Nio.4Co0.24Zno.36Lax Fe2-x O4铁氧体微波吸收特性的研究

采用溶胶-凝胶工艺制备了Ni0.4Co0.24Zn0.36LaxFe2-xO4铁氧体,利用XRD和微波网络矢量分析仪对其相成分和吸收特性进行研究,实验发现:适量掺杂镧时能够增大吸收频带宽度,改善吸收性能;当x =0.07时,最大吸收可达38.55dB,几乎在整个频段内吸收量都大于15dB,这非常有利于作为高频吸波材料.通过对Ni0.4Co0.24Zn0.36La0.07Fe1.93O4铁氧体烧结温度的分析,发现在1000℃烧结,晶粒只有80nm左右,吸收性能最好.     

Influence of Y~(3+),Yb~(3+),Gd~(3+) cations on structural and electromagnetic properties of CuFe_2O_4 nanoferrites prepared via one step sol-gel method

Rare earths(REs) play a key role in distorting spinel structure by creating some defects at the lattice sites and make them suitable for magnetodielectric applications.In the present study,the nanoferrites of CuRE_(0.02)Fe_(1.98)O_4,where REs=Y~(3+),Yb~(3+),Gd~(3+),were prepared using one step sol-gel method.The prepared samples are copper ferrite(CFO),yttrium doped copper ferrite(Y-CFO),ytterbium doped copper ferrite(Yb-CFO) and gadolinium doped copper ferrite(Gd-CFO),respectively.The single-phase structure of all the REs doped nanoferrites was determined by X-ray diffraction(XRD) analysis.The porosity,agglomerations and grain size of the REs doped copper ferrite were examined using field emission scanning electron microscopy(FESEM) analysis.Fourier transform infrared spectroscopy(FTIR)elaborates the phase formation and environmental effects on the REs doped nanoparticles(NPs).The recorded room temperature M-H loops from a vibrating sample magnetometer(VSM) elucidate the magnetic properties of the REs doped spinel nanoferrites.The magnetic saturation(M_s) was calculated in the range of 23.08 to 51.78 emu/g.The calculated coercivity values(272.6 to 705.60 Oe) confirm the soft magnetic behavior of REs doped copper ferrites.Furthermore,the electromagnetic and dielectric properties were assessed using a Vector network analyzer(VNA) from 1 to 6 GHz.The permeability,permittivity,dielectric tangent loss and electric modulus of the REs doped spinel ferrites illustrate that the prepared NPs may be suitable for microwave and high frequency applications.     

Systematic study of Ce3+ on the structural and magnetic properties of Cu nanosized ferrites for potential applications

Ce~(3+) substituted Cu-spinel nanoferrites CuCe_xFe_(2-x)O_4(x=0.00, 0.02, 0.04, 0.06, 0.08 and 0.10) were synthesized via sol-gel self-combustion hybrid route. Single phase spinel ferrite of Cu nanoferrites were examined using X-ray diffraction(XRD) analysis whereas the multiphase structure was observed as Ce contents increased from x=0.06. Field emission scanning electron microscopy(FESEM), Thermogravimetric and differential thermal analysis(TGA and DTA) and Fourier transform infrared spectroscopy(FTIR) were used to find out the morphology phase and metal stretching vibrations of Ce~(3+) substituted nanocrystalline ferrites. The crystallite size was increased and found in the range of 25-91 nm. The agglomerations in Cu ferrite samples increase as the Ce~(3+) concentration increases. The magnetic properties such as remanence, saturation magnetization, coercivity, Bohr magneton and magnetocrystalline anisotropy constant(K) were determined using M-H loops recorded from a vibrating sample magnetometer(VSM). Saturation magnetization, remanence and coercivity are increased as the Ce~(3+)contents increase in Cu nanocrystalline samples. Moreover, law of approach to saturation(LoA) was used to calculate the maximum value of saturation for Ce-doped Cu nanoferrites. The soft magnetic behaviour of the Cu nanoferrite is observed as compared to the samples substituted with the increased Ce contents in Cu nanocrystalline ferrite. Bohr magneton and magnetocrystalline anisotropy are found to increase with the substitution of rare earth Ce~(3+) contents in Cu spinel nanocrystalline ferrite. Cedoped Cu nanocrystalline ferrites with excellent properties may be suitable for potential applications in sensing, security, switching, core, multilayer chip inductor, biomedical and microwave absorption applications.     

