Chemical Co-precipitation Process Research Articles

Pressureless reactive sintering mechanism of nanocrystalline Bi 2O 3-Y 2O 3 solid electrolyte

Abstract The nanocrystalline Bi 2O 3-Y 2O 3 solid electrolyte material was synthesized by pressureless reactive sintering process with Bi 2O 3 and Y 2O 3 nano mixed powder as raw materials, which was prepared by a chemical coprecipitation process. The study on the behavior of nano δ-Bi 2O 3 formation and its grain growth showed that the solid solution reaction of Y 2O 3 and β-Bi 2O 3 to form δ-Bi 2O 3 occurs mainly in the initial stage of sintering process, and nano δ-Bi 2O 3 crystal grains grow approximately following the rule of paracurve (( D− D 0) 2= K·t) during sintering process. After sintered at 600°C for 2 h, the samples could reach above 96% in relative density and have dense microstructure with few remaining pores, the δ-Bi 2O 3 grains are less than 100 nm in size.

Hybrid precursors synthesis and optical properties of LnNbO 4:Bi 3+ blue phosphors and Bi 3+ sensitizing of on Dy 3+'s luminescence in YNbO 4 matrix

In this paper, Bi 3+ doped with LnNbO 4:Bi 3+ (Ln = La, Gd and Y) and YNbO 4:Bi 3+, Dy 3+ phosphors have been synthesized by a modified chemical co-precipitation process with hybrid precursors. Their micromorphology and particle sizes were characterized by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The photoluminescence data for LnNbO 4:Bi 3+ indicated that the emission peak positions for Bi 3+ showed red-shifts comparing to that of NbO 4 3− for undoped LnNbO 4 hosts. Besides this, it was found that Bi ion can enhance the emission intensity of Dy 3+ in YNbO 4 host lattice when the Bi ion concentration is lower than 3 mol%. Moreover, the influence of Bi 3+ concentration on the luminescent properties of YNbO 4 was examined, which shows that the optimum concentration was 1 mol% and concentration quenching occurred.

LuVO4:RE3+ (RE=Sm, Eu, Dy, Er) phosphors by in-situ chemical precipitation construction of hybrid precursors

In the context, a novel synthesis technology was applied to LuVO4:RE3+ (RE = Sm, Eu, Dy, Er) phosphors for the firstly time. Rare earth coordination polymers with aromatic carboxylic acids were used as the precursors of rare earth oxide components, subsequently polyethylene glycol (PEG) and ammonium vanadate (NH4VO3) were composed to assemble inorganic/organic hybrid polymeric dispersing media by an in-situ chemical coprecipitation process. After heat treatment of the resulting multicomponent hybrid precursors at 1100 °C, LuVO4:RE3+ phosphors were firstly synthesized. Both XRD and SEM indicated the particles presented good crystalline state, whose crystalline grain sizes were in the range of around 0.5–2 μm. The excitation spectra show a broad spectral band in narrow ultraviolet region of 200–350 nm, while no apparent or very weak absorption appears in long-wavelengths region of 350–500 nm. The corresponding emission spectra indicate that these crystalline phosphors exhibit photoluminescence of the characteristic transitions of RE3+. This technology can be expected to apply to prepare high efficient micron rare earth oxylates for practical development in luminescent materials and devices.

Influence of pH values on preparation of hydroxyapatite/gelatin composites

Hydroxyapatite (HA, Ca10(PO4)6(OH)2) biomaterials have been studied as the substitute materials for the hard tissue because of its biocompatibility, bioactivity, and osteoconductivity [1]. Unfortunately, HA biomaterials cannot be used for heavy load-bearing applications due to their low mechanical properties [2]. Therefore the mechanical properties of HA biomaterials have been frequently improved by including a series of organics, such as collagen, gelatin, and Polylactide (PLA) [3– –6]. It is well known that the hard tissue is composed of HA crystals and the organic matrix, of which the main constituent is type I collagen [7]. But the biggest practical problem with collagen is its cost and commercial availability. Gelatin is the metaprot of collagen and is commercially available. Same as collagen it also shows good biocompatibility and osteoconductvity [8, 9]. Therefore, gelatin has always been used instead of collagen to prepare composites with HA in many investigations. Chang et al. had developed a chemical co-precipitation process to synthesize HA/gelatin nanocomposites [10]. However, a detailed study of the effect of pH of reactive solution on the synthesis of HA/gelatin composites had not yet been studied till date. The pH values would affect both the HA formation and the gelatin incorporation. The aim of the present study was to investigate the effect of pH values on the structure, phase constitutes, and gelatin content of HA/gelatin composites. The staring materials were Ca(NO3)2 (analytic grade), (NH4)2HPO4 (analytic grade) and gelatin (MW250,000), and they were all dissolved in distilled water. NH3·H2O (analytic grade,) was added to above solutions to adjust the pH. Then the gelatin and (NH4)2HPO4 solutions were gradually added to the stirred Ca(NO3)2 solution, respectively. White precipitates of HA/gelatin was formed when PO3− 4 solution was dropped into the Ca 2+ solution according to the following equation.

