Liquid-phase Co-precipitation Method Research Articles

The influence of Nano-composite metal oxides on the thermal decomposition performance of RDX

Abstract In order to investigate the effect of nano-composite metal oxides on the thermal decomposition performance of hexogen (RDX), this study prepared nano nickel-iron (NFO), nickel-cobalt (NCO), and nickel-iron-cobalt (NFCO) composite oxides by liquid-phase co-precipitation method. The precursor of Prussian blue analogs was synthesized and then calcined in air at 600°C. The addition of nano nickel-iron (NFO), nickel-cobalt (NCO), and nickel-iron-cobalt (NFCO) composite oxides to RDX has a significant impact on its thermal decomposition process. The peak exothermic temperatures were delayed by 8.4°C, 8.5°C, and 8.3°C, respectively, after adding the nano-composite metal oxides, and the heat release also increased to a certain extent. Among them, the addition of NCO nano-composite metal oxides had the greatest impact on the exothermic peak temperature of RDX, while the addition of NFCO nano-composite metal oxides resulted in the largest increase in heat release. This indicates that the addition of NFO, NCO, and NFCO to RDX altered the thermal decomposition reaction process to some extent.

Dispersant-assisted preparation of ultra-fine HfB2 powder

Hafnium boride (HfB2), as an ultra-high temperature ceramic, has been extensively employed in the aerospace field due to its high melting point and excellent ultrahigh-temperature oxidation resistance. Despite its outstanding performance, the development of the HfB2 for practical applications remained limited by its low-quality production including high oxygen content, large particle size and high agglomeration. In this work, a series of dispersants are adopted for reducing the particle size and suppressing the agglomeration of HfB2 powder during the liquid phase co-precipitation method combined with carbothermal reduction. Based on various characterizations, it is discovered that the presence of dispersants can greatly reduce the particle size and restrain the agglomeration of the HfB2. Specifically, the HfB2 prepared using polyethylene glycol (PEG) demonstrates an ultra-fine particle size down to hundreds of nanometers. To better understand the function of the dispersant, the formation of the HfB2 is unveiled via a combination of multiple characterizations. In detail, the dispersants can cap on the formed HfB2 and restrict their further growth and agglomeration during the reaction through the electrostatic repulsion and steric hindrance of high molecular polymer, thereby greatly improving the quality of HfB2 powder.

Self-assembled biomineralized MnOx for low temperature selective catalytic reduction of NOx

A self-assembled biomineralized MnOx materials was prepared by a simple liquid phase co-precipitation method for selective catalytic reduction (SCR) of nitrogen oxides (NOx). Biomineralized MnOx exhibited great SCR performance (achieve > 99% NOx conversion at 100 °C) and high N2 selectivity (exceed 70% at 75–200 °C). The effects of biomineralized materials on physiochemical properties of catalyst were investigated by various characterization methods. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that the crystal structure and the morphologies of MnOx and biomineralized MnOx are remained the same. In order to eliminate the effect of specific surface area, the rate of specific reaction for biomineralized MnOx was calculated to be about twice than that of MnOx. In-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) analyze intermediates during SCR, and speculated that biomineralized MnOx catalyst may mainly follow the Langmuir-Hinshelwood(L-H) mechanism below 200 ℃. The above excellent N2 selectivity can be attributed to the fast NOx specific reaction rate, form Mn-O-C and Mn-C-N structure, provide abundant oxygen vacancies, and high Mn3+/Mn atomic ratio on the catalyst surface. Moreover, biomineralized MnOx possessed a better catalytic cycle performance due to the synergistic effect between biomass and Mn species. Therefore, a reasonable preparation method is proposed to realize the industrial application of biomineralized manganese oxide.

Effect of Sc2O3 addition on the phase composition and electron emission performance of Co-precipitated aluminates for impregnated cathodes

Herein, a series of 6BaO·1CaO·2Al2O3 + x wt% Sc2O3 (x = 1, 3, 5, 7, 9) impregnants were synthesized by a liquid-phase co-precipitation method and subsequent sintering at 1200 °C. The as-synthesized emissive materials were impregnated into porous tungsten matrices at 1700 °C, and their phase composition and electron emission performance were investigated. The X-ray diffraction analysis of the sintered and melted impregnated products revealed that they comprised multi-phase structures consisting of (Ba,Ca)3Al2O6, Ba2ScAlO5, and BaAl2O4 phases. Furthermore, the addition of 3 wt% Sc2O3 to the impregnated test cathodes significantly increased the emission level of the test cathode to 11.4 ± 0.6 A cm−2 at 1100 °CB (i.e., brightness temperature). The relationship between the electron emission properties and phase concentration in the impregnants was analyzed, and the results revealed that the emission performance of the cathodes deteriorated with an increase in the Sc2O3 content, which could be attributed to an increase in the concentration of non-active BaAl2O4 phase in the impregnants.

