Layered solids

It has been also shown that when a thin polymer film is directly coated onto a substrate with a low modulus ( < 10 MPa), if the contact radius to layer thickness ratio is large (afh> 20), the surface layer will make a negligible contribution to the stiffness of the system and the layered solid system acts as a homogeneous half-space of substrate material while the surface and interfacial properties are governed by those of the layer [32,33]. The extension of the JKR theory to such layered bodies has two important implications. Firstly, hard and opaque materials can be coated on soft and clear substrates which deform more readily by small surface forces. Secondly, viscoelastic materials can be coated on soft elastic substrates, thereby reducing their time-dependent effects. 

SFA measurements on mica. Horn et al. [68] studied the deformation of mica surfaces in contact. In these studies, Horn et al. established the applicability of Hertz theory of contact mechanics to non-adhering layered solids by measuring... 

Consider a thin layer solid bowl centrifuge as shown in Figure 4.20. In this device, particles are flung to the wall of the vessel by centrifugal force while liquor either remains stationary in batch operation or overflows a weir in continuous operation. Separation of solid from liquid will be a function of several quantities including particle and fluid densities, particle size, flowrate of slurry, and machine size and design (speed, diameter, separation distance, etc.). A relationship between them can be derived using the transport equations that were derived in Chapter 3, as follows. 

By examining the dispersion properties of surface acoustic waves, the layer thickness and mechanical properties of layered solids can be obtained using the SAM. It can be used to analyze the wear damage progress [104], and detect the defects of thermally sprayed coatings [105]. 

By examining the dispersion properties of surface acoustic waves, the layer thickness and mechanical properties of layered solids can be obtained using the SAM. 

This highhght examines several new hybrid layered structures in the hetero-metallic perrhenate and vanadate families, whereby the late transition-metals are incorporated and their roles probed in the structures of layered solids. From these two families, new structural principles have emerged that not only help us understand key stractural features and correcdy forecast new compositions, but equally, have yielded many surprises (chirality, reduced phases) that show some of the most exciting chemistry is still waiting to be discovered or even imagined ... 

Freshly cast lead has a bright, silvery appearance. On exposure to the atmosphere, however, lead in the surface layer combines with atmospheric oxygen and carbon dioxide to form a dark, stable gray coating of mixed lead oxide and basic lead carbonate. This layer usually protects the metal from further oxidation and corrosion (see Fig. 38). Protected by a weathered surface layer, solid lead is stable to further corrosion. Lead is also very ductile and soft, being the softest metal known in antiquity. It is mainly because of these properties that lead was widely used for building, to make pipes and roofs, and in naval construction, for example. Solid lead flows, albeit very... 

A number of matrices have also been used for the preparation of semiconductor nanoparticles, whereby the particulate material is grown within and subsequently fills the cavities of the host material. These includes zeolites,361 glasses,362 and molecular sieves,363-365 and can be viewed as nanochambers which limit the size to which crystallites can grow. Other synthetic methods include micelles/microemulsions,366-369 sol-gels,370,371 polymers,372-377 and layered solids.378... 

The assembly of biopolymers with inorganic layered solids can lead to bionanocomposites in which the biopolymer becomes intercalated between the layers of the inorganic hosts [3]. The intercalation is a complex process that may simultaneously involve several mechanisms. Thus, in addition to hydrogen bonding, it has been invoked that certain biopolymers interact with the inorganic layers through... 

Ruiz-Hitzky, E., Dardar, M. and Aranda, P. (2005) Functional biopolymer nanocomposites based on layered solids. Journal of Materials Chemistry, 15,... 

The conductivity ofthe film was calculated for 30 monolayers. The film was deposited onto a Ag microelectrode array with a 1-mm distance between fingers. The thickness ofthe monolayer was taken to be 2 x 10"7 cm. For an air humidity value of 60% the conductivity equals 1.3 x 10"6 (Q/cm)-1 The current through the film has an ionic character, and there is apparently layered solid electrolyte... 

Burggraaf, A. J., K. Keizer and B. A. van Hassel. 1989b. Ceramic nanostructure materials, membranes and composite layers. Solid State Ionics 32/33 (Part 2) 771-82. 

