Enhanced hyperthermia performance in hard-soft magnetic mixed Zn0.5CoxFe2.5−xO4/SiO2 composite magnetic nanoparticles

High quality Zn0.5CoxFe2.5?xO4(x=0,0.05,0.1,0.15)serial magnetic nanoparticles with single cubic structures were prepared by the modified thermal decomposition method,and Zn0.5CoxFe2.5?xO4/SiO2 composite magnetic nanoparticles were prepared by surface modification of SiO2.The magnetic anisotropy of the sample increases with the increase of the doping amount of Co2+.When the doping amount is 0.1,the sample shows the transition from superparamagnetism to ferrimagnetism at room temperature.In the Zn0.5CoxFe2.5?xO4/SiO2 serial samples,the maximum value of specific loss power(SLP)with 1974 W/gmetal can also be found at doping amount of x=0.1.The composite nanoparticles are expected to be an excellent candidate for clinical magnetic hyperthermia.     

Remanence Enhancement Effect in Ni_(0.7)Zn_(0.3)Fe_2O_4/Co_(0.8)Fe_(2.2)O_4 Ferrite Multilayer Film

Ni_(0.7)Zn_(0.3)Fe_2O_4/Co_(0.8)Fe_(2.2)O_4(NZFO/CFO) multilayer films are fabricated on Si(100) substrates by the chemical solution deposition method.The microstructure and magnetic properties are systematically investigated.The results of field-emission scanning electronic microscopy show that the grain size of the NZFO/CFO multilayer film is quite uniform and the thickness is about 300 nm.The remanence enhancement effect of the NZFO/CFO multilayer film can be mainly attributed to the exchange coupling interaction between NZFO and CFO ferrite films,which is in favor of the design and fabrication of modern electronic devices.     

Effect of Magnetic Anisotropy on Magnetic Thermal Induction of Mn_(0.3)Zn_(0.3)Co_xFe_(2.4-x)O_4 Nanoparticles

Mn_(0.3)Zn_(0.3)Co_xFe_(2.4-x)O_4 series magnetic nanoparticles are prepared by the high-temperature organic solvent method, and Mn_(0.3)Zn_(0.3)Co_xFe_(2.4-x)O_4@SiO_2 composite nanoparticles are prepared by the reverse microemulsion method. The as-prepared samples are characterized, and the results show that the magnetic anisotropy constant of nanoparticles increases with the cobalt content, and the magnetic thermal induction shows a trend of increasing first and then decreasing. The optimal magnetic thermal induction is obtained at x = 0.12 with a specific loss power of 2086 w/gmetal, which is a bright prospect in clinical magnetic hyperthermia.     

Magnetic field aligned orderly arrangement of Fe_3O_4 nanoparticles in CS/PVA/Fe_3O_4 membranes

The CS/PVA/Fe_3O_4 nanocomposite membranes with chainlike arrangement of Fe_3O_4 nanoparticles are prepared by a magnetic-field-assisted solution casting method. The aim of this work is to investigate the relationship between the microstructure of the magnetic anisotropic CS/PVA/Fe_3O_4 membrane and the evolved macroscopic physicochemical property. With the same doping content, the relative crystallinity of CS/PVA/Fe_3O_4-M is lower than that of CS/PVA/Fe_3O_4.The Fourier transform infrared spectroscopy(FT-TR) measurements indicate that there is no chemical bonding between polymer molecule and Fe_3O_4 nanoparticle. The Fe_3O_4 nanoparticles in CS/PVA/Fe_3O_4 and CS/PVA/Fe_3O_4-M are wrapped by the chains of CS/PVA, which is also confirmed by scanning electron microscopy(SEM) and x-ray diffraction(XRD)analysis. The saturation magnetization value of CS/PVA/Fe_3O_4-M obviously increases compared with that of non-magnetic aligned membrane, meanwhile the transmittance decreases in the UV-visible region. The o-Ps lifetime distribution provides information about the free-volume nanoholes present in the amorphous region. It is suggested that the microstructure of CS/PVA/Fe_3O_4 membrane can be modified in its curing process under a magnetic field, which could affect the magnetic properties and the transmittance of nanocomposite membrane. In brief, a full understanding of the relationship between the microstructure and the macroscopic property of CS/PVA/Fe_3O_4 nanocomposite plays a vital role in exploring and designing the novel multifunctional materials.     

