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As one of the most widely used inorganic fine powder fillers, calcium carbonate is cheap. However, considering its poor light transmittance, it is not suitable to be added to resin matrix composites that require high light transmittance. Aluminum hydroxide has good light transmission and flame retardancy, but it is more expensive than calcium carbonate. CaCO3/Al(OH)3 composites with a core-shell structure that showed a trend toward the performance of aluminum hydroxide not only improved the surface properties of CaCO3, but also increased the added value of CaCO3. In the present paper, CaCO3/Al(OH)3 composites were successfully prepared in sodium aluminate solution via heterogeneous nucleation. Four types of calcium sources, including calcite-type precipitated calcium carbonate, vaterite-type precipitated calcium carbonate, ground calcium carbonate with two different particle sizes as the precursors and supersaturated sodium aluminate solution as the substrate, have been deeply investigated in terms of their influence on the preparation of CaCO3/Al(OH)3 composites. Results showed that the calcium carbonate precursor greatly affected the formation of CaCO3/Al(OH)3 composites. Both the precipitated calcium carbonate and the small particle ground calcium carbonate are likely to undergo anti-causticization and a complexation reaction with it to generate 3CaO·Al2O3·6H2O and 3CaO·Al2O3·CaCO3·11H2O, which go against the coating of calcium carbonate with aluminum hydroxide. Within the experimental range, the use of ground calcium carbonate with a particle size of 400–500 mesh is more suitable as a precursor for the preparation of core-shell CaCO3/Al(OH)3 composites.

The recent use of cryoprotectant replacement method for solving the easy drying problem of hydrogels has attracted increasing research interest. However, the conductivity decrease of organohydrogels due to the induced insulating solvent limited their electronic applications. Herein, we introduce the Hofmeister effect and electrostatic interaction to generate hydrogen and sodium bonds in the hydrogel. Combined with its double network, an effective charge channel that will not be affected by the solvent replacement, is therefore built. The developed organohydrogel-based single-electrode triboelectric nanogenerator (OHS-TENG) shows low conductivity decrease (one order) and high output (1.02-1.81 W/m2), which is much better than reported OHS-TENGs (2-3 orders, 41.2-710 mW/m2). Moreover, replacing water with glycerol in the hydrogel enables the device to exhibit excellent long-term stability (four months) and temperature tolerance (-50-100 °C). The presented strategy and mechanism can be extended to common organohydrogel systems aiming at high performance in electronic applications.

The Ni-rich layered material LiNixCoyMzO2 (M=Mn or Al, x+y+z=1) plays a crucial role in LIBs and attracts much attention owing to its comprehensive advantages in terms of energy density, production cost, and environmental friendliness, leading to the development of LIBs and related energy-storage devices. However, Ni-rich layered materials are limited in certain aspects such as safety, life cycle, and application range, which fail to meet the requirements for application in the market entirely. Starting from the factors including cation mixing, phase transition, crackle, and so on, which cause the performance degradation of nickel-rich cathode materials, this paper analyzes the mechanism of their action, and summarizes the mutual transformation relationship between the factors. Cutting off this transition process may, like inhibiting these factors, help improve the performance of materials. At the same time, the research progress on the strategies and mechanisms to deal with these failure factors is summarized, and the role of simulation calculation in material design and mechanism demonstration is discussed. The purpose of this paper is to give an introduction to the related research results of nickel-rich layered cathodes in recent years and to help researchers understand the development status of this field in a timely and rapid manner.

Recently, niobium tungsten oxide has garnered considerable attention owing to its excellent Li-ion diffusion rate and prominent structural stability during charge–discharge cycles. Here, a cathode material (LiNi0.8Co0.1Mn0.1O2, NCM811) for Li-ion batteries is successfully coated with Li-ion conductive Li2.09W0.9Nb0.1O4 using a simple wet-chemical coating method followed by high-temperature sintering. A physicochemical phase analysis reveals that a 4–5-nm-thick coating with a Li2.09W0.9Nb0.1O4 crystal structure is evenly distributed on the surface of the cathode particles. Among cathodes coated with different amounts of material, the one coated with 0.5 wt% Li2.09W0.9Nb0.1O4 yielded the best overall performance, with a high discharge capacity of 136.8 mAh g−1 at 10 C and long-term cycling stability with a capacity retention of 91.7% after 100 cycles at 1 C. This excellent electrochemical performance can be attributed to the coating’s ability to prevent the impedance from increasing and the Li-ion diffusion coefficient from decaying. In addition, it protects the cathode from side reactions and stabilizes the structure during cycling.

LiNi0.8Co0.1Mn0.1O2 (NCM811) has a high potential for using as the cathode material for lithium–ion batteries (LIBs) for electric vehicles owing to its high energy density and low cost. However, its poor rate capability and cycling performance have significantly hindered its application. In this study, we successfully design a uniform magnesium oxide (MgO) coating on NCM811 via a wet-chemical coating followed by heat treatment using magnesium ethoxide [Mg (OEt)2] dissolved in ethanol as the Mg source. The effects of MgO coating on the surface states, crystal structure, and electrochemical performances of NCM811 cathode material are studied in detail. After 100 cycles, the capacity retention of MgO-coated NCM811 is 90.1% at room temperature at 1 C, whereas the pristine NCM811 is only 74.5%. Besides, the MgO-coated NCM811 delivers a better rate property than pristine NCM811. Prominent improvements in electrochemical performances are attributed to the fact that the formation of MgO coating layer helps to suppress deleterious side reactions, lower the overpotential on the surface, and facilitate lithium–ion diffusion.

