Effect of Chromium on Magnetic Properties of Y2.9Ce0.1Fe5-xCrxO12 Nanoparticles

Y_2.9Ce_0.1Fe_5-xCr_xO₁₂ (x = 0-0.5) nanoparticles were fabricated by a sol-gel method. Samples with particle size ranging from 60 to 64 nm were obtained and their crystalline structures and magnetic properties were investigated by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). Results of VSM show that the saturation magnetization is increased firstly, after decreased with the Cr concentration (x). The saturation magnetization is increased with increasing the particle size.     

Magnetic Properties of Y3Fe5O12 Nanoparticles Doped Bi and Ce Ions

Y_2.9-xCe_0.1Bi_xFe₅O₁₂ (x = 0-0.5) nanoparticles ranging from 58 to 63 nm were fabricated by a sol-gel method, and their crystallite structures and magnetic properties were investigated by X-ray diffraction (XRD), IR spectroscopy, and vibrating sample magnetometer (VSM). Results of VSM show that the saturation magnetization intensity increased with increase in Ce content (0.1), decrease in Bi concentration (x), and increase in particle size of the formulation.     

Synthesis of Poly(DL-Lactide-Co-Glycolide) Nanoparticles with Entrapped Magnetite by Emulsion Evaporation Method

The goal of this study was to synthesize Poly(DL-lactide-Co-glycolide) nanoparticles with entrapped magnetite, of under 100 nm in diameter, for future drug delivery applications. The emulsion evaporation method was selected to form poly(lactide-co-glycolide) (PLGA) nanoparticles with entrapped magnetite (Fe₃O₄) in the polymeric matrix, in the presence of sodium dodecyl sulfate (SDS) as a surfactant. Magnetite, a water-soluble compound, was surface functionalized with oleic acid to ensure its efficient entrapment in the PLGA matrix. The inclusion of magnetite with oleic acid (MOA) into the PLGA nanoparticles was accomplished in the organic phase. Synthesis was followed by dialysis, performed to eliminate the excess SDS, and lyophilization. The synthesized nanoparticles ranged in size from 38.6 to 67.1 nm for naked PLGA nanospheres and from 78.8 to 87.2 nm for MOA-entrapped PLGA nanospheres. The entrapment efficiency ranged from 57.36% to 77.3%.     

Traps identification in silicon nanocrystals memories by low noise technique

This work reports the extraction of oxide traps properties of n-metal–oxide–semiconductor field-effect transistors with W × L = 0.5 × 0.1 μm² using random telegraph signals (RTS) techniques. RTS study of nc-Si has been performed on thin tunnel oxides from 0.8 to 2.0 nm. RTS signals were two or more levels switching events observed on the drain current of transistors with and without nc-Si. The simple two levels RTS₁ noise was observed on samples without nc-Si. On transistors with nc-Si we distinguish two different RTSs (RTS₂ and RTS₃). RTS signal variations with temperature have shown that there's three slow interfacial traps located at E_c — 0.26 eV (trap1), E_c — 0.23 eV (trap2) and E_c — 0.2 eV (trap3). The spatial localization of traps 1, 2 and 3 from the Si–SiO₂ interface are determined using numerical simulations (x_Trap1 ≈ 0.6 nm, x_Trap2 ≈ 0.8 nm and x_Trap3 ≈ 0.4 nm). RTS noise observed on these devices is attributed to traps localized precisely at the interface thermal oxide/deposited control oxide. (RTS₁) noise is attributed to trap1 and (RTS₂, RTS₃) to traps 2 and 3. From RTS analysis in frequency domain, we extract the power spectrum density of the drain current noise (PSD). From these PSDs we have measured the cut-off frequencies of a single trap even at very low frequencies (for RTS₁ noise f_c = 5 Hz (trap1) and for RTS₂ noise f_c1 = 2 Hz (trap2), f_c2 = 130 Hz (trap3)). These results are in good agreement with those obtained by analysis in time domain and confirm the localization of each trap from the Si–SiO₂ interface.     

