1、Designation: E 1582 04Standard Practice forCalibration of Temperature Scale for Thermogravimetry1This standard is issued under the fixed designation E 1582; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describe the temperature calibration ofthermogravimetric analyzers over the temperature range from25 to 1500 C and is
3、 applicable to commercial and custom-built apparatus. This calibration may be accomplished by theuse of either melting point standards or magnetic transitionstandards.1.2 The mass change curve in thermogravimetry resultsfrom a number of influences, some of which are characteristicof the specimen hol
4、der assembly and atmosphere rather thanthe specimen. The variations from instrument to instrumentoccur in the point of measurement of the temperature, thenature of the material, its size and packing, the geometry andcomposition of the specimen container, the geometry anddesign of the furnace, and th
5、e accuracy and sensitivity of thetemperature sensor and displaying scales. These all contributeto differences in measured temperatures, which may exceed20 C. In addition, some sample holder assemblies will showvariations of measured temperature with sample size orheating/cooling rate, or both. Since
6、 it is neither practical noradvisable to standardize sample holders or thermobalancegeometries, instruments may be calibrated by measurement ofthe deviation of a melting or magnetic (Curie Point) transitiontemperature from the standard reference temperature. Thisdeviation can be applied as a correct
7、ion term to subsequentmeasurements.1.3 This practice assumes that the indicated temperature ofthe instrument is linear over the range defined by a two-pointcalibration and that this linearity has been verified. These twocalibration temperatures should be as close to the experimentalmeasurements to b
8、e made as possible.1.4 This practice describes three procedures for temperaturecalibration of thermogravimetric analyzers using any typebalance. Procedures A and B use melting point standards withvertical and horizontal balances. Procedure C uses magnetictransition standards for calibration. Procedu
9、re A is designedspecifically for use with horizontal-type balances using exter-nal furnaces. Procedure B is designed specifically for use withvertical hang-down balances using either internal or externalfurnaces. No procedure is restricted to the use of the furnacetype described in that procedure.1.
10、5 Computer or electronic-based instruments, techniques,or data treatment equivalent to this procedure may be used.NOTE 1Since all electronic data treatments are not equivalent, theuser shall verify equivalency prior to use.1.6 The data generated by these procedures can be used tocorrect the temperat
11、ure scale of the instrument by either apositive or negative amount using either a two-point tempera-ture calibration procedure or a multi-point temperature calibra-tion with best line fit for the generated data.NOTE 2A single-point calibration may be used where this is the onlyprocedure possible or
12、practical. The use of a single-point procedure is notrecommended.1.7 SI units are standard.1.8 This practice is related to ISO 11358 but providesinformation and methods not found in ISO 11358 .1.9 This standard does not purport to address all of thesafety problems, if any, associated with its use. I
13、t is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:E 473 Terminology Relating to Thermal Analysis2E 691 Practice for Conducting an
14、Interlaboratory Study toDetermine the Precision of a Test Method2E 967 Practice for Temperature Calibration of DifferentialScanning Calorimeters and Differential Thermal Analyz-ers2E 1142 Terminology Relating to Thermophysical Proper-ties22.2 Other Standards:ISO 11358 Thermogravimetry (TG) of Polyme
15、rs GeneralPrinciples31This practice is under the jurisdiction of ASTM Committee E 37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.01 on TestMethods and Recommended Practices.Current edition approved May 1, 2004. Published June 2004. Originallyapproved in 1993. Last pre
16、vious edition approved in 2000 as E 1582 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from A
17、merican National Standardards Institute, 11 West 42nd Street,13th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3. Terminology3.1 DefinitionsTechnical terms used in this document aredefined in Terminology
18、E 473 and E 1142.3.1.1 magnetic reference temperaturethe observed tem-perature at which a change in the magnetic properties of amaterial in a magnetic field produces an apparent mass change.This temperature is read from the dynamic TG curve as thepoint of intersection of the extrapolated higher temp
19、eratureportion of the base line with a tangent drawn to the point ofgreatest slope of apparent mass-change curve. This tempera-ture most closely represents the Curie Point, that point on themass change curve where the magnetic effect of the standardmaterial has disappeared completely (see Fig. 1).NO
20、TE 3The position of the magnet and the design of the instrumentwill affect the direction of the mass change.4. Summary of Practice4.1 This practice provides a set of different procedures sincethermogravimetric apparatus is often of significantly differingdesign.4.2 Calibration of Analyzers Using Mel
21、ting PointStandardsThe calibration material is heated at a controlledrate in a controlled atmosphere through its melting region. Thetemperature of the standard is monitored and recorded continu-ously. In this practice, a small platinum mass is suspendedwithin a thermogravimetric analyzer specimen bo
