Mesoscale organization of CuO nanoslices: Formation of sphere

The nanocrystalline CuO powders were prepared by precipitation method using Cu(NO₃)₂ as copper raw material, water and ethanol as dispersants, and NaOH and ammonia solution as precipitates. The structure, particle size and morphology of resulting CuO powders were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mechanism of CuO formation was discussed.     

Synthesis,structure, and physicochemical properties of bivalent element hexanitratothorates

Compounds of the composition M^IITh(NO₃)₆·8H₂O (M^II = Mg, Mn, Co, Ni, Zn) were prepared by precipitation from solution. The structure and thermal decomposition of these compounds were examined by X-ray diffraction and thermal analysis. The previously unknown standard enthalpies of formation of the compounds at 298.15 K were determined by reaction calorimetry.     

The CeO2–TiO2–ZrO2 sol–gel film: a counter-electrode for electrochromic devices

Thin films of CeO₂–TiO₂–ZrO₂ with 23 mol% of Ce, 45 mol% of Ti and 32 mol% of Zr were obtained by the sol–gel method. The precursor sol was prepared from a mixture of Ce(NH₄)₂ (NO₃)₆, Ti(OPrⁱ)₄ and Zr(OPrⁱ)₄ solubilized in isopropanol and then sonicated. Xerogels were characterized by Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) and X-ray diffraction. The films were deposited by dip-coating technique on a glass plate coated with an indium tin oxide film (ITO) and thermally treated at 80 °C for 15 min. and heated at 450 °C for 15 min in an oxygen atmosphere. By means of the addition of a lithium salt (LiCF₃SO₃) to the precursor solution, films with different electrochemical performances were obtained. Their possible use as ion storage (counter-electrode) in electrochromic devices (ECD) was analyzed by spectroelectrochemical measurements using cyclic voltammetry and chronoamperometry coupled to spectrometric measurements.     

Preparation of nano-sized flower-like ZnO bunches by a direct precipitation method

In this work, nano-sized ZnO particles were prepared by a direct precipitation method with Zn(NO₃)₂·6H₂O and NH₃·H₂O as raw materials, and the impact of the synthesis process was studied. The optimal thermal calcined temperature of precursor precipitates of ZnO was obtained from the differential thermal analysis (DTA) and the thermal gravimetric analysis (TGA) curves. The purity, microstructure, morphology of the calcined ZnO powders were studied by X-ray diffraction (XRD), energy dispersive X-ray spectrum (EDS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The synthesized ZnO powders had a wurtzite structure with high purity. The final products were of flower-like shape and the nanorods which consisted of the flower-like ZnO bunches were 20–100 nm in diameter and 0.5–1 μm in length. The effect of process conditions on the morphology of ZnO was discussed.     

Formation and transformation of ZnTiO3 prepared by sol–gel process

ZnTiO₃ powders with pure hexagonal phase were prepared by the sol–gel process with Zn(NO₃)₂·6H₂O and Ti(OC₄H₉)₄ materials. The thermal behavior and phase transformation of the gels were investigated by the differential scanning calorimetry–thermogravimetry (DSC–TG) analysis, X-ray diffraction (XRD) patterns, Fourier-transforming infrared (FT-IR) spectroscopy, and Raman scattering spectroscopy. The results revealed that pure hexagonal phase of ZnTiO₃ could be obtained at low temperature of 800 °C. However, in further increased temperature above 900 °C, hexagonal ZnTiO₃ would decompose into cubic Zn₂TiO₄ and rutile TiO₂.     

Rational Construction of Heterostructured Cu3P@TiO2 Nanoarray for High-Efficiency Electrochemical Nitrite Reduction to Ammonia

Electroreduction of nitrite (NO₂⁻) to valuable ammonia (NH₃) offers a sustainable and green approach for NH₃ synthesis. Here, a Cu₃P@TiO₂ heterostructure is rationally constructed as an active catalyst for selective NO₂⁻-to-NH₃ electroreduction, with rich nanosized Cu₃P anchored on a TiO₂ nanoribbon array on Ti plate (Cu₃P@TiO₂/TP). When performed in the 0.1 m NaOH with 0.1 m NaNO₂, the Cu₃P@TiO₂/TP electrode obtains a large NH₃ yield of 1583.4 µmol h⁻¹ cm⁻² and a high Faradaic efficiency of 97.1%. More importantly, Cu₃P@TiO₂/TP also delivers remarkable long-term stability for 50 h electrolysis. Theoretical calculations indicate that intermediate adsorption/conversion processes on Cu₃P@TiO₂ interfaces are synergistically optimized, substantially facilitating the conversion of NO₂⁻-to-NH₃.     