Nanomagnetic Particles for SQUID-Based Magnetically Labeled Immunoassay

With the increasing importance of SQUID-based magnetically labeled immunoassay, the study on the synthesis of controllable sizes of magnetic nanoparticles plays a role to promote the accuracy of the immunoassay. In this work, Fe/sub 3/O/sub 4/ nano-particles coated with a suitable bio-probe (biotin) are synthesized through chemical co-precipitation process to probe the bio-target (avidin). Through the synthesis developed here, the particle hydrodynamic diameter can be adjusted from 30 to 90 nm, which provide candidates for probing various bio-targets in the future. The amount of the magnetically labeled avidin is then analyzed via measuring the saturated magnetization or the remanence of the sample by using a SQUID magnetometer.

The synthesis and luminescence of YPxV1−xO4:Dy3+ microcrystalline phosphors by in situ co-precipitation composition of hybrid precursors

Dy3+ activated YPxV1−xO4 phosphors were synthesized via an in situ chemical co-precipitation process with fixed Dy3+ concentration (2mol%) and varying x (x=0.2, 0.3, 0.4, 0.6, 0.7, 0.8, respectively). In order to obtain the hybrid precursors, the rare earth coordination polymers with salicylic acid were used as precursors and the polyethylene glycol (PEG) was used as dispersing media. Their microstructure and micromorphology have been analyzed by X-ray powder diffraction (XRD) and scanning electronic microscope (SEM), which indicates that there exist some novel cobblestone-like microcrystalline particles. The characteristic transitions of Dy3+ due to 4F9/2→6H15/2 (blue) and 4F9/2→6H13/2 (yellow) were detected in the emission spectra and the yellow-to-blue intensity ratio decreased with the increase of x value.

In situ chemical coprecipitation composition of hybrid precursors to synthesize YP xV 1− xO 4:Eu 3+ micron crystalline phosphors

In the context, a novel synthesis technology was applied to YP x V 1− x O 4:Eu 3+ phosphors. Among rare earth coordination polymers with aromatic carboxylic acids were used as the precursors of rare earth oxide components, and polyethylene glycol (PEG) and different molar ratio of ammonium vanadate (NH 4VO 3) and ammonium primary phosphate (NH 4H 2PO 4) were composed to assemble inorganic/organic hybrid polymeric dispersing media by an in situ chemical coprecipitation process. After the heat-treatment of the resulting multicomponent hybrid precursors at 1100 °C, YP x V 1− x O 4:Eu 3+ phosphors were achieved. Both XRD and SEM indicated the particles present good crystalline state, whose crystalline grain sizes were in the range of around 0.5–1 μm. The excitation spectra show a brand spectral band in narrow ultraviolet region of 200–280 nm, while no apparent absorption appears in long-wavelengths region of 280–400 nm. The corresponding emission spectra indicate that these crystalline phosphors exhibit very strong red emission of the characteristic transitions of Eu 3+ ( 5D 0 → 7F 2). This technology can be expected to apply to prepare high efficient micron rare earth oxylates (vanadates, phosphates or their complex phosphors) for practical development in luminescent materials and devices.

Synthesis and properties of Ni–SDC cermets for IT–SOFC anode by co-precipitation

Ni–Samaria-doped ceria (SDC) cermets have been prepared using a chemical co-precipitation process with Ni(NO 3) 2, Sm(NO 3) 3 and Ce(NO 3) 3 as precursors and (NH 4) 2CO 3 as mineralizer. The co-precipitates were fired at 600, 700 and 800 °C for 2 h, respectively, resulting in powders, which consist of two phases, the cubic NiO and fluorite structure ceria as confirmed with X-ray diffraction identification. The powder was observed with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The powders were fine with surface area of 23–51 m 2/g, and an average agglomerate particle size of 0.23–0.36 μm. The powder was sintered to porous NiO–SDC cermets, which were subsequently reduced to Ni–SDC cermets with porosity of about 30–40%. The Ni–SDC cermets exhibit metallic behavior over the temperature from 500 to 800 °C, as measured with a DC four-probe technique in H 2. The Ni–SDC cermets with high electrical conductivity appear to be compatible with the electrolyte (SDC) for intermediate temperature solid oxide fuel cell (IT-SOFC) application.

