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The Turner-Sclerometer test consists of measuring the amount of load required to make a scratch. [1] [2] In test a weighted diamond point is drawn, once forward and once backward, over the smooth surface of the material to be tested. The hardness number is the weight in grams required to produce a standard scratch.
Scratch hardness test or scratch test refers to any of a number of methods of measuring scratch hardness. Resistance to abrasion is less affected by surface variations than indentation methods. Scratch hardness is measured with a sclerometer. [1] Attempting to scratch a surface to test a material is a very old technique. [2]
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In the recent past, the so-called "window pane test" was commonly thought to be an assured method of identifying diamond. It is a potentially destructive test wherein a suspect diamond gemstone is scraped against a pane of glass, with a positive result being a scratch on the glass and none on the gemstone.
In microindentation hardness testing, a diamond indenter of specific geometry is impressed into the surface of the test specimen using a known applied force (commonly called a "load" or "test load") of 1 to 1000 gf. Microindentation tests typically have forces of 2 N (roughly 200 gf) and produce indentations of about 50 μm. Due to their ...
A superhard material is not necessarily "supertough". For example, the fracture toughness of diamond is about 7–10 MPa·m 1/2, [16] [17] which is high compared to other gemstones and ceramic materials, but poor compared to many metals and alloys – common steels and aluminium alloys have the toughness values at least 5 times higher. [18]
Vickers test scheme The pyramidal diamond indenter of a Vickers hardness tester An indentation left in case-hardened steel after a Vickers hardness test. The difference in length of both diagonals and the illumination gradient, are both classic indications of an out-of-level sample.
Diamond is a good electrical insulator, having a resistivity of 100 GΩ⋅m to 1 EΩ⋅m [32] (1.0 × 10 11 – 1.0 × 10 18 Ω⋅m), and is famous for its wide bandgap of 5.47 eV. High carrier mobilities [ 33 ] and high electric breakdown field [ 34 ] at room temperature are also important characteristics of diamond.