTRACT FROM AUTHOR]

We investigated monomethylmercury (MMHg) concentrations in 448 samples of four common fish species (barbel steed, largemouth bass, leopard mandarin, and bluegill) and the trophic states of 14 artificial reservoirs in South Korea in order to understand how trophic states of reserviors affect MMHg concentrations in fish. The trophic state index (TSI) of each reservoir was determined using empirical equations based on the monthly chlorophyll-a, total phosphorus, and Secchi depth, collected over a three-year period. The length-normalized MMHg concentrations in fish showed a negative correlation with the TSI based on chlorophyll-a (r 2 = 0.90) and total phosphorus (r 2 = 0.75) that may be a result of particle dilution of MMHg in surface waters. This study revealed that MMHg accumulation in fish was better correlated with TSI than MMHg in water, therefore, we suggest that the measurement of TSI based on chlorophyll-a and total phosphorus is an effective way to predict MMHg bioaccumulation across diverse reservoirs. [ABSTRACT FROM AUTHOR]

We demonstrate the facile microwave-assisted synthesis of a porous organic framework 1 and the sulfonated solid ( 1S) through postsubstitution. Remarkably, the conductivity of 1S showed an approximately 300-fold enhancement at 30 °C as compared to that of 1, and reached 7.72×10−2 S cm−1 at 80 °C and 90 % relative humidity. The superprotonic conductivity exceeds that observed for any conductive porous organic polymer reported to date. This material, which is cost-effective and scalable for mass production, also revealed long-term performance over more than 3 months without conductivity decay. [ABSTRACT FROM AUTHOR]

We demonstrate the facile microwave-assisted synthesis of a porous organic framework 1 and the sulfonated solid ( 1S) through postsubstitution. Remarkably, the conductivity of 1S showed an approximately 300-fold enhancement at 30 °C as compared to that of 1, and reached 7.72×10−2 S cm−1 at 80 °C and 90 % relative humidity. The superprotonic conductivity exceeds that observed for any conductive porous organic polymer reported to date. This material, which is cost-effective and scalable for mass production, also revealed long-term performance over more than 3 months without conductivity decay. [ABSTRACT FROM AUTHOR]

A zone refining processing was utilized to purify tellurium (Te) metal using a locally melted zone caused by high-frequency induction heating. The travel rate of the molten zone was set as a parameter. The purification efficiency for each impurity (Bi, Sb, Sn, and Se) in the tellurium sample was analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES), and the experimental results were compared with the theoretical results furnished by the proposed model to validate its predictions. The experimental results indicated that a lower travel rate of the molten zone and repetition of passes were more efficient for purification. The effective distribution coefficient k eff and the k eff values of bismuth, antimony, tin, and selenium were 0.5, 0.35, 0.22, and 0.58, respectively. These elements were effective for the purification of Te by zone refining. The obtained distribution coefficient k eff values of impurities can be used as standards for the purification of Te by zone refining. The Vickers hardness was measured, and a correlation between hardness and concentration was observed, with an average Vickers hardness was 62 Hv . [ABSTRACT FROM AUTHOR]

In this study, a combustion process for a TiO 2 + 0.12Al + (2.5 + 6 k )Mg + 0.021V 2 O 5 + k MgCl 2 ·6H 2 O mixture was studied to fabricate Ti-6Al-4V alloy spherical particles. From the temperature-time profiles, the average value of the synthesis temperature was estimated to be 1650 ± 20 °C. Based on FESEM observations, spherical shape particles were obtained when 0.05–0.1 mol MgCl 2 ·6H 2 O was added to the initial reaction mixture. Therefore, spherical alloy particles were achieved by consecutive processes of cooling and acid purification of the burned down sample. According to laser particle size analysis, the average diameter of the spheres was between 5 and 25 μm. A selective laser melting process was applied to build dense Ti-6Al-4V alloy samples. The tensile properties and the microhardness were evaluated and compared to those characteristics of a reference sample prepared from commercial Ti-6Al-4V alloy spherical powder. [ABSTRACT FROM AUTHOR]

