Effect of Al-substitution on phase formation and magnetic properties of barium hexaferrite synthesized with sol-gel auto-combustion method

Al-substituted barium ferrite powders were synthesized using the sol-gel auto-combustion method according to the molecular formula BaAlxFe12-xO19 （x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0）. Compared with non-substituted barium ferrite annealing at 1000 ℃, the vibrating sample magnetometer （VSM） measurement manifested that the optimum magnetic properties formation temperature of Al-substituted barium ferrite was 1 100 ℃. The data from X-ray diffractometer （XRD） showed that with increasing x, the lattice constants （a and c） decreased as well as the unit-cell volume Vcell. Magnetic measurement of non-substituted and Al-substituted powders annealed from 900 ℃ to 1 200 ℃ exhibited that the maximum magnetization M （10 kOe）, the remanent magnetization Mr and the coercivity Hc depended strongly on the chemical composition of powder as well as the annealing temperature. When annealing at 1 100 ℃, BaAl0.5Fe11.5O19 of high coercivity Hc （6584 Oe） was produced. Meanwhile, M （10 kOe） and Mr were 42.83 emu/g and 25.65 emu/g, respectively.

Synthesis and Luminescent Properties of Superfine Sr_2CeO_4 Phosphors by Sol-Gel Auto-Combustion Method

Citric acid complexing sol-gel auto-combustion method was explored to synthesize superfine Sr2CeO4 phosphors using the inorganic salts Sr（NO3）2 and Ce（NO3）3 as raw materials together with citric acid （CA） as a chelating agent. TGDTA, XRD, SEM and photoluminescence spectra were used to investigate the formation process, microstructure and luminescent properties of the synthesized Sr2CeO4. The results show that the crystallization of Sr2CeO4 begins at about 800 ℃ and completes around 900 ℃ with an orthorhombic structure. When the calcination temperature is above 1000 ℃, Sr2CeO4 partly decomposes into SrCeO3. SEM studies show that the particles of Sr2CeO4 obtained at 900 ℃ are sphericallike shape and superfine with diameter below 100 nm. The excitation spectrum of the superfine Sr2CeO4 phosphors displays a broad band with two peaks around 290 and 350 nm respectively. The former peak is stronger than the latter one. This broad band is due to the charge transfer （CT） band of the Ce^4＋ ion. Excited by a radiation of 290 nm, the superfine phosphors emit a strong blue-white fluorescence, and the emission spectrum shows a broad band with a peak around 470 nm, which can be assigned to the f→t1g transition of Ce^4＋ . It is found that the emission intensity is affected by the calcination temperature.

Influence of citric acid content on magnetic properties of BaFe12O19 powder prepared by sol-gel auto-combustion method

BaFe12O19 powders with nanocrystaUine sizes were produced by sol-gel auto-combustion method. The precursors were prepared under the molar ratios of citric acid to the metal nitrate of 0.5, 1.0 and 1.5. Appropriate ethylene diamine （C2H8N2） was added in order to adjust pH of 7. The ions distribution of citric acid at different pH explains the effect of citric acid in the starting solution. The XRD patterns of the as-burnt powders and annealing powders show different phases for different citric acid content. In addition, the lattice constants （a, c） derived from X-ray diffraction pattern were changed from 0.58881 nm to 0.58997 nm and 2.32057 nm to 2.32296 nm respectively. The data from VSM indicated that the powder with high citric acid content took on good magnetic properties. Pure single BaFe12O19 of the specific maximum magnetization M（1 T）≈ 49.73 Am^2/kg, the specific remanent magnetization Mr ≈ 30.77 Am^2/kg and the coercive force He≈ 467 kA/m was produced when the molar ratios of citric acid to the metal nitrate was 1.5.

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.

Development of Modified Glasses by Transparent, Functional Hybrid Sol-Gel Nano-Ceramic Coatings, a Comparative Study

This paper concentrates on the development of glasses with self-cleaning surfaces exhibiting high water contact angles. In this study, we prepared super-hydrophobic nano-ceramic coated glass based on titania & silica using simple sol-gel & dip coating methods and studied the best composition of the coatings by altering ratios of titanium tetraisopropoxide (TTIP)/tetraethyl orthosilicate (TEOS) with different homogenizing agents. We characterized the coatings by surface roughness measurement, percentage of optical transmission, static contact angle, near-infrared (NIR) transmission, and diffuse reflectance. The fabrication of coatings on glass substrates played an important role in increasing the water contact angle of about 95° and visible & NIR transmission of about 90%. We compared our modified glass substrate with commercial low emissivity (Low E) glass using X-ray diffraction (XRD) analysis, which showed pure amorphous surface claiming excellent wettability and thus the prepared glass substrate could have a variety of applications in different fields.