Synthesis and spectroscopic studies of Zn_4B_6O_(13) and Eu/Tb single-doped Zn_4B_6O_(13) phosphors

In this study, Zn_4B_6O_(13), Eu-and Tb-doped Zn_4B_6O_(13) phosphors were prepared by conventional solid state reaction method and the samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM) and photoluminescence spectroscopy(PL). The doped rare-earth ions had little influence on the crystal structure of Zn_4B_6O_(13), but obviously affected the morphology of Zn_4B_6O_(13) particles. The PL results indicated that the 5% Eu-doped sample and 1% Tb-doped sample had the highest intensity in their respective different concentrations doped samples. The CIE chromaticity coordinates indicated that Zn_4B_6O_(13), Zn_4B_6O_(13):Eu and Zn_4B_6O_(13):Tb showed the three basic colors of blue, red and green, respectively. Evidently, the white light could appear only at appropriate intensity of blue, red and green components.     

MnO_2掺杂对NiZn铁氧体磁性能的影响

采用传统陶瓷工艺制备了MnO2掺杂Ni0.88Zn0.12Fe1.98O4铁氧体材料。实验发现,较高的烧结温度有助于NiZn铁氧体磁导率的提高,但过高和过低烧结温度都不利于材料品质因数的提高,从降低损耗的角度考虑,最佳烧结温度为1220℃。当NiZn铁氧体中MnO2掺杂量为1.5%时,铁氧体晶粒生长均匀,平均晶粒尺寸适中,能获得最高的品质因数,过低或过高的掺杂量都不利于损耗的降低。铁氧体饱和磁感应强度随MnO2掺杂量的增多先上升,后下降,但总体的变化程度都不大。而矫顽力则随掺杂量的增多持续下降。相关的影响机制在文中作了详细的讨论。     

注射成形粘结钕铁硼/铁氧体复合磁体的研究

对注射成形粘结Nd-Fe-B/铁氧体复合磁体进行了深入的研究。实验结果表明：随着铁氧体磁粉的加入，复合磁体的磁性能虽略有降低，但其力学性能及热稳定性均有大幅度改善，特别是在铁氧体含量为87%（质量分数时），复合磁体内禀矫顽力温度系数为零，不同磁粉间静磁场的存在，使得复合磁体在铁氧体含量低于70%（质量分数）时，其磁性能大于平均值，而大于70%（质量分数）时则小于平均值。     

MgO对以细磁铁精矿为主的烧结矿微观结构的影响

研究了MgO对以细磁铁精矿为主的烧结矿显微结构的影响。显微结构分析表明：烧结矿MgO的质量分数从1．4%提高到2．3％时,MgO对烧结矿微观结构具有明显的影响。低MgO时,未氧化的Fe3O4及其部分氧化生成的Fe2O3与铁酸钙粘结相形成了烧结矿良好的显微结构,其烧结矿强度良好。高MgO时,烧结矿生成了大块再结晶磁铁矿,同时生成了铁酸镁和镁铁橄榄石等一系列含镁矿物,MgO稳定了磁铁矿和含镁矿物的晶格,这些矿物与赤铁矿、铁酸钙等共存和互连。但MgO矿化需要较高的烧结温度和较长的高温保持时间,垂直烧结速度和利用系数有明显的降低。     

新型(Fe,Co)-Zr-RE-B非晶合金的热稳定性和磁性

利用旋铸技术制备了一种新型的含稀土元素的铁基非晶合金。研究了Nd含量对Fe70Co8Zr7-xNdxB15(x=0～6%原子数分数)合金的非晶形成能力、热稳定性和磁性能的影响。当该合金系的Nd含量在0～6%(原子数分数)变化时,其饱和磁感应强度(Js)在1.10T～1.37T范围内变化,矫顽力(Hc)在2.28A/m～8.15A/m范围内变化。Js随Nd含量的增加而增加,当Nd含量为2%和3%时,其Hc值均在3A/m以下,且在Nd含量为2%时,具有最高的非晶形成能力(glassformationability简称GFA)即大的ΔTx(达61K);同时又有良好的软磁性能,其Js和Hc值分别为1.25T和2.28A/m。经对比得出,Fe70Co8Zr5RE2B15(RE=Ce、Pr、Gd和Tb)合金与Fe70Co8Zr5Nd2B15具有相近的非晶形成能力和磁性能。     

Effects of cerium substitution on phase components,microstructures and magnetic properties of Nd-Fe-Ti-B alloy

