Replicating Nanostructures on Silicon by Low Energy Ion Beams

We report on a nanoscale patterning method on Si substrates using self-assembled metal islands and low-energy ion-beam irradiation. The Si nanostructures produced on the Si substrate have a one-to-one correspondence with the self-assembled metal (Ag, Au, Pt) nanoislands initially grown on the substrate. The surface morphology and the structure of the irradiated surface were studied by high-resolution transmission electron microscopy (HRTEM). TEM images of ion-beam irradiated samples show the formation of sawtooth-like structures on Si. Removing metal islands and the ion-beam induced amorphous Si by etching, we obtain a crystalline nanostructure of Si. The smallest structures emit red light when exposed to a UV light. The size of the nanostructures on Si is governed by the size of the self-assembled metal nanoparticles grown on the substrate for this replica nanopatterning. The method can easily be extended for tuning the size of the Si nanostructures by the proper choice of the metal nanoparticles and the ion energy in ion-irradiation. It is suggested that off-normal irradiation can also be used for tuning the size of the nanostructures.Comment: 12 pages, 7 figures, regular paper submitted to Nanotechnolog

Transformation of Quartz to Tridymite in the Presence of Binary Silicate Liquids

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66429/1/j.1151-2916.1967.tb15146.x.pd

Developmentally Sensitive Implementation of Core Elements of Evidence-Based Treatments: Practical Strategies for Youth With Internalizing Disorders

MANY TREATMENT APPROACHES for psychological disorders among children and adolescents are downward extensions of adult treatment models. According to Barrett (2000), when treatments for childhood disorders are based on cognitive behavioral models of adult disorders, clinicians may make inaccurate assumptions, such as viewing children as “little adults,” thereby failing to adjust treatment terminology for children and ignoring contextual factors such as families and peers. Subscribing to adult models may also result in a lack of awareness of research findings in the field of developmental psychology (e.g., cognitive abilities, social skills, emotion regulation) and, consequently, implementation of treatment strategies in a similar manner across levels of development (e.g., assuming all children possess the same level of meta-cognitive skills). As Kingery and colleagues (2006) emphasize, simply utilizing a treatment that has been developed for youth is not sufficient. Particularly when implementing manual-based CBT for youth with internalizing disorders, clinicians must be knowledgeable, creative, and flexible, taking each child’s individual cognitive, social, and emotional skills into consideration to provide the most developmentally appropriate intervention

The composition and technology of polychrome enamels on Chinese ruby‐backed plates identified through nondestructive micro‐X‐ray fluorescence

This research presents non‐destructive analyses of Chinese enamelled copper and porcelain decorated with polychrome enamels. This study utilises two key, high‐value art works with complex enamelling in the collection of the Victoria and Albert Museum (London, UK) to elucidate the composition and technology of objects with ruby‐backed decoration. These plates date from early Qing dynasty and are associated with the Yongzheng (1723–1735) and early Qianlong (1735–1796) periods. The goal of this research is to investigate the hypothesis that ruby‐backed plates in these two mediums are decorated with the same enamels and possibly manufactured in mutual enamelling workshops, which is a current topic of debate among scholars. Ten different enamel colours and the gilding on each plate were analysed and evaluated with micro‐X‐ray fluorescence to study the opacifiers and pigments. The results show that the enamels on these two works utilise the same opacifier and the consistent pigments in the white, ruby, pink, green, yellow, turquoise green, and blue enamels. Compositional differences were identified in the underdrawings, purple enamels, and gilding. The results demonstrate that Chinese painted enamels and overglazes on porcelain share mutual technology in most, but not all, of the polychrome decoration, which impacts upon our knowledge of technological organisation in the manufacture of these objects. Micro‐X‐ray fluorescence has been shown to be an effective and robust technique for the nondestructive study of decorative surfaces in these two material types

Relative energetics and structural properties of zirconia using a self-consistent tight-binding model

We describe an empirical, self-consistent, orthogonal tight-binding model for zirconia, which allows for the polarizability of the anions at dipole and quadrupole levels and for crystal field splitting of the cation d orbitals. This is achieved by mixing the orbitals of different symmetry on a site with coupling coefficients driven by the Coulomb potentials up to octapole level. The additional forces on atoms due to the self-consistency and polarizabilities are exactly obtained by straightforward electrostatics, by analogy with the Hellmann-Feynman theorem as applied in first-principles calculations. The model correctly orders the zero temperature energies of all zirconia polymorphs. The Zr-O matrix elements of the Hamiltonian, which measure covalency, make a greater contribution than the polarizability to the energy differences between phases. Results for elastic constants of the cubic and tetragonal phases and phonon frequencies of the cubic phase are also presented and compared with some experimental data and first-principles calculations. We suggest that the model will be useful for studying finite temperature effects by means of molecular dynamics.Comment: to be published in Physical Review B (1 march 2000

Reaction Between Nitrogen and Spinel in Chromium

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66029/1/j.1151-2916.1968.tb15671.x.pd

Observations from Preliminary Experiments on Spatial and Temporal Pressure Measurements from Near-Field Free Air Explosions

It is self-evident that a crucial step in analysing the performance of protective structures is to be able to accurately quantify the blast load arising from a high explosive detonation. For structures located near to the source of a high explosive detonation, the resulting pressure is extremely high in magnitude and highly non-uniform over the face of the target. There exists very little direct measurement of blast parameters in the nearfield, mainly attributed to the lack of instrumentation sufficiently robust to survive extreme loading events yet sensitive enough to capture salient features of the blast. Instead literature guidance is informed largely by early numerical analyses and parametric studies. Furthermore, the lack of an accurate, reliable data set has prevented subsequent numerical analyses from being validated against experimental trials. This paper presents an experimental methodology that has been developed in part to enable such experimental data to be gathered. The experimental apparatus comprises an array of Hopkinson pressure bars, fitted through holes in a target, with the loaded faces of the bars flush with the target face. Thus, the bars are exposed to the normally or obliquely reflected shocks from the impingement of the blast wave with the target. Pressure-time recordings are presented along with associated Arbitary-Langrangian-Eulerian modelling using the LS-DYNA explicit numerical code. Experimental results are corrected for the effects of dispersion of the propagating waves in the pressure bars, enabling accurate characterisation of the peak pressures and impulses from these loadings. The combined results are used to make comments on the mechanism of the pressure load for very near-field blast events

Grain Size Control of Tetragonal Zirconia Polycrystals Using the Space Charge Concept

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65680/1/j.1151-2916.1990.tb06449.x.pd

Computer Simulation of Final-Stage Sintering: II, Influence of Initial Pore Size

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65612/1/j.1151-2916.1990.tb06687.x.pd