Fe3O4纳米催化剂的制备及其F-T合成性能研究

基于溶剂热合成体系,制备了不同形貌的Fe₃O₄微球和纳米片催化剂,考察了水热合成条件对Fe₃O₄晶粒形貌的影响,并研究了Fe₃O₄纳米催化剂的费托合成(F-T)性能。结果表明,成核和晶体生长速率是控制Fe₃O₄晶体形貌的关键。与传统的沉淀铁催化剂相比,Fe₃O₄纳米催化剂更容易还原和向活性相转变,因此,具有更高的F-T反应活性、低碳烯烃选择性及C₅₊选择性;Fe₃O₄微球催化剂比纳米片催化剂更易维晶粒的稳定,具有更高的反应活性和稳定性。     

配位-氧化聚合-水热法制备聚苯胺/CoFe_2O_4纳米复合物及其微波吸收性能

采用"配位-氧化聚合-水热法"制备了本征态聚苯胺/CoFe2O4二元纳米复合物,再以磺基水杨酸掺杂获得聚苯胺/CoFe2O4电磁复合物.考察了反应物配比及掺杂酸浓度对产物电磁性能的影响.通过透射电子显微镜(TEM)、X射线衍射(XRD)、红外光谱(FTIR)及电磁测量等手段对聚苯胺/CoFe2O4的形貌、结构及性能进行了表征.结果表明,复合物呈现多级结构,其中CoFe2O4为立方体状,平均粒径小于20 nm.当CoFe2O4的质量分数为8.86%时,复合物的电导率约为0.43 S/cm;当聚苯胺/CoFe2O4复合物厚度为2 mm时,在16.01 GHz处最大反射损耗为-16.71 dB,小于-10 dB的带宽达4.68 GHz;而当聚苯胺/CoFe2O4复合物厚度为3.2 mm时,在9.23 GHz处最大反射损耗达-51.81 dB,小于-10 dB的带宽为3.69 GHz,表明具有良好的吸波性能.     

铁酸镍/碳复合中空多壳层结构的制备及吸波性能

采用次序模板法合成了单、双壳层的中空铁酸镍(NiFe₂O₄)材料,通过改变前驱体溶液组成及煅烧条件等因素实现了对产物形貌的调控.在中空NiFe₂O₄颗粒表面原位包覆聚多巴胺,再经过碳化处理,制备了具有中空多壳层结构(HoMS)的NiFe₂O₄/C复合吸波材料;考察了其电磁参数,计算了其吸波性能,分析了不同复合结构对性能的影响.结果表明,中空多壳层结构能够显著降低材料的密度,而碳薄层不仅能够改善其阻抗匹配性,而且提升了材料的反射损耗性能.其中,双壳层NiFe₂O₄/C复合物的吸波性能最佳,当样品厚度为3.5 mm时,材料在8.44 GHz处反射损失最小,为-32.35 dB;当样品厚度为2.0 mm时,材料在14.01～17.69 GHz范围内反射损耗小于-10 d B,有效吸收频宽为3.68 GHz.这些优异性能主要源于独特的中空多壳层结构增加了电磁波多次反射/散射的概率,提供了更多的界面极化,实现了电磁波的快速...     

Fe3O4和Zn2+掺杂型Zn1-xFe2+xO4纳米晶的溶剂热合成和电磁性能

利用溶剂热法, 在醋酸钠静电保护剂的辅助下, 成功制备出Fe₃O₄和Zn²⁺掺杂型Zn_0.07Fe_2.93O₄纳米晶. 利用X射线衍射仪和扫描电子显微镜等对样品的晶体结构、粒径、形貌和化学组成进行了分析. 结果表明, 所得纳米晶的粒径均匀, 形貌为球形, 分散度好; Zn_0.07Fe_2.93O₄纳米晶的平均粒径(70 nm)明显小于Fe₃O₄(170 nm). 磁性能测量结果表明, 室温下Zn_0.07Fe_2.93O₄的饱和磁化强度(54.2 A·m²·kg^-1)小于Fe₃O₄ (81.6 A·m²·kg^-1). 利用矢量网络分析仪对样品的电磁性能和吸波性能进行了研究. 结果表明, Zn²⁺掺杂型Zn_0.07Fe_2.93O₄纳米晶的吸波性能优于Fe₃O₄, 前者的最大吸收峰(-19.3 dB)大于后者(-9.8 dB), 且吸收峰低于-10 dB的峰宽达2.5 GHz.     

