Silica water series#
Silica water free#

While the impact of confinement on the coordination number has been studied for some cases, not always is surface-bonded water quantitatively included in the considerations, nor has there been extensive research of the coordination number for varying hydrophobicity and pore sizes. Some theoretical studies regarding the existence of supercooled bulk water in confined geometries have been carried out, and the fragile-to-strong transition of supercooled water has been studied in confined systems.

H (109.7°) because the water molecule is not surrounded by a sufficient number of neighbors, as compared to bulk liquid water or ice.

In a mesopore environment, such confinement can lead to significant changes in the coordination number, in the distance between nearest-neighbor water molecules, and in the angles of H O H (106.8°, I h) and H O As mentioned above, the bulk properties of water are dominated by the intermolecular hydrogen bonds between adjacent molecules deviations from bulk behavior occur when these interactions are disturbed, for example, by restriction in confined space. In this context, the term ‘liquid’ refers to water molecules that are closely related to bulk water. 3230 cm −1, overlapping with the band of ‘liquid’ water (ca. Ice-like water is marked by a characteristic vibration mode at ca. It refers to strongly hydrogen-bonded tetrahedrally coordinated water molecules, as can be characterized by infrared (IR) spectroscopy. When water molecules assemble in a structure more ordered than liquid water but not entirely crystalline, the term ‘ice-like’ water is frequently used. We speak of an ice structure if a high degree of order, that is, crystal structure, can be achieved. The dynamics can explain the differences in liquid water compared to the ordered hexagonal structure in I h ice. In the liquid state, water exhibits a coordination number of 4.4, while in the most common ice phase ( I h hexagonal space group P6 3 cm) it is reduced to precisely 4. Nevertheless, the sheer amount of hydrogen bonds creates a dominant influence on the behavior of water. Such hydrogen bonds in water exhibit dissociation energies of 12.5–20.9 kJ mol −1, which lies between the weaker van der Waals forces and the stronger covalent/ionic bonds.

Silica water free#

In water molecules, the difference in electronegativity between hydrogen and oxygen, as well as the free electron pairs in the latter, lead to electrostatic attraction between adjacent molecules. For this purpose, the structure of water is analyzed by pairing densities, coordination, and angular distributions with a novel adaptation of surface-specific sum-frequency generation calculation for pore environments. Furthermore, the water's structure is studied theoretically to gain deeper insight into the interfacial interactions. Those results are combined with IR spectroscopy to investigate pore wall-to-water interactions leading to different structures of water in the mesopore. The mesopore surface is characterized by N 2 and H 2O sorption experiments. The surface polarity of mesoporous silica (SiO 2) is modified by functionalization with trimethylsilyl moieties, resulting in a change from a hydrophilic (pristine) to a hydrophobic pore wall. In this work, this is studied both experimentally and theoretically. In addition to the pore size, the behavior is also strongly affected by the strength of the pore wall-to-water interactions, that is, the pore wall polarity. This leads to a different behavior regarding the molecular orientational freedom (‘structure of water') compared to the bulk liquid state. Utilizing powerful electronics, advanced features such as automatic calibration, continuous sample analysis and programmable multi-stream switching ensure accurate measurement of silica.In the spatial confinement of cylindrical mesopores with diameters of a few nanometers, water molecules experience restrictions in hydrogen bonding.

Silica water series#

Many years of experience and innovation in the design and successful application of continuous chemical analyzers has been combined with the latest electronics and production technologies to produce the Navigator 600 Series of analyzers from ABB.īased on colorimetric techniques, they feature a liquid handling section carefully designed to reduce routine maintenance.