Traditional Co-precipitation Method Research Articles

Synthesis of LiAl2-layered double hydroxides for CO2capture over a wide temperature range

Although there are many reports on layered double hydroxide (LDH) derived CO2 adsorbents, none of them have studied the special case of LiAl2 LDHs. Here we report the first detailed investigation of the performance of LiAl2 LDHs as novel CO2 adsorbents. LiAl2 LDHs were synthesized using both traditional coprecipitation and gibbsite intercalation methods. All the materials were thoroughly characterized using XRD, SEM, TEM, FTIR, BET, and TGA. The CO2 capture performance of these LDHs were investigated as a function of charge compensating anions, Li/Al ratio in preparation solution, calcination temperature, adsorption temperature, and doping with K2CO3. The data indicated that LiAl2 LDHs derived compounds can be used as CO2 adsorbents over a wide temperature range (60–400 °C), with a CO2 capture capacity of 0.94 and 0.51 mmol g−1 at 60 and 200 °C, respectively. By doping LiAl2–CO3 LDH with 20 wt% K2CO3, the CO2 adsorption capacity was increased up to 1.27 and 0.83 mmol g−1 at 60 and 200 °C, respectively. CO2 adsorption–desorption cycling studies showed that both pure LiAl2 LDH and the K2CO3-promoted LiAl2 LDH had stable CO2 capture performance even after 22 cycles. Considering its high CO2 capture capacity and good cycling stability, LiAl2 LDH based novel CO2 adsorbents have significant potential for CO2 capture applications.

Ultrasonic/microwave-assisted co-precipitation method in the synthesis of Li1.1Mn0.433Ni0.233Co0.233O2 cathode material for lithium-ion batteries

Ultrasonic/microwave-assisted co-precipitation method (UMCP) is proposed to synthesize lithium-rich material, Li1.1Mn0.433Ni0.233Co0.233O2. The synthesized precursors from UMCP were denser, and the final products showed improved crystallinity, as well as lower cation disordering, caused by the homogeneous dispersed reagents introduced by the ultrasonic effect, resulting in higher discharge capacity and better cycling performance compared with those from traditional co-precipitation method. The sample synthesized by UMCP exhibited a capacity of 260mAhg−1 at 0.1C charge/discharge rate and 207mAhg−1 after 50 cycles, while the discharge capacity of the control sample was only 212mAhg−1 for the first cycle and 180mAhg−1 after 20 cycles.

Self-directed chemical synthesis of lithium-rich layered oxide Li[Li0.2Ni0.2Mn0.6]O2 with tightly interconnected particles as cathode of lithium ion batteries with improved rate capability

A novel method, self-directed chemical method, is proposed to synthesize lithium-rich layered oxide Li[Li0.2Ni0.2Mn0.6]O2 as cathode of lithium ion batteries with improved rate capability. In this method, Li2CO3 powder that has low dissolvability in aqueous solution is introduced as precipitating agent to induce the formation of transition-metal carbonate, resulting in the precursor Ni0.25Mn0.75CO3 with a hierarchical structure: secondary particles assembled with interconnected primary particles. This hierarchical structure remains in subsequent product (Li[Li0.2Ni0.2Mn0.6]O2-T). Electrochemical measurements indicates that Li[Li0.2Ni0.2Mn0.6]O2-T delivers a capacity of 222mAhg−1 at 1st cycle (0.05C, 1C=263mAhg−1) and holds 207mAhg−1 at 50th cycle, which is slightly better than the sample from a traditional co-precipitation method (Li[Li0.2Ni0.2Mn0.6]O2-L). More importantly, Li[Li0.2Ni0.2Mn0.6]O2-T is able to stably offer 156mAhg−1 at 0.5C, 136mAhg−1 at 1C and 108mAhg−1 at 2C, much better than Li[Li0.2Ni0.2Mn0.6]O2-L. The improved performance is attributed to the tightly interconnected structure and smaller particle size, which facilitates the diffusion of Li+ ions in the material bulk and reduces the barrier of charge transfer reaction.