多孔羰基铁/CoFe2O4/聚苯胺复合材料的制备及吸波机理

通过金属点蚀技术制备了表面多孔形貌的羰基铁粉（PCIP）,并采用共沉淀及原位聚合方法,将CoFe₂O₄与聚苯胺（PANI）负载于多孔羰基铁表面,得到具有电磁吸收性能的PCIP/CoFe₂O₄/PANI复合材料.通过扫描电子显微镜（SEM）、X射线衍射仪（XRD）、傅里叶变换红外光谱仪（FTIR）、热重分析仪（TGA）及矢量网络分析仪（VNA）等对复合材料的形貌、成分和吸波性能进行了研究.结果表明,CoFe₂O₄/PANI团聚于PCIP表面,显著提升了复合材料电损耗能力,促进了低频电磁波的1/4波长干涉相消.当苯胺添加量为0.5 mL,复合材料在频率为5.7 GHz时,反射损耗达到-22.9 dB,低频吸波性能得到大幅提升.利用1/4波长干涉相消理论及电磁波界面反射模型对复合材料低频吸波性能提升的内在原因进行了分析.     

SiO2@Fe2O3核-壳结构催化剂的制备及表征

采用优化的Stöber法制备了平均粒径为230 nm的单分散球形SiO₂颗粒,并以此为内核,通过水解沉积法制备了不同壳层厚度的核-壳结构SiO₂@Fe₂O₃催化剂。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、N₂物理吸附和X射线衍射分析(XRD)等手段对催化剂进行表征,探讨了不同制备条件对SiO₂@Fe₂O₃催化剂形貌的影响。结果表明,通过水解沉积法制备的SiO₂@Fe₂O₃催化剂具有明显的核-壳结构,并且保持了原始SiO₂核的球形形貌,Fe₂O₃纳米粒子通过-OH的氢键作用连接在SiO₂表面,形成了2~10 nm厚的Fe₂O₃均匀连续包覆层。     

锂锌铁氧体微纳米纤维的电纺制备及吸波性能

采用静电纺丝技术结合后续热处理制备了尖晶石型Li_0.35Zn_0.3Fe_2.35O₄微纳米纤维. 利用差示扫描量热(DSC)-热重分析(TGA)、 傅里叶变换红外光谱(FTIR)、 X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)等手段研究了煅烧温度(700, 800, 900, 1000 ℃)对产物物相和形貌的影响; 利用矢量网络分析仪分析了纤维状产物的吸波性能. 研究结果表明, Li_0.35Zn_0.3Fe_2.35O₄在700 ℃及以上温度煅烧后可生成单一尖晶石结构. 随着煅烧温度的升高, 产物依次呈现出微纳米纤维状、 三维网络状、 竹节状和颗粒状的微观形貌. 随着匹配厚度增加, 微纳米纤维状Li_0.35Zn_0.3Fe_2.35O₄的最低反射率向低频移动, 在8 GHz以下的最佳匹配厚度为6 mm, 在此厚度下吸波性能优良, 最低反射率为-26 dB, 对应的吸收频率为5.0 GHz, 低于-10 dB的吸收频带为4.0~8.0 GHz, 带宽为4 GHz.     

Bi2Ti2O7/TiO2/Bi4Ti3O12多异质结的构筑及其增强的可见光催化性能

以静电纺丝技术制备的TiO₂纳米纤维为基质,硝酸铋为铋源,KOH为矿化剂,成功制备了多异质结Bi₂Ti₂O₇/TiO₂/Bi₄Ti₃O₁₂复合纳米纤维光催化剂。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外可见漫反射光谱(UV-Vis DRS)等一系列表征,对其物相组成、微观形貌和光学性质等进行分析。结果表明：TiO₂纳米纤维的介入,将Ⅰ型异质结Bi₂Ti₂O₇/Bi₄Ti₃O₁₂分离为2个Ⅱ型异质结Bi₂Ti₂O₇/TiO₂和Bi₄Ti₃O₁₂/TiO₂。Bi₂     

