Electrophysical phenomena in the tribology of polymers

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Thermodynamic methods are essentially macroscopic by origin and nature.

They appear in the analysis of macroscopic engineering systems. They have been reliably validated in numerous macroscopic experiments and observations. Most probably there can be found areas that permit analysis of mechanochemical systems by means of relatively simple thermodynamic methods. From the purely thermodynamic point of view, the central problem of mechanochemistry is the exchange of energy between the long-range elastic energy and the short-range energy accumulated in individual bonds.

There is no clear theory which could be adapted to mechanochemistry, however the most recent approach [ 16 ] should be mentioned here. This model can be helpful in general dependences formulation, related to kinetics of mechanochemical reactions and to mechanical forces used for reactions activation. The general Eqn. On the other hand the positive effect of mechanical stress on catalyst efficiency confirms this hypothesis. However the reason of this effect can be mechanically eg. Rodriguez et al. They tested a new advanced method for dechlorination of 1,2,3-, 1,2,4-, and 1,3,5-trichlorobenzenes in organic solvent catalysed by palladium on carbon support and solid hydrazine hydrochloride yields benzene in short reaction times.

The catalyst system can be efficiently reused for several cycles. Ultrasound radiation of the heterogeneous catalyst reaction increases remarkably the rate of dechlorination. Moreover, Rodriguez found that there is optimum energy of ultrasound radiation which results maximum catalysts efficiency. This effect is not seen when ultrasound radiation act liquid reactants.

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Rodriguez results confirm thesis that energy, in this case of ultrasound radiation is useful in reaction rate increasing when solid body — particles of catalyst are present in reaction mixture. This energy is cumulated by catalyst and emitted to the space near catalyst surface, what is the reason of reaction rate increasing. This effect can not be explained by the changes of the structure of catalysts surface, like in other mechanochemical effects eg. The concept of mechanochemistry to modify molecular reactivity has a rich history for a long time.

For instance Kauzmann an Eyring as early as [ 18 ] suggested that the mechanical perturbation of diatomic molecules could alter the reaction coordinates combined with their homolytic dissociation. The chemical kinetic quantitatively describes homogenous reactions, where the rate of reaction depends only on heat introduced to reaction system.

Kinetic equations concern reagents concentration, and according to Arrhenius equation: temperature of reaction mixture as well as activation energy.

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These kinetic equations used in heterogeneous catalytic reactions description concern no one parameter characterizing catalyst. Consequently the effect of catalyst action can be explained only by the decreasing of activation energy value — the only one calculated parameter in kinetic equations.

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It is the reason that all theories of catalysts action try explain the mechanism of activation energy decreasing. This mechanism should be directly confirmed, particularly by materials engineering, which should explain:. Most recent work [ 19 ] emphasizes that while the detailed mechanisms by which different mechanochemical phenomena arise are not always well understood, mechanical forces are capable of effecting novel reactivity.

Additionally, it strengthens that using force, one can effectively shepherd a chemical reaction down specific reaction pathways, for instance by selectively lowering the energy of a transition state. At this point it is of note, that the field of polymer mechanochemistry, has also the potential to change this paradigm by revolutionizing the way chemists think about controlling chemical reactions [ 19 ]. In recent years the mechanochemistry field approach has found a renaissance, and different techniques have been applied to activate chemical reaction [ 20 - 22 ] and thereby to lower their activation energy.

This model was worked out on the basis of tribological tests results and was dedicated to tribochemistry. Due to the additional energy the reaction can reach a critical rate. The energy emitted from surface as pulses ranges 3—5 eV and can reach the value of activation energy E a and the triboreaction process starts to proceed or reaches the critical rate. This effect is due to addition portion of energy emitted by catalysts surface to the reaction space. At this point it should be emphasized that equation 19 describes both catalytic and tribocatalytic reactions.

This equation quantitatively characterizes all kinds of energy introduced into the reaction system, including mechanical energy and properties of catalyst, explained by energy emitted from its surface to reaction space. Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3. Help us write another book on this subject and reach those readers. Login to your personal dashboard for more detailed statistics on your publications. Edited by Hasim Pihtili. By Juan R. Laguna-Camacho, M.

Electronic Processes in Organic Crystals and Polymers

Vite-Torres, E. Edited by Chang-Hung Kuo.

