CoFe2O4的制备、结构表征与气敏性能

采用共沉淀方法,以可溶性钴盐和铁盐为源物质,以氢氧化物作为沉淀剂,制备出了具有尖晶石结构的CoFe2O4复合氧化物粉末.由CoFe2O4粉体制成的旁热式厚膜气敏元件无需掺杂,对乙醇、丙酮、乙酸具有较高的灵敏度.     

CoFe2O4的制备、结构表征与气敏性能

采用共沉淀方法,以可溶性钴盐和铁盐为源物质,以氢氧化物作为沉淀剂,制备出了具有尖晶石结构的CoFe2O4复合氧化物粉末.由CoFe2O4粉体制成的旁热式厚膜气敏元件无需掺杂,对乙醇、丙酮、乙酸具有较高的灵敏度.     

铁酸钴磁性液体的制备及稳定性

用化学沉淀法制备CoFe2O4超微颗粒,以CoFe2O4超微颗粒作为核心磁性材料,经表面活性剂作用后悬浮于水载液中得到铁酸钴磁性液体.利用震动磁强计对磁性液体进行了磁场测试,用X-射线进行了物相分析并计算了晶粒的尺寸.通过控制实验工艺,CoFe2O4磁性颗粒的大小平均为4.63nm,形成了纳米级铁酸钴颗粒;通过对表面活性剂的选择和复配,得到了稳定的铁酸钴磁性液体,饱和磁化强度达到16.202GS,矫顽力和剩磁均趋于零.     

制备工艺对铁酸钴纳米颗粒大小的影响

以FeCl3和CoCl2为原料,采用共沉淀法制备CoFe2O4纳米颗粒.研究工艺条件对磁性颗粒大小的影响,经X射线衍射仪分析,得出纳米颗粒的大小为11.1～20.4nm之间.通过比较分析得出:浓度配比对颗粒大小基本上无影响,焙烧温度和焙烧时间对颗粒大小有较大的影响,焙烧温度300℃,焙烧时间1h时得到的颗粒最小.     

磁性材料与磁性纸的制备

介绍了常用磁性材料Fe3O4、γ-Fe2O3及CoFe2O4及其制备方法。综述了磁性纤维及磁性纸的制备方法,回顾了细胞腔内填充法和原位复合法制备磁性纤维和磁性纸的研究进展情况,对两种方法制备的磁性纸的印刷适性进行了分析。指出,细胞腔填充法制备的磁性纸适合于彩色印刷,原位复合法制备的磁性纸印刷后适合做夹层,可采用特殊检测仪器检测图文达到防伪的目的。随着研究的深入,磁性纸将在更多的领域得到应用。     

Fe3+-草酸-葡萄糖酸盐媒质的电化学还原染色工艺的研究

在以石墨电极为阴阳电极[阳极电解池中加入15 g/L H2SO4作为电解液,阴极电解池中加入Fe2(SO4)3、NaOH、C2H2O4、Ca(C6H11O7)2作为还原染液]电解装置中,进行还原大红R的电化学还原染色.结果表明:还原大红R为4g/L,Fe2(SO4)3为8g/L,NaOH为50 g/L,C2H2O4为12.6 g/L,Ca(C6H11O7)2为24.4 g/L,工作电压为4 V,还原时间为10 min,阴极面积为40 cm2时,具有良好的染色效果.     

SiO2改性对LiMn2O4电化学性能的影响

用溶胶-凝胶法在锂离子电池阴极材料LiMn2O4的表面包覆一层Si(OH)4,然后进行热处理,制备出用SiO2改性的LiMn2O4,并对材料进行了X射线衍射、恒电流充放电、比表面积等的比较.结果表明:用SiO2改性后的LiMn2O4的尖晶石基本结构没有改变,而其电化学循环性能有显著的提高.改性后的LiMn2O4之所以具有更好的循环性能是与其微结构和比表面的变化有关的.     

杨木爆破浆两段组合漂白的研究

研究了杨木SEP H2O2两段漂白和以甲脒亚磺酸(FAS)代替H2O2进行组合漂白以及H2O2-Na2S2O4两段组合漂白.其结果表明:当H2O2总用量为5%,分配比例P1:P2为1:4时,杨木SEP H2O2-H2O2两段漂白漂后纸浆白度为64.4%SBD,白度增值为23.4%SBD,比在相同的H2O2用量下单段漂白高出1.2%SBD.H2O2-FAS两段漂白和H2O2-Na2S2O4两段组合漂白,白度增值可分别达到24.2%SBD和17.3%SBD.     

