Page 354 - Book Hosokawa Nanoparticle Technology Handbook
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FUNDAMENTALS                           CH. 6 EVALUATION METHODS FOR PROPERTIES OF NANOSTRUCTURED BODY
                  In nanomaterials, internal friction measurement can be  (see Fig. 6.2.10). The average value of the diagonal
                  required for expecting to minimize the vibration of the  lengths is applied as d, as we have two different diag-
                  materials or components with adding secondary  onal lengths on one indent. For the unit expressing the
                                                                                     –2
                  nanophase. For internal friction measurement, we have  Vickers hardness, kgf mm (force by kgf and area by
                                                                    2
                  some techniques such as measuring the dumping of the  mm ) was used, but recently we can see the expression
                  vibration or the sharpness of the resonance of the vibra-  with SI units, hardness in GPa.
                  tion of the materials. Each technique can be applied at a  In the measurement of brittle materials, cracks can
                  certain vibration frequency, so, we can choose the tech-  be generated from the corner of the indents. For pre-
                  nique considering the frequency for the applications.  cise measurement, we must keep enough distance on
                    Hardness is the parameter expressing the value for  every indent for avoiding the influence of the cracks.
                  deformation of the materials with concentrated force  Fig. 6.2.10 shows the guideline for the distance of the
                  on the surface. Vickers hardness test [10,11] is one of  indents, recommended in the testing on ceramic
                  the most common technique for the measurement of  materials.
                  hardness, which uses the diamond indenter, and meas-  For the measurement on thin films, it is antici-
                  ures the indent size after applying force on the surface.  pated that the properties of the substrate may affect
                    On Vickers hardness test, diamond with pyramid  the hardness measurement results. It is said that if
                  shape is used for forming indents, and the tip of the  the film thickness is more than three times of the
                  indenter is put and the force is applied on the surface  indent depth, the hardness can be measured with no
                  of the materials. The following equation is used for  influence by the substrate. In the case of  Vickers
                  calculating the Vickers hardness value.        hardness, the indentation depth, h, and the area of
                                                                 the indent, S, has the following relation. The inden-
                                       1 8544 P
                                        .
                                 H                      (6.2.6)  tation depth can be calculated from the result of the
                                   V
                                         d  2                    indent area measurement.
                  where,  H is Vickers  hardness,  P the applied force
                         V
                  and  d the diagonal length of the formed indents                S   24.5 h 2         (6.2.7)
                                                                                        c
                                                       d





                                 Specimen edge








                                            L 2                     L 1





                                           L 1   4d and 5c
                                              2.5d and 5c
                                           L 2
                                           d: diagonal length of indent
                                           c: length form center of indent to end of crack
                                            : length between center of indents
                                           L 1
                                            : length from center of indent to specimen edge
                                           L 2
                  Figure 6.2.10
                  Indentation on Vickers hardness test and the recommended distance of indents.

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