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We are IntechOpen, the world's leading publisher of Open Access books. Built by scientists, for scientists. Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. Downloaded: Introduction Activation energy Ea is strictly combined with kinetics of chemical reactions. Background and the present work goal 2. In the investigations of bioactivity the elements of implants with NCD layer will be assessed by the allergy tests and adhesion of blood platelets. Metallic biomaterials with modified structure and specific mechanical features modulus of elasticity, shape-memory and hyperplasticity with surface layers of good mechanical and corrosion properties and biotolerance intended for making new generation implants for reconstruction and elastic osteosynthesis.

The aim of the task is to work out the technology of making new generation metallic biomaterials with surface layers intended for surgical implants for reconstruction and elastic osteosynthesis. Implants of perspective importance were selected for endoscopic operations stents for treatment of narrowing of blood vessels - artery and aorta, oesophagus, bronchi, trachea and urinary system made of FeCrNiMo alloys nad NiTi shape memory and hyperelastic alloys with passive - carbon layers and nails for intramedullar osteosynthesis made of FeCrNiMo and TiAlNb alloys with passive - carbon layers as well as fixators used for spine illness and injury made of TiAlNb or TiNbTaZr alloys of specific modulus of elasticity, with surface layers modified with elements such as O, C and N.

The project assumes stress and strain analyses for selected forms and geomeric features of implants realized with the use of computational mechanics methods due to describe optimal mechanical properties of a metallic biomaterial and surface layers. The selection of optimal structures and mechanical properties of the metallic biomaterial as well as physical and chemical properties of surface layers for specified functional forms of implants, their conditions of use and applied operation technique is a key problem both scientific and application in the suggested task.

Tests of biomaterials with surface layers as well as finished products which will be made by selected manufacturers will be carried out in "in vitro" conditions adequate to clinical ones. Furthermore, sterilization techniques of implants and criteria of quality assessment of applied biomaterials, surface layers and finished products taking UE directives into consideration will be worked out. Additionally, recommendations for the operation technique for these products will be also carried out.

New titanium-based biomaterials produced by surface engineering methods with the possibility of controlling their biocompatibility. Titanium and its alloys belong to the most prospective metallic biomaterials. Their distinguishing features are: - the highest resistance to biological corrosion, - relatively good mechanical properties accompanied by a low density - twice as low as that of austenitic steel and that of Co-Cr-Mo alloys. Just as is the case with the metallic biomaterials mentioned above, the use of titanium and its alloys is however limited by their low frictional wear resistance and by the possibility of the release of their constituents into the surrounding biological environment.

The investigations performed thus far indicate that the possibility of improving the biotolerance of and mechanical properties of biomaterials by modifying their chemical and phase composition has been exhausted. The other difficulties reported in the literature lie in achieving a good bond between the bone implant and the tissues that surround it, and, when moving artificial body parts and medical instruments are in question, in ensuring a low cell adhesion.

Now, the only way in which these problems can be solved is to develop new methods of materials engineering such that permit producing surface layers with a precisely specified microstructure, chemical and phase composition, surface topography, hardness and residual stress state, prevent the release of the material constituents into the surrounding tissues, and in addition are characterized by a good resistance to frictional wear and corrosion and, in consequence, by a good biocompatibility tailored according to a given destination of the biomaterial.

The basic goal of the project is to develop technologies that permit optimizing the properties of titanium alloys, both used at the present and those being in the stage of development, that are intended to be used for the fabrication of orthopedic implants, heart valves, backbone stabilizers, bone screws and plates and medical instruments, by employing new, even in the world-wide scale, methods of surface engineering, such as glow discharge assisted carbonitriding and nitriding combined with Pulsed Laser Deposition PLD , or with autocatalytic deposition of nickel-phosphorus coatings.

Another important advantage is that the layers can be produced on parts of sophisticated shapes. The research goals of the project will thus be concentrated on the fabrication of a new generation of titanium-based biomaterials that combine the good physical and mechanical properties of titanium and its alloys with the properties, advantageous for the biochemical behavior of the implant, of the surface layers with controlled biocompatibility and biofunctionality.

