Characteristics of Yttrium Iron Garnet Ultrafine Particles Prepared by the Alkoxide Method

Hydrolysis of a mixture of iron ethoxide and yttrium butoxide produced amorphous yttrium iron garnet (YIG) ultrafine particles with a mean diameter of 9 nm. The particles prepared by hot water vapor hydrolysis were less agglomerated than those prepared by plain hot water. DTA revealed that a broad phase transition temperature T _o from amorphous YIG to crystalline YIG ultrafine particles is 691°C with heat discharge of 118 kJ/mol which is attributed to the entropy decrease accompanying the crystallization, whereas magnetic experiments gave a value of T _o= 650°C. The particles calcined at 700°C were single-crystalline ones while those calcined at higher temperatures (at least higher than 800°C) were multicrystalline ones.     

Development and Evaluation of a Compact Facility for Exposing Humans to Concentrated Ambient Ultrafine Particles

This article presents the development and evaluation of a very compact facility for exposing humans to concentrated ambient ultrafine particles (d_a < 0.15 μm). The human ultrafine particle concentrator (UFPC) operates at an intake flow rate of 1200 liters per minute (LPM). The concentrator is preceded by an ultrafine impactor which separates the accumulation mode from ultrafine mode particles under a very low pressure drop (1.5 kPa), a feature that is essential in enabling human inhalation studies of ultrafine concentrated ambient particulates (CAP). A key feature of the UFPC is a new cooling system, consisting of a programmable refrigerated circulator, which produces the supersaturation that is necessary to grow ultrafine PM to supermicrometer sizes so that they can be concentrated by means of conventional virtual impaction. The new cooling system allows for entirely automated operation of the UFPC. The UFPC was characterized in field experiments, in which the concentration enrichment of ultrafine particles was determined based on their number and mass concentration as well as on chemical composition including elemental carbon (EC), inorganic ions (sulfate and nitrate), and polycyclic aromatic hydrocarbons (PAH). Tests were conducted at minor-to-total flow ratios varying from 2.5–5% (hence at minor flow rates between 30–60 LPM). Measurements with the scanning mobility particle sizer (SMPS) showed a near-ideal increase in number concentrations (corresponding to the ratio of total-to-minor flow rate) of ultrafine particles after enrichment. The concentration enrichment was uniform across the entire particle diameter range of 15–660 nm. Similar results were obtained for EC and PAH concentrations (measured by an Aethalometer). Time-integrated filter-based tests, conducted to characterize the system for ultrafine PM mass and inorganic ion concentrations showed that the average enrichment factor was very close to the ideal values, indicating near-perfect collection efficiency with minimal particle losses.     

Diffusion Sampler for Measurement of Acidic Ultrafine Particles in the Atmosphere

The adverse health effect of acidic ultrafine particles (AUFPs) has been widely recognized in scientific societies. These particles mainly deposit on the surface by diffusion and so far there is no mature method for the measurement of airborne AUFPs. The purpose of this study was to develop a diffusion sampler (DS) with iron nanofilm detectors to effectively measure the number concentration and size distribution of airborne AUFPs in indoor and outdoor environments. The developed DS was made of stainless steel with a flat and rectangular channel with 1.0 mm height, 50 mm width, and 500 mm length. The iron nanofilm detectors were deployed on rectangular recesses inside the sampler at three different locations along the length of the channel to collect the ultrafine particles. The exposed detectors were then scanned using an atomic force microscope (AFM) to numerate and distinguish the AUFPs from the nonacidic UFPs. Prior to sampling, the semi-empirical equations for the diffusive deposition efficiency of particles at the different detector locations in the sampler were obtained on the basis of theoretical diffusive mechanism and modified by the experimental data using polystyrene latex (PSL) standard particles. After calibration, the DS + AFM method and a commercially available online measurement system, i.e., scanning mobility particle sizer (SMPS) incorporated with a condensation particle counter (CPC), were simultaneously used in a 4-week field measurement. Both methods showed very good agreement in terms of total particle number concentration and size distribution. The results indicate that the diffusion sampler is effective for the quantification of ambient acidic ultrafine particles.

