scholarly journals Controlling the Electronic Properties of a Nanoporous Carbon Surface by Modifying the Pores with Alkali Metal Atoms

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 610
Author(s):  
Michael M. Slepchenkov ◽  
Igor S. Nefedov ◽  
Olga E. Glukhova
Keyword(s):  
Electronic Properties ◽  
Film Surface ◽  
Potassium Atom ◽  
Nanoporous Carbon ◽  
Carbon Surface ◽  
Effective Control ◽  
Adsorbed Hydrogen ◽  
Oh Groups ◽  
Carbon Framework ◽  
Almost All

We investigate a process of controlling the electronic properties of a surface of nanoporous carbon glass-like thin films when the surface pores are filled with potassium atoms. The presence of impurities on the surface in the form of chemically adsorbed hydrogen and oxygen atoms, and also in the form of hydroxyl (OH) groups, is taken into account. It is found that even in the presence of impurities, the work function of a carbon nanoporous glass-like film can be reduced by several tenths of an electron volt when the nanopores are filled with potassium atoms. At the same time, almost all potassium atoms are ionized, losing one electron, which passes to the carbon framework of the film. This is due to the nanosizes of the pores in which the electron clouds of the potassium atom interact maximally with the electrons of the carbon framework. As a result, this leads to an improvement in the electrical conductivity and an increase in the electron density at the Fermi level. Thus, we conclude that an increase in the number of nanosized pores on the film surface makes it possible to effectively modify it, providing an effective control of the electronic structure and emission properties.

Quick and Practical Cleaning Process for Silicon Carbide Epitaxial Reactor

2018 ◽  
Vol 924 ◽  
pp. 96-99
Author(s):  
Kohei Shioda ◽  
Keisuke Kurashima ◽  
Hitoshi Habuka ◽  
Hideki Ito ◽  
Shinichi Mitani ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Carbon Film ◽  
Film Surface ◽  
Chemical Vapor ◽  
Pyrolytic Carbon ◽  
Film Deposition ◽  
Carbon Surface ◽  
Cleaning Process ◽  
Silicon Carbide Film ◽  
Carbon Coated

In order to develop a quick and practical cleaning process for the silicon carbide chemical vapor deposition reactor, the pyrolytic carbon-coated susceptor was used. The 30-μm-thick silicon carbide film was formed on the susceptor; the film was cleaning by chlorine trifluoride gas at 460 °C for 15 min. The remained fluorine was removed by the annealing at 900 °C in ambient hydrogen. The pyrolytic carbon surface did not suffer from any damage, because the pyrolytic carbon film surface morphology after the cleaning process was the same as that before the silicon carbide film deposition.

scholarly journals Vaccination policy in Italy: An update

2018 ◽  
Author(s):  
Stefano Crenna ◽  
Antonio Osculati ◽  
Silvia D. Visonà
Keyword(s):  
Point Of View ◽  
Vaccine Hesitancy ◽  
Effective Control ◽  
Pharmaceutical Companies ◽  
Vaccination Policy ◽  
Vaccine Preventable Diseases ◽  
Italian Law ◽  
Fertile Ground ◽  
Almost All ◽  
Administrative Sanctions

The effective control of vaccine-preventable diseases generally requires indefinite maintenance of extremely high rates of timely vaccination. Therefore, vaccine hesitancy is of paramount importance and needs to be addressed. In Italy, regulations about vaccinations are controversial and, to some extent, inconsistent. Even though the childhood vaccinations are mandatory by law (Italian Law n. 891/1939, n. 292/1963, n.51/1966 and n. 165/1991), the limited deterrent effectiveness of the sanctioning system, and the changes introduced by the Italian Constitutional Law n. 3/2001 (devolution of almost all the competences and responsibilities in health matters to the Regions and the Autonomous Provinces), were the fertile ground in which new vaccine policies were generated and developed, radically different from the existing ones: many Regions, based on what was decided in 2005 - on an experimental basis - by the State-Regions Conference, decided to abolish the vaccination obligation and/or to stop the imposition of administrative sanctions on non-compliant parents. In addition, since then, there is a worrying tendency to decline vaccinations due to the parents’ mistrust in pharmaceutical companies and health policies. Therefore, recently, the Italian government decided to deploy an emergency ordinance (Italian Decree Law n. 73/2017). In this article, the authors are going to illustrate the current situation in Italy concerning vaccination policy, from a legislative and social point of view.

scholarly journals Carbon-Doped Boron Nitride Nanomesh: Stability and Electronic Properties of Adsorbed Hydrogen and Oxygen