Methotrexate intercalated layered double hydroxides with different particle sizes: Structural study and Controlled release properties

To study the influence of particle size on release properties, drug efficacy and other properties, a series of methotrexate intercalated layered double hydroxides (MTX/LDHs) nanohybrids with different particle sizes were synthesized through traditional coprecipitation method, by using the mixture of water and polyethylene glycol (volume ratio is 3:1) as solvent. The relationship between particle size and hydrothermal treatment conditions (i.e., time and temperature) had been systematically investigated, and the results indicate that the particle size can be precisely controlled between 70 and 300nm. Elemental C/H/N and inductive coupled plasma (ICP) analysis indicated that different hydrothermal treatment almost has no effect on compositions of the nanohybrids. X-ray diffraction (XRD) patterns and fourier transform infrared spectroscopy (FTIR) investigations manifested the successful intercalation of MTX anions. MTX/LDHs particles exhibited hexagonal platelet morphology with round corner, due to the adsorption of MTX anions on positively charged LDHs surface. In addition, the crystallinity of MTX/LDHs increased with the particle diameters and the thermal stability of MTX anions was enhanced by holding together with LDHs layers. The in vitro release showed that bigger particles have much longer release duration, and the bioassay tests indicated that bigger particles are more efficient in the suppression of the tumor cells.

Synthesis of Cerium‐Doped Gd3(Al,Ga)5O12 Powder for Ceramic Scintillators with Ultrasonic‐Assisted Chemical Coprecipitation Method

Cerium‐doped Gd3(Al,Ga)5O12 powders have been synthesized with ultrasonic‐assisted chemical coprecipitation method (UACC), and the traditional chemical coprecipitation method (CC) was also employed for comparison. The structure and morphology of powders were investigated by XRD, BET, and TEM. The powders were used for preparing ceramics at different temperatures. The specific surface areas of UACC and CC powders calcined at 800°C were 66 and 29 m2/g, respectively. Ceramics derived from UACC and CC powders were sintered at 1600°C, and the densities are 6.67 and 6.48 g/cm3, respectively. UACC is an attractive method for synthesizing GAGG powder for preparing ceramic scintillators.

Determination of ultratrace amounts of plutonium in high saline groundwater by inductively coupled plasma mass spectrometry

For determination of ultratrace amounts of plutonium in high saline groundwater, large-volume sampling and preconcentration are necessary. However, traditional co-precipitation methods, such as Fe(OH)3, Ca(OH)2–Mg(OH)2 and hydroxide-carbonate co-precipitation, are unable to meet the requirements of preconcentration of the ultratrace plutonium in high saline groundwater. In this paper, the ultratrace plutonium in high saline groundwater was concentrated by sequential co-precipitation with MnO2 and Fe(OH)3, and purified by two-stage anion-exchange separation on Dowex1 × 4 resin column. Quadrupole ICP-MS was employed for the determination of 239Pu with 242Pu spiked. After co-precipitation and purification, the major matrix elements were significantly decreased to μg mL−1 level and decontamination factor of uranium is better than 106. The detection limit for 239Pu in 50 L high saline water is 2.1 × 10−16 g L−1. Three high saline fountain samples (total dissolved solids more than 20 g L−1) from Dunhuang region of China were analyzed using this method. The concentrations of 239Pu in these samples were 0.48 ± 0.2 × 10−15, 1.40 ± 0.10 × 10−15 and 2.13 ± 0.21 × 10−15 g L−1 respectively. The recovery obtained for 7 pg of 242Pu spiked into real high saline-water samples was all above 70 %.

Nanostructured LiNi0.5Mn1.5O4 cathode material synthesized by polymer-assisted co-precipitation method with improved rate capability

The polymer-assisted oxalate co-precipitation method has been developed to synthesize nanostructured LiNi0.5Mn1.5O4. In this method, polyacrylic acid (PAA) as a dispersant agent was applied in the co-precipitation process to achieve the well-dispersed and homogenous precursor route. The obtained powder possesses small particle around 50–100nm as compared to the one synthesized by traditional co-precipitation method. Besides, the porous texture was also found in as-fabricated LiNi0.5Mn1.5O4. The X-ray diffraction reveals the well-crystallized cubic spinel structure without the presence of undesired impurities, such as NiO or LixNi1−xO, commonly found in other fabrication method. An excellent cycling stability is obtained with the capacity retention over 90% after 100 cycles in 1C at room temperature. Moreover, the superior rate capability was also derived by nanostructured LiNi0.5Mn1.5O4, in which the discharge capacity in 5 and 7C is around 110 and 100mAhg−1, respectively. The greatly enhanced rate capability is attributed to the significantly shortened Li-ion diffusion pathway, associating with the nano-textured particle morphology.

