中空介孔碳化钨微球载钯催化剂对甲酸电催化性能

采用喷雾干燥法和还原炭化处理制备具有中空介孔结构的碳化钨钴复合粉(HTCCS),其中,钴的质量含量为6%。在碳化钨钴复合粉表面的钴和氯化钯发生置换反应,得到纳米Pd/WC复合催化剂。采用X射线粉末衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)对样品的形貌和晶型结构进行了表征。结果表明, 5.0-6.0nm钯纳米粒子取代钴均匀分布在碳化钨微球表面。采用循环伏安和计时电流法研究了在酸性溶液中Pd/WC催化剂对甲酸的电催化氧化性能,结果表明,Pd/WC催化剂比Pd/C催化剂对甲酸呈现出更高的电催化氧化活性和稳定性。     

中空介孔碳化钨微球载钯催化剂对甲酸电催化性能（英文）

采用喷雾干燥法和还原炭化处理制备具有中空介孔结构的碳化钨钴复合粉(HTCCS),其中,钴的质量含量为6%。在碳化钨钴复合粉表面的钴和氯化钯发生置换反应,得到纳米Pd/WC复合催化剂。采用X射线粉末衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)对样品的形貌和晶型结构进行了表征。结果表明,5.0-6.0 nm钯纳米粒子取代钴均匀分布在碳化钨微球表面。采用循环伏安和计时电流法研究了在酸性溶液中Pd/WC催化剂对甲酸的电催化氧化性能,结果表明,Pd/WC催化剂比Pd/C催化剂对甲酸呈现出更高的电催化氧化活性和稳定性。     

负载四氧化三钴纳米粒子的介孔碳基氧还原反应催化剂的电化学性能分析

采用软模板法合成介孔碳材料前驱体,引入钴盐,通过高温煅烧等步骤得到负载钴氧化物纳米粒子的介孔碳基催化剂。通过X-射线衍射(XRD)、透射电子显微镜(TEM)、X-射线光电子能谱(XPS)、循环伏安法(CV)和线性扫描伏安法(LSV)等测试方法对所制备的催化剂的成分、结构和电化学性能进行了表征。结果表明,钴以四氧化三钴的形式成功负载于介孔碳材料基底,所得催化剂在碱性环境中表现出与商业Pt/C催化剂相当的氧还原催化活性,并且其稳定性优于商业Pt/C催化剂,有望取代造价高昂的Pt/C基催化剂,成为新型燃料电池阴极催化材料。     

含铜有序介孔Cu-KIT-6的合成及其苯乙烯环氧化催化性能:pH值的影响（英文）

苯乙烯侧链C=C的选择性氧化一直是烯烃环氧化研究领域关注的热点之一.近几十年来,苯乙烯环氧化研究主要集中于多相过渡金属催化剂的开发与应用;以铜为主要活性物种的催化剂因具有较高的环氧苯乙烷选择性而备受瞩目.然而,采用pH调节法将铜离子引入三维六方介孔材料KIT-6阵列尚未见报道,尤其是pH值对合成材料的形貌、结构以及催化活性的影响尚未可知.基于此,本文采用pH调节法合成了铜嵌入KIT-6介孔材料Cu-KIT-6x(x代表初始溶胶的pH值,x=1.43,2.27,3.78,3.97,4.24,6.62),并将其应用于苯乙烯环氧化反应.采用X射线粉末衍射、氮气吸附脱附、透射电子显微镜以及X射线光电子能谱等手段对Cu-KIT-6x的表面结构及形貌进行了细致表征.结果表明,随着pH的变化,Cu-KIT-6x催化剂的物理特性、表面结构尤其是铜物种种类和含量均变化较大.较低的pH导致铜物种主要以Cu~(2+)形式存在,难以引入到KIT-6骨架中,且不利于介孔材料的合成,最终导致产生无序介孔结构.当pH增大到3.78时,约有4.6 wt%的Cu(Ⅱ)以–Cu–O–Si–形式成功引入KIT-6骨架中,获得了具有较高比表面积且有序的孔结构.此外,由于Cu~(2+)的引入,骨架内部分Si~(4+)被取代,促使Cu-KIT-6_(3.78)拥有可与载体KIT-6相媲美的大孔径.然而,当pH继续增大时,过量的Cu~(2+)从KIT-6骨架中析出,以CuO形式存在于载体表面,从而导致Cu-KIT-6的孔径逐渐增大;同时NaOH对三维立方介孔结构的破坏,使得介孔结构坍塌及比表面积显著降低.以苯乙烯环氧化反应评价了Cu-KIT-6x系列催化剂的催化活性.当以叔丁基过氧化氢为氧化剂,乙腈为溶剂,在70 ℃反应6 h后,Cu-KIT-6_(3.78)表现出最优的苯乙烯转化率(43.5%)及环氧苯乙烷选择性(86.6%).使用4次后,Cu-KIT-6_(3.78)展示了稳定的苯乙烯转化率、环氧苯乙烷选择性及有序的孔结构,充分表明其具有出色的稳定性.各表征结果揭示了在适宜pH下合成的Cu-KIT-6_(3.78)催化剂具有较高的铜含量、有序的立方Ia3d介孔结构及合适的结构参数,因而在苯乙烯环氧化反应中表现优异活性和良好稳定性.     