Multiferroic YMn2O5 fine powders derived from hydrothermal process

Multiferroic YMn₂O₅ fine powders were synthesized by a hydrothermal process from Y(NO₃)₃ · 6H₂O and Mn(NO₃)₂, and their structure and magnetic characteristics were evaluated. YMn₂O₅ fine powders with orthorhombic structure were synthesized by the present process with aqueous NaOH as the mineralizer, and the synthesis conditions such as temperature and [NaOH] have significant effects upon the grain size and morphology. The single phase YMn₂O₅ fine powders with the most uniform morphology were synthesized at 523 K from the solution with [NaOH] = 1 M, and then the good sinterability was expected at lower temperatures where the phase separation in YMn₂O₅ ceramics could be avoided. YMn₂O₅ fine powders derived by the present hydrothermal process indicated the weak ferromagnetism below 45 K.     

Constructing Co@TiO2 Nanoarray Heterostructure with Schottky Contact for Selective Electrocatalytic Nitrate Reduction to Ammonia

Electrochemical nitrate (NO₃⁻) reduction reaction (NO₃⁻RR) is a potential sustainable route for large-scale ambient ammonia (NH₃) synthesis and regulating the nitrogen cycle. However, as this reaction involves multi-electron transfer steps, it urgently needs efficient electrocatalysts on promoting NH₃ selectivity. Herein, a rational design of Co nanoparticles anchored on TiO₂ nanobelt array on titanium plate (Co@TiO₂/TP) is presented as a high-efficiency electrocatalyst for NO₃⁻RR. Density theory calculations demonstrate that the constructed Schottky heterostructures coupling metallic Co with semiconductor TiO₂ develop a built-in electric field, which can accelerate the rate determining step and facilitate NO₃⁻ adsorption, ensuring the selective conversion to NH₃. Expectantly, the Co@TiO₂/TP electrocatalyst attains an excellent Faradaic efficiency of 96.7% and a high NH₃ yield of 800.0 µmol h⁻¹ cm⁻² under neutral solution. More importantly, Co@TiO₂/TP heterostructure catalyst also presents a remarkable stability in 50-h electrolysis test.     

Preparation and electromagnetic property of Al-doped SnO2 powders by coprecipitation method in the GHz range

Al-doped SnO₂ powders have been prepared by coprecipitation method at 550 °C, using tin chloride (SnCl₄·5H₂O) as the raw material, ammonium hydroxide (NH₃·H₂O) as the precipitator, and aluminum nitrate (Al(NO₃)₃·9H₂O) as the doping source, respectively. The microstructure of the prepared powders has been characterized by X-ray diffraction and scanning electron microscope, respectively. Results show that the prepared powders were Sn_(1?x)Al_xO₂ (x = 0, 0.03, 0.06, and 0.09) solid solution powders and the lattice constant decreased with increasing Al doping content. The electromagnetic property in the frequency range of 8.2–12.4 GHz of prepared powders has been determined. The real part (ε′) and imaginary part (ε″) of permittivity of prepared powders increased with increasing Al doping content. There was little change of real part (μ′) and imaginary part (μ″) of permeability of prepared powders. The electromagnetic loss mechanism has been discussed.     

Thermoanalytical characteristics of powders in dental cast investment

The present study examined the thermal properties of phosphate-bonded investments, a gypsum-bonded investment and an experimental investment powder when the basic powders were heated to high temperatures by simultaneous differential thermal analysis (DTA) and thermogravimetry (TG). The phosphate-bonded investments showed values of about 59 kcal mol^–1 (247 kJ mol^–1) (thermal decomposition of NH₄H₂PO₄) and about 11 kcal mol^–1 (46 kJ mol^–1) (formation of NH₄MgPO₄). Thermal reactions occurred clearly on the DTA-TG curves for the investment powders, using powders of NH₄H₂PO₄, and MgO with NH₄H₂PO₄/MgO = 1 as main components in the investment.     

Study on thermodynamics and oxidation mechanism of ethylene glycol in the preparation of nanometer nickel powders

Nanometer nickel powders have been prepared using the polyol method with NaOH, Ni(NO₃)₂·6H₂O, ethylene glycol (EG), and polyvinylpyrrolidone (PVP) as raw materials. The thermodynamics of the reaction system was studied, and the E–pH diagram of Ni–EG–H₂O was plotted. The oxidation products of EG were predicted from the E–pH diagram, and CO₃²⁻ in alkaline solutions was identified as the product through the IR spectrum and CaCO₃ sediment. Field-emission scanning electron micrograph (FE-SEM) showed that spherical nanometer nickel powders were obtained.     

