1、 ISO 2017 Nanotechnologies Characterization of multiwall carbon nanotubes Mesoscopic shape factors Nanotechnologies Caractrisation des nanotubes en carbone multicouches Facteurs de forme msoscopique TECHNICAL SPECIFICATION ISO/TS 11888 Reference number ISO/TS 11888:2017(E) Second edition 2017-07 ISO
2、/TS 11888:2017(E)ii ISO 2017 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2017, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photo
3、copying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Ch. de Blandonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22
4、 749 01 11 Fax +41 22 749 09 47 copyrightiso.org www.iso.org ISO/TS 11888:2017(E)Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 T erms, definitions and abbr e viat ed t erms 1 3.1 Terms and definitions . 1 3.2 Abbreviated terms . 3 4 Sample preparation methods . 3 4.1 Ball mill cu
5、tting. 3 4.2 Dispersion method 3 4.3 Sample preparation for SEM . 3 4.4 Alternative sample preparation method 3 5 Experimental procedure 4 5.1 Measurements of the SBPL using SEM . 4 5.1.1 SEM 4 5.1.2 Measurement methods for the SBPL 4 5.2 Measuring inner and outer diameters of MWCNTs using TEM . 5 6
6、 Test report . 5 Annex A (normative) F ormulae for t erms and definitions in Clause 2, Annex B, Annex C and Annex D 6 Annex B (informative) Viscometry 11 Annex C (informative) Dynamic light scattering and depolarized dynamic light scattering 12 Annex D (informative) Case study and reports .14 Biblio
7、graphy .18 ISO 2017 All rights reserved iii Contents Page ISO/TS 11888:2017(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through I
8、SO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates
9、closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval crite
10、ria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives). Attention is drawn to the possibility that some of the elements of this document may be the subject
11、 of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www .iso .org/ patents). Any trad
12、e name used in this document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adhere
13、nce to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: w w w . i s o .org/ iso/ foreword .html. This document was prepared by Technical Committee ISO/TC 229, Nanotechnologies. This second edition cancels and replaces the first edition (IS
14、O/TS 11888:2011), which has been technically revised.iv ISO 2017 All rights reserved ISO/TS 11888:2017(E) Introduction Multiwall carbon nanotubes (MWCNTs) synthesized by chemical vapour deposition (CVD) are of growing interest for use in polymer composites and conductive coatings. In many cases, MWC
15、NTs synthesized by CVD have static (permanent) bend points randomly distributed along their axis. Physical and chemical properties of mass-produced MWCNTs are strongly dependent on the statistical distribution of mesoscopic shapes and sizes of the individual MWCNT (see ISO/TS 80004-3), among other p
16、arameters, that comprise the product. 46It is therefore crucial to characterize the mesoscopic shapes of MWCNTs in order to ensure that the final properties are reproducible for use in a wide range of materials, including composites and other dispersions, as well as for Environment, Health and Safet
17、y (EHS) issues. 7 This document provides methods for the characterization of mesoscopic shape factors of MWCNTs, including sample preparation procedures. In particular, it provides a statistical method for characterizing MWCNTs produced by the CVD method. During MWCNT synthesis, axial structures are
18、 not perfectly linear but include static bend points. This document provides methods for determining a statistical quantity, representing a maximum straight length that is not deformed by permanent bending called the “static bending persistence length” (SBPL). The SBPL gives information regarding th
19、e relationship between the MWCNT mesoscopic shape and size. If two MWCNTs of equal length have different SBPLs, their overall sizes (e.g. radius of gyration or an equivalent diameter such as a hydrodynamic diameter) will also be different from one another. In practical applications, the variation in
20、 SBPL affects both chemical reactivity and physical properties. 456 Electrical conductivity and dimensional stability of MWCNT-polymer compounds are also strongly dependent on the SBPL of the MWCNT used to make them. 456Various properties might be affected by SBPL, including electrical percolation t
