Preparation and properties of nanocrystal SmBO_3 by nitrate-citrate sol-gel combustion method

Nanocrystal SmBO3 powders were synthesized by nitrate-citrate sol-gel combustion method. The phase evolution, morphologies and absorbency of the synthesized powders were characterized by X-ray diffraction （XRD）, Field emission scanning electronic microscope （FESEM）, Fourier transform infrared spectroscopy （FFIR） and UV-3101PC spectrophotometer （UVPC）, respectively. XRD and FESEM results showed that pure SmBO3 phase was obtained at 750 ℃, with an average original particle size of about 100 nm. FTIR showed that there were apparently concentrated absorbent peaks between 500 and 1400 cm^-1. Moreover, the reflectivity of the powders apparently decreased at the wavelength between 1.05 and 1.15 μm. Therefore, SmBO3 might be a kind of absorbent material for infrared laser.

Preparation of YAG:Ce^(3+) phosphor by sol-gel low temperature combustion method and its luminescent properties

YAG:Ce3+ phosphor was prepared by sol-gel low-temperature combustion method. The effects of the precursor properties and calcining temperature on the crystallization process, microscopic morphology and luminescent properties of phosphor were studied. The results indicate that the pure phase of YAG can be obtained at 800 ℃ by sol-gel low temperature combustion method, using citric acid as complexing agent. When the molar ratio of metal ion to citric acid is 2.0 and pH value is 2, the crystallinity increases and the phosphor particle size grows up gradually with the increase of the calcining temperature. The powders were characterized through thermal analysis, X-ray diffraction analysis and scanning electron microscope analysis. The excitation spectra of YAG:Ce3+ phosphor take on a double peak structure, and the peak value of the main excitation spectra occurs at 460 nm and that of the emission spectra is near 530 nm. With the gradual increase of the calcining temperature, the peak position of excitation and emission spectra remains basically unchanged, but its relative intensity increases gradually.

Effect of Bi3+ Ion Substitution on Magnetic Properties of Cobalt Nano Ferrites Prepared by Sol-Gel Combustion Method

Bismuth substituted cobalt nano ferrites with the chemical composition Co Bix Fe2-x O4 (x = 0.00, 0.05, 0.10, 0.15, 0.20 & 0.25) were prepared by sol-gel combustion method. The phase identification of prepared samples is characterised by X-ray powder diffraction (XRD) method, which confirms the formation of a single phase fcc spinal structure. The mean crystallite sizes of all prepared samples were obtained within the range of 21 (±5) nm. Transmission Electron Microscopy (TEM) images also confirmed the crystallite size of all the synthesised samples was in nano range. With the effect of Bi3+ ion substitution on spinal cobalt ferrite, the magnetic properties were investigated by using Vibration Sample Magnetometer (VSM). The obtained hysteresis (M-H) curves of all the samples were analysed under the applied magnetic field of range ± 10 K Oe at 300 K. The magnetic properties such as saturation magnetisation (Ms), remnant magnetization (Mr) and coercivity (Hc) values are tabulated, which show a decrease in trend as the bismuth ion concentration increases. This is due to the addition of Bi3+ ion in the place of Fe3+ ion (octahedral site) and hence the Bi3+-Fe3+ ion interaction predominates as compared with the Fe2+-Fe3+ ion interaction. The data obtained from magnetic studies, the variation among the magnetic properties have been investigated for all the prepared samples.

Synthesis and Structural Properties of Bismuth Doped Cobalt Nanoferrites Prepared by Sol-Gel Combustion Method

