Page 231 - Manufacturing Engineering and Technology - Kalpakjian, Serope : Schmid, Steven R.

2 I 0 Chapter 8 Cerami cs, Graphite, Diamond, and Nanomaterials: Structure, General Properties, and Applications
Graphite structure zigzag Ohm'
qqqqqqgeeeeeeeeq
%%%%%%%4Q¢qq4¢4’WM~@
0§¢¢¢¢@ppp§§¢¢¢,, ~M
qqhhqhmgffypp, 45
C
Arm hai I” °0°0'0°0°0°0°o°0°0°0°0'0'0‘ 0
:~0000%gggg;g»50
3°3°3°3°3°3°3'3°3°3°3°3°3°¢°3¢!°
00 0000
~q--0,0~q--
0#FUY#ffN#§#f#P#
000000000000
0 000
0000000000000000 N
W
0000000000000000
0
00 00000
00 0000
00
¢¢¢¢p¢¢¢¢¢¢@¢¢¢p
0
¢¢¢¢00¢¢¢0¢¢¢¢¢¢
.0
2”
0 0¢¢¢¢0¢0¢'¢¢¢¢¢0
0
0
0 '
0: ---'- 5510 0.\‘ . . ° Q
|_|_|_|_|_
‘.3§°§3§»§2§¥§2I-:'§°:%‘2:2°2§2§
‘\
.
|000099&99&9h&@@
°2°3°3°3°€°3°3°3°2°3'2°3°3922¢ ¢ , M /_ ff/
00000000 000\000

\
°
° : :-2-2-2-°-2
0 N°»:~:-:»:-2-Q-2-.-
\
|00000000\000000
000000000\000000
‘Q |-qqqqq~`q00qy~
°3°3°3°3°€34 3°$‘3°3°3°3°¥°3 3
°
°
°
~
0 000000 \00000
‘
0000000000000000
O
Q Q
\
|000000000¢000m,n
rH%%%%%%%%%%%h4%% MM
,%%%%%%%%%%*%%%%
0000000000000000
. :»:»:-:-:»:»:-:-:»:»:¥:»:-:-:-
ggggqqqqqqqqqqqq
qqqqqqqqqqqqqqqq
FIGURE 8.4 Forms of carbon nanotubes: armchair, zigzag, and chiral. Armchair nanotubes
are noteworthy for their high electrical conductivity, whereas zigzag and chiral nanotubes are
semiconductors.
8.7 Diamond
Diamond is a principal form of carbon with a covalently bonded structure. It is the
hardest substance known (7000 to 8000 HK). However, it is brittle and begins to
decompose in air at about 700°C, but it resists higher temperatures in nonoxidizing
environments.
Synthetic (also called industrial) diamond was first made in 1955. A common
method of manufacturing it is to subject graphite to a hydrostatic pressure of
14 GPa and a temperature of 3000°C. Synthetic diamond is identical to natural dia-
mond. It has superior properties because of its lack of impurities and is used exten-
sively in industrial applications. Synthetic diamond is available in various sizes and
shapes; for abrasive machining, the most common grit size is 0.01 mm in diameter.
Diamond-like carbon also has been developed and is used as a diamond film coat-
ing, as described in Section 34.13. Diamond particles also can be coated with nick-
el, copper, or titanium for improved performance in grinding operations.
In addition to its use in jewelry, gem-quality synthetic diamond has possible
applications as heat sinks for computers, in telecommunications and integrated-
circuit industries, and as windows for high-power lasers. Its electrical conductivity is
50 times higher than that of natural diamond, and it is 10 times more resistant to
laser damage.
Because of its favorable characteristics, diamond has numerous important
applications, such as the following:
° Cutting-tool materials, as a single crystal or in polycrystalline form
° Abrasives in grinding wheels, for grinding hard materials
° Dressing of grinding wheels (i.e., sharpening of the abrasive grains)
° Dies for drawing wire less than 0.06 mm in diameter
° Coatings for cutting tools and dies.
8.8 Nanomaterials
Important developments have taken place in the production of materials as particles,
fibers, wire, tube, films, and composites having features that are typically on the
order of 1 nm to up to 100 nm. First investigated in the early 1980s and generally
called nanomaterials or nanostructured, nanocrystalline, or nanop/Jase materials,