Porous Alumina Processing Using the Direct Foaming Technique Based on Slurry Boiling

2018 ◽  
Vol 766 ◽  
pp. 1-6
Author(s):  
Kritkaew Somton ◽  
Mana Rodchom ◽  
Pitak Laoratanakul ◽  
Ryan C. McCuiston
Keyword(s):  
Pore Size ◽  
Theoretical Calculations ◽  
Heated Surface ◽  
Porous Alumina ◽  
Bubble Diameter ◽  
Scanning Calorimetry ◽  
Direct Foaming ◽  
Solids Content ◽  
Direct Foaming Method ◽  
Size And Structure

The effect of slurry solids content was studied for a novel direct foaming method based on slurry boiling to produce porous alumina ceramics. Slurries with solids contents of 30 to 45 wt. % were produced by conventional processing methods. The physical properties of slurry density and surface tension were measured, as well as thermal properties such as specific heat and latent heat, which were obtained using differential scanning calorimetry (DSC). Samples were fabricated by boiling the slurries on a hot plate until the liquid was completely evaporated. The resultant porous samples were presintered at 1000 °C and were examined to determine the pore size and structure. The measured pore diameter of samples obtained from this experiment were compared with theoretical calculations of departing bubble diameter from a heated surface proposed by Fritz, and Cole & Rohsenow. It was found that the pore size had a relationship with slurry solids content depending on the thermal gradient. The pore size, at a position away from the heated surface, increased as the solids content increased. However, the pore size at the heated surface did not vary significantly with solids content. The results showed that a direct foaming method based on slurry boiling is capable of producing porous alumina and that solids content of the slurry may be utilized to somewhat control pore size and structure.

scholarly journals Fabrication and characterization of porous alumina with a surface layer composed of alumina platelet by direct-foaming method

2017 ◽  
Vol 125 (4) ◽  
pp. 375-377 ◽  
Author(s):  
Akihiro SHIMAMURA ◽  
Manabu FUKUSHIMA ◽  
Mikinori HOTTA ◽  
Tatsuki OHJI ◽  
Yu-ichi YOSHIZAWA ◽  
...  
Keyword(s):  
Surface Layer ◽  
Porous Alumina ◽  
Direct Foaming ◽  
Fabrication And Characterization ◽  
Direct Foaming Method

scholarly journals High-strength porous alumina ceramics prepared from stable wet foams

2021 ◽  
Author(s):  
Linying Wang ◽  
Liqiong An ◽  
Jin Zhao ◽  
Shunzo Shimai ◽  
Xiaojian Mao ◽  
...  
Keyword(s):  
Heat Insulation ◽  
Porous Alumina ◽  
High Strength ◽  
Porous Ceramics ◽  
High Porosity ◽  
Alumina Ceramics ◽  
Direct Foaming ◽  
Catalyst Carrier ◽  
Average Grain Size ◽  
Direct Foaming Method

AbstractPorous ceramics have been widely used in heat insulation, filtration, and as a catalyst carrier. Ceramics with high porosity and high strength are desired; however, this high porosity commonly results in low strength materials. In this study, porous alumina with high porosity and high strength was prepared by a popular direct foaming method based on particle-stabilized wet foam that used ammonium polyacrylate (PAA) and dodecyl trimethyl ammonium chloride (DTAC) as the dispersant and hydrophobic modifier, respectively. The effects of the dispersant and surfactant contents on the rheological properties of alumina slurries, stability of wet foams, and microstructure and mechanical properties of sintered ceramics were investigated. The microstructure of porous ceramics was regulated using wet foams to achieve high strength. For a given PAA content, the wet foams exhibited increasing stability with increasing DTAC content. The most stable wet foam was successfully obtained with 0.40 wt% PAA and 0.02 wt% DTAC. The corresponding porous alumina ceramics had a porosity of 82%, an average grain size of 0.7 µm, and a compressive strength of 39 MPa. However, for a given DTAC content, the wet foams had decreasing stability with increasing PAA content. A possible mechanism to explain these results is analyzed.

scholarly journals Bifunctional acid–base mesoporous silica@aqueous miscible organic-layered double hydroxides

RSC Advances ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 3749-3754 ◽  
Author(s):  
Hongri Suo ◽  
Haohong Duan ◽  
Chunping Chen ◽  
Jean-Charles Buffet ◽  
Dermot O'Hare
Keyword(s):  
Mesoporous Silica ◽  
Pore Size ◽  
Layered Double Hydroxides ◽  
High Surface ◽  
High Surface Area ◽  
Core Shell ◽  
Acid Base ◽  
Double Hydroxides ◽  
Hierarchical Morphology ◽  
Size And Structure

Core@shell materials which exhibit hierarchical morphology with ultra high surface area and controllable pore size and structure have been synthesised.