Investigation of the supercapacitance of ruthenium-based/ hemp stem activated carbon

This work presents the synthesis of amorphous ruthenium-based/hemp stem activated carbon (HSAC) composites by a liquid phase co-precipitation method. It is the first time that a solution of tetramethylammonium bicarbonate is used as the precipitant. The result reveals that the as-synthesized ruthenium oxide particles are small in size and homogenously distributed on the activated carbon surface. Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) results show that the ruthenium oxide/HSAC composite has a high mass-specific capacitance (652.79 F g−1 at 5 mV s−1) and excellent rate capability. Electrochemical impedance spectroscopy (EIS) experiments further demonstrate that it has a low device series resistance (0.653 Ω), which has a great enhancement by contrast with the state-of-the-art previous reports. High specific capacitance, outstanding cycling stability, and facile preparation conditions make the electrode material potentially promising for energy storage and conversion devices.

Manganese dioxide nanosheets decorated on MXene (Ti3C2Tx) with enhanced performance for asymmetric supercapacitors

The incorporation of nanosized pseudocapacitive materials and structure design are general strategies to enhance the electrochemical performance of MXene-based materials. Herein, the decoration of manganese dioxide (MnO2) nanosheets on MXene (Ti3C2Tx) surfaces was prepared by a facile liquid phase coprecipitation method. Ti3C2Tx is initially modified by polydopamine (PDA) coating to ensure the homogeneous distribution of MnO2 nanosheets and tight and close connections between MnO2 and the Ti3C2Tx backbone. Due to the obtained three-dimensional (3D) nanostructure, facilitating electron transport within the electrode and promoting electrolyte ion accessibility, the δ-MnO2@Ti3C2Tx-0.06 electrode yields superior electrochemical performances, such as a rather large areal capacity of 1233.1 mF cm−2 and high specific capacitance of 337.6 F g−1 at 2 mV s−1, as well as high cyclic stability for 10000 cycles. Furthermore, δ-MnO2@Ti3C2Tx-0.06 composites are employed as positive electrodes, and activated carbon (AC) materials act as negative electrodes with an aqueous electrolyte of 1 M Na2SO4 to assemble asymmetric supercapacitors. The prototype device is reversible at cell voltages from 0 to 1.8 V, and manifests a maximum energy density of 31.4 Wh kg−1 and a maximum power density of 2700 W kg−1. These encouraging results show enormous possibilities for energy storage applications.

Carrier densities of Sn-doped In2O3 nanoparticles and their effect on X-ray photoelectron emission

Sn-doped In2O3 (ITO) nanoparticles with various Sn doping concentrations were successfully fabricated using a liquid phase coprecipitation method. Similar to sputtered ITO thin films, Sn doping reaches a maximum carrier density (1.52×1021cm−3) at 10 at. % in ITO nanoparticles, which was estimated from the bulk plasmon energy based on a scanning ellipsometry (SE) simulation. Interestingly, the X-ray photoelectron emission spectra (XPS) of In 3d core levels show a clear asymmetric peak with a shoulder on the high-binding-energy side for degenerated ITO nanoparticles, which may be associated with the influence of the surface plasmon or plasmonic coupling. Our results suggest that combining the SE simulation and XPS measurements effectively provides a new way to understand the difference between bulk plasmons and surface plasmons for transparent conductive oxide nanoparticles.

Room-temperature liquid-phase synthesis of Na3FeF6 and its lithium/sodium storage properties

A Na3FeF6 electrode material for lithium-ion batteries and sodium-ion batteries is firstly synthesized by a room-temperature liquid-phase co-precipitation method. A scanning electron microscopy observation shows that the material owns pseudocubic morphology in primary particles. The charge-discharge tests indicate that Na3FeF6 for lithium-ion batteries and sodium-ion batteries delivers initial discharge capacities of 472.8 mAh·g−1 and 121.1 mAh·g−1, respectively, with decent capacity retentions, which is hardly influenced by charging cut-off voltages. The cyclic voltammetry results of Na3FeF6 as the electrode material confirm a two-step reaction mechanism for lithium-ion batteries while a one-step reaction mechanism for sodium-ion batteries.

