Aerosol Generation by a Spray-Drying Technique Under Coulomb Explosion and Rapid Evaporation for the Preparation of Aerosol Particles for Inhalation Tests

In this study, nanosized (<100 nm) aerosol particles with high mass concentrations for inhalation tests were generated by a spray-drying technique with combining Coulomb explosion and rapid evaporation of the droplets. Under typical spray-drying conditions, aerosol particles with average diameter of 50–150 nm were prepared from a suspension of NiO nanoparticles with a primary diameter of 15–30 nm. Under the Coulomb explosion method, the sprayed droplets were charged by being mixed with unipolar ions to break up the droplets, which resulted in the generation of smaller aerosol particles with diameters of 15–30 nm and high number concentrations. Under the rapid evaporation method, the droplets were heated immediately after being sprayed to avoid inertial impaction on the flow path due to shrinkage of the droplet, which increased the mass concentration of the aerosol particles. The combination of the Coulomb explosion and rapid evaporation of droplets resulted in the generation of aerosol particles with sizes less than 100 nm and mass concentrations greater than 1 mg/m³; these values are often necessary for inhalation tests. The aerosols generated under the combined method exhibited good long-term stability for inhalation tests. The techniques developed in this study were also applied to other metal oxide nanoparticle materials and to fibrous multiwalled carbon nanotubes.

Copyright 2014 American Association for Aerosol Research     

磁性Ni/NiO纳米颗粒的制备及其在蛋白分离上的应用

用1∶323的硝酸镍和尿素制备出前驱物Ni2+-oligomer,于450℃下热解2 h,得到平均粒径为2 nm的磁性Ni/NiO纳米颗粒;再利用Ni2+与组氨酸的特异性结合,将Ni/NiO纳米颗粒表面修饰上组氨酸,得到平均粒径为10 nm的磁性his-Ni/NiO纳米颗粒,在大肠杆菌体内进行蛋白吸附并在体外进行提纯。结果表明,his-Ni/NiO纳米颗粒洗脱下来的蛋白与大肠杆菌中的蛋白种类一致,该研究为蛋白分离和纯化提供了一条新思路。     

Synthesis of spherical NiO nanoparticles using a solvothermal treatment with acetone solvent

Nanometer-sized nickel oxide (NiO) particles were synthesized by thermal reactions with nickel (II) carbonate as a metal-containing precursor and four solvents: water, ethanol, butanol, and acetone. The optimal reaction conditions to obtain spherical NiO were determined to be the acetone solvent, nickel carbonate precursor, and a reaction temperature and time of 200 °C and 48 h, respectively. TEM images revealed perfectly spherical NiO nanoparticles of size ranging from 2.0 to 10.0 nm in the acetone solvent. The reaction mechanism for the formation of the NiO nanoparticles is proposed based on a pathway of chelated Ni complex during crystal growth. Although metallic Ni was also formed from reactions using the two alcoholic solvents, the Ni(OH)₂ structure remained in the water solvent after thermal treatment.     

均匀沉淀法制备纳米氧化镍及其工艺优化

为研制生物质气化用纳米N iO催化剂,文中以六水合硝酸镍为原料、尿素为沉淀剂,采用均匀沉淀法制备了纳米N iO,并利用TGA,XRD,TEM等分析手段对前驱体和产品的性能进行了表征。同时,探讨了制备条件对产品粒径和产率的影响,得出了最佳工艺条件:反应物n(六水合硝酸镍)/n(尿素)=1∶3,沉淀反应温度和时间分别为115℃和2.5 h,煅烧温度400℃,煅烧时间1 h。最佳条件下所得纳米N iO粒子呈球形,分散性好,纯度较高,属立方晶系结构,平均粒径约为7.5 nm。     

纳米氧化镍制备及表征

以六水硝酸镍和氨水为原料,采用配位均匀沉淀法制备了纳米氧化镍。探讨了制备条件对氧化镍前驱体产率和纳米氧化镍平均粒径的影响,得出最佳工艺条件：镍离子浓度为0.8 mol/L,反应物配比［n（氨水）/n（硝酸镍）］为3∶1,沉淀反应温度为80 ℃,反应时间为90 min,焙烧温度为400 ℃,焙烧时间为1 h。同时,利用X射线衍射（XRD）和透射电镜（TEM）等分析方法对产品组成和形貌进行了表征,结果显示,实验制得的氧化镍纳米晶属标准面心立方晶系结构,晶粒呈球形,平均粒径约为12 nm。     