Influence of Ru substitution on Li-rich 0.55Li2MnO3·0.45LiNi1/3Co1/3Mn1/3O2 cathode for Li-ion batteries

Li-rich cathode 0.55Li2MnO3·0.45LiNi1/3Co1/3Mn1/3O2 or written in a solid solution form Li(Li0.20Mn0.54Ni0.13Co0.13)O2 doped with trace Ru is synthesized using a traditional co-precipitation method. The structural and morphological characterizations are carried out by employing inductively coupled plasma emission spectrometry (ICP), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Ru doping causes variation of lattice constants in both Li2MnO3 and LiNi1/3Co1/3Mn1/3O2 components according to the results of Rietveld refinement. Electrochemical measurement shows that Li(Li0.19Mn0.54Ni0.13Co0.12Ru0.01)O2 possesses the best performance, especially at high rate. A discharge capacity as high as 182mAhg−1 at a current density of 500mAg−1 (2C) is achieved with a capacity fade of as low as 0.06% per cycle in the following 700 cycles. Such improvement is associated with the prominent appearance of spinel-like regions transferred from the original Li2MnO3 component in which Ru facilitates the phase transformation via enhancing the ability of Li diffusion in both Li2MnO3 and LiNi1/3Co1/3Mn1/3O2 components. The improvement in Li diffusion is also confirmed from the electrochemical impedance spectroscopy (EIS) analysis.

Post-synthetic treatments on Ni xMn xCo 1 − 2 x(OH) 2 for the preparation of lithium metal oxides

A series of hydroxides Ni x Mn x Co (1−2 x) (OH) 2 for x = 0.00–0.50 were prepared. These hydroxides were used as the precursors in the synthesis of electrochemical active lithiated mixed metal oxides, LiNi x Mn x Co (1 − 2 x) O 2. The traditional co-precipitation method was used to synthesize the hydroxides and the effect of different post-synthetic treatments were tested. The solutions after co-precipitation of the hydroxides were heated under hydrothermal or microwave assisted hydrothermal conditions at 180 °C. All samples were analyzed with X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. We observed that the hydroxides undergo oxidation to an oxyhydroxide phase as the stoichiometry varies during their synthesis and with post-synthetic treatments. As the concentration of Ni and Mn increases in the sample, a mixture of both hydroxide and oxyhydroxide phases is obtained. SEM images demonstrate a sintering effect on the hydroxide particles after post-synthetic treatment, while XRD measurements on these samples show an increase in crystallinity and reduced turbostratic disorder. The oxides synthesized from these precursors demonstrate similar electrochemical performance with one another.

A Novel Route for Collagen/ Hydroxyapatite Preparation by Enzymatic Decomposition of Urea

This article presents a new route for preparing collagen/hydroxyapatite (Coll/HA) composite. Urease-catalyzed decomposition of urea was used for the first time to prepare Coll/HA. Acting as an automatic pH controller, urea totally eliminated the traditional requirement of an external base additive and facilitated procedures for synthesis as a result. This Coll/HA complex was characterized by Fourier transformed infrared spectroscopy, X-ray diffraction, laser diffraction particle size analyzer, scanning electron microscope (SEM), and transmission electron microscopy. The results indicated that chemical and crystallographic properties of this complex were similar to those of the natural bone and other Coll/HA systems. Laser diffraction particle size measurement and SEM showed that this Coll/HA sample evidenced smaller particle size and narrower particle size distribution than other Coll/HA complex prepared by the traditional co-precipitation method.

