Improved electrochemical properties in the Li3Fe2(PO4)3 by titanium and vanadium doping

Ti⁴⁺ ions were introduced to the VO₄^3- substituted Li₃Fe₂(PO₄)₃ by sol-gel method. Simultaneous substitution of Ti⁴⁺ for Fe³⁺ and VO₄^3- for PO₄^3- in the Li₃Fe₂(PO₄)₃ resulted in a net improvement in the rate capability and cycling performance, as compared with the single Ti⁴⁺ or VO₄^3- substituted compound.     

尖晶石型高熵氧化物的制备和电化学性能

采用溶液燃烧法制备了化学组成均一的尖晶石型（Cr_0.2Fe_0.2Mn_0.2Ni_0.2M_0.2）₃O₄（M=Co,Zn,Mg）高熵氧化物（HEOs）纳米晶粉体,并将3种高熵氧化物用作锂离子电池负极材料,研究了活性过渡金属Co和Zn阳离子与非活性Mg阳离子对电化学性能的影响.结果表明,由于具有高构型熵稳定的晶体结构,3种高熵氧化物均表现出优异的循环稳定性,其中含有非活性Mg离子的高熵氧化物（Cr_0.2Fe_0.2Mn_0.2Ni_0.2Mg_0.2）₃O₄不仅具有更高的初始比容量（1300 mA·h/g）和倍率性能（在3 A/g电流密度下比容量约为450 mA·h/g）,且在循环500次后Li⁺的扩散系数为其它2种高熵氧化物的3倍以上.（Cr_0.2Fe_0.2Mn_0.2Ni_0.2Mg_0.2）₃O₄电化学性能提高的原因是非活性Mg离子不仅避免了锂化过程中活性物质的团聚,还提高了锂离子的扩散系数.     

Effects of doping Fe cations on crystal structure and thermal expansion property of Yb2Mo3O12

Crystal structures and thermal expansion properties of Yb_(2-x)Fe_xMo_3O_(12)(x=0.0,0.6,1.0,1.1,1.4) solid solutions have been studied by X-ray powder diffraction(XRPD) at different temperatures.Rietveld analysis of the XRPD data shows that Yb_(2-x)Fe_xMo_3O_(12) solid solutions adopt orthorhombic structure and have variable thermal expansion coefficients controlled by the ratio of Yb~(3+) to Fe~(3+).Yb_2Mo_3O_(12) shows anisotropic negative thermal expansion property,induced by the reductions in average Yb-O-Mo angle and average apparent Mo2-O bond length with increasing temperatures.As more Yb~(3+) substituted by Fe~(3+),the linear thermal expansion coefficients of Yb_(2-x)Fe_xMo_3O_(12) increase from negative to positive.A near-zero thermal expansion coefficient of 0.55×10~(-6)K~(-1) for Yb_(0.6)Fe_(1.4)Mo_3O_(12) is observed in the temperature range of 573-873 K     

碱性介质中制备纳米四氧化三锰及其超级电容特性

比较了不同碱溶液中纳米Mn₃O₄的制备及其超级电容性能。用X射线粉末衍射仪、扫描电子显微镜和原子力显微镜等技术手段分别测试了晶体结构和表面形貌。用循环伏安、恒流充放电和交流阻抗测试了材料的电化学性能。结果表明,在氢氧化钠、氨水中Mn²⁺沉淀氧化可以直接制备纳米Mn₃O₄;碳酸钠中先生成MnCO₃,加氢氧化钠可转化为纳米Mn₃O₄。NaOH、NH₃和Na₂CO₃ 3种介质中制备的Mn₃O₄晶粒尺寸分别为29.5、20.2和36.3 nm。纳米Mn₃O₄经连续充放电循环后可活化为Birnessite-type MnO₂。氨水中制备的Mn₃O₄活化后比容量最大,达到239 F/g,是一种具有应用前景的超级电容器材料。     