21、hreshold, 68toxicity, 7thermal conductivity, 9rheological property 10and field emission property. 11SBPL could be useful for estimating the loading of a MWCNT-polymer matrix to achieve electrical conductivity (percolation limit) and should also assist with modelling the mechanical properties of MWCN
22、T-polymer composites with different loadings. Prior to commencing any work, users are advised to familiarize themselves with the latest guidance on handling and disposal of MWCNTs, particularly in relation to the use of appropriate personal protective equipment. Information on current practices is a
23、vailable in ISO/TR 12885. ISO 2017 All rights reserved v Nanotechnologies Characterization of multiwall carbon nanotubes Mesoscopic shape factors 1 Scope This document describes methods for the characterization of mesoscopic shape factors of multiwall carbon nanotubes (MWCNTs). Techniques employed i
24、nclude scanning electron microscopy (SEM), transmission electron microscopy (TEM), viscometry, and light scattering analysis. This document also includes additional terms needed to define the characterization of static bending persistence length (SBPL). Measurement methods are given for the evaluati
25、on of SBPL, which generally varies from several tens of nanometres to several hundred micrometres. Well-established concepts and mathematical expressions, analogous to polymer physics, are utilized for the definition of mesoscopic shape factors of MWCNTs. 2 Normative references There are no normativ
26、e references in this document. 3 T erms, d efinitions and abbr e viat ed t erms 3.1 T erms and definiti ons For the purposes of this document, the following terms, definitions and abbreviated terms apply. ISO and IEC maintain terminological databases for use in standardization at the following addre
27、sses: ISO Online browsing platform: available at h t t p :/ www .iso .org/ obp IEC Electropedia: available at h t t p :/ www .electropedia .org/ NOTE Formulae for some of these terms and definitions are given in Annex A. 3.1.1 mesoscopic shape description of shape at the observation scale for an ind
28、ividual multiwall carbon nanotube (MWCNT) Note 1 to entry: Mesoscopic shape factors describe the average size and shape of individual MWCNTs, while “macroscopic” describes the shape and size of MWCNT aggregates or agglomerates. “Atomic scale resolution” describes the shape of an MWCNT at the atomic
29、level (see Figure 1). Note 2 to entry: See Reference 4. TECHNICAL SPECIFICATION ISO/TS 11888:2017(E) ISO 2017 All rights reserved 1 ISO/TS 11888:2017(E) a) Macroscopic (aggregates) b) Mesoscopic (individual) c) Atomic scale resolution NOTE SOURCE: 2010 ACS Figure 1 Shape of MWCNTs at various scales
30、3.1.2 regular shape MWCNTs property of having a regular pattern along the tube axis Note 1 to entry: Correlations in the direction of the tangent show a periodical shape for MWCNTs of regular shape. Both straight and coil-shaped MWCNTs are typically classified as MWCNTs of regular shape. 3.1.3 rando
31、m shape MWCNTs property of having static or permanent bend points distributed randomly (Gaussian) along their tube axis 3.1.4 static bending persistence length SBPL l maximum straight length without static bending 3.1.5 contour length L total length of an MWCNT along its axis 3.1.6 weighted average
32、contour length L w average of contour length which is assigned a weight 3.1.7 end-to-end distance R straight distance between the two ends of an MWCNT 3.1.8 bending ratio D b ratio between mean-squared end-to-end distance and squared contour length2 ISO 2017 All rights reserved ISO/TS 11888:2017(E)
33、3.1.9 intrinsic viscosity description of an MWCNTs contribution to the viscosity of MWCNT dispersion 3.2 Abbreviated terms CVD chemical vapour deposition DDLS depolarized dynamic light scattering DLS dynamic light scattering DMF dimethylformamide SBPL static bending persistence length SEM scanning e
34、lectron microscopy TEM transmission electron microscopy 4 Sample preparation methods 4.1 Ball mill cutting Place 200 mg of MWCNTs and 20 ml of ethanol and zirconia balls (5,2 mm) into a zirconia pot (150 ml) and ball mill 500 r/min for 2 h. Pour the ball-milled MWCNT dispersion from the zirconia pot
35、 into a 50 ml conical centrifuge tube at 5 000 r/min. Centrifuge the ball-milled MWCNT dispersion to separate the MWCNTs and then freeze-dry the separated MWCNTs for 24 h. Dry the MWCNTs at 300 C for 30 min while exposed to air to remove unwanted volatile components. Grind the dried MWCNTs by pestle
