热处理温度对纳米 CoFe 2O 4/ SiO 2复合材料结构和磁性的影响

采用溶胶2凝胶法制备了纳米 Co Fe 2O 4/ SiO 2复合材料。利用 X射线衍射(XRD) 、 透射电镜( TEM) 、 振动样品磁强计(VSM)和 Mssbauer 效应研究了纳米复合材料结构、 晶粒尺寸及磁性。结果表明 , 样品中 Co Fe 2O 4的晶粒尺寸随着热处理温度的提高而增加 , 非晶态 SiO 2的存在有效地抑制了 Co Fe 2O 4晶粒的生长。VSM结果表明 , 样品的比饱和磁化强度和矫顽力随 Co Fe 2O 4晶粒尺寸的增加而变大。Mssbauer 效应结果表明 , 随着热处理温度的提高 , 样品从超顺磁和磁有序的混合状态转变为完全的磁有序状态。     

纳米Co_(1-x)Zn_xFe_2O_4/SiO_2复合材料的结构和磁性

为了研究Zn2+含量对CoZn铁氧体结构和磁性的影响,以正硅酸乙酯和硝酸盐为原料,用溶胶-凝胶法制备了纳米Co1-xZnxFe2O4/Si O2(0≤x≤1)复合材料。利用XRD、TEM、VSM和M ssbauer效应分析了样品的结构、形貌和磁性。结果表明,经900℃热处理后,Co1-xZnxFe2O4/Si O2复合材料中Co1-xZnxFe2O4为晶粒分布均匀的尖晶石铁氧体结构。Zn2+替代Co2+后引起Co1-xZnxFe2O4晶格膨胀。随Zn2+含量的增加,样品的矫顽力减小,而比饱和磁化强度先增大后减小,样品从磁有序状态转变为顺磁状态。Zn2+的掺杂对Fe3+核处的s电子密度有较大的影响,对尖晶石结构对称性影响较小。     

(1-x)CaTiO_3/xNi_(0.5)Zn_(0.5)Fe_2O_4复合材料的制备及其性能

采用固相反应法合成了(1-x)CaTiO3/xNi0.5Zn0.5Fe2O4(0≤x≤1.0)复合材料,并研究了复合材料的物相、微观结构、介电性能和磁性能。结果表明:样品中仅含有钙钛矿型CaTiO3和尖晶石型Ni0.5Zn0.5Fe2O4。1260℃保温3h,样品相对密度达到98.91%,颗粒尺寸约为2μm。样品介电常数随Ni0.5Zn0.5Fe2O4含量(x)增加而增大。当x=0.7、测试频率为103 Hz时,样品介电常数(εr)和介电损耗(tanδ)分别为2629.18和1.74。(1-x)CaTiO3/xNi0.5Zn0.5Fe2O4复合材料显示磁性。其中x=0.7时,样品饱和磁化强度(Ms)达到49.07A·m2/kg;这归因于Ni0.5Zn0.5Fe2O4具有优异的磁性能。     

固相法合成La2Ni0.5M0.5O4+δ(M=Co,Cu)材料及电性能

使用金属氧化物La2O3,NiO,CuO和Co2O3作为原料,固相反应法能够合成出具有K2NiF4型结构单一相的、且晶粒尺寸在35～50nm范围的La2Ni0.5M0.5O4 δ(M=Co,Cu)粉料,用XRD、SEM和直流四极探针电导测试法研究了合成La2Ni0.5M0.5O4 δ(M=Co,Cu)粉料的煅烧工艺条件和掺杂元素对电性能的影响以及粉料的颗粒形貌.随着煅烧温度的升高和保温时间的延长,晶粒尺寸在不断长大;合成的粉料在1300℃烧结5h后所有样品的电导率在空气条件下于100～800℃范围内都在增加.掺杂C0或Cu后的材料La2NiO4 δ的电导率均有增加,但掺杂Co后材料电导率要大于掺杂Cu的电导率.为此确定La2Ni0.5M0.5O4 δ(M=Co,Cu)类粉料固相法合成的适宜煅烧条件为1400℃下保温时间14h.     

