ASTM C1274-00(2006)
(Test Method)Standard Test Method for Advanced Ceramic Specific Surface Area by Physical Adsorption
Standard Test Method for Advanced Ceramic Specific Surface Area by Physical Adsorption
SIGNIFICANCE AND USE
Both suppliers and users of advanced ceramics can benefit from knowledge of the surface area of these materials. Results of many intermediate and final processing steps are controlled by, or related to, specific surface area of the advanced ceramic.
SCOPE
1.1 This test method covers determination of surface area of advanced ceramic materials. This test method specifies general procedures that are applicable to many commercial physical adsorption instruments. This test method provides specific sample outgassing procedures for listed materials, including silicon carbide, silicon nitride, and zirconium oxide. It includes additional general outgassing instructions for other advanced ceramic materials. The multipoint equation of Brunauer, Emmett and Teller (BET) along with the single point approximation of the BET equation form the basis for all calculations.
1.2 This test method does not include all existing procedures appropriate for outgassing advanced ceramic materials. The included procedures provided acceptable results for samples analyzed during round robin testing. The investigator must determine the appropriateness of listed procedures.
1.3 This test method uses SI units as standard. State all numerical values in terms of SI units unless specific instrumentation software reports surface area using alternate units. In this case, present both reported and equivalent SI units in the final written report. Many instruments report surface area as m2/g, instead of using correct SI units (m2/kg).
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
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: C1274 – 00 (Reapproved 2006)
Standard Test Method for
Advanced Ceramic Specific Surface Area by Physical
Adsorption
This standard is issued under the fixed designation C1274; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D1993 Test Method for Precipitated Silica-SurfaceArea by
Multipoint BET Nitrogen Adsorption
1.1 Thistestmethodcoversdeterminationofsurfaceareaof
E177 Practice for Use of the Terms Precision and Bias in
advanced ceramic materials.This test method specifies general
ASTM Test Methods
procedures that are applicable to many commercial physical
adsorption instruments. This test method provides specific
3. Terminology
sample outgassing procedures for listed materials, including
3.1 Definitions:
siliconcarbide,siliconnitride,andzirconiumoxide.Itincludes
3.1.1 adsorbate, n—material that has been retained by the
additional general outgassing instructions for other advanced
process of adsorption.
ceramic materials. The multipoint equation of Brunauer, Em-
2 3.1.2 adsorbent, n—any solid having the ability to concen-
mett andTeller (BET) along with the single point approxima-
trate significant quantities of other substances on its surface.
tion of the BET equation form the basis for all calculations.
3.1.3 adsorption, n—aprocessinwhichfluidmoleculesare
1.2 This test method does not include all existing proce-
concentrated on a surface by chemical or physical forces, or
dures appropriate for outgassing advanced ceramic materials.
both.
The included procedures provided acceptable results for
3.1.4 adsorptive, n—anysubstanceavailableforadsorption.
samples analyzed during round robin testing. The investigator
3.1.5 aliquant, n—a representative portion of a whole that
must determine the appropriateness of listed procedures.
divides the whole leaving a remainder.
1.3 This test method uses SI units as standard. State all
3.1.6 outgassing, n—theevolutionofgasfromamaterialin
numerical values in terms of SI units unless specific instru-
a vacuum or inert gas flow, at or above ambient temperature.
mentationsoftwarereportssurfaceareausingalternateunits.In
3.1.7 physical adsorption (van der Waals adsorption),
this case, present both reported and equivalent SI units in the
n—the binding of an adsorbate to the surface of a solid by
final written report. Many instruments report surface area as
2 2 forceswhoseenergylevelsapproximatethoseofcondensation.
m /g, instead of using correct SI units (m /kg).
3.1.8 surface area, n—the total area of the surface of a
1.4 This standard does not purport to address all of the
powder or solid including both external and accessible internal
safety concerns, if any, associated with its use. It is the
surfaces (from voids, cracks, open porosity, and fissures). The
responsibility of the user of this standard to establish appro-
area may be calculated by the BET (Brunauer, Emmett, and
priate safety and health practices and determine the applica-
Teller ) equation from gas adsorption data obtained under
bility of regulatory limitations prior to use.
specific conditions. It is useful to express this value as the
2. Referenced Documents specific surface area, for example, surface area per unit weight
3 of sample (m /g).
2.1 ASTM Standards:
3.1.9 surface area (BET), n— the total surface area of a
solid calculated by the BET (Brunauer, Emmett, Teller )
This test method is under the jurisdiction of ASTM Committee C28 on
equation, from nitrogen adsorption or desorption data obtained
Advanced Ceramics and is the direct responsibility of Subcommittee C28.03 on
under specific conditions.
Physical Properties and Performance.
