Home>ASTM Standards>ASTM F1438-93(R2020) pdf free download

ASTM F1438-93(R2020) pdf free download

ASTM F1438-93(R2020) pdf free download.Standard Test Method for Determination of Surface Roughness by Scanning Tunneling Microscopy for Gas Distribution System Components
1. Scope
1.1 The purpose ofthis test method is to define a method for analyzing the surface texture of the above-mentioned compo- nents using a scanning tunneling microscope (STM). STM is a noncontact method of surface profiling that can measure three-dimensional surface features in the nanometer size range, which can then be used to represent the surface texture or to provide figures ofmerit. Application ofthis test method, where surface texture is used as a selection criterion, is expected to yield comparable data among different components tested. 1.2 Limitations: 1.2.1 This test method is limited to characterization of stainless steel surfaces that are smoother than R a = 0.25 µm, as determined by a contact-stylus profilometer and defined by ANSI B46.1. The magnifications and height scales used in this test method were chosen with this smoothness in mind. 1.2.2 Intentional etching or conductive coating of the sur- face are considered modifications ofthe gas-wetted surface and are not covered by this test method. 1.2.3 This test method does not cover steels that have an oxide layer too thick to permit tunneling under the test conditions outlined in 11.3. 1.3 This technique is written with the assumption that the STM operator understands the use of the instrument, its governing principles, and any artifacts that can arise. Discus- sion of these points is beyond the scope of this test method. 1.4 The values stated in SI units are to be regarded as the standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.6 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Terminology
3.1 Definitions ofTerms Specific to This Standard: 3.1.1 artifact—any contribution to an image from other than true surface morphology. This could include such examples as vibration, electronic noise, thermal drift, or tip imperfections. 3.1.2 center line (graphical center line)—line parallel to the direction ofprofile measurement, such that the sum ofthe areas contained between it and the profile contained on either side are equal (see Calculation Section).3.1.4 current— in this context, the tunneling current (ex- pressed in nanoamperes) that flows in either direction between the tip and surface, under the conditions specified. 3.1.5 feature height—datum (height in the z-direction) of any point in the scan area, relative to the lowest point in the scan area, as derived from tunneling current during tip raster- ing. 3.1.6 filter—process of modification of surface data for purposes of numerical analysis or data presentation. Examples include high or low pass filters and plane-fitting. 3.1.7 gold ruled grating—gold surface having uniformly spaced grooves of known depth and separation; used for micrometer scale x-y calibration. 3.1.8 illuminated surface—three-dimensional image repre- sentation that simulates a reflective surface illuminated obliquely or from overhead. 3.1.9 image—surface topography represented by plotting feature height as a function of tip position. The feature height data is derived from the amount of tunneling current flowing between the tip and surface during rastering. 3.1.10 line plot—three-dimensional image given as side-by- side surface profiles. 3.1.11 mean roughness (R a )—average deviation from the mean of all profile heights (see algebraic definition in the Calculation Section). 3.1.12 peak—highest point between two crossing points ofa profile and its center line.

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