Magnetoelectric effects in multiferroic Y-type hexaferrites Ba(0.3)Sr(1.7)CoxMg(2-x)Fe(12)O(22)

Y-type hexaferrites with tunable conical magnetic structures are promising single-phase multiferroics that exhibit large magnetoelectric effects. We have investigated the influence of Co substitution on the magnetoelectric properties in the Y-type hexaferrites Ba(0.3)Sr(1.7)CoxMg(2-x)Fe(12)O(22)(x = 0.0, 0.4, 1.0, 1.6). The spin-induced electric polarization can be reversed by applying a low magnetic field for all the samples. The magnetoelectric phase diagrams of BaBa(0.3)Sr(1.7)CoxMg(2-x)Fe(12)O(22) are obtained based on the measurements of magnetic field dependence of dielectric constant at selected temperatures. It is found that the substitution of Co ions can preserve the ferroelectric phase up to a higher temperature, and thus is beneficial for achieving single-phase multiferroics at room temperature.     

Controllable Synthesis and Magnetic Properties of Monodisperse Fe_3O_4 Nanoparticles

Magnetite(Fe_3O_4) nanoparticles with different sizes and shapes are synthesized by the thermal decomposition method.Two approaches,non-injection one-pot and hot-injection methods,are designed to investigate the growth mechanism in detail.It is found that the size and shape of nanoparticles are determined by adjusting the precursor concentration and duration time,which can be well explained by the mechanism based on the LaMer modei in our synthetic system.The monodisperse Fe_3O_4 nanoparticles have a mean diameter from 5nm to 16 nm,and shape evolution from spherical to triangular and cubic.The magnetic properties are size-dependent,and Fe_3O_4nanoparticles in small size about 5nm exhibit superparamagnetic properties at room temperature and maximum saturation magnetization approaches to 78 emu/g,whereas Fe_3O_4 nanoparticles develop ferromagnetic properties when the diameter increases to about 16 nm.     

Composites of nanotubular polyaniline containing Fe3O4 nanoparticles

Results of charge-transport and magnetic measurements of nanotubular polyaniline (PANI) composites containing Fe_3O_4 nanoparticles (～10nm) synthesized by a "template-free" method are reported. The T^{-1/2} resistivity has been observed, and dc magnetic susceptibility data are fitted to an equation χ=χ^*_P+C/T. With increasing weight ratio of Fe_3O_4, the electrical conductivity and temperature- independent susceptibility χ^*_P increase, and the Curie-type susceptibility is suppressed at low temperatures. Further discussions have been given. The PANI-H_3PO_4/Fe_3O_4 composite containing 27wt% of Fe_3O_4 nanoparticles is superparamagnetic, exhibiting very little hysteresis even at 5K.     

Characterizations of Tb:Zn2SiO4 films on silicon wafer prepared by sol-gel dip-coating and solid-phase reaction

Terbium-doped Zn_2SiO_4 films were successfully prepared on Si wafers by a simple sol-gel dip-coating and solid-phase reaction method of ZnO and SiO_2. X-ray diffraction (XRD) and UV－Vis absorption results revealed that films processed below 850℃ were ZnO in wurzite structure, and films processed above 850℃ were Zn_2SiO_4 in wellimite structure. Photoluminescence measurements of the Tb-doped Zn_2SiO_4 films showed two strong emission bands at 490 and 545nm. The photoluminescence lifetime was 4.6ms.     

