Spray Co-precipitation Method Research Articles

Coordination polymers as precursors of simple and complex oxides

AbstractCoordination polymers (CPs) are assembled from metal ions and organic linker molecules. Here, we demonstrate that CPs can be used as precursors for simple and complex oxide synthesis. First, we investigated the conditions for linker solutions in which CP was obtained as precipitate only by mixing and stirring the solutions for each of the 28 metal–ion aqueous solutions. Evaluation of the crystalline phase of the samples obtained by firing the precipitates revealed that CPs could be used as precursors of simple oxides for 21 metal ions. Next, we conducted experiments to prepare precursors of 10 complex oxides with an AnBnOm composition containing equimolar amounts of metal ions. Seven complex oxides were successfully synthesized. Three of them were complex oxides that could not be synthesized by the spray coprecipitation method. The present method has a comparable precursor preparation capability to the spray coprecipitation method. Because of the much shorter time for the precursor synthesis, the present method should be useful for parallel and automated experiments.

Synthesis of highly sinterable Tb2O3 powders by spray coprecipitation for transparent ceramics: The influence of ammonium hydrogen carbonate to metal ions molar ratio

A modified spray coprecipitation method was used to prepare highly sinterable Tb2O3 nanopowders. The effects of R (molar ratio of ammonium hydrogen carbonate to metal ions) were studied throughout the preparation process. The characteristics of the precursors and Tb2O3 powders were determined using analytical techniques including XRD, FTIR, TG-DSC, and SEM. It was discovered that altering the R values significantly affected the chemical components, microstructure, and homogeneity of the precursors and oxide powders. Ultrafine, monodispersed, and spherical terbium (III) oxide powders were obtained when R = 4, while inhomogeneous rhombic flake-shaped particles were prepared with R ≥ 5. The powders calcined at 800 °C produced Tb2O3 ceramics with the highest optical transmittance of 64.08% at a wavelength of 1064 nm via flowing hydrogen atmosphere sintering at 1520 °C for 10 h. The Verdet constant measured at 632.8 nm for the obtained Tb2O3 sample was −466.3 rad T−1 m−1, which was approximately 3.5 times that of the Tb3Ga5O12 single crystal.

Microwave Absorption Properties of Nanocrystalline Nixzn1-Xfe2o4 Synthesized by Spraying-Coprecipitation Method

Microwave Absorption Properties of Nanocrystalline Nixzn1-Xfe2o4 Synthesized by Spraying-Coprecipitation Method

Synthesis of highly sinterable Tm,Ho:(Lu1-xScx)2O3 powders by spray co-precipitation for transparent ceramics: Influence of the variable x

Highly sinterable Tm,Ho:(Lu1-xScx)2O3 nanopowders were synthesized by a spray co-precipitation method. The influences of the calcination temperatures and x values on the morphology and composition of the powders were studied. The results indicated that the precursor gradually formed needlelike structures with increasing x values, and the powders calcined at 1100 °C for 2 h exhibited the highest uniformity and sintering activity. Using the powders calcined at 1100 °C, the Tm,Ho:(Lu1-xScx)2O3 ceramics with the highest in-line transmittance of 79.80% at 2090 nm were fabricated by vacuum sintering at 1550 °C for 10 h and further hot isostatic pressing under 190 MPa at 1700 °C. Owing to the disordered crystal structure of the (Lu1-xScx)2O3, the grain size of the ceramics decreased from 1.72 ìm to 1.16 ìm, and the emission spectra showed some variation with increasing x values. This work demonstrates promise in facilitating the production of Tm,Ho:(Lu1-xScx)2O3 transparent ceramics for their use in 2 ìm ultrashort laser pulse and other applications.

Synthesis of highly sinterable Yb:Lu2O3 nanopowders via spray co-precipitation for transparent ceramics

Abstract Highly sinterable Yb:Lu2O3 nano-powders without hard agglomeration were synthesized via a highly efficient spray co-precipitation method. The effects of the spray speeds on morphology and composition of the powders were investigated. The results showed that the composition and dispersion of precursor powders changed with the spray speed. When the spray speed reached 40 mL/min, the particles were spherical and showed higher uniformity. The pure phase Yb:Lu2O3 powder was obtained after calcining at 1000 °C for 2 h. The calcined powders were ball milled and dry-formed to prepare green body. Then the Yb:Lu2O3 transparent ceramic was fabricated by vacuum sintering at 1500 °C for 8 h and further hot isostatic pressing in an argon atmosphere.. The in-line optical transmittance of Yb:Lu2O3 transparent ceramic reached 82.05%@1000 nm and 81.08%@400 nm, respectively, and it had submicron level average grain size, which is an effective way to improve the optical properties of the transparent ceramic.