A series of Bismuth doped Cobalt nanoferrites of chemical composition CoBixFe2-xO4 (where x = 0.00, 0.05, 0.10, 0.15, 0.20 & 0.25) were prepared by sol-gel combustion method and calcinated at 600℃. The structural and morphological studies were carried out by using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive Spectroscopy (EDS) and Fourier Transform Infrared (FT-IR) spectra showing the single phase spinal structure. The X-ray diffraction (XRD) analysis confirmed a single phase fcc crystal. The crystallite size of all the compositions was calculated using Debye-Scherrer equation and found in the range of 17 to 26 nm. The lattice parameters were found to be decreased as Bi3+ ion doping increases. The surface morphology was studied by Scanning Electron Microscope (SEM) and particle size was confirmed by Transmission Electron Microscopy (TEM). The EDS plots revealed existence of no extra peaks other than constituents of the taken up composition. The Fourier Transform Infrared (FT-IR) studies were made in the frequency range 350 - 900 cm-1 and observed two strong absorption peaks. The frequency band is found at 596 cm-1 where as the lower frequency band at 393 cm-1. It is clearly noticed that the two prominent absorption bands were slightly shifted towards higher frequency side with the increase of Bi3+ ion concentration.

Nanostructured Yb:GGG polycrystalline powders via gel combustion method

Gadolinium gallium gamet （GGG） nanopowders doped with ytterbium ions （Yb：GGG） were synthesized with citric acid as a fuel via gel combustion method. The optimized conditions for preparing yb^3＋：Gd3Ga5O12 nanopowders were discussed. The heat behavior, structure and morphology of powders were analyzed with thermal analysis （TG-DTA）, X-ray diffraction （XRD）, infrared spectra OR） and transmission electron microscope （TEM）. TG-DTA analysis revealed that the weight loss of the precursor occured below 800 ℃ and its crystallization temperature was 830.6℃. XRD and IR analysis showed that the precursor converted directly into pure GGG at a relatively lower temperature （900 ℃） without any other intermediate phase. The lattice constant was 1.2377 calculated by extrapolation method. TEM results indicated that the spherical powders showed good dispersity and had a relatively narrow size distribution with average particle size of approximately 40-50 ran, which was favorable for good sinterability of Yb：GGG laser ceramic.

Luminescence Characterization and Synthesis of γ-LiAlO_2:Eu^(3+) by Gel Combustion

γ-LiAlO2：Eu3＋（Eu3＋：LAO） phosphor was obtained by gel combustion method using LiNO3,Al（NO3）3·9H2O,Eu（NO3）3·6H2O and citric acid as raw materials.The structure,morphology and luminescence were characterized by means of X-ray diffraction （XRD）,scanning electron microscopy （SEM）,photoluminescence （PL）.The results demonstrated that the phosphor was pure-phase of flaky tetragonal crystal system with a mean size of around 1 μm.The strongest excitation peak was at 254 nm,belonging to the broadband excitation and the maximum emission peak was at 613 nm,corresponding to the 5D0→7F2 transition of Eu3＋.Luminous intensity is closely related to the calcination temperature and doping concentration of Eu3＋.

Synthesis and characterization of Sr_3Al_2O_6:Eu^(2+), Dy^(3+) phosphors prepared by sol-gel-combustion processing

A type of red luminescent Sr3Al2O6：Eu2＋, Dy3＋ phosphor powder is synthesised by sol-gel-combustion processing, with metal nitrates used as the source of metal ions and citric acid as a chelating agent of metal ions. By tracing the formation process of the sol-gel, it is found that it is necessary to reduce the amount of NO3 by dropping ethanol into the solution for forming a stable and homogeneous sol-gel. Thermogravimetric and Differential Scanning Calorimeter Analysis, x-ray diffractionmeter, scanning electron microscopy and photoluminescence spectroscopy are used to investigate the luminescent properties of the as-synthesised Sr3A1206：Eu2＋, Dy3＋. The results reveal that the Sr3Al2O6 crystallises completely when the combustion ash is sintered at 1250℃. The excitation and the emission spectra indicate that the excitation broadband lies mainly in a visible range and the phosphors emit a strong light at 618 nm under the excitation of 472 nm. The afterglow of （Sr0.94Eu0.03Dy0.03）3Al2O6 phosphors sintered at 1250℃ lasts for over 1000 s when the excited source is cut off.