Effect of BaO on the phase composition and properties of aluminates for Ba-W cathodes

In this study, we prepared (4.8+x)BaO·CaO·2Al2O3 (0 ≤ x ≤ 1.6) aluminates by calcining the precursors under static air at 1500 °C for 120 min. The precursor powders were prepared using a liquid phase co-precipitation method. The effects of the molar content of BaO on the phase composition (before and after melting), melting properties, environmental stability, evaporation, and emission properties of the aluminates was investigated systematically The results showed that the phase of the aluminates completely transformed from Ba5CaAl4O12 to Ba3CaAl2O7 with an increase in the BaO content. After melting, the phase changed from Ba5CaAl4O12 to a mixed phase of Ba5CaAl4O12 and Ba3CaAl2O7. In the high-temperature molten state, the aluminates were in the ionic state, which generated a relatively low-energy Ba5CaAl4O12 phase during cooling crystallization. With every 0.4 mol increase in the BaO content, the initial melting temperature of the aluminates decreased by 10–20 °C, while the environmental stability deteriorated gradually. When the aluminates reacted with H2O and CO2 in the air, the original phase still existed and the characteristic peaks gradually broadened, but with the formation of Ca(OH)2, CaCO3, and BaCO3. At 1050 °C, with an increase in the BaO content, the evaporation rate of the Ba-W cathodes increased and the emission current density first increased and then decreased. The main components of the Ba-W cathode evaporation were Ba and BaO. At n(BaO):n(CaO):n(Al2O3) = 6:1:2, the Ba-W cathode showed the best emission performance, and its pulse emission current density at 1050 °C was as high as 35.31 A/cm2.

Fabrication of Nd:YAG transparent ceramics using powders synthesized by citrate sol-gel method

The highly transparent Nd:YAG ceramics were prepared by using powders synthesized by citrate sol-gel method. The citrate sol-gel method could avoid defects of the solid-phase reaction method and the liquid phase co-precipitation method in preparing Nd:YAG ceramic powders with the ratio of (Nd3+, Y3+):Al3+ equal to 3:5. The dried gel was the three dimensional net-shaped porous structure. When the dried gel was calcined at 500 °C in oxygen, pure YAG phase formed directly with no intermediate phases. The Nd:YAG powders calcined at 800 °C had maximum particle size near 500 nm. These powders were not equiaxed and there were dumbbell-like and annular grains. The highly compact Nd:YAG ceramics could be well sintered at 1750 °C for 12 h in vacuum atmosphere, and these sample had the average grain size about 3.8 μm. The polished Nd:YAG ceramics was highly transparent, and the transmittances at 1064 nm and 400 nm were 83.4% and 74.2%, respectively. The fluorescence emission spectrum implied high possibility of realizing laser output at 1064 nm by pumping at 808 nm. Generally, the citrate sol-gel method was also a reliable choice for preparing high quality Nd:YAG transparent ceramics.

Effect of CaO on Phase Composition and Properties of Aluminates for Barium Tungsten Cathode.

6BaO·xCaO·2Al2O3 (x = 0.8, 1.2, 1.6, 2, and 2.2) aluminates were synthesized via a liquid phase co-precipitation method. Effects of the molar amount of CaO on the phase of aluminates before and after melting and their hygroscopic phase, melting properties, environmental stability, evaporation, and emission properties were systematically studied. The results show that with the increase of the molar amount of CaO, the aluminates change from a mixture phase to a single phase of Ba3CaAl2O7, and the diffraction peak shifts to a higher angle. The melted phase of the aluminates changed from a single phase to a mixed phase of Ba5CaAl4O12 and Ba3CaAl2O7. Meanwhile, the comprehensive properties of the aluminates are improved. The weight gain of 6BaO·2CaO·2Al2O3 aluminates is only 10.88% after exposure to air for 48 h; the pulse emission current density of barium tungsten cathodes impregnated with 6BaO·2CaO·2Al2O3 aluminates in the porous tungsten matrix can reach 28.60 A/cm2 at 1050 °C, and the evaporation rate is 2.52 × 10−10 g/(cm2·s).