催化合成环氧化大豆油SO2-4-ZrO2-HMS催化剂制备

通过ZrOCl2沉淀和H2SO4浸渍HMS介孔分子筛制备新型负载型固体超强酸催化剂(SO2-4-ZrO2-HMS),以H2O2和甲酸为氧化剂,以大豆油环氧化为探针反应,考察催化剂制备条件对催化性能影响.结果表明,制备SO2-4-ZrO2-HMS催化剂最佳条件是:ZrOCl2浓度为0.2 mol/L、H2SO4浓度为0.75 mol/L、焙烧温度为550℃;SO2-4-ZrO2-HMS催化剂对大豆油环氧化具有良好催化性能,环氧值达4.40、酸值达0.22,产品具有色泽优良、容易分离优点.     

Mo肥对烟叶产量品质的影响

通过不同浓度、不同时期和不同方法对烤烟施用Mo6+的试验表明烤烟施Mo6+的协调,烟株生理代谢,改善烟株植物学性状,使烟叶增产、增质.试验各处理以浓度0.5g/kg(NH4)6Mo7O24·4H2O在还苗期叶面喷施1次效果最佳,浓度1.5g/kg(NH4)6Mo4O24·4H2O在团棵期叶面喷施2次及浓度2.5g/kg(NH4)6Mo7O24·4H2O在旺长期根部浇施1次的效果居第2位,施Mo6+处理均优于对照.     

CoFe_2O_4/Co_3Fe_7-Co纳米核壳结构的微波吸收性能

利用溶胶-凝胶法制备了不同粒径的CoFe_2O_4纳米颗粒,再通过H_2热还原法在颗粒表面形成Co_3Fe_7-Co磁性金属纳米壳层,研究不同退火温度、相同还原温度下不同样品的静态和动态磁性.结果表明,还原后样品的饱和磁化强度以及分别代表介电损耗和磁损耗的复数介电常数的虚部和复磁导率的虚部都得到提高,且通过线传输理论计算得到,纳米核壳结构CoFe_2O_4/Co_3Fe_7-Co可有效提高材料的微波吸收性能.     

激光焊接金刚石工具过渡层预合金粉末的试验研究

目前可以用于制备激光焊接金刚石工具过渡层粉末的方法主要有机械混合法、雾化法和化学共沉淀法。化学共沉淀法生产的粉末成分均匀,实现了粉末的预合金化,并且设备简单,生产成本低。此次试验采用草酸盐化学共沉淀法,成功制备了3种不同成分的激光焊接金刚石工具过渡层预合金粉末。焊接强度测试表明,3种粉末的焊接强度均满足欧盟EN13236安全标准,其中2#粉末的焊缝强度最高。X射线物相分析结果表明,3种粉末的主相都是Co3Fe7和CoFe。此外,固定Fe与Co的质量比,加入2wt.%的铜可以有效提高预合金粉末过渡层的焊接强度和稳定性。这是因为,Cu原子完全溶入到Co3Fe7或CoFe晶胞中并形成固溶体,产生了固溶强化。     

金属离子对卤醇脱卤酶发酵生产的影响

在以基因工程大肠杆菌为生产菌发酵生产卤醇脱卤酶过程中,某些金属离子对卤醇脱卤的生产有较大的影响。首先,通过单因子实验确定几种典型微量元素的最佳产酶浓度,其次,通过2水平析因实验和最陡爬坡实验确定了显著影响因子及其浓度拐点,其分别是ZnSO4.7H2O、CoCl2.6H2O和FeSO4.7H2O。最后,运用响应面分析法确定了微量元素的最佳配比为FeSO4.7H2O 11.86g/L,ZnSO4.7H2O 2.0g/L,MnSO4.H2O 1.0g/L,CaCl20.05g/L,CoCl2.6H2O 1.2g/L,CuSO4.5H2O 0.8g/L。与对照生产水平相比,当添加最佳配比金属离子到培养基中后,酶活提高了2倍。     

Investigation of formaldehyde oxidation over Co3O4-Ce2 and Au/Co3O4-CeO2 catalysts at room temperature: effective removal and determination of reaction mechanism

Formaldehyde is regarded as the major indoor pollutant emitted from widely used building and decorative materials in airtight buildings, which should be eliminated under indoor environmental conditions. We report here catalytic oxidation process of formaldehyde over mesoporous Co(3)O(4), Co(3)O(4)-CeO(2), Au/Co(3)O(4), and Au/Co(3)O(4)-CeO(2) catalysts and their excellent catalytic performances at room temperature. These catalysts were prepared by a "nanocasting" method with the mesostructure generated from SBA-15 silica with 2D structure. The adsorbed surface species in the formaldehyde oxidation process are analyzed, and some key steps in the oxidation pathway, active sites, and intermediate species are proposed. Among the detected species, some kinds of formate species formed on the catalysts were indentified as intermediates, which further transformed into bicarbonate or carbonate and which decomposed to carbon dioxide. The role of the mesoporous Co(3)O(4) and the gold nanoparticles in the mechanism are also revealed.     

