Preparation, ignition, and combustion of mechanically alloyed Al-Mg powders with customized particle sizes

2013 ◽  
Vol 1521 ◽  
Author(s):  
Yasmine Aly ◽  
Vern K. Hoffman ◽  
Mirko Schoenitz ◽  
Edward L. Dreizin
Keyword(s):  
Particle Size ◽  
Ignition Delay ◽  
Pure Aluminum ◽  
Particle Morphology ◽  
Combustion Characteristics ◽  
Particle Sizes ◽  
Mechanically Alloyed ◽  
Pressurization Rate ◽  
Improved Performance ◽  
Ignition And Combustion

ABSTRACTAdding aluminum to propellants, pyrotechnics, and explosives is a common way to boost their energy density. A number of approaches have been investigated that shorten aluminum ignition delay, increase combustion rate, and decrease the tendency of aluminum droplets to agglomerate. Previous work showed that particles of mechanically alloyed Al-Mg powders burn faster than similarly sized particles of pure aluminum. However, preparation of mechanically alloyed powders with particle sizes matching those of fine aluminum used in energetic formulations was not achieved. This work is focused on preparation of mechanically alloyed, composite Al-Mg powders in which both internal structures and particle size distributions are adjusted. Binary powders with compositions in the range of 50 - 90 at. % Al were prepared and characterized. Milling protocol is optimized to prepare equiaxial, micron-scale particles suitable for laboratory evaluations of their oxidation, ignition, and combustion characteristics. Quantitative particle size analyses are done using low-angle laser light scattering. Electron microscopy and x-ray diffraction are used to examine particle morphology and phase makeup, respectively. Combustion of aerosolized powder clouds is studied using a constant volume explosion setup. For all materials, ignition and combustion characteristics are compared to each other and to those of pure Al. Compositions with improved performance (i.e., shorter ignition delay and faster pressurization rate) compared to pure Al are identified.

Surface energy of cellulosic materials: The effect of particle morphology, particle size, and hydroxyl number

TAPPI Journal ◽  
2015 ◽  
Vol 14 (9) ◽  
pp. 565-576 ◽  
Author(s):  
YUCHENG PENG ◽  
DOUGLAS J. GARDNER
Keyword(s):  
Particle Size ◽  
Surface Energy ◽  
Particle Morphology ◽  
Nanofibrillated Cellulose ◽  
Particle Sizes ◽  
Hydroxyl Number ◽  
Small Individual ◽  
Dispersion Component ◽  
Commercial Applications ◽  
Lower Temperature

Understanding the surface properties of cellulose materials is important for proper commercial applications. The effect of particle size, particle morphology, and hydroxyl number on the surface energy of three microcrystalline cellulose (MCC) preparations and one nanofibrillated cellulose (NFC) preparation were investigated using inverse gas chromatography at column temperatures ranging from 30ºC to 60ºC. The mean particle sizes for the three MCC samples and the NFC sample were 120.1, 62.3, 13.9, and 9.3 μm. The corresponding dispersion components of surface energy at 30°C were 55.7 ± 0.1, 59.7 ± 1.3, 71.7 ± 1.0, and 57.4 ± 0.3 mJ/m2. MCC samples are agglomerates of small individual cellulose particles. The different particle sizes and morphologies of the three MCC samples resulted in various hydroxyl numbers, which in turn affected their dispersion component of surface energy. Cellulose samples exhibiting a higher hydroxyl number have a higher dispersion component of surface energy. The dispersion component of surface energy of all the cellulose samples decreased linearly with increasing temperature. MCC samples with larger agglomerates had a lower temperature coefficient of dispersion component of surface energy.

Dynamic Hydrothermal Synthesis of Super-Low Density Xonotlite Thermal Insulation Materials from Industrial Quartz Powder

2017 ◽  
Vol 726 ◽  
pp. 569-575 ◽  
Author(s):  
Hong Zhi Yue ◽  
Xin Wang ◽  
Zan Zhong Yang ◽  
Chun Cheng Wei
Keyword(s):  
Particle Size ◽  
Thermal Insulation ◽  
Particle Morphology ◽  
Zirconium Oxychloride ◽  
Low Density ◽  
Particle Sizes ◽  
Quartz Powder ◽  
Insulation Materials ◽  
The Common ◽  
Very High