基于Fe3O4@SiO2@Ag/GCE传感器检测土霉素

合成了具有核壳结构的Fe₃O₄@SiO₂纳米复合材料,在Fe₃O₄@SiO₂表面负载银纳米离子,制备了一种新型的Fe₃O₄@SiO₂@Ag复合材料,并采用玻碳电极(GCE)构建Fe₃O₄@SiO₂@Ag/GCE传感器,对土霉素(OTC)进行定量检测。优化了电解质溶液的种类和pH,Fe₃O₄@SiO₂@Ag用量以及富集时间和富集电位等实验条件。在最佳条件下,OTC浓度(c)与峰电流(I_p)在0.01～120μmol/L范围内呈线性关系,线性方程为I_p=0.9307c-0.0033,线性相关系数R²=0.9986,检出限为8.2 nmol/L。该传感器对牛奶中OTC的检测结果与国标法结果一致。     

nFe3+/nSr2+和nOH-/nNO3-对锶铁氧体纳米片结构及磁性能的影响

采用改进的水热法成功合成了单分散的纯相锶铁氧体纳米片。借助DLS、XRD、FTIR、SEM、EDS和VSM等分析测试手段对SrFe₁₂O₁₉铁氧体粉体的粒度、结构、形貌和磁性能进行表征。研究结果表明,在240℃保温5 h,物质的量之比n_Fe³⁺/n_Sr²⁺(R_F/S)和n_OH^-/n_NO^-(R_O/N)分别为5和2时,所得产物为单分散的纯相六角SrFe₁₂O₁₉铁氧体纳米片。随着R_F/S和R_O/N的变化,合成样品中有少量SrCO₃和Fe₂O₃杂相存在,这主要与反应条件和离子比例有关。磁性能测试结果显示,所得纯相的六角SrF₁₂O₁₉铁氧体纳米片具有优异的磁性能,其饱和磁化强度和矫顽力分别达到60.91 emu·g^-1和94.83 kA·m^-1,使其在医疗、催化和生物等高技术领域具有潜在的应用。     

多孔羰基铁/SiO2/聚吡咯核壳结构复合材料的制备及电磁特性

首先对羰基铁进行点腐蚀得到多孔羰基铁,然后采用St?ber法和原位聚合法将SiO_2和导电高分子聚吡咯包覆在多孔羰基铁表面,制备多孔羰基铁/SiO_2/聚吡咯电磁复合吸波材料。采用XRD、SEM、TEM、FT-IR对样品结构、微观形貌进行了表征,在网络分析仪中采用同轴法测试样品电磁参数,并根据传输线理论研究了2~18 GHz微波频段内吡咯含量及涂层厚度对样品吸波性能的影响。实验结果表明:制备的多孔羰基铁/SiO_2/聚吡咯复合电磁吸波材料具有核壳结构;随着吡咯加入量的增加,吸波材料吸收峰逐渐向低频方向移动;当涂层厚度为3.5 mm、吡咯加入量为6%(w/w)时,在9.44~17.56 GHz范围内反射率均低于-10 d B,频带宽度为8.12 GHz,损耗反射率达到-23 d B。良好的吸波性能归因于复合物有效的阻抗匹配特性及多重界面极化效应,多孔羰基铁/SiO_2/聚吡咯是一种轻质、宽频、强吸收的吸波材料。     

Preparation of graphene/BaFe12O19–Ni0.8Zn0.2Fe2O4 nanocomposite and its microwave absorbing properties

BaFe₁₂O₁₉–Ni_0.8Zn_0.2Fe₂O₄/graphene nanocomposites were prepared by a deoxidation technique. The structure, morphology and electromagnetic properties of the samples were detected by means of X-ray diffraction, scanning electron microscope, transmission electron microscopy, Raman, thermogravimetric analysis. Results show that the BaFe₁₂O₁₉–Ni_0.8Zn_0.2Fe₂O₄ nanoparticles dispersed on the graphene sheets. The magnetic properties of the composites decreased with the increasing of graphene contents, However, the electrical conductivity is in the contrary. Measurement of electromagnetic parameters shows that when the mass ratio of BaFe₁₂O₁₉–Ni_0.8Zn_0.2Fe₂O₄ to graphene is 5:1, it can be matched well. The microwave absorption property of it is below ?10 dB at 6.8–8.2 GHz and the minimum loss value is ?19.63 dB at 7.2 GHz. The introduction of graphene can increase the dielectric loss and has an important effect on the microwave absorption properties.     