Copyright 2014 American Association for Aerosol Research     

A Methodology for Measuring Size-Dependent Chemical Composition of Ultrafine Particles

Ultrafine particulate matter (PM) consists of particles mostly emitted by combustion sources but also formed during gas-to-particle formation processes in the atmosphere. Various studies have shown these particles to be toxic. The very small mass of these particles has posed a great challenge in determining their size-dependent chemical composition using conventional aerosol sampling technologies. Implementing 2 technologies in series has made it possible to overcome these 2 problems. The first technology is the USC Ultrafine Concentrator, which concentrates ultrafine particles (i.e., 10-180 nm) by a factor of 20-22. Ultrafine particles are subsequently size fractionated and collected on suitable substrates using the NanoMOUDI, a recently developed cascade impactor that classifies particles in 5 size ranges from 10 to 180 nm. The entire system (concentrator + NanoMOUDI) was employed in the field at 2 different locations in the Los Angeles Basin in order to collect ultrafine particles in 3 consecutive 3 h time intervals (i.e., morning, midday, and afternoon). The results indicate a distinct mode in the 32-56 nm size range that is most pronounced in the morning and decreases throughout the day at Downey, CA (a "source" site), affected primarily by vehicular PM emissions. While the mass concentrations at the source site decrease with time, the levels measured at Riverside, CA (a "receptor" site), are highest in the afternoon with a minimum at midday. In Riverside, ultrafine EC (elemental carbon) and OC (organic carbon) concentrations were highly correlated only during the morning period, whereas these correlations collapsed later in the day. These results indicate that in this area, ultrafine PM is generated by primary emissions during the morning hours, whereas secondary aerosol formation processes become more important as the day progresses.     

Chemical Mass Closure and Chemical Characteristics of Ambient Ultrafine Particles and other PM Fractions

Ambient ultrafine particles (UPs or PM _0.1 ), PM _2.5 and PM ₁₀ were investigated at the roadside of Syuefu road in Hsinchu city and in the Syueshan highway tunnel in Taipei, Taiwan. A SMPS (TSI Model 3936), three Dichotomous samplers (Andersen Model SA-241), and three MOUDIs (MSP Model 110) were collocated to determine the PM number and mass concentrations simultaneously. The filter samples were further analyzed for organic carbon (OC), element carbon (EC), water-soluble ions, and trace elements. The OC artifact was studied and quantified using the quartz behind quartz (QBQ) method for all PM fractions. Taking into account the OC artifact, chemical mass closure (ratio of the reconstructed chemical mass to the gravimetrical mass) of PM _0.1 , PM _2.5 , and PM ₁₀ was then calculated and found to be good. The chemical analysis results of UPs at both sites showed that UPs in the present tunnel was mostly contributed from the vehicle emissions while UPs at the roadside was mainly influenced by urban sources.     

超声化学法制备阿奇霉素超细粉体的研究

采用超声化学法制备了阿奇霉素超细粉体.具体研究了超声模式、阿奇霉素酸溶液滴加速度、反应温度及稳定剂浓度对结果的影响,并通过红外光谱对样品结构和成分进行鉴定,用扫描电镜和Zeta电位粒度仪表征样品形貌及粒度分布.结果表明,本方法制备的阿奇霉素微粉,未改变阿奇霉素的结构,最佳条件下制备的颗粒粒径为260nm左右,颗粒均匀,粒度分布窄.     

超临界CO2法制备超细HMX颗粒

考察了预膨胀压力、HMX丙酮溶液初始浓度、取样停留时间及其他因素对制备HMX超细微粒粒度和晶体性质的影响.制备的超细HMX微粒平均粒径在350 nm以下,一部分微粒粒度小于100 nm.结果表明,预膨胀压力对HMX颗粒尺寸的影响较大,压力增加,HMX平均粒度变小,粒度分布变窄;HMX丙酮溶液初始浓度对HMX的粒度和粒度分布有很大影响,初始浓度越小平均粒径就变小,粒度分布变窄.停留时间及喷嘴尺寸对颗粒粒度、粒度分布及其形貌都有不同程度的影响.     