High efficiency synthesis of Nd:YAG powder by a spray co-precipitation method for transparent ceramics

A spray co-precipitation method was developed to efficiently synthesize Nd:YAG nano-powders. The effects of spray speeds and solution concentrations on the crystallization processes of calcined precursors have been studied. The results indicated that the pure phase of YAG could be obtained by three different crystallization processes owing to different homogeneity levels of Y and Al mixing. Pure YAG powder was obtained at 850 °C and the phase purity persisted to 1600 °C. Using the obtained powders, transparent ceramics with the in-line transmittance up to 80.2%@400 nm and 83.1%@1064 nm were fabricated by gel-casting method and hot isostatic pressing sintering. Furthermore, the microstructure and laser properties of the transparent ceramics have been measured. The maximum laser output of 7.015 W has been obtained with an oscillation threshold and a slope efficiency of 0.235 W and 59.4%, respectively.

A novel spray co-precipitation method to prepare nanocrystalline Y2O3 powders for transparent ceramics

A novel spray co-precipitation method was adopted to synthesize well dispersed nanocrystalline Y2O3 powders for transparent ceramics. Several analytic techniques such as XRD, SEM, BET and UV–Vis–NIR spectrophotometer were used to determine the properties of coprecipitated powders, and the microstructure and optical properties of as-fabricated ceramics. The influences of the aging time on powders and ceramics were systematically investigated. Precursors were completely reached to yield the Y2O3 phase after being calcined at 1250 °C in air. The calcined Y2O3 powders exhibited an approximately spherical morphology with narrow size distribution and weak agglomeration, with mean particle size of ~140 nm. The co-precipitated nanopowders with an aging time of 12 h exhibited the best sintering activity due to the low agglomeration, and the in-line transmittance of Y2O3 ceramic sintered at 1800 °C for 8 h in vacuum reached to 77.2% at 1064 nm (1 mm thickness).

Cation distribution in CuFe2O4 nanoparticles: Effects of Ni doping on magnetic properties

The Cu1−xNixFe2O4 nanoparticles (with x = 0, 0.3, 0.5, 0.7, and 1) were synthesized by using spray co-precipitation method at annealing temperature Ta = 900 °C in air for 5 h. The crystal structure, microstructure, oxidation state, and magnetic properties of the samples were characterized by using X-ray diffraction, synchrotron X-ray diffraction, scanning electron microscopy, X-ray absorption spectroscopy, and vibrating sample magnetometer. It was shown that all the samples have cubic structure. Lattice constant and grain size decrease, while the Curie temperature TC increases with increasing of Ni2+ content. A small amount of Fe2+ was found in all the samples. Cation distribution was determined by using a combination of magnetization measurements, extended X-ray absorption fine structure analysis, and Rietveld refinement from synchrotron X-ray diffraction data. It was indicated that Ni2+ ions occupy in octahedral site only, while Cu2+ ions distribute in both tetrahedral and octahedral sites. The variation of magnetic parameters is discussed based on Ni2+ concentration, grain size, the cation distribution, surface effect, and the presence of Fe2+ ion in the samples.

Structural and Magnetic Characterization of Copper Ferrites Prepared by Using Spray Co-Precipitation Method

Structural and Magnetic Characterization of Copper Ferrites Prepared by Using Spray Co-Precipitation Method

Preparation of YAG nano-powders via an ultrasonic spray co-precipitation method

Nanometer-sized particles (1–100 nm) are of considerable interest for a wide variety of applications, due to their unique and improved properties primarily determined by size. In this study, homogenously dispersed nanocrystalline YAG powders were synthesized by calcination of the YAG precursors prepared by an ultrasonic spray method. The effects of spray droplets moving path, calcination temperature and aluminum ion concentration on the preparation of pure-phase YAG powders were intensively studied. The results show that the well-dispersed YAG nano-powders can be prepared by this ultrasonic spray co-precipitation method. Well-crystallized YAG powers can be generated when the precursors, produced through top symmetric spray with ammonia as precipitation agent, are calcined at 1000 °C for 3 h. The average size of YAG particles is about 50 nm and well-dispersed.