有机盐制备的Fe3O4-葡聚糖纳米粒子的磁性能及表征

利用葡糖酸铁(C12H22FeO14·2H2O)和柠檬酸铁(C6H5O7Fe·5H2O)参与的化学共沉积法制备出单分散核心氧化铁的平均粒径为4.1nm,葡聚糖厚度约为11nm,总体平均粒径为26nm的Fe3O4葡聚糖复合纳米粒子.研究结果表明,复合粒子Fe3O4葡聚糖具有超顺磁性.制备过程中没有N2保护,得到的Fe3O4无机粒子的晶体结构几乎没有发生变化,证明了有机盐的抗氧化性,合成的Fe3O4葡聚糖复合纳米粒子具有较好的磁性能.其在室温下(300K)的饱和磁化强度为52emu/g,低温下(5K)的饱和磁化强度为63emu/g.并利用TEM、XRD、DLS和VSM(振动样品磁强计)等手段对其粒结构、形态、粒径和磁性能进行了表征.     

Novel Fe_3O_4@SiO_2@Ag@Ni trepang-like nanocomposites:High-efficiency and magnetic recyclable catalysts for organic dye degradation

A facile step-by-step approach is developed for synthesizing the high-efficiency and magnetic recyclable Fe_3O_4@SiO_2@Ag@Ni trepang-like nanocomposites.This method involves coating Fe_2O_3 nanorods with a uniform silica layer,reduction in 10%H_2/Ar atmosphere to transform the Fe_2O_3 into magnetic Fe_3O_4,and finally depositing Ag@Ni core-shell nanoparticles on the L-lysine modified surface of Fe_3O_4@SiO_2 nanorods.The fabricated nanocomposites are further characterized by x-ray diffraction,transmission electron microscopy,scanning electron microscope,Fourier transform infrared spectroscopy,and inductively coupled plasma mass spectroscopy.The Fe_3O_4@SiO_2@Ag@Ni trepang-like nanocomposites exhibit remarkably higher catalytic efficiency than monometallic Fe_3O_4@SiO_2@Ag nanocomposites toward the degradation of Rhodamine B(RhB) at room temperature,and maintain superior catalytic activity even after six cycles.In addition,these samples could be easily separated from the catalytic system by an external magnet and reused,which shows great potential applications in treating waste water.     

成分调制的La1－xSrxMnO3复合隧道结

利用磁控溅射和Sr成分的调制以及原位热处理方法，在10mm×10mm大小的(001) 取向SrTiO_３单晶衬底上制备出三明治结构为La_0.7Sr_0.3MnO３(100nm)/La_0.96Sr_0.04MnO_３ (5nm)/ La0.7Sr_0.3MnO_３ (100nm) 的隧道结外延薄膜，然后再次 利用磁控溅射方法，在三层单晶膜上方继续沉积Ir_２２Mn_７８(15n m)/Ni_７９Fe_２１(5nm)/Pt(20nm)等金属三层膜.最后利用深紫外曝 光和Ar离子束刻蚀等微加工技术，制备出长短轴分别为12和6μm或者8和4μm大小的椭圆形L a_１-xSr_xMnO_３成分调制的复合磁性隧道结.在4.2K和 外加磁场8 T的测试下，La_１-xSr_xMnO_３成分调制的复 合磁性隧道结其隧穿磁电阻(TMR)比值达到3270%, 直接从实验上证实了铁磁性La_{0.7Sr0.3MnO３金属氧化物的自旋极化率（97%）可接近100％，具 有很好的半金属性质. 关键词： １-x}Sr_xMnO_３')" href="#">La_１-xSr_xMnO_３ 半金属 成分调制 复合磁性隧道 结 隧穿磁电阻     

窄缝中气泡在磁性液体中的上升与变形

对窄缝中气泡在磁性液体中的上升与变形进行了可视化研究。定性分析了纳米磁性颗粒引发的黏度效应及表面活性剂分子依附作用对气泡上升速度与形状的影响。试验工质为体积浓度6.33%的水基Fe_3O_4磁性液体,同时对比了质量浓度25%的四甲基氢氧化铵水溶液、质量分数30%和50%的蔗糖溶液以及水中气泡的上升运动。窄缝间隙分别为1 mm和2 mm,气泡由底部不同直径的圆孔产生。试验结果表明:由于活性剂分子的存在,磁性液体气泡上升过程中由扁椭圆形渐转变为上圆下平的冠状,而其略大于水的黏度使气泡在1 mm窄缝中保持直线上升运动,但窄缝间隙增大到2 mm后,磁性液体中气泡的运动轨迹仍会发生振荡。     

