Modified Polyacrylamide Gel Route Research Articles

Synthesis of SrFe12O19 magnetic nanoparticles by EDTA complex method

A modified polyacrylamide gel route was used to prepare SrFe12O19 magnetic nanoparticles; ethylenediaminetetraacetic acid (EDTA) was used as a carboxyl chelating agent. The phase purity, morphology and magnetic properties of as-prepared samples were analyzed via X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometery (VSM). XRD analysis indicates that high-purity SrFe12O19 magnetic nanoparticles can be synthesized at 700°C in air. The characteristic peaks of as-prepared sample at 210, 283, 321, 340, 381, 411, 432, 475, 532, 618, 686, and 726 cm–1 were observed in Raman spectra. SEM and TEM show that the synthesized SrFe12O19 magnetic nanoparticles are uniform with the mean particle size of ~60 nm. VSM measurement shows that the maximum magnetic energy product (BH)max of sample prepared using EDTA as a chelating agent is higher than that of sample prepared using citric acid as a chelating agent.

Influence of different aluminum salts on the photocatalytic properties of Al doped TiO2 nanoparticles towards the degradation of AO7 dye

Three kinds of Al-TiO2 samples and pure TiO2 samples were synthesized via a modified polyacrylamide gel route using different aluminum salts, including Al2(SO4)3∙18H2O, AlCl3, and Al(NO3)3∙9H2O under identical conditions. The influence of different aluminum salts on the phase purity, morphologies, thermal stability of anatase and photocatalytic properties of the as-prepared Al-TiO2 nanoparticles were studied. The energy gap (Eg) of Al-TiO2 nanoparticles decreases due to Al ion doping into TiO2. The photocatalytic activities of the Al-TiO2 samples were investigated by the degradation of acid orange 7 dye in aqueous solution under simulated solar irradiation. The Al-TiO2 nanoparticles prepared from Al(NO3)3∙9H2O exhibit the best photocatalytic activity among the four kinds of samples, followed in turn by the Al-TiO2 nanoparticles prepared with AlCl3, Al2(SO4)3∙18H2O and pure TiO2. The different performances are attributed to complex effects of Eg, particle size, surface morphology, phase purity and the defect sites of the Al-TiO2 nanoparticles.

High-temperature phase transition, coordination mechanism and magnetism in multiferroic YMnO3 nanopowders

Single phase YMnO3 nanopowders were successfully synthesized by a modified polyacrylamide gel route at an optimal sintering temperature. High temperature is helpful for further crystallization and the formation of single hexagonal YMnO3. The process was monitored by X-ray diffraction as well as by X-ray photoelectron spectroscopy, transmission electron microscope, Fourier transform infrared spectrum and magnetic measurements. A mixture of orthorhombic and hexagonal phases was found to exist in the 800 °C, while for the metastable orthorhombic YMnO3 phase complete conversion to hexagonal phase occurs at 950 °C. In the synthesis process, the coordination mechanisms of EDTA anions and metal ions (Y3+ and Mn3+) have been discussed on the basis of the experimental and computational results. The synthesis route used in this case has been aggreed to be more convenient for obtaining single hexagonal YMnO3 phase than by the combination of hydrothermal synthesisand additional thermal treatment or the glycine–nitrate process. The magnetic susceptibility indicates that the anti-ferromagnetic transition temperature increases from 58 to 71 K with increasing sintering temperature from 800 to 950 °C.

Phase-controlled synthesis, surface morphology, and photocatalytic activity of the perovskite AlFeO3

