Microwave Preparation of Mullite Powders

1988 ◽  
Vol 124 ◽  
Author(s):  
Sridhar Komarneni ◽  
Else Breval ◽  
Rustum Roy
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Microwave Heating ◽  
Single Phase ◽  
Processing Parameters ◽  
Microwave Processing ◽  
Microwave Oven ◽  
Fine Powders ◽  
Diphasic Gels

ABSTRACTMullite, Al6Si2O13 composition gels were made by the single phase and diphasic routes. The wet mullite gels were heated in the insulated cavity of an ordinary kitchen microwave oven (2.45 GHz; 700 watts). Crystalline mullite powders were obtained from single phase gels while the diphasic gels yielded α-Al2O3 and mullite in a matter of 20–25 minutes of microwave heating. Trans- mission electron microscopy showed that the mullite particle size varied between 50 nm to 1 μm. The results of this study suggest that fine powders of mullite can be obtained from single phase mullite gels by optimizing the microwave processing parameters.

Synthesis of intermetallic NiAl and Ni3Al fine powders through organometallic precursors

1991 ◽  
Vol 6 (5) ◽  
pp. 928-934 ◽  
Author(s):  
Osami Abe ◽  
Akira Tsuge
Keyword(s):  
Heat Treatment ◽  
Thermal Decomposition ◽  
Particle Size ◽  
Aqueous Solutions ◽  
Single Phase ◽  
Initial Step ◽  
The Other ◽  
Fine Powders ◽  
Organometallic Precursors ◽  
Step Heat Treatment

Fine powders of intermetallic NiAl and Ni3Al were synthesized through organometallic precursors, which were coprecipitated from aqueous solutions of NiCl2 and AlCl3 by the addition of ammonium benzoate and hydradinium monochloride as precipitants. Ni3Al and NiAl were synthesized by a two-step heat treatment of the precursors. The initial step was the thermal decomposition of organic groups to form homogeneous mixtures of Ni3C, amorphous Al2O3, and free C below 1000 °C. The other step was the reaction above 1300 °C to form the intermetallics. Single phase powders of NiAl and Ni3Al with the particle size less than 3 μm were obtained above 1300 and 1400 °C, respectively.

scholarly journals Facile Synthesis of Single-Phase Alpha-Tungsten Nanopowders from Ammonium Paratungstate by RF Induction Thermal Plasma and Thermochemical Reduction

2020 ◽  
Vol 58 (11) ◽  
pp. 798-807
Author(s):  
Dongyoon Shin ◽  
Hyun-Woo Shim ◽  
Basudev Swain ◽  
Kyung-Soo Park ◽  
Chan-Gi Lee
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Plasma Treatment ◽  
Thermal Plasma ◽  
Single Phase ◽  
Morphological Evolution ◽  
Synthesis Conditions ◽  
Ammonium Paratungstate ◽  
Induction Thermal Plasma ◽  
Thermochemical Reduction

Facile, economic methods of preparing tungsten (W) nanopowder are critically needed to meet industrial demand. Herein, we report a method of preparing single-phase alpha-W (α-W) nanopowders using ammonium paratungstate (APT) as a starting material and the optimum synthesis conditions. The process involves two stages: i) the radio-frequency (RF) induction thermal plasma treatment of APT, followed by ii) thermochemical reduction at 600-900 <sup>o</sup>C. The crystallographic phase and morphological evolution of all products were systematically investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM), and the effects of the annealing temperature on the phase and particle size of the obtained powders were also evaluated. When the RF induction thermal plasma treatment was conducted with and without H<sub>2</sub>, the XRD and FESEM results showed the formation of mixed-phase α- and beta-W (β-W) nanopowder and WO<sub>3</sub> nanopowder, respectively. Single-phase α-W nanopowder was achieved by annealing the WO<sub>3</sub> nanopowder in an H<sub>2</sub> reductive atmosphere at 700 <sup>o</sup>C for 10 min, resulting in homogenous nanoparticles with a small particle size (d50) of 21.16 nm without any aggregation.

Analytical Electron Microscopy study of two vehicle-aged automotive exhaust catalysts having dissimilar activities

1989 ◽  
Vol 47 ◽  
pp. 272-273
Author(s):  
Sooho Kim ◽  
M. J. D’Aniello
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Noble Metal ◽  
Catalyst Deactivation ◽  
Analytical Electron Microscopy ◽  
Microscopy Study ◽  
Metal Particles ◽  
Automotive Exhaust ◽  
Exhaust Catalysts ◽  
Analytical Electron

Automotive catalysts generally lose-agtivity during vehicle operation due to several well-known deactivation mechanisms. To gain a more fundamental understanding of catalyst deactivation, the microscopic details of fresh and vehicle-aged commercial pelleted automotive exhaust catalysts containing Pt, Pd and Rh were studied by employing Analytical Electron Microscopy (AEM). Two different vehicle-aged samples containing similar poison levels but having different catalytic activities (denoted better and poorer) were selected for this study.The general microstructure of the supports and the noble metal particles of the two catalysts looks similar; the noble metal particles were generally found to be spherical and often faceted. However, the average noble metal particle size on the poorer catalyst (21 nm) was larger than that on the better catalyst (16 nm). These sizes represent a significant increase over that found on the fresh catalyst (8 nm). The activity of these catalysts decreases as the observed particle size increases.