(Nd_(1-x)Ce_x)_(12)Fe_(77)Ti_5B_6(x = 0,0.2,0.3,0.4,0.6,0.8)alloys were prepared by melt-spinning and annealing techniques.The phase constitutions,microstructures and magnetic properties were investigated by powder X-ray diffraction(XRD),a differential scanning calorimeter(DSC),a vibrating sample magnetometer(VSM)and a transmission electron microscope(TEM).It is found that with the increase of Ce content,the coercivity of the(Nd_(1-x)Ce_x)_(12)Fe_(77)Ti_5B_6 alloys reaches maximum first and then decreases.The maximum coercivity reaches 18.5 kOe obtained in the sample of 20% Ce substituted which is 34%higher than the Ce-free sample.TEM results reveal that the micro structure refinement effect is responsible for the coercivity improvement.This phenomenon implies that in some cases,Ce and Ti co-doping is more beneficial to improving of the coercivity than Ti single doping in Nd-Fe-B alloys.With further Ce addition,magnetic properties deteriorate due to the formation of CeFe_2 and TbCu_7-type phases.     

Effect of Nd3+ substitution on structural and magnetic properties of Mg–Cd ferrites synthesized by microwave sintering technique

Nd~(3+) substituted spinel ferrites with formula Mg_xCd_(1-x)Nd_(0.03)Fe_(1.97)O_4(x = 0.0.2,0.4,0.6.0.8 and 1.0)were prepared by oxalate co-precipitation method using novel microwave sintering technique. AR grade sulphates were used as starting chemicals. The samples were sintered at optimized power of 70 W for10 min in a microwave oven(800 W). The structural analysis of these samples was done by using X-ray diffraction, scanning electron microscope and Fourier transform IR techniques. The XRD analysis of the synthesized ferrite confirms the formation of cubic spinel structure of ferrite. The influence of Nd3+substitution on various structural parameters of Mg-Cd ferrites was reported. IR study indicates the spectra contain two intense absorption bands around 600 and 400 cm~(-1) in addition with four extra bands. The magnetic properties of all ferrites were studied by using a vibration sample magnetometer.The crystallite and grain size dependant magnetic properties are observed. The composition Mg_(0.6)Cd_(0.4)Nd_(0.03)Fe_(1.97)O_4 has better magnetic properties that can be used in recording media. The fast synthesis of spinel ferrites is yielded due to use of the microwave sintering technique.     

Electromagnetic and microwave absorption properties of Er-Ho-Fe alloys

The Er_xHo_(2-x)Fe_(17)(x = 0.0, 0.1,0.2, 0.3, 0.4) powders were prepared by arc melting and high energy ball milling method. The influence of the Er substitution on phase structure, morphology, saturation magnetization,electromagnetic parameters was investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM), vibrating sample magnetometer(VSM) and vector network analyzer(VNA),respectively. The results show that the saturation magnetization increases and the average particle size increases with the increase of Er content. The minimum absorption peak frequency shifts towards a lower frequency region with the increase of Er content. The Er_(0.3)Ho_(1.7)Fe_(17) powder can achieve the minimum RL of-24.07 dB at 6.96 GHz with a thickness of 2.0 mm and the minimum RL is less than-20 dB at the thickness range from 2.0 to 3.0 mm. The minimum RL of Er_(0.3)Ho_(1.7)Fe_(17) is-37.26 dB at5.68 GHz and the frequency bandwidth of R-10 dB reaches about 1.2 GHz with a thickness of 2.4 mm.And the microwave absorbing properties of the composite with different weight ratios of Er_(0.3)Ho_(1.7)Fe_(17)/graphene were researched. The microwave absorbing peaks of the composite shift to lower frequency with the increase of graphene content. The values of the minimum RL of Er_(0.3)Ho_(1.7)Fe_(17)/graphene are close to-10 dB with absorbing coating thicknesses increased.     

镝掺杂W型钡镍铁氧体的制备及电磁性能研究

采用固相反应法制备了掺镝W型钡镍铁氧体粉体。利用X射线衍射仪及扫描电子显微镜对其晶体结构及微观形貌进行分析,使用微波网络分析仪对其微波电磁性能进行研究。结果表明:1350℃时,不同Dy掺杂量下均形成了纯度较高的W型钡镍铁氧体,六角片状结构完整。在15～18GHz频段:μ″,tanμ值随Dy掺杂量的增加而增大,掺镝摩尔分数x=0.08时达到最大。     

Ionic liquid mediated morphologically improved lanthanum oxide nanoparticles by Andrographis paniculata leaves extract and its biomedical applications

