Preparation and Properties of Low Density Replica Carbon Foams

1992 ◽  
Vol 270 ◽  
Author(s):  
S. S. Hulsey ◽  
P. K. Poco
Keyword(s):  
Sodium Chloride ◽  
Pore Size ◽  
Laser Fusion ◽  
Low Density ◽  
Microporous Membranes ◽  
Leaching Process ◽  
Carbon Foams ◽  
Catalytic Supports ◽  
Inorganic Substrate

ABSTRACTLow density foams are used for a variety of applications, including catalytic supports, battery anodes, microporous membranes, and laser fusion targets. The technique for making replica carbon foams described in this paper has been previously reported[I] and involves a process in which an inorganic substrate (sodium chloride) is infused with a carbonizable polymer. After carbonization, the substrate is removed by a leaching process and the wet foam is dried; the resultant foam is referred to as replica carbon. This paper describes improvements in the processing which result in a smaller pore size and improved foam homogeneity.The original substrate is the single most important factor affecting the resultant structure. Techniques to improve the uniformity of the substrate and the translation of substrate anomalies into the final product are described.

scholarly journals Separation of virgin plastic polymers and post-consumer mixed plastic waste by sinking-flotation technique

2021 ◽  
Author(s):  
Orlando Washinton Meneses Quelal ◽  
Borja Velázquez-Martí ◽  
Andrés Ferrer Gisbert
Keyword(s):  
Sodium Chloride ◽  
Municipal Solid Waste ◽  
Solid Waste ◽  
Tap Water ◽  
Pilot Scale ◽  
Complete Separation ◽  
Plastic Waste ◽  
High Density ◽  
Low Density ◽  
Flotation Technique

Abstract The main objective of this research is to separate virgin polymers (PA, PC, PP, HDPE; PS and ABS) and post-consumer plastic waste from municipal solid waste (MSW) using the sinking-flotation technique. The separation was carried out on a pilot scale in a container of 800 l of useful volume with agitation of 160 rpm for one hour. Tap water, ethanol solutions and sodium chloride at different concentrations were used as the densification medium. The virgin polymers were separated into two groups, that is, a group of low-density polymers (HDPE and PP) and a group of high-density polymers (PS, ABS, PA, and PC). Polymers whose density was less than that of the medium solution floated to the surface, while those whose density was greater than that of the medium solution sank to the bottom. The experimental results showed that the complete separation of HDPE from PP was achieved at 23% v/v of ethanol. For the separation of the high-density polymers, up to 40% w / v sodium chloride was used. The recoveries of the polymers ranged from 70 to 99.70%. In post-consumer recycled plastic waste, fractions of 29.6% polyolefins, 37.54% PS, 11% ABS, 8% PA and 12% PC, PET and PVC were obtained. Finally, cast plates were made of the post-consumer waste to improve the identification of the type of polymer present in the separated fractions.

scholarly journals Revealing the True Morphological Structure of Macroporous Soft Hydrogels for Tissue Engineering

2020 ◽  
Vol 10 (19) ◽  
pp. 6672
Author(s):  
Bohumila Podhorská ◽  
Miroslav Vetrík ◽  
Eva Chylíková-Krumbholcová ◽  
Lucie Kománková ◽  
Niloufar Rashedi Banafshehvaragh ◽  
...  
Keyword(s):  
Sodium Chloride ◽  
Pore Size ◽  
Laser Scanning ◽  
Morphological Changes ◽  
3D Structure ◽  
Morphological Structure ◽  
Laser Scanning Confocal Microscopy ◽  
Future Application ◽  
Sem Images ◽  
Hydrogel Scaffolds

(1) Background: Macroporous hydrogel scaffolds based on poly [N-(2-hydroxypropyl) methacrylamide] are one of the widely studied biocompatible materials for tissue reparation and regeneration. This study investigated the morphological changes during hydrogel characterization which can significantly influence their future application. (2) Methods: Three types of macroporous soft hydrogels differing in pore size were prepared. The macroporosity was achieved by the addition of sacrificial template particles of sodium chloride of various sizes (0–30, 30–50, and 50–90 µm) to the polymerizing mixture. The 3D structure of the hydrogels was then investigated by scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM). The SEM was performed with specimens rapidly frozen to various temperatures, while non-frozen gels were visualized with LSCM. (3 and 4) Results and Conclusion: In comparison to LSCM, the SEM images revealed a significant alteration in the mean pore size and appearance of newly formed multiple connections between the pores, depending on the freezing conditions. Additionally, after freezing for SEM, the gel matrix between the pores and the fine pores collapsed. LSCM visualization aided the understanding of the dynamics of pore generation using sodium chloride, providing the direct observation of hydrogel scaffolds with the growing cells. Moreover, the reconstructed confocal z-stacks were a promising tool to quantify the swollen hydrogel volume reconstruction which is not possible with SEM.

scholarly journals Improved isolation of normal human reticulocytes via exploitation of chloride-dependent potassium transport

Blood ◽  
1992 ◽  
Vol 80 (1) ◽  
pp. 249-254 ◽  
Author(s):  
MP Sorette ◽  
K Shiffer ◽  
MR Clark
Keyword(s):  
Sodium Chloride ◽  
Density Gradient ◽  
Gradient Methods ◽  
Low Density ◽  
High Potassium ◽  
Cation Composition ◽  
Density Fraction ◽  
High Sodium ◽  
Density Fractions ◽  
Normal Human

