Synthesis and characterization of manganese ferrite nanostructure by co-precipitation,sol-gel,and hydrothermal methods

ABSTRACT

In this research work, manganese ferrite nanoparticles (MnFe₂O₄) were synthesized by three different methods including the co-precipitation, sol-gel, and hydrothermal route. Structure, size, morphology, and magnetic properties of nanostructures were determined and compared using X-ray diffraction, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy analysis (FESEM), and the vibration sample magnetometer (VSM). X-ray diffraction analysis from Debye–Scherrer’s formula with the (2θ?=?35.08°) peak indicated that the mean size of the synthesized manganese ferrite nanocrystallites were obtained to be 36, 45, and 16?nm for co-precipitation, sol-gel, and hydrothermal, respectively. Also, the sample prepared by the hydrothermal method has the lowest crystal sizes, which it is approved by FESEM analysis. Field emission scanning electron microscopy analysis images confirmed the existence of three types of basic morphology of MnFe₂O₄ nanoparticles: spherical shape, multi-walled hollow nanosheets, and reticular structure. In addition, Based on VSM data magnetization saturation (M_s) was 41.89?emu/g for hydrothermal synthesized samples, 38.76?emu/g for co-precipitation samples, and 9.52?emu/g for sol-gel samples. These findings show that various methods of nanoparticle synthesis can lead to different particle sizes and magnetic properties.     

纳米CuAl2O4/CuO的制备及其模拟太阳光催化产氢

采用共沉淀法制备了纳米结构的CuAl2O4/CuO,用草酸作牺牲剂,在150W的氙灯照射下,考查了不同焙烧温度、催化剂用量对光催化活性的影响。并用XRD、SEM、TG-DTA对样品分别进行了分析与表征,表明CuAl2O4为尖晶石型结构,平均粒径10nm左右。在相同条件下分别考察了固相法、共沉淀法与柠檬酸溶胶-凝胶法对催化剂活性的影响,实验结果表明溶胶-凝胶法产氢活性最好,产氢速率为41mL/h;共沉淀法次之,为34mL/h;固相法最差,为25mL/h。     

Influence of preparation method on structural and magnetic properties of nickel ferrite nanoparticles

Nickel ferrite nanoparticles of very small size were prepared by sol-gel combustion and co-precipitation techniques. At the same annealing temperature sol-gel derived particles had bigger crystallite size. In both methods, crystallite size of the particles increased with annealing temperature. Sol-gel derived nickel ferrite particles were found to be of almost spherical shape and moderate particle size with a narrow size distribution; while co-precipitation derived particles had irregular shape and very small particle size with a wide size distribution. Nickel ferrite particles produced by sol-gel method exhibited more purity. Sol-gel synthesized nanoparticles were found to be of high saturation magnetization and hysteresis. Co-precipitation derived nickel ferrite particles, annealed at 400??C exhibited superparamagnetic nature with small saturation magnetization. Saturation magnetization increased with annealing temperature in both the methods. At the annealing temperature of 600??C, co-precipitation derived particles also became ferrimagnetic.     

Preparation of Sm-doped ceria (SDC) nanowires and tubes by gas–liquid co-precipitation at room temperature

Sm-doped cerium dioxide (SDC) with fcc structure was formed using a gas–liquid chemical co-precipitation process at room temperature. Morphology and structure of the as-prepared samples were characterized using TG, XRD, TEM, HRTEM and SAED techniques. Under our specific experimental conditions, two kinds of 1D nano-structures SDC have been mainly obtained. SDC nanowires are 0.3–1.2 μm in lengths and 5–20 nm in diameters. SDC nanotubes have outer diameters in 10–40 nm with lengths up to 2 μm. The as-prepared SDC shows very strong UV absorption ability and the maximum absorption peak redshifts compared with that of SDC nanoparticles.     