NiO/Mn3O4整体式催化剂催化分解臭氧的性能

将原料Ni(NO₃)₂·6H₂O、Mn₃O₄粉末和拟薄水铝石用球磨机球磨,以所得的浆料浸渍堇青石,经过焙烧,得到不同比例的NiO/Mn₃O₄催化剂。 通过催化分解臭氧活性测试发现,在空速为20000 h^-1时, 30NiO/Mn₃O₄(NiO占总质量的30%)催化剂的活性最高,臭氧分解率达到98%,催化剂活性稳定。 当提高空速为40000 h^-1,50NiO/Mn₃O₄(NiO占总质量的50%)催化剂的活性最高,臭氧分解率在90%左右,并且出现失活现象。 通过X射线衍射(XRD)、程序升温(TPR)、X射线光电子能谱分析(XPS)、BET比表面积法等表征,发现Mn₃O₄和NiO复合催化剂的比表面积大于单一金属氧化物催化剂的比表面积并且在Mn₃O₄和NiO复合催化剂中Mn₃O₄与NiO发生电子相互作用。 催化剂中的Mn₃O₄与NiO的协同催化作用。 使得Mn₃O₄与NiO混合物催化剂的还原温度降低,分解臭氧(O₃)活性提高。     

12-钨磷酸及其盐的酸性与催化性能的研究

红外法研究结果表明12-钨磷酸Fe³⁺、Mg²⁺和Na⁺盐都具有L酸点和B酸点。用Benesi法测得10种12-钨磷酸盐的酸强度顺序为(Al³⁺、Fe³⁺、La³⁺、Cu²⁺、Cd²⁺>Zn²⁺>(Ca²⁺、Mg²⁺>(Na⁺、Li⁺,其酸量与抗衡阳离子的离子势和电负性大体成线性关系。还看出酸量与所含结晶水量有关。催化剂的酸量与其对异丙醇脱水反应和丁烯-1异构化反应的催化活性的关系表现出不同的特征,这可用“体相型”和“表面型”催化作用的不同特点来解释。     

Enhanced Electrochemical Performance of Na0.67Fe0.5Mn0.5O2Cathode with SnO2 Modification

P2-type layered oxide Na_0.67Fe_0.5Mn_0.5O₂ is recognized as a very promising cathode material for sodium-ion batteries due to the merits of high capacity, high voltage, low cost, and easy preparation. However, its unsatisfactory cycle and rate performances remain huge obstacles for practical applications. Here, we report a strategy of SnO₂ modification on P2-type Na_0.67Fe_0.5Mn_0.5O₂ to improve the cycle and rate performance. Scanning electron microscope(SEM) and transmission electron microscope(TEM) images indicate that an insular thin layer SnO₂ is coated on the surface of Na_0.67Fe_0.5Mn_0.5O₂ after medication. The coating layer of SnO₂ can protect Na_0.67Fe_0.5Mn_0.5O₂ from corrosion by electrolyte and the cycle performance is well enhanced. After 100 cycles at 1 C rate(1 C=200 mA/g), the capacity of SnO₂ modified Na_0.67Fe_0.5Mn_0.5O₂ retains 83 mA·h/g(64% to the initial capacity), while the capacity for the pristine Na_0.67Fe_0.5Mn_0.5O₂ is only 38 mA·h/g(33.5% to the initial capacity). X-Ray photoelectron spectroscopy reveals that the ratio of Mn⁴⁺ increases after SnO₂ modification, leading to less oxygen vacancy and expanded lattice. As a result, the capacity of Na_0.67Fe_0.5Mn_0.5O₂ increases from 178 mA·h/g to 197 mA·h/g after SnO₂ modification. Furthermore, the rate performance of Na_0.67Fe_0.5Mn_0.5O₂ is enhanced with SnO₂ coating, due to high electronic conductivity of SnO₂ and expanded lattice after SnO₂ coating. The capacity of SnO₂ modified Na_0.67Fe_0.5Mn_0.5O₂ at 5 C increases from 21 mA·h/g(pristine Na_0.67Fe_0.5Mn_0.5O₂) to 35 mA·h/g.     

