High frequency magnetic properties and intergranule interaction of nano-granular films with high resistivity and high permeability

In order to get magnetic films with high permeability and high resistivity for applications in high frequency devices, (Fe65Co35)x(SiO2)1-x nano-granular films with low metal volume fraction were fabricated by radio frequency magnetron sputtering, and excellent soft magnetic properties have been acquired by annealing the sample with x = 0.38 at 260 degrees C in a magnetic field. The real part micro' of complex permeability is larger than 100 when frequency f is lower than 0.7 GHz, and the ferromagnetic resonance frequency f(r) is as high as 1.8 GHz. More interestedly, the resistivity of this sample reaches 13.4 momega x cm, 4 orders higher than that of pure FeCo alloy. Ferromagnetic resonance experiment and deltam-H curve study were employed to elucidate the mechanism of soft magnetic properties. The results reveal that the intergranule exchange coupling plays an important role in realizing good soft magnetic properties for metal-insulator granular films.     

Studies of the magnetic field intensity on the synthesis of chitosan-coated magnetite nanocomposites by co-precipitation method

Chitosan-coated magnetite nanocomposites (Fe₃O₄/CS) were prepared under different external magnetic field by co-precipitation method. The effects of the magnetic field intensity on phase composition, morphology and magnetic properties of the Fe₃O₄/CS nanocomposites were investigated by X-ray diffractometer (XRD), Fourier transform infrared analysis (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The results showed that the intensity of the magnetic field in the co-precipitation reaction process did not result in the phase composition change of the magnetic chitosan but improved the crystallinity of magnetite. The morphology of Fe₃O₄/CS nanocomposites was greatly changed by the magnetic field. It was varied from random spherical particles to chain-like cluster structure and rod-like cluster structure with the magnetic field intensity increased in the synthetic process. The VSM results indicated that all the products had excellent superparamagnetic properties regardless of the presence or the absence of the magnetic field, and the saturation magnetization values of the Fe₃O₄/CS nanocomposites were significantly improved by the magnetic field.     

Spherical porous hydroxyapatite granules containing composites of magnetic and hydroxyapatite nanoparticles for the hyperthermia treatment of bone tumor

Spherical porous granules of hydroxyapatite (HA) containing magnetic nanoparticles would be suitable for the hyperthermia treatment of bone tumor, because porous HA granules act as a scaffold for bone regeneration, and magnetic nanoparticles generate sufficient heat to kill tumor cells under an alternating magnetic field. Although magnetic nanoparticles are promising heat generators, their small size makes them difficult to support in porous HA ceramics. We prepared micrometer-sized composites of magnetic and HA nanoparticles, and then supported them in porous HA granules composed of rod-like particles. The spherical porous HA granules containing the composites of magnetic and HA nanoparticle were successfully prepared using a hydrothermal process without changing the crystalline phase and heat generation properties of the magnetic nanoparticles. The obtained granules generated sufficient heat for killing tumor cells under an alternating magnetic field (300 Oe at 100 kHz). The obtained granules are expected to be useful for the hyperthermia treatment of bone tumors.     

Indirect Susceptibility Mapping of Thin-Layer Samples Using Nuclear Magnetic Resonance Imaging

We measured and imaged magnetic field distributions of thin layers (2-D objects with negligible thickness) of biological and physical samples, by using nuclear magnetic resonance (NMR). The image represents the magnetic susceptibility distribution in the sample. We used a standard gradient echo imaging method, susceptible to magnetic field homogeneity, for detection. Since the physical and biological samples we investigated do not generate any NMR signal, we used a homogeneous phantom reference - a container filled with water - as a medium. The image acquired by this method is actually a projection of the sample properties onto the homogeneous phantom. The method can be applied in nanotechnology, microelectronics, and especially in the biological and medical sciences.     

