Structural Properties

The increase in surface area and surface free energy with decreasing particle size leads to changes in interatomic spacings. For Cu metallic clusters the interatomic spacing is observed to decrease with decreasing cluster size. This can be explained by the compressive strain induced by the internal pressure arising from the small radius of curvature in the nanoparticle . Conversely, for semiconductors and metal oxides there is evidence that interatomic spacings increase with decreasing particle size.


Kelsall, Nanoscale, p 25




Pore Structure of Slowly Cooled Mafic Intrusions

.....The glass films vary from a few microns to a few tens of microns thick, and are associated with strings of small lensoid grain boundary pockets formed by impingement during crystal growth. Additional porosity occurs as extensive liquid-filled pockets adjacent to included grains within oikocrysts and as large triangular pockets formed by impingement of planar-sided grains. Interstitial material within glass films, and the irregularity of film thickness along a single grain boundary, suggest that the present pore structure is representative of the pore structure before entrainment and eruption. Pore geometry is consistent with a dominant control by crystal growth during solidification, with little or no evidence for control by minimization of internal energies driven by textural equilibration. Similarities between liquid distribution in the crystalline nodules and that of late-stage, interstitial phases in fully solidified mafic cumulates from the Rum and Skaergaard intrusions demonstrate that the crystalline nodules provide information about the latest stages of solidification in slowly cooled mafic plutons. The highly permeable network of intersecting liquid films, lenses and pockets may promote in situ crystallization in the solidifying mush, explaining the common presence of adcumulates in such intrusions.

Textures in Partially Solidified Crystalline Nodules: a Window into the Pore Structure of Slowly Cooled Mafic Intrusions; Journal of Petrology 2007 48(7):1243-1264; doi:10.1093/petrology/egm016




Influence of radiation on material properties

High energy neutrons cause atoms to be displaced from their lattice sites to become self interstitials leaving behind an excess of vacancies. The vacancies and self interstitials may recombine so that the lattice reverts to its original state, or the defects may be attracted to sinks, such as grain boundaries. Alternatively, these defects may form clusters such as interstitial or vacancy loops, or the vacancies may create three dimensional clusters, that is, voids. Accompanying this defect generation is a loss in ductility together with an increase in the mechanical properties (strength and hardness). Swelling may also result from void formation. In steel this loss of ductility can be described quantitiatively by an increase in the ductile to brittle transition temperature as determined by the Charpy impact test. In addition, radiation damage reduces the high temperature shelf energy of the Charpy impact test curve. These changes in mechanical behaviour are of particular interest in the case of steel usedin nuclear reactor pressure vessels because of possible embrittlement induced failure during operation.

There are two factors that affect the properties of the pressure vessel steels; the microstructure, which can be altered by radiation damage, and the composition. A typical pressure vessel steel contains about 0.25 wt% carbon, which produces a mixed ferrite-pearlite microstructure on slow cooling from the austenite range. Among the metallic elements present in steel, copper is the most deleterious, probably because of its very limited solid solubility which results in the formation of precipitates. Long-term retention of the pearlite at a temperature below the eutectoid temperature leads to a spheroidite structure, spherical cementite in a ferrite matrix. In addition to carbon these steels contain a number of other alloying elements all of which are in solid solution in the ferrite. It was proposed that copper or copper microvoid precipitates form, having a diameterof about 0.3 nm, which cannot be observed by conventional transmission electron microscopy TEM. These precipitates cause embrittlement of the steel. experimentally the copper content in pressure vessel steel has been found responsible for much of the radiation induced shift in the transition temperature. The higher copper content steels show a substantial increase in yield strength compared to those with an increasing phosphorus content………

It is proposed that in radiation damaged steel, the surfaces of vacancy clusters formed in cascades have a strong binding interaction for imputities, such as copper, hence producing precipitates.

Books.google.co.uk, 13th international symposium



Crystalline Structure of Pancreatic Calculi

........The crystals were identified as calcite composed of CaCO3 in X-ray and electron diffraction studies. Scanning electron microscopy (SEM) revealed that the calculi consist of aggregations of rhombohedral, fang-shaped, botryoidal, foliaceous, and plate-shaped crystals. Some of them showed signs of partial dissolution on their surface. Transmission electron microscopy (TEM) showed crystals of various sizes and shapes either solitary or in clumps. The direct measurement of crystalline lattice intervals obtained from each crystal was 0.386 run in accordance with the diffraction data. Exocrine pancreatic cell debris are present in pancreatic calculus matrices.


The Crystalline Structure of Pancreatic Calculi, Journal of Electron Microscopy 43(2): 57-61 (1994, oxfordjournals.org