The purification of LiCl salt mixture has traditionally been carried out by a melt crystallization process. To improve the throughput of zone refining, three heaters were installed in the zone refiner. The zone refining method was used to grow pure LiCl salt ingots from LiCl-CsCl-SrCl 2 salt mixture. The main investigated parameters were the heater speed and the number of passes. A change in the LiCl crystal grain size was observed according to the horizontal direction. From each zone refined salt ingot, samples were collected horizontally. To analyze the concentrations of Sr and Cs, an inductively coupled plasma optical emission spectrometer and inductively coupled plasma mass spectrometer were used, respectively. The experimental results show that Sr and Cs concentrations at the initial region of the ingot were low and reached their peak at the final freezing region of the salt ingot. Concentration results of zone refined salt were compared with theoretical results yielded by the proposed model to validate its predictions. The k eff of Sr and Cs were 0.13 and 0.11, respectively. The decontamination factors of Sr and Cs were 450 and 1650, respectively. [ABSTRACT FROM AUTHOR]

This study deals with combustion behavior of B 2 O 3 /Mg/NH 4 Cl/C complex systems for the synthesis of amorphous boron (B), boron carbide (B 4 C), and boron nitride (BN) nanostructures. The raw mixtures used in the experiments were prepared on the base of a B 2 O 3 –Mg precursor mixture, which is sufficiently exothermic to maintain a self-propagating regime of the combustion reaction. Thermodynamic analysis of the combustion temperatures and experimental validation indicate that the 1000–1500 °C temperature range is very effective for synthesizing the nanostructures of B, B 4 C, and BN. It was found that B-containing functional nanostructures are mainly spherical nanoparticles (B) or nanosheets (B 4 C, BN). The phase composition and microstructural characteristics of the final products were evaluated based on the combustion temperature and solid/liquid phase changes. [ABSTRACT FROM AUTHOR]

The intergranular carbide precipitation behavior and its effect on the tensile properties were investigated in alloy 690. The precipitation of intergranular carbides, identified as Cr-rich M 23 C 6 , was retarded on the low-angle grain boundaries and the coincidence-site lattice boundaries. The M 23 C 6 carbides have a cube-cube orientation relationship with the matrix. The ultimate tensile strength, yield strength, and elongation of the solution annealed alloy 690 are 648.2 ± 8.2 MPa, 242.8 ± 10.5 MPa and 44.9 ± 2.3%, respectively. The ultimate tensile strength and the yield strength increased to 764.8 ± 7.8 MPa and 364.8 ± 10.2 MPa until the aging time reached 16 h. This increase is ascribed to the M 23 C 6 carbide acting as reinforcements. However, when the aging time exceed 16 h, these properties gradually decreased with increasing aging time. The decrease in ultimate tensile strength, yield strength, and elongation were mainly caused by the intergranular cracking due to the low bond strength between the carbide and the matrix. [ABSTRACT FROM AUTHOR]

A simple surface modification strategy to generate lithophilic sites in carbon-coated Si nanoparticles significantly enhances the capacity as well as cycling stability. [Display omitted] • A simple surface treatment process generates lithophilic surface groups on carbon-coated Si nanoparticles. • The surface-functionalized electrode of Si-C-AT shows a higher diffusion coefficient than Si-C. • The Si-C-AT shows a reversible capacity of 1575 mA h g−1 after 200 cycles at a current rate of 0.5C. • Functional groups on the Si-C-AT assist in accumulating the lithium-ions in excess on the carbon surface. Silicon nanoparticles (Si NPs) are potential anode materials for next-generation lithium-ion batteries due to their natural abundance, low discharge potential, and high theoretical capacity. Carbon coating improves the capacity of the Si NPs, protects them from disintegration during the lithiation/delithiation process, and provides an additional conductive matrix. Surface modification as a tool leading to capacity enhancement in carbon-coated Si NPs has rarely been explored. It is a straightforward process that involves the surface functionalization of carbon-coated Si NPs (Si-C) with the oxidizing acidic mixture. The surface-treated Si-C functionalized with carboxyl and hydroxyl groups in excess on the carbon surface of Si-C NPs. As a result of surface modification, the acid-treated Si-C (Si-C-AT) displayed a higher reversible capacity of 1575 mA h g−1 after 200 cycles compared to the Si-C (1261 mA h g−1) and bare Si (961 mA h g−1). This high capacity of Si-C-AT is a cumulative outcome of the functional groups and the disordered structure of the carbon shell. The functional groups act as lithophilic sites, and the disordered carbon shell facilitates the insertion-desertion of lithium ions. The simple surface modification strategy proposed in the present study significantly enhances the cyclability of the Si-C-AT NPs and has great potential for application in carbon-coated materials for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