制备态(Fe88Zr7B5)100-xCux非晶薄膜的磁特性和巨磁阻抗

采用射频溅射法在单晶Si衬底上制备了Fe88Zr7B5)100-xCux(x=0、1、2、3、4)非晶薄膜样品,对其软磁特性和巨磁阻抗(GMI)变化行为进行了测量和研究。测量结果显示,加入适量Cu元素(x=3)的制备态样品具有极好的软磁性能和GMI效应,此样品的矫顽力仅有56A/m,在13MHz的频率下,最大有效磁导率(μe)比和GMI比分别为42.5%和17.0%。研究发现,制备态样品的电阻R、电抗X和阻抗Z都随Cu含量的增加而下降。X=0、4两个样品的μe、R、X、Z对外加磁场响应极不敏感,只有软磁性能优异的x=3样品的μe、R、X、Z才显示出对外加磁场响应敏感,因而有显著的GMI效应。样品拥有高的磁导率、小的矫顽力和低的电阻率是获得大GMI效应的本质条件。     

Zirconium Alloys for Orthopaedic and Dental Applications

Zirconium alloys for biomedical applications are receiving increasing attention due to their two unique properties: 1) the formation of an intrinsic bone‐like apatite layer on their surfaces in body environments, and 2) better compatibility with magnetic resonance imaging (MRI) diagnostics due to their low magnetic susceptibility, as well as their overall excellent biocompatibility, mechanical properties, and bio‐corrosion resistance. In particular, since both of the MRI quality and speed depend on magnetic field strength, there is a compelling drive for use of high magnetic field strength (>3 Tesla) MRI systems. This paper provides a comprehensive review of the characteristics of commercially pure (CP) Zr and Zr‐based alloys as orthopaedic and dental implant materials. These include their 1) phase transformations; 2) unique properties including corrosion resistance, biocompatibility, magnetic susceptibility, shape memory effect, and super‐elasticity; 3) mechanical properties; 4) current orthopaedic and dental applications; and 5) the d‐electron theory for Zr alloy design and novel Zr‐alloys. The mechanical properties of Zr‐based bulk metallic glasses (BMGs) and their application as implant materials are also assessed. Future directions for extending the use of Zr‐alloys as orthopaedic and dental implants are discussed.

     

磁场对PET表面碳氟等离子体改性的影响：II.磁场位形与PET？…

研究了不同磁场条件下碳氟等离子体对涤纶（ＰＥＴ）表面改性的影响,通过变角Ｘ光电子能谱（ＸＰＳ）方法研究改性后ＰＥＴ表面结构和性质的变化,并探讨了磁场对碳氟等离子体改性的影响,实验结果表明,在磁场存在的条件下,碳氟等离子体处理ＰＥＴ的表面结构和性质的变化,依赖于磁场的强度而不是磁场的分布,磁场强度的增强,导致了改性后ＰＥＴ表面Ｆ／Ｃ比的提高及等离子体事物或蚀程度的加强。     

CFRP层间碳纳米管定向喷涂工艺及断裂韧性研究

为了提高碳纤维增强树脂基复合材料(CFRP)层间性能,采用共沉淀法在碳纳米管上接枝磁性Fe₃O₄粒子,通过定向喷涂工艺使磁性碳纳米管(Fe₃O₄-MWCNTs)在碳纤维表面取向一致,并喷涂树脂加以固定,形成碳纤维-定向碳纳米管-树脂界面,采用真空辅助树脂渗透成形(Vacuum assisted resin infusion, VARI)工艺制备层间性能优异的Fe₃O₄-MWCNTs层间定向增强CFRP。试验结果表明,喷涂树脂可改善和巩固定向喷涂工艺。与未加磁场喷涂工艺相比,当Fe₃O₄-MWCNTs的质量分数为0.3wt%时,采用定向喷涂工艺试件的I型层间断裂韧性(G_IC)提升幅度最大,G_IC提高了37.7%。断面形貌分析表明其增强机制以树脂的塑性变形、Fe₃O₄-MWCNTs棒状聚集体的拔出及树脂塑性孔洞的生长为主。该研究为具有可控定向行为的磁性碳纳米管改性CFRP层间力学性能提供了新思路与方法。      

