Materials Synthesis

1987 ◽  
Vol 98 ◽  
Author(s):  
Peter R. Strutt ◽  
Julian P. Partridge

ABSTRACTInteresting possibilities exist for the scientific design of materials with optimized properties for a diversity of technological applications. For example, the reduction of severe wear and erosion in critical turbine and engine components requires basic studies of intrinsic strengthening, where loads are uniformly transferred across interphase inter-faces. The acheivement of this requires a developed capability for producing selected morphologies on the (i) macro, (ii) micro, and (iii) nanoscale. This involves using a combination of techniques that include the deposition of one, or more, atomic or molecular species in gaseous environments. Recent discoveries suggest, in fact, that it is feasible to design layers where the chemistry and structure at any depth can be pre-selected. Such a capability offers exciting opportunities for forming ‘graded property’ materials, as required in mechanical component and fiber-optic applications. Here, specific radial distributions of chemical species can be used to achieve optimal properties. Another in-triguing possibility is the formation of composite-structure materials, even on the nanoscale, by simultaneous growth of filaments and matrix, using appropriate precur-sors. Thus, metal and polymer matrices may, in principle, be strengthened by various types of fiber and particle distributions. In this approach the basic concept is the syn-thesis of scientifically designed materials for specific technological applications.

2017 ◽  
Vol 29 (5) ◽  
pp. 896-904 ◽  
Author(s):  
Duo Yi ◽  
Min Zhang ◽  
Lijuan Gu ◽  
Jianming Yang ◽  
Wenhui Yu

This study aims to evaluate the thermomechanical behavior of a new composite structure using finite element method. The composite structure consists of the substrate and the thermal spray coating with embedded fiber optic. The temperature evolution of the composite estimated by the finite element model shows good agreement with the experimental recording, which confirms the justifiability of model initialization, and then, the thermal results are applied for the following mechanical analysis. The stress distribution and the variation in refractive index of the embedded fiber are investigated. The results show that the stress level suffered by the embedded fiber is much lower than the yield strength, and the variation in refractive index of the embedded fiber has an insignificant effect on optical transmission, which ensures a good embedding quality of the fiber optic.


2020 ◽  
Vol 31 (16) ◽  
pp. 1950-1958
Author(s):  
Duo Yi

The optical fiber smart composite structures have been widely applied for the structural health monitoring, and the packaging technique of integrating optical fiber sensor with host structure is one of the key issues. The flame spraying coating provides strong adhesive strength with good heat resistance, which is particularly suitable for the packaging applications in harsh environments. However, the elaboration process of flame spraying coating–based fiber composite structure faces great challenges due to the flame spraying mechanisms. This study evaluates numerically an overall effect of flame spraying coating formation process on the structural and the optical properties of the embedded fiber optic based on a three-dimensional finite element model. First, the lumped capacitance method is used; both the average heat flux density in the whole spraying process and the specific heat flux density of each torch sweep are estimated to initialize the thermo-mechanical modeling. Then, the stress distributions in both radial and axial directions of the embedded fiber are discussed separately. Next, the variation of refractive index of the embedded fiber optic due to the residual strain is also investigated. Finally, the elaboration parameters including torch displacement and velocity are evaluated and optimized. The simulation results show that the embedded fiber optic maintains good structural and optical properties with the presented elaboration conditions, and therefore its transmission and sensing performance can be ensured.


2020 ◽  
pp. 225-240
Author(s):  
Guillermo Restrepo

A chemical element, treated as a concept, entails objects and attributes. From the eighteenth century to date, objects include substances up to quasi-molecular species and nuclides. Attributes range from non-decomposability up to lifetimes of 10-14 seconds. By analyzing the historical changes of the concept, we found the central role “chemical reaction” has played. However, historical changes of objects and attributes of the concept of chemical element lead to expand chemical reactions to the more general “chemical relations,” which contain traditional chemical reactions and any kind of relation between chemical species. In such a setting, a general structure for the concept of chemical element is presented that entails chemical species as objects and detected chemical relations and experimental measurement of atomic number as attributes.