Development of an Aerosol Focusing-Laser Induced Breakdown Spectroscopy (Aerosol Focusing-LIBS) for Determination of Fine and Ultrafine Metal Aerosols

An Aerosol Focusing-Laser Induced Breakdown Spectroscopy (Aerosol Focusing-LIBS) with a sheath air focusing and an aerodynamic lens focusing was developed to determine elemental composition of fine and ultrafine metal aerosols. Data showed that with a sheath air focusing, the LIBS qualitatively detected various metals (Al, Ca, Cd, Cr, Cu, K, Mg, Na, Ni, Zn) in submicrometer to micrometer aerosols, but that detection of ultrafine particles smaller than 100 nm was not successful due to weak intensity of emitted light. Also, the hitting rate was so low for particles at low number concentration and the single particle detection approach was only valid when aerosol loading is low. Thus, we concentrated aerosols on to a collection substrate by using the aerodynamic lens focusing system, resulting in the strong emission light from the generated plasma even for nanoparticles and the better quantification performance by the LIBS. We found the linear relationship between LIBS signal response and metal mass concentration. For example, as Cu metal concentration increased, peak area of LIBS emission line for Cu increased. The resulting correlation coefficient was 0.94 and the LOD for Cu mass concentration was found to be ～80 ng/m3, which can be further lowered by extending current collection time (～5 min). A similar linear relationship was found for Cd and Ni ultrafine metal aerosols. We also successfully detected internally mixed metal aerosols. When particles were collected on a substrate with the aerodynamic lens for 5 min prior to analysis of the deposit it was possible to analyze particles as small as 60 nm.     

Synthesis of CoO/Ni Composite Powders for Molten Carbonate Fuel Cells

CoO/Ni composite particles were prepared by the advanced mechanical-coating method called Mechanofusion™. These composite particles were composed of nickel particles uniformly covered with fine CoO particles. A new cathode structure for molten carbonate fuel cells (MCFCs), where the NiO core was coated with an outer layer of lithiated cobalt and nickel solid-solution oxide (Li(Co,Ni) oxide), was formed by oxidation and lithiation using these CoO/Ni composite particles. The solubility of nickel in this Li(Co,Ni) oxide layer into carbonate melt decreased to two-thirds of that of NiO when used as a cathode for MCFCs.     

气溶胶在毛细管扩散池组中谱带展宽的实验测定

气溶胶粒子在毛细管中的输运过程是一个谱带展宽的过程,影响谱带展宽的因素大体上可分为柱内和柱外效应两大部分.在Reynolds数0.07～0.26范围内,采用亚微米聚苯乙烯球形硬气溶胶粒子脉冲,测定了气溶胶粒子在毛细管扩散池组中的谱带展宽,由此获得了气溶胶在毛细管中的平均保留时间和穿透率.研究了平均保留时间、穿透率与流体运动速度和气溶胶粒子大小之间的关系.实验发现：气溶胶粒子在毛细管扩散池组中的平均停留时间滞后于流体平均停留时间;气溶胶粒子在毛细管扩散池组中的穿透率随流体运动速度和气溶胶粒子粒径的减小而显著减小.研究结果在气溶胶采样、监测和泄漏评估方面具有应用价值.     