Influence of preparation method on the catalytic activities of CuO/Ce0.67Zr0.33O2 catalysts in CO + O2 reaction

Ce0.67Zr0.33O2 solid solutions synthesized by traditional co-precipitation method (hereafter donated as CZ-CP) and hydrothermal method (hereafter donated as CZ-HT) were used as supports for preparing a series of CuO/Ce0.67Zr0.33O2 catalysts. High resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), temperature-programmed reduction (TPR), CO adsorption in situ Fourier transform infrared spectroscopy (CO in situ FT-IR) and the activity of CO oxidation model reaction at low temperature (<200°C) were used to approach the properties of the catalysts. The results showed that the Ce0.67Zr0.33O2 prepared by hydrothermal method facilitate the formation and stabilization of Cu+ on the surface of support and thus the activity for CO+O2 reaction was improved. A tentative model was suggested that the difference in the preferentially exposed plane of CZ-CP and CZ-HT leads to the great difference in dispersion, reduction and reaction activity of the dispersed copper oxide species on these two supports.

Exchange-biased NiFe2O4/NiO nanocomposites derived from NiFe-layered double hydroxides as a single precursor

NiFe2O4 nanoparticles (<10 nm) embedded in a NiO matrix have been fabricated by calcining the corresponding NiIIFeIII-layered double hydroxide (LDH) precursors at high temperature (500 °C). Compared with the NiFe2O4/NiO nanocomposite obtained by calcination of a precursor prepared by a traditional chemical coprecipitation method, those derived from NiFe-LDH precursors show much higher blocking temperatures (T B) (˜380 K). The enhanced magnetic stability can be ascribed to the much stronger interfacial interaction between NiFe2O4 and NiO phases due to the topotactic nature of the transformation of the LDH precursor to the NiFe2O4/NiO composite material. Through tuning the NiII/FeIII molar ratio of the NiFe-LDH precursor, the NiFe2O4 concentration can be precisely controlled, and the T B value as well as the magnetic properties of the final material can also be regulated. This work represents a successful example of the fabrication of ferro(ferri)magnetic (FM)/antiferrimagnetic (AFM) systems with high magnetic stability from LDH precursors. This method is general and may be readily extended to other FM/AFM systems due to the wide range of available LDH precursors.

The dependence of the oxygen-exchange properties of Ce0.5Zr0.5O2 on the method of synthesis

The oxygen-exchange properties of Ce0.5Zr0.5O2 samples prepared by the traditional coprecipitation method with the use of a biotemplate (pine wood sawdust) were studied by the temperature-programmed reduction and oxidation methods. The use of the template and the presence of alkali and alkaline-earth metal cations in it provides a high mobility of oxygen and a high capacity with respect to oxygen in the biomorphic oxide. Impurities cause the segregation of Ce- and Zr-enriched phases under high-temperature treatment conditions, which worsens the redox properties of the biomorphic sample. Nevertheless, the ability of the biomorphic sample to play the role of an “oxygen buffer” remains high compared with the coprecipitated oxide subjected to similar treatments.

Plasma-Pretreated Catalyst for Methanol Synthesis From Syngas

A new catalyst preparation method by combining the traditional coprecipitation method with an oxygen plasma pretreatment was developed in this paper. The ternary Cu/Zn/Al catalyst powders were first prepared by coprecipitation method, and then pretreated by the plasma in a fluidized-bed dielectric barrier discharge reactor with a carrier gas of a molar ratio of O2/Ar = 5/95. Then, the plasma-pretreated catalyst was conducted with the methanol synthesis test at the following conditions: H2/CO/N2 = 64/32/4, Q = 900 seem, P = 4 MPa, and T = 255degC. The plasma pretreatment could enhance the catalytic activity, e.g., the methanol selectivity increased from 28% to 72% and the methanol yield from 0.19 to 0.52 g/gcat. middot h, although the CO and H2 conversions were slightly decreased. On the other hand, the BET, inductively coupled plasma/optical emission spectroscopy, and X-ray diffraction analysis found that the catalytic properties did vary after plasma pretreatment. In short, this paper reveals that the plasma pretreatment is a viable process for preparation of Cu/Zn/Al catalyst in terms of methanol synthesis.

