Improvement of surface mechanical properties of polymers by helium ion implantation (original) (raw)
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Surface and Coatings Technology, 2004
Surface modification of ultra-high molecular weight polyethylene (UHMWPE) has been explored by using the non-line-of-sight plasma immersion ion implantation (PIII) technique. The polymer specimens, immersed in nitrogen plasma, were pulsed through a metallic grid at repetition rate of 100 Hz with negative high-voltage pulse of 15 kV magnitude and 10 As duration. The UHMWPE's structural changes induced by the PIII were analyzed by laser Raman spectroscopy (LRS) at 514.5 nm, X-ray photoelectron spectroscopy (XPS) and optical microscopy. From the Raman spectra it is observed that the chain structure of UHMWPE has been damaged due to ion bombardment and a layer of hydrogenated amorphous carbon is formed. The ratio of sp 3 /sp 2 bonded carbon in the modified layer was obtained by suitable fitting of the XPS C 1s energy peak, using a four-curve fitting procedure, which recognizes a portion of C -O and CMO surface bonding. The XPS results for N 1s peak show that the implanted nitrogen ions form chemical bonds with the polymer instead of forming precipitates by self-clustering. D
Brazilian Journal of Physics, 2004
Nitrogen Plasma Immersion Ion Implantation (PIII) has been used to modify the surface chemical structure of Ultra High Molecular Weight Polyethylene (UHMWPE). Grinding and polishing processes based on abrasive papers and alumina pastes have been evaluated with regard to their results on the improvement of polymer surface roughness, which has shown to be of crucial importance for hardness characterization. Raman spectroscopy, XPS, and Nanoindentation tests were used to characterize the modified surfaces. Experimental results has shown that UHMWPE surface mechanical properties such as hardness and elastic modulus can be improved by induced chain cross-linking between the macromolecules on the polymer surface caused by nitrogen PIII. The new material formed on the surface is Diamond Like Carbon (DLC). As a significant improvement in hardness was obtained by DLC synthesis on the treated surface, it is expected a dramatic improvement of abrasion resistance and overall durability of prostheses made with PIII treated UHMWPE.
2001
The structural and mechanical properties have been studied for ultra high molecular weight polyethylene UHMWPE q Ž q. 14 15 2 Ž. implanted by 80 keV N , 40 keV N with fluencies ranging from 1 = 10 to 5 = 10 ionsrcm. Elastic recoil detection ERD , 2 Ž. Raman spectroscopy and X-ray photoelectron spectroscopy XPS have been employed to study the structural change of UHMWPE before and after implantation. ERD results show that the high-energy edge of ERD spectra shifts to the lower energy with an increase in implantation fluence, indicating that a hydrogen deficient surface layer is formed after implantation. From Raman spectra it is observed that the chain structure of UHMWPE has been damaged due to ion implantation and when the fluence exceeds 1 = 10 15 ionsrcm 2 , a layer of hydrogenated amorphous carbon is formed. The XPS result shows that the injected nitrogen atoms form chemical bonds with the polymer instead of forming precipitates by self-clustering. The hardness and Young's modulus of the UHMWPE determined by nanoindenter increase with increased fluence. The hardness and Young's modulus of the UHMWPE implanted with the fluence of 5 = 10 15 ionsrcm 2 is four and two times higher than those of unimplanted UHMWPE, respectively.
Polimery, 2007
DARIUSZ M. BIELIÑSKI 1)2) *) , CZES£AW OELUSARCZYK 3) , JACEK JAGIELSKI 4)5) , PIOTR LIPIÑSKI 1) Modification of polyethylene by high energy ion or electron beam-structural, micromechanical and conductivity studies of the surface layer Summary-Commercial grade polyethylenes: high density (PE-HD) and ultra-high molecular weight one (PE-UHMW) were subjected to the surface modification by electron beam irradiation (0.6-1.5 MeV/50-500 kGy) and ion beam bombardment (He + 160 keV/2 •10 13-5 •10 16 ions/cm 2 ; Ar + 130 keV/1 •10 13-2 •10 16 ions/cm 2). Effects of modifications were studied by spherical nanoindentation and scratch hardness tests. Contrary to electron beam irradiation, the ion beam bombardment, especially of He + ions, can significantly increase (up to 3 times) hardness of the surface layer of polyethylene in comparison to the bulk. According to Grazing Incidence X-ray Diffraction (GIXRD) it is associated with an increased degree of crystallinity due to the surface modification. Nuclear Reaction Analysis (NRA) reveals a hydrogen release due to ion bombardment which saturates at the CH atomic composition. It cannot however be associated with cross-polymerization or crosslinking of macromolecules because of some unsaturations being present and a graphite formation. Partially graphitized and/or better organized modified macromolecular chains "rooted" in the polymer substrate explain low friction and wear resistance of ion bombarded polyethylenes. Even high stress crackings are not able to proceed with further delamination of the modified surface layer. Treatment of the material with heavy Ar + ions of energy 150-300 keV was combined with an electrical doping by implantation of polyethylene with I + ions of energy 150 keV. Apart an increase in hardness, the modification results additionally in a significant reduction of the surface resistivity (more than 20 times), facilitating a removal of static charge.
Surface & Coatings Technology, 2010
Generation of wear debris is the principal obstacle limiting the durability of ultra-high molecular weight polyethylene (UHMWPE) in biomedical applications. Aiming to enhance UHMWPE wear resistance, surface modification with swift heavy ion irradiation (SHI) appears as a potential and attractive methodology. Contrary to ion implantation techniques, the swift heavy ions range can reach tens to hundreds microns and its extremely high linear energy is able to induce effective chemical modifications using low fluence values. Nano-wear performance and surface mechanical properties of samples of pristine and SHI irradiated (using N 2 + ions at 33 MeV and a fluence of 1 × 10 12 ions/cm 2) were characterized by depth sensing indentation (DSI) and scanning probe microscopy (SPM). It turned out that modifications induced by irradiation at the surface layers were successful to reduce nano-wear volume and creep deformation. These improvements were related to beneficial changes in hardness, elastic modulus, hardness to elastic modulus ratio and friction coefficient.
Ion bombardment of polyethylene—influence of polymer structure
Vacuum, 2007
Polyethylenes of various macromolecular and supermolecular structures were studied from the point of view of their susceptibility to an ion beam treatment. An influence of molecular weight (M w ), molecular weight distribution (M w /M n ) and the degree of branching were compared within the set of low-density polyethylenes (LDPE) studied. An influence of the length of branches was compared between LDPE, linear low-density (LLDPE) and high-density (HDPE) polyethylenes. An influence of the degree of crystallinity and the morphology of a crystalline phase were compared for HDPE samples solidified under various thermal conditions and ultra-high molecular weight polyethylene (UHMWPE). Plate polymer targets $2 mm were bombarded with 100 keV He + or 130 keV Ar + ions (dose of 10 14 -10 16 ions/cm 2 ; ion energy stream density o0.1 mA/cm 2 ), micromechanical properties of their surface layer (hardness, mechanical modulus and elastic recovery) determined and compared to the virgin materials.
Effect of ion implantation on surface energy of ultrahigh molecular weight polyethylene
Journal of Applied Physics, 2003
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