Thermolysis and Photolysis of C60 Diozonides

Ozonation of C₆₀ in o-xylene produced three C₆₀(O₃)₂ diozonides that were separated from one another and from two C₆₀(O₃)₃ triozonides by High Performance Liquid Chromatography (HPLC). Upon thermolysis at 10, 15, and 16.6°C, each of the diozonides dissociated sequentially, first to a C₆₀O(O₃) oxyozonide, then to a C₆₀O₂ diepoxide. The three diepoxides were stable in solution for at least 3 weeks. The mean lifetimes of the three diozonides were 52 ± 5, 62 ± 6, and 17.3 ± 1.8 min, respectively (all at 15°C). The mean lifetimes of the three oxyozonides were 69.7 ± 0.7 and 58 ± 6 min at 16.6°C, respectively and about 240 min at 10°C. Photolysis of the diozonides yielded two dioxidoannulenes with UV-Vis adsorption maxima at 333 and 332 nm, and what appeared to be an epoxide-oxidoannulene with UV-Vis adsorption maximum at 327 nm. These annulenes were observed to form dimers. We have synthesized and characterized six C₆₀O₂ dioxides, at least three and possibly four of which were hitherto unknown. We report the discovery of oxyozonides that form during the dissociation of diozonides.     

Atmospheric plasma discharge chemical vapor deposition of SnOx thin films using various tin precursors

A series of 0.2–0.6 μm thick SnO_x films were deposited onto borosilicate and sodalime silica glass substrates by atmospheric plasma discharge chemical vapor deposition at 80 °C. SnO_x films deposited from monobutyltin trichloride contained a large percentage of SnCl₂:2H₂O, and therefore were partially soluble in water. SnO_x coatings deposited from tetrabutyltin were not soluble in water or organic solvents, had good adhesion even at growth rates as high as 2.3 nm/s, had high transparency of  90% and electrical resistivity of 10⁷ Ω cm. As-grown tin oxide coatings were amorphous with a small concentration of SnO₂, SnO and Sn crystalline phases as determined by grazing angle X-ray diffraction and X-ray photoelectron spectroscopy measurements. Upon annealing in air at 600 °C the resistivity of SnO_x films decreased to 5–7 Ω cm. Furthermore, optical and X-ray measurements indicated that SnO_x was converted into SnO₂ (cassiterite) with a direct band gap of 3.66 eV. Annealing of as-grown SnO_x films in vacuum at 340 °C led to formation of the p-type conductor SnO/SnO_x. The indirect band gap of SnO was calculated from the optical spectra to be 0.3 eV.     

Transparent conducting F-doped SnO2 thin films grown by pulsed laser deposition

Transparent conducting fluorine-doped tin oxide (SnO₂:F) films have been deposited on glass substrates by pulsed laser deposition. The structural, electrical and optical properties of the SnO₂:F films have been investigated as a function of F-doping level and substrate deposition temperature. The optimum target composition for high conductivity was found to be 10 wt.% SnF₂ + 90 wt.% SnO₂. Under optimized deposition conditions (T_s = 300 °C, and 7.33 Pa of O₂), electrical resistivity of 5 × 10^− 4 Ω-cm, sheet resistance of 12.5 Ω/□, average optical transmittance of 87% in the visible range, and optical band-gap of 4.25 eV were obtained for 400 nm thick SnO₂:F films. Atomic force microscopy measurements for these SnO₂:F films indicated that their root-mean-square surface roughness ( 6 Å) was superior to that of commercially available chemical vapor deposited SnO₂:F films ( 85 Å).     

Nanoscale Magnetic Behavior of C60 Thin Films in Earth Magnetic Field under Polarization Light Influences

Magnetic behavior of C₆₀ thin films in the Earth's magnetic field under polarization light influence is presented. Transformation of magnetic field for two fullerene thin films of different thickness is investigated. Two proton magnetometers were used for these measurements. Samples of 30 nm and 250 nm thickness illustrate a significant change of magnetic field intensity under the influence of polarization light, in range from 3.4 to 12.9 nT, for 200 measurement data per sample.     