Flexible lead-free (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3-0.2 mol%Y nanofibers (BCTZY NFs) were synthesized by electrospinning and their corresponding nanogenerators (NGs) with vertical alignments were fabricated. The low-temperature sintering properties of BCTZY NFs were investigated, to optimize their synthesis path and minimize the thermal energy consumption during the sintering process. The continuity, flexibility, and stability of the BCTZ-based NFs were improved by adding Y3+. Moreover, the temperature-evolved Raman spectra displayed a high Curie temperature of 280 °C for BCTZY NFs, which was far higher than that of about 90 °C for BCTZ-based ceramic bulks, owing to the discontinuous physical property of NFs. The dielectric, ferroelectric, and piezoelectric properties of the vertically aligned BCTZY NFs/PDMS were estimated and compared with those of BCTZ NFs/PDMS composites, to verify the advantages of vertical alignments and the donor doping effect of Y3+. Vertically aligned BCTZY NF-based NGs showed an average VOC of 3.0 V and ISC of 85 nA by finger tapping, suggesting their potential applications in tiny energy harvesting.

The advancement of wearable electronics and environmental awareness requires a wearable triboelectric nanogenerator (TENG) to feature the concepts of sustainability and environmental suitability. While most wearable TENGs are developed based on complex surface modification approaches to avoid the necessity of a physical spacer, herein a nanogap TENG is fabricated based on surface self-modified sustainable polymer films. Compared with poly(lactic acid) (PLA)-based and polycaprolactone (PCL)-based TENGs, the polybutylene succinate (PBS)-based TENG shows the highest output performance, representing up to 3.5-fold that of the reported TENGs based on biodegradable materials with a 0-4 mm spacer, due to the higher content of the ester group and surface roughness resulting from the surface self-modification. The nanogap device is demonstrated as a pressure/angle sensor with acceptable sensitivity for use in health monitoring. More importantly, the environmental suitability of the triboelectric films in air, water, and phosphate buffered saline systems indicates their stability in natural water and saline environments. Moreover, the antibacterial property of the triboelectric films indicates future applications in wearable and implantable electronics. This work demonstrates the potential applications of a biocompatible and environmentally stable TENG in wearable electronics and biomedical systems.

With the rapid development of wearable electronics, flexible and sensitive energy harvesters have recently attracted considerable attention. Herein, a novel piezo-triboelectric nanogenerator (PTNG) based on BCZT/PVDF-HFP composite nanofibers (BP-based NFs) is fabricated using silicone rubber as the negative triboelectric counterpart. The introduction of BCZT nanoparticles markedly improves both the piezoelectric and triboelectric properties of the BP-SG PTNG, where the output voltage and current density are 2.5–3 fold higher than those of pure PVDF-HFP PTNG. Owing to the uniform distribution of BCZT particles on the fiber surface via electrospinning, the maximum power density of the device reaches 161.7 mW m−2, representing 5.5-fold improvement compared to that of BaTiO3/PVDF-based composite PTNG. The device shows stable output for 1200 cycles and after three month storage and exhibits high sensitivity to minute body movements as proved by the output response in both two-electrode and single-electrode modes. This study demonstrates a novel approach to fabricate flexible PTNGs with simple structure and high sensitivity for use in self-powered wearable electronics.

BCZT-CuY/rGO/PDMS composites with excellent elasticity and flexibility, and their nanogenerators (NGs) with favorable electrical properties, were fabricated. The impact of rGO on the dispersion of BCZT-CuY, the mechanical properties of BCZT-CuY/rGO/PDMS, and electrical performance of BCZT-CuY/rGO-based NGs were systematically investigated. The results indicated that the distribution of BCZT-CuY in PDMS with added rGO was much more uniform than that without rGO. Moreover, its elastic modulus and elongation at the break increased to 4.6 MPa and 250%, respectively, with the introduction of rGO. Apart from a high d33 at the percolation threshold, the average VOC (1.36 V) and ISC (35nA) achieved by finger tapping BCZT-CuY/rGO-based NGs suggested their considerable potential in harvesting tiny energy.