The project comprises a wide spectrum of research tasks, beginning from the development of the technology of the surface layers, through the examinations necessary to verify their biocompatibility, and ending with the preparation of the fundamental recommendations concerning the application of the layers. The technologies developed during the realization of the project can be applied for the fabrication of bone implants designed to operate in contact with blood or with soft tissues, and for the production of medical instruments.

Controlled modification of metallic surface layers with carbon ions.


Electrophysical phenomena in the tribology of polymers

The aim of the project was to develop the technology of deposition of thin carbon films which would fulfill special requirements as the layers on medical implants made of Ti6A14V alloy. Diamond is the most biocompatible material and because of this reason it was used in the project as the basic material, which properties investigated in earlier researches had shown its biocompatibility. In this project the RF PCVD method will be improved, the resources of control of biocompatibility of diamond will be extended and the protective interlayer against metalosis in case of incidental damages of diamond layer will be produced.

The improvement of RF PCVD method consist in application of complex process of deposition: RF PCVD and MW PCVD which should enable better rate of ionization of plasma without damage of control of autopotential and temperature of surface and increase of the area of uniform plasma composition which is important for phenomenon stability.

The second alternative of the improvement of RF PCVD method consist in utilization of ceramic film for controlled profiling of surface morphology from nano scale to micro scale. Microstructure and texture optimum parameters in respect to the biocompatibility and mechanical properties of titanium —based semi-roducts produced by deep-drawing with the final surface treatment. Interest in titanium and its alloys is connected with their good mechanical properties joined with the corrosion resistance and bio-compatibility which is the best among metallic materials.

The further increase of the bio-compatibility as well as mechanical properties could be obtained by application of the suitable final surface treatment.

Good ductility of titanium and its alloys, despite the hexagonal structure, makes possible fabrication of semi-products with complicated shapes by application of chosen technologies of plastic deformation. The goal of the project is to elaborate a method of fabrication of titanium-based semi-products with complicated shapes by application of mechanical and hydro-mechanical deep-drawing with subsequent surface treatment using glow discharge methods and laser technologies.

Beside the conventional method of deep-drawing, the hydro-mechanical process will be applied, too.

Polymers: A Property Database

This last method is recently used in the world to produce parts with complicated shapes. In this technological process, the material is being formed into hollow bodies with the aid of an additional fluid. The tension-pressure combination increases the plastifying properties of the material to be deep-drawn and allows the manufacture of complicated work-pieces from the metallic materials. Further increase of physical and chemical parameters of titanium and its alloys could be obtained by application of the respectively chosen modern technology of surface engineering.

It is planned to applied the following technologies: - glow discharge nitriding; fabrication of titanium nitride surface layer - pulsed laser deposition; producing coatings on the basis of nitrides, oxides and hydroxyapatite HA and diamont like carbon DLC. The research activity will be realised in the integrated net-work with co-operation of: - Institute of Metallurgy and Materials Science, Polish Academy of Science in Cracow; complex structural and properties diagnostic - Faculty of Non-Ferrous Metals, University of Mining and Metallurgy in Cracow; mechanical and hydro-mechanical deep drawing - Institute of Optoelectronic MUT in Warsaw; pulsed laser deposition - Faculty of Materials Science Warsaw University of Technology in Warsaw; glow discharge technologies.

Electrophysical phenomena in the tribology of polymers [1999]

Semi-products for application as element of hip-joint and dental implants are planned to be fabricated. Study on interaction of body fluids with artificial surfaces predicted for use in medical implant. The use of medical implants allows for improvement of health condition of people suffering from different diseases. It is important to reduce unfavourable reactions resulting from contact of body fluids with the surfaces.

It is generally accepted, that titanium and its alloys are the best tolerated materials which introduce the lowest amount of unfavourable changes in the body.

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Electrophysical phenomena in the tribology of polymers Electrophysical phenomena in the tribology of polymers
Electrophysical phenomena in the tribology of polymers Electrophysical phenomena in the tribology of polymers
Electrophysical phenomena in the tribology of polymers Electrophysical phenomena in the tribology of polymers
Electrophysical phenomena in the tribology of polymers Electrophysical phenomena in the tribology of polymers
Electrophysical phenomena in the tribology of polymers Electrophysical phenomena in the tribology of polymers
Electrophysical phenomena in the tribology of polymers Electrophysical phenomena in the tribology of polymers

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