Greener synthesis of ionic liquid(IL) assisted lanthanum oxide(La_2O_3) nanoparticles(NPs) was followed using Andrographis paniculata leaves extract by hydrothermal method at low temperature,The IL assisted La_2O_3(La_2O_3-IL) NPs were characterized by various properties such as structural,spectral,optical,morphological,and biological studies.Powder X-ray diffraction studies confirm that La_2O_3-IL NPs crystallize in the form of body-centered cubic structure and average crystalline size is shown-43 nm.FTIR and Laser Raman spectroscopy confirm the La-O,O-H and various functional groups.The La-O stretching vibration band attributes at 639 cm~(-1).The optical property of La_2O_3-IL NPs was characterized by UV-Vis and photo luminesce nce spectroscopy.The sharp and intense absorbance peak observed in the UV region at 288 nm can be assigned.In the PL spectrum,we observe two different emission bands like blue and green emission.The morphological and particle size determination were investigated by SEM with EDX spectra and TEM analyses.The agglomerated particles of hexagonal,spherical,and parallelogram shape are observed in the TEM images.The chemical elements,binding energies as well as La metal states on the surface of these synthesized NPs were determined using XPS.La_2O_3 NPs for good biological activities regarding antibacterial and anti-inflammatory potentials could be utilized in different biological applications to the food and biomedical industries.La_2O_3-IL has a high percentage of inhibitions than La_2O_3 and standard diclofenac.     

Electrochemical synthesis,structure characterization and magnetic properties of Tb_xFe_7Co_3(x=0,0.6,0.8) nanowires

Highly ordered Tb_xFe_7 Co_3(x=0,0.6,0.8) nanowires were synthesized in alumina templates by electrochemical deposition method.Here,the effects of Tb content and annealing treatment on the phase composition,morphology,crystalline structure and magnetic properties were investigated.The asdeposited Tb_0 Fe_7 Co_3 nanowires comprise Fe_7 Co_3 phase.While after adding Tb,the diffraction peaks slightly shift left,indicating the infiltration of Tb atoms into Fe_7 Co_3 phase.After annealing,Tb_0 Fe_7 Co_3 nanowires still consist of Fe_7 Co_3 phase with a slight enhancement on coercivity.While the annealed nanowires with Tb doped present a complex phase composition containing Fe3 Tb,Fe_2 Tb,Co_3 Tb,Co_(17)Tb_2,TbFeO_3 and Fe_2 O_3 phases distribute in the central portion,and Co_(0.72)Fe_(0.28) at the nanowire outer walls.The annealed Tb_xFe_7 Co_3(x=0.6,0.8) nanowires show higher magnetic performance owing to the formation of hard magnetic phases,the interfacial elastic coupling between hard and soft phases and the coherent Fe3 Tb/Co_3 Tb interface which restrain the domain wall motion.To be specific,the coercivity and remanence ratio of TbxFe_7 Co_3(x=0.6,0.8) nanowires significantly enhance with increasing Tb content.     

AC susceptibility and FC-ZFC magnetic properties of SrTb_xFe_(12-x)O_(19) and SrTm_xFe_(12-x)O_(19) hexaferrites:a comparative study

In this comparative study,Tb and Tm substituted Sr-hexafe rrites(HFs) with the chemical compositions of SrTb_xFe_(12-x)O_(19) and SrTm_xFe_(12-x)O_(19)(x=0.00,0.02 and 0.04) were fabricated via citrate sol-gel approach.The AC susceptibility and FC-ZFC magnetization were investigated.The product structure and morphologies were also investigated via XRD,TEM and SEM along with EDX.Measurements of temperature dependence of magnetization M-T and AC magnetic susceptibility versus temperature were carried out.The various synthesized HFs displayed ferrimagnetic behavior within 10-325 K.At lower temperatures,super-spin glass-like behavior was noticed.Neel-Arrhenius and Vogel-Fulcher models were employed to explore the experimental data of AC susceptibility.     

Structural and Magnetic Properties of the New Type of Rare Earth-Iron-Nitrogen Intermetallic Compounds

We succeed in inserting a number of nitrogen atoms into the R_2Fe_(17)and RTiFe_(11)intermetalliccompounds.The nitrides retain original Th_2Zn_(17)(or Th_2Ni_(17_)and ThMn_(12)structures,but with an increase inthe unit cell volume.The interstitial nitrogen atoms are found to have an effect of increasing the Curie tempera-ture and saturation magnetization.Moreover,a distinct effect on the magnetocrystalline anisotropy is also ob-served in these nitride compounds.Especially,NdTiFe_(11)N_(0.5)and SmTiFe_(11)N_2 have excellent intrinsic magneticproperties favourable for permanent magnet applications.     

