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1.
A new reactor and a novel in-situ sampling technique were developed for the study of the synthesis of CeO2 powders produced from dissolved cerium nitrate salts. The conical reactor minimized particle recirculation and provided a
highly symmetrical and undisturbed plasma flow suitable for the analysis of the phenomena affecting the formation of CeO2 powders. Both a calorimetric study of the reactor and a thermodynamic analysis of CeO2 formation were conducted. The sampling probe is described and near-isokinetic sampling was achieved. The sampled particles
were collected using a miniature wet collection system, i.e. a mist atomizer and a custom-made spray chamber. A numerical
simulation of the velocity and temperature fields of the plasma gas in the reactor was done using Fluent. A comprehensive
droplet-to-particle formation mechanism presented elsewhere is revisited and expanded based on calorimetry, thermodynamics
of CeO2 formation, numerical simulations and collected particles. No traces of other oxidation states other than CeO2 were found. 相似文献
2.
The decomposition of N2O in a 13.56-MHz parallel-plate system was studied usingin situ Fourier transform infrared (FTIR) spectroscopy. Areas of two infrared absorption bands of N2O recorded at 8 cm–1 resolution were used to estimate relative gas-phase dissociation as a function of rf power and flow rate at 500 mT. Flow rate was found to strongly affect band areas over the range of powers investigated (10–90 W). The effect of rf power on band areas diminished above 40 W, probably due to poor plasma confinement. Distortion of the band shapes by the plasma permitted rotational temperatures to be estimated. Rotational temperature increased essentially linearly with power at constant flow rate, reaching 450 K at 80 W, but was independent of flow rate at constant power. Rotational temperatures were also found to depend on the temperature of the electrodes, which were heated by plasma exposure. No infrared-active product species were observed even under batch conditions where all N2O was irreversibly dissociated. This lack of detectable products and a 50% pressure rise observed in a batch study suggest that N2 and O2 are the primary stable discharge products. 相似文献
3.
Savukov IM Seltzer SJ Romalis MV 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,185(2):214-220
We demonstrate detection of proton NMR signals with a radio-frequency (rf) atomic magnetometer tuned to the NMR frequency of 62 kHz. High-frequency operation of the atomic magnetometer makes it relatively insensitive to ambient magnetic field noise. We obtain magnetic field sensitivity of 7 fT/Hz1/2 using only a thin aluminum shield. We also derive an expression for the fundamental sensitivity limit of a surface inductive pick-up coil as a function of frequency and find that an atomic rf magnetometer is intrinsically more sensitive than a coil of comparable size for frequencies below about 50 MHz. 相似文献
4.
高频热等离子体发生器数值模拟最近进展 总被引:4,自引:0,他引:4
高频感应耦合热等离子体发生器中的流动与传热和电磁场强烈耦合,它的数值模拟经历了从最简单的一维模型到比较完善的二维数值模拟的几个发展阶段.以前的基于一维非自洽电磁场解的模拟方法,最近已为包括自洽电磁场解的新方法所取代.新方法还能容易地推广到三维情形,从而为发生器的性能预估及参数优化提供有力的工具.本文概述了最近这一进展的产生背景及研究情况. 相似文献
5.
Tatiana A. Vovk Semyon S. Rudyi Andrei V. Ivanov Evgeniy Y. Perlin Yuri V. Rozhdestvensky 《Physics letters. A》2019,383(9):923-928
One of the most interesting problems of modern physics is the realization of nanoparticles in macroscopic quantum states, in which they behave as a quantum objects. These states can only be implemented at ultra-low translational temperatures that have not been achieved so far. Here we develop a novel method for optical cooling of CaF2:Yb3+ nanocrystals, which is based on the coherent population transfer induced in the impurity ions by ultraviolet Raman pulses. A doped nanocrystal localized in a radio-frequency trap is cooled due to the photon recoil from the pulses of varied intensity. The proposed method allows to obtain nanocrystals with translational temperatures of the order of 10?9 K, which indicates that the nanocrystal approaches a macroscopic quantum state. 相似文献
6.