Author(s):  
Elena Khomenko

Multi-fluid magnetohydrodynamics is an extension of classical magnetohydrodynamics that allows a simplified treatment plasmas with complex chemical mixtures. The types of plasma susceptible to multi-fluid effects are those containing particles with properties significantly different from those of the rest of the plasma in either mass, or electric charge, such as neutral particles, molecules, or dust grains. In astrophysics, multi-fluid magnetohydrodynamics is relevant for planetary ionospheres and magnetospheres, the interstellar medium, and the formation of stars and planets, as well as in the atmospheres of cool stars such as the Sun. Traditionally, magnetohydrodynamics has been a classical approximation in many astrophysical and physical applications. Magnetohydrodynamics works well in dense plasmas where the typical plasma scales (e.g., cyclotron frequencies, Larmor radius) are significantly smaller than the scales of the processes under study. Nevertheless, when plasma components are not well coupled by collisions it is necessary to replace single-fluid magnetohydrodynamics by multi-fluid theory. The present article provides a description of environments in which a multi-fluid treatment is necessary and describes modifications to the magnetohydrodynamic equations that are necessary to treat non-ideal plasmas. It also summarizes the physical consequences of major multi-fluid non-ideal magnetohydrodynamic effects including ambipolar diffusion, the Hall effect, the battery effect, and other intrinsically multi-fluid effects. Multi-fluid theory is an intermediate step between magnetohydrodynamics dealing with the collective behaviour of an ensemble of particles, and a kinetic approach where the statistics of particle distributions are studied. The main assumption of multi-fluid theory is that each individual ensemble of particles behaves like a fluid, interacting via collisions with other particle ensembles, such as those belonging to different chemical species or ionization states. Collisional interaction creates a relative macroscopic motion between different plasma components, which, on larger scales, results in the non-ideal behaviour of such plasmas. The non-ideal effects discussed here manifest themselves in plasmas at relatively low temperatures and low densities.


2019 ◽  
pp. 24-29 ◽  
Author(s):  
M. Yu. Fedotov ◽  
O. N. Budadin ◽  
S. O. Kozel’skaya

The results of research on the formation of the system of built-in non-destructive testing of linings of composite three-layer structures by an optical method using fiber-optic sensors based on fiber Bragg gratings are presented. The features of creating an input/output zone for fiber-optic sensors as applied to three-layer composite structures are studied. Recommendations for ensuring the integrity and optimal functioning of the fiber-optic monitoring system as applied to a real three-layer composite structure are formulated. The following is shown. The process of creating an integrated control system of three-layer composite structures by an optical method using integrated fiber-optic sensors includes a number of operations to form a topology and to ensure the output of fiber-optic sensors from composite claddings in a single technological cycle of manufacturing the structure according to the standard technological process without significantly adjusting it, which is extremely important in relation to serial technologies. When developing the technology of integrating fiber-optic sensors into a three-layer composite structure, it was experimentally shown that from the point of view of survivability and preservation of the efficiency of the embedded control system, it is necessary to fulfill a number of requirements for the placement and output of fiber-optic sensors taking into account the characteristics of manufacturing, machining, and operation designs. Thus, it is advisable to place fiber optic sensors in the casings at least 5 mm from the intended edge of the structure, at least 2 layers from the outer surface of the structure and not less than 5 layers from the honeycomb core. The fiber bend radius should be at least 30 mm to prevent mechanical burst and sharp bending of the signal when it is bending. Fiber optic sensors are recommended to be placed between layers with a reinforcement scheme in the direction of the fiber optic sensor, however placement is also allowed between the fiber sensors and one layer with a different direction of reinforcement, while in order to prevent fractures, computation fiber optic sensors overlap is unacceptable, thus, between crossover fiber-optic sensors must be at least 2 layers of prepreg.


1984 ◽  
Vol 4 (1) ◽  
pp. 155-156
Author(s):  
Taichin MORITA ◽  
Hiroshi SAITOH ◽  
Hozue YAMAGUCHI ◽  
Masaki NISHIMURA ◽  
Ryuzaburo TANINO ◽  
...  
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2018 ◽  
pp. 49-59 ◽  
Author(s):  
A.E. Raskutin ◽  
◽  
V.V. Makhsidov ◽  
O.I. Smirnov ◽  
L.A. Kasharina ◽  
...  

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