陶瓷微滤膜过滤超细粉体系的分析

通过计算可沉积在膜表面的临界（最大）粒径，确定了膜表面滤饼层结构与颗粒粒径的关系，并采用不同操作条件下渗透通量的数据进行验证，确定不同粒径的超细粉体系所适合的操作压力和错流速率。     

Ozone Generation from Oxygen and Air: Discharge Physics and Reaction Mechanisms

Industrial ozone generation uses a special high pressure, low temperature electrical discharge which is referred to as the dielectric barrier discharge or silent discharge. The filamentary structure of this discharge and the properties of individual microdischarges are discussed. The main reaction paths for the excited atomic and molecular species in oxygen and air are identified. Possible approaches to obtain high power densities, high ozone generating efficiencies or high ozone concentrations are discussed.     

超微粒子的合成及其应用

本文综述了超微粒子的合成方法和应用。着重叙述了超微粒子在催化、生物、医学、记录材料、传感材料等方面的应用。     

气溶胶用石墨/白碳黑超细复合粒子的制备及表征

通过对石墨/白碳黑复合粒子的制备及性能的分析测试研究,表明石墨复合粒子较纯石墨粉具有更好的分散性、更大的比表面积及孔容,更高的悬浮稳定性及红外吸收特性。     

Inertial Separation of Ultrafine Particles Using a Condensational Growth/Virtual Impaction System

ABSTRACT

A system for the separation of ultrafine particles (i.e., particles smaller than 0.1 μm) has been developed and evaluated. Ultrafine particles are first grown by means of supersaturation to a size that can be easily separated in a virtual impactor. Thus, inertial separation of ultrafine particles occurs without subjecting them to a high vacuum. The condensational growth/virtual impaction system has been evaluated using monodisperse 0.05 and 0.1 μm fluorescent PSL particles, as well as polydisperse ultrafine ammonium sulfate and potassium nitrate aerosols. The generated aerosols were first drawn over a pool of warm water (50°C) where they became saturated. Subsequently, the saturated aerosol was drawn through a cooling tube (8°C) where particles grew due to supersaturation to sizes in the range 1.0–4.0 μm. By placing a virtual impactor with a theoretical 50% cutpoint of 1.4 μm downstream of the condenser, ultrafine particles were separated from the majority (i.e., 90%) of the surrounding gas. The sampling flow rate of the virtual impactor was 8 L/min and its minor-to-total flow ratio was 0.1. For these operating conditions, the particle collection efficiency of the virtual impactor averaged to about 0.9 for particle concentrations in the range 7 × 10⁴-5 × 10⁵ particles/cm³. Particle losses through the system were found less than 5%. Increasing the particle concentration to levels in the range 106–107 particles/cm³ resulted in a decrease in the collection efficiency of the virtual impactor to about 50–70%, presumably due to the smaller final droplet size to which the ultrafine particles grew for the available supersaturation.     

超细颗粒在声场流化床中的流化特性

在内径为130mm的声场流化床中,以原生纳米级SiO2超细颗粒为物料,在声压水平为0～140dB、声波频率为0～500Hz范围内系统地考察了声波对超细颗粒流化特性的影响。结果表明：当声波频率为100～150Hz、声压大于130dB时,声波可以有效地消除节涌、抑制沟流、降低临界流化速度,显著地改善纳米SiO2颗粒的流化质量。在频率一定的情况下,声压越高,超细颗粒的临界流化速度越低,流化质量越好。当频率低于100Hz或高于150Hz时,随着频率的进一步降低或增加,超细颗粒的临界流化速度都增大,甚至又出现节涌和沟流。声波的效果减弱甚至消失。     

Soft-Sensor of Ozone Concentration in Ozone Generation System

The soft-sensor of ozone concentration is introduced. Six secondary variables are chosen in the soft-sensor model. The model is built based on the radial basis function neural network and its parameters are confirmed by the Gradient-descent algorithm. The model is implemented on the basis of the monitoring system that is necessary for ozone generation; thus, it requires no additional hardware cost. The response time of the model is less than 0.6 seconds. The experimental results indicate that the relative errors of the soft-sensor are less than 5%.     