A.I. Figueroa J. Bartolomé J.M. García del Pozo A. Arauzo E. Guerrero P. Téllez F. Bartolomé L.M. García 《Journal of magnetism and magnetic materials》2012
A transverse susceptibility (TS) measurement system based on a simple inverter CMOS cell oscillator cross-coupled to a LC tank is presented. The system has been implemented to operate at a Quantum Design Physical Properties Measurement System (PPMS). We introduce several improvements with respect to similar currently operating TS measurement equipments. The electronics have been redesigned to use CMOS transistors as active devices, which simplifies the circuit design and enlarge the tuning range, thus making the proposed electronic block more feasible, predictable, and precise. Additionally, we propose a newly designed sample holder, which facilitates the procedure to change a sample and improves reproducibility of the circuit. Our design minimizes the thermal leak of the measuring probe by one order of magnitude, allowing to measure from 1.8 K in standard PPMS systems, thanks to the use of a low temperature beryllium–copper coaxial cable instead of the conventional RG402 Cu coaxial cable employed in the insert for the PPMS in similar systems. The data acquisition method is also simplified, so that the measuring sequences are implemented directly in the PPMS controller computer by programming them in the Quantum Design MultiVu software that controls the PPMS. We present the test measurements performed on the system without sample to study the background signal and stability of the circuit. Measurements on a Gd2O3 calibrating sample yield to the estimation of the system sensitivity, which is found to be on the order of 10−6 emu. Finally, measurements on a TmCo2 Laves phase sample with a ferrimagnetic transition temperature around 4 K are described, demonstrating that the developed system is well suited to explore interesting magnetic phenomena at this temperature scale. 相似文献
7.
Toyonobu Yoshida Kunihiko Nakagawa Toshiya Harada Kazuo Akashi 《Plasma Chemistry and Plasma Processing》1981,1(1):113-129
A numerical model has been developed for predicting the two-dimensional flow and temperature fields in a radio-frequency (rf) plasma torch. The method employed here is based on Boulos' model with the exception of the boundary conditions for the electric and magnetic field equations. Calculations have been made for the confirmation of a new sample injection method, which is capable of completely evaporating refractory materials at high feeding rates without interfering with the stability of the plasma. In the newly designed torch, the reagent is radially injected into the hottest part of the plasma through quartz capillary tubes set symmetrically between an inductor coil. Experimental investigations have also been performed for verifying the proper function of the design. These results provide evidence that our radial injection method developed here is more effective in practical processing than the conventional axial injection methods. 相似文献
8.
Iwao Sugimoto Masumi Okamoto Kazuhiko Takahashi 《Polymer Degradation and Stability》2010,95(6):929-934
Carbonaceous films with microcolumnar layer have been prepared by radio-frequency sputtering of polysaccharides pectin. The repeated sputtering has developed the densely packed seamless microcolumns, which are separated by the narrow grooves. The residual film stress has formed the honeycomb-patterned ridges. X-ray photoelectron spectroscopy and energy dispersion spectroscopy revealed the inclusion of nitrogen in the film constituents. The film surface is hydrophilic mainly due to the polar functional groups, such as the carboxyl and amino groups. Nitrogen adsorption measurement revealed that the specific surface area of the film was no less than 109 m2/g. Impedance analysis of the film-coated quartz crystal resonator clarified that the film had the higher adsorption capacities to the polar and cohesive vapors, such as ethyl alcohol. The adsorption of organic vapors has not induced the viscoelastic changes in the film. 相似文献
9.
对磁共振成像(MRI)的安全性进行了综述,主要涉及五个方面:静磁场、梯度场、射频场、噪声和造影剂.在没有铁磁性外源性物质的条件下,静磁场对人体没有明显的损害,有较高的安全系数.随时间变化的梯度场(dB/dt)可在受试者体内诱导出电场而兴奋神经或肌肉.当梯度上升时间只有数毫秒时,外周神经兴奋是梯度场安全的上限指标.在MRI测定过程中,射频场发射的功率在患者组织内转化成热能,使组织温度升高.MRI运行过程中可产生各种噪声,可能使某些患者的听力受到损伤,使用耳塞仍是削弱噪声最简单和最经济的方法.目前使用的造影剂主要为含钆的化合物,副作用发生率在2%~4%. 相似文献
10.
用射频等离子体增强非平衡磁控溅射在Si100基底上沉积了金属Cu膜。研究了偏压,射频功率和磁场等沉积参数对膜性能的影响。用扫描电子显微镜(SEM)、原子力显微镜(AFM)、X射线衍射(XRD)和电子能谱(EM)检测了膜的表面形貌,结构和成分。结果表明,射频放电有利于表面均匀光滑、电导率高的Cu沉积膜的形成;沉积参数对沉积膜的性能有重要的影响。 相似文献