Acoustic wave in a suspension of magnetic nanoparticle with sodium oleate coating

The ultrasonic propagation in the water-based magnetic fluid with doubled layered surfactant shell was studied. The measurements were carried out both in the presence as well as in the absence of the external magnetic field. The thickness of the surfactant shell was evaluated by comparing the mean size of magnetic grain extracted from magnetization curve with the mean hydrodynamic diameter obtained from differential centrifugal sedimentation method. The thickness of surfactant shell was used to estimate volume fraction of the particle aggregates consisted of magnetite grain and surfactant layer. From the ultrasonic velocity measurements in the absence of the applied magnetic field, the adiabatic compressibility of the particle aggregates was determined. In the external magnetic field, the magnetic fluid studied in this article becomes acoustically anisotropic, i.e., velocity and attenuation of the ultrasonic wave depend on the angle between the wave vector and the direction of the magnetic field. The results of the ultrasonic measurements in the external magnetic field were compared with the hydrodynamic theory of Ovchinnikov and Sokolov (velocity) and with the internal chain dynamics model of Shliomis, Mond and Morozov (attenuation).     

Improving resolution in single-scan 2D spectroscopy

New schemes are introduced that allow one to improve the resolution in the indirect dimension of single-scan ‘ultrafast’ two-dimensional NMR spectra. The methods combine undersampling with band-selective pulses to recover signals that lie outside the detection bandwidth. The efficiency is illustrated for homonuclear total correlation spectroscopy (TOCSY) of quinidine.     

Nano-deformation of a Ni-P coating surface after nanoparticle impacts

Chemical mechanical polishing (CMP) has become a primary planarization technique required for the manufacture of a computer hard disk substrate. In CMP, erosive wear, which is regarded as one of the wear mechanisms underlying the interaction between the abrasive particles and polished surfaces, can occur when materials are removed by the surface collision of particles which are carried by a fluid medium. A fundamental understanding of the process in which nanoparticles impact on the surface of the nickel-phosphorous (Ni-P) coating plated on the computer hard disk substrate is important to the control and preventing of surface defects during CMP. In this study, a cylindrical liquid jet containing de-ionized water and SiO₂ nanoparticles impacts obliquely on the surface of Ni-P coating at a speed of 10 m/s. Microscopic examinations of the impacted surface are performed using a high resolution transmission electron microscope, an atomic force microscope, etc. Experimental results indicate that craters and scratches in the surface have taken place after nanoparticle impacts, and crystal grains in nano-scale and an element phosphorus concentration can be found in the sub-surface layer of the impacted surface.     

Improving performance characteristics of semiconductor sensors based on adsorption SnO2 using photons stimulation

The paper considers the possibility of increasing the sensitivity of semiconductor adsorption sensors using photon laser stimulation of low power. The results of experiments on the detection of vapors of malonic ester to semiconductor sensors manufactured on the basis of tin dioxide with various doping impurities with the use of laser irradiation and without it. The mechanism of photon stimulation was proposed and its effect was examined on the kinetics of adsorption and an increase the indicator effect.     

Ultrafast nonlinear spectroscopy of a single silver nanoparticle

The time‐domain nonlinear spectroscopy of a single silver nano‐object is investigated by combining the spatial modulation linear spectroscopy technique with a high‐sensitivity femtosecond pump–probe setup. The investigated single nanoparticle is first optically characterized for size and shape via quantitative measurement of its linear absorption spectrum, and time‐resolved nonlinear pump‐probe measurements are subsequently performed on the same particle. The breathing mode period of a single nanoparticle measured in the time domain is found to be in good agreement with that inferred by the optically deduced particle characteristics, opening the way of full optical investigation of the acoustic response of the characterized single nanoparticles. Copyright © 2011 John Wiley & Sons, Ltd.     