Lead-free (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3-xwt%CuOywt%Y2O3 (BCZT-CuxYy) ceramics with high piezoelectricity were synthesized by the conventional solid-state reaction method. The role of Cu and Y (Cu/Y) in sintering, phase transition, and electrical properties of such ceramics was systematically studied. The results indicated that the sintering temperatures of BCZT-CuxYy decreased by at least 100 °C due to the low melting point of CuO. The promotion effect of Cu/Y on phase transition lied in the improvement of TC by 5–15 °C and the coexistence of O+T phase near room temperature. The contribution of Cu/Y to electrical properties was mainly ascribed to the grains growth, the formed oxygen vacancies and lattice distortions, and the donor doping effect of Y3+. Adding 0.10 wt% Cu2+ and 0.06 wt% Y3+ into BCZT dramatically improved the electrical properties as following: d33 = 552 pC/N, em = 10175, er = 4546, tanδ = 0.016, TC = 100 °C, kp = 0.475, Qm = 157.2, Pr = 10.82 μC/cm2 and EC = 2.33 kV/cm. A plausible mechanism was obtained to explain the reaction process and the favorable performances of BCZT-CuxYy. Co-doping Cu2+ and Y3+ into BCZT could be a promising method to improve and balance the sintering, phase transition, and electrical properties for potential practical applications of lead-free piezoceramics.

A chemical precipitation–thermal decomposition method was developed to synthesize Co3O4 nanoparticles using cobalt liquor obtained from the atmospheric pressure acid leaching process of nickel laterite ores. The effects of the precursor reaction temperature, the concentration of Co2+, and the calcination temperature on the specific surface area, morphology, and the electrochemical behavior of the obtained Co3O4 particles were investigated. The precursor basic cobaltous carbonate and cobaltosic oxide products were characterized and analyzed by Fourier transform infrared spectroscopy, thermogravimetric differential thermal analysis, X-ray diffraction, field-emission scanning electron microscopy, specific surface area analysis, and electrochemical analysis. The results indicate that the specific surface area of the Co3O4 particles with a diameter of 30 nm, which were obtained under the optimum conditions of a precursor reaction temperature of 30°C, 0.25 mol/L Co2+, and a calcination temperature of 350°C, was 48.89 m2/g. Electrodes fabricated using Co3O4 nanoparticles exhibited good electrochemical properties, with a specific capacitance of 216.3 F/g at a scan rate of 100 mV/s.

A reasonable and economic process to achieve the comprehensive utilization of waste from production of zirconium oxychloride would benefit sustainable development of zirconium industries and reduce environmental pollution. In this paper, wollastonite was prepared from spent caustic liquor and zirconium-containing silicon slag at low temperature. The effects of CaO/SiO 2 mole ratio, reaction temperature, reaction time, and rotation rate on the crystallization and morphology of wollastonite were systemically investigated. The optimal conditions for desilication were confirmed as a CaO/SiO 2 mole ratio of 1.0, a reaction temperature of 90 °C, a desilication time of 60 min, and a rotation rate of 200 r/min. Wollastonite was subsequently prepared by calcination of the obtained calcium silicate hydrate at 1000 °C for 1.0 h. The developed process achieved good performance of wollastonite and alkali liquor with a low silicate content, which met the standard of an industrial-grade product.

Owing to its potential to maximize the power output, hybrid energy harvesting technology has attracted more research interest. Boosting merits such as renewable energy sources and high output, hybrid photovoltaic-triboelectric nanogenerator (HPTNG) is considered as one of the promising power sources for next-generation smart electronics. To date, there is still a lack of a comprehensive review of the latest development and challenges of HPTNGs. Herein, we systematically summarize the recent advances of the hybrid photovoltaic-triboelectric energy-harvesting system. In particular, the structural flexibility and simplification of the hybridized device is described, followed by the detailed discussion from perspectives of the input mechanical energy sources, the output interaction between triboelectric nanogenerators and solar cells, as well as the functions and applications of the HPTNGs. Finally, the main challenges and perspective for the future development of HPTNGs are discussed.

Substituents can affect the partial charge distribution on porphyrin, and in tandem with the ion states in electrolyte, the charge transfer mechanism can be altered at catalytic interface. Three cobalt porphyrins with methyl phenyl, 2,1,3-benzothiadiazole (BTD) and BTD-triphenylamine (TPA) substituents at the 5,15-positions, nominated as CoPor, BTD-CoPor and TPA-BTD-CoPor, respectively, have been examined in oxygen reduction reactions (ORR) under alkaline condition. Reduced reduction potentials and enhanced response current densities were observed on the two substituent porphyrin-coated catalysts as compared to CoPor/C. Importantly, TPA-BTD-CoPor/C obtained slightly larger ORR current with less hydroperoxide anion generation yields than BTD-CoPor/C. We proposed that the electronic structure along with the induced partial charge effect caused the difference in ORR potential, while the electron-withdrawing property of BTD contributed to the increased response current. Though TPA unit still benefits the ORR performance, the more exposed cation orbitals on TPA that merit the acidic ORR activity was suggested to be ineffective in alkali condition. These findings demonstrate the importance of the induced intramolecular partial charges in affecting the catalytic process in alkali medium and point out the limitation in utilizing the structural merit of TPA in accelerating the interfacial charge transfer.