羧甲基壳聚糖/Ce^3＋掺杂TiO2复合抗菌材料的研究

采用溶胶-凝胶法制备稀土（Ce^3＋）掺杂纳米TiO2（纳米Ce/TiO2）,借助XRD、BET、SEM对Ce/TiO2进行表征。结果表明纳米Ce/TiO2晶型为锐钛矿,平均晶粒大小为19.95nm,比表面积为43.302m^2/g。采用超声波催化法合成了羧甲基壳聚糖（CMC）,并与Ce/TiO2复配制得羧甲基壳聚糖/Ce3＋掺杂纳米TiO2复合材料（CMC/Ce/TiO2）,借助FT-IR对CMC及CMC/Ce/TiO2复合材料进行了结构表征。初步研究了纳米Ce/TiO2、普通纳米TiO2、CMC/Ce/TiO2、CMC的抗菌性能,结果显示纳米Ce/TiO2对大肠杆菌和金黄色葡萄球菌的抗菌率分别为55%和53%,普通纳米TiO2对两种菌的抗菌率分别为50%和45%,Ce^3＋的掺杂可提高纳米TiO2的抗菌性能;CMC/Ce/TiO2对大肠杆菌和金黄色葡萄球菌的抗菌率分别达到99%和95%,CMC对两种菌的抗菌率分别为90%和80%,Ce/TiO2的复合可显著提高CMC的抗菌性能。     

In situ co-precipitation synthesis and photoluminescence of YxGd1−xVO4:Tm microcrystalline phosphors by hybrid precursors

Y_xGd_1−xVO₄:Tm³⁺ (5 mol%) phosphors were prepared by in situ co-precipitation technology with the different content ratio of Y/Gd (x = 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, respectively). During the process, rare earth coordination polymers with o-hydroxylbenzoate were used as precursors, composing with polyethylene glycol (PEG) as dispersing media. After heat-treatment of the resulting multicomponent hybrid precursors at 900 °C, the samples were obtained. SEM indicated the particles present good crystalline state, whose crystalline grain sizes were about 0.2–2 μm. Under the excitation of 257 nm, all the materials show the characteristic emission of Tm³⁺ which is the strong blue emission centered at 475 nm originating from ¹G₄ → ³H₆ of Tm³⁺. Besides this, concentration quenching appears in the system of YVO₄:Tm³⁺ and GdVO₄:Tm³⁺. And when x reaches 0.5, the system of Y_xGd_1−xVO₄:Tm³⁺ shows the strongest blue emission.     

Distinction between SnO2 nanoparticles synthesized using co-precipitation and solvothermal methods for the photovoltaic efficiency of dye-sensitized solar cells

Nanocrystalline SnO₂ powders prepared by solvothermal and co-precipitation pathways have been characterized using XRD, TEM, UV-Visible absorption, BET specific surface area (S _BET) method, EIS and J-V measurements. The obtained powders have a surface area and size of 38.59 m²/g and 10.63 nm for the SnO₂ powders synthesized solvothermally at a temperature of 200 °C for 24 h, while the values were 32.59 m²/g and 16.20 nm for the formed hydroxide precursor annealed at 1000 °C for 2 h by co-precipitation route. The microstructure of the formed powders appeared as tetragonal-like structure. Thus, the prepared SnO₂ nanopowders using two pathways were applied as an electrode in dye-sensitized solar cell (DSSC). The photoelectrochemical measurements indicated that the cell presents short-circuit photocurrent (J _sc), open circuit voltage (V _oc) and fill factor (FF) were 7.017 mA/cm², 0.690 V and 69.68%, respectively, for solvothermal route and they were 4.241 mA/cm², 0.756 V and 66.74%, respectively, for co-precipitation method. The energy conversion efficiency of the solvothermal SnO₂ powders was considerably higher than that formed by co-precipitation powders; ～ 3.20% (solvothermal) and 2.01% (co-precipitation) with the N719 dye under 100 mW/cm² of simulated sunlight, respectively. These results were in agreement with EIS study showing that the electrons were transferred rapidly to the surface of the solvothermal-modified SnO₂ nanoparticles, compared with that of a co-precipitation-modified SnO₂ nanoparticles.     