Resuspension of Dust Particles in a Chamber and Associated Environmental Factors

Experiments investigating particle resuspension from human activities were conducted in a full-scale experimental chamber. The experiments tested three types of flooring (vinyl tiles, new and old level-loop carpets) and two ventilation configurations (ceiling and side wall supply systems). The floorings were seeded with 0.1–10 μ m test particles. The airborne particle concentration was measured by an array of optical particle counters (OPCs) in the chamber. Resuspension rates were estimated in size ranges of 0.8–1, 1.0–2.0, 2.0–5.0, and 5.0–10 μm ranging from 10^?5–10^?2 hr^?1, with higher resuspension rates associated with larger particles. Resuspension via walking activity varied from experiment to experiment. “Heavy and fast” walking was associated with higher resuspension rates than less active walking, most likely due to a combination of increased pace, increased air swirl velocity, and electrostatic field effects established by the walking. The type of floorings also influenced the particle resuspension. Given the same size and mass distribution of test particles per unit floor area, resuspension rates for the seeded new level-loop carpet were significantly higher than those for the vinyl tile flooring for larger particles (1.0–10 μ m) under the ceiling air supply system.     

Morphological and Elemental Classification of Freshly Emitted Soot Particles and Atmospheric Ultrafine Particles using the TEM/EDS

The Transmission Electron Microscopy (TEM) and Energy Dispersive Spectroscopy (EDS) were used to determine morphology and elemental composition of a variety of freshly emitted soot particles (acetylene flame, candle flame, kerosene flame, diesel exhaust, electric arc, plastic burning, styrofoam burning, wood burning [white oak and pine bark], and rice straw burning), which can be possible candidate soot in the ambient atmosphere, and ultrafine particles sampled in urban, industrial, and coastal sites during ultrafine particle formation events (combustion and photochemical events). By using mobility-classified non-refractory ((NH ₄ ) ₂ SO ₄ ) and refractory (Polystyrene latex (PSL) and salt (NaCl)) particles, limitation of the TEM was tested. Data showed that the TEM method can be used to examine shapes of both volatile particles such as (NH ₄ ) ₂ SO ₄ (100 nm) at low, but not high magnification (refer to low and high beam intensity, respectively), and non-volatile particles like NaCl (100 nm) and PSL (84 nm) at either low or high magnification. Distinct differences in morphological properties such as primary particle diameter, fractal dimension, and microstructure were observed among the different types of fresh soot particles. The atmospheric ultrafine particles were classified as agglomerates, sulfate mixtures (spherical), metallic oxides (spherical and polygonal), C-rich refractory (not agglomerated), C-rich non-refractory (not agglomerated), Si-rich (spherical), Na-rich (porous), or P-containing (non-spherical) particles. At the urban Gwangju site, a higher fraction of fresh and aged agglomerates was observed than at other sites. The C-rich non-refractory and sulfate mixtures were often observed in the photochemical event. The C-rich refractory particles were abundant at the Gwangju and Yeosu sites. The coastal Taean site had few agglomerates due to limited anthropogenic combustion source.     

Inspiratory Deposition Efficiency of Ultrafine Particles in a Human Airway Bifurcation Model

The inspiratory deposition efficiency of ultrafine particles in a physiologically realistic bronchial airway bifurcation model, approximating the airway generation 3-4 juncture, was computed for different particle sizes, ranging from 1 to 500 nm, under three different flow conditions, representing resting to heavy exercise breathing conditions. For the smallest particle sizes, say between 1 and 10 nm, molecular diffusion is the primary deposition mechanism, as indicated by the inverse relationship with flow rate, except for the highest flow rate where the additional effect of convective diffusion has to be considered as well. For the larger particle sizes, say above 20 nm, the independence from particle size and dependence on flow rate suggests that convective diffusion plays the major role for ultrafine particle deposition in bifurcations. A semiempirical equation for the inspiratory deposition efficiency, m (D, Q), as a function of diffusion coefficient D and flow rate Q, due to the combined effect of molecular and convective diffusion was derived by fitting the numerical data. The very existence of a mixed term demonstrates that molecular and convective diffusion are not statistically independent from each other.     

超微粒子的特性、制备和应用

对超微粒子的特性、制备和应用作了简明的介绍。特别对超微粒子制备工艺的选择作了比较细致的阐述。     

Generation and Long-Term Stability of Ultrafine Bubbles in Water

This study investigated submicron-sized bubbles, more precisely ultrafine bubbles (UFBs). The number concentration, size, and scattered light intensity of UFBs were measured by particle tracking analysis (PTA). The results showed that storage temperature had a significant effect, whereas the storage containers had little effect on the long-term stability of UFBs. It was found that the second-order aggregation rate equation could predict the stability of UFBs; however, there were some differences from the theory at high storage temperatures. The features of the PTA were also discussed in detail.     