The automotive industry consumes a large amount of fossil fuels consequently exacerbating the global environmental and energy crisis and fuel cell electric vehicles (FCEVs) are promising alternatives in the continuous transition to clean energy. This paper summarizes the recent development of fuel cell technologies from the perspectives of the automobile industry and discusses current bottlenecks hindering commercialization of FCEVs. Current status of the fuel cell technology, policies and market prospect of FCEVs, as well as recent progress of FCEVs are reviewed. Polymer electrolyte membrane fuel cells constitute the mainstream and most mature fuel cell technology for automobile applications. Hybridization with an auxiliary battery system will greatly boost the dynamic response of FCEVs. Hydrogen FCEVs have entered the preliminary commercialization stage since 2015 and the market share of FCEVs is expected to grow at a high rate. Challenges encountered by commercialization of FCEVs and future outlook are also discussed. Future efforts are expected to focus on solving problems such as the high cost of fuel cell stack production and maintenance, insufficient hydrogen supply facilities, insufficient reliability, slow cold start, safety concerns, and immature energy management systems of FCEVs. This review serves as a reference and guide for future technological development and commercialization of FCEVs.

Zirconia fiber, with its resistance to ultra-high temperature, is irreplaceable in many applications. Herein, a technique combining the sol-gel method and electrospinning was used to fabricate uniform 1D zirconia nanofibers from zirconium polyacetate. A suitable heat treatment process was established, and the effects of spinning parameters and additives on the fiber morphology were investigated using XRD, SEM, TGA, and FTIR. The results showed that addition of silica effectively inhibited grain growth and reduced the grain size to 30–60 nm. By optimizing the electrospinning parameters and the sintering process, fine-grained tetragonal zirconia fibers of 400–700 nm diameter could be produced.

With the rapidly increasing health and environmental awareness, demands for wearable electronics are no longer limited to performance and design, but also safety, health and environment protection. Herein, a sustainable and shape-adaptable skin-like liquid single-electrode TENG (LS-TENG) is developed using aloe vera gel (AVG)@NaCl as the liquid electrode. As an effective network channel for charge transfer, the liquid electrode shows high conductivity and mobility, leading to a high current density that is 2.1–23 folds of reported LS-TENGs. Besides, the size effect of liquid electrode in LS-TENG is firstly investigated, upon which the output parameters are optimized. Consequently, AVG@1wt%NaCl-based LS-TENG shows the highest output reported for LS-TENG with VOC of 157.8 V, JSC of 44.2 mA/m2 and power density of 4.61 W/m2. Moreover, the device shows a high sensitivity to minute face expressions and is suitable for 2D or 3D-shape fabrication, indicating a great potential for use in wearable electronics, such as e-skin and health monitoring.

The direct preparation of LiNi0.8Co0.1Mn0.1O2 (LNCM811) cathode materials from the hydrochloric acid leaching of laterite are promising; however, there are Cl− ions and other impurities in the hydrochloric acid leaching solution, thereby limiting the commercial application of LNCM811. In this study, we compared the LNCM811 prepared from Cl−- and SO42−- ion precursor solutions, and observed that the existence of Cl− ions could result in agglomerate disjointed and the primary particles grew separately during the sintering process, further deteriorating the electrochemical performance. Therefore, the initial raw Ni/Co solid residues were washed with deionised water and leached with 25 wt% H2SO4 solution to obtain an enriched Ni/Co solution with SO42− anions. Furthermore, considerable impurities in the enriched Ni/Co solution caused primary particle separation during the sintering process and led to the LNCM811 having poor electrochemical properties. Therefore, it was further purified by extraction with Cyanex272 to obtain a pure NiSO4 solution. The impurities in the NCM811 precursor prepared from this pure NiSO4 solution were below standard limits, the corresponding lithiated cathode delivers an initial reversible capacity of 192.1 mAh g−1 at 0.1C with an initial Coulombic efficiency of 86.5%; it retains 85.1% of its capacity after 100 cycles at 1.0C in 2.8–4.3 V, thereby achieving the standard of commercial LNCM811. On this basis, combined with the previous research of our group, high-value utilisation of laterite for preparing cathode materials includes the following processes: hydrochloric acid leaching, preliminary purification, alkaline oxidation precipitation, conversion of the Cl− solution system to the SO42− ion solution system, extraction, solution-phase synthesis, and calcination. Moreover, compared with the conventional process of preparing NCM811 from metal sulfates, the cost saving through the proposed process was found to be approximately 265.8 $/ton.

Boron-bearing magnetite concentrate is typically characterized by low grade of iron and boron (wTFe = 51% – 54%, wR2O3 = 6%–8%), as well as the close intergrowth of ascharite phase and magnetite phase. A promising technology was proposed to separate iron and boron by coupling the direct reduction of iron oxides and Na activation of boron minerals together. The influence of Na2CO3 as additive on the direct reduction of boron-bearing magnetite was studied by chemical analysis, kinetic analysis, XRD analysis and SEM analysis. The results showed that the addition of Na2CO3 not only activated boron minerals, but also reduced the activation energy of the reaction and promoted the reduction of iron oxides. Besides, the addition of Na2CO3 changed the composition and melting point of non-ferrous phase, and then promoted the growth and aggregation of iron grains, which was conducive to the subsequent magnetic separation. Thus, the coupling of the two processes is advantageous.