Microstructure and magnetic properties of nanocrystalline Co1−xZnxFe2O4 ferrites

Nanocrystalline Co1−xZnxFe2O4 ferrites with spinel phase were prepared by a spraying-coprecipitation method. Experimental results indicate that the average grain size of Co1−xZnxFe2O4 ferrites calcined at 973K for 1.5h is about 32nm and more uniform. The obtained smaller and more uniform particle size can be ascribed to the effect of entrainment and turbulence for jet in the spraying-coprecipitation approach. Magnetic property shows that the saturation magnetization of the nanocrystalline Co0.7Zn0.3Fe2O4 ferrite is enhanced to 83.4Am2kg−1. Moreover, the remanent magnetization and coercivity of nanocrystalline Co1−xZnxFe2O4 ferrites decrease with the increase of zinc concentration. The specific saturation magnetization and remanent magnetization of Co0.5Zn0.5Fe2O4 ferrite increases with the increasing grain size. The maximum coercivity of Co0.5Zn0.5Fe2O4 ferrite reaches up to 7.6×103Am−1, as the grain size is 32nm. The value of ferromagnetic exchange length in Co0.5Zn0.5Fe2O4 ferrite is about 42nm. The magnetic behavior of Co0.5Zn0.5Fe2O4 ferrites may be attributed to the effect of nanometer size of magnetic particles.

Microstructure and magnetic properties of nanocrystalline (Ni0·5Zn0·5)xCo1−xFe2O4 ferrite by spraying co-precipitation method

Nanocrystalline (Ni0·5Zn0·5)xCo1−xFe2O4 with 0⩽x⩽1·0 are prepared by spraying co-precipitation method. Their microstructure and magnetic properties are investigated. The results show that nanocrystalline (Ni0·5Zn0·5)xCo1−xFe2O4 ferrites are spinel phase. Coercivity and retentivity of specimens increase with cobalt content. The enhancement of the saturation magnetisation up to a maximum value of 102·1 A m2 kg−1 in nanocrystalline (Ni0·5Zn0·5)0·5Co0·5Fe2O4 ferrite is observed. This can be attributed to the change of the net magnetic moment between the sublattices of structure for the substitution of Ni2+ and Zn2+ ions with Co2+ ions. The coercivity of nanocrystalline (Ni0·5Zn0·5)0·5Co0·5Fe2O4 ferrite increases monotonously in the grain size regime d<69 nm, and then coercivity decreases with grain size. The initial increase in coercivity of the nanocrystalline (Ni0·5Zn0·5)0·5Co0·5Fe2O4 ferrite with increasing size is due to the enhanced role of the surface and its strong random anisotropy.

The Enhanced Saturation Magnetization of Nanocrystalline (Ni0.5Zn0.5)1-xCoxFe2O4 Ferrite

Single spinel phase nanocrystalline ferrite (Ni0.5Zn0.5)1-XCoxFe2O4was prepared using the spraying co-precipitation method. The coercivity of prepared (Ni0.5Zn0.5)1-XCoxFe2O4 increases with an increasing content of cobalt. The enhancement of the saturation magnetization was observed up to the maximum value of 102.1emu/g as x was 0.5. This can be attributed to the substitution of the Ni2+ and Zn2+ ions with Co2+ ions. This changed the net magnetic moment between the sublattices of structure.

Effect of the Grain Size on Magnetic Properties of Nanocrystalline CoFe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; Ferrite

Nanocrystalline CoFe2O4 ferrite have been synthesized by a spraying-coprecipitation method. X-ray diffraction (XRD) and Transmission electron microscope (TEM) confirmed the formation of single-phase CoFe2O4 ferrite nanoparticles in the range 10 nm ~ 100 nm depending on the calcining temperature. The magnetic measurements show that specific saturation magnetization of nanocrystalline CoFe2O4 ferrite increases from 36.1 A•m2•kg-1 to 88.6 A•m2•kg-1 as grain size increases from 12 nm to 98 nm. The coercivity shows a peak with grain size, peaking at around 43 nm. The magnetic behaviour of nanocrystalline CoFe2O4 ferrite might be attributed to the effects of surface and random anisotropy.

Effect of Zn2+ content on the microstructure and magnetic properties of nanocrystalline Ni1−x Zn x Fe2O4 ferrite by a spraying-coprecipitation method

Nanocrystalline Ni1−xZnxFe2O4 ferrites with 0⩽x⩽1 were successfully prepared by a spraying-coprecipitation method. The microstructure was investigated by using XRD and TEM. Magnetic properties were measured with vibrating sample magnetometer (VSM) at room temperature. The results show that the grain size of nanocrystalline Ni1−xZnxFe2O4 ferrite calcined at 600 °C for 1.5 h is about 30 nm. Lattice parameter and specific saturation magnetization Ms of nanocrystalline Ni1−xZnxFe2O4 ferrite increase with the Zn2+ ions content at room temperature, and maximum Ms is 66.8 A · m2 · kg−1 as the Zn2+ ions content is around 0.5, and coercivity Hc of the nanocrystalline Ni1−xZnxFe2O4 ferrite decreases with Zn2+ ions content.