纳米复合Fe-SiO2粉体的制备和结构

采用非醇盐溶胶-凝胶工艺可获得Fe与Si摩尔比达4.5/1的均匀凝胶,发现可以通过控制SiO2的含量和热处理条件来控制相结构和晶粒尺寸,热处理过程中α-Fe相是由Fe3O4相还原而来,材料中有大量氧参与反应是工艺中采用了沉淀胶溶步骤的结果,最终制备了纳米复合Fe-SiO2粉体.     

Investigation of Ozone Reaction in River Waters Causing Instantaneous Ozone Demand

Ozone consumption by water can be characterized by the instantaneous ozone demand (IOD) and a pseudo first order decay constant. Utilizing the flow injection analytical system for measuring IOD, the instantaneous ozone demand characteristics of two river waters (Korea) were investigated, utilizing a ?OH probe compound and ?OH scavenger, and were compared with those of two commercial humic acids (the Suwannee River humic acid and Aldrich humic acid). The major findings were as follows; (1) The IOD in river waters was found to be mainly due to the reaction of the ozone with natural organic matter (NOM), which constituted approximately 0.26–0.29?mg/mg DOC, and was responsible for the consumption of more than 40% of the applied ozone. Whereas, the IOD of the two commercial humic acids were three times more than those of the river waters. (2) The IOD in the river waters was mainly caused by the direct ozone reaction with dissolved organics, not from the ?OH mediated ozone reaction. However, for the two commercial humic acids, more than 40% of the IOD came from the ?OH mediated ozone reaction. (3) The hydrophobic fractions of the dissolved organics in the river waters were mainly responsible for the IOD. The IOD of the hydrophobic organics was approximately ten times larger than that of the hydrophilic organics. Although the exact magnitude of the IOD, and the relative importance of the direct/indirect ozone reaction with river water may vary greatly depending upon the source of the NOM, the characteristics of the IOD compromise a significant fraction of the ozone dose need (especially in achieving good ozone disinfection) in water treatment plants.     

选粉机分级室内的颗粒运动特性

在分析SLK5500型选粉机结构和分级机理的基础上,通过构建选粉机分级室模型,根据计算流体力学理论,运用DPM模型与非稳态算法求解颗粒运动轨迹,阐述了不同粒径的颗粒群在分级室内的运动特性. 考察了选粉机分级室内的流场速度分布,并捕捉颗粒计算了风量和转速对细粉颗粒产率和80 mm筛余的影响,模拟结果与实验结果基本相符,验证了模型的可靠性.     

Generation and Characterization of Ultrafine Chain Aggregate Aerosols

Continuously stable, well-characterized chain aggregate aerosol sources generated from a flame aerosol generator are described. To characterize the length of the chain aggregate, a new image processing software was developed to measure the length distribution of aggregates. This program measures the path length of the aggregate that has been skeletonized into one pixel in width while maintaining its length and shape. In order to generate monodisperse chain aggregate sources, a differential mobility analyzer was used to classify aggregates according to electrical mobility. A series of experiments were conducted to generate singly charged, monodisperse chain aggregate aerosol sources. The operational range of the system for generation of monodisperse chain aggregates is described. Single-mode chain aggregates with a geometric mean particle length between 1.50 and 3.20 μm and a length standard deviation around 1.3 were generated.     

超细硫酸沙丁胺醇药物颗粒的制备与表征

以沙丁胺醇和硫酸为反应物,在异丙醇溶液中采用反应结晶法制备超细硫酸沙丁胺醇颗粒。对影响产物粒度和产率的因素,如:硫酸浓度、反应温度、搅拌转速、反应时间等进行了系统研究。实验结果表明:当硫酸浓度为1.0mol.L-1、反应温度为15℃、搅拌转速为900r.min-1、反应时间为10min时,可以得到短轴为50~60nm、长径比为20~35且粒度分布较窄的针状硫酸沙丁胺醇颗粒。产品经IR、XRD等验证,符合中国、英国药典的要求,纯度大于98%。     

Ozone Generation in Air by a DC-Excited Multi-Pin-to-Plane Plasma Source

In the fields of material processing and environmental technology, atmospheric pressure non-thermal plasmas embrace a broad range of applications. Ozone generation is one of them. This paper discusses a DC-excited atmospheric pressure glow discharge in a multi-pin-to-plane electrode configuration for the production of ozone in air. The influence of discharge current, temperature, flow rate and air humidity is investigated. A simple model is proposed to predict the experimental results for the ozone production and ozone concentrations.