In this work, FeCl3 solution was used as a lixiviant to leach Ni, Co, Mg, and Mn from saprolitic laterite ore. Investigation into the leaching of these metals and the precipitation of Fe in the lixiviant, found the optimal leaching conditions to be a temperature of 150 degrees C, a Fe concentration in the lixiviant of 178.9 g/L, a liquid to solid ratio (L/S) of 1.0, and a leaching time of 90 min. The kinetics of the leaching process was also discussed. Saprolitic ore with and without goethite seeds was leached using FeCl3 solution under identical conditions. X-ray diffraction (XRD) analysis, infrared spectrometry (IR), and mineral liberation analysis (MLA) were used to characterize the leached residues. The leaching mechanism was analyzed based on these results. (C) 2015 Elsevier Ltd. All rights reserved.

In the alkali fusion process for the production of zirconium oxychloride, the formation of the water insoluble by-product, Na2ZrSiO5, largely affects NaOH recovery and results in the formation of silicon slags. Thus, controlling Na2ZrSiO5 formation is necessary. In this paper, we studied the effects of roasting temperature, NaOH/zircon mole ratio, and particle size of zircon sand on Na2ZrSiO5 formation. The optimum reaction parameters, when the roasting time was 1 h, were as follows: >= 95 mu m average particle size of zircon sand, 6:1 NaOH/zircon mole ratio, and 750 degrees C roasting temperature. To avoid an uneven roasting temperature during alkali fusion, the use of a rotary kiln reactor is recommended. The amount of Na2ZrSiO5 was significantly decreased under these optimum conditions, and the content of Na2O was reduced from 7.049% to only 2.21% after three water-leaching cycles. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

This study investigated the performance of Amberlite IRC 748 resin in removing calcium ions from highly concentrated potassium chromate solution in a fixed bed column. The exchange capacity increased with initial calcium ion concentration and bed height but decreased as flow rate increased. Four different kinetic models, specifically the bed depth service time (BDST), mass transfer, Thomas, and Yoon-Nelson models, were applied to the experimental data to predict the breakthrough curves and determine the column parameters. The BDST model was extended to the prediction of service times of columns operated at different flow rates and influent concentrations; while the experimental and theoretical data points followed a similar trend, they deviated slightly from each other. The Thomas and Yoon-Nelson model predictions were in very good agreement with the experimental results for all the process parameters studied, indicating that they are suitable for use with these kinds of columns. (C) 2015 Elsevier B.V. All rights reserved.

In this study, pressure hydrochloric-add selective leaching was used to leach Ni and Co from saprolitic laterite ore on the basis of potential-pH diagrams constructed for Fe-Si-Cl-H2O and Ni-Si-Cl-H2O systems. The leaching of Ni, Co, Mg, Mn, and Fe was investigated under various conditions. The results showed that the optimal output was obtained under the following conditions: leaching temperature of 150 degrees C, HCl concentration of 350 g/L, liquid to solid ratio (I/s) of 1.0, and leaching time of 90 min. The saprolitic laterite and leached residue were characterized via X-ray diffraction analysis, infrared spectrometry, and mineral liberation analysis. The related acid leaching mechanism was analyzed based on the results, and the kinetics of the leaching process was discussed. The results of this study suggest that pressure hydrochloric-acid selective leaching is a viable method for efficiently leaching Ni from laterite ores. (C) 2015 Elsevier B.V. All rights reserved.

In this work, a two-step zircon method to produce zirconium oxychloride was introduced, and the alkali fusion technique with NaOH and water leaching process were investigated. The effects of the operating conditions on the decomposition of zircon were determined, and the optimal conditions are as follows: alkali/zircon mass ratio of 0.7 at the first step and 0.6 at the second step (0.7 + 0.6), fusion temperature of 700 °C and fusion time of 0.5 h at the first step and 0.5 h at the second step (0.5 + 0.5 h). Under these conditions, the decomposition alloy of zircon sand can reach 97.25 %. In the fusion process of zircon sand, the products of first step are mainly Na2ZrO3 and ZrSiO4, the products of second step are Na2ZrO3 and Na2SiO3, and the diffraction peaks of Na2ZrSiO5 are not observed. The conditions of water leaching process were investigated as well, and the optimal conditions are as follows: liquid–solid ratio of 5:1, leaching time of 0.5 h, leaching temperature of 50 °C and leaching three times. Under these conditions, the contents of leaching products SiO2 and Na2O are 3.51 % (40 % ZrO2) and 4.46 % (40 % ZrO2), respectively. The crystal phase structures of Na2ZrO3 and Na2SiO3 are formed in water leaching process.

