Fracture Characteristics of Borosilicate Glasses Reinforced by Metallic Particles

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

Effects of Laminate Architecture on Fracture Resistance of Sponge Biosilica: Lessons from Nature

“…A common strategy for toughening involves the addition of fine, well-bonded metallic particles. Studies have been performed with Ni, [20] Cu, [21] Mo, [22] and Al. [23] Enhancement of the toughness is derived from plastic stretching of the particles in the wake of an advancing matrix crack.…”

Addition of platinum and silver nanoparticles to toughen dental porcelain

“…As discussed by Dlouhy et al 22) , an effective crack/ particle interaction may exist between the particles and the glass matrix if there is a perfect bond between both constituents. The inherent ductility of the metallic phase can be utilized to inhibit propagation of a running crack through the nanoparticles; in other words, a crack can be bridged by stretching nanoparticles.…”

“…These metals and alloys were either in the form of particles [10][11][12][13][14] or chopped fibers 15,16) and had sizes of the order of micrometers. The two most plausible mechanisms that have been proposed for toughening of the glass matrix by the addition of particles are bridging of cracks by stretching particles and crack deflection around particles 22) . Thus, metal particles are expected to increase the fracture resistance of porcelain in dental applications.…”

Effects of dental porcelain containing silver nanoparticles on static fatigue

“…Another possible mechanism is the crack-bridging phenomenon that occurs when a ductile metal acts to inhibit the propagation of cracks. This inherent ductility of the metallic phase thus inhibited the propagation of cracks running through the silver nanoparticles 14) . Lastly, an ion-exchange reaction between the sodium ions and silver ions in the glass matrix produced compressive stress at the surface 5) , thus increasing the fracture toughness of NS porcelain by chemical strengthening.…”

“…Various dental porcelain reinforcement methods have been recommended to increase their material strength and fracture toughness 2) , and one such method is the addition of ductile metal particles. These metal particles were expected to increase flexion resistance and provide crack-bridging ability 3) , or to provide more resistance to crack initiation due to ion exchange between porcelain surface and the metal particles deposited on the surface 4) . In a previous study 5) , the authors have examined the effects of adding silver nanoparticles to porcelain powder on the residual stress and fracture toughness of sintered bodies after firing.…”