2H2O Particles Research Articles

Conversion-type anode chemistry with interfacial compatibility toward Ah-level near-neutral high-voltage zinc ion batteries.

High-voltage aqueous zinc ion batteries (AZIBs) with a high-safety near-neutral electrolyte is of great significance for practical sustainable application; however, they suffer from anode and electrode/electrolyte interfacial incompatibility. Herein, a conversion-type anode chemistry with a low anodic potential, which is guided by the Gibbs free energy change of conversion reaction, was designed for high-voltage near-neutral AZIBs. A reversible conversion reaction between ZnC2O4·2H2O particles and three-dimensional Zn metal networks well-matched in CH3COOLi-based electrolyte was revealed. This mechanism can be universally validated in the battery systems with sodium or iodine ions. More importantly, a cathodic crowded micellar electrolyte with a water confinement effect was proposed in which lies the core for the stability and reversibility of the cathode under an operating platform voltage beyond 2.0V, obtaining a capacity retention of 95% after 100 cycles. Remarkably, the scientific and technological challenges from the coin cell to Ah-scale battery, sluggish kinetics of the solid-solid electrode reaction, capacity excitation under high loading of active material, and preparation complexities associated with large-area quasi-solid electrolytes, were explored, successfully achieving an 88% capacity retention under high loading of more than 20mg cm-2 and particularly a practical 1.1 Ah-level pouch cell. This work provides a path for designing low-cost, eco-friendly and high-voltage aqueous batteries.

Effect on Rotation Speed on Thermal Dehydration Characteristics of Waste Gypsum Particles in a Constant Volume Rotary Vessel by Heating.

This study examined the thermal dehydration characteristics of CaSO4∙2H2O in a constant-volume rotary vessel. The experiment used CaSO4∙2H2O particles obtained from the crushed waste gypsum board. The particle size ranged from 850 to 2000 μm, and the experiment was carried out at varying rotation speeds of 1, 10, and 35 rpm, with the vessel temperature heated to 180 °C. Temperature and pressure inside the vessel were measured simultaneously using the thermocouple and the pressure sensor. The XRPD measurement analyzed the transition of CaSO4∙2H2O after the heating of particles. The result showed that the temperature growth rate was similar for high rotation speeds of 10 and 35 rpm, while periodic temperature changes occurred at the low rotation speed of 1 rpm. A distinguishing flow pattern was observed at the low rotation speed, and the particles inside the vessel collapsed periodically downward. This particle behavior was related to the temperature distribution of the rotation speed of 1 rpm. Additionally, the pressure in the vessel increased rapidly at higher rotation speeds. This trend indicates the desorption of the crystal water of CaSO4∙2H2O due to the increasing temperature in the case of high rotation speed. Also, the XRPD measurement results showed the appearance of CaSO4∙0.5H2O under the higher rotation speed conditions, and the mass fraction of CaSO4∙0.5H2O increased with the rotation speed. Overall, the present study suggests that rotation speed plays a crucial role in determining the heat conduction and heat transfer of particles in a constant-volume rotary vessel.

Recovery of iron from titanium white waste for the preparation of LiFePO4 battery

The recovery of iron from by-product ferrous sulfate in titanium white industry to prepare battery-grade FePO4 represents a promising approach to address the solid waste disposal issue while simultaneously providing a precursor for new energy battery. However, a critical challenge lies in the elimination of impurities during the purification and synthesis process to prevent decrease in electrochemical performance of the product. In this work, we propose a simple, clean and cost-effective route based on Al/Ti precipitation purification, followed by selective synthesis of FePO4·2H2O with coexisting divalent metal ions. The results demonstrate precipitation efficiencies of 98.3% and 99.9% for Al and Ti, respectively, and only 1.3% loss of iron under the optimal conditions during the purification separation process. The contents of impurity in the synthesized FePO4 from waste ferrous sulfate met the battery-grade standard. Furthermore, the synthesized LiFePO4 materials exhibited comparable electrochemical performance with that of commercial LiFePO4. In addition, the growth mechanism of FePO4·2H2O particles under high temperature and high acid environment was clarified, which was dominated by surface nucleation. This work provides a guidance for the utilization of iron resource from waste ferrous sulfate to prepare battery-grade LiFePO4, and may promote the recycling industries and clean production strategies in titanium field.