Many of the impurities present in the hydrochloric acid leaching liquors obtained after the treatment of Ni laterite and serpentine ores can be removed in a preliminary purification step. However, Mn and Mg typically persist in the liquor. In addition, the liquor also contains Ni and Co. This paper describes the separation of Mn and Mg from Ni-Co chloride solutions by alkaline oxidation and acid leaching processes and the preparation of Ni-Co residues, MnO2, and MgO from the separated components. The effects of variables such as time, temperature, pH, and concentrations of NaOH, H2O2, and HCl on the reactive behaviors of the above metallic components are investigated. Under optimal conditions including a NaOH concentration of 5 wt.%, H2O2 concentration of 10 wt.%, HCl concentration of 10 wt.%, and oxidation pH of 9.0, the recoveries of Ni, Co, Mn, and Mg are nearly 100%, 93.07%, 93.76%, and 99.07%, respectively. The products of Ni-Co residues, MnO2, and MgO are suitable as raw materials for industrial applications. (C) 2015 Elsevier B.V. All rights reserved.

Atmospheric hydrochloric-acid leaching of nickel laterite can produce a leaching solution containing a large amount of Fe. To recover Ni and Co, Fe should be separated from the laterite-leaching solutions. In this study, hydrolytic distillation was used to remove Fe from the synthetic laterite-leaching solutions; Ni and Co remained as soluble chlorides in the solutions, while most Fe was removed as Fe2O3. The conversion of Fe, recovery of Ni and Co, recovery of HCI, and the concentration of HCI, were investigated under various conditions. The results showed that the optimal output was obtained under the following process conditions: the hydrolysis temperature was 170 degrees C, the pressure was 0.03 MPa, the water flow rate was 1.67 mL/min, and the hydrolysis duration was 2 h. The effects of impurities under the optimized conditions were also studied, showing that as the amount of metal chlorides increased, the conversion of Fe decreased. The residues were characterized by X-ray diffraction analysis and scanning electron microscopy with X-ray energy-dispersive spectroscopy. Using the results, a growth model of alpha-Fe2O3 (hematite) spheres from the synthetic laterite-leaching solutions was constructed. (C) 2015 Elsevier B.V. All rights reserved.

Illite/TiO2 composite pigments were prepared through hydrolysis of titanium sulfate on the surface of illite particles. Some factors that influence the coating process of TiO2 were investigated in single-factor tests, and the whiteness and oil absorption value of coating products were tested. With optimized coating conditions, the whiteness and oil absorption of illite/TiO2 composite pigments can reach to 95.73% and 31.35 g/100 g, respectively. The crystalline phases and surface morphology of the coating products were characterized by X-ray diffraction and scanning electron microscopy. In addition, the precipitated mechanism of anatase was investigated by X-ray photoelectron spectroscopy. The results showed that the microstructure of TiO2 coating on illite substrate was mainly anatase. The uniform and dense TiO2 layers were anchored to the surface of illite by forming Ti-O-Si bond. (C) 2014 Elsevier B.V. All rights reserved.

A chromium oxide green pigment was prepared by thermal decomposition of chromium hydroxide via hydrothermal reduction of a high concentration mixture of Na2CrO4 (300 g/L) using NaHCO3 as a mineralizer. The mineralizer effects on the hydrothermal process, conversion of chromate, properties of amorphous Cr(OH)(3), and color performance of Cr2O3 were investigated. Compared with sodium carbonate and urea, sodium bicarbonate significantly reduces the Na2CrO4 concentration and, consequently, improves the conversion of Na2CrO4 during the hydrothermal process. Additionally, homogeneous particles were obtained by adding NaHCO3. The changes in the amount of trapped water, oxygen chemisorption, and negative charge on the surfaces of chromium hydroxide particles caused by adding a mineralizer were analyzed using Fourier-transform infrared spectroscopy and zeta potential analysis. The Cr2O3 pigments were characterized using X-ray diffraction, scanning electron microscopy, and an automatic differential colorimeter. A good color performance by the Cr2O3 pigment, comparable to that of a commercial pigment, was obtained. (C) 2014 Elsevier Ltd. All rights reserved.

An innovative technology for processing saprolitic laterite ores from the Philippines by hydrochloric acid atmospheric leaching and spray hydrolysis is proposed. The factors that affect the hydrochloric acid atmospheric leaching of the laterite ores and spray hydrolysis of the atmospheric acid leach solution are investigated. Experimental results show that the leaching of Ni, Fe, and Mg is 98.9 wt%, 97.8 wt%, and 80.9 wt%, respectively, under optimal acid leaching conditions. The hydrolysis of Ni and Fe by the atmospheric acid leach solution approaches 100 wt% at the temperature range of 450–500 °C. Characterization results show that a serpentine mineral, nominally Mg3Si2O5(OH)4, is the major component and goethite, FeO(OH), is the minor one in the laterite ores. Treatment by hydrochloric acid atmospheric leaching breaks the mineral lattices of the laterite ores and makes amorphous silica the primary product in the atmospheric acid leach residue. The grade of Ni in the hydrolyzate increases to 4.55%. The hydrolyzate with high Ni content can be utilized for ferro-nickel production.