2014 ◽  
Vol 118 (41) ◽  
pp. 23888-23896 ◽  
Author(s):  
G. C. Loh ◽  
Sandeep Nigam ◽  
G. Mallick ◽  
Ravindra Pandey
Keyword(s):  
Boron Nitride ◽  
Electronic Properties ◽  
Adsorbed Hydrogen ◽  
Carbon Doped

scholarly journals Ethylene Adsorption Using Cobalt Oxide-Loaded Polymer-Derived Nanoporous Carbon and Its Application to Extend Shelf Life of Fruit

Molecules ◽  
2019 ◽  
Vol 24 (8) ◽  
pp. 1507 ◽  
Author(s):  
Imam Prasetyo ◽  
Nur Indah Fajar Mukti ◽  
Teguh Ariyanto
Keyword(s):  
Shelf Life ◽  
Cobalt Oxide ◽  
High Surface ◽  
High Surface Area ◽  
Nanoporous Carbon ◽  
Carbon Surface ◽  
Calcination Process ◽  
Weight Percentage ◽  
Ethylene Adsorption ◽  
Ethylene Removal

Suppressing the amount of ethylene during storage has been of interest as a method to enhance shelf life of fruit. In this work, ethylene removal by adsorption using cobalt oxide-impregnated nanoporous carbon has been studied. Nanoporous carbon with a high surface area up to 2400 m2 g−1 was prepared by carbonization process biomass and synthetic polymer at 850 °C. Dispersion of cobalt oxide on porous carbon surface was carried out by an incipient wetness procedure followed by calcination process at 200 °C. Ethylene adsorption test was performed using a volumetric method in an ultrahigh vacuum rig constructed by Swagelok VCR® fittings. The results showed that the cobalt oxide/carbon system had significant ethylene adsorption capacity. Ethylene uptake increases with the increasing cobalt oxide loading on the carbon. The highest ethylene capacity of 16 mol kg−1 adsorbent was obtained by using 30 wt.% (weight percentage) of cobalt oxide dispersed in polymer-derived carbon. In closed storage, the ratio of 15 g adsorbent/kg fruit may extend the storage life up to 12 d, higher than that without adsorbent (3 d). Therefore, the results demonstrate the great potential use of cobalt oxide-impregnated nanoporous carbon as an adsorbent for ethylene removal during storage of fruit.

The Influence of W Filament Alloying on the Electronic Properties of Hwcvd Deposited a-Si:H Films

2000 ◽  
Vol 609 ◽  
Author(s):  
A. H. Mahan ◽  
A. Mason ◽  
B. P. Nelson ◽  
A. C. Gallagher
Keyword(s):  
Electronic Properties ◽  
Diffusion Length ◽  
Depth Profiling ◽  
Film Surface ◽  
Film Deposition ◽  
Alloy Formation ◽  
Central Regions ◽  
Film Deposition Rate ◽  
Filament Surface ◽  
Post Deposition

ABSTRACTIn depositing a-Si:H by HWCVD using W filaments, one issue common to this technique is that of filament lifetime. When using undiluted silane as the source gas, a buildup of silicon at the colder ends of the filament is routinely observed (thickening), and it is here that filament breakage usually occurs. Less well understood is the effect of filament alloy formation on a-Si:H electronic properties. In this work we combine ambipolar diffusion length (SSPG) measurements on consecutively deposited a-Si:H films with SEM surface topography and sputter (SP) Auger depth profiling of the filament Si/(W+Si) composition to track film electronic properties as a function of the Si buildup on short filaments entirely exposed to the growing film surface. We find that with increasing exposure time of the filament to silane, appreciable Si exists everywhere along the filament length, even in the non-thickened central regions. We discuss the effect of this alloying on the film deposition rate and electronic properties, and suggest that the nature of the filament surface must be carefully considered when optimizing a- Si:H film electronic properties. Finally, we discuss possible ways to minimize this alloying by post deposition treatments, which include different filament ‘run’ temperatures.

Chitosan Film Sensor (CFS) for Detecting Fertilizer Concentration of Grape Tree

2014 ◽  
Vol 679 ◽  
pp. 137-144
Author(s):  
Roshida Mustaffa ◽  
Irwana Nainggolan ◽  
Tulus Ikhsan Nasution ◽  
Rafezi Ahmad Khairel ◽  
Nazree Derman
Keyword(s):  
Magnesium Sulphate ◽  
Chitosan Film ◽  
Film Surface ◽  
Ammonium Molybdate ◽  
Time Stability ◽  
Film Sensor ◽  
Oh Groups ◽  
Sem Image ◽  
Recovery Response ◽  
Main Components

