scholarly journals Adsorbed water-molecule hexagons with unexpected rotations in islands on Ru(0001) and Pd(111)

2012 ◽  
Vol 85 (15) ◽  
Author(s):  
Sabine Maier ◽  
Ingeborg Stass ◽  
Toshiyuki Mitsui ◽  
Peter J. Feibelman ◽  
Konrad Thürmer ◽  
...  
Keyword(s):  
Water Molecule ◽  
Adsorbed Water ◽  
Adsorbed Water Molecule

Theoretical Insights into the Role of Water Molecule in The Aqueous/Cu(111) Interface during Corrosion Pathway

2014 ◽  
Vol 19 (4) ◽  
pp. 235-240
Author(s):  
Jun Hu ◽  
Xiao-yong Fan ◽  
Chao-Ming Wang
Keyword(s):  
Water Molecule ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Adsorbed Water ◽  
Dipole Interaction ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Adsorbed Water Molecule ◽  
The One

The absorption and possible reaction paths during corrosion have been systematically identified at the molecular level by us-ing density functional theory calculations. The results show that the co-adsorbed water molecule has a two-fold impact on the corrosive kinetics process. The one is the solvation effect, where water molecule affects the various reactions through ion dipole interaction, without bond fracture and formation. Another is the H-transfer mediator, where the bond of co-adsorbed water molecule breaks and regenerates in order to transfer hydrogen atoms.

Water Molecule Adsorption on Vertically Aligned Single-Walled Carbon Nanotubes

2014 ◽  
Author(s):  
Hiroyuki Moroizumi ◽  
Shohei Chiashi ◽  
Yasuyuki Takata ◽  
Masamichi Kohno
Keyword(s):  
Raman Spectroscopy ◽  
Water Molecule ◽  
Adsorbed Water ◽  
Radial Breathing Mode ◽  
Defective Structure ◽  
Single Walled Carbon ◽  
Adsorbed Water Molecule ◽  
Two Samples ◽  
Nano Channel ◽  
Vertically Aligned

A single walled carbon nanotube, which adsorbed water molecule in its nano channel, was observed using Raman spectroscopy, and two samples’ spectrums were compared under the same conditions. The SWNT samples that were vertically aligned on the silicon substrate were used. One of the samples was not covered by polymer whereas the other sample was covered by polymer. In our experiment, a nano channel was made using a nanosecond pulse laser (Nd:YAG laser). In order to adjust the focus, the sample was set on the automatic stage and controlled on the PC using a USB camera to watch closely. By moving the stage for over 30 seconds, the sample was processed to make the nano channel. The cell with the laser-processed sample in it was set on the Raman spectroscopy’s platform. Then, the cell was connected to the vacuum chamber and erlenmeyer flask by the valve. Both of the valves were opened first and left for a while to make the cell vacuum. Second, the vacuum chamber’s valve was closed and left for a while to let water molecule spread in the cell. Finally, the SWNT successfully adsorbed water molecule in its nano channel. Ar-ion laser was used in the Raman spectroscopy and the laser wavelength is 488nm. With the Raman spectroscopy, Radial Breathing Mode (RBM), D-band, and G-band were mainly observed. The RBM, D-band, and G-band originated from radial vibration frequency, defective structure, and graphite structure respectively. According to the sample types, the RBM spectrums were compared in our experiment.

Molecular Orbital Modeling of Water Adsorption on a Tetrasiloxane Ring

1990 ◽  
Vol 180 ◽  
Author(s):  
J. K. West ◽  
S. Wallace
Keyword(s):  
Water Molecule ◽  
Molecular Orbital ◽  
Water Adsorption ◽  
Adsorbed Water ◽  
Metal Alkoxide ◽  
Sioh Group ◽  
Vibrational Overtone ◽  
Neglect Of Differential Overlap ◽  
Mo Theory ◽  
Hydrogen Bonded

ABSTRACTA water molecule hydrogen bonded to a surface SiOH group produces an IR vibrational transmission peak (ν3) at 2.82 μm. Water was adsorbed into the pores of a metal alkoxide derived silica gel monolith, and the increase in the wavelength of the first vibrational overtone (2ν3) of this peak was measured as a function of the adsorbed water content W (g H2O/g SiO2). The peak shifted from 1.390 to 1.420 μm as W increased by 0.14 g/g. Intermediate Neglect of Differential Overlap (INDO) Molecular Orbital (MO) theory was used to model this process. The effect of a H2O molecule, hydrogen bonded to a hydroxylated tetrasiloxane ring, on the structure of the ring and the water molecule was investigated. The bond length of the O-H group H-bonded to the water molecule increased, as expected from the increase in wavelength of the 2ν3 IR peak.