Self-Supported Pd Nanorod Arrays for High-Efficient Nitrate Electroreduction to Ammonia

Electrochemical nitrate (NO₃⁻) reduction to ammonia (NH₃) offers a promising pathway to recover NO₃⁻ pollutants from industrial wastewater that can balance the nitrogen cycle and sustainable green NH₃ production. However, the efficiency of electrocatalytic NO₃⁻ reduction to NH₃ synthesis remains low for most of electrocatalysts due to complex reaction processes and severe hydrogen precipitation reaction. Herein, high performance of nitrate reduction reaction (NO₃⁻RR) is demonstrated on self-supported Pd nanorod arrays in porous nickel framework foam (Pd/NF). It provides a lot of active sites for H* adsorption and NO₃⁻ activation leading to a remarkable NH₃ yield rate of 1.52 mmol cm⁻² h⁻¹ and a Faradaic efficiency of 78% at −1.4 V versus RHE. Notably, it maintains a high NH₃ yield rate over 50 cycles in 25 h showing good stability. Remarkably, large-area Pd/NF electrode (25 cm²) shows a NH₃ yield of 174.25 mg h⁻¹, be promising candidate for large-area device for industrial application. In situ FTIR spectroscopy and density functional theory calculations analysis confirm that the enrichment effect of Pd nanorods encourages the adsorption of H species for ammonia synthesis following a hydrogenation mechanism. This work brings a useful strategy for designing NO₃⁻RR catalysts of nanorod arrays with customizable compositions.     

Nanohydroxyapatite prepared from non-toxic organic Ca2+ compounds by precipitation in aqueous solution

Nanocrystalline hydroxyapatites were prepared by the precipitation method using a water soluble Ca²⁺ organic compounds and (NH₄)₂HPO₄. The fine nanohydroxyapatites had spherical, needle-like or mixed morphology and specific areas around 150 m²/g. The nanocrystalline powders differed by thermal stability and they were transformed to bi- or three-phasic systems with hydroxyapatite, βTCP and αTCP phases after annealing at 1000 °C.     

Photoluminescence of Tb/Ce co-doped aluminum oxynitride powders

Aluminum oxynitride(AlON) phosphors co-doped by Tb³⁺ and Ce³⁺ were synthesized by nitridation of the precursor which was co-precipitated from Al(NO₃)₃ solution and nanosized carbon black at 1750 °C for 2 "hrs" in flowing nitrogen atmosphere. The obtained AlON based powders were composed of polycrystalline spinel typed particles with sizes in the range of 1-3 μm. Under an excitation of 275 nm, it was found that co-doping of Ce³⁺ could drastically enhance the luminescence of AlON:Tb³⁺ powder by energy transfer. The product with 0.5 mol% Ce³⁺ and 0.67 mol% Tb³⁺ exhibited a strong broad green emission at 540 nm. The critical quenching concentration of Tb³⁺ in AlON:0.5 mol% Ce³⁺/xmol% Tb³⁺ phosphor was determined to be 0.67 mol%. It was supposed that the mechanism of concentration quenching of Tb³⁺ in AlON:0.5 mol% Ce³⁺ xmol% Tb³⁺ phosphor was dipole-dipole interaction.     

Effects of pH and H2O2 upon coprecipitated PbTiO3 powders

The properties of precipitated materials are highly dependent upon the complex ionic equilibria of the species in the solutions used for precipitation. Concentration, temperature, and pH dictate the complex species present within aqueous systems, and therefore affect the final precipitate properties. This paper discusses the effect of pH on the properties of PbTiO₃ precursor powders prepared by adding stoichiometric mixtures of TiCI₄ and Pb(NO₃)₂, in aqueous solution, to NH₄OH solutions. Several powders were prepared between pH 8.00 and 10.50. The pH does not affect the amorphous structure, but does have a pronounced effect upon the specific surface area and growth mechanisms of the precipitates.Since previous studies indicated that hydrogen peroxide (H₂O₂) affects the hydroxylation of the precipitated powders, the effect of (H₂O₂) concentration on the precipitate properties was also studied. Several precipitates were prepared from solutions containing (H₂O₂): PbTiO₃ ratios between 0:1 and 6:1. When (H₂O₂) was not added to the solutions used for precipitation, atmospheric CO₂ dissolved in solution caused precipitation of carbonate species. Thus, addition of the (H₂O₂) to the solutions inhibited precipitation of the carbonates.     

