共查询到19条相似文献,搜索用时 156 毫秒
1.
用化学共沉淀法制备了α-Fe2O3掺杂的In2O3纳米晶微粉,研究了α-Fe2O3掺杂对In2O3电导和气敏性能的影响.结果表明,α-Fe2O3和 In2O3间可形成有限固溶体In2-xFexO3(0≤x≤0.40);Fe3+对 In2O3晶格中In3+格位的部分取代,大大增强了阴阳离子间的结合力,导致材料中氧空位Vox数骤降、自由电子的浓度变稀和电导下降.n(Fe3+):n(In3+)=5:5的共沉淀粉于 800℃下灼烧 4 h所得的 α-Fe2O3掺杂In2O3传感器元件,对 45μmol·L-1C2H5OH的灵敏度达54.0,为相同浓度干扰气体汽油的8倍多. 相似文献
2.
氧化铁在ZnO上分散的结构状态及其表征 总被引:1,自引:0,他引:1
采用(NH_4)_3[Fe(C_2O_4)_3]·xH_2O的水溶液含浸,Fe(NO_3)_3.9H_2O水溶液饱和浸渍(含浸)以及Fe(AcAc)_3的甲苯溶液热吸附三种方法制备了在ZnO上分散的氧化铁体系。用多种物理化学手段对用不同方法制备的分散体系进行了细致的表征,氧化铁在ZnO上形成单层分散是困难的。Fe~(3+)一般进入到ZnO载体的表层,结构环境类似于ZnFe_2O_4微晶中的Fe~(3+),分散的Fe~(3+)通常处于高自旋态,配位对称性并不是正交畸变。在ZnO上形成尖晶石的趋势最强。在亚单层铁含量范围内,通常形成表面ZnxFe_yO_z。当铁含量超过单层阈值时,既生成ZnFe_2O_4簇也有FeO_x簇存在。无论是FeO_x或ZnFe_2O4簇还是表面的Zn_xFe_yOz,其Fe_(3+)在实验温度范围内,很难被还原为零价铁,FeO_x较之Zn_xFe_yO_z物种难以还原且比体相a-Fe_2O_3中Fe~(3+)要难还原得多。由热吸附法制得的FeO_x和ZnFe_2O_4簇具有很低的催化活性,而由含浸法制得的表面Zn_xFe_yOz的反应性能有明显的改善。ZnO载体上不同含铁物种的反应性由Fe~(3+)的还原性及是否存在活泼 相似文献
3.
4.
用循环伏安和红外光谱法对α-Fe_2O_3在室温LiOH溶液中的锂化行为进行研究.采用X射线衍射(XRD)、电感偶合等离子体光源的原子发射光谱(ICP)对α-Fe_2O_3电极在第一、二次循环中不同时段进行了跟踪分析测量.实验结果揭示: α-Fe_2O_3能进行少量锂化;大量的α-Fe_2O_3在第一次放电和充电后反应生成Fe_3O_4;之后,Fe_3O_4的锂化行为不可避免地为Fe的析出、氧化反应所限制,但在用KOH作电解质溶液的对比实验时发现:α-Fe_2O_3在LiOH溶液中的充放电行为与它在KOH溶液中是不同的,主要表现为,1)在LiOH溶液中,锂化和Fe析出、氧化反应协调的结果是其充放电曲线平台高度比在同碱度 KOH溶液中降低了 100 mV左右, 2)与 K~(+)对比, Li~(+)的插入反应促进了α-Fe_2O_3到Fe_3O_4的转化. 相似文献
5.
6.
用XRD、TPR及固定床微反应器技术研究了微量Pt 和Pd 对Fe2O3/ZrO2 催化剂结构及性能的影响。结果表明,活性组分Fe3 + 与载体ZrO2 之间的相互作用会阻止载体从无定形ZrO2 到t-ZrO2 进而m - ZrO2 的转变,同时,促进Fe2O3 在ZrO2 表面的分散。微量Pt 或Pd 的加入对Fe2O3 在ZrO2 上的分散状态无明显影响,但使Fe2O3/ZrO2 的还原性能发生明显变化,表层Fe2O3 的还原性显著增强,导致M- Fe2O3/ZrO2 催化剂在NO+ CO反应中有更高的催化活性。N2 生成的选择性次序为Fe2O3/ZrO2 > Pd - Fe2O3/ZrO2 > Pt- Fe2O3/ZrO2 > Pd/ZrO2 > Pt/ZrO2 。 相似文献
7.