The present investigation studied the recycling of zinc from brass ash which is a secondary product produced during the brass smelting process. A retiring cycle was devised to produce high-purity ZnO nanopowders. Recovery of > 90 wt% of the total zinc available was achieved after the calcination of brass ash at 700 °C and a multistage hydrometallurgical treatment at room temperature. ZnO powder produced by the developed method was analyzed by X-ray diffraction, transmission electron scanning microscopy, ICP-AES and BET analysis. The ZnO nanopowder obtained from the brass ash was well dispersed and the size of the individual particles was in the range of 30–50 nm. The purity of the powder was 99.83 wt%, and the surface area was about 30.5 m 2 /g. A relative density level of about 98.1% was reached with ZnO pellets sintered at 1300 °C. [ABSTRACT FROM AUTHOR]

Hollow carbon nanospheres as potential cathode materials for lithium-sulfur (Li-S) batteries were successfully synthesized using a metathesis reaction between sodium azide and halogen polymer. The reaction was driven by thermal heat from the exothermic recombination of Na + and Cl − (or F − ) ions into NaCl (or NaF) salts. The result was an increase of the overall system temperature up to 1320–1750 °C followed by the simultaneous formation of sodium halide-carbon core–shell nanoparticles. Therefore, hollow carbon nanospheres with diameter and shell thickness of ∼50–500 nm and ∼10–50 nm, respectively, were produced after water washing of the reaction product. The composite cathode materials for Li-S batteries were manufactured by infiltrating sulfur into the hollow core of nanospheres. The electrochemical cycling showed discharge capacity of ∼700 mAh g −1 (after 100 cycles) at 0.5 C current rate which is more than ∼2.4 times larger than that for the sulfur/carbon black composites prepared by the same technique. The enhancement of battery performance was attributed to the well-organized and unique 3D structure of hollow carbon, enabling better utilization of sulfur. [ABSTRACT FROM AUTHOR]

Combustion based synthesis of AlN nanoparticles using the "solid nitrogen" promotion reaction was investigated in Al2O3 + 3Mg system in nitrogen atmosphere. A controlled amount of Mg + 0.5NH4Cl mixture as a solid source of nitrogen was blended with the Al2O3 + 3Mg starting system and the synthesis reaction of AlN nanoparticles was conducted using the exothermic heat of the entire reaction system. The resulting AlN nanoparticles were characterized by X-ray diffraction (XRD), Raman and Fourier transform infrared spectroscopy (FTIR), PL spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller surface area techniques. The analysis results confirmed that single phase and crystalline AlN nanoparticles with an average size of 50-500 nm were obtained from the developed approach. Photoluminescence spectra of AlN nanopowders under the excitation of 230-270 nm UV light revealed that AlN emits yellow-red light having a wavelength near to 590 nm. The chemistry of the combustion process is discussed and the basic reactions that led to the formation of AlN are presented. [ABSTRACT FROM AUTHOR]

High-quality two-dimensional (2D) nanosheets of B 4 C were synthesized using a facile combustion reaction with a reaction mixture comprising boron oxide (B 2 O 3 ), magnesium (Mg), and polyvinylchloride (C 2 H 3 Cl) n . The ability to tune the nanosheets of boron carbide was achieved by controlling the combustion temperature within a range of 1500–1700 °C and by using polyvinylchloride powder as the carbon source. FE-SEM and TEM images of the acid leached combustion products show sheet-like B 4 C particles with thicknesses of about 10–50 nm and edge lengths from 0.1 to several micrometers. The chemistry of the combustion process and the formation mechanism of B 4 C nanosheets are discussed based on the experimental findings. [ABSTRACT FROM AUTHOR]