采用PVA方法制备ZnO基发光稀磁半导体

不同的制备工艺对ZnO薄膜的微结构和性能有很大的影响,为了得到成本较低,样品具有较好特性的实验方法,对于制备手段进行了探索。使用PVA溶胶-凝胶法制备了Zn_0.88Co_0.12O薄膜,研究了不同退火工艺对其微结构的影响。对于Zn_0.88Co_0.12O样品的微结构和室温下的铁磁性和发光特性,具体比较分析了产生原因。对比了Co掺杂和复合Co、Fe掺杂Zn_0.88(Co_0.5Fe_0.5)_0.12O样品的微结构,采用振动样品磁强计(VSM)测量了样品的磁特性,发现单一掺杂的薄膜具有更好的晶体质量和更强的磁性。     

Synthesis and microwave absorption properties of graphene-oxide(GO)/polyaniline nanocomposite with Fe3O4 particles

In order to investigate the impedance matching properties of microwave absorbers,the ternary nanocomposites of GO/PANI/Fe₃O₄（GPF） are prepared via a two-step method,GO/PANI composites are synthesized by dilute polymerization in the presence of aniline monomer and GO,and GO/PANI/Fe₃O₄ is prepared via a co-precipitation method.The obtained nanocomposites are characterized by scanning electron microscopy（SEM）,X-ray diffraction（XRD）,and Fourier transform infrared spectroscopy（FTIR）,respectively.The microwave absorbability reveals enhanced microwave absorption properties compared with GO,PANI,and GO/PANI.The maximum reflection loss of GO/PANI/Fe₃O₄ is up to-27 dB at 14 GHz with its thickness being 2 mm,and its absorption bandwidths exceeding-10 dB are more than 11.2 GHz with its thickness values being in the range from 1.5 mm-4 mm.It provides that GO/PANI/Fe₃O₄ can be used as an attractive candidate for microwave absorbers.     

Local Structure Analysis of Lead Zinc Niobate-Barium Titanate Ceramic by X-Ray Absorption Spectroscopy and Density Functional Calculation

The local structure of an alternative Pb(Zn_(1/3)Nb_(2/3))O3-based perovskite ceramic is investigated. The 0.07 BaTiO_3-0.93 Pb(Zn_(1/3)Nb_(2/3))O_3 ceramic is synthesized using a combination of Zn_3 Nb_2 O_8 B-site precursor and BaTiO_3 perovskite phase stabilizer. Then, x-ray absorption spectroscopy and density functional theory are employed to calculate the local structure configuration and formation energy of the prepared samples. Ba2+ is found to replace_Pb)~(2+) in A-site with Zn~(2+) occupying B-site in Pb(2 n_(1/3)Nb_(2/3))O_3, while in the neighboring structure, Ti~(4+)replaces Nb~(5+) in B-site with Pb~(2+) occupying A-site. With the substitution of BaTiO_3 in Pb(Zn_(1/3)Nb_(2/3))O_3, the bond length between Zn2+ and Pb~(2+) is longer than that of the typical perovskite phase of Pb(Zn_(1/3)Nb_(2/3))O_3.This indicates the key role of BaTiO_3 in decreasing the steric hindrance of Pb~(2+) lone pair, and the mutual interactions between Pb~(2+) lone pair and Zn2+ and the formation energy is seen to decrease. This finding of the formation energy and local structure configuration relationship can further extend a fundamental understanding of the role of BaTiO_3 in stabilizing the perovskite phase in PbZn_(1/3)Nb_(2/3)O_3-based materials,which in turn will lead to an improved preparation technique for desired electrical properties.     