Analysis of the electronic structure of ZrO2 by Compton spectroscopy

The electronic structure of ZrO₂ is studied using the Compton scattering technique. The first-ever Compton profile measurement on polycrystalline ZrO₂ was obtained using 59.54 keV gamma-rays emanating from the ²⁴¹Am radioisotope. To explain the experimental data, we compute theoretical Compton profile values using the method of linear combination of atomic orbitals in the framework of density functional theory. The correlation scheme proposed by Perdew-Burke-Ernzerhof and the exchange scheme of Becke are considered. The ionic-model-based calculations for a number of configurations, i.e., Zr^+x (O^?x/2)₂ (0 ≤ x ≤ 2), are also performed to estimate the charge transfer on compound formation, and the study supports transfer of 1.5 electrons from Zr to O atoms.     

Optical property of an antireflection coating fabricated by an optimal spin-coating method with a pH-modified SiO_2 nanoparticle solution

An antireflection(AR) coating is fabricated by applying an optimal spin-coating method and a p H-modified SiO_2 nanoparticle solution on a cover glass. Because the p H value of the solution will affect the aggregation and dispersion of the SiO_2 particles, the transmittance of the AR-treated cover glass will be enhanced under optimal fabricated conditions. The experimental results show that an AR coating fabricated by an SiO_2 nanoparticle solution of pH 11 enhances the transmittance approximately by 3% and 5% under normal and oblique incident conditions, respectively. Furthermore, the AR-treated cover glass exhibits hydrophobicity and shows a 65% enhancement at a contact angle to bare glass.     

A reduced model for nanoparticle coating in non-equilibrium plasma

In this Letter, a reduced model is developed based on the full model presented earlier [Yarin et al., J. Appl. Phys. 99 (6) (2006) 064310] for the deposition of amorphous hydrogenated carbon onto particles in a methane–hydrogen plasma. The reduced model is developed based on the assumption that, under certain conditions, chemistry may be decoupled from transport. The results from the reduced model are compared to the results from the full model for particle charge and growth rate of the deposited layer. It is shown that the two models are in good agreement for submicron particles that are of interest in nanoparticle coating in low-pressure plasma reactors. The reduced model is computationally far less expensive as compared to the full model and can be implemented for simulation of a large number of nanoparticles in plasma reactors.     

ATR-FTIR and FT Raman spectroscopy and laser cleaning of old paper samples with foxings

Samples of old paper are studied using ATR-FTIR and FT Raman spectroscopy. It is demonstrated that the methods of laser spectroscopy make it possible to distinguish between the foxing localization regions and the region of homogeneous aging (yellowing). A significant bleaching of old paper and an almost complete erasure of the foxing stains can be reached using laser irradiation. Original Text ? Astro, Ltd., 2009.     

Improving dopant incorporation during femtosecond-laser doping of Si with a Se thin-film dopant precursor

We study the dopant incorporation processes during thin-film fs-laser doping of Si and tailor the dopant distribution through optimization of the fs-laser irradiation conditions. Scanning electron microscopy, transmission electron microscopy, and profilometry are used to study the interrelated dopant incorporation and surface texturing mechanisms during fs-laser irradiation of Si coated with a Se thin-film dopant precursor. We show that the crystallization of Se-doped Si and micrometer-scale surface texturing are closely coupled and produce a doped surface that is not conducive to device fabrication. Next, we use this understanding of the dopant incorporation process to decouple dopant crystallization from surface texturing by tailoring the irradiation conditions. A low-fluence regime is identified in which a continuous surface layer of doped crystalline material forms in parallel with laser-induced periodic surface structures over many laser pulses. This investigation demonstrates the ability to tailor the dopant distribution through a systematic investigation of the relationship between fs-laser irradiation conditions, microstructure, and dopant distribution.     

重力对金纳米颗粒在生物膜表面吸附影响的荧光研究

纳米颗粒在生物膜表面的吸附行为是纳米生物技术领域的重要问题. 采用正、倒置实验, 通过荧光显微镜定量研究了重力对金纳米颗粒在支撑磷脂膜表面吸附的影响. 研究发现, 颗粒尺寸决定其在顶或底层支撑膜表面吸附的差异性. 吸附量的差异与颗粒的沉淀速率和扩散速率之比的对数呈线性关系. 粒径小于14 nm时, 不考虑重力在吸附时的影响; 粒径大于176 nm时, 重力在吸附中占主导地位. 为药物载体研究和理解颗粒－生物膜相互作用提供参考.     