8.
9.
10.
11.
Comparison of reduction behavior of Fe2O3, ZnO and ZnFe2O4 by TPR technique 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《天然气化学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Advanced integrated gasification combined cycle (IGCC) power generation systems require the development of high-temperature,regenerable,desulfurization sorbents capable of removing hydrogen sulfide from coal gasifier gas to very low levels.As a sort of effective desufurizer,such as Fe2O3,ZnO and ZnFe2O4,it will endure strong reducing atmosphere in desulfurization process.The reduced degree of desufurizer can have an effect on its desulfurization reactivity.In this paper,Fe2O3,ZnO and ZnFe2O4 were synthesized by precipitation or co-precipitation at constant pH.After aging,washing and drying,the solids were calcined at 800℃.The reduction behaviors of sample were characterized by temperature-programmed reduction (TPR).It is found that there are two reduction peaks for Fe203 in TPR,and whereas no reduction peaks for ZnO are found.The reduction process of ZnFe2O4 prepared by co-precipitation is different from that of Fe2O3.ZnFe2O4 is easier to be reduced than Fe2O3.The activation energy of reduction process for Fe2O3 and ZnFe2O4 is obtained at different reduction periods. 相似文献
12.
铁酸锌掺杂对二氧化钛结构相变及光催化性能的影响 总被引:15,自引:0,他引:15
分别采用共沉淀法和溶胶-凝胶法制备铁酸锌和二氧化钛纳米粉体,较系统地研究了铁酸锌纳米掺杂对二氧化钛“锐钛矿→金红石”的结构相变及光催化性能的影响.结果表明,适量铁酸锌的掺杂可促进二氧化钛的结构相变,显著提高其光催化活性,在最佳掺杂浓度时,其光催化降解苯酚的效率可以提高2~3倍. 相似文献
13.
Fu L Wu Z Ai X Zhang J Nie Y Xie S Yang G Zou B 《The Journal of chemical physics》2004,120(7):3406-3413
Using nanosecond (ns) and femtosecond (fs) time-resolved absorption spectroscopies (pump-probe technique), the carrier dynamics in transition metal oxide nanocrystals of alpha-Fe2O3 and ZnFe2O4 was studied during the photolysis process. For Fe2O3 and ZnFe2O4 nanocrystals, the fs measurements detect similar profiles of a positive nonlinear absorption in their capped nanocrystals, whereas much weak signals in the naked particles. In the nanosecond measurements Fe2O3 and ZnFe2O4 nanocrystals show obvious excitation-power dependent absorption properties and at the low pump power they show weak photobleaching, but at high pump power they produce positive nonlinear absorptions. For Fe2O3 nanocrystals, the threshold power of negative absorption (bleach) to positive absorption increases with reducing size, whereas for the ZnFe2O4 samples, the threshold powers reach minimum at a critical size of 11 nm, grow for both the bigger and the smaller nanocrystals. These results reflect the influences of their microscopic magnetic couplings and carrier correlation on biexciton absorption in Fe2O3 and ZnFe2O4 nanocrystals. All the results indicate that the time resolved photoabsorption techniques are useful to study the microscopic spin interactions and carrier correlations in transition metal oxide nanocrystals. 相似文献
14.
研究了Na2O或K2O对苯胺和1,6己二醇气相合成1-苯基氮杂环庚烷的CoO/SiO2-Al2O3催化剂的作用,并采用X射线衍射、透射电子显微镜、H2-程序升温还原、NH3-程序升温脱附等技术对催化剂进行了表征.结果表明,Na2O助剂能增加催化剂的弱酸中心数,减少中强酸中心数,使催化剂的选择性得到提高.加入K2O使催化剂的弱酸中心数显著减少,并使CoO在反应过程中易于烧结,因此不利于1–苯基氮杂环庚烷的合成. 相似文献
15.