The harsh atmosphere of the sulfur–iodine process used for producing hydrogen requires better corrosion resistance and mechanical properties than are possible to obtain with pure tantalum. Ta–W alloy is superior to pure tantalum but is difficult to alloy due to its high melting temperature. In this study, substrate samples were coated with Ta–W (Ta–7W, Ta–4W and Ta–1W) using the Multi-Anode Reactive alloy Coating (MARC) process in molten salt (LiF–NaF–K 2 TaF 7 ), with varying distances between cathode and anode. In the case of Ta–4W, a corrosion rate of less than 0.011 mm/year was attained in hydriodic acid at 160 °C, and thickness uniformity was 80.3 ± 2.15 μm. Also, the resulting coated films had hardnesses up to 12.9% stronger than pure tantalum coated film. The alloy coating films also contributed to significant enhancement of corrosion resistance. [ABSTRACT FROM AUTHOR]

Electroless deposition reaction (EDR) is a promising route for the synthesis of copper (Cu) and silver (Ag) dendritic structures with a controllable morphology. Here, we demonstrate the use of an electroless deposition reaction on the interface between an iron foil and aqueous solutions of either Cu or Ag salts to produce well-defined Cu and Ag dendritic nanostructures at room temperature. The dendritic structures and morphology were characterized based on the reaction time, Cu and Ag salt concentration, and diethylene glycol (DEG) content in the aqueous solution. We also demonstrate control over the dendrite sizes, morphologies and growth mechanisms. The electrical resistivity and improved sheet resistance were also evaluated in an anisotropic conductive film prepared from dendritic silver powder. [ABSTRACT FROM AUTHOR]

The importance of ZT in thermoelectric (TE) materials is critical for green power generation and cooling applications. Therefore, tremendous efforts were underway to improve ZT, in which we proposed a layer structured approach by successively arranging of coarse Bi 0.5 Sb 1.5 Te 3 (BST) and fine BST/0.07Cu microstructure materials and investigated their transportation mechanism. The dual bulk microstructure was well-bonded and confirmed by analyzing the microstructure through scanning electron microscope (SEM), electron backscatter diffraction analysis (EBSD) and simulated the electrical potential and temperature distribution during spark plasma sintering with COMSOL software. The results indicate that the highest power factor of 3.8 mW/m-K2 was attained in the layer structured sample, which is significantly higher than other samples due to its synergistically optimized electrical conductivity and Seebeck coefficient. Through the varied microstructure, the κ was decreased at 400 K and consequently the ZT was improved to 1.25 at 400 K for the layer structure samples. Therefore, it is suggested that layered arrangement of different microstructure material could improve the thermoelectric properties of materials. [Display omitted] • Novel fabrication of hierarchical structured material with successive arrangement of two different microstructures. • Successful consolidation of well-bonded hierarchical material and confirming by simulating results from COMSOL software. • Highest power factor of 3.8 * 10−3 W/m-K2 obtained by transportation of charge carriers through two different energy levels. • Hierarchical structured sample show highest figure of merit of 1.25 at 400 K which is highest among all reported samples. [ABSTRACT FROM AUTHOR]

A melt-assisted solid flame synthesis approach was applied to synthesize boron nanoparticles in argon gas and air atmospheres. For this purpose, we investigated the characteristics of a thermally induced combustion wave in B 2 O 3 + α Mg mixtures ( α = 1.0–1.5 mol) in argon and air atmospheres. Utilizing stoichiometrically insufficient amounts of magnesium ensured that a large portion of molten B 2 O 3 remained in the sample, which reduced the combustion parameters and favored the formation of boron nanoparticles. Under these conditions the combustion temperature and burning velocity were controlled in the range of 1300–1580 °C and 0.065–0.18 cm/s, respectively, and boron nanoparticles in a ∼20–200 nm size range were obtained. The characteristics of boron nanoparticles (morphology, purity, specific surface area, oxidation activity, etc.) were analyzed and a reaction pathway leading to boron nanoparticles synthesis was proposed. [ABSTRACT FROM AUTHOR]

We have investigated a thermally induced combustion route for preparing 2D hexagonal BN nanoplates from B 2 O 3 +(3+0.5 k )Mg+ k NH 4 Cl solid system, for k =1–4 interval. Temperature–time profiles recorded by thermocouples indicated the existence of two sequential exothermic processes in the combustion wave leading to the BN nanoplates formation. The resulting BN nanoplates were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy, PL spectrometry, and Brunauer–Emmett–Teller surface area analysis. It was found that B 2 O 3 was converted into BN completely (by XRD) at 1450–1930 °C within tens of seconds in a single-step synthesis process. The BN prepared at a k =1–4 interval comprised well-shaped nanoplates with an average edge length ranging from 50 nm to several micrometer and thickness from 5 to 100 nm. The specific surface area of BN nanoplates was 13.7 g/m 2 for k =2 and 28.4 m 2 /g for k =4. [ABSTRACT FROM AUTHOR]