Production of Graphene/Inorganic Matrix Composites through the Sintering of Graphene Oxide Flakes Decorated with CuWO4·2H2O Nanoparticles.

There is growing interest in graphene-reinforced inorganic matrix composites, but progress in this field is far behind that of polymer matrices due to difficulties in the processing of carbon materials in aggressive sintering environments, including oxidation and solubility in the host matrix. Copper-tungsten matrices are of particular interest in the power switching field but are difficult to produce due to the mutual insolubility of metals and poor wetting. Herein, composites were produced by decorating graphene oxide flakes with 8 nm diameter CuWO4·2H2O nanoparticles and then sintering them to form the final shape. The oxide nanoparticles were found to self-assemble into platelets on the surfaces of graphene flakes. Upon sintering, the presence of graphene was found to change the grain morphology from elongated needles to a polyhedral shape. It was found that, despite the nanosize of the CuWO4·2H2O particles used, the sintering conditions did not reduce the matrix to a pure metal; the sintered composites were found to be of mixed phase with copper tungstate and copper oxide present. Raman spectroscopy indicated that the graphene oxide became hydrogenated during the sintering process as a result of the reducing hydrogen atmosphere used.

Mitigating soil salinity stress with titanium gypsum and biochar composite materials: Improvement effects and mechanism

Titanium gypsum and biochar are considered effective amendments for mitigating soil salinity stress. However, the knowledge is inadequate regarding their efficiency and application as an improvement. In this study, TG-B composite was prepared by using industrial by-products titanium gypsum and biochar as raw materials and then modified by ball milling method, to characterize its microscopic characteristics and explore the improvement effect on saline-alkali soil and plant growth. Besides, we explored the mechanism of TG-B in improving saline-alkali soil and the dynamic balance of the solution reaction process. Our results showed that the CaSO4·2H2O particles in TG-B were finer, dispersed evenly, and contacted fully with soil gelatinous particles, which was more conducive to the improvement of saline-alkali soil. The results of TG-B with different ball milling ratios and different materials dosages indicated that the application rate of TG-B was 5%, and the optimum ratio of TG-B was TG: B (mass ratio) = 10:1, with the best soil improvement effect. The pot experiment proved that the indicators of indicating soil salinity such as pH, EC, SAR, and soluble Na+ decreased by 20.74%, 77.24%, 68.77%, and 44.70%, respectively, thus playing a good role in improving saline-alkali soil. In addition, pot experiments demonstrated that compared with the control group, the soil porosity and soil moisture content in the TG-B group increased by 15.95% and 38.71%, respectively, and further improve the structure and diversity of soil bacterial community when compared with titanium gypsum and biochar alone. Finally, the application of TG-B promoted the germination and growth of rice significantly through the synergistic effects of composite material components. These results all suggested that the application of TG-B was an effective strategy to improve soil salinity and promote plant growth. Therefore, it might provide new insights into the utilization of solid waste resources to improve saline-alkali lands.

Operando Imaging of Crystallinity-Dependent Multicolor Thermochromic Processes for Single Hydrated Hybrid Perovskite Particles.

The thermochromic properties of hydrated metal halide perovskites (MHPs) are promising for applications in smart windows, solar cells, optical sensors, and information storage. Traditional ensemble characterization methods always study the averaged thermochromic activity, lacking the accurate structure-activity correlation. Here we utilize dark-field microscopy (DFM) to in situ image the thermochromic processes of single isolated hydrated hybrid perovskite (CH3NH3)4PbI6-xClx·2H2O (MA4PbI6-xClx·2H2O) microparticles. The thermal-induced dehydration transition is demonstrated to alter the color of single MA4PbI6-xClx·2H2O particles. Operando single-particle mapping results reveal the significant intra- and interparticle variations of thermochromic behaviors, yielding unexpected single or multistep multicolor thermochromic processes. These phenomena are confirmed to be governed by the crystallinity of single MA4PbI6-xClx·2H2O particles that results in distinct composition-dependent bandgaps and thermal decomposition pathways. The present work highlights the important role of single-particle imaging for resolving the intrinsic thermochromic characteristic of hydrated MHPs, therefore opening a way for rational design of stimuli-responsive materials.