ZnFe2O4中阳离子分布对苯酚H2O2羟化制苯二酚催化活性的影响 总被引:2,自引:0,他引:2
具有尖晶石结构的铁酸盐是苯酚H2O2羟化合成苯二酚的有效催化剂.分别用共沉淀和水热法制备了ZnFe2O4,并用Mossbauer,XRD和ESR等方法予以表征.发现不同方法制备的ZnFe2O4中阳离子在四面体和八面体位置的分布不同,认为阳离子分布影响了催化活性. 相似文献
16.
The nano-ZnFe2O4/TiO2 films possess the functions of desulfurization and degradation for organic pollutants. The sols of ZnFe2O4/TiO2 were prepared by sol-gel method and coated on glass and porous ceramic by vertical coating and dipping-lift processes, respectively, and the samples were obtained after drying and sintering. The composition, appearance, absorption spectrum of the films, and the influence of the film on porous ceramic performances were analyzed using SEM, AFM, UV-Vis spectrometer, and mercury porosimeter, respectively, to determine the operation parameters of the multifunction porous ceramic elements for gas-purification. 相似文献
17.
Tb掺杂SiO2-B2O3-NaF玻璃的制备及发光性质 总被引:5,自引:0,他引:5
使用正硅酸乙酯、硼酸和氟化钠为前驱体,0.10 mol•L-1TbCl3溶液为掺杂剂,通过溶胶-凝胶方法制备了Tb3+掺杂的SiO2-B2O3-NaF玻璃,研究了Tb3+在SiO2-B2O3-NaF体系中的发光性质,结果显示发光体能产生强的绿色发光(544 nm),归属于Tb3+的5D4—7F5电子跃迁.Tb3+含量不同时,除发光强度不同外,其发射光谱基本相同,并且在低掺杂Tb3+样品和低退火温度样品中检测到了来自5D3跃迁产生的峰,其跃迁随Tb3+掺杂浓度的增加和退火温度的升高而发生猝灭,这种现象归因于5D3-5D47F6—7F0和/或5D3—7F07F6—5D4跃迁中发生了交叉弛豫现象.Tb3+在SiO2-B2O3-NaF玻璃中的激发光谱由一个宽峰和一系列窄峰组成,宽峰最大波长位于230 nm,对应于Tb3+的4f 8—4f 75d 1跃迁,一系列窄峰位于300~380 nm处,归属于4f 8跃迁,所有发光材料的XRD和TEM测试显示材料是非晶态的. 相似文献
18.
测定了含ZrO2的Rh/γ-Al2O3催化剂上NO+C2H4和NO+C2H4+O2的反应活性,并应用TPR、XRD、BET比表面等表征了ZrO2的加入方式和晶型对Rh/γ-Al2O3催化剂活性和结构的影响。结果表明,ZrO2的加入一定程度地抑制了Rh3+与γ-Al2O3之间的相互作用和γ-Al2O3的相变,提高了催化剂的热稳定性,明显提高了850℃老化样品的NO+C2H4反应活性。对于NO+C2H4+O2反应,含ZrO2样品的选择还原活性却较低,表明反应机理不同,而且ZrO2对C2H4的深度氧化有促进作用,但老化后活性下降幅度比不含ZrO2的样品小。 相似文献
19.
Lei Qi Mei Wang Jianbin Xue Qiyuan Zhang Prof. Feng Chen Qianqian Liu Prof. Wanfei Li Prof. Xinheng Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(59):14638-14644
Photocatalytic Z or S scheme merits higher redox potentials and faster charge separation. However, heterostructure photocatalysts with band gaps of bulk materials often have a type I band structure leading to poor photocatalytic activity. In view of this, we report simultaneous tuning of band gaps of Cu2O and TiO2, where quantum dot Cu2O nanoparticles were formed on doped TiO2 with Ti3+. The reduced size of Cu2O made its conduction band more negative, whereas the introduction of Ti3+ made the absorption edge red shift to the visible light region. The as-formed heterostructure enabled an S-Scheme mechanism with remarkable activity and stability for visible light photodegradation of 4-chlorophenol (4-CP). The as-obtained photocatalysts’ activity demonstrated ca. 510-fold increase as compared to individual ones and a mechanical blend. The as-obtained photocatalysts maintained over 80 % for 5 cycles and 2 months exposure to O2 did not decrease the degradation rate. ESR characterization and scavenger experiments proved the S-Scheme mechanism. 相似文献