Preparation, Characterization and In-vitro release of Piroxicam-loaded Solid Lipid Nanoparticles

2010 ◽  
Vol 3 (3) ◽  
pp. 1136-1146
Author(s):  
V K Verma ◽  
Ram A
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Solid Lipid Nanoparticles ◽  
In Vitro Release ◽  
Entrapment Efficiency ◽  
Lipid Nanoparticles ◽  
Diffusion Method ◽  
Solid Lipid ◽  
Vitro Release

 Solid lipid nanoparticles (SLNs) of piroxicam where produced by solvent emulsification diffusion method in a solvent saturated system. The SLNs where composed of tripamitin lipid, polyvinyl alcohol (PVAL) stabilizer, and solvent ethyl acetate. All the formulation were subjected to particle size analysis, zeta potential, drug entrapment efficiency, percent drug loading determination and in-vitro release studies. The SLNs formed were nano-size range with maximum entrapment efficiency. Formulation with 435nm in particle size and 85% drug entrapment was subjected to scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for surface morphology, differential scanning calorimetry (DSC) for thermal analysis and short term stability studies. SEM and TEM confirm that the SLNs are nanometric size and circular in shape. The drug release behavior from SLNs suspension exhibited biphasic pattern with an initial burst and prolong release over 24 h. 

Isolasi Dan Karakterisasi Bentonit Alam Menjadi Nanopartikel Monmorillonit

2018 ◽  
Vol 3 (1) ◽  
pp. 12 ◽  
Author(s):  
Zaimahwati Zaimahwati ◽  
Yuniati Yuniati ◽  
Ramzi Jalal ◽  
Syahman Zhafiri ◽  
Yuli Yetri
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Particle Size ◽  
Surface Morphology ◽  
Average Diameter ◽  
Particle Size Analyzer ◽  
Ft Ir ◽  
Scanning Electron ◽  
Sedimentation Processes

<p>Pada penelitian ini telah dilakukan isolasi dan karakterisasi bentonit alam menjadi nanopartikel montmorillonit. Bentonit alam yang digunakan diambil dari desa Blangdalam, Kecamatan Nisam Kabupaten Aceh Utara.  Proses isolasi meliputi proses pelarutan dengan aquades, ultrasonic dan proses sedimentasi. Untuk mengetahui karakterisasi montmorillonit dilakukan uji FT-IR, X-RD dan uji morfologi permukaan dengan Scanning Electron Microscopy (SEM). Partikel size analyzer untuk menganalisis dan menentukan ukuran nanopartikel dari isolasi bentonit alam. Dari hasil penelitian didapat ukuran nanopartikel montmorillonit hasil isolasi dari bentonit alam diperoleh berdiameter rata-rata 82,15 nm.</p><p><em>In this research we have isolated and characterized natural bentonite into montmorillonite nanoparticles. Natural bentonite used was taken from Blangdalam village, Nisam sub-district, North Aceh district. The isolation process includes dissolving process with aquades, ultrasonic and sedimentation processes.  The characterization of montmorillonite, FT-IR, X-RD and surface morphology test by Scanning Electron Microscopy (SEM). Particle size analyzer to analyze and determine the size of nanoparticles from natural bentonite insulation. From the research results obtained the size of montmorillonite nanoparticles isolated from natural bentonite obtained an average diameter of 82.15 nm.</em></p>

scholarly journals New approach in process intensification based on subcritical water, as green solvent, in propolis oil in water nanoemulsion preparation

2021 ◽  
Vol 10 (1) ◽  
pp. 208-218
Author(s):  
Fatemeh Ghavidel ◽  
Afshin Javadi ◽  
Navideh Anarjan ◽  
Hoda Jafarizadeh-Malmiri
Keyword(s):  
Antioxidant Activity ◽  
Particle Size ◽  
Zeta Potential ◽  
Subcritical Water ◽  
Process Intensification ◽  
Processing Parameters ◽  
Bioactive Materials ◽  
Propolis Extract ◽  
High Antibacterial Activity ◽  
Oil In Water

