The Microscopic Structure of Adsorbed Water on Hydrophobic Surfaces under Ambient Conditions

Nano Letters ◽  
2011 ◽  
Vol 11 (12) ◽  
pp. 5581-5586 ◽  
Author(s):  
Peigen Cao ◽  
Ke Xu ◽  
Joseph O. Varghese ◽  
James R. Heath
Keyword(s):  
Adsorbed Water ◽  
Microscopic Structure ◽  
Ambient Conditions ◽  
Hydrophobic Surfaces

Chemical Vapor Deposited Graphene for Opto-Electronic Applications

2016 ◽  
Vol 39 ◽  
pp. 57-68
Author(s):  
Vikram Passi ◽  
Amit Gahoi ◽  
Sarah Riazimehr ◽  
Stefan Wagner ◽  
Andreas Bablich ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Spectral Response ◽  
Single Layer ◽  
Chemical Vapor ◽  
Adsorbed Water ◽  
Single Layer Graphene ◽  
Ambient Conditions ◽  
Transfer Length ◽  
Type Silicon ◽  
P Type

In this work, fabrication and characterisation of graphene photodiodes and transfer length method structures is presented. Graphene growth is carried out using a thermal chemical vapor deposition process on copper foils and subsequently transferred onto silicon-dioxide/silicon substrate. Comparison of electrical and optical characteristics of the photodiodes, which are fabricated on both n-type and p-type silicon, is shown. The photodiodes fabricated on n-type silicon show good rectifying behaviour when compared with photodiodes fabricated on p-type silicon. Spectral response of graphene photodiodes is measured to be less than 0.2 mAW-1 which is attributed to the light absorbance of 2.3% for single layer graphene. Transfer length method device structures are also fabricated and contact resistance is calculated and plotted as a function of spacing between the contacts. The calculated contact resistance (RcW) is 0.87 kΩ.µm. The latter structures are also characterised under various ambient conditions, before and after annealing. The value of contact resistance reduces from 0.87 kΩ.µm to 0.75 kΩ.µm after annealing. This reduction is attributed to the improvement in bonding between graphene and metal. Measurements under vacuum show an increase in contact resistance which is attributed to the removal of adsorbed water molecules on the surface on graphene. The sheet resistivity of graphene is calculated to be between 1.17 kΩ/□ and 3.67 kΩ/□.

Average molecular orientations in the adsorbed water layers on silicon oxide in ambient conditions

2008 ◽  
Vol 10 (32) ◽  
pp. 4981 ◽  
Author(s):  
Anna L. Barnette ◽  
David B. Asay ◽  
Seong H. Kim
Keyword(s):  
Silicon Oxide ◽  
Adsorbed Water ◽  
Ambient Conditions ◽  
Water Layers

Stability of Adsorbed Water on TiO2-TiN Interfaces. A First Principles and Ab Initio Thermodynamics Investigation.

2018 ◽  
Author(s):  
Michael Nolan ◽  
Julio Gutierrez ◽  
Pierre Loverra ◽  
Marco Fronzi ◽  
Alan O'Riordan
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Adsorbed Water ◽  
Free Energy Calculations ◽  
Ambient Conditions ◽  
High Concentration ◽  
High Coverage ◽  
Reducing Conditions ◽  
Atomistic Thermodynamics ◽  
The Stability

Titanium Nitride (TiN) surfaces can oxidise and the growth of a TiO<sub>x</sub> layer on the surface along with the likely presence of water in the surrounding environment can modify the properties of this widely used coating material. The present Density Functional Theory study, including Hubbard +U correction (DFT+U), investigates the stability of adsorbed water at TiO<sub>2</sub>-TiN interfaces with different defects, that serve as a model for an oxide layer grown on a TiN surface. Surface free energy calculations show the stability of perfect TiN-TiO<sub>2</sub> interface at regular O pressures, while oxygen vacancy-rich TiO<sub>1.88</sub>–TiN is more favourable at reducing conditions. An isolated water is preferentially adsorbed dissociatively at perfect and oxygen defective interfaces while molecular adsorption is more stable at higher coverages. The adsorption energy is stronger at the oxygen defective interfaces which arises from the high concentration of reduced Ti<sup>3+</sup> and strong interfacial atomic relaxations. Ab initio atomistic thermodynamics show that water will be present at high coverage on TiO<sub>2</sub>-TiN interfaces at ambient conditions and the pristine interface is only stable at very low pressure of O and H<sub>2</sub>O. The results of these DFT+U simulations are important for the fundamental understanding of wettability of interfacial systems involving metal oxides.

