Untersuchung zur Schichtfolge eines Multilayerschichtsystems NiZn Ferrit / Si bzw. SiO2 für Höchstfrequenzleiterplatten im Frequenzbereich größer 1000 MHz

Simulation of Layer – Sequence of Ni‐Zn Ferrite Thin Films and Multilayers for EMC Applications > 1000 MHz NiZn ferrite multilayer have attracted much attention as materials with unique properties. One of these properties is enhanced microwave absorption. This gives a possibility to product absorption electromagnetic covers ( EMC ) with ultrathin thickness. The Electromagnetic Compatibility absorption of NiZn Ferrite polycristalline sample is 0,6 dB in the rf‐ range.     

自蔓延高温合成软磁铁氧体粉的研究进展

简要介绍了自蔓延高温合成技术和热力学判据,评论了此合成技术的新进展和存在的问题,综述了利用此方法制备MnZn、NiZn和MgZn铁氧体材料的制备工艺及其应用研究现状,重点分析讨论了软磁铁氧体的原料配方、合成工艺和磁特性.研究表明,通过控制工艺参数和添加剂的合理使用,SHS法制备铁氧体粉体具有更好的烧结活性和纯度,适合于大规模的工业生产.     

基于人工神经网络的NiZn铁氧体结构不敏感性能的预测模型

为了系统研究配方对铁氧体电磁性能的影响,制备了一系列Mn2 、Ge4 和Si4 替代的NiZn铁氧体材料,建立了铁氧体配方与结构不敏感性能之间的人工神经网络预测模型.利用所建立的模型研究了ZnO对NiZn铁氧体3个结构不敏感性能居里温度、磁饱和强度及介电常数的影响规律,以及多个组分的交互作用.结果表明:模型的预测结果与实验结果吻合良好,二者的相对误差较小.ZnO含量的增加会导致铁氧体居里温度下降,但会提高饱和磁化强度和介电常数.NiO和ZnO的交互作用对铁氧体的结构不敏感性能影响明显.利用模型得到的铁氧体性能-成分等值线图对寻找最佳配方有较高参考价值.     

Low-temperature <Superscript>1</Superscript>H-NMR spectroscopic study of doxorubicin influence on the hydrated properties of nanosilica modified by DNA

The effect of the anticancer drug—doxorubicin (Dox) on hydration properties of a nanocomposite material deposited on silica and modified by small amount of DNA (0.6 wt%) was studied by means of ¹H NMR spectroscopy at low temperatures (in the range of 200–280 K). Signals of either weakly (WAW) or strongly (SAW) associated water, as well as water associated with electrondonor groups of the composite surface (ASW), were observed. The findings reveal that, depending on the temperature and the composition of the dispersion medium, fast molecular exchange takes place between different forms of interphase water. The presence of Dox (0.1–0.2 wt%) in the dispersion medium leads to change of the relative concentrations of different forms of water.     

Preparation of single-crystal <Superscript>29</Superscript>Si

A process has been developed for the preparation of single-crystal ²⁹Si from ²⁹Si-enriched silane. A silicon single crystal has been grown with a ²⁹Si content over 99.9 at %. The oxygen and carbon concentrations in the crystal are under 1 × 10¹⁶ cm⁻³, and its resistivity exceeds 1 kΩ cm.     

Role of Mg<Superscript>2+</Superscript>, Sr<Superscript>2+</Superscript>, and F<Superscript>–</Superscript> ions in octacalcium phosphate crystallization

We have synthesized octacalcium phosphate (OCP) in the presence of inorganic additives (magnesium, strontium, and fluoride ions) and studied the composition, morphology, thermal stability, and dynamic dissolution of the samples thus obtained. It has been shown that, in addition to OCP, magnesium and strontium ions favor the formation of brushite and hydroxyapatite (HA), whereas fluoride ions favor the formation of HA and fluorohydroxyapatite (FHA). We have proposed a process for the preparation of powder materials whose resorption kinetics in corrosive liquid media are corrected by adding dopants capable of activating the dissolution process.     