Background: In South Korea, a cluster of acute lung disease patients included lung injury disease suspected of being caused by the use of humidifier disinfectants. We examined the relationship between humidifier disinfectant exposure and clinically diagnosed humidifier disinfectant-associated lung injury (HDLI) in a family-based study. Methods: This case-control study included 169 clinically confirmed HDLI cases and 303 family controls who lived with the HDLI patients. A range of information on exposure to humidifier disinfectants was obtained using a structured questionnaire and field investigations. Odds ratios (ORs) and confidence intervals (CIs) were estimated using unconditional logistic regression models that were adjusted for age, sex, presence of a factory within 1 km of residence, and the number of household chemical products used. Results: HDLI risk increased approximately two-fold or more among the highest quartile compared with the lowest quartile in terms of the hours sleeping in a room with an operating humidifier treated with disinfectant (adjusted OR = 2.0, 95 % CI = 1.1-3.7), average hours of disinfectant-treated humidifier use per day (adjusted OR = 2.1, 95 % CI = 1.0-4.5), airborne disinfectant intensity (adjusted OR = 2.6, 95% CI = 1.2-5.3), and cumulative disinfectant inhalation level (adjusted OR = 2.0, 95% CI = 1.0-4.1). HDLI risk increased as the distance of the bed from humidifier gets shorter; compared with longer distance (> 1 m), the odds ratio was 2.7 for 0.5 to 1 m (95 % CI = 1.5-5.1) and 13.2 for <0.5 m (95 % CI = 2.4-73.0). Conclusions: The use of household humidifier disinfectants was associated with HDLI risk in a dose-response manner. [ABSTRACT FROM AUTHOR]

The synthesis of AlN nanoparticles in non-isothermal high-temperature conditions was developed. The process involved Al 2 O 3 –Mg–NH 4 Cl mixtures preparation and combustion in nitrogen atmosphere. Temperature profiles in the combustion waves were recorded by thermocouples, and the values of combustion temperature and wave velocity were determined from the recorded profiles. The existence of two independed combustion regimes with maximum temperatures of about 850 °C and 1400–1600 °C were revealed based on concentrations of NH 4 Cl. AlN nanocrystals were obtained and investigated by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller surface area. AlN nanocrystals prepared under non-isothermal combustion process were comprised well distributed multi-faceted particles with an average size of 50–200 nm. The chemical reactions in the combustion wave were discussed and a possible thermochemical pathway for the synthesis of AlN nanoparticles was proposed. [ABSTRACT FROM AUTHOR]

Amorphous boron nanoparticles were synthesized by heating a B 2 O 3 + 3 Mg + k NaCl ( k is the number of moles of NaCl) exothermic mixture in a laboratory oven at 800 °C under argon flow. NaCl was used as inert material to decrease the maximum combustion temperature of the reaction mixture when it was self-ignited after the melting of Mg at 650 °C. The size of the boron nanoparticles extracted from the final product by acid leaching ranged between 30 and 300 nm for k values ranging from 1 to 5. Moreover, increasing the value of k from 1 to 5 resulted in an increase in the specific surface area of the nanoparticles from 40 to 74 m 2 g −1 . However, at k = 10, a decrease in the specific surface area to 47.56 m 2 g −1 was recorded due to incomplete reduction of B 2 O 3 . The ignition point of boron nanoparticles in air as estimated using a thermocouple was approximately 300 °C. Digital camera recording of the combustion process of boron nanoparticles in air revealed that the burning speed of the nanoparticles increased significantly from 0.3 to 15 cm/s when k increased from 1 to 5. [ABSTRACT FROM AUTHOR]