One‐step in situ growth of magnesium ferrite nanorods on graphene and their microwave‐absorbing properties

The magnesium ferrite nanorods/graphene (MgFe₂O₄ NR/G) composites were prepared by a facile one‐step surfactant‐assisted solvothermal method. The structure and morphology of as‐prepared composite materials were characterized by electron microscopy, energy dispersive spectrometry, Raman spectrometry, X‐ray diffraction, FT‐IR and X‐ray photoelectron spectroscopy. The homogeneous MgFe₂O₄ nanorods with a typical diameter of about 100 nm were well distributed on graphene. The electromagnetic parameters were measured using a vector network analyzer. A minimum reflection loss (RL) of ?40.3 dB was observed at 14.9 GHz with a thickness of 3 mm, and the effective absorption frequency (RL  <   ? 10 dB) ranged from 12.0 to 18.0 GHz, indicating the remarkable microwave absorption performance of the MgFe₂O₄ NR/G composites. The absorbing property of as‐obtained composites was better than that of the pure MgFe₂O₄ nanorods. The synergistic effect of MgFe₂O₄ and graphene was responsible for the enhanced absorbing performance.     

Synthesis,characterization and microwave absorption properties of polyaniline/Sm-doped strontium ferrite nanocomposite

Sm-doped strontium ferrite nanopowders (SrSm_0.3Fe_11.7O₁₉) and their composites of polyaniline (PANI)/SrSm_0.3Fe_11.7O₁₉ with 10 wt% and 20 wt% ferrite were prepared by a sol–gel method and an in-situ polymerization process, respectively. The structure, magnetic properties and microwave absorption properties of the samples were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and vector network analyzer, respectively. The particle size of SrSm_0.3Fe_11.7O₁₉ was about 35 nm by using XRD. The ferrite successfully packed by PANI. PANI/SrSm_0.3Fe_11.7O₁₉ possessed the best absorption property with the optimum matching thickness of 3 mm in the frequency of 2–18 GHz. The value of the maximum reflection loss (RL) were −26.0 dB at 14.2 GHz with the 6.5 GHz bandwidth and −24.0 dB at 13.8 GHz with the 7.9 GHz bandwidth for the samples with 10 wt% and 20 wt% ferrite, respectively.     

Enhanced Electromagnetic Wave Absorption Properties of Ultrathin MnO2 Nanosheet-Decorated Spherical Flower-Shaped Carbonyl Iron Powder

In this work, spherical flower-shaped composite carbonyl iron powder@MnO₂ (CIP@MnO₂) with CIP as the core and ultrathin MnO₂ nanosheets as the shell was successfully prepared by a simple redox reaction to improve oxidation resistance and electromagnetic wave absorption properties. The microwave-absorbing properties of CIP@MnO₂ composites with different filling ratios (mass fractions of 20%, 40%, and 60% after mixing with paraffin) were tested and analyzed. The experimental results show that compared with pure CIP, the CIP@MnO₂ composites have smaller minimum reflection loss and a wider effective absorption bandwidth than CIP (RL < −20 dB). The sample filled with 40 wt% has the best comprehensive performance, the minimum reflection loss is −63.87 dB at 6.32 GHz, and the effective absorption bandwidth (RL < −20 dB) reaches 7.28 GHz in the range of 5.92 GHz–9.28 GHz and 11.2 GHz–15.12 GHz, which covers most C and X bands. Such excellent microwave absorption performance of the spherical flower-like CIP@MnO₂ composites is attributed to the combined effect of multiple beneficial components and the electromagnetic attenuation ability generated by the special spherical flower-like structure. Furthermore, this spherical flower-like core–shell shape aids in the creation of discontinuous networks, which improve microwave incidence dispersion, polarize more interfacial charges, and allow electromagnetic wave absorption. In theory, this research could lead to a simple and efficient process for producing spherical flower-shaped CIP@MnO₂ composites with high absorption, a wide band, and oxidation resistance for a wide range of applications.     