The charge storage characteristics of ZrO2 nanocrystallite-based charge trap nonvolatile memory

ZrO2 nanocrystallite-based charge trap flash memory capacitors incorporating a(ZrO2)0.6(SiO2)0.4 pseudobinary high-k oxide film as the charge trapping layer were prepared and investigated.The precipitation reaction in the charge trapping layer,forming ZrO2 nanocrystallites during rapid thermal annealing,was investigated by transmission electron microscopy and X-ray diffraction.It was observed that a ZrO2 nanocrystallite-based memory capacitor after post-annealing at 850℃ for 60s exhibits a maximum memory window of about 6.8V,good endurance and a low charge loss of ～25% over a period of 10 years(determined by extrapolating the charge loss curve measured experimentally),even at 85℃.Such 850℃-annealed memory capacitors appear to be candidates for future nonvolatile flash memory device applications.     

Fabrication of superhydrophobic coating via a facile and versatile method based on nanoparticle aggregates

Herein, we report a facile and low cost method for the fabrication of superhydrophobic surface via spin coating the mixture of polydimethylsiloxane precursor (PDMS) and silicon dioxide (SiO₂) nanoparticles. The surface hydrophobicity can be well tuned by adjusting the weight percent of PDMS and SiO₂. The water contact angle (WCA) can increase from 106.8 ± 1.2° on PDMS film to 165.2 ± 2.3° on PDMS/SiO₂ coating, companying with a change from adhering to rolling which was observed from tilting angle (TA) characterization. Multi-scale physical structures with SiO₂ nanoparticle aggregates and networks of SiO₂ nanoparticle aggregates are characterized by scanning electron microscopy (SEM) and atomic force microscope (AFM), and they can be observed more clearly from the AFM images treated with software (WSxM). Then the relationship between surface hydrophobicity and structures is further discussed based on Wenzel and Cassie models, indicating that the appearance of networks of nanoparticle aggregates is important in the Cassie state. The superhydrophobic coating can keep the superhydrophobicity at least for one month under environment conditions and readily regenerate after mechanical damage. Additionally, the superhydrophobic coating can be fabricated using other methods including dip coating, spray coating and casting. Thus, a large area of superhydrophobic coatings can be easily fabricated. Therefore the range of possible applications for these facile and versatile methods can be expanded to various actual conditions.     

Improving the sensitivity of a humidity sensor based on fiber bend coated with a hygroscopic coating

A highly sensitive all-fiber humidity sensor is demonstrated. The sensor behaves as a humidity dependent optical switch between 85% and 90% RH. This sensor also offers the advantages of simple structure and low cost and its response is fast and reversible in nature. The typical humidity response of the sensor is suitable for using it as a human breath rate monitor.     

Densification and nanocrystallisation of sol-gel ZrO 2 thin films studied by surface plasmon polariton-assisted Raman spectroscopy

Very thin ZrO ₂ films (few nanometers) have been prepared by sol-gel process. These films were deposited onto a stack of a thin silver layer evaporated on a glass substrate for Surface Plasmons Resonance (SPR) experiments. The first aim of this work is to study the high densification of the sol-gel films followed by the refractive index and thickness accurate measurements at each step of the annealing procedure, using an optical set-up based on SPR. Secondly, SPR excitation coupled with micro-Raman experiment has also been performed to determine the thin films structure depending on layer thickness. Finally, Conventional Transmission Electron Microscopy (CTEM) and High Resolution (HRTEM) studies have been conducted to check and complete Raman spectroscopy results. A discussion compares the optical results and the Transmission Electron Microscopy observations and shows that ultra thin layers structure is strongly depends on films thickness. Received 14 May 2001 and Received in final form 2 January 2002     

Evaluation of nanoparticle emission for TiO<Subscript>2</Subscript> nanopowder coating materials