Spent nuclear fuel is electro-reduced in a chemically aggressive atmosphere wherein oxygen is generated at the anode in the presence of lithium molten salt containing a strong basic oxide, Li 2 O. Herein, the effect of the Li 2 O concentration on the hot corrosion behaviour of Haynes 263 and Inconel X-750 was investigated by immersion in molten LiCl–Li 2 O salt (1, 3, and 5 wt% Li 2 O) for 72–288 h at 650 ℃ under oxidizing atmosphere. For Li 2 O concentrations of approximately 3%, the weight loss and the products formed by the basic fluxing mechanism differed due to the dependence on the O2− concentration. • Effect of Li2O concentration on corrosion of Ni-based alloys was investigated. • Corrosion occurred by basic fluxing with O2 − ; products varied with ≥ 3 wt% Li2O. • Dense and continuous Cr-rich oxide layer prevented the inward diffusion of oxygen. • Ni-rich layer hindered outward diffusion of the alloying elements in the base metal. • Excess Fe appeared to be deleterious to the overall corrosion resistance. [ABSTRACT FROM AUTHOR]

Excessive methylmercury (MeHg) accumulation in dietary fish is a global concern due to its harmful effects on human health, however, environmental factors affecting MeHg accumulation in reservoir ecosystems are not clearly known. In this study, we aim to identify the main sources of MeHg in the water column and the critical factors related to MeHg concentration and methylation rate constant (k m) in sediment and total Hg concentration in fish using five-year (2016–2020) monitoring data of the five artificial reservoirs. The preliminary mass budgets constructed using the measurement and online data showed that sediment transport dominated over runoff in the long residence time reservoirs (400–475 days), while runoff dominated over sediment transport in the short residence time reservoirs (10 days). Whereas the sediment k m showed a comparable variation with the algal biomass, the sediment MeHg concentration and the length-normalized Hg concentration in the barbel steed and bluegill increased in the longer residence time reservoirs with lower algal biomass. As MeHg accumulation in sediment and fish tends to increase in the slowly overturning reservoirs, the hydraulic residence time should be carefully managed to meet the best protection of human health from chronic Hg exposure by fish consumption. [Display omitted] • MeHg mass budgets were estimated using the Hg data from five artificial reservoirs. • Sediment was the main source of MeHg in the long residence time reservoirs. • Runoff was the main source of MeHg in the short residence time reservoirs. • MeHg in sediment and fish were higher in the long residence time reservoirs. • Turnover period should be carefully managed to lower MeHg in reservoir fish. [ABSTRACT FROM AUTHOR]

The article offers an approach to prepare the exfoliated layered double hydroxide (LDH) nanosheet decorated with dense and uniform platinum (Pt) nanoparticals (NPs) through a precursor-exchange and a thermal reduction process. Topics discussed include the LDH nanosheet colloiding in formamide prepared by exfoliation of the nitrate form of the LDH nanocrystals; and dense and uniform Pt NPs being synthesized on the exfoliated LDH nanosheets through precursor exchange of the precursor ions.

Highlights: [•] A facile synthesis has been developed to convert directly solid Na2SiO3. [•] The synthesis has been carried out at ambient pressure and temperature. [•] Hydrolysis was performed using ethanol, Na2SiO3 particles and HCl solution. [•] Other precipitants (NH4Cl, (NH4)2SO4, B2O3) were tested. [•] The particle characteristics were investigated by TGA, FE-SEM, XRD, and BET. [Copyright &y& Elsevier]

Abstract: Herein, we present the low-temperature solid-phase combustion synthesis of tantalum carbide (TaC), TaC/tantalum silicide (TaSi2), and TaC/tantalum boride (TaB) nanoparticles by the silicothermic reduction of potassium fluorotantalate (K2TaF7) in the presence of carbon, boron, and polytetrafluoroethylene (PTFE, 1 [1] BJH, Barrett–Joyner–Halenda; HRTEM, high-resolution transmission electron microscopy; MMC, metal matrix composite; PFTE, polyfluorotetraethylene; PTFE; polytetrafluoroethylene; RF, radio frequency; SAED, selected area electron diffraction pattern; T c , combustion temperature; TEM, transmission electron microscopy; U c , combustion velocities; XRD, X-ray diffractometer. (C2F4) n ). The temperature–time profiles of the combustion wave were measured by thermocouples and used to calculate the combustion parameters: temperature and wave velocity. The flame temperature was found to increase with the concentration of PTFE. Using high resolution transmission electron microscopy, a homogeneous distribution of highly crystalline nanoparticles was observed. The thermal–kinetic activation energy, the heat released during each of the individual reactions, and the chemical mechanism of the overall combustion process are discussed with respect to the final products. [Copyright &y& Elsevier]

