ASTM D6056-96

Standard Test Method for Determining Concentration of Airborne Single-Crystal Ceramic Whiskers in the Workplace Environement by Transmission Electron Microscopy

SCOPE
1.1 This test method covers the sampling methods and analysis techniques used to assess the airborne concentration and size distribution of single-crystal ceramic whiskers (SCCW), such as silicon carbide and silicon nitride, which may occur in and around the workplace where these materials are manufactured, processed, transported, or used. This test method is based on the filtration of a known quantity of air through a filter. The filter is subsequently evaluated with a transmission electron microscope (TEM) for the number of fibers meeting appropriately selected morphological and compositional criteria. This test method has the ability to distinguish among different types of fibers based on energy dispersive X-ray spectroscopy (EDS) analysis and selected area electron diffraction (SAED) analysis. This test method may be appropriate for other man-made mineral fibers (MMMF).
1.2 This test method is applicable to the quantitation of fibers on a collection filter that are greater than 0.5 µm in length, less than 3 μm in width, and have an aspect ratio equal to or greater than 5:1 (1). The data are directly convertible to a statement of concentration per unit volume of air sampled. This test method is limited by the amount of coincident interference particles.
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.4 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 appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-Dec-1996
• Technical Committee: D22 - Air Quality
• Drafting Committee: D22.04 - Workplace Air Quality

Relations

• Replaced By: ASTM D6056-96(2001) - Standard Test Method for Determining Concentration of Airborne Single-Crystal Ceramic Whiskers in the Workplace Environement by Transmission Electron Microscopy
• Effective Date: 10-Dec-1996
• Referred By: ASTM D6058-96(2016) - Standard Practice for Determining Concentration of Airborne Single-Crystal Ceramic Whiskers in the Workplace Environment
• Effective Date: 10-Dec-1996