Cu/Co/Mn基氧载体释氧动力学及机理研究

以溶胶凝胶法制备了CuO/CuAl₂O₄、Co₃O₄/CoAl₂O₄以及Mn₂O₃/Al₂O₃氧载体,在流化床反应器中CO₂气氛下研究了不同温度下氧载体释氧特性,并通过分析得到各氧载体的释氧动力学机理函数、活化能及指前因子等重要参数。释氧过程中,氧载体CuO/CuAl₂O₄中CuO、CuAl₂O₄均为活性相,释氧后转化为Cu₂O及CuAlO₂,而Co₃O₄/CoAl₂O₄及Mn₂O₃/Al₂O₃中CoAl₂O₄和Al₂O₃均为惰性相,仅有Co₃O₄和Mn₂O₃参与释氧并分别转化为CoO和Mn₃O₄。三种氧载体的释氧过程均可由成核-核生长机理描述,释氧初期氧载体经化学反应形成新的活性核心,随后活性核心聚集形成还原态的氧载体团簇。各氧载体释氧的机理函数G(x)有不同的表达式,CuO/CuAl₂O₄、Co₃O₄/CoAl₂O₄、Mn₂O₃/Al₂O₃释氧的活化能E分别为226.37、130.06和65.90 kJ/mol,相对应的指前因子A分别为2.99×10⁶、4.96×10³和27.37 s^-1。     

Thermogravimetric study on perovskite-like oxygen permeation ceramic membranes

The oxygen permeation properties of mixed-conducting ceramics SrFeCo_0.5O_3−δ (SFCO), Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCFO), La_0.2Sr_0.8Co_0.8Fe_0.2O_3−δ (LSCFO) and Ba_0.95Ca_0.05Co_0.8Fe_0.2O_3−δ (BCCFO) were studied by thermogravimetric method in the temperature range 600–900 °C. The results show that the oxygen adsorption rate constants k_a of all material are larger than oxygen desorption rate constants k_d and both k_a and k_d are not strongly dependent on temperature in the studied temperature range. The oxygen vacancy contents δ(N₂) and δ(O₂) in nitrogen and oxygen and their difference Δδ = δ(N₂) − δ(O₂) play an important role in determining the temperature behavior of oxygen permeation flux J_O2.     

Ag/Yb掺杂对Ca3Co3.9Cu0.1O9-δ热电性能的影响

采用溶胶凝胶及冷压方法, 通过在Ca₃Co_3.9Cu_0.1O_9-δ体系中引入不同量的Ag⁺或Yb³⁺离子来调控体系的热电性能, 制备了可在300~880 K下稳定存在且热电性能优良的陶瓷材料Ca_3-xAg_xCo_3.9Cu_0.1O_9-δ(x=0.1, 0.15, 0.2, 0.3)和Ca_3-yYb_yCo_3.9Cu_0.1O_9-δ(y=0.05, 0.1, 0.2, 0.3). 通过X射线衍射(XRD)和扫描电子显微镜(SEM)等测试手段对产物进行了表征, 结果显示所制备的样品纯度较高, 晶粒均匀, 晶粒间较致密. 适量的Ag⁺, Yb³⁺离子取代Ca²⁺离子固溶到晶体中使制备的双掺杂材料晶胞体积发生了变化, 但并未引起晶体对称结构的变化. 电阻率和Seebeck系数的表征结果说明双掺杂优化了载流子的浓度, 随着温度的升高电阻率不断减小, Seebeck系数不断增大. 经过计算可知Seebeck系数的增大还有电子有效质量的贡献. 热导率表征结果显示双掺杂体系的热导率随着温度的升高而减小, 其中声子热导依然起主要作用, 这与单掺杂体系的结果一致. 随着温度的升高, 双掺杂样品Ca_2.7Ag_0.3Co_3.9Cu_0.1O_9-δ在880 K下ZT值达到最大, 为0.2.     