酸性气体组分含量测定方法的改进

介绍了ＡＳ循环洗涤工艺中酸性气体组分含量的新分析方法,新方法具有结果稳定,数据可靠,完全可作为生产调整的依据。     

Development of a Pulsed-Field Differential Mobility Analyzer: A Method for Measuring Shape Parameters for Nonspherical Particles

For a nonspherical particle, a standard differential mobility analyzer (DMA) measurement yields a mobility-equivalent spherical diameter, but provides no information about the degree of sphericity. However, given that the electrical mobility for nonspheres is orientation-dependent, and that orientation can be manipulated using electric fields of varying strength, one can, in principle, extract some type of shape information through a systematic measurement of mobility as a function of particle orientation. Here, we describe the development of a pulsed-field differential mobility analyzer (PFDMA) which enables one to change the peak E-field experienced by the particle to induce orientation, while still maintaining the same time-averaged field strength as a standard DMA experiment. The instrument is validated with polystyrene latex (PSL) spheres with accurately known size, and gold rods with dimensions accurately determined by transmission electron microscopy (TEM). We demonstrate how the instrument can be used for particle separation and extraction of shape information. In particular, we show how one can extract both length and diameter information for rod-like particles. This generic approach can be used to obtain dynamic shape factors or other multivariate dimensional information (e.g., length and diameter).

Copyright 2014 American Association for Aerosol Research     

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.     

TG氧化铁常(低)温精脱硫技术的发展及应用

回顾了氧化铁脱硫技术的发展历程。指出活性氧化铁在常低温下能将H₂S精脱除至0.1～1 ppm以下,可同(200~350) ℃下中温氧化铁脱硫相媲美。讨论了氧化铁常低温精脱硫的理论依据。介绍了太原工业大学近年开发的TG型氧化铁系列脱硫剂的性能及应用。     

Synthesis of sub-micrometer lithium iron phosphate particles for lithium ion battery by using supercritical hydrothermal method简

A supercritical hydrothermal method was employed to prepare sub-micrometer LiFePO4 particles with high purity and crystallinity. The structure and morphology of LiFePO4 particles were characterized by X-ray diffraction and scanning electron microscope. The electrochemical tests were carried out to determine the reversible capacity, rate and cycling performance of the LiFePO4 particles as cathode material for lithium ion battery. Experimental results show that solvent and calcining time have significant effects on purity, size and morphology of LiFePO4 particles. Mixed solvent contained deionized water and ethanol is conducive to synthesize smaller and more uniform particles. The size of LiFePO4 particles as-prepared is about 100-300 nm. The specific discharge capacities of the LiFePO4 particles are 151.3 and 128.0 mA. h. g-1 after first cycle at the rates of 0.1 and 1.0 C, respectively. It retains 95.0% of the initial capacity after 100 cycles at 1.0 C.     

TiO2超细粒子的微乳法制备、表征及性能研究

采用表面活性剂OP-7、正庚烷、水和异戊醇形成的微乳体系制备TiO2超细粒子,并考察水和异戊醇含量对TiO2超细粒子平均粒径的影响。所得产物易于分离,溶剂可回收,产率达80%。结果表明,500℃灼烧2h所制备的TiO2超细粒子为锐钛型。采用FTIR、XRD、BET、DSC、TEM对TiO2超细粒子进行表征,由FTIR分析可知,表面无残留有机物;由DSC分析可得晶型转变温度为437 3℃;根据XRD分析计算的平均粒径为9 7nm,颗粒分散度较高;采用BET法测定比表面积为85 8m2/g。以苯酚的光催化氧化作为目标反应来评价TiO2超细粒子的光催化活性。苯酚光催化降解反应2 5h,降解率可达85%。     

酸性镀锌溶液中铁杂质的处理方法

试验了用双氧水处理酸性镀锌溶液中铁杂质的方法,实验表明:在pH = 4.5 ～ 5.0时,向镀液中加入30%的双氧水0.1 mL/L, 只有23.2% ～33.9%的双氧水能与Fe2+离子反应生成氢氧化铁沉淀,其余的双氧水则破坏光亮剂.在较低的pH下处理铁杂质,双氧水的有效利用率较高.应当选择抗氧化性强的中间体配制酸性镀锌光亮剂或者研究其它方法来处理镀锌液中的铁杂质.     

采用铁氰化钾去除酸性镀锌液中的铁杂质

采用铁氰化钾处理酸性镀锌溶液中二价铁杂质的方法为:向镀液中加铁氰化钾,Fe2+离子与铁氰化钾反应生成亚铁氰化钾和三价铁,亚铁氰化钾与锌离子反应生成亚铁氰化锌沉淀,三价铁水解生成氢氧化铁,过量的铁氰化钾与锌离子生成铁氰化锌.实验表明,用这种方法处理酸性镀锌液中的铁杂质,铁氰化钾的利用率为65.9%～87.6%.     