Preparation of Micro-Nano-Structured FePO4·2H2O for LiFePO4 Cathode Materials by the Turbulent Flow Cycle Method.

The micro–nano-structured FePO4·2H2O was prepared from mixed solution of FeSO4 oxidized in diluted H3PO4 with H2O2 and NaOH solution in the turbulent flow cycle state at 90 °C. The resulting products were characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Constant current charge/discharge tests were adopted to investigate the electrochemical performance and the rate capability (from 0.1C to 5C) of the carbon-coated LiFePO4 composite materials prepared from the micro–nano-structured FePO4. The carbon-coated LiFePO4 composite materials deliver a high specific discharge capacity of 153.7 mAh·g–1, exhibit excellent cycle performance with 98.6% of the capacity retained after 30 cycles. This study demonstrates that the turbulent flow cycle method may be an economical and effective method for industrial production of fine and uniform micro–nano-structured FePO4·2H2O particles for LiFePO4 cathode materials for Li-ion batteries.

Synthesis and characterization of mono-dispersion LiNi0.8Co0.1Mn0.1O2 micrometer particles for lithium-ion batteries

LiNi0.8Co0.1Mn0.1O2 cathode material for lithium-ion battery exhibits high capacity, but it suffers from interfacial side reactions and structural/thermodynamic instability, which leads to capacity reduction and safety problems. Cubic brick (Ni0.8Co0.1Mn0.1)C2O4·2H2O particles with micron size are synthesized by co-precipitation method. The oxalic precursor is sintered with lithium hydroxide to obtain cubic mono-dispersion LiNi0.8Co0.1Mn0.1O2 micrometer particles. Structural stability, cycling performance, rate capability and compacting density of the cubic mono-dispersion material are investigated. Conventional spherical and irregular mono-dispersion LiNi0.8Co0.1Mn0.1O2 are also prepared for comparison. The results reveal that the cubic mono-dispersion LiNi0.8Co0.1Mn0.1O2 dramatically enhances the structural stability and cycling performance at a little cost of capacity and rate capability.

Eco-friendly leaching of rubidium from biotite-containing minerals with oxalic acid and effective removal of Hg2+ from aqueous solution using the leaching residues

Efficient leaching of valuable metal resources from minerals and comprehensive utilizations of the leaching residues are extremely important for the sustainable use of mineral resources and reducing the environmental pollution. In this study, rubidium was leached from biotie-containing minerals with oxalic acid and the leaching residues were used to remove Hg2+ from aqueous solution. Results showed that the leaching efficiency of rubidium was 96.54% at 90 °C when oxalic acid concentration was 3 mol/L after reaction of 120 min. More than 75% iron were reserved in the leaching residues, which was favorable for the subsequent extraction of rubidium from leachate. It was found that the leaching residues could efficiently remove Hg2+, and the Hg2+ removal efficiency reached to 97.59% at initial concentration of 100 mg/L and pH of 2. The maximal Hg2+ removal capacity of the leaching residues was identified as 357.14 mg/g, and kinetics and thermodynamics results showed that the removal of Hg2+ was mainly depended on chemi-sorption and monolayer adsorption. XRD and SEM results of these residues suggested that a large number of 10 nm FeC2O4•2H2O particles were formed on the layered silica, and mesoporous structure was observed from the BET analysis. HAADF-STEM results indicated that a new rod-like morphology was formed and most of the adsorbed mercury existed in this structure after reaction with Hg2+ solution, which was identified as HgC2O4. The Hg2+ removal involved in ion exchange, reducing-oxidation and adsorption. It was concluded that this new method can efficiently realize the comprehensive utilization of Rb-bearing minerals.