Synthesis of carboxymethyl-chitosan-bound magnetic nanoparticles by the spraying co-precipitation method

Magnetic Fe 3 O 4 nanoparticles functionalized with carboxymethyl chitosan were prepared by means of the spraying co-precipitation method. The synthesis reaction is discussed in terms of a nucleus growth mechanism. The results presented in this report show that magnetic particles should prove suitable as nanomagnetic carriers of drugs, and demonstrated that the spraying co-precipitation process is a better production method for this kind of magnetic particle as it can be automated and requires fewer procedures.

Synthesis, Microstructure and Magnetic Properties of Nanocrystalline Ni-Zn Ferrite by a Modified Wet Chemical Method

Nanocrystalline Ni1-xZnxFe2O4 ferrites with 0 ≤ x ≤ 1 were prepared by sprayingcoprecipitation method. The microstructure was investigated by TG-DSC, XRD, SEM, TEM and BET. Magnetic properties were measured with vibrating sample magnetometer at room temperature. The results showed that uniform and fine nanocrystalline Ni1-xZnxFe2O4 ferrites are obtained. The grain size of sample calcined at 600°C for 1.5h is about 30nm. There are a few agglomerates with average sizes below 100nm. The specific saturation magnetization, Ms, of the sample increases with increasing Zn2+ concent x at room temperature, and the maximum Ms is 66.8 A·m2·kg-1 as the Zn2+ content x is around 0.5mol. As calcining temperature increased from 400°C to 1050°C, the Ms of Ni0.5Zn0.5Fe2O4 ferrite increases from 40.2 A·m2·kg-1 to 75.6 A·m2·kg-1. The coercivity maximum is about 5.97 kA·m-1 as its critical grain size is about 62.0nm. The relation between coercivity and grain size for nanocrystalline Ni0.5Zn0.5Fe2O4 ferrite may be explained based on random anisotropy theory.

Microstructure and magnetic characteristics of nanocrystalline Ni0.5Zn0.5ferrite synthesized by a spraying–coprecipitation method

Nanocrystalline Ni0.5Zn0.5 ferrite with average grain sizes ranging from 10 to 100 nm is prepared by using a spraying–coprecipitation method. The results indicate that the nanocrystalline Ni0.5Zn0.5 ferrite is ferromagnetic without the superparamagnetic phenomenon observed at room temperature. Specific saturation magnetization of nanocrys-talline Ni0.5Zn0.5 ferrite increases from 40.2 to 75.6 emu/g as grain size increases from 11 to 94nm. Coercivity of nanocrystalline Ni0.5Zn0.5 ferrite increases monotonically when d < 62 nm. The relationship between the coercivity and the mean grain size is well fitted into a relation Hc ~ d3. A theoretically evaluated value of the critical grain size is 141nm larger than the experimental value 62nm for nanocrystalline Ni0.5Zn0.5 ferrite. The magnetic behaviour of nanocrystalline Ni0.5Zn0.5 ferrite may be explained by using the random anisotropy theory.

Silver-Metal Oxide Contact Materials Fabricated by Spray Coprecipitation

This paper describes the development of a highly versatile technique for fabricating improved silver-metal oxide contact materials. The spray coprecipitation method, invented at The Allen Clark Research Centre and patented [1] for Plessey Inc., offers both economic and technical advantages over existing processes for making silvercadmium oxide such as conventional internal oxidation of fabricated alloy, conventional powder metallurgy, and internal oxidation of alloy powder/shot. The main technical advantages are the following: a) controlled microstructural perfection in the uniform fineness and long-range homogeneity of the oxide dispersion; b) unlimited composition with respect to both quantity and type of oxide (not limited to oxides of metals with solid solubility in silver); c) ease of doping with beneficial ternary additons without influencing the microstructure, which is simply controlled by the sintering time and temperature. The method relies on converting, to some extent, the intimate dispersion provided on a molecular scale in mixed aqueous solutions to the solid state by instantaneous coprecipitation from small sprayed droplets of mixed nitrates solutions. This paper concentrates in the main on the application of the process to the fabrication of traditional silver-cadmium oxide, but examples are also given of the production of silver-zinc oxide, silver-tin oxide, and silver-lanthanum oxide materials which demonstrate the versatility and simplicity of the method. IEC AC-4 erosion test results are presented for spray coprecipitated Ag-15 weight percent CdO.