Structural Investigation of MFe2O4 (M = Fe, Co) Magnetic Fluids

Ferrites of the type MIIFe2O4 (M = Fe and Co) have been prepared by the traditional coprecipitation method. These ferrites were modified by the adsorption of fatty acids derived from soybean and castor oil and were then dispersed in cyclohexane, providing very stable magnetic fluids, readily usable in nonpolar media. The structural properties of the ferrites and modified ferrites as well as the magnetic fluids were characterized by XRD (X-ray powder diffraction), TEM (transmission electron microscopy), DRIFTS (diffusion reflectance infrared Fourier transform spectroscopy), FTNIR (Fourier transform near-infrared), UV−vis, normal Raman spectroscopy, and surface-enhanced Raman scattering (SERS). XRD and TEM analysis have shown that the magnetic nanoparticles (nonmodified and modified) present diameters in the range of 10−15 nm. DRIFTS measurements have shown that the carboxylate groups of soybean and castor oil fatty acids adsorb on the ferrite surface, forming three different structures: a bridging bidentate, a bridging monodentate, and a bidentate chelate structure. The FTIR and Raman spectra of nonmodified Fe3O4 and CoFe2O4 nanoparticles have shown that the number of observed phonons is not compatible with the expected Oh7 symmetry, since IR-only active phonons were observed in the Raman spectra and vice versa. SERS measurements of a CoFe2O4 thin film on a SERS-active gold electrode at different applied potentials made possible the assignment of the signals near 550 and 630 cm−1 to Co−O motions and the signals near 470 and 680 cm−1 to Fe−O motions.

Synthesis of Layered Double Hydroxides with Novel Morphologies

Generally, the hexagonal plate morphology of Mg-Al layered double hydroxides (LDHs) is more favorable, in this article, we report the synthesis of Mg-Al LDHs with unique morphologies, such as ring-like, fiber-like, and sphere-like particles, respectively, using simple traditional coprecipitation method. This synthesis of MgAl-LDHs were carried out with sodium dodecylsulfate together with Na2-edta, Na2-edta, and sodium tartrate, respectively, as assistants to favor the precipitation process. The obtained products were characterized by transmission electron microscopy, x-ray diffraction, and FTIR spectroscopy. The studied results confirm that morphology of LDHs might be controlled by a soft-template effect of assistants in traditional coprecipitation method.

Superparamagnetic Iron Oxide Nanoparticles Coated with Mannan for Macrophage Targeting

To develop the functionalized superparamagnetic iron oxide nanoparticles (SPIONs) demonstrating the capacities to be delivered in antigen presenting cells specifically and to be dispersed in physiological environment stably, the nanoparticle surface was coated with mannan that induces receptor-mediated endocytosis. Mannan is a water-soluble polysaccharide having high content of D-mannose residues to be recognized by mannose receptors on immunate macrophages. Mannan-coated SPIONs (mannan-SPIONs) were prepared by traditional coprecipitation method, followed by a thermochemical treatment and post-coating with mannan solution. Poly(vinyl alcohol)-coated SPIONs (PVA-SPIONs) were also prepared as a control. Upon characterization, mannan-SPIONs were proven to be suitable for MR imaging due to small size, excellent stability in ferrofluid, and low cytotoxicity. In addition mannan-SPIONs exhibited enhanced targeted delivery efficiency to macrophages than PVA-SPIONs in vitro and in vivo. Therefore, mannan as a coating material not only prevented the aggregation of SPIONs in physiological medium but also provided a capacity to be delivered in antigen presenting cells specifically, suggesting of the potential utility of mannan-SPIONs as a macrophage-targeting MRI contrast agent.