Mechanical and Magnetic Properties of Novel Yttria-Stabilized Tetragonal Zirconia/Ni Nanocomposite Prepared by the Modified Internal Reduction Method

Dense ceramic/metal nanocomposite has been fabricated by internal reduction method, which includes a two-step process: sintering of ceramic–metal oxide solid solution and subsequent heat treatment in a reducing atmosphere to precipitate metal nanoparticles. This novel technique has been applied to yttria-stabilized tetragonal zirconia (Y-TZP) and nickel oxide (NiO) system to fabricate Y-TZP/Ni nanocomposite. Dense Y-TZP and 0.3 mol% NiO solid solution ceramic was successively prepared by the pressureless sintering, and Y-TZP/Ni was fabricated by the internal reduction treatment. The obtained Y-TZP/Ni nanocomposite possessed characteristic intragranular nanostructure with nano-sized metallic Ni particles of around 20 nm. Fracture toughness of both the solid solution and nanocomposite was remarkably improved because of the solid solution of NiO into Y-TZP and resultant destabilization of the tetragonal phase, and the Y-TZP/Ni nanocomposite was still destabilized by the remaining nickel solution after the reduction. The nanocomposite exhibited ferromagnetism, while the Y-TZP–NiO solid solution had diamagnetic nature. Comparison of saturation magnetization values revealed that 39.5 at.% of introduced nickel was reduced to metallic nanoparticle, proving the existence of residual NiO solute in zirconia that contributed to higher toughness value than the monolithic Y-TZP. It is concluded that the introduced internal reduction method is a suitable process to achieve multifunctional ZrO₂/Ni nanocomposite with high toughness and coexistent magnetic characteristic.     

Preparation of Matrix-Type Nickel Oxide/Samarium-Doped Ceria Composite Particles by Spray Pyrolysis

Matrix-type nickel oxide (NiO)/samarium-doped ceria (SDC) composite particles, in which NiO and SDC nano-particles were homogeneously dispersed, were synthesized by spray pyrolysis (SP) for an anode precursor of intermediate-temperature solid oxide fuel cells (IT-SOFCs). SP of an aqueous solution containing Ni, Ce, and Sm salts resulted in capsule-type composite particles that had NiO enveloped with SDC. The capsule-type composite particles actually prevent Ni aggregation between particles, but they cannot have a large contact area between nickel (Ni) and SDC. A matrix-type composite particle is expected to have a large contact area because the matrix-type composite is comprised of nanometer-sized Ni and SDC particles. An adequate addition of ethylene glycol successfully resulted in matrix-type NiO/SDC composite particles. The matrix-type composite particles also showed higher anode performance than the capsule-type composite particles in these experiments and they were effective as precursors of high-performance IT-SOFC anodes.     

Combined Optical and Ionization Measurement Techniques for Inexpensive Characterization of Micrometer and Submicrometer Aerosols

This article describes a simple combination ionization chamber and angular scattering sensor and presents the results of laboratory experiments to define its response to micrometer and submicrometer aerosols as a function of aerosol mass, surface, and diameter. The results of these experiments indicate that a simple theory is adequate to describe the operation of the sensor and presents correlations and techniques that will allow the sensor to be used for measurement and characterization of aerosols over a broad spectrum of possible applications related to adverse environmental and health consequences. For particles with volume mean diameters in the range of ~ 150–500 nm, the measured sensor responses yielded signal-to-noise ratios in the range of ~25 to > 500 for mass concentrations in the range of 0.50 to 16 mg/m³.     

Targeted Lung Delivery of Nasally Administered Aerosols

Using the nasal route to deliver pharmaceutical aerosols to the lungs has a number of advantages, including coadministration during noninvasive ventilation. The objective of this study was to evaluate the growth and deposition characteristics of nasally administered aerosol throughout the conducting airways based on delivery with streamlined interfaces implementing two forms of controlled condensational growth technology. Characteristic conducting airways were considered including a nose-mouth-throat (NMT) geometry, complete upper tracheobronchial (TB) model through the third bifurcation (B3), and stochastic individual path (SIP) model to the terminal bronchioles (B15). Previously developed streamlined nasal cannula interfaces were used for the delivery of submicrometer particles using either enhanced condensational growth (ECG) or excipient enhanced growth (EEG) techniques. Computational fluid dynamics (CFD) simulations predicted aerosol transport, growth, and deposition for a control (4.7 μm) and three submicrometer condensational aerosols with budesonide as a model insoluble drug. Depositional losses with condensational aerosols in the cannula and NMT were less than 5% of the initial dose, which represents an order-of-magnitude reduction compared to the control. The condensational growth techniques increased the TB dose by a factor of 1.1–2.6×, delivered at least 70% of the dose to the alveolar region, and produced final aerosol sizes ≥2.5 μm. Compared to multiple commercial orally inhaled products, the nose-to-lung delivery approach increased dose to the biologically important lower TB region by factors as large as 35×. In conclusion, nose-to-lung delivery with streamlined nasal cannulas and condensational aerosols was highly efficient and targeted deposition to the lower TB and alveolar regions.