22、at or panfrom a fusible link of the standard calibration material. As thestandard specimen is heated through the melting region, theplatinum mass is released. The mass is either caught in thespecimen boat or pan, producing an “action/reaction” blip onthe thermal curve, or is allowed to drop through
23、a hole in thebottom of the specimen boat or pan, producing a sharp,discontinuous mass loss. These events may be used to calibratethe thermogravimetric analyzer for the experimental conditionsused.4.3 Calibration of Analyzers Using Magnetic TransitionStandards:4.3.1 In this procedure, the apparent ma
24、ss change of one ormore of the magnetic transition standards is obtained under thenormal operating conditions of the instrument. The extrapo-lated endpoint temperature, (see Fig. 1), is determined andcompared with the established transition temperature for thematerial. The difference provides an adj
25、ustment or calibrationthat may be applied to the temperature scale of the instrument.4.3.2 The apparent mass change of the magnetic transitionmaterials is caused by the magnetic to nonmagnetic transitionin the presence of a magnetic field.4.4 Calibration of Analyzers That Have SimultaneousThermograv
26、imetry-Differential Scanning Calorimeter orThermogravimetry-Differential Thermal Analysis CapabilityThese instruments may be calibrated using melting temperaturestandards following Practice E 967.5. Significance and Use5.1 Thermogravimetric analyzers are used to characterize abroad range of material
27、s. In most cases, one of the desiredvalues to be assigned in thermogravimetric measurements isthe temperature at which significant changes in specimen massoccur. Therefore, the temperature axis (abscissa) of allapparent-mass-change curves must be calibrated accurately,either by direct reading of a t
28、emperature sensor, or by adjustingthe programmer temperature to match the actual temperatureover the temperature range of interest. In the latter case, this isaccomplished by the use of either melting point or magnetictransition standards.5.2 This practice permits interlaboratory comparison andintra
29、laboratory correlation of instrumental temperature scaledata.6. Interferences6.1 The reference metals are sensitive to impurities and mayoxidize at elevated temperatures. All runs shall be conducted inan oxygen-free inert purge gas of the same type to be used inthe experimental procedures.6.2 Care m
30、ust be taken to stay below temperatures at whichthe magnetic transition standard will react with the specimen orits holder.6.3 The atmosphere, purge gas type, purge gas flow rate,and heating will affect the calibration. These rates and condi-tions must be the same for both calibration and analysis.
31、Inaddition, high heating rates should be avoided, if possible. Dueto the differing heat exchange (emissivity and heat capacity)during the calibration and analysis, higher heating rates in-crease the error in the temperature measurement. The ICTACSixth International Test Program (4)4warns that heatin
32、g ratesabove 6C/min can produce errors in the temperature calibra-tion.7. Apparatus7.1 Thermogravimetric AnalyzerA system of related in-struments that are capable of continuously measuring the massof a specimen in a controlled atmosphere and in a controlledtemperature environment ranging from ambien
33、t to at least25 C above the temperature range of interest over a selectedtime period. This instrument shall consist of the following:7.1.1 Thermobalance, composed of:4The boldface numbers in parentheses refer to the list of references at the end ofthis practice.FIG. 1 Magnetic Reference TemperatureE
34、15820427.1.1.1 Furnace, to provide uniform controlled heating of aspecimen from 25 C to a constant temperature or at a constantrate within the applicable temperature range of this testmethod.7.1.1.2 Temperature Sensor, to provide an indication of thespecimen/furnace temperature to 6 0.1 C.7.1.1.3 A
35、continuously recording Balance, to measure thespecimen weight with a minimum capacity of 50 mg and asensitivity of 6 5 g.7.1.1.4 A means of maintaining the specimen/containerunder Atmospheric Control, of nitrogen or other inert gas of99.9 +% purity at a purge rate of 50 to 100 mL/min constant towith
36、in 6 5 mL/min.7.1.2 A Temperature Controller, capable of executing aspecific temperature program by operating the furnace betweenselected temperature limits at a specified heating rate between0.5 to 20 C/min constant to within 6 0.1 C/min or to anisothermal temperature that is maintained constant to
37、 6 0.5 Cfor a minimum of 10 min.7.1.3 A Recording Device, capable of recording and display-ing any fraction of the specimen weight (TGA thermal curve)including the signal noise, on the Y- axis versus any fraction oftemperature, including signal noise, on the X- axis.7.1.4 Containers (pans, crucibles
38、, and the like), that areinert to the specimen and will remain dimensionally stablewithin the temperature limits of this test method.8. Calibration and Standardization8.1 Calibration of ApparatusIf necessary, calibrate thetemperature sensor of the instrument at room temperature usingthe procedure de
39、scribed in the instrument manual.8.2 Calibration Materials:8.2.1 Melting Point StandardsFor the temperature rangecovered by many applications, the melting transition of the99.9+ % pure materials listed in Table 1 may be used forcalibration.NOTE 4It is recommended that the size of the wire used be 0.