Perovskite-type AlFeO3 powders are synthesized by a modified polyacrylamide gel route using different chelating agents at different pHs. X-ray diffraction and Raman results indicate that the AlFeO3 powders synthesized with oxalic acid are rhombohedral structure, while the AlFeO3 powders fabricated by using the other chelating agents exhibit an orthorhombic structure. The scanning electron microscopic images indicate that the morphology of the AlFeO3 samples depend on the choice of chelating agent and pH value. In addition, the particle size of samples with rhombohedral structure is larger than that of the samples with orthorhombic structure. X-ray photoelectron spectroscopy and scanning electron microscopic analysis indicate that the AlFeO3 powders fabricated at pH = 7 have good phase purity and uniform size. Photocatalytic activities of the AlFeO3 samples are determined by the degradation of rhodamine B dye in the presence of hydrogen peroxide and the results show that the samples will probably be applicable in the development of highly efficient photocatalyst. In addition, the rhombohedral AlFeO3 samples exhibit better photocatalysis than the orthorhombic samples, which is probably because that the crystal structure of AlFeO3 samples play a more important role than particle size in photocatalytic activity. The as-prepared AlFeO3 photocatalyst exhibits a pronounced photocatalytic activity for the decomposition of rhodamine B under visible-light irradiation, which is expected to widen the potential applications for perovskite-type oxide AlFeO3. A novel perovskite-type photocatalyst AlFeO3 is synthesized by a modified polyacrylamide gel route using different chelating agents. The crystal structure of AlFeO3 sample depend on the choice of chelating agent and AlFeO3 photocatalyst, in the presence of hydrogen peroxide, exhibit a pronounced photocatalytic activity for the decomposition of rhodamine B under simulated sunlight.

Highly dispersed spinel (Mg, Ca, Ba)-ferrite nanoparticles: Tuning the particle size and magnetic properties through a modified polyacrylamide gel route

Highly dispersed ferrite magnetic nanoparticles (MFe2O4, where M=Mg, Ca, Ba) were synthesized through a modified polyacrylamide gel route based on the use of carbon particles. By manipulating the sintering temperature and carbon concentration, the formation of (Mg, Ca, Ba)-ferrite phase can be suppressed to produce the intermediate phases of MCO3 (M=Mg, Ca, Ba) and Fe2O3. The novel MFe2O4 magnetic nanoparticles exhibited high crystallinity and hysteresis loop squareness ratio. Furthermore, the MFe2O4 magnetic nanoparticles exhibited improved surface morphology when compared with nano-MFe2O4 of similar particle size synthesized by the polyacrylamide gel route reported in the literature. Morphology and magnetic properties of MFe2O4 magnetic nanoparticles change also appears to be strongly dependent on the divalent metal M. These results bring up new ideas for the design of highly dispersed ferrite magnetic nanoparticles with tuned magnetic properties through a versatile polyacrylamide gel route.

Insight into the effects of titanium salt and sintering temperature on the luminescence of Ti: α-Al2O3 phosphor

A modified polyacrylamide gel route is used to synthesize the alumina-based light-emitting material Ti: α-Al2O3. Sintering temperature and titanium metal salt can significantly effects the formation of rhombohedral α-Al2O3 phase. The titanium metal salt introduction influenced the sample morphology, band-gap and luminescence properties. The photoluminescence spectra show that the Ti: α-Al2O3 sample have three strong bands at 380, 430 and 520nm. The luminescence mechanisms of Ti: α-Al2O3 sample have been discussed on the basis of the experimental results. The Ti: α-Al2O3 composites making them promising candidates as efficient blue-green light-emitting materials.

Coordination mechanism, characterization, and photoluminescence properties of spinel ZnAl2O4 nanoparticles prepared by a modified polyacrylamide gel route

Single-phase ZnAl2O4 nanoparticles with the spinel structure were successfully synthesized using a modified polyacrylamide gel method according to the atomic ratio of Zn to Al = 1: 1.8. The as-prepared samples were characterized by means of X-ray powder diffraction (XRD), thermogravimetric analysis (TG), differential scanning calorimetry analysis (DSC), field-emission scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL) spectra. XRD patterns show that the pure phase of ZnAl2O4 is obtained after heating the xerogel at 900°C for 5 h in air. The SEM images reveal that the ZnAl2O4 nanoparticles have a narrow particle size distribution and the average particle size is around 45 nm. Photoluminescence (PL) spectra demonstrate the single phase ZnAl2O4 nanoparticles have an emission peak located at 469 nm when excited by 350 nm light. The phase structure, coordination mechanism, and luminescence properties have been discussed on the basis of the experimental results.

A New Method for Synthesis of FeMnO<sub>3</sub> Ceramics and its Phase Transformation

FeMnO3 powders were synthesized through a modified polyacrylamide gel route. The gel and the heat treated final powders have been characterized by X-ray diffractometry (XRD), differential scanning calorimetry and thermogravimetric analysis (TG/DSC) and field-emission scanning electron microscopy (SEM). Phase transformation sequence of dry gel during heating is (Mn+3,Fe+3)2O3→(α-Mn2O3)·(α-Fe2O3)→FeMnO3. The thermal expansion properties of as-prepared sample were determined. From 100 to 700 °C, the average coefficient of expansion is 9.0139×10-6 /K. The experimental results demonstrates that the FeMnO3 sample exhibit a ferromagnetic transitions with TN ≈ 40 K.

