XX is the XXth reference in the list of references. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. 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Venčeslav Kaučič, in, Reference Module in Materials Science and Materials Engineering. Skutterudites (SKUs), clathrates, and HH alloys are PGEC TE materials prepared mainly by solution casting or powder metallurgic synthetic processes. Table 9.1 summarizes the ZT values of high-performance inorganic TE materials together with the plausible mechanisms governing their TE performance. These alloys have three components selected from different element groups or from the same group. Progress in nanostructured HH materials has been summarized in Reference [111]. For example, any intrinsic modification to the composition of the polymer chain as a result of changing the sequence or distribution of the different domains, or extrinsic factors such as salt additions, that modifies the tendency of water molecules to take part in hydrophilic versus hydrophobic hydration will alter the clathrate structure and modify the Tt. or in a thesis or dissertation provided that the correct acknowledgement is given However, genetic engineering and the tailored molecular design of ELRs allow this possibility to be extended to other topologies and nanostructures that involving the directed self-assembly of ELRs [113,114] such as nanopores [115]. UC Davis chemists just discovered a whole new class of clathrates, potentially opening new ways to make and apply these materials. Clathrates compared to SKUs possess a more complex cage-like structure and a wider variation in composition. Center for Energy Materials, Department of Chemistry and iNANO, Aarhus University, Århus C, Denmark As-synthesized products are generally calcined in air or oxygen flow. Medical applications such as in magnetic resonance imaging. A similar procedure was later applied by the same group to obtain Na8Al8Si38 from NaSi and NaAlSi precursors [55], K4.2Na3.8Si46 from Na4Si4 and KCl precursors [56] and A8Na16Si136 from Na4Si4 and ACl (A = K, Rb, Cs) [57]. UC Davis chemists just Many zeolitic materials have been prepared in the form of colloidal suspensions with narrow particle size distributions.31 Silicalite-1 is the most frequently studied system. Thanks to these properties, DNACCs promised to provide a general platform for designing the self-assembly of colloidal crystals. On the other hand, Type I and Type II silicon clathrates (Si46 and Si136), which are composed with face-sharing Si20, Si24, and Si28 cages, have been synthesized via a number of processing routes. SKUs are bulk TE materials with the structure of (Co, Ni, Fe)(P, Sb, As)3 and cubic space group Im3. "Reproduced from" can be substituted with "Adapted from". with the reproduced material. More complex techniques can also be used to control the mutual interactions between colloidal particles via grafting of molecules on their surface. This property is based on a molecular transition of the polymer chain in the presence of water at a temperature above a certain value, known as the “inverse temperature transition” (ITT). it in a third party non-RSC publication you must The clathrates are low-thermal conductivity compounds with open frameworks composed of tetrahedrally coordinate Si, Ge, Al, Ga, or Sn. the type VIII clathrate33–35 and type IX clathrate.36 Because of specific structural features, compounds of the latter type are sometimes called chiral clathrates. 4 and figs. Thermoelectric clathrates hold significant promise for high temperature applications with zT values exceeding 1.3. In DNACCs, colloidal attraction arises due to the formation of intraparticle bridges formed from the hybridization of single-stranded DNA (ssDNA) with its complementary sequence (such hybridization leads to the famous double-helix structure), see Fig. Carbon dioxide entrapment in an organic molecular host. Other articles where Clathrate is discussed: bromine: Physical and chemical properties: …bromine water a hydrate (a clathrate) can be isolated that contains 172 water molecules and 20 cavities capable of accommodating the bromine molecules. The four cluster types can be arranged into three crystals, clathrates I, II, and IV, following literature classification (Fig. The Hartmann–Hahn condition was established by using sodium hexafluorosilicate, for which the relaxation time (3.2 s) is rather long for convenience, but no more suitable compound has been identified (Hoffner et al. A clathrate is a type of hydrate, or water compound, in which molecules of another substance are trapped within a cage-like structure composed of water molecules. In 2010, Yan et al. Physical Chemistry Chemical Physics 2016, 18 (15) , 10018-10027. In all cases the Ref. [31] reported the synthesis of the clathrate Na24Si126 from the Na4Si4 precursor. For the design of mesoporous materials from nanosized zeolitic species, the best results were obtained when the synthesis was carried out in two steps. Also, a DSC thermogram of a 50 mg/L aqueous solution of the same polymer is shown (heating rate 5°C/min). In our discussion, we will progress in order of decreasing complexity, starting