Surfaces with Improved Mechanical Properties

Austenitic stainless steel, titanium and its alloys, zirconium and Cr—Co alloys are found to be the metallic materials of choice for joint prostheses. The first two materials 

Superhard coatings are of special interest in this regard. They can roughly be classified in four groups  

Typically, not only a high surface hardness is desired, but also a lower coefficient of friction, which among other factors affects the temperature in the friction zone. Examples include surgical tools, where high temperatures in the bone tissue must be avoided to minimize bone necrosisThe lowering of the friction of biomaterials is also of interest in many other medical devices, such as catheters, needles, stents, joint prostheses. 

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Surfaces with improved mechanical properties Joint prostheses... 

A number of studies on CNT-polymer composites have focused on improving the dispersion and load transfer efficiency in other words the compatibility between the CNTs and polymer matrix through covalent chemical functionalization of CNT surface (12,40). Many of the studies reported above have used acid-functionalized CNTs to fabricate MWCNT-PMMA composites with improved mechanical properties using different processing methods (24,25,27,62). Yang et. al (68) modified the acid functionalized CNTs with octadecylam-ine (ODA) to obtain ODA-functionalized CNTs. These CNTs were reinforced in a copolymer P(MMA-co-EMA) to form composites with improved dispersion and mechanical properties. 

The previous three sections involved the treatment of natural fibres by removing substances from the natural fibres. This section, however, describes a new modification that does not involve the removal but the addition of new material onto the surface of natural fibres. This type of modification involves the deposition of nanosized cellulosic materials onto the surface of natural fibres to enhance the interfacial adhesion between the fibres and the matrix [9,10,14,104]. By doing so, a hierarchical structure can be created. These works were inspired by nature. Nature maximises the efficiency of structural materials by creating hierarchical stmctures the arrangement of the constituents at every level, from the molecular level to the macroscopic level. By applying this concept, composites that possess a hierarchical structure with improved mechanical properties can be manufactured. 

Ganter, M., Gronski, W., Semke, H., Zilg, T., Thomann, R., MiiUiaupt R. Surface-compatibilized layered silicates—A novel class of nanofillers for mbbers with improved mechanical properties. Kautsch. Gununi Kunstst 54(4), 166-171 (2001)... 

In the new polymerization lling technique (PFT), Ziegler-Natta catalyst is attached onto the surface of an inorganic ller, so that ole n can be polymerized from the Her surface, thus allowing a very high ller loading to be reached in composites with improved mechanical properties... 

M. Ganter, W. Gronski, H. Semke, T. Zilg, C. Thomann, R. Mlilhaupt (2001) Surface compatibilized layered silicates a novel approach of nanofillers for rubbers with improved mechanical properties, Kautschuk, Gummi, Kunststoffe 54, 166. 

Numerous avenues to produce these materials have been explored (128—138). The synthesis of two new fluorinated bicycHc monomers and the use of these monomers to prepare fluorinated epoxies with improved physical properties and a reduced surface energy have been reported (139,140). The monomers have been polymerized with the diglycidyl ether of bisphenol A, and the thermal and mechanical properties of the resin have been characterized. The resulting polymer was stable up to 380°C (10% weight loss by tga). 

Modification of the membranes affects the properties. Cross-linking improves mechanical properties and chemical resistivity. Fixed-charge membranes are formed by incorporating polyelectrolytes into polymer solution and cross-linking after the membrane is precipitated (6), or by substituting ionic species onto the polymer chain (eg, sulfonation). Polymer grafting alters surface properties (7). Enzymes are added to react with permeable species (8—11) and reduce fouling (12,13). 

In a nutshell, the performance of weapons and munitions increases with the use of nanosized particles because of the increased surface area and enhanced heat transfer resulting in reduced ignition delay, burn time, improved mechanical properties and high density-specific impulse. Further, formulations based on micron-sized materials with a wide distribution suffer from defects such as slow energy release, incomplete combustion and inability to support rapid combustion which can be overcome with the use of nanoparticles or nanomaterials [102]. 

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