Ce<Superscript>3+</Superscript> and Eu<Superscript>2+</Superscript> luminescence in calcium and strontium aluminates

Compound CaAl₄O₇ (CA4), SrAl₄O₇ (SA4), CaAl₁₂O₁₉ (CA12) and SrAl₁₂O₁₉ (SA12) have been synthesized by using single step combustion method. The phosphors have been characterized by XRD, SEM and PL techniques. Both CA4 and SA4 possess monoclinic crystal structure whereas CA12 and SA12 possess hexagonal structure. Effects of crystal symmetry on the emission spectrum have been studied by doping the samples with Ce³⁺ and Eu²⁺ ions. The luminescence properties of Ce³⁺ and Eu²⁺ in these hosts is discussed on the basis of their covalent character and the crystal field splitting of the d-orbital of dopant ions. The spectroscopic properties, crystal field splitting, centroid shift, red shift and stokes shift have been studied. Spectroscopic properties of Eu²⁺ ions have been accurately predicted from those of Ce³⁺ ions in the same host. Most importantly experimental results were matched excellently with the calculated results. The preferential substitution of Ce³⁺ and Eu²⁺ at different Ca²⁺, Sr²⁺ crystallographic sites have been discussed. The dependence of emission wavelengths of Ce³⁺ and Eu²⁺ on the local symmetry of different crystallographic sites was also studied by using Van Uitert’s empirical relation. Differences in the emission spectrum of these samples have been observed despite their similar crystal structures and space group. Possible reasons have been discussed.     

Green synthesis of white-light-emitting ZnSe:Eu<Superscript>2+</Superscript>, Mn<Superscript>2+</Superscript> quantum dots in an aqueous solution

High-quality ZnSe:Eu, Mn quantum dots (QDs) with white light emitting were synthesized via a green preparation method in an aqueous solution using thioglycolic acid as a stabilizing agent. The composition of the QDs could be flexibly controlled by varying the amount of Eu or Mn cation. The effects of reflux time and Eu²⁺ ion dopant concentration on the luminescence properties were systematically investigated. The obtained QDs were characterized by photoluminescence spectrometry, X-ray powder diffraction, and high-resolution transmission electron microscopy. The proposed method formed cubic ZnSe:Mn²⁺, Eu²⁺ QDs with the maximum emission peak at 460 and 580 nm. In the optimal condition, the quantum yields of ZnSe:Mn²⁺, Eu²⁺ QDs could reach 27.68%. The CIE color coordinates were (0.328, 0.334), which agreed with those of pure white light (0.33, 0.33). The results verified that the ZnSe:Mn²⁺, Eu²⁺ QDs exhibited potential in light-emitting diode applications.     

EPR and SQUID studies on magnetic properties of SiO2-doped Ni–Zn ferrite nanocomposites

Effects of the silica content and temperature on the magnetic properties of Ni_0.5Zn_0.5Fe₂O₄/SiO₂ nanocomposites have been studied by electron paramagnetic resonance (EPR) and superconducting quantum interference device (SQUID) technique. The content of TEOS in the starting solution affects the interaction between NiZn ferrite and silica, and then determines the particle size and the EPR properties. In addition, the SQUID properties of the composites were sensitive to particle size. It was observed that the saturation magnetization (M_s), remnant magnetization (M_r) and initial susceptibility (χ_i) decreased with increasing SiO₂ content.     

Nanocrystalline PbIn<Subscript>0.5</Subscript>Nb<Subscript>0.5</Subscript>O<Subscript>3</Subscript> ceramics and its properties

A ferroelectric relaxor PbIn_0.5Nb_0.5O₃ (PIN) ceramics has been obtained using a modified ceramic technology, with the sintering stage preceded by compression and shear straining of the synthesized charge in Bridgman anvils. The dimensions of ceramic grains after this pretreatment are spread over a range from 100 to 1250 nm. A comparative investigation of the properties of PIN ceramics obtained using the standard and modified technology showed that the proposed mechanical action at the charge preparation stage can be used for controlled modification of the properties of ferroelectric ceramics.     

Determination of radiochemical and radionuclide purity of a <Superscript>131</Superscript>I preparation

The radiochemical purity of a ¹³¹I preparation (the iodide fraction) was determined by ascending paper chromatography using a mixture of sodium iodide, sodium iodate, and sodium carbonate as a carrier and aqueous methanol as an eluent. The chromatogram was developed with a scanning β-ray spectrometer. The radiochemical purity of ¹³¹I determined by this procedure was 99.98%. The radionuclide purity of the ¹³¹I preparation was measured on a γ-ray spectrometer with an ultrapure Ge detector. The content of radionuclide impurities estimated from their detection limits in the ¹³¹I preparation isolated from TeO₂ in 3–4 days after its irradiation in a reactor was no more than 0.03%. The ⁷⁵Se content in the preparation aged for 6–7 months (which corresponds to a decrease in the ¹³¹I activity by a factor of 10⁶–10⁷ owing to decay) corresponds to 2 × 10^?6% of the activity by the end of irradiation.     