Copyright 2014 American Association for Aerosol Research     

MEASUREMENT OF AEROSOL EFFECTIVE TRANSPORT COEFFICIENTS IN CYLINDRICAL TUBES

Transport of submicrometer aerosols in flows in tubes can be described by an effective one-dimensional axial convection–diffusion equation with apparent aerosol transport properties: mean aerosol velocity, mean aerosol diffusion coefficient (dispersivity) and mean aerosol deposition coefficient. These quantities are investigated experimentally by shape analyses of boluses of submicrometer Latex aerosol particles injected in the clean air flow through long tubes and a diffusion battery of capillary tubes. It is shown that the aerosol effective dispersivity and volumetric deposition coefficient significantly depend on the particle transit (residence) time within the tubes. For sufficiently long residence times these quantities are found to approach their asymptotic limiting values, predicted by the existing theories of the hydrodynamic dispersion. On the other hand, the mean aerosol velocity only weakly differs from the mean air velocity, and is almost independent of the aerosol residence time. The results obtained are important in several applications, including particle sampling using long tubes or lines.     

Reduction and Sintering of a Nickel–Dispersed-Alumina Composite and Its Properties

High-density nickel–dispersed-alumina (Al₂O₃/nickel) composites with superior mechanical properties were obtained by the hydrogen reduction and the hot pressing of alumina–nickel oxide (Al₂O₃/NiO) mixed powders. The mixtures were prepared by using NiO or nickel nitrate (Ni(NO₃)₂· n H₂O) as a dispersion source of nickel metal. Microstructural investigations of the composite fabricated using nitrate powder revealed that fine nickel particles, } 100 nm in diameter, dispersed homogeneously at the matrix grain boundaries, forming the intergranular nanocomposite. High strength (.1 GPa) and high-temperature hardness were registered for the composite that contained a small amount of nickel dispersion. The ferromagnetic properties of nickel, such as high coercive force, were observed, because of the fine magnetic dispersions, which indicates a functional value of structural composites.     

Condensational Growth May Contribute to the Enhanced Deposition of Cigarette Smoke Particles in the Upper Respiratory Tract

Previous experimental studies have shown that concentrated cigarette smoke particles (CSPs) deposit in the upper airways like much larger 6 to 7 μ m aerosols. Based on the frequent assumption that relative humidity (RH) in the lungs does not exceed approximately 99.5%, the hygroscopic growth of initially submicrometer CSPs is expected to be a relatively minor factor. However, the inhalation of mainstream smoke may result in humidity values ranging from sub-saturated through supersaturated conditions. The objective of this study is to evaluate the effect of condensation particle growth on the transport and deposition of CSPs in the upper respiratory tract under various RH and temperature conditions. To achieve this objective, a computational model of transport in the continuous phase surrounding a CSP was developed for a multicomponent aerosol consisting of water soluble and insoluble species. To evaluate the transport and deposition of dilute hygroscopic CSPs in the upper airways, a model of the human mouth-throat (MT) through approximately respiratory generation G6 was considered with four steady inhalation conditions. These inhalation conditions were representative of inhaled ambient cigarette smoke as well as warm and hot saturated smoke. Results indicate that RH conditions above 100% are possible in the upper respiratory tract during the inhalation of a warm or hot saturated airstream. For sub-saturated inhalation conditions, initial evaporation of the CSPs was observed followed by hygroscopic growth and diameter increases less than approximately 50%. In contrast, the inhalation of warm or hot saturated air resulted in significant particle growth in the MT and tracheobronchial regions. For the inhalation of warm saturated air 3°C above body temperature, initially 200 and 400 nm particles were observed to increase in size to above 3 μ m near the trachea inlet. The upper boundary inhalation condition of saturated 47°C air resulted in 7 to 8 μ m droplets entering the trachea. These results do not prove that the enhanced deposition of CSPs in the upper airways is only a result of condensational growth. However, this study does highlight condensational growth as a potentially significant mechanism in the deposition of smoke particles under saturated inhalation conditions.     