40、25 mmin diameter. For sources of very pure fine metal wire, contact the ASTMInformation Center.NOTE 5The melting temperatures of the first seven materials given inthis table are taken from Mangum and Furukawa (1) and have beenselected as primary fixed points for the International Temperature Scale o
41、f1990. The remaining melting temperatures give in this table are takenfrom Bedford, Bonnier, Mass, and Pavese (2).8.2.2 Magnetic Transition Standards.NOTE 6Materials with known magnetic transitions determined withhigh precision are required (3). For sources of materials of known orcertified Curie tr
42、ansition temperatures, contact the ASTM InformationCenter. The values for Curie transition temperatures differ from lot to lotof the material. Curie point temperatures given in the table were obtainedfrom Refs. (5 ).9. Procedure AMelting Point Standard Test forHorizontal Balance Types9.1 Positioning
43、 of the Temperature SensorIf the systememploys a temperature sensor that is movable, it shall belocated as close to the specimen as possible without touchingit or the balance pan. In addition, it must be located in exactlythe same position during calibrations as used during analyticaldeterminations.
44、NOTE 7This position may be inside or outside the balance pan.9.2 Action-Reaction Procedure:9.2.1 Flatten one end of a fine platinum wire (approximately0.34- mm diameter and 2 cm in length), and spot weld it to theoutside of a specimen container as shown in Fig. 2. Carefullybend the wire into a U sha
45、pe so that the cantilevered end islocated in the center of the specimen container.9.2.2 Suspend this specimen container from the balancemechanism so that it hangs freely, and locate the temperaturesensor as outlined in 9.1.9.2.3 Bend a 5-mm length (0.25-mm diameter) of the wiretemperature standard i
46、nto a sigmoid shape, and suspend it fromthe end of the platinum wire in the middle of the specimencontainer.NOTE 8The selection of wire standard depends on the part of thetemperature axis that is to be calibrated. Two or more standards may berun consecutively to enable one to obtain a calibration cu
47、rve.9.2.4 Close the balance assembly, and purge the system withthe desired atmosphere at the selected rate. Select the appro-priate heating rate.9.2.5 Zero the balance and the recorder.9.2.6 Open the system and carefully suspend a platinummass of approximately 50 mg from the end of the wirestandard.
48、NOTE 9This mass can be prepared by tightly winding approximately50 mm of 0.25- mm diameter platinum wire and distending one loop of thewire to provide a convenient connecting loop.9.2.6.1 Close the system.9.2.7 For analog systems using a chart recorder, adjust they-axis pen recorder control sensitiv
49、ity so that the pen is locatedabout the middle of the chart paper.9.2.8 Rapidly heat the system to 50 C below the theoreticalmelting temperature, and allow the system to equilibrate for 5min. Then heat at the selected programmed rate up through themelting temperature of the standard. When the standard melts,the platinum mass falls into the specimen boat or pan. Thisproduces an action-reaction blip on the recorded thermal curvewithout any mass loss. A typical thermal curve is shown in Fig.3.NOTE 10The recorder action is fast and must ordinarily be observ