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 6056 – 96
Standard Test Method for
Determining Concentration of Airborne Single-Crystal
Ceramic Whiskers in the Workplace Environment by
Transmission Electron Microscopy
This standard is issued under the fixed designation D 6056; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 1356 Terminology Relating to Sampling and Analysis of
Atmospheres
1.1 This test method covers the sampling methods and
D 4532 Test Method for Respirable Dust in Workplace
analysis techniques used to assess the airborne concentration
Atmospheres
and size distribution of single-crystal ceramic whiskers
D 6057 Test Method for Determining Concentration of
(SCCW), such as silicon carbide and silicon nitride, which may
Airborne Single-Crystal Ceramic Whiskers in the Work-
occur in and around the workplace where these materials are
place Environment by Phase Contrast Microscopy
manufactured, processed, transported, or used. This test
D 6058 Practice for Determining Concentration of Airborne
method is based on the filtration of a known quantity of air
Single-Crystal Ceramic Whiskers in the Workplace Envi-
through a filter. The filter is subsequently evaluated with a
ronment
transmission electron microscope (TEM) for the number of
D 6059 Test Method for Determining Concentration of
fibers meeting appropriately selected morphological and com-
Airborne Single-Crystal Ceramic Whiskers in the Work-
positional criteria. This test method has the ability to distin-
place Environment by Scanning Electron Microscopy
guish among different types of fibers based on energy disper-
E 691 Practice for Conducting Interlaboratory Study to
sive X-ray spectroscopy (EDS) analysis and selected area
Determine the Precision of a Test Method
electron diffraction (SAED) analysis. This test method may be
appropriate for other man-made mineral fibers (MMMF).
3. Terminology
1.2 This test method is applicable to the quantitation of
3.1 Definitions:
fibers on a collection filter that are greater than 0.5 μm in
3.1.1 analytical sensitivity, n—airborne fiber concentration
length, less than 3 μm in width, and have an aspect ratio equal
represented by a single fiber counted in the TEM.
to or greater than 5:1 (1). The data are directly convertible to
3.1.1.1 Discussion—Although the terms fiber and whisker
a statement of concentration per unit volume of air sampled.
are, for convenience, used interchangeably in this test method,
This test method is limited by the amount of coincident
whiskers is correctly applied only to single-crystal fibers
interference particles.
whereas a fiber may be single- or poly-crystalline or may be
1.3 The values stated in SI units are to be regarded as the
noncrystalline.
standard. The values given in parentheses are for information
3.1.2 aspect ratio, n—the ratio of the length of a fiber to its
only.
width.
1.4 This standard does not purport to address all of the
3.1.3 fiber, n—for the purpose of this test method,an
safety concerns, if any, associated with its use. It is the
elongated particle having a minimum length of 0.5 μm, a width
responsibility of the user of this standard to establish appro-
less than 3 μm, and an aspect ratio equal to or greater than 5:1.
priate safety and health practices and determine the applica-
3.1.4 fibrous, adj—composed of parallel, radiating, or inter-
bility of regulatory limitations prior to use.
laced aggregates of fibers, from which the fibers are sometimes
2. Referenced Documents separable. That is, the crystalline aggregate may be referred to
as fibrous even if it is not composed of separable fibers, but has
2.1 ASTM Standards:
that distinct appearance. The term fibrous is used in a general
D 1193 Specification for Reagent Water
mineralogical way to describe aggregates.
3.1.5 man-made mineral fiber, n—any inorganic fibrous
material produced by chemical or physical processes.
This test method is under the jurisdiction of ASTM Committee D-22 on
3.1.6 single-crystal ceramic whisker, n— a man-made min-
Sampling and Analysis and is the direct responsibility of Subcommittee D22.04 on
eral fiber that has a single-crystal structure.
Analysis of Workplace Atmospheres.
Current edition approved Dec. 10, 1996. Published February 1997.
The boldface numbers in parentheses refer to a list of references at the end of
this test method. Annual Book of ASTM Standards, Vol 11.03.
3 5
Annual Book of ASTM Standards, Vol 11.01. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 6056
3.2 For definitions of other terms used in this test method, tive cassette assembly such as a three-piece cassette with an
see Terminology D 1356. extension cowl or retainer ring containing a 0.45-μm pore size
MCE filter and a support pad. Seal the cassette assembly with
4. Summary of Test Method
shrink tape. Reloading of used cassettes is not permitted.
4.1 The sample is collected on a mixed cellulose ester
7.2 Personal Sampling Pump—Use a portable battery-
(MCE) filter by drawing air, using a sampling pump, through
operated pump for personal sampling. Each pump must be
an open-face 25-mm electrically conductive sampling cassette
capable of operating within the range from 0.5 to 4 L/min and
assembly (2-4). A section of the filter is prepared and trans-
continuously over the chosen sampling period (2,3). The flow
ferred to a TEM grid and the fibers are identified, sized, and
must be free from pulsation. All pumps shall be calibrated prior
counted at a screen magnification in the range from 8000 to
to use (8).
12 0003 in the TEM in Section 11. Results are reported as a
7.3 Area Sampling Pump—Use a personal sampling pump
fiber concentration per unit volume of air and a fiber loading
or a non-portable high-volume pump for area sampling. Each
per unit area of filter. The airborne concentration is expressed
pump shall be capable of operating within the range from 0.5
as fibers per millilitre (f/mL) and the fiber loading is expressed
to 16 L/min and continuously over the chosen sampling period
as fibers per square millimetre (f/mm ). Optionally, a supple-
(2,3). The flow shall be free from pulsation. All pumps shall be
mentary low-magnification count in the range from 800 to
calibrated prior to use (8).
12003 may also be performed, using the criteria discussed in
7.4 Vinyl tubing or equivalent.
11.1.5, to provide comparison with PCM data.
7.5 Plasma Asher, a low-temperature asher (LTA) is re-
5. Significance and Use
quired to plasma-etch the collapsed MCE filter.
5.1 The SCCW may be present in the workplace atmosphere
7.6 Oxygen, used as a bleed gas for plasma asher.
where these materials are manufactured, processed, trans-
7.7 Vacuum Evaporator, for vapor deposition of conductive
ported, or used. This test method can be used to monitor
layers of carbon.
airborne concentrations of fibers in these environments. It may
NOTE 2—Sputter coaters and carbonaceous fiber coaters are not appro-
be employed as part of a personal or area monitoring strategy.
priate.
5.2 This test method is based on morphology, elemental
composition, and crystal structure. The analysis technique has 7.8 Specimen Grids, copper 200-mesh TEM grids for
the ability to positively identify SCCW. mounting the specimen for TEM examination.