Cu-Mn-CeO_(x) 催化剂制备及其对甲苯催化燃烧性能的探究

催化燃烧法因高效、节能和环境友好等特点被认为是最具发展潜力的VOCs治理方法之一。采用溶胶-凝胶法制备了多组铜锰铈复合金属氧化物催化剂,通过X射线衍射(XRD)、H_(2)-程序升温还原(H_(2)-TPR)、X射线光电子能谱技术(XPS)和BET比表面积等催化剂表征手段和催化燃烧性能评价实验,讨论了铜锰铈摩尔比对催化剂晶相结构、氧化活性、表面活性氧以及比表面积的影响。结果表明:调节铜锰铈摩尔比可影响催化剂原子掺杂状态诱导产生更多的氧空位从而提升其甲苯催化燃烧性能,当铜锰铈摩尔比为1∶1∶4时,催化剂表现出最佳催化燃烧效率(T_(90)=239.5℃)。

Preparation and Ionic Conductivity of Ultrafine Li_(2+x)RE_xSi_(1-x)O_3 by Sol-Gel Method

Li 2+ x RE x Si 1- x O 3(RE=Pr, Nd, Sm, Gd; x =0～0 15) samples were prepared by the sol gel method. DTA TG, XRD, TEM and A C impedance techniques were used to investigate the structure, shape, and ionic conductivity of these samples. The results show that the range of solid solution formation is in 0< x ≤0 09, in which the conductivity of these samples raises with the increasing amount of RE 2O 3 (RE=Pr, Nd, Sm, Gd) added, and the diameter of the powders is about 100 nm. Compared with the conventional solid state reaction, the sol gel method needs low temperature and presents high ionic conductivity.

sol-gel燃烧法合成MgFe2O4纳米颗粒及其气敏性

以Mg(NO3)2、Fe(NO3)3和柠檬酸为原料,采用sol-gel燃烧法,合成了MgFe2O4纳米颗粒。利用XRD、TEM和红外光谱对产物进行了结构、形貌的测量和表征。结果表明:MgFe2O4的前驱体燃烧后经过500℃下1h的热处理,得到平均粒径小于20nm的纳米颗粒。以MgFe2O4为原料,制备了气敏元件,发现元件在工作电压为4.5V时对50×10–6的Cl2的灵敏度达到177,响应时间达4s,而且对其它气体的抗干扰性很好,有望开发成为对Cl2检测的传感器材料。

NiCo铁氧体的sol-gel自蔓延法制备及电磁性能

为了提高NiCo铁氧体Ni1–xCoxFe2O4(x=0,0.1,0.3和0.5)的抗电磁干扰特性,采用柠檬酸sol-gel自蔓延法制备了纳米晶粒的NiCo铁氧体样品。利用XRD、VSM和矢量网络分析仪,测定了样品的晶体结构和磁性能及电磁性能。结果表明:在0.1～1.5GHz频段,Co含量x=0.1时样品的tanδ比x=0时提高了一倍以上。但Co含量的进一步增加却使样品的损耗特性变差,例如x=0.5时的tanδ仅为x=0时的40%,这与Co2+占位和晶粒度大小有密切关系。

Effects of ultrasonic impregnation combined with calcination in N_2 atmosphere on the property of Co_3O_4/CeO_2 composites for catalytic methane combustion

CoO/CeOcomposites with high surface areas and ultrafine crystalline sizes for catalytic combustion of methane were firstly prepared by a new sol-gel method which combined ultrasonic impregnation treatment and calcination in Natmosphere. The samples were characterized by various means such as nitrogen adsorption/desorption, X-ray diffraction(XRD), Htemperature-programmed reduction(H-TPR),X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM). Results showed that the modified catalyst had the mesoporous structure, comparatively higher amount of surface oxygen and larger oxygen vacancies than others. As a result of the structure and surface composition merits, a high methane combustion conversion(50%) could be obtained at a low temperature of 262 °C for the modified CoO/CeOcomposites catalysts. The experimental results demonstrated that ultrasonic impregnation treatment combined with the Nthermal treatment prior to calcination in air had a promising application for preparation of CoO/CeOcomposites catalysts for low-temperature catalytic combustion of methane.

