3. สารเคมี (Chemical Substance)
สารเคมี หมายถึง ...
สารบริสุทธิ์ (A chemical substance is any pure,
unmixed material substance with a definite
chemical composition)
ตองการคําอธิบายเพิ่มเติม
ในทางเคมี สารบริสุทธิ์ ไดแกธาตุหรือ
สารประกอบ
41. กรณีศึกษา 1 - การสังเคราะหเพชร
Could slippery, soft graphite be transformed
into diamond - the hardest and most brilliant
material on earth?
42. กรณีศึกษา 1 - การสังเคราะหเพชร
How nature makes diamond ?
• diamonds are found inside extinct
volcanoes, embedded in a mineral called
kimberlite
• geologists believed they were formed in
the molten ooze of the earth's mantle - T = 1100 - 1600 o C
more than 100 miles below the surface. P > 1,000,000 psi
• But how long did it take nature to make a
diamond?
1,000,000,000 years ?
43. กรณีศึกษา 1 - การสังเคราะหเพชร
1951 GE started project Superpressure to make diamonds
1955
GE spent millions on diamond
presses capable of focusing huge
pressures and temperatures on
the graphite capsule, but still the
graphite wouldn't turn to diamond
Many presses were spent. No
diamonds is formed Project was in
trouble. The team had to find a
new way or the project would be
cancelled
http://www.pbs.org/wgbh/nova/transcripts/2703diamond.html
44. กรณีศึกษา 1 - การสังเคราะหเพชร
Some hints:
1955 1. Why ice is crytalline why water
is not?
2. Why tiny crystal of diamond
found in meteorites is
surrounded by troilite?
Troillite was added to graphite. After
heating to about 4600 oC and 1 million
psi small crystal of diamond was formed
Today, 90% of all diamonds used in
Industry are manufactured
45. Sciences and Business
1970 Can gem-quality diamond be
produced by this method?
GE was able to grow larger
diamonds
but they cost more to produce
than the price of natural
diamonds.
46. Sciences and Business
How De Beers keeps the market value of diamond business
Control the
Sale 4,000 million
release
dollars worth of
rough diamond
4,000 million From diamond
mines 1 rough gem
dollars worth of
rough diamond Africa, Siberia,
reserve 250 tons of rock
Canada
47. Sciences and Business
What would be happen to the business
if scientists can produce perfect gem-
quality synthetic diamonds?
48. กรณีศึกษา 1 - การสังเคราะหเพชร
1995 Synthetic diamond was not perfect
1. metal inclusion
2. yellow color
1. A process of crystallization must
be controlled: the press must be
redesigned.
2. Aluminium was put in a growing
cell.
Could sciences compete with nature ?
Find more at
http://www.pbs.org/wgbh/nova/transcripts/2703diamond.html