可注射磁性液固相变材料用于骨肉瘤的磁共振成像与低温磁热治疗研究

过高温可诱发肿瘤周围正常组织产生炎症以及热辐射损伤。因此研发一种能在相对较低温度下(例如43 ℃)即可实现肿瘤细胞高致死率的磁性材料对于磁热治疗的临床应用至关重要。本研究聚焦低温、安全、高效磁热疗, 选取FDA批准的液固相变材料聚乳酸-羟基乙酸(PLGA)为原料, 装载一步温和还原法制备得到的超顺磁性氧化铁纳米颗粒, 用于磁共振成像和磁热升温; 进一步在PLGA中装载热休克蛋白HSP90的小分子抑制剂-表没食子儿茶素没食子酸酯(EGCG), 抑制机体受热保护功能, 实现较低温度下杀死肿瘤细胞。体外实验结果表明, 制备得到的超顺磁性氧化铁纳米颗粒不仅拥有良好的T₂加权成像性能, 还具有优良的磁热升温性能。所制备的PLGA/Fe₃O₄/EGCG复合材料在交变磁场下控制升温至43 ℃并保温40 min后发现肿瘤细胞死亡率达70%, 显示出针对骨肉瘤低温磁热治疗的良好潜力。这种可注射磁热相变材料将为骨肉瘤的治疗提供新的思路和材料支撑。     

Adaptive iron-based magnetic nanomaterials of high performance for biomedical applications

With unique physicochemical properties and biological effects,magnetic nanomaterials(MNMs)play a crucial role in the biomedical field.In particular,magnetic iron oxide nanoparticles(MIONPs)are approved by the United States Food and Drug Administration(FDA)for clinical applications at present due to their low toxicity,biocompatibility,and biodegradability.Despite the unarguable effectiveness,massive space for improving such materials'performance still needs to be filled.Recently,many efforts have been devoted to improving the preparation methods based on the materials'biosafety.Besides,researchers have successfully.regulated the performance of magnetic nanoparticles(MNPs)by changing their sizes,morphologies,compositions;or by.aggregating as-synthesized MNPs in an orderly arrangement to meet various clinical requirements.The rise of cloud computing and artificial intelligence techniques provides novel ways for fast material characterization,automated data analysis,and mechanism demonstration.In this review,we summarized the studies that focused on the preparation routes and performance regulations of high-quality MNPs,and their special properties applied in biomedical detection,diagnosis,and treatment.At the same time,the future.development of MNMs was also discussed.     

Si含量对纳米晶Fe_(87-x)Cu_1Nb_3Si_xB_9合金磁性能的影响

研究了Si含量对Fe87-xCu1Nb3SixB9合金经不同方式退火后磁性能的影响。结果表明:随Si含量的增加,Fe87-xCu1Nb3SixB9合金经普通退火后软磁性能逐渐得到优化;经磁退火后可感生出单轴磁各向异性,且磁退火特征随Si含量的增加而逐渐明显。根据横磁退火实验结果计算出的感生磁各向异性值Ku,则由26.7J/m3(Si=9.5at%)降低至14.1J/m3(Si=13.5at%)。由实验数据的分析认为Fe87-xCu1Nb3SixB9合金在高Si含量时经普通退火或纵磁退火后呈现优异的软磁特性,归因于析出的α-Fe(Si)相晶粒具有小的磁晶各向异性K1,从而导致合金具有更低的有效磁各向异性常数K所至。     

Simultaneous Delivery of Doxorubicin and EZH2-Targeting siRNA by Vortex Magnetic Nanorods Synergistically Improved Anti-Tumor Efficacy in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC), one of the most aggressive types of breast cancer, currently lacks a targeted therapy and has a high clinical recurrence rate. The present study reports an engineered magnetic nanodrug based on Fe₃O₄ vortex nanorods coated with a macrophage membrane loaded with doxorubicin (DOX) and Enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2) siRNA. This novel nanodrug displays excellent tissue penetration and preferential tumor accumulation. More importantly, it significantly increases tumor suppression compared to chemotherapy, suggesting the synergistic activity of the combination of doxorubicin and EZH2-inhibition. Importantly, owing to tumor-targeted delivery, nanomedicine shows an excellent safety profile after systemic delivery, unlike conventional chemotherapy. In summary, chemotherapy and gene therapy are combined into a novel magnetic nanodrug carrying doxorubicin and EZH2 siRNA, which shows promising clinical application potential in TNBC therapy.     