Synthesis and Ferrimagnetic Behaviour of Mn Doped Rare Earth Iron Garnets

Rare earth iron garnets R₃Fe_5–xMn_xO₁₂(R=Pr, Nd, Sm, Eu) were prepared through mild hydrothermal method. The initial alkalinity of solutions was thought to play an important role in governing the content of Mn. The effect of substitution Fe³⁺ ions by Mn³⁺ ions on magnetic properties was investigated. The saturation magnetizations of Mn-doped samples are larger than that of corresponding parent compounds due to the moment of Mn³⁺ ion being smaller than that of Fe³⁺. It is clearly shown that incorporation of Mn³⁺ gives rise to significant variations in the Curie temperature. With increasing of Mn content x, Curie temperatures reduced sharply for the garnets, which could be explained by the exchange interaction between a-d Fe³⁺ being reduced in these compounds.     

煤和生物质化学链气化中铜基载氧体与灰分的碳热反应研究

从反应温度、灰的种类和灰的比例三个方面,对煤和生物质化学链气化过程中铜基载氧体与灰中矿物的碳热反应过程进行了研究;通过往复切换固定床的氧化还原气氛模拟化学链气化的循环过程,利用XRD和SEM-EDS等表征手段并结合热力学计算对产物进行分析。结果表明,灰中Fe_2O_3和Al_2O_3易与CuO/Cu_2O反应形成CuAl_2O_4、Cu_2Fe_2O_4和CuFe_2O_4等尖晶石结构的物质,而CaO能够通过阻碍Cu-Al和Cu-Si复合化合物的形成来缓解铜基载氧体的烧结。温度升高促使CuO极易与CaSiO_3和MgSiO_3等硅酸盐矿物发生固-固反应,生成CaCuSi_2O_6和CuMgSi_2O_6等而降低铜基载氧体的反应活性。随着灰分比例的增加,Ca~(2+)和Fe~(3+)等离子富集所生成的Ca_2Fe_9O_(13)易与SiO_2发生反应生成高熔点的CaFeSi_2O_6三相共熔体,与铜基载氧体共熔并覆盖在载氧体表面,阻碍其释氧性能。     

Facial Preparation of Magnetic Lipase as Efficient Biocatalyst to Resolute Esters Enantioselectively

Magnetic lipase was prepared by a facial and cost-effective method. Lipase from Pseudomonase cepacia was covalently linked to Fe₃O₄ nanoparticles, which were produced by co-precipitating Fe²⁺ and Fe³⁺ ions in ammonia solution and subsequent coating with 3,4-dihydroxylaldehyde. Magnetic Fe₃O₄ nanoparticles modified with 3,4-dihydroxylaldehyde bonded lipase efficiently(47 mg/g). The resulting magnetic-lipase is active(0.68 μmol·min^-1·mg^-1) and enantioselective(e.e. of the product >98%) in the hydrolysis of racemic 1-phenylethyl acetate. Furthermore, as a heterogeneous catalyst, the magnetic-lipase can be magnetically recycled, and a retained activity of 48% was obtained even after 6 cycles.     

A ternary phase diagram of the Mn–Te–O system at 950 K

A ternary phase diagram of the Mn–Te–O system at 950 K has been established in the composition range in and around the MnO–TeO₂ pseudo binary line. Various preparation methods were employed to confirm the co-existence of different ternary phases. The results of these phase equilibration studies were revalidated by the invariancy of partial pressures at constant temperature during high temperature mass spectrometric vaporization experiments. The following three-phase regions have been identified: MnO+Mn₃O₄+Mn₆Te₅O₁₆ (phase region 1; PH1), Mn₃O₄+Mn₆Te₅O₁₆+MnTeO₃ (phase region 2; PH2), Mn₃O₄+MnTeO₃+Mn₃TeO₆ (phase region 3; PH3), and MnTeO₃+Mn₂Te₃O₈+Mn₃TeO₆ (phase region 4; PH4). The complex nature of the Mn–Te–O ternary system was revealed by the interesting results obtained by us with regard to preparation of samples and mass spectrometric vaporization experiments.     