Salts of purine alkaloids caffeine and theobromine with 2,6-dihydroxybenzoic acid as coformer: structural, theoretical, thermal and spectroscopic studies

2021 ◽  
Vol 77 (11) ◽  
Author(s):  
Mateusz Gołdyn ◽  
Anna Komasa ◽  
Mateusz Pawlaczyk ◽  
Aneta Lewandowska ◽  
Elżbieta Bartoszak-Adamska
Keyword(s):  
Hydrogen Bonds ◽  
Water Solubility ◽  
Theoretical Calculations ◽  
Spectroscopic Studies ◽  
X Ray Diffraction ◽  
Dihydroxybenzoic Acid ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Purine Alkaloids ◽  
Vis Spectroscopy

The study of various forms of pharmaceutical substances with specific physicochemical properties suitable for putting them on the market is one of the elements of research in the pharmaceutical industry. A large proportion of active pharmaceutical ingredients (APIs) occur in the salt form. The use of an acidic coformer with a given structure and a suitable pK a value towards purine alkaloids containing a basic imidazole N atom can lead to salt formation. In this work, 2,6-dihydroxybenzoic acid (26DHBA) was used for cocrystallization of theobromine (TBR) and caffeine (CAF). Two novel salts, namely, theobrominium 2,6-dihydroxybenzoate, C7H9N4O2 +·C7H5O4 − (I), and caffeinium 2,6-dihydroxybenzoate, C8H11N4O2 +·C7H5O4 − (II), were synthesized. Both salts were obtained independently by slow evaporation from solution, by neat grinding and also by microwave-assisted slurry cocrystallization. Powder X-ray diffraction measurements proved the formation of the new substances. Single-crystal X-ray diffraction studies confirmed proton transfer between the given alkaloid and 26DHBA, and the formation of N—H...O hydrogen bonds in both I and II. Unlike the caffeine cations in II, the theobromine cations in I are paired by noncovalent N—H...O=C interactions and a cyclic array is observed. As expected, the two hydroxy groups in the 26DHBA anion in both salts are involved in two intramolecular O—H...O hydrogen bonds. C—H...O and π–π interactions further stabilize the crystal structures of both compounds. Steady-state UV–Vis spectroscopy showed changes in the water solubility of xanthines after ionizable complex formation. The obtained salts I and II were also characterized by theoretical calculations, Fourier-transform IR spectroscopy (FT–IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and elemental analysis.

The high porosity silicon nitride foams prepared by the direct foaming method

2019 ◽  
Vol 45 (2) ◽  
pp. 2124-2130 ◽  
Author(s):  
Zhongpei Du ◽  
Dongxu Yao ◽  
Yongfeng Xia ◽  
Kaihui Zuo ◽  
Jinwei Yin ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
High Porosity ◽  
Direct Foaming ◽  
Direct Foaming Method

scholarly journals Energetic Films Realized by Encapsulating Copper Azide in Silicon-Based Carbon Nanotube Arrays with Higher Electrostatic Safety

Micromachines ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 575 ◽  
Author(s):  
Xuwen Liu ◽  
Yan Hu ◽  
Hai Wei ◽  
Bingwen Chen ◽  
Yinghua Ye ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Porous Alumina ◽  
Chemical Vapor ◽  
Exothermic Peak ◽  
Alumina Film ◽  
Scanning Calorimetry ◽  
Micro Electro Mechanical Systems ◽  
Transmission Electron ◽  
Anodic Oxidation Method ◽  
Silicon Based