from the more complex computational models to the simpler analytical theories. have studied the mechanical features of an ELR-based hydrogel whose lysine residues have been modified with activated alkyne and azide groups, that form a strong covalent bond without the presence of any catalyst, which finally bring to a stable platform possibly applicable in various biomedical applications [116]. In fact, almost 10 years passed since their inception before the first DNACC-based crystalline structure was reported [8–10]. In other words, clathrate hydrates are clathrate compounds in which the host molecule is water and the guest molecule is typically a gas or liquid. More recent literature describes a steam-assisted dry gel conversion techniques for the synthesis of TS-1,21 the preparation of microporous products from layered silicates and aluminophosphates with kanemite-type layered structure as precursors,22 the vapour-phase method for the preparation of large single crystals of the clathrate compound MTN (a zeolite-like material)23 or the TS-1 synthesis using mechanochemical reaction by grinding titanium and silica powders with a planetary ball mill and succeeding hydrothermal treatment.24 The majority of the syntheses of ordered mesoporous silica- and nonsilica-materials are based on the same principles, that is, the hydrothermal procedure using various structure-directing agents (surfactants), like cationic cetyltrimethylammonium hydroxide (synthesis of MCM-41) or nonionic block copolymers (synthesis of SBA-15).1,25 Precise adjustments of synthetic parameters, like silica source, temperature and the time of crystallisation or pH, crucially affect the properties of final products, for example, pore size or hydrothermal stability. The inorganic clathrates have been shown to be both chemically and thermally stable at high temperatures, and … University of California - Davis Clathrates Under certain conditions it is possible to create gas hydrate clathrates where the host is water and the trapped species is a gas such as methane, natural gas, or some refrigerant gases. The Si44− cluster lattice was oxidized and crystollographically rearranged close to the anode, and sodium was reduced and vaporized at the cathode. In addition, clathrates are highly chemically and thermally stable at high temperatures. A chemical substance consisting of a lattice of one type of molecule trapping and containing a second type of molecule. 1993). If you are not the author of this article and you wish to reproduce material from Hence, depending on the specific need, one would better resort to one or the other. One of the main reasons behind this problem lies in the physics of multivalent interactions, i.e., interactions mediated by the formation of multiple bonds, governing DNACCs. * If you are the author of this article you do not need to formally request permission Layer Type Some compounds, such as bentonite, can trap hydrocarbons, alcohols, and glycols between the layers of their lattices.20 Graphite can also intercalate compounds between its layers. A and X are transition metals, and B may be a metal or nonmetal. The strict control over the amino acid composition and sequence of the ELR structure is finally of great value not only because it permits a theoretically infinite fan of bioactivities and favors the thermo-responsive behavior of the recombinamer, but also because it opens up possibly to a whole array of crosslinking approaches, some of which will be mentioned in further examples. Fig. 1993). the whole article in a third party publication with the exception of reproduction In addition, smaller zeolite crystals have reduced diffusion path lengths relative to conventional micrometer-sized zeolites. ZT of SKUs can be significantly improved by double, triple, and multiple filling of elements into their structural vacancies. The ZT enhancement comes from a simultaneous increase in the Seebeck coefficient and a decrease in the thermal conductivity due to nanostructuring. With all these assets, it is not surprising that clathrates have been intensely investigated in the thermoelectric community during the past decade. Such a structure makes them “PGEC” materials. The magnitude of Tt also depends on several factors. (A) Schematic close-up image of two DNACCs forming a bond via the hybridization of DNA strands—the so-called sticky ends—grafted on them via a polymeric tether (colloid core: light blue spheres (gray in the print version ); tether: dark blue (dark gray in the print version)). For example: What will be the crystalline order of the assembled structure? {It should be noted that the distribution of semiconducting clathrates over the above structural types is essentially non-uniform. to reproduce figures, diagrams etc. Fetching data from CrossRef. The present perspective provides a review of the many studies concerned with the synthesis, crystal structure and thermoelectric properties of clathrates with emphasis on the type I clathrate. B. Iversen, Center for Energy Materials, Department of Chemistry and iNANO, Aarhus University, Århus C, Denmark, Instructions for using Copyright Clearance Center page. Proteins