Xonotlite was synthesized by dynamic hydrothermal methode with industrial quartz powder as the siliceous materials and calcium hydroxide derived from hydration of calcined calcium carbonate as calcareous material.This paper focused on the influence of particle size of the industrial quartz powder, the mass ratio of water and solid reactants (W/S) and additives on the product composition, apparent density and crystal morphology. The products were characterized by X-ray powder diffraction (XRD), scanning eletron microscope (SEM) and other analysis methodes. Results indicated that in a certain range to decrease particle sizes of quartz powder could improve the content of xonotlite under the help of potassium hydroxide and zirconium oxychloride, the content of xonotlite could reach 99.5% when the particle size of quartz powder decrease to 4.65um no need to the common level of below 1 um in some literature. The product had a very high xonotlite content and perfect particle morphology when the ratio of W/S was controled over 30%; under the help of strontium ions and zirconium ions xonotlite fiber became significantly slimmer with a greater ratio of length to diameter,which was easier to obtain super-low density xonotlite thermal insulation materials.

Effects of C particle size on the ignition and combustion characteristics of the SHS reaction in the 20wt.% Ni–Ti–C system

2008 ◽  
Vol 460 (1-2) ◽  
pp. 276-282 ◽  
Author(s):  
Y.F. Yang ◽  
H.Y. Wang ◽  
R.Y. Zhao ◽  
Y.H. Liang ◽  
L. Zhan ◽  
...  
Keyword(s):  
Particle Size ◽  
Combustion Characteristics ◽  
Ignition And Combustion

scholarly journals Investigations on the Modifications in Ignition Delay Time of Shellac-based Pyrotechnic Igniter using Additives of Varying Particle Size

2020 ◽  
Author(s):  
Lakshay Bansal ◽  
Prakhar Jindal ◽  
Manish Kumar Bharti
Keyword(s):  
Particle Size ◽  
Activated Carbon ◽  
Iron Oxide ◽  
Ignition Delay ◽  
Delay Time ◽  
Base Composition ◽  
Ignition Delay Time ◽  
Particle Sizes ◽  
Opposite Trend ◽  
Pyrotechnic Compositions

Modifications achieved in the ignition delay time of shellac-based pyrotechnic igniter using different additives of varying particle size are observed and compared. 40 different pyrotechnic compositions were prepared using five additives i.e. aluminium, magnesium, red iron oxide, naphthalene and activated carbon. Four particle sizes i.e. <75 µm, 75-150 µm, 150-300 µm, 300-600 µm and two weight percentages of the additives i.e. 3% and 5% were investigated. A base composition, without any additive, was also prepared to compare and investigate the effects of additives and their particle size on the ignition delay time of the composition. The incorporation of additives significantly reduced the ignition delay time of the base composition. Addition of 5% red iron oxide having a particle size of <75 µm, delivered the maximum decrement in ignition delay time i.e. by 49.7%. Naphthalene of particle size of <75 µm added as 3% in the composition weight, provided the minimum reduction in the ignition delay time i.e. by 13.7%. It was also observed that all of the additives exhibited a similar manner of decrement in ignition delay time as the particle size decreased, except for naphthalene which exhibited an opposite trend.

Nb-W Alloy Prepared by Mechanical Alloying and Optimal Design of Corresponding Milling Variables

2014 ◽  
Vol 1033-1034 ◽  
pp. 839-848
Author(s):  
Bai Ru Li ◽  
Yong Dong Wang ◽  
Xing Liu
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Particle Size ◽  
Milling Time ◽  
Milled Powder ◽  
Orthogonal Test ◽  
Particle Sizes ◽  
Liquid Ratio ◽  
Mechanically Alloyed ◽  
Fe Content

The effects of milling variables on the particle sizes and purity of mechanically alloyed Nb-30W powders were quantitatively investigated using orthogonal test of three factors consisting of milling time A (12h, 24h and 48h), ball-to-powder ratio B (6:1, 10:1 and 20:1) and solid-to-liquid ratio C (1:0.2, 1:0.5 and 1:1) at three levels in order to optimize the milling variables of mechanically alloyed Nb-30W powders. Results indicated that the particle size was mainly determined by the solid-to-liquid ratio and the purity of powder was mainly affected by the ball-to-powder ratio and the milling time; best combination of all variables was found to be A2B2C1 with the particle size 12.62μm and Fe content 0.399%. After hot pressed, A2B2C1 combination obtained the highest mechanical properties. With the refining of particles during milling, the Fe contaminations of milled powder increased and were dissolved into Nb lattices to form Nb (Fe) solid solution; meanwhile, macro stress caused by plastic deformation of Nb particles was released.