Optical and morphological properties of chemically synthesized poly3-octylthiophene thin films

Poly3-octylthiophene (P3OT) was synthesized by direct oxidation of 3-octylthiophene using FeCl₃ as oxidant/catalyst. It was observed that the purity of FeCl₃ affected the molecular weight and polydisparity as well as the degree of regioregularity of the polymer, measured by size exclusion chromatography and by ¹H nuclear magnetic resonance, respectively. Optical absorption properties of the P3OT films were analyzed as a function of solution concentration, the type of the substrates and the mole percentage of the doping agent. Morphology study with atomic force microscopy indicates that the surface roughness and the cluster size of the polymeric films are influenced by the P3OT solution concentration and the percentage molarity of ferric chloride. FeCl₃ doped P3OT films show enlarged clusters compared with the pristine one due to the introduction of FeCl₃ molecules in the original P3OT chains, a phenomenon observed in electrochemically doped heterocyclic conducting polymers reported in the literature.     

中空磁性氧化石墨烯的制备及其对亚甲基蓝吸附性能

用共沉淀法将Fe3O4沉淀在PS微球上并用甲苯去除PS制备出Fe3O4@PS,再用超声将用Hummers法制备的氧化石墨烯包裹在Fe3O4@PS表面制备出中空磁性氧化石墨烯,研究了这种复合材料对模拟亚甲基蓝废水的吸附.结果 表明:在55℃,用中空磁性氧化石墨烯对亚甲基蓝染料吸附60 min达到平衡,最大吸附量为349....     

Recording Resolution and Writability for (Co-Pt)-SiO2/Co-SiO 2 Hard/Soft-Stacked Granular Perpendicular Media

The magnetic properties and recording performance of hard/soft stacked media consisting of a magnetically hard 9-nm-thick (Co-Pt)-SiO ₂ layer underneath a thin (2-3 nm) soft granular layer were studied. Experimental results indicated that an increase in the mean value of saturation magnetization of the soft layer langM_s ^softrang was very effective at improving the recording resolution D₅₀ due to an increase in the slope of magnetization curve alpha. The use of a Co-SiO₂ layer, which has the highest langM_s ^softrang in the present study, resulted in the highest D₅₀ value. It is likely that the increase in alpha was mainly caused by the demagnetization field in grains due to the difference between langM _s ^softrang and the mean value of saturation magnetization of the hard layer, langM_s ^hardrang. Moreover, it was successfully demonstrated that the magnetization reversal of (Co-Pt)-SiO₂/Co-SiO₂ stacked media changed systematically as theoretically predicted on reducing the interfacial exchange coupling by using NiFeCr-SiO₂ or Pt-SiO₂ interlayers. The reduction of remanence coercivity H_r was achieved by controlling the thickness and film composition of the interlayer, moreover, a high-langM_s ^softrang enhanced the H_r reduction. The H_r reduction improved recording writability without degrading D₅₀, the signal to medium noise ratio SN_mR and thermal stability     

Preparation of uniform titania nanocoating on ZnS-based phosphors by a sol–gel process

A sol–gel process has been developed to coat micron-sized ZnS:Cu,Au,Al phosphors with a smooth and uniform layer of amorphous titania having nanosize thickness. The titania nanocoating is based on the hydrolysis and condensation of titanium tetrabutoxide Ti(OBu)₄. Acetylacetone was used to decrease the reactivity of Ti(OBu)₄. The experimental variables such as water concentration, the amount of ZnS particles, and reaction time were investigated. The thickness of the titania nanocoating was homogeneous and can easily be controlled from 20 to 54 nm by adjusting the experimental variables. The as-prepared titania nanocoating was amorphous phase and could be crystallized to anatase phase upon heating at 500 °C in Ar atmosphere.     

Luminescence of composites based on oxide aerogels incorporated in silica glass host matrix

This paper deals with the elaboration and photoluminescence (PL) examination of oxide powder (OP = ZnO, Al₂O₃, SnO₂, TiO₂) incorporated in silica host matrix. OP, in the first step, was prepared by a sol–gel method using supercritical drying of ethyl alcohol. The obtained powder, in a second step, was incorporated in silica aerogel monolith using tetraethylorthosilicate as SiO₂ precursor and ethyl alcohol supercritical conditions for drying. In the third step, silica aerogel containing oxide powders were heated under natural atmosphere at 1200 °C for 2 h to form the composites that exhibited a strong PL bands at Vis–IR range. Photoluminescence excitation (PLE) measurements show different origins of the emission. It was suggested that OH-related radiative centres and non-bridging oxygen hole centres (NBOHCs) defects resulting from thermal treatment and crystallization at the interfaces between OP and silica host matrix, were responsible for the bands at 400–600 and 700–900 nm respectively.     