Examining Elemental Surface Enrichment in Ultrafine Aerosol Particles Using Analytical Scanning Transmission Electron Microscopy

The surface structure and chemistry of ultrafine aerosol particles (typically particles smaller than 100 nm in diameter) play key roles in determining physical and chemical behavior, and is relevant to fields as diverse as nanotechnology and aerosol toxicity. Analytical scanning transmission electron microscopy (STEM) is one of the few analytical methods available that is potentially capable of characterizing ultrafine particles at subnanometer resolution. We propose a method that enables STEM to characterize and quantify elemental surface enrichment within radially symmetrical particles at a spatial resolution of less than 1 nm when used in conjunction with electron energy loss spectroscopy (EELS) and X-ray energy dispersive spectroscopy (EDS). Although the method relies on a number of assumptions for complete particle characterization, estimation of the depth of an outer layer of elemental enrichment should be possible with relatively few assumptions. A preliminary investigation of the method has been carried out using particles from gas metal arc welding on mild steel. Using the analysis method, we were able to characterize Si and O enrichment in a number of particles. Two particles were investigated extensively using EELS and EDS analysis. Both techniques allowed surface enrichment of Si to be identified and quantified in the particles, although the relatively poor sensitivity of EDS was a limiting factor in the analysis. EELS allowed rapid data collection and enabled surface enrichment of Si and O to be characterized. Using a simple model to describe elemental composition with radial position, it was estimated that Si and O were enriched in an outer layer around the particle approximately 1 nm deep.     

石墨超细片状磨碎的机理及方法

为了保持较完整的片状结构以适应工业应用的需求,提供了一种新的搅拌磨技术能将天然鳞片状石墨磨细到１ｎｍ以下,并筛选了一种新的分散剂,探讨了研磨设备的选型方法和最佳工艺条件的选择,同时研究了影响研磨结果的因素。     

超细YMnO_3的硬脂酸溶胶-凝胶法合成及充放电性能

以硬脂酸、Y2O3及Mn（NO3）2为原料,采用硬脂酸溶胶-凝胶法,在700℃保温8h制备钙钛矿型复合氧化物YMnO3纳米颗粒;并以YMnO3作为超级电容器电极材料,采用恒电流充放电测试方法研究YMnO3的性能。结果表明：YMnO3表现出优良的电化学性能,在6mol/L的KOH电解液中,单电极比电容可达164.19F/...     

Synthesis of Silicon Carbide–Silicon Nitride Composite Ultrafine Particles Using a Carbon Dioxide Laser

The synthesis and the structure of silicon carbide-silicon nitride (SiC─Si₃N₄) composite ultrafine particles have been studied. SiC─Si₃N₄ composite ultrafine particles were prepared by irradiating a SiH₄, C₂H₄, and NH₃ gas mixture with a CO₂ laser at atmospheric pressure. The composition of composite powders changed with the reactant gas flow rate. The carbon and nitrogen content of the powder could be controlled in a wide range from 0 to 30 wt%. The composite powder, which contained 25.3 wt%. carbon and 5.8 wt% nitrogen, had a (β-SiC structure. As the nitrogen con- tent increased, SiC decreased and amorphous phase, Si₃N₄, Si appeared. The results of XPS and lattice constant measurements suggested that Si, C, and N atoms were intimately mixed in the composite particles.     

Novel Method for Coating Magnetic Iron Oxide Particles with Carbon Black

Magnetic particles with finer size, higher coercive force, higher blackness, and lower electrical resistance are required to produce better magnetic tape materials. A new method to coat iron oxide particles with carbon black using an adhesive agent is reported in this paper. Magnetic tapes prepared using the coated particles in the recording layer exhibit improvements in both light transparency and electrical resistance. A decrease in transparency of ∼20% and a reduction in electrical resistance of ∼1 order of magnitude relative to conventionally prepared tapes are achieved when ∼5% of the particle weight is carbon black. Surface smoothness and the orientation ratio are also improved because the dispersibility of these particles in magnetic lacquer is better than that of uncoated magnetic iron oxide particles. Higher electromagnetic performance relative to the conventionally prepared layers is also obtained. TEM photographs indicate that all the carbon black is firmly bound to the surface of the magnetic iron oxide particles in a distinct layer.