In this study, nanoparticle emission of TiO₂ nanopowder coated on different substrates including wood, polymer, and tile, was evaluated in a simulation box and measured with a Scanning Mobility Particle Sizer (SMPS) for the first time. The coating process for the substrate followed the instructions given by the supply company. In the simulation box, UV light, a fan, and a rubber knife were used to simulate the sun light, wind, and human contacting conditions. Among the three selected substrates, tile coated with TiO₂ nanopowder was found to have the highest particle emission (22 #/cm³ at 55 nm) due to nanopowder separation during the simulation process. The UV light was shown to increase the release of particle below 200 nm from TiO₂ nanopowder coating materials. The results show that, under the conditions of UV lamps, a fan and scraping motion, particle number concentration or average emission rate decreases significantly after 60 and 90 min for TiO₂/polymer and TiO₂/wood, respectively. However, the emission rate continued to increase after 2 h of testing for TiO₂/tile. It is suggested that nanoparticle emission evaluation is necessary for products with nanopowder coating.     

A novel TiO2 nanoparticles/nanowires composite core with ZrO2 nanoparticles shell coating photoanode for high-performance dye-sensitized solar cell based on different electrolytes

The novel TiO₂ nanopartilces/nanowires (TNPWs) composite with ZrO₂ nanoparticles (ZNPs) shell-coated photoanodes were prepared to fabricate high-performance dye-sensitized solar cell (DSSC) based on different types of electrolytes. Hafnium oxide (HfO₂) is a new and efficient blocking layer material applied over the TNPWs-ZNPs core-shell photoanode film. TiO₂ nanoparticles (TNPs) and TiO₂ nanowires (TNWs) were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). DSSCs were fabricated using the novel photoanodes with an organic sensitizer D149 dye and different types of electrolytes namely liquid electrolyte, ionic liquid electrolyte, solid-state electrolyte, and quasi-solid-state electrolyte. The DSSC-4 made through the novel core-shell photoanode using quasi-solid-state electrolyte showed better photocurrent efficiency (PCE) as compared to the other DSSCs. It has such photocurrent-voltage characteristics: short circuit photocurrent (Jsc)?=?19 mA/cm², the open circuit voltage (Voc)?=?650 mV, fill factor (FF)?=?65 %, and PCE (η)?=?8.03 %. The improved performance of DSSC-4 is ascribed to the core-shell with blocking layer photoanode could increased electron transport and suppressed recombination of charge carriers at the TNPWs-ZNPs/dye/electrolyte interface.     

Dielectric properties of BaTiO3 modified with ZrO2

The dielectric constant and loss tangent of BaTiO₈ with ZrO₂ additives have been studied. The loss tangent was less ranging between 0.16 for pure BaTiO₃ and 0.05 for samples containing 5% ZrO₂. The dielectric constant at Curie temperature decreased with increasing ZrO₂ concentration up to 0.4%. The volume resistivity measurements illustrate a peak value at a certain range of temperatures for each composition.     

Reactive plasma cladding of TiC/Fe cermet coating using asphalt as a carbonaceous precursor

A new process of preparing Ti-Fe-C composites powder for reactive plasma cladding, precursor carbonization-composition process, was developed. TiC/Fe cermet coatings were synthesized by reactive plasma cladding of the composite powder. XRD and SEM were employed to analyze the phase composition and microstructure of the composite powder and coating. The hardness and wear resistance of the coating was tested. Results show that: The compound powder prepared by precursor carbonization-composition process has very tight structure, which can avert the question of raw powder breaking-up in cladding process. The TiC/Fe cermet coating by reactive plasma cladding consists of alternate, laminated layers as following: the layers in which the round nanoscale TiC particles are dispersed within the α-Fe matrix and the layers of TiC accumulation. The TiC/Fe cermet coating by reactive plasma cladding shows superior hardness and wear resistance: The surface hardness of the TiC/Fe cermet coating is 68 ± 6 (HR30 N). In the same fretting conditions, the wear resistance of Ni60 coating is twelve times than that of the TiC/Fe cermet coating.