Sol-gel-based porous Ti-doped tungsten oxide films for high-performance dual-band electrochromic smart windows

Dual-band electrochromic smart windows(DESWs)with independent control of the transmittance of near-infrared and visible light show great potential in the application of smart and energy-saving buildings.The current strategy for building DESWs is to screen materials for composite or prepare plasmonic nanocrystal films.These rigorous preparation processes seriously limit the further development of DESWs.Herein,we report a facile and effective sol-gel strategy using a foaming agent to achieve porous Ti-doped tungsten oxide film for the high performance of DESWs.The introduction of foaming agent polyvinylpyrrolidone during the film preparation can increase the specific surface area and free carrier concentration of the films and enhance their independent regulation ability of near-infrared electrochromism.As a result,the optimal film shows excellent dual-band electrochromic properties,including high optical modulation(84.9%at 633 nm and 90.3%at 1200 nm),high coloration efficiency(114.9 cm^(2) C^(-1) at 633 nm and 420.3 cm^(2) C^(-1) at 1200 nm),quick switching time,excellent bistability,and good cycle stability(the transmittance modulation losses at 633 and 1200 nm were 11%and 3.5%respectively after 1000 cycles).A demonstrated DESW fabricated by the sol-gel film showed effective management of heat and light of sunlight.This study represents a significant advance in the preparation of dual-band electrochromic films,which will shed new light on advancing electrochromic technology for future energy-saving smart buildings.

Investigation of UV photosensor properties of Al-doped SnO_(2) thin films deposited by sol-gel dip-coating method

Transparent conducting aluminum doped tin oxide thin films were prepared by sol-gel dip coating method with differ-ent Al concentrations and characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), UV-Vis spectrophotometry and photoconductivity study. The variation observed in the properties of the measured films agrees with a difference in the film's thickness, which decreases when Al concentration augments. X-ray diffraction analysis reveals that all films are polycrystal-line with tetragonal structure, (110) plane being the strongest diffraction peak. The crystallite size calculated by the Debye Scher-rer’s formula decreases from 11.92 to 8.54 nm when Al concentration increases from 0 to 5 wt.%. AFM images showed grains uni-formly distributed in the deposited films. An average transmittance greater than 80% was measured for the films and an en-ergy gap value of about 3.9 eV was deduced from the optical analysis. Finally, the photosensitivity properties like current-voltage characteristics, ION/IOFF ratio, growth and decay time are studied and reported. Also, we have calculated the trap depth energy using the decay portion of the rise and decay curve photocurrent.

Structural evolution-enabled BiFeO3 modulated by strontium doping with enhanced dielectric,optical and superparamagnetic properties by a modified sol-gel method

Multiferroic(BFO)nanoparticles doped with strontium with the general formula Bi1-xSrx FeO3(x=0,0.3,0.5,0.7)were synthesized using a modified sol-gel auto-combustion process.The structural,electrical,optical,and magnetic properties of the samples are discussed.The structural analysis,carried out using the x-ray powder diffraction technique,shows a structural transition from rhombohedral(R-3c)to cubic(Pm-3m)for the doping amount of strontium(Sr)equal to x=0.3.Morphological analysis of the prepared samples were carried out using scanning electron microscopy(SEM).Frequency-dependent dielectric constant and ac conductivity were studied.The doped samples,with improved dielectric properties,can be used to fabricate different optoelectronic devices.Strong dielectric dispersion and broad relaxation were exhibited by all the samples.Cole–Cole plots were employed as an effective tool to study the dispersion parameters,namely,the optical dielectric constant,static dielectric constant,relaxation time,and spreading factor.The activation energy was calculated from the relaxation peaks and Cole–Cole plots,which were found to be compatible with each other.The bandgap of the samples was calculated using diffuse reflectance spectral(DRS)analysis.Sharp and strong photoluminescence in the IR region was observed in the samples,similar to ZnO,which was reported for the first time.Room-temperature and low-temperature magnetization studies point towards the superparamagnetic nature of the samples,with an improvement in magnetic properties with doping.The antiferromagnetic behavior of bulk bismuth ferrite transforms to superparamagnetic in nature for both pure and Sr-substituted bismuth ferrite nanoparticles due to the close dimensions of crystallite size with magnetic domains leading to the break-down of the frustrated spin cycloidal moment.