General synthesis of high-performing magneto-conjugated polymer core–shell nanoparticles for multifunctional theranostics

Recently,increasing attention has been paid to magneto-conjugated polymer core-shell nanopartides (NPs) as theranostic platforms.However,the utilization of surfactants and extra oxidizing agents with potential toxidty in synthesis,the lack of general methods for the controlled synthesis of various kinds of magnetic NP (MNP)@conjugated polymer NPs,and the difficulty of obtaining balanced magneto-optical properties have greatly limited the applications of magneto-conjugated polymers in theranostics.We developed an in situ surface polymerization method free of extra surfactants and oxidizing agents to synthesize MNP@polypyrrole (PPy) NPs with balanced,prominent magneto-optical properties.MNP@PPy NPs with an adjustable size,different shapes,and a controlled shell thickness were obtained using this method.The method was extended to synthesize other MNP-conjugated polymer core-shell NPs,such as MNP@polyaniline and MNP@poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS).We discuss the formation mechanism of the proposed method according to our experimental results.Finally,using the optical and magnetic properties of the obtained MNP@PEDOT:PSS NPs,in vivo multimodal imaging-guided hyperthermia was induced in mice,achieving an excellent tumor-ablation therapeutic effect.Our work is beneficial for extending the application of MNP-conjugated polymer core-shell NPs in the biomedical field.     

New design for a high performance optically pumped cesium beam tube

An optically pumped cesium beam resonator has been designed including three successive magnetic field regions. The optical interactions take place in the first and third regions, where the magnetic field has the required value of 3x10(-5) T. The microwave interaction occurs in the intermediate region, where the value of the C-field is typically set to 4x10(-6) T. It has been verified that the magnetic field profile along the cesium beam does not induce Majorana transitions. Using a single laser diode emitting at 852 nm with a linewidth of about 30 MHz, the resonator gives an excellent amplitude signal to noise ratio equal to 20000 in a 1-Hz bandwidth.     

Biocompatible nanoclusters of <Emphasis Type="Italic">O</Emphasis>-carboxymethyl chitosan-coated Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles: synthesis,characterization and magnetic heating efficiency

In this work, we developed a polymer encapsulation of Fe₃O₄ nanoparticles as a core–shell nanocluster with different sizes to investigate the cluster structure effect on their magnetic properties and magnetic heating behavior. Well-dispersed nanoclusters of O-carboxymethyl chitosan-coated Fe₃O₄ nanoparticles were synthesized by microwave-assisted co-precipitation. The cluster sizes were tunable by varying the concentration of polymers used during synthesis. Nanoclusters present superparamagnetic behavior at room temperature with a reduction in saturation magnetization as a consequence of coating layer. The shift of blocking temperature to the higher value with increasing clusters size shows the stronger magnetic interaction in larger magnetic clusters. In a low alternating magnetic field with frequency of 178 Hz and amplitude of 103 Oe, nanoclusters offer a high heating efficiency. A maximum specific absorption rate of 204 W/g is observed in the sample with hydrodynamic size of 53 nm. In vitro cytotoxicity analysis performed on HeLa cells verified that nanoclusters show a good biocompatibility and can be an excellent candidate for applications in hyperthermia cancer treatment.     

Nanomagnetic planar magnetic resonance microscopy "lens"

The achievement of three-dimensional atomic resolution magnetic resonance microscopy remains one of the main challenges in the visualization of biological molecules. The prospects for single spin microscopy have come tantalizingly close due to the recent developments in sensitive instrumentation. Despite the single spin detection capability in systems of spatially well-isolated spins, the challenge that remains is the creation of conditions in space where only a single spin is resonant and detected in the presence of other spins in its natural dense spin environment. We present a nanomagnetic planar design where a localized Angstrom-scale point in three-dimensional space is created above the nanostructure with a nonzero minimum of the magnetic field magnitude. The design thereby represents a magnetic resonance microscopy "lens" where potentially only a single spin located in the "focus" spot of the structure is resonant. Despite the presence of other spins in the Angstrom-scale vicinity of the resonant spin, the high gradient magnetic field of the "lens" renders those spins inactive in the detection process.     