Coordination properties of 1-allyl-2-methylimidazole relative to some metal ions in the solid state and aqueous solution

Cobalt(II) and copper(II) complexes with 1-allyl-2-methylimidazole (L), of general formula [ML₂(NO₃)₂], have been prepared in the solid state. The compounds were characterised by structural, spectroscopic and magnetic measurements. The metal ions in both six coordinate complexes are surrounded by two nitrogen atoms of the imidazole rings and four oxygen atoms of the chelating nitrato group (the CoN₂O₄ and CuN₂O₄ chromophores). The structure of both chromophores is described by a very distorted tetragonal bipyramid. The formation of successive complexes of the azole with Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Cd²⁺ in aqueous solution was followed potentiometrically. An irregularity in the K_n constants of successive Co²⁺ and Zn²⁺ complexes suggests a change in the coordination sphere of the central ions from octahedral to tetrahedral. With the Co²⁺–1-allyl-2-methylimidazole system, the change has been proven by inspection of the visible absorption spectra.     

Kinetics and mechanisms of the reduction of Cu0.5Zn0.5Fe2O4 with hydrogen at 400–600 °C for the production of metallic nanoparticles

Ferrites have continued to attract attention over years. As magnetic materials, ferrites cannot be replaced by any other magnetic material because they are relatively inexpensive, stable and have a wide range of technological applications in transformer core, high quality filters, high frequency circuits and operating devices. Nanocrystallite sizes of Cu_0.5 Zn_0.5Fe₂O₄ with 25 nm have been obtained by hydrothermal route. Cu_0.5Zn_0.5Fe₂O₄ powder was isothermally reduced in H₂ flow at 400–600 °C. The reduction behavior of the produced powder as well as the influence of reduction temperature on the structural characteristics of the products was extensively studied. Microstructure of partially and completely reduced samples was investigated and the activation energy values were calculated from Arrhenius equation. The activation energy for nanocrystallite Cu_0.5 Zn_0.5Fe₂O₄ reduced at the initial stage was found to be 37.4 kJ/mole, while that at the final stage is 14 kJ/mole. The approved mathematical formulations for the different crystallite sizes gas solid reaction were applied and it was found that at the final stages the reaction is controlled by the gaseous diffusion while the combined gaseous diffusion and interfacial chemical reaction is the rate controlling mechanisms at the initial stages. The reduction process produce nanoparticles metallic phases of iron, copper and zinc, which have ball and fibers shapes.     

Effective Removal of Tetracycline by Using Biochar Supported Fe3O4 as a UV-Fenton Catalyst

Novel Fe3O4-decorate hierarchical porous carbon skeleton derived from maize straw(Fe3O4@MSC)was synthesized by a facile co-precipitation process and a calcination process,which was developed as a UV assisted heterogeneous Fenton-like catalyst.The as-synthesized catalysts were characterized via X-ray powder diffraction(XRD), scanning electron microscope(SEM),transmission electron microscope(TEM),Brunauer-Emmet-Teller(BET)and vibrating sample magnetometer(VSM)at room temperature.The morphology and structure analysis revealed that the as-prepared Fe3O4@MSC retained the original pore morphology of the maize straw material.The non-uniform poly- hedral Fe3O4 grew on the whole surface of the MSC,which reduced the aggragation of Fe3O4 and provided more active sites to strengthen the UV-assisted Fenton-like reaction.As a result,the tetracycline(TC)degradation efficiency after 40 min reaction and total organic carbon(TOC)removal efficiency after 2 h reaction of Fe3O4@MSC catalyzing UV-Fenton system reached 99.2%and 72.1%,respectively,which were more substantial than those of Fe3O4@MSC/H2O2(31.5%and 2%),UV/H2O2 system(68%and 23.4%)and UV/Fe3O4/H2O2(80% and 37.5%).The electron spin resonance(ESR)results showed that the ·OH played an important role in the catalytic reaction.A possible degradation pathway of TC was proposed on the basis of the identified intermediates.Overall,the UV assisted heterogeneous Fenton-like process in Fe3O4@MSC improved the cycle of Fe^3+/Fe^2+ and activated the interfacial catalytic site,which eventually realized the enhancement of degradation and mineralization to tetracycline.     