Properties of red-emitting phosphors Sr_2MgSi_2O_7:Eu^(3+) prepared by gel-combustion method assisted by microwave

Novel red-emitting phosphors Sr2MgSi2O7：Eu3＋ were prepared by gel-combustion method assisted by microwave. The phase struc-ture and luminescent properties of as-synthesized phosphors were investigated by XRD and fluorescence spectrophotometer, respectively. The results showed that the as-synthesized sample was Sr2MgSi2O7 with tetragonal crystal structure. The excitation spectrum of Sr2MgSi2O7：Eu3＋ was composed of two major parts： one was the broad band between 200 and 350 nm, which belonged to the charge transfer of Eu3＋-O2-; the other consisted of a series of sharp lines between 350 and 450 nm, ascribed to the f-f transition of Eu3＋. The emission spec-trum consisted of two emission peaks at 593 and 616 nm, which was attributed to 5D0→7F1 and 5D0→7F2 of Eu3＋, respectively. The concen-tration of Eu3＋ （x） had great effect on the emission intensity of Sr2-xMgSi2O7：Eu3＋x. When x varied in the range of 0.04-0.18, the intensity of emission peaks at 593 and 616 nm increased gradually with the concentration of Eu3＋ increasing. It was interesting that no concentration quenching occurred. Moreover, the luminescent intensity could be greatly enhanced with incorporation of charge compensator Li＋ ions.

Magnetic properties of samarium and gadolinium co-doping Mn-Zn ferrites obtained by sol-gel auto-combustion method

Mn-Zn ferrites doped with different contents of Sm^（3＋） and Gd^（3＋） ions were prepared by sol-gel auto-combustion method and characterized by Fourier transform infrared spectroscopy（FTIR）, thermogravimetric analysis（TG）, X-ray diffraction（XRD）, scanning electron microscopy（SEM） and vibrating sample magnetometer（VSM）. When samples were calcined in a relatively low temperature below 1100 °C, secondary phases（α-Fe_2O_3） could be identified. Therefore, in order to acquire pure and better crystallinity, the suitable calcining temperature of powders was selected at 1200 °C. It was also found that all the samples consisting of ferrite phases of typical spinel cubic structure and average crystallite sizes between 31.5 and 38.2 nm were obtained after calcining at 1200 oC for 4 h. The lattice parameters increased almost linearly with increasing Sm content. A dense microstructure was obtained after sintering at 1250 °C for 4 h. Through the analysis of magnetic properties, hysteresis loops for all the samples were narrow with low values of coercivity and retentivity, indicating the paramagnetic nature of these samples. And saturation magnetization Ms strongly depended on the type of additive to reach a maximum of 47.99 emu/g for x=0.015, which showed a great promise for hyperthermia applications.

纳米粉体(CeO_2)_(0.9-x)(GdO_(1.5))_x(Sm_2O_3)_(0.1)的溶胶-凝胶低温燃烧合成

采用溶胶 -凝胶法与低温燃烧法相结合 ,合成了 (CeO2 ) 0 .9-x(GdO1 .5 ) x(Sm2 O3) 0 .1 系列粉体 .结果表明 :由硝酸盐与柠檬酸混合形成的凝胶 ,可在较低温度 (2 0 0～ 3 0 0℃ )点火并燃烧 ,其火焰温度达 90 0℃以上 .经TEM ,XRD测试 ,燃烧后即直接形成了粒径为 2 0～ 3 0nm ,具有萤石结构的单相粉体 ,由该粉体制备的固体电解质在中温下电导率为 5 .8× 10 - 2 S/cm ,组装的单个H2 -O2 燃料电池最大功率密度达 70mW