NiFe2O4/T-ZnOw复合材料的制备及电磁波吸收性能

采用铁氧体化学镀在四角氧化锌晶须(T-ZnOw)表面包覆NiFe2O4镀层,制备了NiFe2O4/T-ZnOw复合材料。利用X射线衍射仪、扫描电镜、能谱分析仪对镀覆前后T-ZnOw的结构、形貌等进行了表征。利用矢量网络分析仪研究了NiFe2O4/T-ZnOw复合材料的电磁波吸收性能。结果表明,化学镀覆后,在T-ZnOw表面包覆了尖晶石型NiFe2O4镀层,生成了NiFe2O4/T-ZnOw复合材料,该材料为磁损耗型材料。化学镀覆过程中T-ZnOw的装载量会影响复合材料的介电常数和磁导率,当T-ZnOw装载量为0.2g时,所制备的复合材料具有最大的介电常数、磁导率、介电损耗和磁损耗,当吸收层厚度达到3 mm时,反射率在14 GHz处达到-11 dB。     

A controllable preparation of two-dimensional cobalt oxalate-based nanostructured sheets for electrochemical energy storage

Well-defined two-dimensional （2D） cobalt oxalate （CoC₂O₄·2H₂O） nanosheets exhibit more excellent property than common bulk cobalt oxalate due to high specific surface areas and high-efficient transport of ion and electron. However, the delicate control of the 2D morphology of CoC₂O₄·2H₂O during their synthesis remains challenging. Herein, 2D CoC₂O₄·2H₂O nanosheets （M1）, grown by straightforward che...     

NZFO-PZT磁电复合纳米纤维的制备及其吸波性能

采用静电纺丝法制备(1-x)Ni_0.5Zn_0.5Fe₂O₄-(x)Pb(Zr_0.52Ti_0.48)O₃(简称为(1-x)NZFO-(x)PZT, x=0.1、0.2、0.3、0.4、0.5)磁电复合纳米纤维, 研究了PZT含量对复合纳米纤维结构、电磁特性及微波吸收性能的影响。所有样品均由尖晶石结构NZFO和钙钛矿结构PZT两相所组成。由于NZFO磁损耗与PZT介电损耗的协同效应及界面效应的加强, 适量PZT相的引入可改善复合纳米纤维吸波涂层的电磁阻抗匹配和衰减特性, 提高微波吸收性能。x=0.3和0.4的复合纳米纤维分别在低频和高频范围表现出最强的微波吸收能力。当涂层厚度为2.5~5.0 mm时, x=0.3样品的最小反射损耗在6.1 GHz处达-77.2 dB, 反射损耗小于-10 dB的有效吸收带宽为11.2 GHz(2.8~12.9和16.9~18 GHz);x=0.4样品的最小反射损耗位于18 GHz处为-37.6 dB, 有效吸收带宽达到12.5 GHz(3.3~12.5和14.7~18 GHz)。     

NZFO-PZT磁电复合纳米纤维的制备及其吸波性能

采用静电纺丝法制备(1-x)Ni_0.5Zn_0.5Fe₂O₄-(x)Pb(Zr_0.52Ti_0.48)O₃(简称为(1-x)NZFO-(x)PZT, x=0.1、0.2、0.3、0.4、0.5)磁电复合纳米纤维, 研究了PZT含量对复合纳米纤维结构、电磁特性及微波吸收性能的影响。所有样品均由尖晶石结构NZFO和钙钛矿结构PZT两相所组成。由于NZFO磁损耗与PZT介电损耗的协同效应及界面效应的加强, 适量PZT相的引入可改善复合纳米纤维吸波涂层的电磁阻抗匹配和衰减特性, 提高微波吸收性能。x=0.3和0.4的复合纳米纤维分别在低频和高频范围表现出最强的微波吸收能力。当涂层厚度为2.5~5.0 mm时, x=0.3样品的最小反射损耗在6.1 GHz处达-77.2 dB, 反射损耗小于-10 dB的有效吸收带宽为11.2 GHz(2.8~12.9和16.9~18 GHz);x=0.4样品的最小反射损耗位于18 GHz处为-37.6 dB, 有效吸收带宽达到12.5 GHz(3.3~12.5和14.7~18 GHz)。