不对称配位磷酸钴铵增强电催化水氧化反应性能（英文）

钴基材料被认为是有望替代贵金属材料的电催化水氧化反应催化剂之一.研究发现,高活性的钴基催化剂常发生表面重构行为,深入研究表面重构行为对于阐明真实的催化活性位点和指导合成高性能的电催化剂至关重要.但是受到复杂的催化剂结构以及多种性能影响因素限制,钴基材料的配位结构对表面重构和电催化水氧化性能影响仍不清晰.基于此,本文设计了具有配位对称结构和不对称结构的两种磷酸钴基材料用于电催化水氧化反应,探索配位对称性对表面重构和水氧化性能的影响.本文通过调控共沉淀反应中磷酸铵的用量,合成了具有对称配位结构的磷酸钴材料和不对称配位结构的磷酸钴铵材料.采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)和物理吸附等技术表征了两种材料的物理性质.通过线性扫描法,循环伏安法和恒电位电解法等电化学方法测定两种材料的电催化水氧化活性和稳定性.采用原位电化学阻抗图谱、拉曼光谱(Raman)和XPS图分析水氧化反应中的表面重构过程.晶体结构图表明,磷酸钴材料和磷酸钴铵材料均由六配位的Co O6八面体组成.其中,磷酸钴结构中钴中心由四个水分子和两个磷酸基团或两个水分子...     

有机官能化介孔硅基材料负载纳米金催化剂的制备及其催化性能

一步合成了桥键嵌入二硫醚官能化介孔硅基材料(PMO-SBA-15),利朋介孔硅基材料孔道内表面的二硫醚基团捕获纳米金(Au)粒子的作用,获得了负载型纳米Au催化剂(Au-PMO-SBA-15).小角X射线衍射和低温N2吸附-脱附的结果表明,PMO-SBA-15和Au-PMO-SBA-15均保持典型的介孔结构;高分辨透射电镜观察到纳米Au粒子在载体孔道内分散均匀,甲均粒径为(2.2±0.2)nm.以70%的叔丁基过氧化氧水溶液为氧化剂,考察了纳米Au催化剂Au-PMO-SBA-15在苯甲醇氧化反应中的催化性能.结果表明,当反应温度为353 K、反应时间为5 h时,苯甲醇的转化率为29.1%,苯甲醛的选择性为100%,且催化剂重复使用7次其催化活性和苯甲醛选择性基奉不变.     