A method to detect fertilizer concentration of grape tree using chitosan film sensors (CFS) with 1.75% w/v has been developed. Electrochemical deposition has been chosen as an efficient technique for the fabrication of CFS. CFS has been used to detect different concentration of fertilizer ranging from 0 ppm until 60 ppm. The types of fertilizers used in this testing were magnesium sulphate and ammonium molybdate. The electrical laboratory testing result of the CFS shows the de-ionised water (DIW) has the highest response with the value ~81%. The highest response values of CFS of magnesium sulphate and ammonium molybdate content of 10 ppm concentration were ~52% and ~35% respectively. The lowest response values of CFS of magnesium sulphate and ammonium molybdate content of 60 ppm concentration were ~13.5% and ~16% respectively. The results have been proven that CFS can differentiate concentration of fertilizers. The morphological surfaces of CFS were observed with SEM and FTIR. SEM image of CFS showed the film surface was compact and the chitosan was well distributed. FTIR result shows there were N-H and OH groups in chitosan film where they were the main components to sense the fertilizer concentrations. The CFS can fulfil all the reliable sensing properties which include excellent sensitivity, recovery, response time, stability, repeatability and selectivity.

Anodization of Nanoporous Carbons for Removal of Ammonia

2005 ◽  
Vol 23 ◽  
pp. 7-10
Author(s):  
Soo Jin Park ◽  
Jun-Sik Shin
Keyword(s):  
Carbon Adsorbent ◽  
Nanoporous Carbon ◽  
Ammonia Removal ◽  
Nanoporous Carbons ◽  
Ammonia Gas ◽  
Oh Groups ◽  
Surface Areas ◽  
Effective Removal ◽  
Acid And Base ◽  
Anodic Oxidation Treatment

In this study, a new nanoporous carbon was prepared by anodic oxidation treatment to remove noxic ammonia gas. The acid- and base values of the nanoporous carbon were determined by Boehm’s titration method. And, the surface properties of the carbons were investigated by XPS analysis. Also, N2/77K adsorption isotherm characteristics, including the specific surface areas and nano/micropore volumes were studied by BET and t-plot methods, respectively. The ammonia removal efficiency was confirmed by gas-detecting tube technique. As a result, it was revealed in the case of acidic treatment on nanoporous carbons that the ammonia removal was greatly effective due to the increase of OH groups in carbon surfaces without significant changes of nanostructural properties. It was then found that the acidic anodization of nanoporous carbons was a suitable method for the effective removal of ammonia gas, which could be attributed to the increase of acceptor-donor interactions between acidic oxygen functional groups of carbon adsorbent and basic adsorbate in an adsorbent-adsorbate system.

Molecular Orientation of Polymer Lubricant Films: Its Tribological Consequence

1998 ◽  
Vol 120 (2) ◽  
pp. 369-378 ◽  
Author(s):  
Chao Gao ◽  
Tam Vo ◽  
Joel Weiss
Keyword(s):  
Molecular Orientation ◽  
Energy State ◽  
Tribological Performance ◽  
Lubricant Film ◽  
Carbon Surface ◽  
Lubricant Layer ◽  
Significant Difference ◽  
End Groups ◽  
Lubricant Films ◽  
Almost All

The objective of this paper is to demonstrate, from experiments and modeling, how and why molecular orientation of functional end groups of perfluoro-polyether (PFPE) lubricants play an important role in the tribological performance of thin film magnetic disks. These disks typically have an amorphous carbon overcoat upon which a thin lubricant layer is deposited using dip-coating technique. Glancing-angle FTIR (Fourier Transform Infra-Red Spectrometry) is used for measuring molecular orientation of planer functional end groups. A molecular orientation index (MOI) was defined as 1 for randomly oriented functional end groups. The MOI is mathematically derived as 3 (maximum) for lubricant molecules oriented with their functional end groups perpendicular to the surface, and as 0 (minimum) if lubricant molecules oriented with their functional end groups parallel to the surface. The MOI is shown to depend on processing conditions and lubricant film thickness. The tribological performance of the lubricant films was evaluated using drag-mode contact start-stop testing. It was found that wear durability of the lubricant films (~2 nm) with MOI ~ 1.5 is a few times better than those with MOI ~ 0.5 to 1.0. No significant difference in the amount of bonded lubricant film was detected over the range of MOI studied. Nor was there a detectable relationship with hydrophobicity. It was inferred from decreased MOI values due to thermal effects and storage time that a smaller MOI value corresponds to a lower free energy state of the lubricant film. Interestingly, MOI values for bonded lubricant films for Process A are found to be close to 3.0, suggesting that almost all functional end groups in the bonded films are oriented perpendicular to the carbon surface, close to 2.0 for process B, and close to 0 for process C, meaning that almost all functional end groups in the bonded films from process C are oriented parallel to the carbon surface. Relationship between physical/chemical bonding configurations and MOI values are graphically presented in detail. Based on this relation, a simple model on lubricant film structures for the three processes studied is presented. The model MOI values agree very well with measured MOI values as a function of lubricant thickness for all three processes, and the model also appears to account for the observed tribology performance for the MOI values studied (0.5 ~ 1.5).

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