Ni0.5Zn0.5Fe2O4粉末化学镀铜前后的电磁性能

本文用溶胶-凝胶自燃烧法制备了Ni0.5Zn0.5Fe2O4粉末颗粒,以甲醛为还原剂在Ni0.5Zn05Fe2O4颗粒表面进行了化学镀铜,制备了Cu/Ni0.5Zn0.5Fe2O4复合粉体.用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)对镀铜前的Ni0.5Zn0.5Fe2O4颗粒以及镀铜后的复合纳米颗粒进行了表征.对镀铜前的Ni0.5Zn0.5Fe2O4粉体和不同镀铜量的Cu/Ni0.5Zn0.5Fe2O4复合粉体进行了电磁性能的研究,结果表明镀铜后镍锌铁氧体的吸波性能明显提高,增重量为65%的Cu/Ni0.5Zn0.5Fe2O4复合粉体在频率为11GHz处反射率可达-12dB左右.     

尖晶石型(Zn1-δFeδ)[CoδFe2-δ]O4铁氧体纳米粒子的制备与磁性研究

采用分析纯CoCl2·6H2O、ZnCl2·6H2O、FeCl3·6H2O和NaOH为主要原料,控制反应物摩尔比,利用低温固相反应法制备了尖晶石型CoFe2O4、ZnFe2O4和Co0.5Zn0.5Fe2O4纳米粒子.采用X射线衍射、透射电子显微镜对样品的结构、形貌进行表征.在室温下采用振动样品磁强计对其磁性能进行了测定.结果表明:反尖晶石型CoFe2O4纳米粒子的饱和磁化强度为64.28A·m2/kg,呈亚铁磁性;正尖晶石型ZnFe2O4纳米粒子的饱和磁化强度为7.27A·m2/kg,表现出与块体的反铁磁性不同的超顺磁性;而Zn2+替代反尖晶石型CoFe2O4中的一部分磁性离子Co2+形成的复合铁氧体Co0.5Zn0.5Fe2O4的饱和磁化强度为35.06A·m2/kg,呈亚铁磁性.最后,对3种铁氧体的磁性来源进行了探究.     

Zr4+B位置换对(Pb0.5Ca0.5)(Fe(0.5)Nb0.5)O3

研究了Zr4+离子B位置换改性对(Pb0.5Ca0.5)(Fe0.5Nb0.5)O3陶瓷微波介电性能.实验结果表明,(Pb0.5Ca0.5)(Fe0.5Nb0.5)O3(PCFNZ)陶瓷样品呈现单一斜方钙钛矿相结构.随Zr(4+)离子的置换量增加,PCFNZ陶瓷体系的Qr值和晶粒尺寸逐渐减小;介电常数εr随着置换量增加...     

锌掺杂钴铁氧体:硬磁→软磁

采用共沉淀法制备了不同Zn2+掺杂量的Co1-xZnxFe2O4,研究了Zn2+掺杂量对其结构和磁性的影响。X射线衍射测试表明Co1-xZnxFe2O4成相良好,结晶随烧结温度增加而愈加完善。经400℃热处理2h的Co0.7Zn0.3Fe2O4晶粒尺寸由谢乐公式计算为8.57nm。利用振动样品磁强计研究其静态磁性,结果表明,Zn2+掺杂量对Co1-xZnxFe2O4磁性有显著影响,Zn2+含量越高矫顽力越低,同时饱和磁化强度越大,当x=0.3时,矫顽力仅为1352.82A/m,磁化强度为42A.m2/kg,实现了CoFe2O4从硬磁性到软磁性的转变,可作为潜在的高频软磁材料。     