Nanocrystalline indium tin oxide fabricated via sol-gel combustion for electrochemical luminescence cells

Nanoporous indium tin oxide (ITO) was synthesized via a sol-gel combustion hybrid method using Ketjenblack as a fuel. The effects of the sol-gel combustion conditions on the structures and morphology of the ITO particles were studied. The size of the nanoporous powder was found to be 20-30 nm in diameter. The layer of the nanoporous ITO electrode (-10 microm thickness) with large surface area (-360 m2/g) was fabricated for an electrochemical luminescence (ECL) cell. At 4 V bias, the ECL efficiency of the cell consisting of the nanoporous ITO layer was approximately 1050 cd/m2, which is significantly higher than the cell using only the FTO electrode (450 cd/m2). The nanoporous ITO layer was effective in increasing the ECL intensities.     

Synthesis and physical characterization of magnetite nanoparticles for biomedical applications

Iron oxide nanoparticles for biomedical applications in the size range of 15–130 nm were prepared by either oxidative hydrolysis of ferrous sulfate with KOH or precipitation from ferrous/ferric chloride solutions. The magnetite particle size is controlled by variation of pH and temperature. The synthesized magnetite nanoparticles are partially oxidized as signaled by ferrous concentrations of below 24 wt% Fe²⁺ and lattice parameters of a₀ ≤ 8.39 Å which are smaller compared to 8.39 Å for stoichiometric magnetite. The extend of oxidation increases with decreasing particle size. Heating at 150–350 °C topotactically transforms the magnetite nanoparticles into stoichiometric tetragonal maghemite (ferrous ion concentration c_Fe²⁺=0 and a₀ = 8.34 Å) without significant particle growth. The magnetite–maghemite transformation is studied with thermal analysis, XRD and IR spectroscopy. The saturation magnetizations of the magnetite and maghemite particles decrease with decreasing particle size. The variation of M_s with particle size is interpreted using a magnetic core–shell particle model. Magnetite particles with d ≤ 16 nm show superparamagnetic behavior at room temperature whereas particles with diameter >16 nm display hysteresis behavior. These particles are candidates for biomedical applications, e.g. controlled drug release or hyperthermia.     

La2O3对ZnO-SiO2纳米复合物结构性能的影响

采用溶胶-凝胶法制备了ZnO-SiO2和ZnO-La2O3-SiO2复合物,通过TEM分析发现其均为纳米颗粒,平均粒径分别为45nm和35nm;通过比表面及孔径分布测定发现ZnO-SiO2的比表面积高达715.5m2/g,La2O3的加入使其比表面积骤减至142.5m2/g,平均孔径增大近4倍,孔容减小.此外,ZnO-SiO2的孔径分布较窄,从1.7nm到15nm,而ZnOLa2O3-SiO2的孔径分布变宽,从1.7nm到90nm,大多数孔集中在15.56nm左右.通过XRD和XPS分析发现ZnO、La2O3和SiO2之间存在着较强的相互作用.     

纳米介孔氧化铝的制备工艺及性能

分别采用碳黑和十六烷基三乙基溴化铵作为模板剂,硝酸铝为前驱体,用溶胶-凝胶法合成介孔氧化铝.通过N2吸附一脱附、TG-DSC等测试手段对样品进行了对比分析表征.考察了两种不同模板剂对其晶体结构、比表面及孔径大小的影响.实验结果表明,相对于十六烷基三甲基溴化铵或碳黑做模板剂,采用十六烷基三甲基溴化铵和碳黑组成的复合模板剂可以合成较大的比表面积、孔径和孔容(分别为370m2/g、6.5nm和1.54cm3/g)的介孔氧化铝,而且具有较窄的孔径分布.     

Synthesis and photoconductivity of nanosized phthalocyanine

Functional phthalocyanine （Pc） compounds of H2Pc, TiOPc, FePc and CIAIPc were synthesized with a yield of 46.7%, 91.2%, 37.4% and 34.0%, respectively. Nanosized TiOPc was synthesized via a one-step sol-gel method and effects of surfactant doses, nucleation temperature on TiOPc particle size and photoconductivity were investigated. When re（PEG）： m（TiOPc） was 0.1 and nucleation temperature was 0℃, the as-obtained TiOPc had the smallest particle size and largest specific surface area, which were 60 nm and 83m^2/g, respectively. TiOPc synthesized under these conditions also exhibits excellent photoconductivity with charging potential V0, dark decay speed Rd and energy for half-discharging of potential E1/2 being 1160 V, 30 V/s and 0.6 1x.s, respectively.     