36、 and mortar. NOTE When higher r/min and longer ball-milling time are applied than those described here, the structure of MWCNTs might be destroyed. 4.2 Dispersion method Disperse 0,02 g of milled MWCNTs in 200 ml dimethylformamide (DMF) using an ultra-sonicator at 40 W for 3 h. Pour the MWCNT disper
37、sion into a 50 ml conical centrifuge tube and centrifuge at 3 000 r/min for 30 min. Filter the dispersion with a paper filter (pore size 10 m) to eliminate any non- dispersed parts that might remain. NOTE DMF is the best solvent for CNT dispersion (see Reference 4,5). 4.3 Sample preparation for SEM
38、Use additional DMF to dilute the MWCNT dispersion to 10. Drop 1 ml of the 10 dispersion onto a 0,02 m ceramic filter and filter it under vacuum. Dry the ceramic filter, containing the MWCNTs, at 60 C for 24 h. 4.4 Alternative sample preparation method Following the methods in order (4.1, 4.2 and 4.3
39、) is recommended for Method 1 (see 5.1.2.1) and Method 3 (see 5.1.2.3). As-synthesized MWCNTs can be used for Method 2 (see 5.1.2.2). ISO 2017 All rights reserved 3 ISO/TS 11888:2017(E) 5 Experimental procedure 5.1 Measurements of the SBPL using SEM 5.1.1 SEM 5.1.1.1 General High-resolution SEM imag
40、es allow closely spaced features to be examined at a high magnification. 5.1.1.2 Preparing SEM images Cut the ceramic filter containing the MWCNTs into small pieces and place on a sample holder, to which conductive tape is applied. Dry the sample holder under vacuum at 40 C for 1 h. Sputter coat the
41、 dried sample with iridium for 1 min. Gold, platinum, or carbon may be used if an iridium source is not available. Take three or more SEM images at a magnification of 10 000. Take three or more representative high- resolution images at 20 000. This procedure is recommended for Method 1 (5.1.2.1) and
42、 Method 3 (5.1.2.3). Alternatively, place an as-synthesized MWCNT on a sample holder, to which conductive tape is applied. Dry the sample holder under vacuum at 40 C for 1 h. Sputter coat the dried sample with iridium for 1 min. Gold or platinum may be used if an iridium source is not available. Tak
43、e three or more SEM images at a magnification of 10 000. Take three or more representative high-resolution images at 20 000. This procedure is recommended for Method 2 (see 5.1.2.2). NOTE 1 Sputter coating for more than 1 min can cause a slight change in the bending of the MWCNT. 5.1.2 Measurement m
44、ethods for the SBPL 5.1.2.1 Method 1 From the SEM images, determine the contour lengths and end-to-end distances of at least 100 different individual MWCNTs. Classify the data using an interval of 100 nm for contour length. For each contour length range, calculate the mean-squared end-to-end distanc
45、e. Obtain the bending ratio for each contour length range by dividing the mean-squared end-to-end distance by the squared average contour length see Formula (A.3). When the contour length is greater than 1m, the value of contour length from the top view image may be underestimated by up to 15 %. 1Wh
46、en more accurate values are required, measure the contour length and end-to-end distance using a 3D image, which can be obtained by several side view images. 1 Plot the bending ratio with respect to the reciprocal contour length, measure the gradient and determine the SBPL using Formula (A.4). When
47、the linear relationship between bending ratio and reciprocal contour length reaches the asymptotic limit, the resulting slope equals two times the SBPL. NOTE 1 For MWCNTs of random shape, the end-to-end distance varies at constant contour length. 1Therefore, various values of end-to-end distance cou
48、ld be measured for each contour length range. The distribution of end- to-end distance of MWCNT is Gaussian for each contour length range when MWCNTs are of random shape. To obtain the mean-squared end-to-end distance, the mean value of the squared end-to-end distance is calculated. NOTE 2 Because w
49、ell-dispersed MWCNTs are filtered prior to SEM imaging, 100 MWCNTs are sufficiently representative of the shape of the MWCNTs in the sample. This is supported by DLS and DDLS measurements as well as intrinsic viscosity measurements. 1An approximate value for the SBPL can be obtained using Method 2 or Method 3.4 ISO 2017 All rights reserved ISO/TS 11888:2017(E) 5.1.2.2 Method 2 Measure the radius of curvature of at least 100 individual tubes from the SEM images of as
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