Abstract: For the first nationwide representative survey on the environmental health of children and adolescents in Korea, we designed the Korean Environmental Health Survey in Children and Adolescents (KorEHS-C) as a two-phase survey and planned a sampling strategy that would represent the whole population of Korean children and adolescents, based on the school unit for the 6-19 years age group and the household unit for the 5 years or less age group. A pilot study for 351 children and adolescents aged 6 to 19 years in elementary, middle, and high school of two cities was performed to validate several measurement methods and tools, as well as to test their feasibility, and to elaborate the protocols used throughout the survey process. Selected exposure biomarkers, i.e., lead, mercury, cadmium in blood, and bisphenol A, metabolites of diethylhexyl phthalate and di-n-butyl phthalate and cotinine in urine were analyzed. We found that the levels of blood mercury (Median: 1.7 ug/L) and cadmium (Median: 0.30 ug/L) were much higher than those of subjects in Germany and the US, while metabolites of phthalates and bisphenol A showed similar levels and tendencies by age; the highest levels of phthalate metabolites and bisphenol A occurred in the youngest group of children. Specific investigations to elucidate the exposure pathways of major environmental exposure need to be conducted, and the KorEHS-C should cover as many potential environmental hazards as possible. [Copyright &y& Elsevier]

Tantalum nitride nanoparticles were produced from a (K2TaF7 +5NaN3) exothermic mixture under the combustion regime. The effects of the K2TaF7/NaN3 ratio and KF and NH4F concentrations on the combustion parameters, product composition, and size of the tantalum nitride particles were studied. Depending on the synthesis conditions, the combustion temperature was maintained in the 700–1200°C range, resulting in hexagonal ε-TaN, TaN0.8, and Ta2N phases. The dominant phases were TaN and TaN0.8 in the 1000–1200°C range, whereas only the Ta2N phase was present in the 700–100°C range. Pure-phase cubic tantalum nitride (δ-TaN) was produced with 4.0mol of NH4F at a combustion temperature of ~800°C. Under controlled reaction conditions, the size of the tantalum nitride particles was about 10–50nm. We also found that during the synthesis, the stainless steel tube located inside of the reaction mixture was partially coated with fine TaN crystals. The mechanism of the combustion process is discussed in regards to the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: Reed bristles (Andropogon virginicus) were used as precursors and bio-templates for tubular carbon synthesis. The carbonization of the bristles was performed at 1200°C in a double crucible system using charcoal as a reducing agent. Following carbonization, carbon microtubes with outer and inner diameters of 4–8 and 3–7μm, respectively, were obtained. Moreover, the seeds of reeds demonstrated catalytic activity that led to the formation of multiwalled carbon nanotubes with outer diameters of 10–15nm. The BET specific surface area of CMTs prepared at 1200°C calculated using the adsorption data was 145m2/g. The corresponding pore size evaluated using the HK plot was 0.5–1.5nm. [Copyright &y& Elsevier]

Abstract: Zirconium (Zr) has commonly been used as a cladding material of nuclear fuel. Moreover, it is regarded as the only material that can be used for nuclear fuel cladding because it has the lowest neutron capture cross section of any metal element and because it has high corrosion resistance and size stability. In this study, Hf-free Zr tubes (Zr–1Nb–1Sn–0.1Fe) were used as anode materials and electrorefining was performed in a LiF–KF eutectic 6wt.% ZrF4 molten fluoride salt system. As a result of electrolysis, Zr scrap metal was recycled into pure Zr with low levels of impurities, and the size and density of the Zr deposit was controlled using applied current density. [Copyright &y& Elsevier]

Abstract: It is important to understand electrochemical phenomena in order to design an electrorefiner system suitable for pyroprocessing, particularly one equipped with complicated electrodes. Computer simulation of the electrochemical cells is an effective tool for the visualization of processing parameters such as the potential distribution, current density, and concentration profile. The electrochemical parameters considered in this study are the exchange current density distribution and electrode arrangement. The application of a numerical model to design an electrorefiner for spent metallic nuclear fuel is discussed with respect to throughput, impurity contamination, and operating mode. A commercial finite element method package was used. In addition, calculations of the tertiary current density and an experimental validation of these results are presented. [Copyright &y& Elsevier]