Influence of Mn<Superscript>2+</Superscript> on the up-conversion emission performance of Mn<Superscript>2+</Superscript>, Yb<Superscript>3+</Superscript>, Er<Superscript>3+</Superscript>: ZnWO<Subscript>4</Subscript> green phosphors

The Mn²⁺, Yb³⁺, Er³⁺: ZnWO₄ green phosphors are synthesized successfully through the high temperature solid state reaction method. The micro-structure and morphology have been investigated by means of XRD and EDS. The doped concentrations of Mn²⁺, Yb³⁺, Er³⁺ are measured by ICP. The absorption spectra and emission spectra with different doped concentrations of Mn²⁺ are presented to reveal the influence of Mn²⁺ on the green up-conversion performance. Excited with 970 nm LED, the up-conversion emission peak at 547 nm is obtained and the CIE spectra as well as the green light photo are also presented. The results indicate that the Mn²⁺ ions play the role of the luminescence adjustment in the up-conversion process, which can improve the up-conversion green emission intensity effectively. The luminescence adjustment mechanism of Mn²⁺ ions in Mn²⁺, Yb³⁺, Er³⁺: ZnWO₄ green phosphors has been discussed. The crystal parameters of Dq, B and C are calculated to evaluate the energy level split effect.     

Extraction of single <Superscript>71</Superscript>Ge atoms from the gallium target of a Ga-Ge neutrino detector

A method has been developed for the extraction of single ⁷¹Ge atoms from the gallium target of a Ga-Ge neutrino detector. The key features of this chemical process stem from the extremely low content of the element to be extracted in the sample (n × 10⁻²⁷ at %), the large sample weight (up to n × 10³ kg), the limited time available for the extraction and measurement of the extracted atoms (≤20 h), and small permissible loss (≤0.1%) of the target material at high degrees of ⁷¹Ge extraction (≥90%). The method involves forced generation and maintenance of a disperse system of liquid gallium droplets with an oxide surface film in an acid-peroxide solution. The small droplet size ensures a rapid ⁷¹Ge transfer from the bulk target to a small amount of gallium oxide. The ⁷¹Ge passes from the oxide film to the solution, is concentrated, and converts to germane, which is delivered to a proportional counter. We have assessed the completeness of germanium extraction in relation to process conditions. The results, in particular the completeness of extraction, have been verified in experiments with Ga + Ge mixtures at germanium concentrations of 10⁻⁴ and 10⁻¹⁷ to 10⁻¹⁶ wt %. The adequacy of the approaches used to develop the technology of the Ga-Ge detector is supported by satisfactory agreement between the solar neutrino fluxes obtained with gallium and gallium-chloride detectors.     

Preparation and Characterization of Eu<Superscript>3+</Superscript>-Doped Transparent Oxyfluoride Glasses

A process has been proposed for the preparation of oxyfluoride glasses based on the SiO₂–B₂O₃–Bi₂O₃–ZnO–CaF₂ system at various ratios of batch components, and transparent glasses have been obtained at a temperature below 1000°C. According to X-ray diffraction data, all of the glasses are X-ray amorphous. The surface morphology of the glasses has been examined and their glass transition temperatures have been determined. Their local structure has been studied by IR spectroscopy and it has been shown that, independent of composition, the glasses contain complex polyborate anions formed by [BO₃] and [BO₄] groups. Bismuth is incorporated into the glass network to form Bi–O–Si bonds and [BiO₆] network-formers.     

A method for determining the main mechanical properties of soft soils at high strain rates (10<Superscript>3</Superscript>–10<Superscript>5</Superscript> s<Superscript>−1</Superscript>) and load amplitudes up to several gigapascals

A new method has been developed for determining the main laws of the deformation of soft soils under conditions of dynamic loading with amplitudes of up to several gigapascals. The method is based on the results of high-strain-rate tests under uniaxial deformation conditions, which were obtained using a modified Kolsky method and the plane shock wave technique. The possibilities of the proposed method are illustrated by determining the dynamic properties of sand.     