含铜有序介孔Cu-KIT-6的合成及其苯乙烯环氧化催化性能:pH值的影响

苯乙烯侧链C=C的选择性氧化一直是烯烃环氧化研究领域关注的热点之一.近几十年来,苯乙烯环氧化研究主要集中于多相过渡金属催化剂的开发与应用;以铜为主要活性物种的催化剂因具有较高的环氧苯乙烷选择性而备受瞩目.然而,采用pH调节法将铜离子引入三维六方介孔材料KIT-6阵列尚未见报道,尤其是pH值对合成材料的形貌、结构以及催化活性的影响尚未可知.基于此,本文采用pH调节法合成了铜嵌入KIT-6介孔材料Cu-KIT-6x(x代表初始溶胶的pH值,x=1.43,2.27,3.78,3.97,4.24,6.62),并将其应用于苯乙烯环氧化反应.采用X射线粉末衍射、氮气吸附脱附、透射电子显微镜以及X射线光电子能谱等手段对Cu-KIT-6x的表面结构及形貌进行了细致表征.结果表明,随着pH的变化,Cu-KIT-6x催化剂的物理特性、表面结构尤其是铜物种种类和含量均变化较大.较低的pH导致铜物种主要以Cu2+形式存在,难以引入到KIT-6骨架中,且不利于介孔材料的合成,最终导致产生无序介孔结构.当pH增大到3.78时,约有4.6 wt%的Cu(II)以?Cu?O?Si?形式成功引入KIT-6骨架中,获得了具有较高比表面积且有序的孔结构.此外,由于Cu2+的引入,骨架内部分Si4+被取代,促使Cu-KIT-63.78拥有可与载体KIT-6相媲美的大孔径.然而,当pH继续增大时,过量的Cu2+从KIT-6骨架中析出,以CuO形式存在于载体表面,从而导致Cu-KIT-6的孔径逐渐增大;同时NaOH对三维立方介孔结构的破坏,使得介孔结构坍塌及比表面积显著降低.以苯乙烯环氧化反应评价了Cu-KIT-6x系列催化剂的催化活性.当以叔丁基过氧化氢为氧化剂,乙腈为溶剂,在70 oC反应6 h后,Cu-KIT-63.78表现出最优的苯乙烯转化率(43.5%)及环氧苯乙烷选择性(86.6%).使用4次后,Cu-KIT-63.78展示了稳定的苯乙烯转化率、环氧苯乙烷选择性及有序的孔结构,充分表明其具有出色的稳定性.各表征结果揭示了在适宜pH下合成的Cu-KIT-63.78催化剂具有较高的铜含量、有序的立方Ia3d介孔结构及合适的结构参数,因而在苯乙烯环氧化反应中表现优异活性和良好稳定性.     

介孔结构的α-FeOOH对苯酚的催化臭氧化降解

以双氧水和硫酸亚铁为原料,采用绿色简便水热法得到了高比表面的羟基氧化铁纳米催化剂,提出将α-FeOOH纳米材料用作臭氧化催化剂。X射线粉末衍射(XRD)、透射电镜(TEM)、低温氮吸附脱附表征结果证明催化剂组成为α-FeOOH,形貌为直径13～20 nm、长度70～100 nm具有介孔结构的棒状物,Brunauer-Emmett-Teller(BET)比表面积达到132 m²·g^-1,碱滴定分析表明所得催化剂的表面羟基密度高达5.484 mmol·g^-1,该纳米材料对臭氧化降解水中苯酚显示了优异的催化性能。机理研究表明,具有高比表面、高表面羟基密度以及合适的pH_pzc值的纳米α-FeOOH催化剂,在多相催化反应中促进了臭氧分子到羟基自由基的转变,从而加快了苯酚的降解。     

介孔钯-硼合金纳米颗粒的制备和甲醇氧化电催化性能北大核心CSCD

合金化可以调节贵金属纳米材料的物理化学性质,从而显著提升它们的电催化性能。尽管合金化在过去的20多年里已取得诸多成果,但是如何充分发挥纳米合金的组分优势仍需深入的探究。本研究通过一步溶液相合成法实现了类金属硼(B)合金化的钯基介孔纳米催化剂材料的合成,同时探究了B原子的组分优势和介孔形貌的结构优势在碱性介质中电化学甲醇氧化反应(MOR)的协同作用。最优PdCuB介孔纳米催化剂表现出优异的电化学MOR活性和稳定性。机理研究表明,优异的催化活性源于B原子在Pd基介孔纳米催化剂中的积极协同作用;该协同作用通过电子效应(改变Pd的表面电子结构从而减弱CO基中间体的吸附)和双功能效应(促进OH_(2)的吸附从而氧化CO基中间体)在动力学上加速了有毒CO基中间体的去除(提高甲醇氧化的决速步骤)。同时,B原子的间隙插入和介孔结构抑制了物理奥斯特瓦尔德(Ostwald)熟化过程,显著增加了催化剂的稳定性。     

CoFe2O4纳米微粒的制备及其催化性能

采用溶胶-凝胶法制备了铁酸钴纳米微粒催化剂，运用XRD、IR、TPR以及BET比表面测试等手段对所制备的样品进行了表征。研究了铁酸钴的结构和氧化还原性质，考察了铁酸钴对二氧化碳选择性氧化乙苯制苯乙烯的催化性能。结果表明：制备的铁酸钴微粒的比表面积为36.3m^2/g，晶粒大小约为30nm。在由二氧化碳选择性氧化乙苯制苯乙烯的反应中表现出较好的催化活性。     