Direct synthesis of Zn-ZSM-5 with novel morphology

Zinc-containing ZSM-5 zeolite with novel morphology was firstly synthesized in a one-step route using [Zn(NH₃)₄]²⁺ aqueous solution as zinc resource and n-butylamine as template. The materials were characterized by XRD, SEM, diffuse reflectance UV–vis spectra, FTIR for pyridine adsorption. The results showed that the formation of this novel structure might be related to the introduction of [Zn(NH₃)₄]²⁺ aqueous solution and the zinc existent state in zeolite.     

Univalent metal hexanitratothorates

Compounds M ₂ ^I Th(NO₃)₆ (M^K = NH₄, K, Rb, Cs) were precipitated from a solution. The structure and thermolysis of these compounds were studied by X-ray diffraction, precision IR spectroscopy, and thermal analysis. Their previously unknown standard enthalpies of formation at 298.15 K were determined by reaction calorimetry.     

Fabrication and characterization of novel bowknot-like CeO2 crystallites and applications for Methyl-orange Sensors

Bowknot-like CeO₂ bundles crystals were successfully prepared from a single precursor via a thermal decomposition route. The precursor was synthesized by a hydrothermal reaction using Ce(NO₃)₃ · 6H₂O with CO(NH₂)₂ at 150 °C in a water-glycerol complex solution. Glycerol plays a very important role for the formation of precursor bowknot-like structures. The morphology of the precursor was maintained during the heating process. The optical absorption spectrum indicates that the CeO₂ dendrites have a direct band gap of 3.42 eV, which is mostly larger than values of bulk powders due to the quantum size effect. The electrochemical characters of the CeO₂ bundles structures are studied by their investigation of cyclic voltammetry (CV). It was found that the CeO₂ bundles can greatly improve the electron transfer ability.     

Physicochemical properties of silver powders obtained by contact precipitation with magnesium

We study the influence of the concentrations of AgNO₃ (0.06–0.32 mole/liter) and NH₄NO₃ (0.1–0.5 mole/liter) in the initial solution and the hydrodynamic conditions for Rev varying within the range 12,950–46,700 on the physicochemical properties of silver powders obtained from secondary solutions of silver (I) nitrate by contact precipitation with magnesium chips within the range 293–323°K. At a temperature of 313°K, for the stoichiometric amount of magnesium chips, turbulization of the medium corresponding to Re _v = 24,200, and the contents of AgNO₃ and NH₄NO₃ in the initial solution equal to 0.06–0.1 mole/liter and 0.25 mole/liter, respectively, we obtain silver powders with a bulk density of 1.09 g/cm³, a specific surface area of 2520 cm²/g (determined according to the gas permeability), and mean particle sizes of 1.0–3.0 μm. Powder particles have perfect geometric shapes with tetragonal and hexagonal symmetry about the axis of growth. The content of Ag in the powder is equal to 99.9 wt.%. It is shown that, by choosing and combining the conditions of contact precipitation, we can get powders with prescribed physicochemical properties.     

Sol–gel processing and phase characterization of Al2O3 and Al2O3/SiC nanocomposite powders

Monolithic Al₂O₃ and Al₂O₃/SiC nanocomposite powders were prepared by sol–gel processing. The process involved the precipitation of Al(NO₃)₃·9H₂O with NH₄OH in excess water to form boehmite (AlOOH). XRD indicates that the subsequent thermal reaction proceeds by the phase transformation sequence AlOOH, γ-, δ-, θ-, to α-Al₂O₃. The ²⁷Al NMR spectra indicate a gradual increase in the proportion of Al in the tetrahedral sites of the γ-, δ- and θ-Al₂O₃ formed at increasing calcination temperatures. Complete transformation to octahedral Al (α-Al₂O₃) is marked by the abrupt disappearance of tetrahedral Al. Al₂O₃/SiC nanocomposite powders were prepared by adding α-SiC powder to the boehmite precursor at the precipitation stage. Upon heating, the ²⁹Si NMR spectra of the Al₂O₃/SiC powders reveal α-SiC, Al₂O₃·xSiO₂ and SiO₂ phases. Stable α-Al₂O₃ and α-Al₂O₃/SiC nanocomposite powders are formed at 1200 and 1300 °C, respectively. It appears likely that the presence of SiC modifies the thermal behaviour of the Al₂O₃ in the nanocomposites by stabilising the Al₂O₃ phases with concomitant oxidation of SiO₂.