Elucidating the effects of particle sizes on the fire extinguishing performance of core-shell dry water

Based on the percolation threshold theory of conductive-dielectric composites, the dielectric constant can be improved more by adding a certain mass fraction of conductive particle into polymer matrix. However, the dielectric loss increases with the increasing mass fraction of conductive particle. In this paper, conductive Polyaniline (PANI) with different particle sizes is utilized to illustrate that reducing particle size can improve the dielectric properties. The dielectric constant is increased from 319 to 540, and dielectric loss is decreased from 2.34 to 0.85 when PANI with smaller particle size is used. Moreover, PANI coated with an insulating surfactant layer can further improve the dielectric properties, the experimental results show that the dielectric constant of the composite could be more than 1000, while the dielectric loss is 0.35 at 1[Formula: see text]KHz.

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Application of a novel a core-shell microstructured nanocomposites as a fire extinguishant using seawater

E3S Web of Conferences ◽

10.1051/e3sconf/202123701009 ◽

2021 ◽

Vol 237 ◽

pp. 01009

Author(s):

Hao Liu ◽

Tianwei Zhang ◽

Cunwei Zhang ◽

Lei Xiao ◽

Qiang Liang

Keyword(s):

High Speed ◽

High Efficiency ◽

Water Shortage ◽

Core Shell ◽

Dry Powders ◽

The Core ◽

Fire Extinguishing ◽

External Shell ◽

Treatment Technologies ◽

In Fire

Water has unsurpassed capabilities in fire extinguishing. However, water scarcity is rapidly increasing in many regions and water shortage problems have led to find either new water resources or improve seawater treatment technologies. In this study, a new environment-friendly and high-efficiency powdered fire extinguishing agent with a core-shell structure is designed. The designed extinguishing agent is a colloidal powder with a 92% liquid content and is prepared through physical modification and high-speed shearing. Fumed silica is used for the external shell due to its chemical inertness, whereas seawater is used as the core due to its high extinguishing efficiency. Results show that the size of the prepared agent ranged between 100–200μm. The two fire extinguishing experiments of different scales demonstrate that the employing inorganic salts with seawater as the core can significantly increase the efficiency of the new powder in extinguishing gasoline and diesel fire compared with ultrafine and common ABC dry powders. The suppression mechanism of action is caused by the combined flame chemical and pyrolysis theories of the potassium compounds. This study would be of great theoretical significance and application value for improving the application scope of the seawater.

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Influence of Mie scattering on nanoparticles with different particle sizes and shapes: Photometry and analytical ultracentrifugation with absorption optics

Journal of the Serbian Chemical Society ◽

10.2298/jsc0503361l ◽

2005 ◽

Vol 70 (3) ◽

pp. 361-369 ◽

Cited By ~ 53

Author(s):

M.D. Lechner

Keyword(s):

Analytical Ultracentrifugation ◽

Mie Scattering ◽

Precise Determination ◽

Core Shell ◽

Particle Sizes ◽

Wide Range ◽

Photometric Measurements ◽

Shell Particles ◽

Reliable Methods

Nanoparticles are used in large quantities for very different applications. A precise determination of the diameter and the particle size distribution which is responsible for the application properties is therefore essential. Reliable methods for measuring the above mentioned quantities are photometric measurements and analytical ultracentrifugation with an UV optics detector. Both methods are ruled by the Mie effect, that is scattering and absorption of the particles as function of the diameter, the wavelength, and the shape of the particles. The extinction coefficients ?=?/c for spheres, rods, and core shell particles have been calculated and plotted over a wide range of the size parameter ?d/?. Two examples for multimodal latex particles and core shell particles have been given and demonstrate the applicability of the method.

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Synthesis and Characterization of Silver/Titanium dioxide Core-Shell Nanoparticles

Borneo Journal of Resource Science and Technology ◽

10.33736/bjrst.252.2013 ◽

1970 ◽

Vol 3 (1) ◽

pp. 21-24

Author(s):

Suk Fun Chin ◽

Suh Cem Pang ◽

Freda Emmanuel Idely Dom

Keyword(s):