Mechanical Properties and Thermal Stability of Oxide Eutectic Composites at High Temperatures

New unidirectionally solidified eutectic composites such as Al₂O₃/YAG and Al₂O₃/GdAlO₃(GAP) have been fabricated by unidirectional solidification. The eutectic composites have a microstructure, in which single crystal Al₂O₃ and single crystal complex oxide compounds (YAG or GdAlO₃) are continuously connected and finely entangled in three-dimensions without grain boundaries. The eutectic composites are thermally stable and have the following properties: (1) The flexural strength at room temperature can be maintained almost up to the melting point, (2) In case of Al₂O₃/YAG composite, the compressive flow stress at 1873 K and a strain rate of 10^-4sec is about 13 times higher than that of sintered composites of the same composition, (3) Al₂O₃/YAG composite shows neither weight gain nor grain growth, even upon heating at 1973 K in an air atmosphere for 1000 hours, and (4) The Al₂O₃/GdAIO₃ eutectic composite shows substantial plastic deformation at 1873 K with a flexural yield stress of about 690 MPa, where the plastic deformation occurred by dislocation motion in each phase. Consequently, these composites can be considered for several useful applications such as new aero gas turbines and power generation systems with non-cooled turbine blades at above 1773 K.     

Temperature-independent electron tunneling injection in tris (8-hydroxyquinoline) aluminum thin film from high-work-function gold electrode

We fabricated electron-only tris (8-hydroxyquinoline) aluminum (Alq₃) single-layer devices with a device structure of glass substrate/MgAg anode (100 nm)/Alq₃ layer (100 nm)/metal cathode (100 nm), and systematically varied the work functions (WF) of the metal cathodes from WF = − 1.9 (Cs) to − 2.9 (Ca), − 3.8 (Mg), − 4.4 (Al), − 4.6 (Ag), and − 5.2 eV (Au) to investigate how electron injection barriers at the cathode/Alq₃ interfaces influence their current density–voltage (J–V) characteristics. We found that current densities at a certain driving voltage decrease and the temperature dependence of J–V characteristics of the devices gradually becomes weaker as the work functions of the metal cathodes are decreased. The device with the highest-work-function Au cathode exhibited virtually temperature-independent J–V characteristics, suggesting that a current flow mechanism of this device is mainly controlled by electron tunneling injection at the Au/Alq₃ interface.     

Alkoxide route to La0.5Sr0.5CoO3 epitaxial thin films on SrTiO3

An all alkoxide based sol–gel route was investigated for preparation of epitaxial La_0.5Sr_0.5CoO₃ (LSCO) films on 100 SrTiO₃ (STO) substrates. Films with 20–30 to 80–100 nm thickness were prepared by spin-coating 0.2–0.6 M (metal) solutions on the STO substrates and heat treatment to 800 °C at 2 °C min^− 1, 30 min, in air. The films were epitaxial with a cube-on-cube alignment and the LSCO cell was strained to match the STO substrate of 3.905 Å closely; a and b = 3.894 Å and 3.897 Å for the 20–30 and 80–100 nm films, respectively. The c-axis was compressed to 3.789 Å and 3.782 Å for the 20–30 and 80–100 nm films, respectively, which resulted in an almost unchanged cell volume as compared to polycrystalline film and nano-phase powders prepared in the same way. The SEM study showed mainly very smooth, featureless surfaces, but also some defects. A film prepared in the same way on an -Al₂O₃ substrate was dense and polycrystalline with crystallite sizes in the range 10–50 nm and gave cubic cell dimensions of a_c = 3.825 Å. The conductivity of the ca 30–40 nm thick polycrystalline film was 1.7 mΩcm, while the epitaxial 80–100 nm film had a conductivity of around 1.9 mΩcm.     

