The quest to create superhard materials rarely strays from the use of high-pressure synthetic methods, which typically require gigapascals of applied pressure. We report that rhenium diboride (ReB2), synthesized in bulk quantities via arc-melting under ambient pressure, rivals materials produced with high-pressure methods. Microindentation measurements on ReB2 indicated an average hardness of 48 gigapascals under an applied load of 0.49 newton, and scratch marks left on a diamond surface confirmed its superhard nature. Its incompressibility along the c axis was equal in magnitude to the linear incompressibility of diamond. In situ high-pressure x-ray diffraction measurements yielded a bulk modulus of 360 gigapascals, and radial diffraction indicated that ReB2 is able to support a remarkably high differential stress. This combination of properties suggests that this material may find applications in cutting when the formation of carbides prevents the use of traditional materials such as diamond.

Biomechanical and biological factors can co-dependently influence the establishment of implant-tissue integration; thus, concurrent evaluation of these factors should provide a better understanding of osseointegration. This study aimed to establish and validate an in vivo rat model frequently used in molecular/cellular biology for implant biomechanical studies. We tested the hypotheses that the implant push-in test assesses the degree of osseointegration by the breakpoint load at the implant-tissue interface and that it sensitively differentiates between the effects of different implant surface topographies. The implant push-in test, which produces a consistent load-displacement measurement, was used to test miniature cylindrical titanium implants placed at the distal edge of the adult rat femur. The push-in test values obtained at each post-implantation healing point (weeks 0, 2, 4, and 8) significantly increased in a time-dependent manner. The implant surface after the push-in test was associated with remnant tissues containing host-derived elements, such as calcium, phosphate, and sulfate. In this model, acid-etched implants (average roughness, 0.159 microm) showed significantly greater push-in test values than did turned implants (average roughness, 0.063 microm) throughout the experimental period (p < 0.0001). These results support the validity of the push-in test in rats, which may be used as a rapid and sensitive biomechanical assay system for implant osseointegration research.

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GLARE (glass-reinforced aluminum laminate) is a new class of fi ber metal laminates for advanced aerospace structural applications. It consists of thin aluminum sheets bonded together with unidirectional or biaxially reinforced adhesive prepreg of high-strength glass fi bers. GLARE laminates offer a unique combination of properties such as outstanding fatigue resistance, high specific static properties, excellent impact resistance, good residual and blunt notch strength, fl ame resistance and corrosion properties, and ease of manufacture and repair. GLARE laminates can be tailored to suit a wide variety of applications by varying the fi ber/resin system, the alloy type and thickness, stacking sequence, fi ber orientation, surface pretreatment technique, etc. This article presents a comprehensive overview of the mechanical properties of various GLARE laminates under different loading conditions.