Development of bond strength in hydraulic lime mortared brickwork

The first recorded use of hydraulic lime in construction can be traced back to at least two thousand years ago. Hydraulic lime, produced through either adding pozzolanic materials or calcining clay containing limestone, unlike air lime, can set and harden under water, developing strength through initial hydration reaction and subsequent carbonation. After WWII Portland cement mortars had almost completely replaced lime based mortars in modern construction. However, through conservation and specialist construction the benefits of hydraulic lime are becoming increasingly recognised. To support wider usage of these mortars there is a need for systematic study on the mortar properties and structural performance of lime mortared masonry. This thesis presents findings from a research programme conducted to develop understanding of the mechanical properties of natural hydraulic lime (NHL) mortared brickwork. The work focussed on the flexural strength of NHL mortared brickwork. A variety of material and environmental factors, including lime grade and supplier, mix proportion, sand type and age, have been investigated. In addition the research has completed an in-depth study on the influence of brick absorption characteristics on bond development. The two methods of flexural wall panel and bond wrench testing to establish flexural strength have been compared. In addition to flexural strength, initial shear strength and compressive strength of brickwork has also been investigated. A greater understanding of NHL mortared brickwork performance has been developed through this work. Performance of the brickwork has been related to properties of constituent materials and environmental factors. Recommendations for design performance of materials have been provided.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Thermal stability of high temperature Pb-free solder interconnect characterised by in-situ electron microscopy

The present investigation aimed to use in-situ heating experiment in a transmission electron microscope (TEM) to live characterize the thermal stability of a Cu/Ni-W-P interlayer/ZnAl solder interconnect. It demonstrated the TEM was able to detect live intermetallic compounds (IMCs) growth during heating. In addition, stress building up was evidenced by the progressive evolving of the dislocations at the interface between NiW-P interlayer and the ZnAl Solder. However, due to the μm to nm scale of specimens' dimensions required for electron microscopy, the sample preparation and data interpretation remains a challenge

Exploring the potentiality of standard sirens to probe cosmic opacity at high redshifts

In this work, using the Gaussian process, we explore the potentiality of future gravitational wave (GW) measurements to probe cosmic opacity at high redshifts through comparing its opacity-free luminosity distance (LD) with the opacity-dependent one from the combination of Type Ia supernovae (SNIa) and gamma-ray bursts (GRBs). The GW data, SNIa and GRB data are simulated from the measurements of the future Einstein Telescope, the actual Pantheon compilation and the latest observation of GRBs compiled by L. Amati {\it et al}, respectively. A nonparametric method is proposed to probe the spatial homogeneity of cosmic transparency at high redshift by comparing the LD reconstructed from the GW data with that reconstructed from the Pantheon and GRB data. In addition, the cosmic opacity is tested by using the parametrization for the optical depth, and the results show that the constraints on cosmic opacity are more stringent than the previous ones. It shows that the future GW measurements may be used as an important tool to probe the cosmic opacity in the high redshift region.Comment: 21pages, 3 figures accepted by EPJC. arXiv admin note: text overlap with arXiv:1912.0232

In-situ micro bend testing of SiC and the effects of Ga+ ion damage

The Young’s modulus of 6H single crystal silicon carbide (SiC) was tested with micro cantilevers that had a range of cross-sectional dimensions with surfaces cleaned under different accelerating voltages of Ga+ beam. A clear size effect is seen with Young’s modulus decreasing as the cross-sectional area reduces. One of the possible reasons for such size effect is the Ga+ induced damage on all surfaces of the cantilever. Transmission electron microscopy (TEM) was used to analyse the degree of damage, and the measurements of damage is compared to predictions by SRIM irradiation simulation

A novel scale-down cell culture and imaging design for the mechanistic insight of cell colonization within porous substrate

At the core of translational challenges in Tissue Engineering is the mechanistic understanding of the underpinning biological processes and the complex relationships among components at different levels, which is a challenging task due to the limitations of current tissue culture and assessment methodologies. Therefore, we proposed a novel scale-down strategy to deconstruct complex bio-matrices into elementary building blocks, which were resembled by thin modular substrate and then evaluated separately in miniaturised bioreactors using various conventional microscopes. In order to investigate cell colonization within porous substrate in this proof-of-concept study, TEM specimen supporters (10-30µm thick) with fine controlled open pores (100~600µm) were selected as the modular porous substrate and suspended in 3D printed bioreactor systems. Non-invasive imaging of human dermal fibroblasts cultured on these free-standing substrate using optical microscopes illustrated the complicated dynamic processes used by both individual and coordinated cells to bridge and segment porous structures. Further in situ analysis via SEM and TEM provided high quality micrographs of cell-cell and cell-scaffold interactions at micro-scale, depicted cytoskeletal structures in stretched and relaxed areas at nano-scale. Thus this novel scaled-down design was able to improve our mechanistic understanding of tissue formation not only at single- and multiple-cell levels, but also at micro- and nano-scales, which could be difficult to obtain using other methods

Formation and homogenisation of Sn-Cu interconnects by self-propagated exothermic reactive bonding

We produced SnCu interconnects by self-propagated exothermic reactions using AlNi NanoFoil at ambient conditions, through the instantaneous localised heat across the interfaces between Sn electroplated Cu substrates. This technique presents a great potential for electronics integration with minimal thermal effects to the components. However, the metastable phases resulted from the non-equilibrium interfacial reactions and solidification were inevitable under a highly transient regime due to a drastic heating/cooling (over 107 K/s). In this study, Finite Element Analysis was performed to predict the temperature profiles across bonding interfaces, which were subsequently correlated with the formation and homogenisation of the bonded structures during the bonding and post-bonding ageing process. It has been revealed that, for nano-sized metastable phases, their formation, morphologies and distribution were primarily attributed to the convective mass transportation, liquid-solid inter-diffusion, and directional non-equilibrium solidification of Sn in molten zone of the bonding interfaces. The non-equilibrium phases initially formed in the SnCu interconnects can be homogenised towards the equilibrium status by accelerated ageing. This was achieved through the coalescing and subsequent growth of the original nano-sized metastable phases, as a result of the solid-diffusion of Cu and Ag atoms at intergranular boundary regions of Sn grains, AlNi NanoFoil/Sn. and Cu/Sn interfaces