Effect of powder preparation on (CeO 2) 0.8(Sm 2O 3) 0.1 thin film properties by screen-printing

Chemical co-precipitation process and glycine-nitrate process (GNP) were used to synthesize (CeO 2) 0.8(Sm 2O 3) 0.1(SDC) powders for the preparation of thin dense film by screen-printing. XRD, transmission electron microscope (TEM), scanning electron microscope (SEM) and the AC impedance spectroscopy were used to investigate the phase identification, morphology and electrical properties of SDC powders, respectively. It was found that the powders prepared by both processes possessed similar sinterability and conductivity. To both synthesized powders, the SDC pellets sintered at 1350 °C can reach 96% in relative density and 0.08 S cm −1 in conductivity at 800 °C in air. Thin electrolyte films about 30 μm have been successfully achieved by screen-printing with both powders. While the thin electrolyte film by GNP powders possessed better sinterability and higher conductivity, which was attributed to its high pack density during the green film preparation.

Synthesis and aging effect of spherical magnetite (Fe3O4) nanoparticles for biosensor applications

The chemical coprecipitation process was used to synthesize about 7 nm, spherical magnetite nanoparticles to study magnetic properties and the aging effect. As-produced spherical magnetite nanoparticles have been aged in the atmosphere for 19 months. Magnetic properties and aging effect were studied by Mössbauer spectroscopy at a temperature ranging from 77 to 300 K, vibrating sample magnetometer, and x-ray diffraction. Saturation magnetization and coercivity were found to be 49 emu/g and nearly 0 Oe at room temperature, respectively. A singlet Mössbauer spectrum was observed at room temperature, implying superparamagnetic behavior of the particles, while a two-sextet spectrum was observed at 77 K. The particle size in this study is about 7 nm, which is smaller than the superparamagnetic size of 26 nm as calculated from Neel’s theory of single domain particles. After having aged these particles for 19 months, all magnetic properties and their original shapes were retained. Superparmagnetic magnetite nanoparticles synthesized in this study can be applied to microbead applications of a biosensor.

化学的共沈法による（Ｓｒ・Ｂａ）‐Ｌａ‐Ｃｏ系Ｍ型フェライト微粒子の磁気特性

(Sr⋅Ba)-La-Co M-type ferrite fine particles were prepared by the chemical coprecipitation and subsequent heat-treatment method. The chemical reagents used for the experiment were FeCl3⋅6H2O, BaCl2⋅6H2O, SrCl2.6H2O, LaCl3⋅7H2O, and CoCl2.6H2O. The chemical coprecipitation process was applied to the samples having the formula. {(SrO)1-x⋅(BaO)x⋅n/2(Fe2O3)}100-Y-Z(La2O3)Y(CoO)Z (n=6.0-12.0, x=0.0-1.0, y=1.0-10.0, z=1.0-10.0). The solution containing Sr2+, Ba2+, Fe3+, La3+, and Cot2+ was poured into solution of NaOH (pH=13.0). The precipitated products were boiled for 2h and they were carefully washed with water and dried. The obtained fine particles were heated at 950 to 1100°C for 2h in air to obtain the single phase of (Sr⋅Ba)-La-Co M-type ferrite fine particles. The best magnetic properties were observed for the sample with the composition of {(SrO)0.8⋅(BaO)0.2⋅3.5(Fe2O3)} 88.0 (La2O3)6.0(CoO)6.0, and magnetic properties were as follows: σs= 84.8 × 10-6 Wb⋅m/kg (67.5 emu/g), σr=42.8 × 10-6 Wb⋅m/kg (34.1 emu/g), HcJ=476.6 kA/m (5.98 kOe) and Tc=452.6°C.

