The role of the porosity and oxygen groups on the adsorption of n-alkanes, benzene, trichloroethylene and 1,2-dichloroethane on active carbons at zero surface coverage

ABSTRACTWe present new results of kinetic studies of the deposition of high quality a-Si:H which strongly support the reaction mechanism suggested in our earlier papers: 1. SiH4 → SiH2; 2. SiH2 + SiS4 → Si2H6 (SiH2 + Si2H6 → Si3H6); 3. Si2H6 → 2a-Si:H (Si3H8 → 3a-Si:H). The “SiH3 mechanism”, as promoted by several workers, is in contradiction with these experimental facts.The di- and trisilane, which have a much higher reactive sticking coefficient than monosilane, play the role of reactive intermediates which facilitate the heterogeneous decomposition of silicon carrying species at the surface of the growing film. The values of the reactive sticking coefficient of Si2H6 and Si3H8 depend on the surface coverage by chemisorbed hydrogen; they increase with decreasing surface coverage. Under the conditions of the growth of high quality a-Si:H films the reactive sticking coefficient of disilane amounts to 10−4 to 10−2 which is in a good agreement with recent data of other authors.The rate determining step of the growth of high quality a-Si:H films is the desorption of hydrogen from the surface of the growing film. This can be strongly enhanced by ion bombardment at impact energy of <100 eV. In this way, homogeneous, good quality films were deposited at rates up to 1800 Angströms/min, and there is a well justified hope that this rate can be further increased.

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Changes in the Adsorption Properties of Activated Carbon due to Partial Oxidation of the Surface

Adsorption Science & Technology ◽

10.1177/026361749501200305 ◽

1995 ◽

Vol 12 (3) ◽

pp. 211-219 ◽

Cited By ~ 13

Author(s):

A.M. Youssef ◽

A.A. El-Khouly ◽

A.I. Ahmed ◽

E.I. El-Shafey

Keyword(s):

Water Vapour ◽

Surface Coverage ◽

Activated Carbons ◽

Textural Properties ◽

Isosteric Heat ◽

Adsorption Properties ◽

Adsorption Of Water ◽

Oxygen Groups ◽

Initial Adsorption ◽

Entropy Of Adsorption

The textural properties (surface area and porosity) of activated carbons change upon treatment with oxidizing solutions. The extent of this change is related to the strength of the oxidizing agent. Oxidation also changes the chemistry of the surface by forming carbon–oxygen groups which are the sites upon which the initial adsorption of water vapour takes place. The adsorption of water vapour at 300–320 K is mainly physical and the isosteric heat of adsorption decreases continuously as the surface coverage increases. The entropy of adsorption of water vapour on untreated and oxidized carbons, at different adsorption temperatures, has been calculated.

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Facile Synthesis of a Tailored-Designed Au/Pt Nanoanode for Enhanced Formic Acid, Methanol, and Ethylene Glycol Electrooxidation

Journal of Nanomaterials ◽

10.1155/2019/2784708 ◽

2019 ◽

Vol 2019 ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Islam M. Al-Akraa ◽

Yaser M. Asal ◽

Ahmad M. Mohammad

Keyword(s):

Ethylene Glycol ◽

Formic Acid ◽

Energy Demand ◽

Liquid Fuel ◽

Surface Coverage ◽

Co Adsorption ◽

Catalytic Performance ◽

Onset Potential ◽

Anodic Reactions

The recent revolution in nanoscience and global energy demand have motivated research in liquid fuel cells (LFCs) due to their enhanced efficiency, moving flexibility, and reduced contamination. In line with this advancement, a glassy carbon (GC) electrode was modified with platinum (PtNPs) and gold (AuNPs) nanoparticles to fabricate a nanosized anode for formic acid, methanol, and ethylene glycol electrooxidation (abbreviated, respectively, to FAO, MO, and EGO), of the key anodic reactions of LFCs. The deposition sequence of the catalyst’s layers was important where the Au/Pt/GC electrode (in which PtNPs were directly deposited onto the GC surface followed by AuNPs—surface coverage ≈ 32%) exhibited the best catalytic performance. The catalytic performance of the Au/Pt/GC anode excelled (at least threefold) its value obtained at the Pt/GC anode with regard to FAO and EGO, if the oxidation peak currents were compared. This enhancement got reduced to 1.4 times in the case of MO, but the large decrease (− 220 mV) in the onset potential of MO provided compensation. The role of AuNPs in the Au/Pt/GC catalyst was principal in boosting its catalytic performance as it immunized the underlying PtNPs against CO poisoning which is associated with the release of CO as an intermediate during the oxidation. Interestingly, AuNPs succeeded in interrupting the contiguity of the Pt surface sites required for CO adsorption during FAO, MO, and EGO and, thus, presage preventing the deterioration of the catalytic performance of their corresponding LFCs.

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Absence of Fibrinogen in Afibrinogenemia Results in Large but Loosely Packed Thrombi under Flow Conditions

Thrombosis and Haemostasis ◽

10.1055/s-0037-1615661 ◽

2001 ◽

Vol 85 (04) ◽

pp. 736-742 ◽

Cited By ~ 41

Author(s):

Ya-Ping Wu ◽

Martin IJsseldijk ◽

Jaap Zwaginga ◽

Jan Sixma ◽

Philip de Groot ◽

...

Keyword(s):

Morphological Analysis ◽

Surface Coverage ◽

Thrombus Formation ◽

Flow Conditions ◽

Thrombotic Complications ◽

Platelet Thrombus ◽

The Difference ◽

Adhesive Proteins ◽

Lamellipodia Formation

SummaryWe studied the role of fibrinogen in platelet thrombus formation under flow on adhesive proteins using afibrinogenemic blood (LMWH anticoagulated) in a perfusion system. Perfusions with afibrinogenemic blood showed strong increased surface coverage and thrombus volume that normalized upon addition of fibrinogen. Similar studies using citrate anticoagulated blood showed that this was due to fibrinogen and not fibrin. Morphological analysis showed that afibrinogenemic thrombi were loosely packed and consisted mainly of dendritic platelets that contacted one another through filopodia. However, in the presence of fibrinogen, platelets formed lamellipodia and spread out on top of one another. Studies with radiolabeled platelets showed similar numbers of platelets in both conditions demonstrating that the difference is one of packing and the larger size is due to absence of lamellipodia formation and spreading. The found increased thrombus size and loosely packed platelets might help to understand thrombotic complications sometimes seen in afibrinogenemia patients.

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