Accumulation of high-arsenic fly ash (HAFA) poses a serious environmental threat due to the toxicity of As and release of other heavy metals especially Cr. In this work, a novel graphite felt (GF) cathode modified with the nanoscale MoS2/reduced graphene oxide (rGO) heterojunction is prepared by blending with PTFE emulsion for efficient synergistic oxidative dissolution of As(III) and Cr(III) in HAFA. By taking advantage of the p-n junction characteristics of the heterojunction and appropriate hydrophobicity of the PTFE coating, the modified GF efficiently utilizes both dissolved O2 and gaseous O2 in the 2e− oxygen reduction reaction (ORR). Our theoretical assessment indicates that gaseous O2 adsorbs stably on sulfur vacancies and is reduced by electrons transmitted from rGO. Experimentally, the modified GF shows superior ORR catalytic activity as exemplified by a high peak current density of 8.41 mA cm−2 and onset potential of 0.53 V vs. RHE. OH generated by the Cr and Fe-triggered autocatalysis mechanism promotes oxidization of As(III) and Cr(III) in detoxification of HAFA resulting in 96.1% As removal as well as 70.74% Cr removal in 135 min. The modified GF with excellent stability and durability has immense industrial prospect in detoxification of HAFA and treatment of other types of As-containing hazardous wastes.

A green process for the production of chromate compounds from chromite ore was simulated using process simulation software. Firstly, the phase equilibria of the KOH-K2CrO4-H2O system were investigated to determine the feasible operating conditions for the separation of K2CrO4 from the KOH alkaline solution. The green process model of chromate production was developed and three cases with different concentrations of alkali solution were simulated based on several assumptions. The mass and energy balances in the three cases were simulated, showing that the energy consumption of the evaporation unit is the largest in the whole process. The simulation results provide important information for the implementation of this green chromate production process.

TiO2-coated illite composite pigments were prepared by hydrolyzing Ti(SO4)(2) on the surface of illite substrates and the products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), zeta potential analysis, and X-ray photoelectron spectroscopy (XPS), respectively. Density functional theory calculations of the energetic stability and electronic structure of illite, calcined illite, and TiO2-coated illite were used to analyze the chemical activity and bonding position between the anatase film and the illite particles. The results demonstrate that calcined illite is more suitable for metatitanic acid coating. Moreover, the surface of illite substrates is continuously coated with anatase and a chemical interaction could occur between the anatase film and the illite substrates. The whiteness, hiding power, and oil absorption value of the compound pigment are 95.73%, 97.55%, and 33.82 g/100 g, respectively. (C) 2014 Elsevier Ltd. All rights reserved.

The efficiency of silicon removal technology by acid leaching and flocculation during zirconium oxychloride octahydrate (ZrOCl2 center dot 8 H2O) production has been improved. The optimum conditions of acid leaching were found to be as follows: transiton material, 300 g; HCl (6 mol/L), 600 mL; leaching time, 4 h; and leaching temperature, 100 degrees C. The nonionic polyoxyethylene lauryl ether (AEO9) was adopted as the flocculant. The optimum flocculation conditions were found to be as follows: temperature, 40 degrees C; flocculant amount, 10 ml (concentration 1%); time, 1 h. The zirconium oxychloride solution after purification contained 36 ppm SiO2 and 160 g/L ZrOCl2. The polymerization and flocculation mechanisms of silicic acid were analyzed. Results of Fourier-transform infrared, scanning electron microscopy, nuclear magnetic resonance, and Brunauer-Emmett-Teller analyses showed the main transformation and properties of the products in the acid leaching and flocculation processes. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

A novel method was proposed for preparing oxychloride octahydrate by the two – step decomposition of zircon sand concentrate in sodium hydroxide system. The effect of decomposition temperature and NaOH – to – zircon mass ratio of each stage on the decomposition of zircon sand was investigated. The macrokinetics of the two – step decomposition process was also examined. The experimental date showed that the shrinking core model with diffusion through the residual layer is most applicable for the first step decomposition process with the apparent activation energy of 42.9 kJ/mol, but the second step process was controlled by chemical reaction with the apparent activation energy of 30.1 kJ/mol.

Chromium hydroxide (CH) was prepared by the reduction of purified sodium chromate using starch. CH was then used to prepare chromium oxide (Cr2O3). Results of thermogravimetric, X-ray diffraction, Fourier transform infrared spectroscopy, and chemical analyses suggested that a small amount of the initial Cr(VI) content speeds up the oxidation and reduction reactions, thereby promoting the purity and crystallization of Cr2O3. Cr(VI) in CH induced the evolution of CH and the formation of Cr(VI) containing compounds including CrO3, NaCr(CrO4)(2), Cr3O8, and Cr5O12 at low sintering temperature. Furthermore, homogeneous Cr2O3 nanoparticles with 99 % purity and particle size of 50 nm were obtained.