Sol-gel synthesis of K3InF6 and structural characterization of K2InC10O10H6F9, K3InC12O14H4F18 and K3InC12O12F18

K₃InF₆ is synthesized by a sol-gel route starting from indium and potassium acetates dissolved in isopropanol in the stoichiometry 1:3, with trifluoroacetic acid as fluorinating agent. The crystal structures of the organic precursors were solved by X-ray diffraction methods on single crystals. Three organic compounds were isolated and identified: K₂InC₁₀O₁₀H₆F₉, K₃InC₁₂O₁₄H₄F₁₈ and K₃InC₁₂O₁₂F₁₈. The first one, deficient in potassium in comparison with the initial stoichiometry, is unstable. In its crystal structure, acetate as well as trifluoroacetate anions are coordinated to the indium atom. The two other precursors are obtained, respectively, by quick and slow evaporation of the solution. They correspond to the final organic compounds, which give K₃InF₆ by decomposition at high temperature. The crystal structure of K₃InC₁₂O₁₄H₄F₁₈ is characterized by complex anions [In(CF₃COO)₄(OH_x)₂]^(5−2x)− and isolated [CF₃COOH_2−x]^(x−1)− molecules with x=2 or 1, surrounded by K⁺ cations. The crystal structure of K₃InC₁₂O₁₂F₁₈ is only constituted by complex anions [In(CF₃COO)₆]³⁻ and K⁺ cations. For all these compounds, potassium cations ensure only the electroneutrality of the structure. IR spectra of K₂InC₁₀O₁₀H₆F₉ and K₃InC₁₂O₁₂F₁₈ were also performed at room temperature on pulverized crystals.     

Li2O-TiO2-SiO2-P2O5和Li2O-TiO2-Al2O3-P2O5体系锂离子固体电解质的制备及性能研究

一些具有NASICON型网格结构的固体电解质具有高的电导率和好的稳定性,NASICON的意思是Na Super Ionic Conductor[1]。当NaZr2(PO4)3中P5 被Si4 部分取代时便可以得到具有NASICON结构的Na1 xZr2SixP3-xO12体系,其具有高的钠离子电导率。然而有相同结构的Li1 xZr2SixP3-xO12体系的离子电导率却很低,这是因为Li 半径太小,而NASICON三维网格结构的离子通道太大,两者不匹配而使电导率下降[2]。但当LiZr2(PO4)3中Zr4 被离子半径小些的Ti4 取代,所得LiTi2(PO4)3的通道就与Li 半径相匹配,适合于锂离子的迁移,从而使其电导率…     

Non-centrosymmetric Ba3Ti3O6(BO3)2

The compound previously reported as Ba₂Ti₂B₂O₉ has been reformulated as Ba₃Ti₃B₂O₁₂, or Ba₃Ti₃O₆(BO₃)₂, a new barium titanium oxoborate. Small single crystals have been recovered from a melt with a composition of BaTiO₃:BaTiB₂O₆ (molar ratio) cooled between 1100°C and 850°C. The crystal structure has been determined by X-ray diffraction: hexagonal system, non-centrosymmetric space group, a=8.7377(11) Å, c=3.9147(8) Å, Z=1, wR(F²)=0.039 for 504 unique reflections. Ba₃Ti₃O₆(BO₃)₂ is isostructural with K₃Ta₃O₆(BO₃)₂. Preliminary measurements of nonlinear optical properties on microcrystalline samples show that the second harmonic generation efficiency of Ba₃Ti₃O₆(BO₃)₂ is equal to 95% of that of LiNbO₃.     

Synthesis, crystal structure, infrared and Raman spectra of Sr4Cu3(AsO4)2(AsO3OH)4·3H2O and Ba2Cu4(AsO4)2(AsO3OH)3