Magnetic and photocatalytic properties of nanocrystalline ZnMn<Subscript>2</Subscript>O<Subscript>4</Subscript>

The present study describes the synthesis of ZnMn₂O₄ nanoparticles with the spinel structure. These oxide nanoparticles are obtained from the decomposition of metal oxalate precursors synthesized by (a) the reverse micellar and (b) the coprecipitation methods. Our studies reveal that the shape, size and morphology of precursors and oxides vary significantly with the method of synthesis. The oxalate precursors prepared from the reverse micellar synthesis method were in the form of rods (micron size), whereas the coprecipitation method led to spherical nanoparticles of size, 40–50 nm. Decomposition of oxalate precursors at low temperature (∼ 450°C) yielded phase pure ZnMn₂O₄ nanoparticles. The size of the nanoparticles of ZnMn₂O₄ obtained from reverse micellar method is relatively much smaller (20–30 nm) as compared to those made by the co-precipitation (40–50 nm) method. Magnetic studies of nanocrystalline ZnMn₂O₄ confirm antiferro-magnetic ordering in the broad range of ∼ 150 K. The photocatalytic activity of ZnMn₂O₄ nanoparticles was evaluated using photo-oxidation of methyl orange dye under UV illumination and compared with nanocrystalline TiO₂. Dedicated to Prof. C N R Rao on his 75th birthday     

还原氮化法制备多孔氮化钛粉体及其电化学性能

以乙醇为氧供体,四氯化钛为钛源,采用非水解溶胶-凝胶法制备多孔TiO2粉体,再经900℃氨气还原氮化合成多孔TiN粉体。利用XRD、SEM和BET表征粉体的物相、形貌及孔结构。结果表明,还原氮化产物为NaCl型立方TiN,颗粒呈球形团聚体,晶粒尺寸均匀,直径约30nm,同时具有平均孔径为22nm的介孔结构,孔容为0.18cm3/g,比表面积为34m2/g。循环伏安测试表明TiN粉体具有良好的功率特性,交流阻抗图谱显示其电阻较小,约为1.44Ω。恒流充放电测试表明TiN粉体的比电容达到81F/g,且能量密度随着功率密度增加而缓慢减小。由此可知,该多孔TiN粉体在超级电容器领域有应用潜力。     

Preparation of PbO nanoparticles by microwave irradiation and their application to Pb(II)-selective electrode based on cellulose acetate

Nanosized lead oxide particles were prepared by thermal decomposition of lead hydroxycarbonate synthesized under microwave irradiation. Urea and lead nitrate were used as the starting materials. Microstructure and morphology of the products were investigated by means of XRD, AFM, TEM, and IR absorption spectra. The results indicated that well crystallized, finely dispersed and spherical -PbO nanoparticles with a size of ca. 30 nm were obtained. Meanwhile, an orthogonal phase β-PbO with a size of ca. 38 nm was also obtained when the calcinations temperature was up to 600 °C. In addition, a Pb(II)-selective electrode based on cellulose acetate was prepared using nanosized -PbO powders synthesized. The electrode exhibited a Nernstian slope of 29±1 mV per decade in a linear range of 2.5×10⁻⁵ mol L⁻¹ to 1.0×10⁻¹ mol L⁻¹ for Pb²⁺ ion. The detection limit of this electrode is down to 8.0×10⁻⁶ mol L⁻¹. This sensor has a short response time of about 10 s and could be used in a pH range of 2.0–8.0. High selectivity was obtained over a wide variety of metal ions.     

无定形介孔SiO_2纳米粉体的仿生合成及表征(英文)

以酵母细胞为模板,采用共沉淀法制备了具有介孔结构的无定形SiO2纳米粉体。采用X射线衍射(XRD)测试出合成的材料为无定形结构,通过氮气吸附-脱附测试证明样品中含有介孔结构,并且样品的比表面积为443.18m2/g,BJH吸附平均孔径为6.24nm。样品的介孔结构也通过TEM得到证实。采用红光光谱测试分析了样品的化学键的键链情况。最后对其合成机理进行了分析,并画出了合成机理的简单模拟图。     

Charging kinetics in virgin and 1 MeV-electron irradiated yttria-stabilized zirconia in the 300–1000 K range

