Polyetheretherketone (PEEK) is considered as a substitute for metallic implant materials due to its extremely low elastic modulus (3-4 GPa). Despite its good mechanical properties, PEEK exhibits a slow integration with the bone tissue due to its relatively inert surface and low biocompatibility. We introduced a dual modification method, which combines the laser and plasma surface treatments to achieve hierarchically patterned PEEK surfaces. While the plasma treatment leads to nanotopography, the laser treatment induces microstructures over the PEEK surface. On the other hand, plasma and laser treatments induce inhomogeneity in the surface chemistry in addition to the tailored surface topography. Therefore, we coated the structured PEEK surfaces with a thin alumina layer by pulsed laser deposition (PLD) to get identical surface chemistry on each substrate. Such alumina-coated PEEK surfaces are used as a model to investigate the effect of the surface topography on the wetting independent from the surface chemistry. Prepared surfaces bring advantages of enhanced wetting, multiscaled topography, proven biocompatibility (alumina layer), and low elastic modulus (PEEK as substrate), which together may trigger the use of PEEK in bone and other implant applications.
Melt-textured YBa 2 Cu 3 O 7−y (Y123) containing fine particles of Y 2 BaCuO 5 (Y211) has been prepared from Y123/Y211 powder that was attrition milled with 1 wt% CeO 2 addition, and the microstructure has been examined. Fine and spherical Y211 particles (less than 1 µm in size) are found to be homogeneously dispersed within the melt-textured Y123 domain. Many dislocations are observed to be formed around the trapped Y211 and the Ba(Ce, Zr)O 3 inclusions, which were formed as a result of CeO 2 addition and ZrO 2 introduction from the ZrO 2 jar and ball used for attrition milling. CuO stacking faults were also observed around the trapped Y211; these were initiated at the Y123/Y211 interface and extended into the Y123 matrix. Each stacking fault has a lenticular shape, with a width of a few tens of nanometres and a length of a few hundred nanometres, and the faults developed along the [100] and [010] directions of the Y123. The formation mechanism of the stacking fault was discussed together with the formation of the platelet structure (the elongated Ba-Cu-O phase) on the basis of an oxygenation-induced decomposition of the Y123 phase. It is concluded that the prolonged oxygenation heat treatment producing the tetragonal-to-orthorhombic phase transformation is responsible for the formation of the platelet structure and possibly for the formation of the stacking faults.
The effects of lithium doping on the electrical properties and ageing effect of ZnSnO (ZTO) thin films fabricated using a sol-gel process were investigated. As the Li content increased from 0 to 15 at%, the saturation mobility increased until 3 at% of Li and then decreased. The sub-threshold swing and on/off ratio were improved with the increase in Li content. In addition, Li (3 at%)-ZTO showed the smallest V TH change of 2.52 V among the thin film transistors (TFTs) in a positive bias stress (PBS) test. To observe the influence of Li on the ageing effect of TFTs, unpassivated Li-ZTO TFTs were stored under ambient conditions for 120 days. As a result of comparing the electrical characteristics of Li-ZTO TFTs after different durations of air exposure, the on/off ratio and sub-threshold swing of the Li (7 at%)-ZTO sample were almost unchanged when compared to those of ZTO. An x-ray photoelectron spectroscopy analysis of the O 1s core level showed that the relative area of oxygen vacancies (V O ) decreased from 27.2 to 19.6% as the Li content increased from 0 to 15 at%. A spectroscopic ellipsometer analysis showed that Li (3 at%)-ZTO had the smallest optical band gap of 3.68 eV. From the result of the band alignment, it was confirmed that the Fermi level (E F ) of Li (3 at%)-ZTO was located at the closest position to the conduction band minimum. Despite the reduction of the oxygen vacancy, the reason for the increasing electron concentration was due to the Li atom being preferentially located in the interstitial site, which released the free electron in the ZnO matrix. As a result, Li (3 at%)-ZTO showed improved electrical properties in the saturation mobility and PBS with stability under an ambient environment.
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