Since copper azide (Cu(N3)2) has high electrostatic sensitivity and is difficult to be practically applied, silicon-based Cu(N3)2@carbon nanotubes (CNTs) composite energetic films with higher electrostatic safety were fabricated, which can be compatible with micro-electro mechanical systems (MEMS). First, a silicon-based porous alumina film was prepared by a modified two-step anodic oxidation method. Next, CNTs were grown in pores of the silicon-based porous alumina film by chemical vapor deposition. Then, copper nanoparticles were deposited in CNTs by electrochemical deposition and oxidized to Cu(N3)2 by gaseous hydrogen azide. The morphology and composition of the prepared silicon-based Cu(N3)2@CNTs energetic films were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. The electrostatic sensitivity of the composite energetic film was tested by the Bruceton method. The thermal decomposition kinetics of the composite energetic films were studied by differential scanning calorimetry (DSC). The results show that the exothermic peak of the silicon-based Cu(N3)2@CNTs composite energetic film is at the temperature of 210.95 °C, its electrostatic sensitivity is significantly less than that of Cu(N3)2 and its 50% ignition energy is about 4.0 mJ. The energetic film shows good electric explosion characteristics and is successfully ignited by laser.

Numerical Simulation and Experimental Validation of the Dynamics of a Single Bubble During Pool Boiling Under Constant and Time-Varying Reduced Gravity Conditions

2003 ◽  
Author(s):  
H. S. Abarajith ◽  
D. M. Qiu ◽  
V. K. Dhir
Keyword(s):  
Numerical Simulation ◽  
Heated Surface ◽  
Bubble Diameter ◽  
Pool Boiling ◽  
Growth Period ◽  
Single Bubble ◽  
Time Varying ◽  
Reduced Gravity ◽  
System Pressure ◽  
Vapor Liquid

The numerical simulation and experimental validations of the growth and departure of a single bubble on a horizontal heated surface during pool boiling under reduced gravity conditions have been performed here. A finite difference scheme is used to solve the equations governing mass, momentum and energy in the vapor liquid phases. The vapor-liquid interface is captured by level set method, which is modified to include the influence of phase change at the liquid-vapor interface. The effects of reduced gravity conditions, wall superheat and liquid subcooling and system pressure on the bubble diameter and growth period have been studied. The simulations are also carried out under both constant and time-varying gravity conditions to benchmark the solution with the actual experimental conditions that existed during the parabolic flights of KC-135 aircraft. In the experiments, a single vapor bubble was produced on an artificial cavity, 10 μm in diameter microfabricated on the polished silicon wafer, the wafer was heated electrically from the back with miniature strain gage type heating elements in order to control the nucleation superheat. The bubble growth period and the bubble diameter predicted from the numerical simulations have been found to compare well with the data from experiments.

scholarly journals Electrical Monitoring as a Novel Route to Understanding the Aging Mechanisms of Carbon Nanotube-Doped Adhesive Film Joints

2020 ◽  
Vol 10 (7) ◽  
pp. 2566 ◽  
Author(s):  
Xoan F. Sánchez-Romate ◽  
Alberto Jiménez-Suárez ◽  
María Sánchez ◽  
Silvia G. Prolongo ◽  
Alfredo Güemes ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Theoretical Calculations ◽  
Electrical Response ◽  
Partial Recovery ◽  
Initial State ◽  
Scanning Calorimetry ◽  
Resistance Change ◽  
Adhesive Film ◽  
Lap Shear ◽  
Aging Conditions

Carbon fiber-reinforced plastic bonded joints with novel carbon nanotube (CNT) adhesive films were manufactured and tested under different aging conditions by varying the surfactant content added to enhance CNT dispersion. Single lap shear (SLS) tests were conducted in their initial state and after 1 and 2 months immersed in distilled water at 60 °C. In addition, their electrical response was measured in terms of the electrical resistance change through thickness. The lap shear strength showed an initial decrease due to plasticization of weak hydrogen bonds, and then a partial recovery due to secondary crosslinking. This plasticization effect was confirmed by differential scanning calorimetry analysis with a decrease in the glass transition temperature. The electrical response varied with aging conditions, showing a higher plasticity region in the 1-month SLS joints, and a sharper increase in the case of the non-aged and 2-month-aged samples; these changes were more prevalent with increasing surfactant content. By adjusting the measured electrical data to simple theoretical calculations, it was possible to establish the first estimation of damage accumulation, which was higher in the case of non-aged and 2-month-aged samples, due to the presence of more prevalent brittle mechanisms for the CNT-doped joints.

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