Effect of carbon and sintering temperature on the structural and magnetic properties of SrFe12O19 nanoparticles

SrFe12O19 magnetic nanoparticles with hexagonal magnetoplumbite structure were synthesized by a modified polyacrylamide gel route and characterized by X-ray diffraction, scanning electron microscope, Fourier transform infrared spectrophotometer, and vibrating sample magnetometer. To obtain large squareness ratio of SrFe12O19, a certain amount of carbon particles were introduced to the precursor solution. X-ray diffraction patterns showed that the carbon and sintering temperature accelerated hexagonal SrFe12O19 phase formation and not changed the hexagonal magnetoplumbite structure. The phase transformation process is closely correlated not only to the sintering temperature but also to the addition carbon particles. In the Fourier transform infrared spectra of SrFe12O19 sample, three obvious absorption peaks at 600, 550 and 439 cm−1 were observed. The carbon introducing to SrFe12O19 precursor solution improved the surface morphology and enhanced the squareness ratio value. The coercivity and squareness ratio of the hexagonal SrFe12O19 are closely correlated not only to the crystallite size but also to the dispersion of nanoparticles of SrFe12O19 sample.

Optimization of the electrochemical performance of a Ni/Ce0.9Gd0.1O2−δ-impregnated La0.57Sr0.15TiO3 anode in hydrogen

A-site deficient perovskite La0.57Sr0.15TiO3 (LSTO) materials are synthesized by a modified polyacrylamide gel route. X-ray diffraction pattern of LSTO indicates an orthorhombic structure. The thermal expansion coefficient of LSTO is 10.0 × 10−6 K−1 at 600 °C in 5%H2/Ar. LSTO shows an electrical conductivity of 2 S cm−1 at 600 °C in 3%H2O/H2. A new composite material, containing the porous LSTO backbone impregnated with small amounts of Ce0.9Gd0.1O2−δ (CGO) (3.4–8.3 wt.%) and Ni/Cu (2.0–6.3 wt.%), is investigated as an alternative anode for solid oxide fuel cells (SOFCs). Because of the substantial electro-catalytic activity of the fine and well-dispersed Ni particles on the surface of the ceramic framework, the polarization resistance of 6.3%Ni-8.3%CGO-LSTO anode reaches 0.73 Ω cm2 at 800 °C in 3%H2O/H2. In order to further improve the anodic performance, corn starch and carbon black are used as pore-formers to optimize the microstructure of anodes.

Influence of Fe<sub>2</sub>O<sub>3</sub> on Structural and Magnetic Properties of LaFeO<sub>3</sub>/Fe<sub>2</sub>O<sub>3</sub> and Mn<sub>2</sub>O<sub>3</sub>/Fe<sub>2</sub>O<sub>3</sub> Magnetic Nano-Composites

LaFeO3/Fe2O3 and Mn2O3/Fe2O3 magnetic nanocomposites have been prepared by a modified polyacrylamide gel route. The XRD result indicates the formation of LaFeO3/Fe2O3 and Mn2O3/Fe2O3 nanocomposites. Scanning electron microscope (SEM) observation shows that the LaFeO3/Fe2O3 particles appear to be regularly spherical in shape and highly uniform in size with a diameter of ~ 80 nm, while the Mn2O3/Fe2O3 sample exhibits a relatively broad particle size distribution with an average particle size centered around 20-60 nm. Result of vibrating sample magnetometer (VSM) of LaFeO3/Fe2O3 magnetic nanocomposites revealed that coercivity values decreased with the increase sintering temperature. However, the coercivity values of Mn2O3/Fe2O3 magnetic nanocomposites appear to an anomaly phenomenon.