A theoretical treatment of cation exchangers - III. The hydration of cations in polystyrene sulphonates

1955 ◽  
Vol 228 (1174) ◽  
pp. 322-341 ◽  
Keyword(s):  
Water Molecule ◽  
Water Activity ◽  
Adsorption Isotherms ◽  
Liquid Water ◽  
Adsorbed Water ◽  
Isopiestic Method ◽  
Water Molecules ◽  
Hydration Water ◽  
Monovalent Cations ◽  
Free Energies

The adsorption of water by the polystyrene sulphonates of cations has been investigated at 0 and 25° C, using an isopiestic method. The adsorption isotherm and the heats (enthalpies) and entropies of hydration have been obtained for the monovalent cations H, Li, Na, K, Cs, NH4, Ag and for the divalent cations Be, Mg, Ca, Sr, Ba, Hg. With the exception of H, which gives a smooth enthalpy-water-content curve, all monovalent cations show a more or less marked step in the differential enthalpy of adsorbed water between the first and second water molecule adsorbed per ion, thereafter the steps are less clearly defined. The differential entropies show similarities to those calculated for a B. E. T. isotherm, except that the curves show two minima which correspond to approximately 0.15 and 1.5 molecules of water/ion. The adsorption isotherms follow more or less the model of the B. E. T. isotherm, with several significant differences: ( a ) the volatility of the second and further water molecule/ion is not that of liquid water, but only tends to reach this value after several molecules/ion are adsorbed, and the energy levels of the first successive water molecules, though rising rapidly, differ substantially from that of liquid water; ( b ) the adsorption process of the first water molecule is significantly different from a Langmuir mechanism, and varies approximately as the one-half power of the water activity. The knowledge of the free energies, enthalpies and entropies permits a fair analysis of the hydration mechanism into its individual steps, which then permits a calculation of the standard state enthalpies and entropies of the first hydration steps. Both functions show a markedly linear relationship with the ionic radius of the unhydrated ion when summed up for the first two water molecules adsorbed. The knowledge of the adsorption isotherms permits one to differentiate between water adsorbed with zero free energy (swelling water) and the excess adsorbed water (cationic and anionic hydration water). The amount of hydration water associated with the cations has been obtained in this way both for mono- and divalent ions. The amount varies both with the water activity and with temperature. It is clear from the small free energies of hydration of all monovalent ions that the association of almost all water molecules is very loose, and is not related to the co-ordination number of the ions.

scholarly journals Effect of -O- on Water Molecule Adsorption and Adsorption Mechanism of Lignite and Coke

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Xue Bai ◽  
Yue Yin Song ◽  
Ying Yue Teng ◽  
Wen Lu Zhang ◽  
Yin Min Song ◽  
...  
Keyword(s):  
Water Molecule ◽  
1H Nmr ◽  
Adsorption Mechanism ◽  
Adsorbed Water ◽  
Proton Nuclear Magnetic Resonance ◽  
Special Role ◽  
Adsorption Mechanisms ◽  
Molecule Adsorption ◽  
Different Temperatures ◽  
Moisture Desorption

The high moisture content of lignite restricts its extensive and efficient use. Furthermore, the reabsorption of lignite is also a factor that affects lignite spontaneous combustion. Therefore, it is of great importance to study the process and mechanism of water molecule desorption and adsorption on lignite and coke (25–950°C) to achieve the clean and efficient utilization of lignite and environmental protection. Proton nuclear magnetic resonance (1H-NMR), thermogravimetric analysis, and other techniques were used in this study to explore the water molecule absorption and desorption processes of lignite pyrolysis at different temperatures (25–950°C) and the special contributions of ether bonds to water molecule adsorption. A mechanism of lignite water molecule adsorption was proposed. The results showed that ether bonds played a special role in the water molecule adsorption by pyrolyzed lignite. The ether bond content was greater in the coal samples at 300 and 950°C, which changed the trend of lignite water molecule absorption and the distribution of water (T2) detected in the 1H-NMR experiments and delayed the escape of water molecules during moisture desorption. The total amount of adsorbed water decreased first and then increased in the coal samples as the pyrolysis temperature increased. However, the maximum adsorption interactions of each coal sample increased first and then decreased. This was the result of the interactions between the pores and the oxygen-containing functional groups. Based on the above analysis, water molecule adsorption mechanism models of lignite and coke were constructed. This study offers a new approach for investigating the water molecule adsorption and adsorption mechanisms of lignite and coke.

scholarly journals Pristine and hydrated fluoroapatite (0001)

2019 ◽  
Vol 75 (5) ◽  
pp. 830-838
Author(s):  
Xavier Torrelles ◽  
Immad M. Nadeem ◽  
Anna Kupka ◽  
Adrián Crespo-Villanueva ◽  
Sandrina Meis ◽  
...  
Keyword(s):  
Water Molecule ◽  
Experimental Analysis ◽  
Surface Coverage ◽  
Adsorbed Water ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crystal Truncation Rod ◽  
Before And After ◽  
Dry Conditions

The surface structure of fluoroapatite (0001) (FAp0001) under quasi-dry and humid conditions has been probed with surface X-ray diffraction (SXRD). Lateral and perpendicular atomic relaxations corresponding to the FAp0001 termination before and after H2O exposure and the location of the adsorbed water molecules have been determined from experimental analysis of the crystal truncation rod (CTR) intensities. The surface under dry conditions exhibits a bulk termination with relaxations in the outermost atomic layers. The hydrated surface is formed by a disordered partially occupied H2O layer containing one water molecule (33% surface coverage) adsorbed at each of the three surface Ca atoms, and is coupled with one OH group randomly bonded to each of the three topmost P atoms with a 33% surface coverage.

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..

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