Application of g-C_(3)N_(4)/sol-gel nanocomposite on AM60B magnesium alloy and investigation of its properties

To protect the AM60B magnesium alloy from corrosion,a sol-gel coating containing hydroxylated g-C_(3)N_(4)nanoplates was applied.The chemical composition of the hydroxylated g-C_(3)N_(4)nanoplates was investigated using X-ray photoelectron spectroscopy(XPS).The hydroxylation process did not affect the crystal size,specific surface area,pore volume,average pore diameter,and thermal stability of the g-C_(3)N_(4)nanoplates.After incorporating pristine and hydroxylated g-C_(3)N_(4)nanoplates,dense sol-gel coatings were obtained.Transmission electron microscopy(TEM)revealed the uniform distribution of the modified g-C_(3)N_(4)in the coating.The average roughness of the coating was also reduced after adding the modified nanoplates due to the decreased aggregation tendency.Electrochemical impedance spectroscopy(EIS)examinations in simulated acid rain revealed a significant improvement in the anticorrosion properties of the sol-gel film after the addition of the modified g-C_(3)N_(4)due to the chemical bonding of the coating to the nanoplates.

Comparative structural and electrochemical properties of mixed P2/O′3-layered sodium nickel manganese oxide prepared by sol-gel and electrospinning methods:Effect of Na-excess content

The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.

Sol-Gel法制备ZnO压敏陶瓷及其电性

采用溶胶－凝胶（ｓｏｌ－ｇｅｌ）工艺制备ＺｎＯ电压敏陶瓷粉体．探讨其制备的最佳工艺条件：以 Ｚｎ（ＮＯ３）２与 ＮａＯＨ为反应前驱物制取胶体， Ｚｎ２＋浓度控制在 ０．５ｍｏｌ·Ｌ－１以上， ｐＨ值７．５左右，预烧温度３００℃，陶瓷烧结温度１２００℃；制得的压敏电阻的非线性系数α＝２８；研究了稀土Ｌａ２Ｏ３掺杂对该陶瓷电性的影响：低浓度掺杂时，可提高压敏电压，高浓度掺杂时；不呈现压敏特性；对粉体进行了Ｘ射线衍射和透射电镜分析，预烧后得到五元掺杂的ＺｎＯ粉体粒形呈球状，属六方晶系，粒径分布窄，约为４０～８０ｎｍ．

TiO_2的微波辐射Sol-Gel法制备及其光催化性能

采用微波辐射Sol Gel法在石英砂表面制备负载型TiO2 光催化剂 ,考察不同加热方式 ,微波功率以及微波加热温度对溶胶质量的影响 ,微波加热反应制备的溶胶粒子平均粒径小于常规加热反应制备得到的溶胶粒子 ,微波加热反应适宜条件是微波功率6 0 0W ,反应温度为 90℃ .以苯酚为光催化降解研究对象 ,考察了两种方式制备的负载型TiO2 光催化剂的催化性能 ,实验结果表明微波辐射Sol Gol法制备的负载型TiO2 光催化剂光催化性能也优于常规Sol Gel法制备的负载型TiO2 光催化剂 .

Sol-Gel技术与纳米材料的化学剪裁

本文以ＳｉＯ２纳米材料为实例，阐述了ｓｏｌ－ｇｅｌ化学的基本概念，讨论了ＳｉＯ２纳米材料在结构剪裁和性能调控方面的研究进展和前沿问题，并指出ｓｏｌ－ｇｅｌ技术已经成为实现化学剪裁合成纳米材料的主要手段。

纳米晶钛酸钡的Sol-gel法制备及其尺寸效应

采用sol-gel法制备了不同粒径的钛酸钡(BT)纳米晶粉.XRD、Raman光谱和DSC测试结果显示,随着退火温度的升高,晶粒长大,晶胞的a轴逐渐减小,c轴逐渐增大.粒径在54nm左右时,钛酸钡由顺电立方相向铁电四方相结构转变,在立方-四方相变过程中,晶胞略微膨胀.随着粒径的减小,正交-四方相变温度升高,四方-立方相变温度降低,Raman谱峰降低和宽化,粒径为38nm左右时四方相的特征峰消失.

