A New Generation of Flat Rheology Invert Drilling Fluids

The use of high resolution electron microscopy (HREM) to determine the atomic structure of grain boundaries and interfaces is a topic of great current interest. Grain boundary structure has been considered for many years as central to an understanding of the mechanical and transport properties of materials. Some more recent attention has focussed on the atomic structures of metalsemiconductor interfaces which are believed to control electrical properties of contacts. The atomic structures of interfaces in semiconductor or metal multilayers is an area of growing interest for understanding the unusual electrical or mechanical properties which these new materials possess. However, although the point-to-point resolutions of currently available HREMs, ∼2-3Å, appear sufficient to solve many of these problems, few atomic models of grain boundaries and interfaces have been derived. Moreover, with a new generation of 300-400kV instruments promising resolutions in the 1.6-2.0 Å range, and resolutions better than 1.5Å expected from specialist instruments, it is an appropriate time to consider the usefulness of HREM for interface studies.

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Total etch dentin bonding systems: scanning electron microscopy of the resin-dentin hybrid layer

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100130092 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1092-1093

Author(s):

Jorge Perdigao

Keyword(s):

Composite Resin ◽

Mechanical Interlocking ◽

Hybrid Layer ◽

Agent Based ◽

Dentin Bonding ◽

Acid Agent ◽

Bond Strengths ◽

Main Component ◽

Bonding Systems ◽

New Generation

In 1955, Buonocore introduced the etching of enamel with phosphoric acid. Bonding to enamel was created by mechanical interlocking of resin tags with enamel prisms. Enamel is an inert tissue whose main component is hydroxyapatite (98% by weight). Conversely, dentin is a wet living tissue crossed by tubules containing cellular extensions of the dental pulp. Dentin consists of 18% of organic material, primarily collagen. Several generations of dentin bonding systems (DBS) have been studied in the last 20 years. The dentin bond strengths associated with these DBS have been constantly lower than the enamel bond strengths. Recently, a new generation of DBS has been described. They are applied in three steps: an acid agent on enamel and dentin (total etch technique), two mixed primers and a bonding agent based on a methacrylate resin. They are supposed to bond composite resin to wet dentin through dentin organic component, forming a peculiar blended structure that is part tooth and part resin: the hybrid layer.

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Low-voltage, high-resolution scanning electron microscopy of polymers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100127037 ◽

1987 ◽

Vol 45 ◽

pp. 466-467 ◽

Cited By ~ 1

Author(s):

S. J. Krause ◽

W.W. Adams ◽

S. Kumar ◽

T. Reilly ◽

T. Suziki

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Low Voltage ◽

Chromatic Aberration ◽

Image Resolution ◽

Resolution Limit ◽

Crossover Point ◽

New Generation ◽

Beam Damage ◽

Scanning Electron

Scanning electron microscopy (SEM) of polymers at routine operating voltages of 15 to 25 keV can lead to beam damage and sample image distortion due to charging. Imaging polymer samples with low accelerating voltages (0.1 to 2.0 keV), at or near the “crossover point”, can reduce beam damage, eliminate charging, and improve contrast of surface detail. However, at low voltage, beam brightness is reduced and image resolution is degraded due to chromatic aberration. A new generation of instruments has improved brightness at low voltages, but a typical SEM with a tungsten hairpin filament will have a resolution limit of about 100nm at 1keV. Recently, a new field emission gun (FEG) SEM, the Hitachi S900, was introduced with a reported resolution of 0.8nm at 30keV and 5nm at 1keV. In this research we are reporting the results of imaging coated and uncoated polymer samples at accelerating voltages between 1keV and 30keV in a tungsten hairpin SEM and in the Hitachi S900 FEG SEM.

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