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Fatigue fracture properties of wood plastic composites (WPC) were investigated. The material was based on a wood flour/ polypropylene (PP) master batch, and prepared to be 30wt% and 50wt% wood flour contents by the addition of PP pellets. First, kneading temperature and screw speed of a uni-axial extruder were changed in some conditions, and 190°C and 20rpm were decided from tensile test of the injection-molded WPC specimens as the optimum manufacturing conditions. Next, tensile and fatigue tests were carried out for WPC specimens with 30wt% and 50wt% wood flour contents. The resultant tensile strength and tatigue life were largely improved as compared to neat PP specimens. When a lump of the master batch remained in the WPC specimen, the strength and life were reduced. It should be noted that, while fatigue life of the neat PP specimens was only 10 to 102 cycles to failure range at 30MPa maximum cyclic stress, those of WPC specimens with 30wt% and 50wt% contents were drastically extended to 103 to 104, and 105 to 106 cycles to failure, respectively. It was estimated that the major cause of fatigue damage in WPC specimens was craze occurring in the matrix, which initiated near the specimen surface, extended into the inner, and finally led to the unstable fracture. [ABSTRACT FROM AUTHOR]

Luminescent mercury selenide (HgSe) quantum dots have been synthesised by a phosphine-free method using oleic acid as a capping agent. The modification of experimental conditions such as temperature resulted in particles of various sizes (15–100 nm) and morphologies not previously seen in HgSe, with emission tuneable between 1000 nm and 1350 nm. [ABSTRACT FROM AUTHOR]

A comprehensive study of the optical properties of PbS nanocrystals (NCs) is reported that includes the temperature dependent absorption, photoluminescence (PL) and PL lifetime in the range of 3–300 K. The absorption and PL are found to display different temperature dependent behaviour though both redshift as temperature is reduced. This results in a temperature dependent Stokes shift which increases from ∼75 meV at 300 K with reducing temperature until saturating at ∼130 meV below ∼150 K prior to a small reduction to 125 meV upon cooling from 25 to 3 K. The PL lifetime is found to be single exponential at 3 K with a lifetime of τ1 = 6.5 μs. Above 3 K biexponential behaviour is observed with the lifetime for each process displaying a different temperature dependence. The Stokes shift is modelled using a three-level rate equation model incorporating temperature dependent parameter values obtained via fitting phenomenological relationships to the observed absorption and PL behaviour. This results in a predicted energy difference between the two emitting states of ∼6 meV which is close to the excitonic exchange energy splitting predicted theoretically for these systems. [ABSTRACT FROM AUTHOR]