Intercalation in layered solids is a long-established phenomenon. It has been suggested [ 1 ] that the first example, dating from over two thousand years ago, involved intercalation in kaolinite (an aluminosilicate clay) and explains the secret behind the production of fine Chinese porcelain, hi modern times, many thousands of papers have been devoted to intercalation chemistry in clays, graphite and other materials. 

Jones W, Chibwe M (1990) In Mitchell IV (ed) Pillared layered solids. Elsevier, Amsterdam, p 67... 

A large fraction of the material science research, and an important chapter of solid state physics are concerned with interfaces between solids, or between a solid and a two dimensional layer. Solid state electronics is based on metal-semiconductor and insulator-semiconductor junctions, but the recent developments bring the interface problem to an even bigger importance since band gap engineering is based on the stacking of quasi two dimensional semiconductor layers (quantum wells, one dimensional channels for charge transport). 

Fig. 10. Fourier transform of Pt Lj-edge SEXAFS data for 0.8 ML Pt/Si(l 11)7x7 (dots) and of the simulated EXAFS for a Pt atom in the sixfold interstitial site within the top Si(lll) double layer (solid line). The derived chemisorption model is represented in the insets. The first neighbour distance is Pt—Si = 2.48 + 0.03 A, and the Pt coordination number is 6 + 1 Si neighbours. The distances beyond the first neighbour peak are fitted up to the fifth Pt—Si distance, and indicate the deformation of the Si cage, as indicated in the modot, due to the presence of the host Pt atom...

Several synthetic methods for the preparation of semiconductor nanoparticles have been reported. Colloidal and organometallic routes have probably been identified as the two major methods in use [11-16], although nano dimensional particles have been also synthesized in confined matrices such as zeolites [17], layered solids [18], molecular sieves [19,20], vesicles/micelles [21,22], gels [23,24], and polymers [25]. An ideal synthetic route should produce nanoparticles which are pure, crystalline, reasonably monodisperse and have a surface which is independently derivatized. 

Fig. 3.5.7 Absorbance (corrected for ArH and the quartz substrate) of 10-layer (solid line), 20-layer (dashed line), 30-layer (triangles) and 40-layer (squares) HgAr films exposed to H2S for 15 min. Inset Absorbance of HgS in ArH (corrected for ArH and quartz) as a function of layer number at 350, 400, 500, 600, and 700 nm. (From Ref. 45.)...

Many layered solids form intercalation compounds, where a neutral molecule is inserted between weakly bonded layers. For example when potassium vapour reacts with graphite above the melting temperature of potassium (337 K), it forms a golden compound KCs in which the potassium ions sit between the graphite layers, and the inter-layer spacing is increased by 200 pm (Figure 3.16). Addition of a small amount of KO2 to the molten potassium results in the formation of a double layer of potassium atoms between the graphite layers and a formula close to KC4. 

Intercalation of polyaniline between MoS2 layers produced nanoscale molecular composites with unusual charge transport properties [119]. Recent advances in the preparation, characterization, and utilization of conducting polymers intercalated into layered solids were surveyed [120],... 

Removal of the carboxyl group from a BS molecule leaves heneicosane (C21) which exhibits no liquid-crystalline phase, but does form two layered solid phases in which the C21 molecules are fully extended with the molecular axes normal to the layer planes [320]. In the higher temperature solid (Phase II), the molecules are hexagonally packed within and execute hindered rotations about their long axis. In the lower temperature solid (Phase I), the rotational motions are damped and the molecules are orthorhombically packed within a layer. Gauche defects in the preferred al -transoid conformations occur more frequently near layer ends than near the middle of layers... 

The term solid-wall or monobloc vessel is applied to all components where the cylindrical wall consists of a single layer. Solid-wall vessels are suitable for all types of pressure vessels, in particular for those operated under high temperatures. Thermal stresses arising during heating or cooling are smaller than in multilayer vessels because of the good thermal conduction across the wall. Therefore solid-wall vessels are especially suitable for batchwise operation. 

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