Abstract Subcritical water was used to provide propolis oil in water (O/W) nanoemulsions. To monitor and detect the main bioactive compounds of the prepared propolis extract, gas chromatography demonstrated that there were 47 bioactive materials in the propolis extract, among which pinostrobin chalcone and pinocembrin were the two key components. Effectiveness of two processing parameters such as the amount of saponin (0.5–2.0 g) and propolis extract (0.1–0.6 g), on particle size, polydispersity index (PDI), zeta potential, and antioxidant activity of the provided nanoemulsions, was evaluated. Results demonstrated that more desirable propolis O/W nanoemulsion, with minimum particle size (144.06 nm) and PDI (0.286), and maximum zeta potential (−21.71 mV) and antioxidant activity (90.86%) were made using 0.50 g of saponin and 0.53 g of propolis extract. Further analysis revealed that the prepared nanoemulsion based on optimum processing conditions had spherical shaped propolis nanodroplets in the colloidal solution with turbidity and maximum broad absorption peak of 0.08 a.u. and 292 nm, respectively. The prepared nanoemulsion had high antibacterial activity against both selected bacteria strains namely, Staphylococcus aureus and Escherichia coli.

scholarly journals A Thermally Conductive Pt/AAO Catalyst for Hydrogen Passive Autocatalytic Recombination

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 491
Author(s):  
Alina E. Kozhukhova ◽  
Stephanus P. du Preez ◽  
Aleksander A. Malakhov ◽  
Dmitri G. Bessarabov
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Combustion Temperature ◽  
Volume Fraction ◽  
Morphological Characteristics ◽  
Al Alloy ◽  
Impregnation Method ◽  
Case Scenario ◽  
Worst Case ◽  
Thermal Distribution

In this study, a Pt/anodized aluminum oxide (AAO) catalyst was prepared by the anodization of an Al alloy (Al6082, 97.5% Al), followed by the incorporation of Pt via an incipient wet impregnation method. Then, the Pt/AAO catalyst was evaluated for autocatalytic hydrogen recombination. The Pt/AAO catalyst’s morphological characteristics were determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The average Pt particle size was determined to be 3.0 ± 0.6 nm. This Pt/AAO catalyst was tested for the combustion of lean hydrogen (0.5–4 vol% H2 in the air) in a recombiner section testing station. The thermal distribution throughout the catalytic surface was investigated at 3 vol% hydrogen (H2) using an infrared camera. The Al/AAO system had a high thermal conductivity, which prevents the formation of hotspots (areas where localized surface temperature is higher than an average temperature across the entire catalyst surface). In turn, the Pt stability was enhanced during catalytic hydrogen combustion (CHC). A temperature gradient over 70 mm of the Pt/AAO catalyst was 23 °C and 42 °C for catalysts with uniform and nonuniform (worst-case scenario) Pt distributions. The commercial computational fluid dynamics (CFD) code STAR-CCM+ was used to compare the experimentally observed and numerically simulated thermal distribution of the Pt/AAO catalyst. The effect of the initial H2 volume fraction on the combustion temperature and conversion of H2 was investigated. The activation energy for CHC on the Pt/AAO catalyst was 19.2 kJ/mol. Prolonged CHC was performed to assess the durability (reactive metal stability and catalytic activity) of the Pt/AAO catalyst. A stable combustion temperature of 162.8 ± 8.0 °C was maintained over 530 h of CHC. To confirm that Pt aggregation was avoided, the Pt particle size and distribution were determined by TEM before and after prolonged CHC.

scholarly journals Functional Properties and Molecular Degradation of Schizostachyum Brachycladum Bamboo Cellulose Nanofibre in PLA-Chitosan Bionanocomposites

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 2008
Author(s):  
Samsul Rizal ◽  
N. I. Saharudin ◽  
N. G. Olaiya ◽  
H. P. S. Abdul Khalil ◽  
M. K. Mohamad Haafiz ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Moisture Content ◽  
Polymeric Materials ◽  
Particle Size Analysis ◽  
Size Analysis ◽  
Thickness Swelling ◽  
Compression Moulding ◽  
Ft Ir ◽  
Degradation Properties

The degradation and mechanical properties of potential polymeric materials used for green manufacturing are significant determinants. In this study, cellulose nanofibre was prepared from Schizostachyum brachycladum bamboo and used as reinforcement in the PLA/chitosan matrix using melt extrusion and compression moulding method. The cellulose nanofibre(CNF) was isolated using supercritical carbon dioxide and high-pressure homogenisation. The isolated CNF was characterised with transmission electron microscopy (TEM), FT-IR, zeta potential and particle size analysis. The mechanical, physical, and degradation properties of the resulting biocomposite were studied with moisture content, density, thickness swelling, tensile, flexural, scanning electron microscopy, thermogravimetry, and biodegradability analysis. The TEM, FT-IR, and particle size results showed successful isolation of cellulose nanofibre using this method. The result showed that the physical, mechanical, and degradation properties of PLA/chitosan/CNF biocomposite were significantly enhanced with cellulose nanofibre. The density, thickness swelling, and moisture content increased with the addition of CNF. Also, tensile strength and modulus; flexural strength and modulus increased; while the elongation reduced. The carbon residue from the thermal degradation and the glass transition temperature of the PLA/chitosan/CNF biocomposite was observed to increase with the addition of CNF. The result showed that the biocomposite has potential for green and sustainable industrial application.

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