Abstract Studies on normal human reticulocytes have been limited by a lack of methods for effective reticulocyte enrichment. This study shows a convenient new approach for selective enrichment of reticulocytes from normal blood samples. We have developed a modified arabinogalactan density gradient that contains high potassium levels, approximating the internal cation composition of red blood cells (RBC). The low-density populations from this gradient are enriched in reticulocytes, and the highly selected lowest density fraction shows a much higher reticulocyte enrichment than that obtained with high sodium chloride arabinogalactan density gradients, or other previously reported density gradient methods. We found that this improved isolation is caused by suppression of potassium loss and reticulocyte dehydration via chloride (KCI) cotransport. When the low-density fraction of RBC from a high- potassium gradient was subsequently incubated in high sodium chloride medium and reseparated on a sodium chloride density gradient, the reticulocytes dehydrated and were recovered in high-density fractions. The highest-density fractions from this secondary gradient yield 95% to 99% reticulocytes. We anticipate that this method will benefit investigators who require reticulocyte enriched populations for a wide variety of applications.

scholarly journals Quantitative Nondestructive Density Determinations of Very Low-Density Carbon Foams

1992 ◽  
pp. 387-393
Author(s):  
W. E. Moddeman ◽  
D. P. Kramer ◽  
D. W. Firsich ◽  
P. D. Trainer ◽  
P. S. Back ◽  
...  
Keyword(s):  
Low Density ◽  
Carbon Foams

The Effect of Stretching on UHWMPE Microporous Film by Thermally Induced Phase Separation Method

2020 ◽  
Vol 993 ◽  
pp. 906-914
Author(s):  
Xiao Na Wang ◽  
Yue Mu ◽  
Guo Qun Zhao ◽  
Jia Cheng Gao ◽  
You Lei Zhou ◽  
...  
Keyword(s):  
Phase Separation ◽  
Pore Structure ◽  
Pore Size ◽  
Liquid Paraffin ◽  
Great Influence ◽  
Practical Significance ◽  
Microporous Membranes ◽  
Thermally Induced Phase Separation ◽  
Thermally Induced ◽  
Stretching Ratio

UHMWPE microporous membranes were prepared via thermally induced phase separation(TIPS) combining with stretching. TIPS method was adopted to resolve processing difficulties of UHMEPE, and the subsequent stretching was used to optimize pore structure. The preparation process utilized liquid paraffin (LP) as the diluent. The effect of different stretching ratios on pore structure was investigated through SEM, XRD and mercury intrusion test. The results indicated that stretching process not only greatly improved the pore size uniformity and pore distribution uniformity, but also had a great influence on pore size controlling. When the stretching ratio was lower than 80%, the pore size was concentrated in nano-region which pore size distribution was around 0.02-0.03 μm. While the stretching ratio was larger than 80%, due to bridging breakage and liquid paraffin movement, pore size was concentrated in the micron area where pore size mainly distributed around 1μm, which had a practical significance for controlling the pore size of membranes in industrial production. And it’s obtained that at the same concentration of UHMWPE, the microporous membranes prepared in this study have more uniform pore structures than those reported previously.

Nanoporous Silica for Low k Dielectrics

1996 ◽  
Vol 443 ◽  
Author(s):  
Teresa Ramos ◽  
Kevin Roderick ◽  
Alok Maskara ◽  
Douglas M. Smith
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Film Thickness ◽  
Pore Size ◽  
Ambient Pressure ◽  
Porous Solids ◽  
Nanoporous Silica ◽  
Low Density ◽  
Trade Offs ◽  
Small Pore

AbstractConsiderable progress has been made in development of thin films of nanoporous silica (also known as aerogels or low density xerogels) for ILD and IMD applications. Advantages of these materials include high thermal stability, small pore size, and similarity to conventional deposition processes, precursors and final material (silica). We have previously reported success in synthesizing low density, low dielectric constant (K<2) thin films using ambient pressure processing. However, processing of those films was complicated due to large number of process steps and difficulties in independently controlling both film thickness and film porosity.Nanoglass has now developed a new process which considerably reduces the number of process steps and allows independent control of both film thickness and porosity. The dielectric constant of the films can be tailored between 1.3 and 2.5. These films have improved mechanical properties due to controlled pore size and narrow pore size distribution and also because of higher density. The trade-offs between density, mechanical strength and dielectric constant for these types of porous solids will be elucidated. The known properties of the film and the process flow for deposition and post-deposition curing and the role of the relative rates of reaction, gelation, aging, and drying will be presented.

Ultra-low density carbon foams produced by pulsed laser deposition

Carbon ◽  
2013 ◽  
Vol 56 ◽  
pp. 358-365 ◽  
Author(s):  
A. Zani ◽  
D. Dellasega ◽  
V. Russo ◽  
M. Passoni
Keyword(s):  
Pulsed Laser Deposition ◽  
Pulsed Laser ◽  
Laser Deposition ◽  
Low Density ◽  
Carbon Foams
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