Effect of particle size on indicator gas emission during high-temperature oxidation of weathered coal

2020 ◽  
Author(s):  
JiaJia Song ◽  
Jun Deng ◽  
JingYu Zhao
Keyword(s):  
Particle Size ◽  
High Temperature ◽  
High Temperature Oxidation ◽  
Spontaneous Combustion ◽  
Combustion Characteristics ◽  
Particle Sizes ◽  
Gas Emission ◽  
Temperature Oxidation ◽  
Weathered Coal ◽  
Effect Of Particle Size

&lt;p&gt;Coal spontaneous combustion is one of the severe nature hazards among nature resources. There are many influence factors which control the development of spontaneous combustion such as particle size, oxygen concentration, etc. Weathering effects alter the spontaneous combustion characteristics of coal. To explore the effect of particle size on gas emission from weathered coal under high temperature oxygen deficiency, the macroscopic spontaneous combustion characteristics of weathered coal with various particle sizes in high temperature oxidation process were studied. The gas concentration of different particle sizes with weathered coal oxidation from normal temperature to 600 &amp;#176;C was tested by the self-built high temperature program experiment system, and the variation law of the indicator gas was analyzed. The results showed that there were different experimental phenomena in each particle size coal sample. The concentration of indicator gas neither increased nor decreased monotonically with the change of particle size. Roughly, 3 mm is the critical particle size in the process of high temperature oxidation of weathered coal. The experimental results provided a pivotal theoretical basis for the early prediction and the scientific prevention of the spontaneous combustion of the weathered coal during the mining process of the open pit and the shallow coal seam.&lt;/p&gt;

EFFECT OF MOISTURE AND PARTICLE SIZE ON THE COMBUSTION CHARACTERISTICS OF SEWAGE SLUDGE IN A FIXED BED

2018 ◽  
Author(s):  
Joana Freitas Campana ◽  
Kaio Pandolfi Pessotti ◽  
Carlos Eduardo Silva Abreu ◽  
Patrick de Jesus
Keyword(s):  
Particle Size ◽  
Sewage Sludge ◽  
Fixed Bed ◽  
Combustion Characteristics ◽  
Effect Of Moisture

scholarly journals Effect of particle size on phytochemical composition and antioxidant properties of Sargassum cristaefolium ethanol extract

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
E. S. Prasedya ◽  
A. Frediansyah ◽  
N. W. R. Martyasari ◽  
B. K. Ilhami ◽  
A. S. Abidin ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Particle Size ◽  
Antioxidant Activities ◽  
Antioxidant Properties ◽  
Ethanol Extract ◽  
Total Phenolic ◽  
Particle Sizes ◽  
Epicatechin Gallate ◽  
Particle Size Reduction ◽  
Phytochemical Composition

AbstractSample particle size is an important parameter in the solid–liquid extraction system of natural products for obtaining their bioactive compounds. This study evaluates the effect of sample particle size on the phytochemical composition and antioxidant activity of brown macroalgae Sargassum cristaefolium. The crude ethanol extract was extracted from dried powders of S.cristeafolium with various particle sizes (> 4000 µm, > 250 µm, > 125 µm, > 45 µm, and < 45 µm). The ethanolic extracts of S.cristaefolium were analysed for Total Phenolic Content (TPC), Total Flavonoid Content (TFC), phenolic compound concentration and antioxidant activities. The extract yield and phytochemical composition were more abundant in smaller particle sizes. Furthermore, the TPC (14.19 ± 2.08 mg GAE/g extract to 43.27 ± 2.56 mg GAE/g extract) and TFC (9.6 ± 1.8 mg QE/g extract to 70.27 ± 3.59 mg QE/g extract) values also significantly increased as particle sizes decreased. In addition, phenolic compounds epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), and Epigallocatechin gallate (EGCG) concentration were frequently increased in samples of smaller particle sizes based on two-way ANOVA and Tukey’s multiple comparison analysis. These results correlate with the significantly stronger antioxidant activity in samples with smaller particle sizes. The smallest particle size (< 45 µm) demonstrated the strongest antioxidant activity based on DPPH, ABTS, hydroxyl assay and FRAP. In addition, ramp function graph evaluates the desired particle size for maximum phytochemical composition and antioxidant activity is 44 µm. In conclusion, current results show the importance of particle size reduction of macroalgae samples to increase the effectivity of its biological activity.

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