不同Ti/Ba摩尔比的钛酸钡纳米晶粉体的Sol-gel法制备与表征

采用Ｓｏｌ－ｇｅｌ法制备了不同Ｔｉ／Ｂａ摩尔比的ＢａｙＴｉｘＯ３（ｘ／ｙ＝０．９９０，１．０００，１．０１０，１．０２０，１．０４５）纳米晶粉体。应用热分析、Ｘ射线粉末衍射、激光和透射电镜等技术对干凝胶热分解历程和粉体性能进行了研究，发现随Ｔｉ／Ｂａ摩尔比的增加，粉体的平均晶粒尺寸、晶体结构和粉体粒度分布各呈现规律性变化。

Sol-Gel法合成HAP的结晶特征及其对F^-离子吸附性能研究

用ｓｏｌ－ｇｅｌ法合成了具有纳米级尺寸的ＨＡＰ；采用ＸＲＤ，ＩＲ，ＢＥＴ比表面积测定，静、动态吸附等方法研究了不同Ｃａ／Ｐ摩尔比和煅烧温度合成的ＨＡＰ的比表面积、结晶度、晶粒尺寸、晶格缺陷度、热稳定性、平衡吸氟量；探讨了吸氟机理和行为．结果表明：ｓｏｌ－ｇｅｌ法合成的ＨＡＰ在常温、常压、不调ｐＨ的操作条件下，有较大的吸氟能力，且无二次污染，可作为绿色环境材料．

多孔氧化铝模板结合sol-gel旋转涂敷法制备PZT纳米管

利用溶胶-凝胶旋转涂敷法在通孔的多孔阳极氧化铝(PAA)模板中制备了锆钛酸铅(PZT)纳米管,研究了溶胶浓度对样品形貌的影响。利用SEM和TEM观察了纳米管阵列和单根纳米管的形貌,采用XRD和EDS图谱分析了纳米管的相结构和化学元素组成。结果表明合成的PZT纳米管结晶良好,具有钙钛矿结构(属于四方晶系);纳米管具有较高的韧性但表面较粗糙,直径和管壁厚度分别约为75和7nm,直径与原始PAA模板的孔径相吻合。在一定范围内调节PZT溶胶的浓度(0.1～0.4mol/L),均能在PAA模板的孔洞中形成PZT多晶纳米管,且组成PZT纳米管的晶粒随着溶胶浓度的增加而变大。

Sol-Gel法制备PZT薄膜及其抗疲劳性能研究进展

综述了Ｓｏｌ－Ｇｅｌ法制备ＰＺＴ系列铁电薄膜各种因素对薄膜微结构及性能的影响，分析了铁电薄膜极化疲劳微观机制，提出了优化的工艺条件及极化疲劳改善方法。

纳米掺铁二氧化钛的sol-gel法制备与表征(Ⅰ)热重红外联用分析掺铁二氧化钛凝胶的热分解和晶化特性

本文通过热分析、红外联用和 X射线衍射分析了不同煅烧温度下的纳米掺铁二氧化钛样品，研究了 sol-gel方法制备的纯二氧化钛和掺铁二氧化钛干凝胶的热分解和晶化过程。结果表明，干凝胶有较为明显的两个阶段的热分解。在实验条件下得到的二氧化钛干凝胶粉为无定形，无定形二氧化钛加热晶化过程是一个持续的过程，没有明显的晶化温度。

Sol-gel法制备纳米SnO_2气敏材料的研究

用Sol gel法制备SnO2 纳米粒子 ,并用XRD、紫外吸收光谱和激光Raman光谱进行了表征和分析。XRD实验证实了所制备的粒子具有较理想的纳米尺寸 ,其粒径随热退火温度升高而增大 ;Raman光谱表明 ,低温退火时SnO2 纳米材料的氧缺位较大 ;紫外吸收光谱表明退火温度在 30 0～ 5 0 0℃粒径变化很大 ,但光的吸收稳定不变。可望利用这些性质 ,提高SnO2 气敏器件的性能。