7.9 Transmission Electron Microscope— A TEM capable of
NOTE 1—This test method assumes that the analyst is familiar with the
operating using an accelerating voltage of at least 80 kV. The
operation of TEM/EDS instrumentation and the interpretation of data
TEM must also be capable of performing EDS and SAED
obtained using these techniques.
analyses. A light-element X-ray analyzer capable of detecting
5.3 This test method is applicable for the measurement of
carbon, nitrogen, and oxygen is recommended. Use of a
the total population of SCCW fibers including fibers with
tilt-rotation holder as well as a double-tilt stage is also
diameters #0.1 μm.
recommended. The TEM must have a fluorescent screen
5.4 Results from the use of this test method shall be reported
inscribed with calibrated gradations. It must be capable of
along with 95 % confidence limits for the samples being
producing a spot less than 250 nm in diameter at crossover
studied. Individual laboratories shall determine their intralabo-
under routine analytical conditions. Scanning transmission
ratory coefficient of variation and use it for reporting 95 %
electron microscope (STEM) mode is allowed for this purpose.
confidence limits (2,5,6).
7.10 Sample Preparation Area, consisting of either a clean
6. Interferences
room facility or a room containing a positive pressure HEPA-
6.1 This test method has been designed to filter air for the
filtered hood.
determination of SCCW concentration. However, filtration of
7.11 Tweezers.
air also involves collection of extraneous particles and other
7.12 Scalpel Blades.
fibers that may not be of interest. Extraneous particles may
7.13 Large Glass Petri Dishes (approximately 90 mm in
obscure fibers by overlay or overloading of the filter. This
diameter).
situation can be managed by regulating the air volume sampled
7.14 Jaffe Washer.
and thus the filter loading. Fibers should appear separated from
7.15 Lens Tissue.
other particles to ensure an adequate opportunity for their
7.16 MCE Filters, 25 mm, 0.45 μm, and 0.22 μm.
recognition as separate entities in the TEM and accurate
7.17 Funnel/Filtration Assembly,25mm.
counting. Some coincident particulate agglomeration does
7.18 Acetone.
occur even with these guidelines. Analyze an alternate filter
with a reduced loading if the obscuring condition appears to
NOTE 3—Precaution: Acetone is a flammable liquid and requires
exceed 15 % of the filter area (7). Redeposition of a portion of
precautions not to ignite it accidently.
an overloaded filter is permitted only in circumstances where
7.19 Specification D 1193 Type II Water (particle free).
an alternate filter is not available and cannot be obtained
7.20 Purity of Reagents—Reagent grade chemicals shall be
through resampling (see 10.1.12).
used in all tests. Unless otherwise indicated, it is intended that
7. Apparatus and Reagents
all reagents conform to the specifications of the Committee on
7.1 Sampling Cassette—Use a 25-mm electrically conduc- Analytical Reagents of the American Chemical Society where
D 6056
NOTE 4—Deactivate the sampling pump prior to disconnecting the
such specifications are available. Other grades may be used,
cassette from the tubing.
provided it is first ascertained that the reagent is of sufficiently
high purity to permit its use without lessening the accuracy of
8.7 Submit at least one field blank (or a number equal to
the determination.
10 % of the total samples, whichever is greater) for each set of
samples. Remove the cap of the field blank briefly (approxi-
8. Sample Collection
mately 30 s) at the sampling site, then replace it. The field
8.1 Collect samples of airborne SCCW on MCE filters using
blank is used to monitor field sampling procedures. Field
sampling cassettes and pumps in accordance with Section 7.
blanks shall be representative of filters used in sample collec-
8.2 Remove the outlet plug from the sampling cassette and
tion (for example, same filter lot number).
connect to a sampling pump by means of flexible, constriction
8.8 Submit at least one unused and unopened sealed blank
proof tubing.
which is used to monitor the supplies purchased as well as
8.3 Perform a leak check of the sampling system by
procedures used in the laboratory. The sealed blank shall be
activating the pump with the closed cassette and rotameter (or
representative of filters used in sample collection (for example,
other flow measurement device) in line. Any flow indicates a
same filter lot number).
leak that must be eliminated before starting the sampling
operation.
9. Transport of Samples
8.4 Remove the inlet plug from the sampling cassette to
9.1 Ship the samples in a rigid container with sufficient
eliminate any vacuum that may have accumulated during the
packing material to prevent jostling or damage. Care shall be
leak test; then remove the entire inlet cap.
taken to minimize vibrations and cassette movement.
8.5 Conduct personal and area sampling as follows:
NOTE 5—Do not use shipping material that may develop electrostatic
8.5.1 For personal sampling, fasten the sampling cassette to
forces or generate dust.
the worker’s lapel in the worker’s breathing zone and orient
NOTE 6—Shipping containers for 25-mm sampling cassettes are com-
face down. Adjust the calibrated flow rate to a value between
mercially available and their use is recommended.
0.5 and 4 L/min (2,3). Typically, a sampling rate between 0.5
9.2 Include in the container a list of samples, their descrip-
and 2.5 L/min is selected (4-7). Also see Test Method D 4532.
tions, and all other pertinent information.
8.5.2 Place area samples on an extension rod facing down at
a 45° angle. Adjust the calibrated flow rate to a value between
10. Specimen Preparation
0.5 and 16 L/min (2,3). Typically, a sampling rate between 1
10.1 The objective of the specimen preparation technique is
and 10 L/min is selected (1).
to produce a thin carbon film (sufficiently clear for the TEM
8.5.3 Set the sampling flow rate and time to produce an
analysis) containing the particles from the filter surface. This
optimum fiber loading between 100 and 1300 f/mm (2-4) .
requires four separate preparation steps: (1) partially fuse or
The time of sampling can be estimated by using the following
collapse the filter to obtain a more continuous surface for the
equation:
evaporated carbon layer, (2) in a lowtemperature asher, lightly
~A ! ~F !
c L
t 5 (1) etch the filter surface to uncover any fibers that may have been
~Q! ~C ! 10
e
covered in the collapsing step, (3) evaporate a thin carbon film
over the collapsed and etched filter, and (4) dissolve the MCE
where:
filter and retain the carbon film with particles for TEM
A = active filter collection area (;385 mm for 25-mm
c
analysis. Procedures described as follows or other equivalent
filter),
methods (for example, dimethyl formamide (DMF) procedure
t = time, min,
F = fiber loading, f/mm , (9)) may be used to prepare samples.
L
Q = sampling flow rate, L/min,
10.1.1 Wipe the exterior of the cassettes with a damp cloth
C = estimated concentration of SCCW, f/mL, and
e before taking them into the clean preparation area to minimize
10 = conversion factor.
the possibility of contamination.
8.5.4 At a minimum, check
...