The two new compounds, Sr₄Cu₃(AsO₄)₂(AsO₃OH)₄·3H₂O (1) and Ba₂Cu₄(AsO₄)₂(AsO₃OH)₃(2), were synthesized under hydrothermal conditions. They represent previously unknown structure types and are the first compounds synthesized in the systems SrO/BaO-CuO-As₂O₅-H₂O. Their crystal structures were determined by single-crystal X-ray diffraction [space group C2/c, a=18.536(4) Å, b=5.179(1) Å, c=24.898(5) Å, β=93.67(3)°, V=2344.0(8) Å³, Z=4 for 1; space group P4₂/n, a=7.775(1) Å, c=13.698(3) Å, V=828.1(2) Å³, Z=2 for 2]. The crystal structure of 1 is related to a group of compounds formed by Cu²⁺-(XO₄)³⁻ layers (X=P⁵⁺, As⁵⁺) linked by M cations (M=alkali, alkaline earth, Pb²⁺, or Ag⁺) and partly by hydrogen bonds. In 1, worth mentioning is the very short hydrogen bond length, D···A=2.477(3) Å. It is one of the examples of extremely short hydrogen bonds, where the donor and acceptor are crystallographically different. Compound 2 represents a layered structure consisting of Cu₂O₈ centrosymmetric dimers crosslinked by As1φ₄ tetrahedra, where φ is O or OH, which are interconnected by Ba, As2 and hydrogen bonds to form a three-dimensional network. The layers are formed by Cu₂O₈ centrosymmetric dimers of CuO₅ edge-sharing polyhedra, crosslinked by As1O₄ tetrahedra. Vibrational spectra (FTIR and Raman) of both compounds are described. The spectroscopic manifestation of the very short hydrogen bond in 1, and ABC-like spectra in 2 were discussed.     

A new 2212-type stair like structure: Bi14Sr21Fe12O61, m=5 member of the generic [Bi2Sr3Fe2O9]m[Bi4Sr6Fe2O16] family

A new oxide, Bi₁₄Sr₂₁Fe₁₂O_61, with a layered structure derived from the 2212 modulated type structure Bi₂Sr₃Fe₂O₉, was isolated. It crystallizes in the I2 space group, with the following parameters: a=16.58(3) Å, b=5.496(1) Å, c=35.27(2) Å and β=90.62°. The single crystal X-ray structure determination, coupled with electron microscopy, shows that this ferrite is the m=5 member of the [Bi₂Sr₃Fe₂O₉]_m[Bi₄Sr₆Fe₂O₁₆] collapsed family. This new collapsed structure can be described as slices of 2212 structure of five bismuth polyhedra thick along , shifted with respect to each other and interconnected by means of [Bi₄Sr₆Fe₂O₁₆] slices. The latter are the place of numerous defects like iron or strontium for bismuth substitution; they can be correlated to intergrowth defects with other members of the family.     

Ion-beam irradiation of lanthanum compounds in the systems La2O3-Al2O3 and La2O3-TiO2

Thin crystals of La₂O₃, LaAlO₃, La_2/3TiO₃, La₂TiO₅, and La₂Ti₂O₇ have been irradiated in situ using 1 MeV Kr²⁺ ions at the Intermediate Voltage Electron Microscope-Tandem User Facility (IVEM-Tandem), Argonne National Laboratory (ANL). We observed that La₂O₃ remained crystalline to a fluence greater than 3.1×10¹⁶ ions cm⁻² at a temperature of 50 K. The four binary oxide compounds in the two systems were observed through the crystalline-amorphous transition as a function of ion fluence and temperature. Results from the ion irradiations give critical temperatures for amorphisation (T_c) of 647 K for LaAlO₃, 840 K for La₂Ti₂O₇, 865 K for La_2/3TiO₃, and 1027 K for La₂TiO₅. The T_c values observed in this study, together with previous data for Al₂O₃ and TiO₂, are discussed with reference to the melting points for the La₂O₃-Al₂O₃ and La₂O₃-TiO₂ systems and the different local environments within the four crystal structures. Results suggest that there is an observable inverse correlation between T_c and melting temperature (T_m) in the two systems. More complex relationships exist between T_c and crystal structure, with the stoichiometric perovskite LaAlO₃ being the most resistant to amorphisation.     

Raman scattering investigations on lanthanum-doped Bi4Ti3O12-SrBi4Ti4O15 intergrowth ferroelectrics

The ferroelectric ceramics of Bi₄Ti₃O₁₂, SrBi₄Ti₄O₁₅, and lanthanum-doped Bi₄Ti₃O₁₂-SrBi₄Ti₄O₁₅ were synthesized, and their Raman spectra were investigated. La-doping resulted in the enlargement of remnant polarization of Bi₄Ti₃O₁₂-SrBi₄Ti₄O₁₅. The structure of the Bi₂O₂ layers and TiO₆ octahedra of the intergrowth was found to be different from those of Bi₄Ti₃O₁₂ and SrBi₄Ti₄O₁₅. La³⁺ ions exhibit pronounced selectivity for the occupation of A site as La content is lower than 0.50, and tend to be incorporated into Bi₂O₂ layers when the La content is higher than 0.50. Lanthanum substitution brings about the structural phase transition in Bi₄Ti₃O₁₂-SrBi₄Ti₄O₁₅. The variation of ferroelectric property may be attributed to combined contribution from the decreasing of the oxygen vacancies, the relaxation of the lattice distortion, the destroying of the insulation and the space charge compensation effects of the Bi₂O₂ slabs.     