Preparation of SOFC anode composites by spray pyrolysis

Lowering the SOFC working temperature would also be greatly attractive, but low temperature working SOFCs require high-performance anodes. The cermet SOFC anodes, which are composed of nickel and samarium doped ceria, were prepared by spray pyrolysis (SP), because SP produces spherical particles with small size distributions. SP-derived particles of NiO, SDC, and NiO/SDC composite had a round shape and comprised nanometer-sized primary grains. The cermet anodes were prepared by using SP-derived NiO/SDC composite particles or mixing SP-derived NiO and SDC particles. The anode prepared with the composite particles showed higher SOFC cell performance than that with the mixed ones. The composite particles had high surface areas and a capsule-type form. The outer shell would be composed of SDC and the inner core was NiO. The capsule-type composite particles would depress aggregation of Ni or NiO during reduction from NiO to Ni metals, and this depression would enhance SOFC anode performance.     

Processing and characterisation of a fine nickel oxide/zirconia/composite prepared by polymeric complex solution synthesis

A homogeneous dispersion of nickel in a YSZ ceramic matrix by the polymeric organic complex solution method was achieved. A YSZ powder was added to the polymeric gel containing Ni²⁺ cations leading to an organic resin in which the YSZ particles were embedded. By further heat treatment a composite of ultrafine nickel oxide dispersed in the YSZ matrix was attained. After sintering and reducing treatment of nanocrystalline NiO/YSZ composite, the microstructure of the Ni/YSZ cermet showed a uniform distribution of the porous metallic Ni particles of about 1–2 μm surrounded by a microporous space. The electrical properties of NiO/YSZ (55/45 wt.%) composites were studied using impedance spectroscopy in the temperature range from 100 to about 700 °C. Variations in activation energy were in agreement to the NiO electrical behaviour with increasing temperatures for polymer complex solution NiO/YSZ prepared composite, which indicates a uniform and fine-grained microstructure, in which the YSZ–YSZ and/or the NiO–NiO particle contacts were predominant.     

Preparation of Nickel Powders by Spray Pyrolysis of Nickel Formate

The preparation of nickel powders by the ultrasonic spray pyrolysis of Ni(HCOO)₂ was studied. Phase-pure nickel powder was obtained at as low as 350°C. HCOOH was a reducing source for nickel formation. Moreover, metallic nickel was obtained at a residence time as short as 0.1 s at 600°C. A broad range of particle morphologies, which included agglomerated nanoparticles, nonagglomerated submicrometer particles, hollow particles, and spherical dense particles, were obtained from Ni(HCOO)₂ pyrolysis and were shown to depend on the precursor solution and the operating condition.     

Filtration of Multi-Walled Carbon Nanotube Aerosol by Fibrous Filters

Filtration efficiency of multi-walled carbon nanotube (MWCNT) aerosol by fibrous filter was evaluated experimentally. Mono-mobility test aerosols with electrical mobility diameter of 100, 200, and 300 nm were generated by the atomization of MWCNT aqueous suspension followed by mobility classification with a differential mobility analyzer (DMA). By analyzing the shape of classified aerosol particles under a scanning electron microscope, it was found that the DMA-classified 300 nm particles were fibrous in shape and had uniform diameter of about 60 nm and length of 2.1 micrometer. On the other hand, 100 nm and 200 nm particles contained a fairly large amount of multiply charged fibrous particles with a larger diameter. These test aerosols were challenged to a medium performance fibrous filter at various filtration velocities. As a result, fibrous particles were captured by fibrous filter at a higher collection efficiency than the spherical particles with the same mobility. By analyzing the single fiber capturing efficiency, interception incorporating the rotation of fibrous particles is found to be the dominant capturing mechanism for the fibrous particles in the studied size range.