Photocatalytic Activity ◽

Ag Nanoparticles ◽

Sol Gel ◽

Model Reaction ◽

Synthesis And Characterization ◽

Core Shell ◽

Particle Sizes ◽

Shell Nanoparticles ◽

Core Shell Nanoparticles

Silver nanoparticles (AgNPs) with mean diameter of 150 nm were synthesized by using an aqueous-basedreduction method. Ascorbic acid and sodium hydroxide (NaOH) were used as a reducing agent and as acatalyst, respectively. These AgNPs were subsequently coated with a layer of TiO2 to form Ag/TiO2 core-shellnanoparticles by using a sol-gel method. The particle sizes and morphology of Ag/TiO2 core-shellnanoparticles were characterized using scanning electron microscopy (SEM) and transition electronmicroscopy (TEM). The photocatalytic activity of the Ag/TiO2 core-shell nanoparticles were evaluated basedon the degradation of methylene blue (MB) as the model reaction. The TiO2 coating has resulted in theenhanced photocatalytic activity of Ag nanoparticles as compared to bare Ag nanoparticles.

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Ceria/silicon carbide core–shell materials prepared by miniemulsion technique

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.2.67 ◽

2011 ◽

Vol 2 ◽

pp. 638-644 ◽

Cited By ~ 6

Author(s):

Lars Borchardt ◽

Martin Oschatz ◽

Robert Frind ◽

Emanuel Kockrick ◽

Martin R Lohe ◽

...

Keyword(s):

Cross Correlation ◽

Methane Combustion ◽

Correlation Spectroscopy ◽

Core Shell ◽

Particle Sizes ◽

Temperature Programmed Oxidation ◽

Preparation Conditions ◽

Temperature Programmed ◽

Shell Particles ◽

First Time

For the first time we present the synthesis of CeO2/Si(O)C core–shell particles prepared by the miniemulsion technique. The Si(O)C core was obtained by means of a polycarbosilane precursor (SMP10), which was subsequently functionalized with ceria and pyrolyzed to the ceramic. The size of these particles could easily be adjusted by varying the surfactants and the surfactant concentration, or by the addition of comonomers. Hence particle sizes ranged from 100 to 1000 nm, tunable by the preparation conditions. All materials were characterized by photon cross correlation spectroscopy, scanning electron microscopy and elemental mapping investigations. Furthermore, first catalytic tests were carried out by temperature programmed oxidation (TPO) of methane, and the activity of this material in lowering the onset temperature of methane combustion by 262 K was documented.

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Synthesis, Optical Properties, and Sensing Applications of LaF3:Yb3+/Er3+/Ho3+/Tm3+ Upconversion Nanoparticles

Nanomaterials ◽

10.3390/nano10122477 ◽

2020 ◽

Vol 10 (12) ◽

pp. 2477

Author(s):

Hsiu-Wen Chien ◽

Chien-Hao Huang ◽

Chien-Hsin Yang ◽

Tzong-Liu Wang

Keyword(s):

Ligand Exchange ◽

Near Infrared ◽

Upconversion Nanoparticles ◽

Core Shell ◽

Particle Sizes ◽

X Ray Diffraction ◽

Water Dispersible ◽

Sensing Applications ◽

Transmission Electron ◽

Doping Ratio

Herein, we successfully synthesized a series of LaF3:Yb3+/Er3+/Ho3+/Tm3+ upconversion nanoparticles (UCNPs) and LaF3:Yb3+0.20, Er3+0.02@LaF3:Yb3+0.20 core/shell UCNPs by modifying the amount of NaOH and the reaction time. Hexagonal LaF3 nanocrystals with uniform particle sizes and bright UC emissions were obtained. The crystal structures of the lanthanide-doped LaF3 UCNPs were investigated using wide-angle X-ray diffraction. The morphologies and particle sizes of the nanocrystals were determined using transmission electron microscopy. The photoluminescence (PL) spectra of the LaF3 nanocrystals could be tuned by altering the doping ratio of Er3+, Ho3+, and Tm3+. In addition, the PL intensities increased after coating the UCNP cores with an active shell. The fluorescence intensities of the UCNPs synthesized via a one-hour reaction with the addition of 2.5 or 5 mmol NaOH increased by up to 17 times compared with the sample prepared without the addition of NaOH. By modifying the doping ratio of Yb/Tm, UV-emissive LaF3 nanocrystals were obtained. After surface modification by ligand exchange, the hydrophobic LaF3:Yb3+0.20, Er3+0.02@LaF3:Yb3+0.20 core/shell UCNPs became water-dispersible. These colloid UCNPs could be utilized as a fluorescent probe for the detection of Hg2+ ions under 980 nm near-infrared irradiation.

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