Synthesis and morphology of Fe3O4/polystyrene/poly(isopropylacrylamide‐co‐methyl acrylate acid) magnetic composite latex – 2,2′‐azobis (2‐methylpropionamidine) dihydrochloride as initiator

AbstractIn this work, Fe3O4/polystyrene/poly(N‐isopropylacryl amide‐co‐methylacrylate acid) (Fe3O4/PS/P(NIPAAM‐co‐MAA)) magnetic composite latex was synthesized by the method of two stage emulsion polymerization. In this reaction system, 2,2′‐azobis(2‐methyl propionamidine) dihydrochloride (AIBA) was used as initiator to initiate the first stage reaction and second stage reaction. The Fe3O4 particles were prepared by a traditional coprecipitation method. Fe3O4 particles were surface treated by either PAA oligomer or lauric acid to form the stable ferrofluid. The first stage for the synthesis of magnetic composite latex was to synthesize PS in the presence of ferrofluid by soapless emulsion polymerization to form the Fe3O4/PS composite latex particles. Following the first stage of reaction, the second stage of polymerization was carried out by the method of soapless emulsion polymerization with NIPAAM and MAA as monomers and Fe3O4/PS latex as seeds. The magnetic composite particles, Fe3O4/PS/P(NIPAAM‐co‐MAA), were thus obtained. The mechanism of the first stage reaction and second stage reaction were investigated. Moreover, the effects of PAA and lauric acid on the reaction kinetics, morphology, and particle size distribution were studied. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3912–3921, 2007

Synthesis and morphology of an iron oxide/polystyrene/poly(isopropylacrylamide‐co‐methacrylic acid) thermosensitive magnetic composite latex with potassium persulfate as the initiator

AbstractIn this work, an iron oxide (Fe3O4)/polystyrene (PS)/poly(N‐isopropylacryl amide‐co‐methacrylic acid) [P(NIPAAM–MAA)] thermosensitive magnetic composite latex was synthesized by the method of two‐stage emulsion polymerization. The Fe3O4 particles were prepared by a traditional coprecipitation method and then surface‐treated with either a PAA oligomer or lauric acid to form a stable ferrofluid. The first stage for the synthesis of the thermosensitive magnetic composite latex was to synthesize PS in the presence of a ferrofluid by emulsion polymerization to form Fe3O4/PS composite latex particles. Following the first stage of reaction, the second stage of polymerization was carried out with N‐isopropylacryl amide and methacrylic acid as monomers and with Fe3O4/PS latex as seeds. The Fe3O4/PS/[P(NIPAAM–MAA)] thermosensitive magnetic particles were thus obtained. The effects of the ferrofluids on the reaction kinetics, morphology, and particle size of the latex were discussed. A reaction mechanism was proposed in accordance with the morphology observation of the latex particles. The thermosensitive property of the thermosensitive magnetic composite latex was also studied. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3062–3072, 2007

An intimate polycarbonate/poly(methyl methacrylate)/poly(vinyl acetate) ternary blend via coalescence from their common inclusion compound with γ‐cyclodextrin

AbstractIn this study, we successfully report an intimate ternary blend system of polycarbonate (PC)/poly(methyl methacrylate) (PMMA)/poly(vinyl acetate) (PVAc) obtained by the simultaneous coalescence of the three guest polymers from their common γ‐cyclodextrin (γ‐CD) inclusion compound (IC). The thermal transitions and the homogeneity of the coalesced ternary blend were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The observation of a single, common glass transition strongly suggests the presence of a homogeneous amorphous phase in the coalesced ternary polymer blend. This was further substantiated by solid‐state 13C NMR observation of the T1ρ(1H)s for each of the blend components. For comparison, ternary blends of PC/PMMA/PVAc were also prepared by traditional coprecipitation and solution casting methods. TGA data showed a thermal stability for the coalesced ternary blend that was improved over the coprecipitated blend, which was phase‐segregated. The presence of possible interactions between the three polymer components was investigated by infrared spectroscopy (FTIR). The analysis indicates that the ternary blend of these polymers achieved by coalescence from their common γ‐CD–IC results in a homogeneous polymer blend, possibly with improved properties, whereas coprecipitation and solution cast methods produced phase separated polymer blends. It was also found that control of the component polymer molar ratios plays a key role in the miscibility of their coalesced ternary blends. Coalescence of two or more normally immiscible polymers from their common CD–ICs appears to be a general method for obtaining well‐mixed, intimate blends. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4182–4194, 2004