scholarly journals Mechanical Effects of Solid Water on the Particle Skeleton of Soil: Mechanism Analysis

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xiaomeng Duan
Keyword(s):  
Effective Stress ◽  
Water Pressure ◽  
Water Layer ◽  
Adsorbed Water ◽  
Interparticle Contact ◽  
Ambient Conditions ◽  
Stress Equation ◽  
Mechanical Effects ◽  
Solid Water ◽  
Interparticle Friction

It is generally accepted that the adsorbed water layer on the surface of the mineral particle has significant effects on the mechanical properties of soils. By defining the concepts of “solid water” and “particle skeleton” after a brief review on adsorbed water, therefore, the mechanical mechanism about how solid water affects the deformation and strength of particle skeleton is theoretically clarified, which could be the physical basis of the reasonability of two assumptive conditions for effective stress equation. Considering solid water as a two-dimensional liquid with appreciable normal strength and lubricity, if soil particles are always wrapped by solid-water layer, the only mechanical effect due to water pressure is to compress particles; while if the interparticle solid water could be extruded undergoing enough force with suitable confinement, the mechanical effects due to increasing water pressure are not only to compress particles more but also to enhance interparticle friction because the indirect interparticle contact could be changed into direct contact to consequently alter the interparticle friction. Because solid water is not likely to be extruded by pressure alone, if the particle compression is negligible relative to the soil-mass compression, two assumptive conditions for effective stress equation are reasonable. Moreover, a simple monitoring test on water content is conducted to certify that the solid-water layer should always exist in soils under ambient conditions, so the ordinarily oven-dried soil samples used in conventional geotechnical tests carried out under ambient conditions could be just “nominally dry” samples with the effects due to solid water.

scholarly journals Ion mobility and material transport on KBr in air as a function of the relative humidity

2019 ◽  
Vol 10 ◽  
pp. 2084-2093
Author(s):  
Dominik J Kirpal ◽  
Korbinian Pürckhauer ◽  
Alfred J Weymouth ◽  
Franz J Giessibl
Keyword(s):  
Ion Mobility ◽  
Water Layer ◽  
Adsorbed Water ◽  
Ambient Conditions ◽  
Material Transport ◽  
Surface Conditions ◽  
Force Microscopy ◽  
Atomic Force ◽  
Microscopy Images ◽  
Material Exchange

Surfaces exposed to air can change their structure due to external influences such as chemical reactions or material exchange and movement. The adsorbed water layer that is present under ambient conditions plays an important role especially for highly soluble materials. Surface atoms can easily diffuse into the thin water layer and, when surface conditions are favorable, they can re-attach to the surface. We collected atomic force microscopy images of KBr surfaces in a humidity-controlled glove box at various relative humidities below 40%. By scratching and poking the surface with the AFM tip, we constructed energetically unfavorable holes or scratch sites and material accumulations and recorded the evolution of these defects as a function of the time. We observed an exponential decay of the size of the defects and material accumulations, and from this data we determined energy barriers to dissolution and aggregation of approximately 0.9 eV.

Stability of Adsorbed Water on TiO2-TiN Interfaces. A First Principles and Ab Initio Thermodynamics Investigation.

2018 ◽  
Author(s):  
Michael Nolan ◽  
Julio Gutierrez ◽  
Pierre Loverra ◽  
Marco Fronzi ◽  
Alan O'Riordan
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Adsorbed Water ◽  
Free Energy Calculations ◽  
Ambient Conditions ◽  
High Concentration ◽  
High Coverage ◽  
Reducing Conditions ◽  
Atomistic Thermodynamics ◽  
The Stability

Titanium Nitride (TiN) surfaces can oxidise and the growth of a TiO<sub>x</sub> layer on the surface along with the likely presence of water in the surrounding environment can modify the properties of this widely used coating material. The present Density Functional Theory study, including Hubbard +U correction (DFT+U), investigates the stability of adsorbed water at TiO<sub>2</sub>-TiN interfaces with different defects, that serve as a model for an oxide layer grown on a TiN surface. Surface free energy calculations show the stability of perfect TiN-TiO<sub>2</sub> interface at regular O pressures, while oxygen vacancy-rich TiO<sub>1.88</sub>–TiN is more favourable at reducing conditions. An isolated water is preferentially adsorbed dissociatively at perfect and oxygen defective interfaces while molecular adsorption is more stable at higher coverages. The adsorption energy is stronger at the oxygen defective interfaces which arises from the high concentration of reduced Ti<sup>3+</sup> and strong interfacial atomic relaxations. Ab initio atomistic thermodynamics show that water will be present at high coverage on TiO<sub>2</sub>-TiN interfaces at ambient conditions and the pristine interface is only stable at very low pressure of O and H<sub>2</sub>O. The results of these DFT+U simulations are important for the fundamental understanding of wettability of interfacial systems involving metal oxides.