纳米晶Co1-xZnxFe2O4薄膜的结构、磁性及温度特性

采用sol-gel方法制备了纳米晶Co1-xZnxFe2O4(x=0～0.3)薄膜.样品的结构、磁性及表面形貌分别用X射线衍射仪(XRD)、振动样品磁强计(VSM)和原子力显微镜(AFM)进行了表征.研究结果表明,400℃退火薄膜已生成单一的尖晶石结构,且样品的晶粒尺寸较小,平均晶粒尺寸在35nm以下.Zn2 离子含量的增加使样品的晶格常数有少许增大.Zn2 离子含量对样品的磁性能有较强的影响,样品的比饱和磁化强度在Zn2 离子含量x=0.2时达极大值(74.3(A·m2)/kg).变温测量显示,样品的磁化强度随温度升高呈下降趋势.当Zn2 含量从零增加到0.3,居里温度从530.0℃降至341.6℃.     

热处理工艺对尖晶石型Ni0.5Zn0.45Co0.05Fe2O4静磁性能的影响

利用溶胶凝胶法制备了尖晶石型 Ni0.5Zn0.45Co0.05Fe2O4 纳米颗粒,设置了3种热处理工艺,发现随着热处理温度的提高,热处理时间的延长,颗粒长大,静磁性能提高。当热处理温度为800℃,保温8h,材料具有比较好的静磁性能（Ms=30.241Oe,Hc=73.261 emg/g,μi=0.210）。另外,将前驱体在磁场条件下热处理,得到颗粒尺寸比同种热处理工艺未加磁场条件下的大,并且静磁性能有了比较大的提高,其比饱和磁化强度甚至比在更高热处理温度,更长热处理时间下制备的NiZnCo铁氧体大。     

Synthesis, Characterization and Electromagnetic Studies on Nanocrystalline Co0.5Zn0.5Fe2O4 Synthesized by Polyacrylamide Gel

Nanocrystalline Co0.5Zn0.5Fe2O4 ferrite was synthesized by polyacrylamide gel method. The electromagnetic and microwave absorption properties of the ferrite were investigated. The results indicated that calcining temperature of the ferrite had a significant influence on the effective properties of the ferrite. When the calcining temperature was 500, 600 and 700℃, the average size of particles was 10, 30 and 80 nm, respectively. The dielectric loss （ε″） and magnetic loss （μ″） of the ferrite was around 0.65 and 0.29 at 8.2 GHz, respectively. Microwave absorption properties of the ferrites were simultaneously influenced due to the strong correlation between reflection loss and electromagnetic parameters of the ferrite.     

One-dimensional SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers and enhancement magnetic property

SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers of diameters about 100 nm with mass ratio 1:1 have been prepared by the electrospinning and calcination process. The SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrites are formed after calcined at 700 degrees C for 2 hours. The composite ferrite nanofibers are fabricated from nanosized Ni(0.5)Zn(0.5)Fe2O4 and SrFe12O19 ferrite grains with a uniform phase distribution. The ferrite grain size increases from about 11 to 36 nm for Ni(0.5)Zn(0.5)Fe12O4 and 24 to 56 nm for SrFe12O19 with the calcination temperature increasing from 700 to 1100 degrees C. With the ferrite grain size increasing, the coercivity (Hc) and remanence (Mr) for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers initially increase, reaching a maximum value of 118.4 kA/m and 31.5 Am2/kg at the grain size about 40 nm (SrFe12O19) and 24 nm (Ni(0.5)Zn(0.5)Fe2O4) respectively, and then show a reduction tendency with a further increase of the ferrite grain size. The specific saturation magnetization (Msh) of 63.2 Am2/kg for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers obtained at 900 degrees C for 2 hours locates between that for the single SrFe12O19 ferrite (48.5 Am2/kg) and the single Ni(0.5)Zn(0.5)Fe2O4 ferrite (69.3 Am2/kg). In particular, the Mr value 31.5 Am2/kg for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers is much higher than that for the individual SrFe12O19 (25.9 Am2/kg) and Ni(0.5)Zn(0.5)Fe2O4 ferrite (11.2 Am2/kg). These enhanced magnetic properties for the composite ferrite nanofibers can be attributed to the exchange-coupling interaction in the composite.     