In situ Fenton reagent generated from TiO2/Cu2O composite film: a new way to utilize TiO2 under visible light irradiation

TiO2/Cu2O composite is prepared by a simple electrochemical method and coated on glass matrix through a spraying method. The obtained composite is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of TiO2/Cu2O composite films with different ratio of TiO2 and Cu2O on photodegradation of the dye methylene blue under visible light is investigated in detail. It is found that the photocatalytic activity of TiO2/Cu2O composite film with the presence of FeSO4 and EDTA is much higher than that for the similar system with only TiO2 and Cu2O film respectively. Without the presence of FeSO4 and EDTA, there is no degradation for methylene blue. The exploration of the optimized parameters for the degradation of methylene blue by using TiO2/Cu2O composite film as catalyst under visible light was also carried out. The most significant factor is the amount of Ti02 in the composite, and the second significant factor is the concentration of FeSO4. During the degradation of methylene blue under visible light, TiO2/Cu2O composite film generates H202, and Fenton regent is formed with Fe2+ and EDTA, which is detected in this study. The mechanism for the great improvement of photocatalytic activity of TiO2/Cu2O composite film under visible light is proposed by the valence band theory. Electrons excitated from TiO2/Cu2O composite under visible light are transferred from the conduction band of Cu2O to that of Ti02. The formed intermediate state of Ti 3+ ion is observed by X-ray photoelectron spectroscopy (XPS) on the TiO/Cu2O composite film. Additionally, the accumulated electrons in the conduction band of TiO2 are transferred to oxygen on the TiO2 surface for the formation of O2- or O2(2-), which combines with H+ to form H2O2. The evolved H202 with FeSO4 and EDTA forms Fenton reagentto degrade methylene blue. Compared to the traditional Fenton reagent, this new kind of in situ Fenton reagent generated from TiO2/Cu2O composite film does not need to supply H202. It is expected to be easily recycled, which may reduce second pollution and the cost of wastewater treatment. Moreover, this TiO/Cu2O composite film with FeSO4 and EDTA provides a new way to take advantage of TiO2 under visible light.     

K2B4O7-Li2B4O7-MgB4O7-H2O四元体系288K相平衡研究

采用等温溶解平衡法研究了288 K时K2B4O7-L i2B4O7-MgB4O7-H2O四元体系的相平衡关系,测定了平衡液相的等温溶解度和密度。研究发现：该体系属于简单共饱和体系,无复盐和固溶体生成;该四元体系288 K时的等温溶解度图存在三个固相结晶区,其平衡固相分别为：Li2B4O7.3H2O,K2B4O7.4H2O和MgB4O7.9H2O;一个共饱点E,三条单变量曲线E1-E,E2-E,E3-E;文章最后对实验结果进行了简单讨论。     

Density functional theory studies on the structures and water-exchange reactions of aqueous Al(III)-oxalate complexes

The structures and water-exchange reactions of aqueous aluminum-oxalate complexes are investigated using density functional theory. The present work includes (1) The structures of Al(C(2)O(4))(H(2)O)(4)(+) and Al(C(2)O(4))(2)(H(2)O)(2)(-) were optimized at the level of B3LYP/6-311+G(d,p). The geometries obtained suggest that the Al-OH(2) bond lengths trans to C(2)O(4)(2-) ligand in Al(C(2)O(4))(H(2)O)(4)(+) are much longer than the Al-OH(2) bond lengths cis to C(2)O(4)(2-). For Al(C(2)O(4))(2)(H(2)O)(2)(-), the close energies between cis and trans isomers imply the coexistence in aqueous solution. The (27)Al NMR and (13)C NMR chemical shifts computed with the consideration of sufficient solvent effect using HF GIAO method and 6-311+G(d,p) basis set are in agreement with the experimental values available, indicating the appropriateness of the applied models; (2) The water-exchange reactions of Al(III)-oxalate complexes were simulated at the same computational level. The results show that water exchange proceeds via dissociative pathway and the activation energy barriers are sensitive to the solvent effect. The energy barriers obtained indicate that the coordinated H(2)O cis to C(2)O(4)(2-) in Al(C(2)O(4))(H(2)O)(4)(+) is more labile than trans H(2)O. The water-exchange rate constants (k(ex)) of trans- and cis-Al(C(2)O(4))(2)(H(2)O)(2)(-) were estimated by four methods and their respective characteristics were explored; (3) The significance of the study on the aqueous aluminum-oxalate complexes to environmental chemistry is discussed. The influences of ubiquitous organic ligands in environment on aluminum chemistry behavior can be elucidated by extending this study to a series of Al(III)-organic system.