Factors affecting the phase composition of 612 aluminates for Ba–W cathode

The precursor powder of 612 aluminates were synthesized by using liquid-phase co-precipitation method. The microstructure and formation mechanisms of the precursor powder were investigated through X-ray diffraction, thermal gravimetric, differential scanning calorimetry, and scanning electron microscope. The effects of the stacking states of the precursor powder, calcination temperature, and atmosphere on the phase compositions of 612 aluminates were also systematically studied. Results showed that the prepared precursor powder was a mixture of BaCO3, BaCa(CO3)2, and amorphous AlOOH, which with particle size ranging from 20 to 30 nm. The stacking states of the precursor powder considerably influenced the phase composition of aluminates. The pressed precursor tablet can ensure the final phase composition of aluminates was Ba3CaAl2O7. When the precursor powder was calcined in CO2 atmosphere at 1400 °C for 2 h, the phase composition included Ba5CaAl4O12, BaAl2O4, and BaCO3. When the calcination temperature was increased, the main crystalline phase of aluminates changed from Ba5CaAl4O12 to Ba3CaAl2O7 in flowing N2, Ar, and static air. The barium–tungsten cathode prepared by aluminates of Ba3CaAl2O7 phase showed better emissivity than that of Ba5CaAl4O12 phase. The current density of pulse emission at 1050 °C can reach 35.31 A/cm2.

Degradation of dye wastewater by persulfate activated with Fe3O4/graphene nanocomposite

In this study, Fe3O4/graphene nanocomposite was synthesized through a liquid-phase co-precipitation method and characterized using X-ray diffraction and Fourier transform infrared spectrometer. The synthetic Fe3O4/graphene was used as a heterogeneous catalyst to activate persulfate to efficiently degrade methylene blue (MB). The target pollutant MB can be degraded by sulfate radicals depending on several parameters including persulfate and Fe3O4/graphene concentrations, pH and reaction temperature. Within 120 min of reaction time, almost 100% of 0.05 mM MB was removed by 1.5 mM persulfate in the presence of 150 mg/L of Fe3O4/graphene at pH = 6.0 and 25 °C. The degradation of MB was found to follow the pseudo-first-order kinetic model. The Fe3O4/graphene has much better stability and reusability than free Fe3O4 suggested by reuse tests. The results demonstrate that Fe3O4/graphene activated persulfate is a promising technology for remediation of water pollution caused by organic contaminants.

Synthesis of Nd:GGG Powder by Liquid Phase Co-Precipitation or Solid State Method and Preparation of its Transparent Ceramic

Neodymium-doped gadolinium gallium garnet (Nd:GGG) precursor and ceramic were prepared by liquid phase co-precipitation or solid-state methods, and the properties were studied. The results indicate that the precursor prepared with the liquid phase co-precipitation method has a small particle size. The sub-transparent ceramic was obtained after the body sintered for 2-3h at 1650°C at 1100Pa using liquid-phase co-precipitation method. When the body was sintered at 1750°C for 2-3h, a sintered body with non-transparency was obtained. The absorption spectrum and fluorescence spectrum of the sub-transparent ceramic were measured with the cross section at 807nm was calculated as1×10-20cm2 and the strongest emission peak located at 1061nm.

Direct Electron Transfer and Electrocatalysis of Hemoglobin on ITO Nanoparticle Electrodes

A novel biofuel cell cathode has been developed based on direct electron transfer (DET) by using hemoglobin (Hb) as an electrocatalyst for hydrogen peroxide (H2O2) reduction and indium tin oxide (ITO) nanoparticles as an electrode material. The nanoparticles were prepared on an ITO-coated glass plate by liquid phase co-precipitation method, and the electrochemical characteristics were examined in phosphate buffered saline (PBS) solution (pH 7.4) containing Hb. In half-cell measurements, a large reduction current of H2O2 due to the electrocatalytic activity of Hb flowed and reached 130 mA cm-2 at -0.45 V vs. Ag|AgCl|KCl(satd.). A single cell with the H2O2|Hb|ITO nanoparticle cathode showed an open circuit voltage of ca. 0.75 V and a maximum power density of ca. 23 mW cm-2.