Li- and Mn-rich materials have high capacities but serious voltage attenuation, whereas Ni-rich materials LiNi0.8Co0.1Mn0.1O2 (NCM) have good rate characteristics but poor stabilities, and they readily to oxidize organic electrolytes. The core–shell strategy with Ni-rich materials as the core and Li- and Mn-rich materials as the shell was expected to balance these merits and drawbacks. In this work, simple and concentration-gradient Li- and Mn-rich shell were successfully synthesized on NCM and critically compared. As expected, a distinct core–shell interface was observed for the simple core–shell cathode, which causes the shell to crack during cycling and exhibits worse electrochemical performance than the single Li- and Mn-rich cathodes and Ni-rich cathodes. In contrast, the fabricated concentration-gradient core–shell cathode shows the uniform fusion of the core and shell at the atomic level, and the overall electrochemical performance is far superior to that of the simple core–shell and pristine cathodes. In addition, it delivers an initial reversible capacity of 226.6 mAh g−1 at a C-rate of 0.1C and 120.2 mAh g−1 at 10.0C, and it retains 86.9% of its capacity after 100 cycles to 4.6 V at 1.0C. Differential capacity versus potential (dQ/dV versus V) and EIS analyses show that the concentration-gradient core–shell cathode has a stable impedance and very stable average voltage. Obviously, the concentration-gradient coating of the Li- and Mn-rich shell can maximize the merits of the core and shell.

Owing to the limited deformability and restricted scalability of traditional triboelectric nanogenerator (TENG), liquid single-electrode TENG based on graphene oxide dispersion (GO LS-TENG) was developed in this study. The device exhibits high short-circuit current density of 18.61 mA m−2 at contact frequency of 3 Hz, being much higher than that of reported LS-TENG based on NaCl solution (1.8 mA m−2, 2.3 Hz) and liquid metal (8.6 mA m−2, 3 Hz). Moreover, its maximum power density can reach 4.97 W m−2 (1.99 mW, 3 Hz), which is higher than that of a reported single-electrode TENG based on GO solid electrode (3.13 W m−2, 5 Hz). On palm tapping the device, 87 green LEDs connected in series can be lit up. Robustness, durability and reproducibility tests show high stability, sensitivity, and potential use of this device in wearable electronics. This work demonstrates a novel approach to fabricate LS-TENG with simple structure, high output and high sensitivity for use in highly flexible and deformable wearable devices.

The water leaching and transition process in manufacturing zirconium oxychloride octahydrate was examined. Results from X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectra showed that most of the soluble sodium silicate was dissolved and the residue hydrolyzed into H2SiO3 during the water leaching process. In addition, Na+ from sodium zirconate (NaZrO3) in the interlayer was removed during the first and second water leaching and the in-host layer was distinguished in the third water leaching. This process resulted in the hydrolysis of NaZrO3 into ZrO(OH)(2). Results from the scanning electron microscopy (SEM), FT-IR spectra, nuclear magnetic resonance (NMR) and XRD of the transition process showed the main reaction and properties of the products at different pH values. Na2ZrSiO5 reacted with HCl at pH=7, producing ZrO(OH)(2) SiO2 and NaCl. ZrO(OH)(2) SiO2 partially reacted with HCl, forming ZrOCl2 and H2SiO3 with a decrease in pH. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

The characterization and atmospheric hydrochloric acid leaching of a limonitic laterite from Indonesia were investigated in the current paper. The mineral and chemical compositions of the laterite were studied by X-ray diffraction (XRD) analysis, optical microscopy, scanning electron microscopy/X-ray energy dispersive spectroscopy (SEM/EDS), carbon/sulfur (C-S) analysis, and Fe(II) content titration. The laterite mainly contained goethite, siderite (similar to 16.6 wt.%), chrysotile, and magnetite (similar to 14.6 wt.%); Ni was incorporated in all major minerals. Complete leaching of the host minerals in hydrochloric acid was investigated, given that economical regeneration of the acid by hydrolysis was possible. Atmospheric leaching experiments were carried out to investigate the effect of acid-ore ratio (a/o), liquid-solid ratio (l/s), leaching temperature and time on the leach recovery of Ni (95.1%), Co (99.0%), and Fe (94.6%). Siderite and chrysotile in the ore were highly leachable; goethite dissolved in a wide range of a/o; magnetite and maghemite were moderately active. (C) 2012 Published by Elsevier B.V.

Precursors of chromium oxide (p-Cr2O3) were prepared by reducing hexavalent chromium in the presence of sodium carbonate solution under hydrothermal conditions. Methanal was used as the reductant, and carbon dioxide was the acidulating agent. The influences of reaction temperature, initial pressure of carbon dioxide, isothermal time and methanal coefficient on Cr(VI) reduction were investigated. Experimental results showed that Cr(VI) was reduced to Cr(III) with a yield of 99%. Chemical titration, thermogravimetry (TG), X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM) were used to characterize the p-Cr2O3 and Cr2O3. The series of p-Cr2O3 were found to be multiphase even if they presented different colors, from gray green to lavender. After these p-Cr2O3 samples were calcined, the product of rhombohedral Cr2O3 with a purity of 99.5wt% was obtained.

Highly ordered submicron spherical Fe-MCM-48 was successfully synthesized by a mixed surfactant method using cheap water glass as silica source. The gyroid like structure of MCM-48 was captured by a TEM image for the first time, and it was corresponded well to the previous simulated gyroid model. A tentative mechanism of homogenization cooperative process involving the Helmholtz double electrical layer was purposed. After the loading of metal Ag, the resulting Ag/Fe-MCM-48 catalyst showed good catalytic performance in the catalytic combustion of benzene.