Raman and optical absorption spectroscopic investigation of Yb-Er codoped phosphate glasses containing SiO_2

Yb-Er codoped Na2O-Al2O3-P2O5-xSiO2 glasses containing 0 - 20 mol% SiO2 were prepared successfully. The addition of SiO2 to the phosphate glass not only lengthens the bond between pS＋ and non-bridging oxygen but also reduces the number of P=O bond. In contrast with silicate glass in which there is only four-fold coordinated Si4＋, most probably there coexist [SiO4] tetrahedron and [SiO6] oetahedron in our glasses. Within the range of 0 - 20 mol% SiO2 addition, the stimulated emission cross-section of Era＋ ion only decreases no more than 10%. The Judd-Ofelt intensity parameters of Er3＋, Ω2 does not change greatly, but Ω4 and Ω6 decrease obviously with increasing SiO2 addition, because the bond between Er3＋ and O2- is more strongly eovalently bonded.     

Radiation Losses in the Microwave X Band in Al-Cr Substituted Y-Type Hexaferrites

We present a study on radiation losses in the microwave X band in Al-Cr substituted Y-type hexaferrites,namely Ba_2 Mg_2 Al_(x/2)Cr_(x/2)Fe_(12-x)O_(22)(x= 0, 0.5 and 1.0). The study is performed by means of a vector network analyzer, Fourier transform infrared spectroscopy, a vibrating sample magnetometer and x-ray powder diffraction.Ba_2 Mg_2 Fe_(12)O_(22) hexaferrite shows radiation loss of-37.25 dB(99.999% loss) at frequency 9.81 GHz, which can be attributed to its high value of saturation magnetization, i.e., 22.08 emu/g. Moreover, we obtain that magnetic properties have strong influence on the radiation losses.     

Nd-Fe-B永磁合金腐蚀产物的拉曼光谱研究

本文应用拉曼光谱法,研究了Nd—Fe—B永磁合金在NaCl,NaHSO_4水溶液及大气环境中的腐蚀产物组成及其变化。测定结果表明,Nd—Fe—B合金大气腐蚀产物的主要组成为:Nd(OH)_3,γ—FeOOH,α—FeOOH,Fe_3O_4及B_2O_3,在NaCl溶液中则有NdCl_3生成。在不同PH值的NaHSO_4溶液中,锈层的组成有所变化。据此,对Nd—Fe—B合金的腐蚀过程与机理进行了探讨。     

抛光对光纤连接器回波损耗的影响

分别选用氧化铝和氧化硅材料的抛光砂纸,在施加不同抛光压力、抛光时间,以及抛光助剂等工艺条件下,实验研究了抛光对连接器回波损耗的影响规律。通过实验发现:氧化铝砂纸干式抛光使光纤连接器的回波损耗仅保持在32～38dB之间;氧化硅砂纸干式抛光会造成光纤端面污损,使得连接器的回波损耗降低到20dB以下;氧化铝与氧化硅砂纸湿式抛光均可使光纤连接器的回波损耗提高到45～50dB,但氧化铝砂纸湿式抛光会造成80nm以上的光纤凹陷。因此,制作高回波损耗的光纤连接器应优先选用氧化硅砂纸湿式抛光工艺,抛光时间应控制在20～30s。     

Extended damage range of(Al_(0.3)Cr_(0.2)Fe_(0.2)Ni_(0.3))_3O_4 high entropy oxide films induced by surface irradiation

Irradiation makes structural materials of nuclear reactors degraded and failed. However, the damage process of materials induced by irradiation is not fully elucidated, mostly because the charged particles only bombarded the surface of the materials(within a few microns). In this work, we investigated the effects of surface irradiation on the indirect irradiation region of the(Al_(0.3)Cr_(0.2)Fe_(0.2)Ni_(0.3))_3O_4 high entropy oxide(HEO) films in detail by plasma surface interaction. The results show that the damage induced by surface irradiation significantly extends to the indirect irradiation region of HEO film where the helium bubbles, dislocations, phase transformation, and the nickel oxide segregation were observed.