Crystal morphology control of synthetic giniite for enhanced photo-Fenton activity against the emerging pollutant metronidazole

Metronidazole (MNZ) is a recalcitrant antibiotic with toxic and carcinogenic effects in aquatic environments. In this work, Fe5(PO4)4(OH)3·2H2O (giniite) particles were synthesised with three different alkaline cations (Li+, Na+ and K+) and used as Fenton catalysts for MNZ removal. It is shown that the addition of different cations during the hydrothermal synthesis process promote different morphologies from asterisk-like to flower-like and branches-like, maintaining the crystalline structure of pure giniite. The photo-Fenton activity of these particles was then evaluated through the degradation of MNZ under sunlight radiation for 9 h. The results indicate that the alkaline cation has a predominant role in the photo-Fenton efficiency, as demonstrated by the superior degradation efficiencies of Na@giniite particles (91.2% and 72.5% with giniite concentration of 0.2 g L−1 and 0.07 g L−1, respectively), related with its high surface area (10.7 m2 g−1). Thus, it is demonstrated the suitability of Na@giniite particles as Fenton catalyst for MNZ removal from water.

Layered Zinc Hydroxide Dihydrate, Zn5(OH)10·2H2O, from Hydrothermal Conversion of ε-Zn(OH)2 at Gigapascal Pressures and its Transformation to Nanocrystalline ZnO.

Layered zinc hydroxides (LZHs) with the general formula (Zn2+)x(OH–)2x−my(Am–)y·nH2O (Am– = Cl–, NO3–, ac–, SO42–, etc) are considered as useful precursors for the fabrication of functional ZnO nanostructures. Here, we report the synthesis and structure characterization of the hitherto unknown “binary” representative of the LZH compound family, Zn5(OH)10·2H2O, with Am– = OH–, x = 5, y = 2, and n = 2. Zn5(OH)10·2H2O was afforded quantitatively by pressurizing mixtures of ε-Zn(OH)2 (wulfingite) and water to 1–2 GPa and applying slightly elevated temperatures, 100–200 °C. The monoclinic crystal structure was characterized from powder X-ray diffraction data (space group C2/c, a = 15.342(7) Å, b = 6.244(6) Å, c = 10.989(7) Å, β = 100.86(1)°). It features neutral zinc hydroxide layers, composed of octahedrally and tetrahedrally coordinated Zn ions with a 3:2 ratio, in which H2O is intercalated. The interlayer d(200) distance is 7.53 Å. The H-bond structure of Zn5(OH)10·2H2O was analyzed by a combination of infrared/Raman spectroscopy, computational modeling, and neutron powder diffraction. Interlayer H2O molecules are strongly H-bonded to five surrounding OH groups and appear orientationally disordered. The decomposition of Zn5(OH)10·2H2O, which occurs thermally between 70 and 100 °C, was followed in an in situ transmission electron microscopy study and ex situ annealing experiments. It yields initially 5–15 nm sized hexagonal w-ZnO crystals, which, depending on the conditions, may intergrow to several hundred nm-large two-dimensional, flakelike crystals within the boundary of original Zn5(OH)10·2H2O particles.

An innovative method to enhance manganese and ammonia nitrogen leaching from electrolytic manganese residue by surfactant and anode iron plate

Electrolytic manganese residue (EMR) contains a lot of manganese (Mn2+) and ammonia nitrogen (NH4+-N), which can cause environmental pollution. In this study, surfactant and anode iron plate were used to synergistically enhance NH4+-N and Mn2+ leaching from EMR. The Characteristics of EMR, Mn2+ and NH4+-N leaching mechanism, and the leaching test were systematically studied. The results showed that the leaching efficiencies of Mn2+ and NH4+-N were 89.4% and 65.9%, respectively, when the current density was 20 mA/cm2 and iron as the anode plate, the mass of H2SO4 was 13 wt%, solid-to-liquid ratio of 1:5 at 20 °C reacting for 120 min. In addition, when the surfactant concentration of tetradecyl trimethylammonium chloride (TTC) was 100 mg/L, the leaching efficiency of Mn2+ and NH4+-N in EMR respectively increased from 89.4% to 97.1% and from 65.9% to 98.4% by adding electric field. The leaching efficiencies of Mn2+ and NH4+-N were 28.5% and 93.7%, respectively, which was higher than that attained under the same condition without an electric field and TTC surfactant. Meanwhile, electric field changed the movement and charge distribution of charged particles on the surface of SiO2 and CaSO4·2H2O particles and released soluble compound salt containing Mn2+ and NH4+-N. TTC surfactant also improved the hydrophilic and hydrophobic properties of the EMR surface and promoted the wetting ability of the particles and the leaching of Mn2+ and NH4+-N. This study shows that TTC surfactant and anode iron plate can enhance NH4+-N and Mn2+leaching from EMR.