Fabrication of a novel light emission material AlFeO3 by a modified polyacrylamide gel route and characterization of the material

AlFeO3 powders have been prepared by a modified polyacrylamide gel method and their thermal expansion and photoluminescence properties have been studied for the first time. The phase, morphology and thermal expansion behavior of as-prepared samples were analyzed via X-ray diffraction (XRD), Scanning electron microscope (SEM), and thermal dilatometer. XRD analysis indicates that the as-synthesized AlFeO3 has the same structure as α-Fe2O3 without the presence of any other impurities. SEM observation shows that the morphology of AlFeO3 powder is significantly dependent on the sintering temperature. The thermal expansion and differential scanning calorimetry (DSC) curves of AlFeO3 sample analysis indicates that a phase transition near 700°C. The crystal growth mechanisms, coordination mechanisms, phase transformation process and luminescence mechanisms of AlFeO3 have been discussed on the basis of the experimental results. The blue light emission at 2.76eV is due to intracenter 4T1→6A1 transitions in Fe3+ ions.

Chelating agents role on phase formation and surface morphology of single orthorhombic YMn2O5 nanorods via modified polyacrylamide gel route

YMn2O5 nanorods were synthesized through a modified polyacrylamide gel route. The synthesis strategy in this work is based on a sol-gel process using a polyacrylamide gel method in which oxalic acid, citric acid or tartaric acid is employed as the chelating agent. In the gel routes, oxalic acid was used as a carboxyl chelating agent, while citric acid or tartaric acid was a carboxyl and hydroxyl chelating agent. The as-prepared samples were characterized by means of techniques such as X-ray powder diffraction (XRD) measurement, thermogravimetric analysis (TG), differential scanning calorimetry analysis (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermal expansion measurement and field-emission scanning electron microscopy (SEM) investigations. It was found that oxalic acid is the best chelating agent with Y(NO3)3·6H2O and Mn(CH3COO)2·4H2O as precursors to prepare a single orthorhombic YMn2O5 nanorods at 1000°C. Scanning electron microscope observation shows that the morphology of YMn2O5 powders is significantly dependent on the chelating agent. The peaks (single orthorhombic YMn2O5 nanorods) at 642, 600, 573, 546, 521, 493, 486, 468, 448 and 400 cm−1 were observed from FTIR spectra. The phase, surface morphology and chelation mechanisms of YMn2O5 samples have been discussed on the basis of the experimental results.

Role of chelating agent in chemical and fluorescent properties of SnO2 nanoparticles

A modified Polyacrylamide gel route is applied to synthesize SnO2 nanoparticles. High-quality SnO2 nanoparticles with a uniform size are prepared using different chelating agents. The average particle size of the samples is found to depend on the choice of the chelating agent. The photoluminescence spectrum detected at λex = 230 nm shows a new peak located at 740 nm due to the surface defect level distributed at the nanoparticle boundaries.

Role of pH, Organic Additive, and Chelating Agent in Gel Synthesis and Fluorescent Properties of Porous Monolithic Alumina

This work demonstrates the synthesis of porous monolithic α-alumina by a modified polyacrylamide gel route at different reaction parameters. Various Al2O3 phases are synthesized by a modified polyacrylamide gel route using different organic additives and solutions with different pH values (3, 7, and 11). After calcination at 1150 °C, the pure α-Al2O3 is obtained at pH = 3 and 7 while there is still θ-Al2O3 at pH = 11. The organic additive has nothing to do with the purity of α-Al2O3phase. The scanning electron microscopic images indicate that the pore size and morphology of the samples depend on the choice of organic additive and pH value. The photoluminescence spectra show that two emission peaks located at 330 and 368 nm are observed when the excitation wavelength is 228 nm. Interestingly, the intensity of emission peak at 368 nm decreases with the decrease of full width at half-maximum or pore size.

Size-controlled synthesis and photoluminescence of porous monolithic α-alumina

A modified polyacrylamide gel route is used to synthesize porous monolithic α-alumina. X-ray powder diffraction analysis indicates that the as-prepared samples are rhombohedral α-alumina phase, suggesting that high-purity α-alumina can be prepared by using different chelating agents and sintering at about 1150°C. The scanning electron microscopic images show that the macropore size of the α-alumina samples is related to the chelating agent. The photoluminescence spectra show that a major emission band around 365nm and a weaker side band located at 330nm are observed when the excitation wavelength is 228nm. Interestingly, the intensity of emission peak at 365nm decreases with the decreasing pore size. The pore-forming and luminescence mechanisms of porous alumina have been discussed based on the experimental results.