Ammonia Co-precipitation Research Articles

Enhancement in the photocatalytic and photoelectrochemical properties of visible-light driven BiVO4 photocatalyst

In this paper, the synthesis, characterization, as well as the photocatalytic activity and photoelectrochemical properties of visible-light responsive Aurivillius structured BiVO4 photocatalyst, which were published in our laboratory, was reviewed. By fabrication of nanocomposites with carbon nanotube, synthesis of nano-size BiVO4 particles using an ammonia co-precipitation process, immobilization on fiber materials to form a BiVO4@fibers composite materials, the performances of photocatalytic decomposition of organic pollutes and photo-to-current conversion were enhanced due to surface properties improvement and the quick transportation of photogenerate electrons.

Synthesis of a new Ca[formula omitted]Y[formula omitted]V[formula omitted]Sn[formula omitted]O[formula omitted] yellow pigment

In this communication a new ceramic pigment based on codoping pyrochlore Y 2Sn2O7 with V 5+ and Ca2+ has been obtained. The limit of solid solution of CaxY 2−xV xSn2−xO7 is around x=0.16. Pigment becomes stable in double firing glazes (CIEL∗a∗b∗=78/5/35 5% w. enamelled) but unstable in single firing glazes such as based on CaO–ZnO–SiO2 chemical system. Using unconventional methods of synthesis the reactivity of the system and final pigmenting power of the powder is enhanced in the case of ammonia coprecipitation of a mixture of nitrates and tin chloride.

In situ synthesis of orange rutile ceramic pigments by non-conventional methods

Different precursor-mixtures of orange Cr,Sb-TiO2 ceramic pigment have been obtained by non-conventional methods (heterogeneous ammonia coprecipitation, urea homogeneous coprecipitation, PECHINI polyester method and an original aqueous–organic coprecipitation method in water–diethylenglycol medium) in order to produce in situ the pigment through the ceramic body firing. The pigmenting performances of powders were appraised in two cases: (a) as ceramic pigment for glazed porcelain stoneware and (b) as ceramic inks for screen printing of porcelain stoneware. Samples were characterised by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV–vis-NIR spectroscopy by diffuse reflectance method, CIE-L*a*b* colour parameters, BET specific surface area and crystallite size measured by the Scherrer method. The colouring performance of raw powders obtained by non-conventional methods in glazed porcelain stoneware improves that of the ceramic samples fired at 1100°C used as reference. TEM observations indicate nanostructured powders with pigmenting performance depending on factors such as their specific surface area (BET), the crystalline phases detected by XRD (e.g. anatase–rutile presence) and their crystallite size (Scherrer measurements). Ammonia coprecipitated samples, both in water and in water–diethylenglycol medium without surfactant addition, or modified by the addition of sodium dodecyl sulphate as surfactant, stand out by their colouring performance.

Low-temperature sintering behaviors of nanosized Ce 0.8Gd 0.2O 1.9 powder synthesized by co-precipitation combined with supercritical drying

Nanocrystalline Ce 0.8Gd 0.2O 1.9 (GDC20) powder was synthesized by ammonia co-precipitation combined with supercritical ethanol drying route, followed by characterizations with TG/DSC, XRD, BET, HR-TEM, and FESEM techniques. After calcination at 600 °C, the powder has a high specific surface area of 146.5 m 2 g −1 and an average crystal size of ∼5 nm without hard-agglomeration. The nano-GDC powder showed excellent sinterability, where by pressureless sintering at 900 °C for 4 h, the relative density of more than 98% and average grain size of 84 nm have been attained, which is attributed to the powder's ultrafine nanocrystal size, weak agglomeration and high homogeneity. Investigations indicate that in the initial sintering stage, grain growth behavior is mainly controlled by volume diffusion mechanism with an activation energy of ∼5.4 eV.

Synthesis of doped ceria–zirconia core–shell nanocomposites via sol–gel process

Abstract In order to introduce more conductive interfaces, the doped ceria–zirconia core–shell nanocomposites are synthesized via a simple and low-cost sol–gel process. Nitrates, citric acid and polyethylene glycol (PEG) are used as starting materials, and the compositions of the core and the shell are Ce 0.9 Gd 0.1 O 1.95 (GDC) and 8 mol% Sc 2 O 3 doped ZrO 2 (ScDZ), respectively. The room-temperature ammonia co-precipitation method is used to prepare the core materials. X-ray diffraction (XRD) indicates that the average grain sizes of the core and shell materials are about 6 nm and 8 nm. The core–shell nanostructure with about 60 nm diameter GDC core (approximate) and about 20 nm thick ScDZ shell, is supported by the field-emission scanning electron microscopy (FESEM) and the transmission electron microscopy (TEM) results. The effects of PEG and the mechanisms during the process of forming the core–shell nanocomposites are discussed in detail.

Synthesis and photocatalytic performances of BiVO 4 by ammonia co-precipitation process

BiVO 4 was prepared by a co-precipitation process using aqueous ammonia solution, followed by heating treatment at various temperatures. The crystalline structure and crystallization process, and their influences on photocatalytic O 2 evolution and organic pollutants degradation were investigated. It demonstrated that the crystalline structure is still the vital factor for the activities of both reactions. However, the crystallinity of BiVO 4 gives a major influence on the activity of O 2 evolution, whereas the surface area, plays an important role for photocatalytic MB decomposition. [Display omitted]

Synthesis of FeNi3/(Ni0.5Zn0.5)Fe2O4 nanocomposite and its high frequency complex permeability

FeNi3/(Ni0.5Zn0.5)Fe2O4 nanocomposite particles were successfully synthesized using the hydrazine reductioncombined with ammonia co-precipitation ferrite coating method. The x-ray andtransmission electron microscopy analysis showed that face-centred cubic-structuredFeNi3 nanoparticles were coated with spinel Ni–Zn ferrite. The compositeparticles were nearly spherical with diameters of about 80–200 nm andexhibited typical soft magnetic properties. The saturation magnetization(Ms) of the composite was greatly improved, compared with that of traditionalferrite. With increasing ferrite content, the eddy-current loss was effectivelysuppressed and a notable high frequency characteristic, in which the real partμ′ of the permeability was almost independent of the frequency, was observed. The imaginary partμ′′ remained at an extremely low value below the frequency of 300 MHz. The cut-off frequencyfr was estimated to be above 1 GHz. The highest value ofμ′ reached 13 whenthe ratio of FeNi3 to Ni0.5Zn0.5Fe2O4 was 1:1. Two peaks were observed in the permeability spectra,which may be ascribed to the ferromagnetic resonances ofFeNi3 and Ni–Zn ferrite respectively.

Coprecipitation and Hydrothermal Synthesis of Ultrafine 5.5 mol% CeO2‐2 mol% YO1.5ZrO2 Powders

Ultrafine 5.5 mol% CeO2—2 mol% YO1.5ZrO2 powders with controllable crystallite size were synthesized by two kinds of coprecipitation methods and subsequent crystallization treatment. The amorphous gel produced by ammonia coprecipitation and hydrothermal treatment at 200°C for 3.5 h results in an ultrafine powder with a surface area of 206 m2/g and a crystallite size of 4.8 nm. The powder produced by urea hydrolysis and calcination exhibits a purely tetragonal phase. In addition, the powders crystallized by hydrothermal treatment exhibit high packing density and can be sintered at lower temperature (,1400°C) with nearly 100% tetragonal phase achieved.