Student Number : 0210528 - PhD thesis - School of Mining Engineering - Faculty of Engineering and the Built Environmnet / This thesis describes the development of a directional primer charge for use in blasting in mining operations. The directional primer charge is an explosive gun which takes the place of a standard primer charge in a blasthole. It is a shaped charge which directs the explosive energy forwards into the blasthole. Its effectiveness is enhanced by a metal liner which is located at a specified stand-off distance from the toe of the hole. The explosive energy of the column charge is converted into the kinetic energy of the metal liner which transforms into an ultrasonic slug. This in turn converts into the impact energy of the slug impacting on the rock. This rock is axially compressed to such a degree that a radial fracture is developed. This radial fracture is termed an umbrella crack. Prior to the development of the directional primer charge, the phenomenon of the umbrella crack had only been observed in experimental Perspex blasting models and its formation mechanism had never been satisfactorily explained. If the directional primer charge could cause an umbrella crack in hard rock mining at the end of blastholes, then more rock would be broken out per blast than is currently achieved in practice. This thesis records the historical development of the explosive shaped charge with particular reference to the development of the explosively-forged projectile. It describes the classical theories and models which apply in determining the theoretical prediction of the physical properties of the designed directional primer charge. It describes the experimental procedures and measurements using flash X-ray radiography and electronic shorting screens to freeze the flight of a metal slug traveling at speeds of over 2000 metres per second. Underground tests were undertaken under full mining production conditions to compare the rock breaking effects of various designs. The theoretical calculation of the extent of the movement of the rock at the toe of the blasthole indicates that umbrella cracks should be formed. The underground tests confirm their formation. It is concluded that the use of the directional primer charge in stoping operations can improve the blasting efficiency in South African hard rock mines by up to 15 %.

The development of layer-oriented two-dimensional conjugated metal-organic frameworks (2D c-MOFs) enables an access to direct charge transport, dial-in lateral/vertical electronic devices and unveil transport mechanisms, but remains a significant synthetic challenge. Here we report the novel synthesis of metal-phthalocyanine-based p-type semiconducting 2D c-MOF films (Cu2[PcM-O8], M=Cu or Fe) with an unprecedented edge-on layer-orientation at the air/water interface. The edge-on structure for-mation is guided by the pre-organization of metal-phthalocyanine ligands, whose basal plane is perpendicular to the water surface due to their π-π interaction and hydrophobicity. Benefiting from the unique layer orientation, we are able to investigate the lateral and vertical conductivities by DC methods, and thus demonstrate an anisotropic charge transport in the resulting Cu2[PcCu-O8] film. The directional conductivity studies combined with theoretical calculation identify that the intrinsic conductivity is dominated by charge transfer along the interlayer pathway. Moreover, a macroscopic (cm2-size) Hall-effect measurement reveals a Hall mobility of ~4.4 cm2 V-1 s-1 for the obtained Cu2[PcCu-O8] film. The orientation control in semiconducting 2D c-MOFs will enable the develop-ment of various optoelectronic applications and the exploration of unique transport properties.