Hydrogen production by aluminum corrosion in aqueous hydrochloric acid solution promoted by sodium molybdate dihydrate

Recycled aluminum alloys corrosion system was studied for hydrogen production in 1.4 M HCl solution at low temperature, 333 K. Molybdate ions were used as corrosion promoter. Commercial Na2MoO4·2H2O was tested, varying its concentration (0–0.036 M) in order to analyze the promoter effect in H2 production. Moreover, Na2MoO4·2H2O particles were synthesized via sonochemical method and by ultrasonic method. Later, synthesized promoters were tested in order to analyze the effect of their physicochemical properties in H2 production. Gas composition produced during the reaction was analyzed by gas chromatography. Results showed that reaction rate was notorious affected by molybdate ions concentration. The highest hydrogen volume and the greatest reaction rate obtained was with the use of 1050 aluminum foil alloy with very low promotor concentration (0.004 M), becoming, therefore, a low-cost process for high purity hydrogen production.

Ferrous-cupric oxalate hydrate combined with multiwalled carbon nanotubes composite anodes for lithium-ion batteries

Ferrous-cupric oxalate hydrate/multiwalled carbon nanotubes composite was prepared by solvothermal method and self-assembly technique. The structural and morphological characterization show that the CuC2O4·yH2O with three-dimension spherical shape is uniformly dispersed among the microrod-liked FeC2O4·2H2O particles embedded by carbon nanotubes. Cu nanoparticles fabricated in first few cycles and carbon nanotubes provide a high conductivity, enhance electrical path for electrochemical reaction and improve the activity of complex nanocomposites, thus resulting in good lithium storage performance: 530 and 482 mAh g−1 at current densities of 0.5 and 2 A g−1 after 200 cycles. This unique design can shorten the preparation process, completely solve the decomposition of oxalate matrix and improve the homogeneity of synthetic materials.

Preparation of flaky dihydrate zinc oxalate particles by controlled chelating double-jet precipitation

Well-dispersed flaky ZnC2O4·2H2O particles were synthesized via a controlled double-jet precipitation process from the relatively concentrated solutions of Zn(NO3)2 (0.05 mol/L) and Na2C2O4 (0.06 mol/L) in the presence of sodium citrate. The effects of concentration of the reactants, reaction time, pH values and feeding rates on the size and shape of the final particles are investigated. It was found that as-prepared dihydrate zinc oxalate particles are formed by aggregation of tiny microsized subunits, and the feeding rate as well as the citrate concentration is quite key to the morphological evolution of the hydrate zinc oxalate particles. Based on experimental results and the thermodynamic equilibrium calculation, it is confirmed that the presence of citrate ligand plays essential roles to the whole precipitation process, which may play the multiple roles of controllable release of zinc ions, crystal habit tunning agent, and dispersing surfactant. The controllable synthesis idea of well-dispersed particles in present research work has the potential of extensive application in the preparation of other similar particles.

Polyethylene Glycol for LiFePO4/C Composites Preparation: Large or Small Molecular Weight

Olivine LiFePO4 is challenged by its poor electronic and ionic conductivities for lithium-ion batteries. Polyethylene glycol (PEG) has been applied for LiFePO4 preparation by different research groups, but there is no consensus on the influence of the mean molecular weight of PEG on the structure and electrochemical performances of LiFePO4/C composites. In this work, LiFePO4/C composites were prepared by using micronsized FePO4·2H2O powder as starting material, PEG (mean molecular weight of 200, 400, 4000 or 10000) and citric acid as complex carbon source. The structure and electrochemical performances of LiFePO4/C composites would be decided considerably by the mean molecular weight of PEG, and the sample using PEG200 exhibited the least inter-particle agglomeration, the smallest charge transfer resistance and the highest discharge capacity. A probable growth mechanism is also proposed based on SEM images and electrochemical results: with the assistance of citric acid, PEG molecule with small molecular weight tends to cover one or only a few micron-sized FePO4·2H2O particles, significantly suppress the agglomeration of primary LiFePO4 particles and thus result in uniform particle-size distribution and carbon coating.