Electrochromic properties of nanocrystalline MoO3 thin films

Electrochromic MoO₃ thin films were prepared by a sol–gel spin-coating technique. The spin-coated films were initially amorphous; they were calcined, producing nanocrystalline MoO₃ thin films. The effects of annealing temperatures ranging from 100 °C to 500 °C were investigated. The electrochemical and electrochromic properties of the films were measured by cyclic voltammetry and by in-situ optical transmittance techniques in 1 M LiClO₄/propylene carbonate electrolyte. Experimental results showed that the transmittance of MoO₃ thin films heat-treated at 350 °C varied from 80% to 35% at λ = 550 nm (ΔT =  45%) and from 86% to 21% at λ ≥ 700 nm (ΔT =  65%) after coloration. Films heat-treated at 350 °C exhibited the best electrochromic properties in the present study.     

Low temperature metal oxide film deposition and reaction kinetics in supercritical carbon dioxide

An effective method is developed for low temperature metal oxide deposition through thermal decomposition of metal diketonates in supercritical carbon dioxide (scCO₂) solvent. The rates of Al(acac)₃ (Aluminum acetyl acetonate) and Ga(acac)₃ (Gallium acetyl acetonate) thermal decomposition in scCO₂ to form conformal Al₂O₃ and Ga₂O₃ thin films on planar surfaces were investigated. The thermal decomposition reaction of Al(acac)₃ and Ga(acac)₃ was found to be initialized at  150 °C and 160 °C respectively in scCO₂ solvent, compared to  250 °C and 360 °C in analogous vacuum-based processes. By measuring the temperature dependence of the growth rates of metal oxide thin films, the apparent activation energy for the thermal decomposition of Al(acac)₃ in scCO₂ is found to be 68 ± 6 kJ/mol, in comparison with 80–100 kJ/mol observed for the corresponding vacuum-based thermal decomposition reaction. The enhanced thermal decomposition rate in scCO₂ is ascribed to the high density solvent which effectively reduces the energy of the polar transition states in the reaction pathway. Preliminary results of thin film deposition of other metal oxides including ZrO_x, FeO_x, Co₂O₃, Cr₂O₃, HfO_x from thermal decomposition of metal diketonates or fluorinated diketonates in scCO₂ are also presented.     

Indium Tin Oxide Thin-Film Sensor for Detection of Volatile Organic Compounds (VOCs)

Indium tin oxide (ITO) (In₂O₃ + 17% SnO₂) thin films were grown on glass substrate by direct evaporation method. Two thick gold pads were deposited to take out contacts. The response of these films at different operating temperatures, when exposed to various volatile organic compounds (VOCs) such as methanol, ethanol, butanol, and acetone in the concentration range 200-2500 ppm was evaluated. Additionally, the effect of film thickness on the response charateristics of methanol and acetone was studied. The linearity and sensitivity of the sensors were measured. The ITO thin-film sensors showed a sensitivity of 0.256 ohms/ppm to acetone vapors, which was almost linear in the range 200-2500 ppm. In order to improve sensitivity and selectivity, a thin layer of various metal and metal oxides such as Cu and PbO was deposited on the sensor surface to work as catalytic layer and the effect on the performance of the sensor was studied. The response and recovery times of the sensor were determined for acetone vapors and were found to be 155 sec and 110 sec, respectively.     

络合法制备均匀γ-Fe2O3纳米颗粒@多层石墨烯复合材料研究

采用水热反应中的金属离子络合一步制备均匀超细磁性γ-Fe₂O₃纳米颗粒@多层石墨烯复合材料, 无需对石墨烯进行氧化处理。采用超声法制备多层石墨烯作为基片, 制备方法简单, 石墨烯表面的含氧官能团少。以FeCl₂为反应物, 以DMF(N, N二甲基甲酰胺)和水混合液作为溶剂, 其中DMF能起到络合金属离子的作用。实验研究了乙酸钠、反应温度及填充度对制备产物的影响。采用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)对复合材料进行微结构分析, 采用振动样品磁强计(VSM)测试了复合材料的磁性能。研究结果表明: 利用亚铁离子与DMF形成的络合物与碳环的π-π吸附作用可以在多层石墨烯表面生成铁氧化物。通过控制亚铁离子的氧化速度和氧化铁的生长速度, 在多层石墨烯表面获得了尺寸小于10 nm的均匀γ-Fe₂O₃纳米颗粒, 复合材料具有良好的磁性能。