Dielectric and magnetic properties of Ca(Zn<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>)O<Subscript>3</Subscript>/NiZn ferrite composites

Dense Ca(Zn_1/3Nb_2/3)O₃/NiZn ferrite composites with homogeneously fine microstructures were prepared through conventional solid-state method. The powder XRD patterns confirm the coexistence of the two phases. The dielectric properties in the low frequency range (100 Hz–1 MHz) follow the rule of Maxwell–Wagner interfacial polarization. The dielectric and magnetic properties in the high frequency range (10 MHz–1 GHz) are also reported. The results show that this kind of magnetic–dielectric composites could be used in high-frequency communications for the capacitor-inductor integrating devices such as electromagnetic interference filters and antennas.     

SnO<Subscript>2</Subscript>(Au<Superscript>0</Superscript>, Co<Superscript>II,III</Superscript>) nanocomposites: A synergistic effect of the modifiers in CO detection

Nanocrystalline SnO₂ has been synthesized and its surface has been modified with Au⁰ and Co(II, III). The distribution of the modifiers over the nanocomposites has been studied by X-ray diffraction, inductively coupled plasma mass spectrometry, and transmission electron microscopy. The effect of the modifiers on the hydrogen reduction of nanocrystalline SnO₂ has been assessed. The CO sensing properties of the synthesized materials (10 ppm CO in air) have been studied in situ by electrical conductance measurements. The addition of both Au⁰ and Co(II, III) allows the working temperature of the SnO₂-based semiconductor sensor to be lowered to 215°C.     

Synthesis and characterization of aluminum diboride products using <Superscript>27</Superscript>Al, <Superscript>11</Superscript>B NMR and ab initio studies

Understanding different bonding environments in various metal borides provides insight into their structures and physical properties. Polycrystalline aluminum diboride (AlB₂) samples have been synthesized and compared both with a commercial sample and with the literature. One issue that arose is the relative ease with which boron-rich and aluminum deficient phases of aluminum borides can be presented in AlB₂. Here, we report ²⁷Al, ¹¹B nuclear magnetic resonance (NMR) spectroscopy and first-principles calculations on AlB₂ in order to shed light on these different bonding environments at the atomic level and compare the structural and electronic properties of the products of different preparations. Along with the aforementioned, the present study also takes an in-depth look at the nature of the ¹¹B and ²⁷Al nuclear spin–lattice relaxation recovery data for the AlB₂ and other superhard materials. The nuclear spin–lattice relaxation has been measured for a static sample and with magic-angle spinning. The combination of NMR and band structure calculations highlights the synthetic challenges with superhard materials.     

Effect of Ti<Superscript>4+</Superscript>:Sn<Superscript>4+</Superscript> ratio on the phase transition and electric properties of PLZST antiferroelectric ceramics

PLZST antiferroelectric ceramics were synthesized by the modified coprecipitation method. Effect of variations in the Ti⁴⁺:Sn⁴⁺ ratio on phase and properties were evaluated. The XRD patterns show that with the increasing of Ti⁴⁺ content, the structure of ceramics changes from tetragonal phase to rhombohedral phase and this was certified by the P–E hysteresis loops. The temperature dependence of dielectric constant of the ceramics was measured. Low frequency dispersion at room temperature disappeared when the temperature increased and the variation of T_m is not linear with the content of Ti⁴⁺. These unusual behaviors had been interpreted.     

Electrical properties of R-phycoerythrin containing Ag<Superscript>0</Superscript> nanoparticles in its channels

The electrical properties of R-phycoerythrin modified with Ag⁰ nanoparticles (Ag⁰ ? R-PE) as a candidate material for biosensors were studied were studied. Modification was ensured by a known procedure: synthesis of Ag⁰ nanoparticles in R-phycoerythrin channels through the addition of AgNO₃ to an aqueous R-phycoerythrin solution. According to electron microscopy results, the Ag⁰ ? R-PE contains predominantly elongated Ag⁰ nanoparticles 6.2 ± 0.5 nm in length, which form structures similar to rows 20–60 nm in length. The electrical conductivity, dielectric permittivity, and dielectric loss of the Ag⁰ ? R-PE have been measured in the frequency range from 0.01 Hz to 1 MHz. Filling the channels in R-phycoerythrin molecules with Ag⁰ nanoparticles has been shown to increase the alternating current electrical conductivity and dielectric loss of the material at low frequencies by more than 200 times and its dielectric permittivity by 40 times. Ag⁰ nanoparticles increase the direct current conductivity of R-phycoerythrin from 5 × 10^–14 to 2.5 × 10^–11 S/cm. The electrical properties of Ag ? R-PE are comparable to those of conductive polymer composites that contain metallic nanowires and are used in designing multifunctional films and smart materials.