Self-assembly of red-blood-cell-like (NH4)[Fe2(OH)(PO4)2]·2H2O architectures from 2D nanoplates by sonochemical method

Red-blood-cell-like (RBC-like) (NH4)[Fe2(OH)(PO4)2]·2H2O architectures assembled from 2D nanoplates are successfully synthesized via a facile sonochemical method. XRD measurement indicates that the as-prepared sample is well crystallized with a monoclinic structure. The morphology of the sample is characterized by SEM analysis, which shows that the (NH4)[Fe2(OH)(PO4)2]·2H2O particles exhibit a unique biconcave red blood cell morphology with an average diameter of 4um and thickness of 1.5um. The detailed time-dependent experiments are conducted to investigate the morphological evolution process. It reveals that the ultrasonic time is crucial to the morphology of the products, and the RBC-like (NH4)[Fe2(OH)(PO4)2]·2H2O proceeds in steps of crystallization, formation of thin plates, and the subsequent self-assembly. Compared to the available methods that are typically time-consuming and complicated, this smart sonochemical strategy proposed herein is efficient and simple. Moreover, these obtained special RBC-like architectures will be more fascinating for application in many areas.

Preparation and microwave absorbing property of porous FeNi powders

Porous FeNi powders with particle size of 1μm were successfully prepared by two steps in this paper. First, Fe0.5Ni0.5C2O4·2H2O particles with uniform size distribution and morphology were obtained by an oxalate precipitation process. Second, the porous FeNi powders were prepared by thermal decomposition of the oxalate precursor at 450°C for 30minina N2/H2mixedatmosphere. The electromagnetic (EM) parameters of FeNi (30wt%)/paraffin composite were measured in 2–18GHz, and the reflection loss (RL) values were calculated based on the transmission line theory. The results show that the bandwidth of RL<−10dBreaches 2.57GHzwhen the composite thickness is 2.0mm, and the minimum RL reaches −52.58dBat 6.82GHzwith a composite thickness of 3mm.

Morphology-controlled synthesis and photocatalytic properties of K1.9Na0.1Ta2O6 2H2O

The controllable synthesis of tantalate K1.9Na0.1Ta2O6 2H2O has been successfully achieved by a two-step technique, namely, the molten salt and hydrothermal methods, at a low temperature. By simply varying the KOH concentration in the hydrothermal process, K1.9Na0.1Ta2O6 2H2O particles with spherical, cuboctahedral, and durian-like morphologies were synthesized. The photocatalytic activity of the obtained samples for the degradation of rhodamine B was studied under ultraviolet light, which indicates that the photocatalytic properties of the samples are highly dependent on their morphologies. The K1.9Na0.1Ta2O6 2H2O nanospheres, with rough surfaces and the highest specific surface area, exhibit the best performance. The present work provides a unique approach for the controlled synthesis of tantalate photocatalysts, which are difficult to achieve through other synthetic approaches.

Improved electrochemical properties of LiFePO4/graphene/carbon composite synthesized from FePO4·2H2O/graphene oxide

LiFePO4/graphene/carbon composite (LFP/G/C) was synthesized by in-situ precipitation of FePO4·2H2O/graphene oxide composite (GO–FePO4·2H2O) and solid state reaction to form LFP/C using Li2CO3 as the lithium resource as well as reduce GO to graphene. SEM results show that a great amount of FePO4·2H2O particles are grown on the GO sheets in GO–FePO4·2H2O. From the TEM and HRTEM results, an effective electronic conducting network on LiFePO4 particles is formed by both graphene and conductive carbon in the LFP/G/C, which can deliver a discharge capacity of 118.8mAhg−1 even at high rate of 10C and show a capacity decay rate of ~2.3% after 120 cycles.