Clathrate hydrates physical properties

In the last 30 years or so. clathrate science has blossomed. with the reports of many new guests, a new hydrate structural family, a complete revision of the stmcture-size relationships, new approaches for hydrate characterization. refined models for hydrate stability prediction, high-level calculations and computational work on hydrate physical properties, experimental work and models for kinetic processes, etc. 

Clathrate hydrates are inclusion compounds formed by the enclosure of a small guest molecule within a hydrogen bonded cage of solid-state water. Clathrate hydrates are co-crystals and are thus distinct from ice, which is made of pure water, and hence can have different physical properties to ice such as a different melting point. The classic example of a clathrate hydrate is the burning snowball of methane clathrate hydrate. The combustion of the methane in the clathrate is self-sustaining, Figure 7.1. Many... 

Air bubbles and clathrate hydrates in polar ice cores have attracted considerable interest because they provide the most direct record of past atmospheric gas compositions (e.g., Raynaud et However, the processes of air clathration in polar ice sheets should be taken into account when considering gas analyses. It is known that extreme fractionation of gases in air inclusions occurs when air bubbles change into clathrate hydrates by the diffusive mass transfer of air molecules between bubbles and hydrates. To estimate the effects of hydrate formation on the distribution of atmospheric gases in deep ice, it is essential to understand the structure and physical properties of natural air hydrates. 

This table gives measured phase equilibria data of si and sll gas clathrate hydrates (see Table I for gas hydrate structure and physical property data). The temperature and pressure conditions at which gas... 

A GAS HYDRATE, also known as a gas clathrate, is a gas-bearing, icelike material. It occurs in abundance in marine sediments and stores immense amounts of methane, with major implications for future energy resources and global climate change. Furthermore, gas hydrate controls some of the physical properties of sedimentary deposits and thereby influences seafloor stability. 

A remarkable variation of the type-I clathrate superstructure is associated with the formation of semiclathrates in the Ge-P-Q (Q = Se, Te) systems [34, 35]. The term semiclathrate was first introduced for hydrates of quaternary ammonium salts, which show general structural and physical properties of normal clathrates but in addition feature a single hydrogen bond between host and guest substructures [50]. Up to now quite a number of semiclathrates-hydrates have been reported in the literature [51] compared to a very limited number of inorganic semiclathrates, which are exclusively cationic semiclathrates. 

CO2 hydrate is perhaps one of the best understood clathrate hydrate regarding structural, thermodynamic, as well as other physical properties. Figure 7(a) and (b) show the CO2 molecules with full symmetry in small and large cages in cubic structure I analyzed by the Rietveld refinement with the direct-space technique. In the large cage, the best... 

Since the outstanding physical property of clathrate hydrates is the efficient storage of gases, interest continues in applications where this property will be of use. Typically, a volume of gas hydrate can hold 160 volumes of gas at STP, thus, gas storage, especially energy gases such as methane and hydrogen, continues to be actively pursued. 

Salts, and more recently co-crystals, have attracted much interest in the pharmaceutical industry for their promise in tailoring the physical properties of an active pharmaceutical ingredient (API) to meet the needs of the drug product and ultimately the patient.Salt forms, produced by add (A)-base (B) reactions in the solid state, are multi-component solids comprising minimally an A B pair they may be crystalline or amorphous. The term co-crystal, on the other hand, refers specifically to crystalline molecular complexes, which may include an A B pair among the different components and by definition necessarily include solvates (hydrates), inclusion compounds, clathrates and solid solutions. 

SOME PHYSICAL AND THERMOPHYSTCAL PROPERTIES OF CLATHRATE HYDRATES... 

Uchida T (1998) Physical property measurements on CO2 clathrate hydrates. Review of crystallography, hydration number, and mechanical properties. Waste Manag 17(5) 343-352... 

Physical constants, fundamental, 1-1 to 11 Physical properties amino acids, 7-1 to 2 gas clathrate hydrates, 6-136 to 140 inorganic compounds, 4-43 to 101 minerals, 4-149 to 155 oils and fats, 7-9 to 13 organic compounds, 3-1 to 523 semiconductors, 12-78 to 90 solvents, 15-13 to 22... 

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