In situ materials

In part II of the present report the nature and molecular characteristics of asphaltene and wax deposits from petroleum crudes are discussed. The field experiences with asphaltene and wax deposition and their related problems are discussed in part III. In order to predict the phenomena of asphaltene deposition one has to consider the use of the molecular thermodynamics of fluid phase equilibria and the theory of colloidal suspensions. In part IV of this report predictive approaches of the behavior of reservoir fluids and asphaltene depositions are reviewed from a fundamental point of view. This includes correlation and prediction of the effects of temperature, pressure, composition and flow characteristics of the miscible gas and crude on (i) Onset of asphaltene deposition (ii) Mechanism of asphaltene flocculation. The in situ precipitation and flocculation of asphaltene is expected to be quite different from the controlled laboratory experiments. This is primarily due to the multiphase flow through the reservoir porous media, streaming potential effects in pipes and conduits, and the interactions of the precipitates and the other in situ material presnet. In part V of the present report the conclusions are stated and the requirements for the development of successful predictive models for the asphaltene deposition and flocculation are discussed. 

PVD reactors may use a solid, liquid, or vapor raw material in a variety of source configurations. The energy required to evaporate liquid or solid sources can be supplied in various ways. Resistive heating is common, induction heating of the source bottle is sometimes used, and electron beams are also employed. Molecular-beam-epitaxy (MBE) systems are PVD-type reactors that operate at ultrahigh vacuum. Very low growth rates are used ( 1 xm/h), and considerable attention is devoted to in situ material characterization to obtain high-purity epitaxial layers (2). 

It is possible to reduce the percentage of fines by means of overflow onboard trailing suction hopper dredgers. This, however, may not always be feasible because of environmental restrictions. Cutter suction dredgers do not have the possibility to make use of overflow. Fill pumped into the reclamation area then consists of the in-situ material as encountered within the borrow area. 

Therefore, the design of a grout requires sufficient knowledge on the construction type of masonry, on its state, on the in situ materials, and on the aim of the intervention, all these combined with knowledge on material science. 

If, for example, the property of the in-situ material lies at the spot inbetween the bounds as shown in fig. 4... 

Two types of materials are studied in the CIAPES programme ferritic steel and stainless steel. A database for vessels monitored by acoustic emission has been builded to collect the results of all the tests carried out in laboratory and in situ. 

One more application area is composite materials where one wants to investigate the 3D structure and/or reaction to external influences. Fig.3a shows a shadow image of a block of composite material. It consists of an epoxy matrix with glass fibers. The reconstructed cross-sections, shown in Fig.3b, clearly show the fiber displacement inside the matrix. The sample can be loaded in situ to investigate the reaction of matrix and fibers to external strain. Also absorption and transmission by liquids can be visualized directly in three-dimensions. This method has been applied to the study of oil absorption in plastic granules and water collection inside artificial plant grounds. 

Certain materials, most notably semiconductors, can be mechanically cleaved along a low-mdex crystal plane in situ in a UFIV chamber to produce an ordered surface without contamination. This is done using a sharp blade to slice tire sample along its preferred cleavage direction. For example. Si cleaves along the (111) plane, while III-V semiconductors cleave along the (110) plane. Note that the atomic structure of a cleaved surface is not necessarily the same as that of the same crystal face following treatment by IBA. 

Yoo C S, Akella J and Nicol M 1996 Chemistry at high pressures and temperatures in-situ synthesis and characterization of p-SijN by DAC x-ray/laser-heating studies Advanced Materials 96 ed M Akaishi et al (Tsukuba National Institute for Research in Inorganic Materials) p 175... 

Characterization of zeolites is primarily carried out to assess tire quality of materials obtained from syntliesis and postsyntlietic modifications. Secondly, it facilitates tire understanding of tire relation between physical and chemical properties of zeolites and tlieir behaviour in certain applications. For tliis task, especially, in situ characterization metliods have become increasingly more important, tliat is, techniques which probe tire zeolite under actual process conditions. 

Unlike melting and the solid-solid phase transitions discussed in the next section, these phase changes are not reversible processes they occur because the crystal stmcture of the nanocrystal is metastable. For example, titania made in the nanophase always adopts the anatase stmcture. At higher temperatures the material spontaneously transfonns to the mtile bulk stable phase [211, 212 and 213]. The role of grain size in these metastable-stable transitions is not well established the issue is complicated by the fact that the transition is accompanied by grain growth which clouds the inteiyDretation of size-dependent data [214, 215 and 216]. In situ TEM studies, however, indicate that the surface chemistry of the nanocrystals play a cmcial role in the transition temperatures [217, 218]. 

Two approaches have been taken to produce metal-matrix composites (qv) incorporation of fibers into a matrix by mechanical means and in situ preparation of a two-phase fibrous or lamellar material by controlled solidification or heat treatment. The principles of strengthening for alloys prepared by the former technique are well estabUshed (24), primarily because yielding and even fracture of these materials occurs while the reinforcing phase is elastically deformed. Under these conditions both strength and modulus increase linearly with volume fraction of reinforcement. However, the deformation of in situ, ie, eutectic, eutectoid, peritectic, or peritectoid, composites usually involves some plastic deformation of the reinforcing phase, and this presents many complexities in analysis and prediction of properties. 

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