No abstract

No abstract

No abstract

No abstract

No abstract

No abstract

The fracture behaviour of borosilicate glass reinforced by molybdenum and/or vanadium particles has been investigated. For the addition of 5 vol% molybdenum particles, two processing procedures have been tested and the influence of volume fraction of vanadium particles (in the range 2 to 30~01%) on fracture resistance has been assessed. The use of chevron-notched specimens in threepoint bendir.g has been shown to be a reliable method for the evaluation of fracture toughness even at toughness levels of order 0.7 to 1.3 M P a f i . The existence of subtle differences in fracture behaviour of glass-composites having comparable volume fractions of molybdenum particles but obtained by two different processing procedures has been established by statistical treatment of the fracture toughness data. An increase in the volume fraction of metallic particles results in an increase of the fracture resistance and the measured fracture toughness level. Toughening mechanisms which have been identified include both the plastic deformation of particles and the bridging of cracks by ductile particles. Some particle cleavage and debonding has been observed, which indicates that a decrease in particle plasticity, probably induced by processing or due to constraints imposed by the rigid matrix, is responsible for a smaller than expected enhancement of the fracture toughness. a =half diagonal of Vickers hardness impression a, = theoretical crack length in chevron notch specimens corresponding to YZin B = thickness of the bend specimen c = crack lengths measured from the centre of Vicker's impression d = mean value of particle size E = Young's modulus H (HV 0.5) = Vickers hardness F, = critical force corresponding to unstable fracture initiation F,, F, , , = fracture force and maximum force Krcv = fracture toughness calculated using Vickers indentation technique K,, = fracture toughness determined by means of chevron notched specimen KO, m = coefficients of two-parameter Weibull analysis L,, L, = inner and outer span, respectively, in four point bending test L = span in three point bending test R =fracture stress in four point bending test L+ = volume fraction of metallic particles W = height of the bend specimen Y&,, = minimum in the calibration function curve yi , ym, yc = fracture energy of inclusion, matrix, and composite, respectively

Bacterial infection associated with medical implants is a major threat to healthcare. This work reports the fabrication of Copper(II)–Chitosan (Cu(II)–CS) complex coatings deposited by electrophoretic deposition (EPD) as potential antibacterial candidate to combat microorganisms to reduce implant related infections. The successful deposition of Cu(II)–CS complex coatings on stainless steel was confirmed by physicochemical characterizations. Morphological and elemental analyses by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy verified the uniform distribution of copper in the Chitosan (CS) matrix. Moreover, homogeneous coatings without precipitation of metallic copper were confirmed by X-ray diffraction (XRD) spectroscopy and SEM micrographs. Controlled swelling behavior depicted the chelation of copper with polysaccharide chains that is key to the stability of Cu(II)–CS coatings. All investigated systems exhibited stable degradation rate in phosphate buffered saline (PBS)–lysozyme solution within seven days of incubation. The coatings presented higher mechanical properties with the increase in Cu(II) concentration. The crack-free coatings showed mildly hydrophobic behavior. Antibacterial assays were performed using both Gram-positive and Gram-negative bacteria. Outstanding antibacterial properties of the coatings were confirmed. After 24 h of incubation, cell studies of coatings confirms that up to a certain threshold concentration of Cu(II) were not cytotoxic to human osteoblast-like cells. Overall, our results show that uniform and homogeneous Cu(II)–CS coatings with good antibacterial and enhanced mechanical stability could be successfully deposited by EPD. Such antibiotic-free antibacterial coatings are potential candidates for biomedical implants.