纳米LaFeO3的制备和表征及其气相光催化性能

以硝酸镧和硝酸铁为原料,柠檬酸为络合剂,利用溶胶凝胶法制备了钙钛矿结构的纳米LaFeO3,并用TG-DTA、XRD、BET、SPS等方法对样品进行了表征．重点考察了热处理温度对光催化降解气相正戊炕活性的影响,探讨了表面光电压信号与光催化活性的关系．结果表明：热处理温度为500℃时,钙钛矿结构的纳米LaFeO3开始生成,随着焙烧温度升高,结晶度变高．在光催化实验中,500℃焙烧的纳米LaFeO3表现出较高的光催化活性,且焙烧温度升高,光催化活性下降,与表征结果一致．说明热处理温度越低,LaFeO3纳米晶尺寸越小,SPS信号越弱,光催化活性越高．     

The preparation,characterization, and catalytic performance of porous fibrous LaFeO3 perovskite made from a sunflower seed shell template

LaFeO₃ perovskite with a porous fibrous structure was successfully synthesized using a sunflower seed shell as a template. To investigate the effects of this template, a sample was prepared without a template via the same procedure. Through various characterization techniques, such as X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, N₂ adsorption-desorption analysis, X-ray photoelectron spectroscopy, oxygen temperature programed desorption, and hydrogen temperature programed reduction, the physiochemical properties of the samples were investigated. The results showed that the sample made with a template had a larger surface area and a larger amount of adsorbed oxygen, which further illustrated that the sunflower seed shell template had a significant impact on the physiochemical properties of the samples. Furthermore, we explored the catalytic activity for nitric oxide (NO) oxidation, and studied the factors affecting it, which highlighted its potential application in automobile exhausts.     

纳米LaFeO3的制备及H2S气敏性能研究

以无机物K3[Fe(CN)6]和La(NO3)3·nH2O为原料,用热分解配合物前驱体法制备了LaFeO3纳米粉体.用X-射线粉末衍射仪(XRD)和透射电镜(TEM)对产物的物相、形貌进行了表征.本工作还以沉淀法相同温度条件下煅烧出的LaFeO3作了对比.结果显示:热分解法在煅烧温度为700℃即可生成纳米晶LaFeO3,TEM显示产物为均匀的椭球形颗粒,充分表明该方法制备的材料具有良好分散性,且纯度较高.将合成材料制备成旁热式气敏元件,气敏性能测试结果表明:合成材料对H2S具有高的灵敏度和选择性,在192℃工作时,对35μL/L H2S气体的灵敏度可达72倍.     

Mn-doped perovskite-type oxide LaFeO3 as highly active and durable bifunctional electrocatalysts for oxygen electrode reactions

Perovskite oxides based on the alkaline earth metal lanthanum for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline electrolytes are promising catalysts, but their catalytic activity and stability remain unsatisfactory. Here, we synthesized a series of LaFe_1−xMn_xO₃ (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1) perovskite oxides by doping Mn into LaFeO₃ (LF). The results show that the doping amount of Mn has a significant effect on the catalytic performance. When x = 0.5, the catalyst LaFe_0.5Mn_0.5O₃ (LFM) exhibits the best performance. The limiting current density in 0.1 mol·L⁻¹ KOH solution is 7 mA·cm⁻², much larger than that of the commercial Pt/C catalyst (5.5 mA·cm⁻²). Meanwhile, the performance of the doped catalyst is also superior to that of commercial Pt/C in terms of the long-term durability. The excellent catalytic performance of LFM may be ascribed to its abundant O²⁻/O⁻ species and low charge transfer resistance after doping the Mn element.     

铁酸镧薄膜的研究进展

铁酸镧(LaFeO3)是一种典型的具有钙钛矿(ABO3)结构的稀土复合金属氧化物,由于具有稳定的晶体结构、独特的电磁、催化和气敏性等特点,因此它在电学、磁学和传感器等领域都有着广泛的应用前景而成为国内外研究的热点.此外,LaFeO3还是少数的同时具有反铁磁性和铁电性的单相多铁材料之一,在信息存储、磁传感器和自旋电子器件等方面都有潜在的应用前景.本文综述了LaFeO3薄膜的结构及性能、制备工艺的研究进展,并展望了LaFeO3薄膜研究趋势.     

制备方法对LaFeO3可见光光催化活性的影响

采用4种方法制备LaFeO3催化剂,探讨制备方法对LaFeO3催化剂结构和性能的影响.用XRD、UV-Vis DRS、PL和SEM等手段对样品进行表征.以罗丹明B为目标降解物,考察催化剂的可见光光催化活性.研究结果表明:这4种方法均能制备单一的钙钛矿型LaFeO3催化剂,其中,共沉淀法制备的催化剂具有最大的晶粒尺寸,最小的比表面积,仅为0.4 m2/g,显示出最强的光催化活性;在可见光照射下反应140 min,罗丹明B的脱色率达到53.6%.柠檬酸络合法制备的催化剂的比表面积最大,为8.1 m2/g,但其脱色率仅为9.0%.由此可推断,小的颗粒和高的比表面积并不是总有利于催化剂的光催化活性,大的晶粒和规整的表面形貌等对催化活性也具有决定性的影响.     

铁酸镧粉体的合成及其光催化性能研究

采用低温熔盐法制备了LaFeO3光催化剂,用X射线衍射仪（XRD）和透射电子显微镜（TEM）等测试手段对材料的结构、粒径进行了分析和表征,研究了其对罗丹明B溶液的光催化降解性能.试验表明：煅烧温度对LaFeO3粉体的结晶发育等具有重要的影响;光催化降解试验数据表明低温熔盐法制备的LaFeO3粉体具有较高的催化活性.     

小粒子尺寸纳米LaFeO3的制备、表征及光催化性能

利用KH331调制的柠檬酸溶胶一水热法合成了LaFeO3纳米粒子,并通过XRD、TEM、BET等进行了表征.重点研究了KH331对LaFeO3粒子尺寸的调控以及对光催化活性的影响.实验结果表明:KH331的引入显著地减小了LaFeO3的粒子尺寸,KH331的用量越大,LaFeO3粒子尺寸越小,并对KH331的作用机制进行了分析.而且适量KH331的引入可以使LaFeO3的可见光催化活性得到较大提高.     

催化法制备多壁碳纳米管

采用复合氧化物LaFeO3,C2H2为碳源,合成了高纯度的碳纳米管,考察了温度对产量的影响。利用TEM,HR－TEM,XRD,Raman等手段对所制备的纳米碳管进行了观察和表征。碳纳米管管径均匀,石墨化程度较高,易于纯化。     

Enhanced piezoelectricity and temperature stability in LaFeO3-modified KNN-based lead-free ceramics

(0.96-x)K_0.48Na_0.52NbO₃-0.04Bi_0.5Na_0.5ZrO₃-xLaFeO₃ ceramics (abbreviated as KNN-BNZ-LF1000x) with enhanced piezoelectric performance and temperature stability were prepared by the conventional solid-state sintering method. It was found that the incorporation of LaFeO₃ gradually shifted the O-T phase boundary toward room temperature, while maintaining the Curie temperature above 300°C. The optimal piezoelectricity was found at x = 0.006, with relatively high piezoelectric constant d₃₃ of 345 pC/N as well as a high level of unipolar strain (0.126% at 3 kV/mm). Benefiting from the diffused phase transition induced by appropriate amount of LaFeO₃ content, the KNN-BNZ-LF6 sample possessed greatly enhanced the temperature stability of , which varied less than 8% in the temperature range of 20°C-100°C.