Multi-method characterization of the ferrihydrite to goethite transformation

Clay Minerals ◽  
2011 ◽  
Vol 46 (3) ◽  
pp. 387-395 ◽  
Author(s):  
G. Houben ◽  
S. Kaufhold
Keyword(s):  
Cation Exchange ◽  
Surface Area ◽  
Iron Oxides ◽  
Cation Exchange Capacity ◽  
Gas Adsorption ◽  
Adsorbed Water ◽  
Exchange Capacity ◽  
Infrared Analysis ◽  
Ambient Conditions ◽  
Data Set

AbstractThe reactivity of soils and sediments is often described by parameters such as the specific surface area (SSA) and the cation exchange capacity (CEC). Both, however, are bulk values controlled by the presence and crystallinity of different phases, e.g. clay minerals and iron oxides. Amongst the latter, ferrihydrite and goethite are the most abundant minerals. Goethite gradually forms from a ferrihydrite precursor, a process involving a decrease in surface area. Today the BET gas adsorption technique is the most common method to measure SSA. In this study, BET surface areas of synthetic and natural ferrihydrite and goethite of variable crystallinity were compared to (a) mineral-specific measurements, including infrared analysis (IR), differential thermal analysis (DTA), and (b) bulk methods, such as cation exchange capacity and oxalate-soluble iron. Correlations showed that the SSA can be indirectly inferred from all methods. There is no general correlation between IR and BET measurements due to the variability of adsorbed water, which depends on drying and ambient conditions. DTA, particularly using the dehydroxylation peak at 300°C, allows quantification of the goethite content, and hence the SSA, because adsorbed water does not affect this peak. The data set of the present study enabled us to estimate either SSA and/or the content of iron oxides, even in natural mixtures, e.g. those in which smectites determine the SSA.

Hydrated form of some clay minerals observed using a film sealed environmental cell

1978 ◽  
Vol 36 (1) ◽  
pp. 72-73
Author(s):  
N. Kohyama ◽  
K. Fukushima ◽  
A. Fukami
Keyword(s):  
Clay Minerals ◽  
Morphological Changes ◽  
Carbon Film ◽  
Electron Microscopic Observation ◽  
Adsorbed Water ◽  
Electron Microscopic ◽  
Hydrated Form ◽  
Thin Carbon ◽  
Environmental Cell ◽  
Thin Carbon Film

Since the interlayer or adsorbed water of some clay minerals are quite easily dehydrated in dried air, in vacuum, or at moderate temperatures even in the atmosphere, the hydrated forms have not been observed by a conventional electron microscope(TEM). Recently, specific specimen chambers, “environmental cells(E.C.),” have been developed and confirmed to be effective for electron microscopic observation of wet specimen without dehydration. we observed hydrated forms of some clay minerals and their morphological changes by dehydration using a TEM equipped with an E.C..The E.C., equipped with a single hole copper-microgrid sealed by thin carbon-film, attaches to a TEM(JEM 7A) with an accelerating voltage 100KV and both gas pressure (from 760 Torr to vacuum) and relative humidity can be controlled. The samples collected from various localities in Japan were; tubular halloysite (l0Å) from Gumma Prefecture, sperical halloysite (l0Å) from Tochigi Pref., and intermediate halloysite containing both tubular and spherical types from Fukushima Pref..

Hydrogen bonding in liquid methanol at ambient conditions and at high pressure

2000 ◽  
Vol 98 (3) ◽  
pp. 125-134 ◽  
Author(s):  
T. Weitkamp, J. Neuefeind, H. E. Fisch
Keyword(s):  
High Pressure ◽  
Hydrogen Bonding ◽  
Ambient Conditions

A datum point for estimating the adsorbed water in hydrated portland cement

1963 ◽  
Vol 13 (9) ◽  
pp. 375-382
Author(s):  
R. F. Feldman ◽  
P. J. Sereda
Keyword(s):  
Portland Cement ◽  
Adsorbed Water
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