锶铁氧体负载磁性酸催化剂的制备和性能研究

首次以具有优异磁学特性的锶铁氧体（Sr-Fe12O19）粒子为磁性基体,负载硫酸制备磁性催化剂SO42-/SrFe12O19。利用XRD、BET、VSM等表征手段,结合催化合成产物的表征,研究了磁性催化剂的表面性质和催化性能。结果表明制备出的SO42-/SrFe12O19的饱和磁化强度较大,易于分离。催化合成酯的研究发现催化剂重复使用6次,其作用下的酯化率仍达74%,表现出良好的回收效果。     

A Liquid‐Metal‐Based Magnetoactive Slurry for Stimuli‐Responsive Mechanically Adaptive Electrodes

Electrical communication between a biological system and outside equipment allows one to monitor and influence the state of the tissue and nervous networks. As the bridge, bioelectrodes should possess both electrical conductivity and adaptive mechanical properties matching the target soft biosystem, but this is still a big challenge. A family of liquid‐metal‐based magnetoactive slurries (LMMSs) formed by dispersing magnetic iron particles in a Ga‐based liquid metal (LM) matrix is reported here. The mechanical properties, viscosity, and stiffness of such materials rapidly respond to the stimulus of an applied magnetic field. By varying the intensity of the magnetic field, regulation within a factor of 1000 of the Young's modulus from ≈kPa to ≈MPa, and the ability to reach GPa with more dense iron particles inside the LMMS are demonstrated. With the advantage of high conductivity of the LM matrix, the functions of the LMMS are not only limited to the soft implanted electrodes or penetrating electrodes in biosystems: the electrical response based on the LMMS electrodes can also be precisely tuned by simply regulating the applied magnetic field.     

锌锰掺杂Fe3O4纳米颗粒的尺寸可控合成

锌锰掺杂的Fe₃O₄纳米颗粒具有优异的磁性能, 在生物医药领域有广泛的应用前景。磁性纳米颗粒的尺寸与其磁学性质以及生物磁性应用密切相关。因此, 为了适应不同生物应用对尺寸的需求, 研究其尺寸调控具有重要的意义。在本研究中, 我们采用高温热分解法, 通过加入还原剂1,2-十六烷二醇, 改变金属前躯体和回流时间成功制备了尺寸在5~20 nm的锌锰掺杂Fe₃O₄纳米颗粒。研究发现:强还原剂1,2-十六烷二醇的加入有利于合成小尺寸的纳米颗粒, 而以金属氯化物作为金属前躯体和延长回流时间可以进一步合成更大尺寸的纳米颗粒; 纳米颗粒的饱和磁化强度随着尺寸的增大而增大。     

An in vitro and in vivo investigation of the biological behavior of a ferrimagnetic cement for highly focalized thermotherapy

The cancer treatment by local hyperthermia, using a high frequency electromagnetic field is an extensively studied subject. For this propose it was developed a ferrimagnetic cement (FC) to be injected directly into the tumor. In this study it was determined the FC injectability, its capability to generate heat when placed within a magnetic field and its interaction with a modified simulated body fluid using SEM/EDS and XRD. The FC biological response was assessed by the intramuscular implantation in rats and histological analysis of the surrounding tissues. The results suggest that FC can be injected directly into the tumor, its temperature can be increased when exposed to a magnetic field and the surface of the immersed samples quickly becomes coated with precipitate denoting its ionic change with the surrounding medium. The histological analysis revealed a transient local inflammatory reaction, similar to the control material, only slightly more abundant during the first weeks, with a gradual decrease over the implantation time. Based on these results, we concluded that FC might be useful for highly focalized thermotherapy, with a good potential for clinical use.