磁性材料 化学的共沈法によるＢａ‐Ｌａ‐Ｃｏ系Ｍ型フェライト微粒子の磁気特性

Ba-La-Co M-type ferrite fine particles were prepared by the chemical coprecipitation process and a heat treatment. The chemical reagents used for the experiment were FeCl3⋅6H2O, BaCl2.6H2O, LaCl3⋅7H2O, and CoCl2.6H2O. The chemical coprecipitation process was applied to the samples having the formula {(BaO⋅n/2(Fe2O3))100-x-y(La2O3)x (CoO)y (n=7.0-12.0, x=1.0-10.0, y=1.0-10.0) the solution containing Ba2+, Fe3+, La3+, and Co2+ was poured into solution of NaOH (pH=13.0). The precipitated products were boiled for 2hs and they were carefully washed with water and dried. The obtained fine particles were heated at 950 to 1100°C for 2hs in air to obtain the single phase of Ba-La-Co M-type ferrite fine particles. The best magnetic properties were observed for the sample with the composition of {(BaO⋅n/2(Fe2O3))94.0(La2O3)3.0(CoO)3.0. The maximum values of magnetic properties were as follows: σ5=87.1×10-6 Wb⋅m/kg(69.3 emu/g), σr=42.9×10-6Wb⋅m/kg (34.1 emu/g), HCJ=469.5 kA/m (5.82 kOe) and TC= 456.4°C.

Sintering and electrical properties of coprecipitation prepared Ce 0.8Y 0.2O 1.9 ceramics

Fine Ce 0.8Y 0.2O 1.9 (YDC) powders were prepared by a chemical coprecipitation process. The effect of the calcination temperature on the sinterability and electrical conductivity of the resulting YDC ceramics was investigated. Broadening degrees of the X-ray peaks of YDC powders indicate that the crystallite sizes of the powders significantly increase with the calcination temperature from 500 to 1000°C, which is consistent with the transmission electron microscopy (TEM) results. Scanning electron microscopy (SEM) photographs of the surface microstructures revealed that YDC ceramics from the powders calcined at temperatures 500–750°C become highly dense (over 98% theoretical density) when sintered at 1500°C, while the ceramic calcined at 1000°C reached only 93% relative density. On the other hand, the average grain size of specimens obtained from powders obtained at increasing calcination temperature decreased from 2.5 to 1 μm, correspondingly. These results are attributed to the high sintering activity and grain growth rate at the same sintering condition for the finer powders calcined at lower temperature. The electrical measurement by ac impedance spectroscopy shows that the specimen from the powder calcined at 750°C exhibits the highest electrical conductivity, approximately 4 Sm −1 at 750°C in air.

A study on the novel gas-sensing solid solution material (Cd 1− xAg x) 2Sb 2O 6.8

In this paper, the ultrafine powders of the solid solution (Cd 1− x Ag x ) 2Sb 2O 6.8 were prepared by a chemical coprecipitation process. The powders were proved by X-ray diffraction (XRD) to bear a similar defect pyrochlore structure to Cd 2Sb 2O 6.8 when x≤10 mol%. The results show that the doped silver ion affects the conductance as well as the gas-sensing properties, and the conductance decreases steadily with the increasing silver content while the sensitivity of the sample with x=0.05 to 1000 ppm C 2H 5OH is about five times that of the pure Cd 2Sb 2O 6.8. Meanwhile, the doping lifted the selectivity toward gasoline and reduced the optimum operating temperature. All of these suggest this solid solution as a candidate for practical alcohol sensors.

Morphological, structural and magnetic characteristics of Co-Ti and Co-Sn substituted Ba-ferrite particles for magnetic recording

Co-Ti substituted barium ferrite particles were prepared by the glass-ceramic method in the BaCO 3-B 2O 3-Fe 2O 3 glass system. The crystallization process of glass flakes, the morphology and magnetic properties of doped barium ferrite particles have been investigated. The finely divided, hexagonal plate-like Co-Ti and Co-Sn substituted barium ferrite particles were prepared by a method which combines the chemical coprecipitation process and the salt flux process. The formation process of these particles was investigated. The correlation between the magnetic properties, the particle morphology and the degrees of Co-Ti and Co-Sn substitutions of Ba-ferrite particles are studied. By the law of approach to saturation the effective anisotropy field H A and crystalline anisotropy constant K 1 were estimated. It was found that BaFe 12−2 x Co x Sn x O 19 with x = 1.10–1.40 have a very low temperature coefficient of coercivity at temperature range from 0 to 60°C and suitable magnetic characteristics for magnetic recording.