3.1.10 surface area, specific, n—thearea,perunitmassofa
Current edition approved Jan. 1, 2006. Published January 2006. Originally
approved in 1994. Last previous edition approved in 2000 as C1274–00. DOI:
granular or powdered or formed porous solid, of all external
10.1520/C1274-00R06.
plusinternalsurfacesthatareaccessibletoapenetratinggasor
Brunauer, S., Emmett, P. H., and Teller, E., J. Am. Chem. Soc. 60, 1938, pp.
liquid.
309–319.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. Compilation of ASTM Standard Terminology, 8th ed, 1994.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C1274 – 00 (2006)
−1
4. Summary of Test Method levels attained are 10 Pa. Typical flushing gases are helium,
nitrogen,oramixtureofthetwo.Outgassingiscompletewhen
4.1 An appropriate sized sample (to provide at least the
duplicatesurfaceareaanalysesproduceresultswithinexpected
minimum surface area required for reliable results for the
instrument repeatability limits, when a constant residual vapor
instrument or apparatus used) is outgassed under appropriate
pressure is maintained upon isolation from the vacuum source,
conditions prior to analysis.
or when flushing gas composition is unaffected while passing
4.2 (Multipoint BET Analyses Only)—Volume of gas ad-
over the sample.
sorbed, or desorbed, is determined for a minimum of four
relative pressures within the linear BET transformation range
7. Apparatus
of the physical adsorption, or desorption, isotherm character-
7.1 Classical Vacuum Apparatus—Refer to Test Method
istic of the advanced ceramic. The linear range is that which
D1993 for apparatus description.
results in a least square correlation coefficient of 0.999 (pref-
7.2 Automated and Dynamic Flow Instruments—
erably 0.9999) or greater for the linear relationship used in the
Commercial instruments are available from several manufac-
BETgraph( ⁄(adsorbed volume * (1/relative pressure — 1))).Typically,the
turers for the measurement of specific surface area by physical
linear range includes relative pressures between 0.05 and 0.30,
adsorption. Some are automated versions of the classical
however, microporous materials usually require use of a range
vacuum apparatus. Others may use a gravimetric technique to
of lower relative pressures, such as 0.01 to 0.10.
determine the amount of adsorbed gas on the sample surface.
4.3 (Single Point BET Analyses Only)—Volume of gas
Additionally, commercial instruments are available which
adsorbed, or desorbed, is determined at the highest known
measure physical adsorption based on the dynamic flow
relativepressurewithinthelinearBETtransformationrangeof
method.
the physical adsorption, or desorption, isotherm. Typically, a
relative pressure of 0.30 is used. (It may be necessary to 8. Reagents and Materials
perform a multipoint analysis of the material first to determine
8.1 Liquid Nitrogen.
the optimum single point relative pressure.)
8.2 Nitrogen, 99.99 mole percent, with the sum of O,Ar,
4.4 The sample is accurately weighed (to at least 1% of the
CO , hydrocarbons (as CH ), and H O totaling less than 10
2 4 2
sample mass) after analysis. It is important to use an analytical
ppm, dry and oil-free, cylinder, or other source of purified
balance to determine the sample weight. The physical adsorp-
nitrogen.
tion instrument or apparatus measures the total amount of gas
8.3 Helium,99.99molepercent,withthesumofN,O ,Ar,
2 2
adsorbed onto, of desorbed from, the sample under analysis.
CO , hydrocarbons (as CH ), and H O totaling less than 10
2 4 2
The sample weight is then used to normalize the measured
ppm, dry and oil-free, cylinder, or other source of purified
results.Any error in the sample weight will be propagated into
helium, if needed for determination of void space above
the final BET surface area.
sample.
4.5 CalculationsarebasedontheBETequation,asrequired
8.4 Blended Nitrogen and Helium,dryandoil-free,cylinder,
by the instrument being used for the determination. The cross
orothersourceofblendedgases.Theactualcompositionofthe
sectional area for the adsorbate is taken to be 0.162 nm if
blend must be known. For use with dynamic flow instruments
nitrogen is used as the adsorptive. Use the appropriate value
only.
recommended by the instrument manufacturer for adsorptives
9. Sampling, Test Specimens, and Test Units
other than nitrogen. Report this cross sectional area with the
BET surface area results.
9.1 No specific instructions are given. However, it is impor-
tant that the aliquant being analyzed represent the larger bulk
5. Significance and Use sample from which it is taken. The bulk sample should be
homogenized before any sampling takes place. Best results are
5.1 Both suppliers and users of advanced ceramics can
obtained when a flowing bulk material is temporarily diverted
benefit from knowledge of the surface area of these materials.
into a collector for an appropriate time. It is better to sample
Results of many intermediate and final processing steps are
the entire flow for a short time than to sample a portion of the
controlled by, or related to, specific surface area of the
flow for a longer time. Collecting several small aliquants and
advanced ceramic.
combining them improves the reliability of the sampling
process. Rotating rifflers are available that satisfy these re-
6. Interferences
quirements.
6.1 This test method can be used to determine the internal
and external surface of a powder or solid only after these 10. Calibration and Standardization
su
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.