g-C_3N_4/CaTi_2O_5复合材料制备及其光催化性能

利用类石墨氮化碳(g-C_3N_4)和亚稳相钙钛氧化物(CaTi_2O_5)固相法制备C_3N_4/CaTi_2O_5复合材料。利用X射线衍射(XRD)、金相显微镜、扫描电子显微镜(SEM)及附带能谱分析仪(EDS)和N2吸附-脱附对样品的显微结构和比表面积进行检测分析,并用紫外-可见吸收光度计(UV-Vis)测试了样品的光吸收性能,研究C_3N_4与CaTi_2O_5物质的量之比(nC_3N_4/nCaTi_2O_5)对C_3N_4/CaTi_2O_5复合样品的物相结构和微观形貌的影响,同时考察C_3N_4/CaTi_2O_5复合样品在可见光照射下光催化降解罗丹明染料效果。实验结果表明:相比纯C_3N_4和CaTi_2O_5样品,C_3N_4/CaTi_2O_5复合样品在可见光下具有较高的光催化性能,随着nC_3N_4/nCaTi_2O_5增加,样品的光催化降解率随之增加而后降低,当nC_3N_4/nCaTi_2O_5=1∶1时,样品的光催化降解率达到最大值99.5%,并且循环重复利用5次后,样品的光催化剂降解率仍几乎保持不变。复合样品光催化性能提高主要归因于复合能级结构有效地抑制了电子和空穴复合所致。     

g-C3N4/CaTi2O5复合材料制备及其光催化性能

利用类石墨氮化碳（g-C₃N₄）和亚稳相钙钛氧化物（CaTi₂O₅）固相法制备C₃N₄/CaTi₂O₅复合材料。利用X射线衍射（XRD）、金相显微镜、扫描电子显微镜（SEM）及附带能谱分析仪（EDS）和N₂吸附-脱附对样品的显微结构和比表面积进行检测分析,并用紫外-可见吸收光度计（UV-Vis）测试了样品的光吸收性能,研究C₃N₄与CaTi₂O₅物质的量之比（n_C3N4/nCaTi₂O₅）对C₃N₄/CaTi₂O₅复合样品的物相结构和微观形貌的影响,同时考察C₃N₄/CaTi₂O₅复合样品在可见光照射下光催化降解罗丹明染料效果。实验结果表明：相比纯C₃N₄和CaTi₂O₅样品,C₃N₄/CaTi₂O₅复合样品在可见光下具有较高的光催化性能,随着n_C3N4/nCaTi₂O₅增加,样品的光催化降解率随之增加而后降低,当n_C3N4/nCaTi₂O₅=1：1时,样品的光催化降解率达到最大值99.5%,并且循环重复利用5次后,样品的光催化剂降解率仍几乎保持不变。复合样品光催化性能提高主要归因于复合能级结构有效地抑制了电子和空穴复合所致。     

Magnetic diphase nanostructure of ZnFe2O4/γ-Fe2O3

Magnetic diphase nanostructures of ZnFe₂O₄/γ-Fe₂O₃ were synthesized by a solvothermal method. The formation reactions were optimized by tuning the initial molar ratios of Fe/Zn. All samples were characterized by X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, and Raman spectra. It is found that when the initial molar ratio of Fe/Zn is larger than 2, a diphase magnetic nanostructure of ZnFe₂O₄/γ-Fe₂O₃ was formed, in which the presence of ZnFe₂O₄ enhanced the thermal stability of γ-Fe₂O₃. Further increasing the initial molar ratio of Fe/Zn larger than 6 destabilized the diphase nanostructure and yielded traces of secondary phase α-Fe₂O₃. The grain surfaces of diphase nanostructure exhibited a spin-glass-like structure. At room temperature, all diphase nanostructures are superparamagnetic with saturation magnetization being increased with γ-Fe₂O₃ content.