Synthesis of ITO Nanoparticles Prepared by the Degradation of Sulfide Method

Indium tin oxide (ITO) nanoparticles are synthesized by the two-degradation sulfide and liquid-phase co-precipitation method under the given conditions with solutions of InCl3·4H2O and SnCl4·5H2O in the presence of ethylendyamine. The sample powders were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses after heat treatments. The SEM results show that the size of the ITO particles prepared by the co-precipitation method is decreased to 100 nm, whereas the size of the ITO prepared by degradation of sulfide increases to 1 μm after heat treatment. The XRD results reveal that the size of crystallite ITO particles is increased with increasing annealing temperature. Finally the intensity ratio of I400/I222 has an increase of 29.07% for ITO prepared by the co-precipitation method.

Synthesis of ITO Nanoparticles by Liquid Phase Co-Precipitation Method

The nano-scale indium tin oxide (ITO) particles are synthezed by liquid phase co-precipitation method under given conditions with solution of indium chloride, tin chloride and ammonia. The absolute ethyl alcohol or deionized water was used as solvent and the dodecylamine or hexadecylamine surfactant as a dispersant in the reaction system. The sample powder was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution electron microscopy (HRTEM). Based on the transmission electron micrograph， the influences of the two different solvents and the two different dispersants on the nanoparticle size and dispersion were studied respectively. The results shown that the ITO particles are finely crystallized body centered cubic structure. The particle size has distributed in 30nm to 90nm.

Synthesis and characterization of ZnO-doped cupric oxides and evaluation of their photocatalytic performance under visible light

ZnO–CuO binary oxide photocatalysts were synthesized by the liquid phase coprecipitation method. The catalysts were characterized by X-ray diffraction, transmission electron microscopy and UV–vis spectroscopy. The photocatalytic activity of the ZnO–CuO nanocomposites was estimated on the basis of decoloration of methyl orange dye under visible light. The effects of parameters such as calcining temperature, amount of catalyst and pH on the photocatalytic degradation efficiency of methyl orange solutions were investigated in detail. The maximum photocatalytic activity was obtained on ZnO–CuO nanocomposites with a calcining temperature of 350 °C, using a catalyst amount of 0.056 g/L and a pH of 7.5. The visible light-driven capability of ZnO–CuO nanocomposites is much better than that of commercially available TiO2 photocatalysts under comparable conditions.

Synthesis and CO2 Adsorption Characteristics of Lithium Zirconates with High Lithia Content

Pure monoclinic phase Li6Zr2O7 and rhombohedral phase Li8ZrO6 that coexisted with a fraction of Li6Zr2O7, are synthesized by a liquid phase coprecipitation method and characterized by X‐ray diffraction, scanning electron microscopy, and thermo‐gravimetric analysis. The high‐temperature CO2 uptake properties of both samples are systematically investigated. The temperature effect tests indicate that, in the case of low temperature (<973 K), both of the adsorbents exhibit slow CO2 uptake rates because of the inhibited diffusion of CO2 in the solid carbonate shell; while at the temperature above the melting point of Li2CO3 (about 983 K), the CO2 uptake rates are enhanced dramatically for both Li6Zr2O7 and Li8ZrO6, and achieved about 12.3% weight gain and 35.0% weight gain within 15 min at 1073 K, respectively. The thermal stability tests indicate that both samples exhibit gradually reduced capacities during the multicycle processes. The analysis of the crystalline structure reveals that the reduced capacities are resulted from the loss of lithia under high temperatures. Finally, the possible adsorption pathways for both monoclinic phase Li6Zr2O7 and rhombohedral phase Li8ZrO6 are suggested as well.

Preparation of ITO Nanoparticles by Liquid Phase Coprecipitation Method

The nanoscale indium tin oxide (ITO) particles are synthesied by liquid phase coprecipitation method under given conditions with solution of indium chloride, tin chloride, and ammonia. The absolute ethyl alcohol or deionized water was used as solvent and the dodecylamine or hexadecylamine surfactant was used as a dispersant in the reaction system. The sample powder was characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), and high‐resolution electron microscopy (HRTEM). Based on the transmission electron micrograph, the influences of the two different solvents and the two different dispersants on the nanoparticle size and dispersion were studied, respectively. The results showed that the ITO particles are finely crystallized body‐centered cubic structure. The particle size has distributed in 30 nm to 90 nm.