溶胶-凝胶燃烧法制备SmBO_3粉体的工艺条件及其光吸收性能

研究了溶胶-凝胶燃烧法制备SmBO3前驱体过程中的各种影响因素,考察了煅烧温度及煅烧时间对所合成的SmBO3粉体光吸收性能的影响.结果表明,当加热温度为80℃、H2O/(Sm+B)摩尔比为30、pH值为2、柠檬酸/(Sm+B)摩尔比为1:1时获得的凝胶在180℃下发生稳定的自燃烧反应,得到白色蓬松的前驱体.前驱体经750℃煅烧2h后得到的SmBO3粉体平均颗粒尺寸为100nm.在1.05～1.15μm波长范围,SmBO3粉体对光存在较强的吸收,在1.07μm波长附近反射率达最低值,约为0.41%,而在1.06μm波长处反射率约为0.6%.

新型稀土发光材料Sr_(3-x)MgSi_3O_(10)∶Tb_x^(3+)的合成及性质

采用凝胶-燃烧法,在活性炭弱还原气氛下合成了新型荧光粉Sr3-xMgSi3O10∶Tb3x+,通过热分析仪、红外光谱、X射线粉末衍射、X射线能量色散谱仪及荧光分光光度计等对产物的形成过程、结构、组成及发光性质进行了分析和表征。结果表明:干凝胶起火燃烧得前驱物,经900℃还原热处理即可得目标产物,其晶体结构与Sr2MgSi2O7相似,同属四方晶系。Sr3-xMgSi3O10∶Tb3x+的激发光谱为一位于200～300nm的宽带,主激发峰在249nm左右;发射光谱由491nm,544nm,586nm,624nm等一系列窄带发射峰组成,归属于Tb3+的5D4到7FJ(J=6,5,4,3)的跃迁。主发射峰位于544nm,对应于Tb3+的5D4→7F5的能级跃迁,导致一种黄绿光发射。研究发现:还原温度及Tb3+掺杂浓度对发光强度有着重要的影响,并对浓度猝灭机制进行了探讨。

超声波-溶胶-凝胶自蔓延法制备纳米氧化铝粉体

超声空化作用已经被证明是制备纳米粉体有效技术,可以防止团聚体生成。本文以柠檬酸为络合剂,在超声波中制得溶胶,用凝胶自蔓延法合成出了纳米Al2O3粉体。通过X射线衍射仪(XRD)、扫描电镜(SEM)和透射电镜(TEM)分析,探讨了不同比例金属离子与柠檬酸对纳米粉体的形成和粉末晶粒尺寸大小的影响。研究结果表明,超声空化可以减少团聚,金属离子与柠檬酸比例为0.6∶1干凝胶在600℃燃烧,保温60 min,可以得到团聚少、颗粒尺寸为20～30 nm的纳米Al2O3粉体。

溶胶-凝胶燃烧法制备Nd:Y_2O_3激光陶瓷纳米粉体

以Y2O3和Nd2O3为原料,采用溶胶-凝胶燃烧法制备出Nd:Y2O3激光陶瓷纳米粉体。XRD测试结果表明粉体的最佳煅烧温度为1000℃,并且晶化完全。原子力显微镜观察结果表明粉体的粒度约为200nm,分布均匀。差热-热重分析表明,柠檬酸在447℃分解放热,而晶型转变温度为590℃,荧光光谱测试表明粉体最强的荧光发射峰位于9421.646cm-1(即波长1061.4nm处),是Nd3+4F3/2-4I11/2谱相导致的荧光发射。

两种络合剂对Ce-Sn-O复合氧化物结构与性能的影响

分别以柠檬酸、葡萄糖为络合剂,用溶胶-凝胶法制备了CeO_2和掺杂少量Sn的Ce-Sn-O复合氧化物,利用XRD、TPR、FT-IR、比表面法、TEM等方法表征了四种催化剂的物理化学性质,同时以甲烷催化燃烧反应为探针对其进行了活性评价.结果表明,以葡萄糖为络合剂合成的掺杂锡后的样品其甲烷完全转化温度较低,比表面积较大,通过透射电子显微镜观察,平均晶粒大小为14nm左右,且分散性良好,而相比之下柠檬酸为络合剂合成的样品出现明显的团聚现象.