Synthesis and Electrical Properties of Li-modified Bi_(0.5)Na_(0.5)TiO_3-BaTiO_3 Lead-free Piezoelectric Ceramics

Lead-free piezoelectric ceramics (1-y)Bi0.5(Na1-xLix)0.5TiO3-yBaTiO3 with x=0-0.125 and y=0.02-0.12 were fabricated by a solid-state reaction process, and their dielectric, piezoelectric and ferroelectric properties were investigated. The results show that the addition of Li+ significantly improves the sintering performance and piezoelectric properties of the ceramics. X-ray diffraction (XRD) patterns indicate that the ceramics possess pure perovskite structure. At room temperature, the ceramics provide hig...     

锰掺杂对(K_(0.5)Na_(0.5))NbO_3-LiNbO_3压电陶瓷结构和性能的影响

采用传统陶瓷制备工艺制备了(K_(0.5)Na_(0.5))NbO_3-LiNbO_3-xMnO_2压电陶瓷,分析了陶瓷样品的微观组织结构.实验结果表明,随MnO_2掺杂量的增多,陶瓷由四方相转变为正交相,晶粒的均匀性下降并生成K_3LiNb_6O_(17)相.研究了MnO_2不同掺杂量对陶瓷压电性能的影响.结果表明,随锰掺杂量的增加,材料逐渐变"硬",机电耦合系数k_p和压电常数d_(33)逐渐减小,同时Q_m逐渐增大;当MnO_2含量为0.8%(质量分数)时,陶瓷的机械品质因数达到最大,此时陶瓷的压电性能为:k_p=0.34,k_t=0.43,d_(33)=110pC/N,Q_m=401.3.     

NbO3-LiNbO3无铅压电陶瓷的烧结特性和压电性能研究

采用传统陶瓷烧结工艺制备了（1-x）（K0．5Na0．5）NbO3-xLiNbO3无铅压电陶瓷，研究了陶瓷的结构、烧结特性及电性能特征．制备的（K0．5Na0．5）NbO3-LiNbO3陶瓷为单一的钙钦矿结构，室温下其相结构随LiNbO3含量增加逐渐由正交相向四方相转变，显微结构也由于LiNbO3含量的不同而表现出很大差异．与（K0．5Na0．5）NbO3陶瓷相比，（K0．5Na0．5）NbO3-LiNbO3陶瓷的烧结温度降低，烧结特性得到改善．（K0．5Na0．5）NbO3-LiNbO3陶瓷表现出优越的压电性能，其中0．94（K0．5Na0．5）NbO3—0．06LiNbO3（x=0．06）陶瓷的压电常数d33达到205pC／N，机电耦合系数kp为40．3％，kt达到49．8％．     

Thermomechanical Analysis of (Cu0.5Tl0.5)-1223 Substituted by Pr and La

The thermomechanical analysis (TMA) of Cu 0.5 Tl 0.5 Ba 2 Ca 2 x R x Cu 3 O 10 δ,where R=Pr and La,with 0.0≤x≤0.15,was carried out in temperature range from 450 to 1145 K.The samples were prepared by singlestep solid state reaction technique.The prepared samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).The superconductivity of the prepared samples was investigated by electrical resistivity measurement.The results showed that low substitution content enhanced the (Cu 0.5 Tl 0.5)1223 phase formation,while the higher substitution content degraded this phase.The higher superconducting transition temperatures T c were found to be 114 K and 109 K at x= 0.025 for Pr-and La-substitutions,respectively.The average linear thermal expansion coefficient increased as x increased,while the shrinkage temperature decreased as x increased.Those results were emphasized by porosity and Vickers microhardness calculations.Debye temperature θ D was calculated from the linear thermal expansion coefficient data and correlated to T c to estimate the electron-phonon coupling λ ep.     