are useful building blocks for the formation of ordered nanostructures via self-assembly due to their well-understood folding, stability, and protein–protein interactions [112]. Synonyms for Clathrates in Free Thesaurus. Usually, temperatures in the range of 450–600 ° C are applied to remove the organic components, which is not critical for the stability of the majority of microporous zeolitic and also mesoporous compounds. This article is part of the themed collection: For reproduction of material from all other RSC journals and books: For reproduction of material from all other RSC journals. In this folded state, the polymer chains adopt a dynamic, regular, non-random structure, known as a β-spiral, which contains type II β-turns as the main secondary feature and is stabilized by intra-spiral, inter-turn and inter-spiral hydrophobic contacts [102]. In general, very dilute systems containing high amounts of tetraalkylammonium hydroxides are used in the synthesis of zeolite nanocrystals to avoid the aggregation of the particles. S8 to S10) . Turbidity profile as a function of temperature for poly(VPGVG) (5 mg/L) in water. Instructions for using Copyright Clearance Center page for details. This effect is a result of both the mean polarity of the polymer chain and the molecular architecture and distribution of the different amino-acid domains in the ELRs [109]. All these factors together with proper choice of silica source allow the stabilisation of starting clear solutions, where only discrete gel particles are present. Corresponding authors, a The trapped molecule is usually a gas at normal pressure and temperature. 1. What are synonyms for Clathrates? of the whole article in a thesis or dissertation. Clathrate hydrates, or gas hydrates, clathrates, hydrates, etc., are crystalline water-based solids physically resembling ice, in which small non-polar molecules or polar molecules with large hydrophobic moieties are trapped inside "cages" of hydrogen bonded, frozen water molecules. 1992). In 2011, CoSb3 with multiple fillers of Ba, La, and Yb were synthesized, and a high ZT of 1.7 at 850K was reported [107]. In the past this high yield, orthogonal and biocompatible reaction was initially questioned due to the necessity of applying copper as a catalyst for the alkyne–azide interaction. article provided that the correct acknowledgement is given with the reproduced material. (B) Different binding approaches in DNACCs: “direct” bonds via grafted complementary strands (top), “indirect” via free linkers in solution (center) or again direct but mediated by strands moving on the colloidal surface rather than fixed (bottom). 1. Their complex unit cells allow a significant reduction in the thermal conductivity and lead to a high ZT. The clathrates considered here are all found to be more stable than the elemental phases. The responsive behavior of ELRs has been defined as their ability to respond to external stimuli. It is thus the scope of this chapter to present their contribution to our understanding of DNACCs self-assembly. In the first step, zeolite seeds were prepared by the shortened hydrothermal treatment and then the second hydrothermal reaction was performed after adding surfactant, in order to direct the mesoporous phase.34 The preparation of mesoporous zeolitic single crystals involve partial dissolution of microporous solid, dealumination procedures, such as steaming, acid and alkaline treatments35 or a procedure, where mesoporous carbon matrix is impregnated with reaction mixture for zeolite ZSM-5 synthesis, and zeolite crystals are grown around the carbon particles.36 The removal of encapsulated carbon matrix by calcination leads to isolated large zeolitic crystals with uniform mesoporous system. However, DNACCs have proved very difficult to crystallize, as their assembly easily leads to amorphous structures rather than well-ordered ones. The inorganic clathrates have been shown to be both chemically and thermally stable at high temperatures, and high performance can be obtained from both single crystals and processed powders. It is indeed multivalency that makes them particularly sensitive to temperature, salinity, pH, and other environmental conditions. These alloys are relatively cheap and have a flexible composition. We use cookies to help provide and enhance our service and tailor content and ads. Carbon-based frameworks composed of sp3 bonding represent a class of extremely lightweight strong materials, but only diamond and a handful of other compounds exist despite numerous predictions. The inorganic clathrates have been shown to be both chemically and thermally stable at high temperatures, and high performance can be obtained from both single crystals and processed powders. The sublimation of Group V elements (e.g., antimony) and poor resistance to oxidation limit their wide application >600°C, as oxidation and volatilization take place in harsh environments such as in air at high temperatures leading to decreased lifetime of the respective TE generators. Information about reproducing material from RSC articles with different licences
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