煅烧温度对Mn/TiO_2催化剂催化NO氧化活性的影响

以浸渍在二氧化钛上的锰基催化剂为对象,研究了制备过程中煅烧温度对锰基催化剂催化NO氧化活性的影响。结果表明,较低的煅烧温度有利于提高Mn/TiO2催化剂对于NO氧化的催化效率。利用X射线粉末衍射(XRD)、场发射扫描电子显微镜(FESEM)、X射线光电子能谱(XPS)、H2程序升温还原(H2-TPR)和O2程序升温脱附(O2-TPD)等表征手段研究了煅烧温度影响Mn/TiO2催化剂催化活性的作用机理。结果表明,在NO氧化过程中发挥主要作用的是Mn2O3,较低的煅烧温度有利于提高Mn2O3在锰氧化物中所占的比例,同时增加锰氧化物在载体表面的分散度,从而改善催化剂活性;当煅烧温度超过500℃时,催化剂会发生烧结,载体TiO2的晶形开始由锐钛型向金红石型转变,Mn2O3也从非晶相向晶相转变。H2-TPR和O2-TPD测试结果表明,低温煅烧有利于提高催化剂的还原性能和表面化学吸附态O2-的脱附性能,良好的还原性能和脱附性能的相互作用使催化剂表面的氧有较好的移动能力,从而促进催化剂的活性。     

Influence of the size of doping ion on phase stability and oxygen permeability of SrCo0.8Fe0.2O3−δ oxide

The compounds of SrCo_0.8Fe_0.2O_3−δ (SCF) doped with Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Ti⁴⁺ and Zr⁴⁺ are synthesized by conventional solid-state reaction. The phase stabilities and oxygen permeabilites of these synthesized oxides are investigated. It is found that the doping Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ totally dissolve into the SCF unit cell, while SrTiO₃ and SrZrO₃ phases form when SCF is doped with Ti⁴⁺ and Zr⁴⁺, respectively. A possible mechanism of the doping behavior is proposed to interpret the structure transformation of the SCF unit cell. Phase stability increases directly with the size of the doping ion when SCF is doped with the ions in the same group. However, the influence of the size of the doping ion on the oxygen permeation behavior is negligible for the membranes doped with the ions in the same group.     

沉淀剂对铜锰复合氧化物变换催化剂构效的影响

以CuSO4.5H2O和MnSO4.H2O为原料,KOH和NaOH为沉淀剂制备了铜锰复合氧化物,考察了其变换反应催化性能,利用XRD、低温氮气吸附法、TG、H2-TPR等对所合成样品进行了表征。以KOH和NaOH为沉淀剂所得沉淀终产物的物相组成和织构明显不同,分别为层状结构碱式硫酸铜Cu4SO4(OH)6.H2O及无定形锰氧化物和Cu2+1O和Mn3O4混合物。两种物相组成和织构完全不同的沉淀终产物焙烧后都生成Cu1.5Mn1.5O4固熔体,在变换反应条件下均转化为Cu和MnO,但其催化性能却有明显差异。以NaOH为沉淀剂,得到以Cu2+1O和Mn3O4复合体为主的沉淀终产物,焙烧及还原后保持了较高的织构稳定性,提高了样品的活性和热稳定性。而以KOH为沉淀剂得到以层状结构碱式硫酸铜Cu4SO4(OH)6.H2O和无定形锰氧化物为主的沉淀终产物,在焙烧过程发生的演变极其复杂,削弱了铜锰组分协同效应,造成其活性和热稳定性极差。研究结果表明,NaOH作沉淀剂所制备样品的织构稳定性、催化活性显著高于以KOH作沉淀剂所制备样品,且热稳定性良好。