Eco-friendly green synthesis of novel magnetic Fe_3O_4/SiO_2/ZnO-Pr_6O_(11) nanocomposites for photocatalytic degradation of organic pollutant

This study reports the successful so nochemical synthesis of novel Fe_3O_4/SiO_2/ZnO-Pr_6O_(11)(Fe/Si/Zn-Pr_6O_(11)) nanocomposites using fructose as a green capping agent.The influence of various parameters containing capping agent,power and time of ultrasound irradiation was investigated to reach optimum morphology and size conditions.The products obtained were characterized by transmission electron microscopy(TEM),UV/Vis diffuse reflectance spectroscopy(DRS),Fourier transform infrared spectra(FT-IR),vibration sample magnetometer(VSM),scanning electron microscopy(SEM),energy dispersive X-ray microanalysis(EDS) and X-ray diffraction(XRD).The Fe_3O_4/SiO_2/ZnO-Pr_6O_(11) nanocomposites display remarkably enhanced photocatalytic activity towards rhodamine b degradation(89.6%)and Congo red(84.7%) under UV irradiation compared with the other products.The results illustrate that the photocatalytic efficiency of magnetic nanocomposites is very much higher than pure Pr_6O_(11)nanostructures.Magnetic photocatalyst still has good stability after five successive runs.So,these recyclable nanocomposites can play a role in the treatment of both industrial and domestic contaminated water.     

Enhanced magnetostrictive properties of lightly Pr-doped Fe_(83)Ga_(17) alloys

Fe_(83)Ga_(17)Pr_x alloys,where x=0,0.2,0.4,0.6 and 1.0,were prepared by a non-consumable vacuum arc melting technique under an inert argon gas atmosphere.The crystal structure and surface morphologies of the alloys were studied by X-ray diffraction(XRD) and scanning electron microscopy(SEM),respectively.Local compositional variations were measured by energy dispersive X-ray spectroscopy(EDXS).The magnetostriction coefficients of the alloys were measured by means of a differential resistive strain sensor.The magnetism of the sample was measured by a vibrating sample magnetometer(VSM).The results show that the parent Fe_(83)Ga_(17) alloy consists of a single A2 phase of bcc symmetry,whereas the Pr doped Fe_(83)Ga_(17) alloys are composed of the A2 phase of bcc structure and a small volume fraction of PrGa2 as a secondary phase.Most importantly,with increasing x,the magnetostriction coefficient of the Fe_(83)Ga_(17)Pr_x alloys first increases reaching a maximum saturation magnetostriction coefficient of192 ppm for x=0.6 at a magnetic field strength of 486 kA/m,then decreased.This maximum represents a 400% increase over the parent alloy with a mere 0.6 at% Pr doping.     

金属间化物（Sm_（1－x）Dy_x）_2Fe_（17）N_y中的各向异性机制探讨

本文主要通过变温穆斯堡尔谱等手段研究金属间化物（Ｓｍ（１－ｘ）Ｄｙｘ）２Ｆｅ（１７）Ｎｙ（ｘ＝０．４；２＜ｙ＜３）的自旋重取向现象，进而对其中的各向异性产生机制进行分析。由实验结果得出Ｄｙ次格子的单轴各向异性较强，导致在１５０Ｋ～１００Ｋ较低温度下出现自旋重取向现象。     

Effect of template on catalytic performance of La_(0.7)Ce_(0.3)Ni_(0.7)Fe_(0.3)O_3 for ethanol steam reforming reaction

Perovskite-type oxides La_(0.7)Ce_(0.3)Ni_(0.7)Fe_(0.3)O_3(LCNF) were synthesized by polystyrene colloidal crystal templating(LCNF-CCT) and polystyrene polymer templating(LCNF-PS) through co-precipitation. The structure and physicochemical properties of the obtained oxides were investigated by scanning electron microscopy, X-ray diffraction, N_2 adsorption-desorption, Fourier transform infrared spectrometry, H_2 temperature-programmed reduction and H_2 temperature-programmed desorption, as well as X-ray photoelectron spectroscopy. The results show that the as-synthesized LCNF-CCT perovskite possesses large specific surface area and regular pore size distribution. In addition, the formation of additional oxygen vacancies on the surface favors the migration of lattice oxygen from the bulk phase to the surface and production of more metallic sites, thus improving the activity and resistance to carbon deposition of catalysts in ethanol steam reforming reaction.