A study performed with a dedicated scanning electron microscope (SEM) on the surface electrical properties of (1 0 0)-oriented yttria-stabilized zirconia (YSZ) single crystals irradiated with 1 MeV electrons is presented. When compared with virgin YSZ, the 1 MeV-irradiated YSZ shows a decrease of the intrinsic total electron emission coefficient σ₀ and an increase of the time constant τ associated with the charging kinetics of the material at room temperature. These measurements performed with the SEM beam at 10 keV indicate that the defects induced by the 1 MeV-electron irradiation generate a positive electric field of the order of 0.5 × 10⁶ V/m at a depth of about 1 μm that prevents electrons to escape. When the SEM beam with a 1.1 keV energy is used, a smaller field (0.5 × 10³ V/m) is detected closer to the surface (20 nm). The fading of these fields during the thermal annealing in the 400–1000 K temperature range provides information on the nature of defects induced by the 1 MeV-electron irradiation.     

Magnetic/SiO2 nanocomposite thin films prepared by sol-gel dip coating modified method

Nanocomposite thin films of Spinel Iron-Oxide and SiO₂ have been prepared with sol-gel dip-coating technique involving the synthesis of a ferrofluid, which has been stabilized in absence of organic media and led to the formation of magnetic nanoparticles. Structural and morphological characteristics of the synthesized ferrofluid and the relevant derived nanocomposite films are reported, as determined from X-ray diffraction (XRD), Raman, Fourier-transform infrared, Mössbauer and Ultraviolet-visible experimental techniques. Scanning electron microscopy, atomic force and magnetic force microscopy results are also reported. The synthesized ferrofluid, composed of magnetic nanoparticles of an XRD estimated average size of 18 nm, exhibit Raman spectra characteristic of a maghemite phase. These ferromagnetic nanoparticles retained their nanostructure after being inserted into the as prepared films. After heat treatment under Ar atmosphere, the maghemite nanoparticles were transformed to non-stoichiometric magnetite, providing the final composite material with useful potential application characteristics. The calcined films reported here exhibit crack-free morphology, consisting of aggregated silica/magnetic nanoparticles, with a final average size of c.a. 100 nm, while the film roughness shows a maximum peak to peak of c.a. 10 nm.     

超声波辅助制备癸酸-棕榈酸@改性SiO2调温调湿复合材料超声波辅助制备癸酸-棕榈酸@改性SiO2调温调湿复合材料

以硅烷偶联剂改性SiO₂为壁材,癸酸（DA）-棕榈酸（PA）为芯材,利用超声波辅助溶胶-凝胶法制备DA-PA@改性SiO₂调温调湿复合材料,分析了硅烷偶联剂用量、超声波功率、超声波时间和超声波温度对DA-PA@改性SiO₂调温调湿复合材料粒径的影响,以及相关性能。结果表明,利用超声波辅助溶胶-凝胶法制备DA-PA@改性SiO₂调温调湿复合材料,可以显著降低粒径尺寸和减小粒径分布。当硅烷偶联剂用量为4.0 g、超声波功率为120 W、超声波时间为100 min和超声波温度为60℃时,DA-PA@改性SiO₂调温调湿复合材料的粒径较小且粒径分布较窄,即d₉₀=87.36 nm、d₅₀=63.34 nm、d₁₀=44.02 nm和d₉₀-d₁₀=43.34 nm,在相对湿度40.0%~65.0%范围内的平衡含湿量为0.1864~0.2379 g/g,相变温度为20.23~23.59℃,相变潜热为40.91~46.72 J/g,稳定性能良好。      

共沉淀法制备纳米YAG粉体

用共沉淀方法,采用共滴的方式,仔细控制反应过程中的ｐＨ值,获得具有包裹结构的共沉淀物,在９００℃煅烧后,可以获得纯ＹＡＧ相粉体．研究了初始溶液浓度及ｐＨ值对粉体性能的影响,所制备的ＹＡＧ粉体的比表面积随着初始溶液浓度的增加而减少,并随着滴定过程所控制的ｐＨ值的增加而迅速减少．通过优化工艺,可以获得颗粒大小为２０～３０ｎｍ,比表面达６８ｍ^２／ｇ的纯 ＹＡＧ粉体．