(Na0.5K0.5)NbO3基无铅压电陶瓷的研究

由于钙钛矿结构无铅压电陶瓷具有高的压电性能，已成为无铅压电陶瓷研究的热点．本文综述了钙钛矿结构无铅压电陶瓷（Na0．5K0.5）NbO3的研究进展和趋势．重点从添加第二组元、添加助烧剂、取代改性和制备方法四个方面，归纳和分析了（Na0．5K0.5）NbO3基无铅压电陶瓷的研究开发进展，并对（Na0.5K0.5）NbO3基无铅压电陶瓷今后的研究和发展提出一些建议．     

新型溶胶-凝胶工艺制备La0.5Ca0.5MnO3薄膜及性能分析

鉴于以醇盐为原料溶胶-凝胶制备La0.5Ca0.5MnO3薄膜工艺中存在诸多苛刻因素,本文以无机盐为原料采用溶胶-凝胶工艺在SiO2/Si(100)衬底上制备了La0.5Ca0.5MnO3薄膜.并用XRD、SEM和TEM等分析手段对薄膜进行了表征,通过不同磁场下电阻-温度(R-T)曲线,研究了样品的磁电阻(CMR)效应...     

无铅压电陶瓷K0.5Na0.5NbO3-BiFeO3的烧结工艺与压电性能研究

采用传统常压固相烧结工艺制备了掺杂0.8at%BiFeO₃(BF)的K_0.5Na_0.5NbO₃(KNN) 无铅压电陶瓷,着重研究了烧结温度与保温时间对陶瓷的晶体结构、相转变、致密度与压电、介电性能的影响. 研究结果表明, 所有陶瓷样品都为单一的钙钛矿结构, 烧结温度与保温时间对陶瓷样品的室温晶体结构与相转变温度几乎没有影响, 但对陶瓷的表面形貌、密度和压电性能有较大的影响. 当保温时间为3h,在1100℃至1150℃范围内, 随烧结温度的升高,陶瓷的压电常数d33、平面机电耦合系数Kp及机械品质因数Qm均一直升高, 介电损耗tanδ则显著降低. 当烧结温度为1150℃时, 随保温时间的增加, 陶瓷的压电性能先显著提高后基本保持不变. 1150℃保温2h烧结的陶瓷获得良好的性能：密度ρ=4.50g/cm³（致密度为95.63%）, d₃₃=132pC/N, K_p=45%, Q_m=333.73, tanδ=2.39%.     

Annealing Induced Enhancement in Magnetic Properties of Co0.5Zn0.5Fe2O4 Nanoparticles

In this paper, cobalt zinc ferrite (Co_0.5Zn_0.5Fe₂O₄) nanoparticles (NPs) have been prepared using chemical co-precipitation method. In order to investigate the annealing induced effects on their various physical properties, the prepared samples have been annealed at 500 °C, 650 °C and 1000 °C and then compared with as-prepared sample. X-ray diffraction (XRD) patterns of as-prepared and annealed samples at various temperatures exhibit single phase spinel structure. Enhancement in crystallinity and crystallite size is observed with the increase in annealing temperature. The annealing has also greatly influence the morphology and grain size of prepared NPs. The Co_0.5Zn_0.5Fe₂O₄ NPs have shown remarkable enhancement in magnetic moment with increase in annealing temperature. The bandgap energies of Co_0.5Zn_0.5Fe₂O₄ NPs have been measured via UV Spectrometer and observed to decrease with annealing temperature. FTIR spectra of the samples reveal the presence of both high frequency and low-frequency bands due to tetrahedral and octahedral sites, which corroborate well with the XRD results. The observed characteristics of cobalt zinc ferrite NPs as a function of annealing temperature are the rising contender for many data storage and nanodevice applications. Finally, the genotoxicity of prepared nanoferrites has been checked via comet assay.