I know that ruthenium is very challenging to work with, with the gas
absorption problems, brittleness and so on. However, I have seen
alot of older literature (granted patents,etc.) that indicates that
it previously was used for making fountain pen tips and so on very
often. If you can make alloys that have 75% or more ruthenium in
them for fountain tips, why can’t you make those same alloys work in
jewelry?
Is it a matter of just psychological preference in that metals like
Ru and Os are considered to be “useless” by the jewelry trade? Or is
it just that the buying public is ignorant of the lesser known
platinum group metals?
Maybe it would take an unlikely situation of supply problems with
the other platinum group metals and continuing availability of
ruthenium (similar to the “strategic use” issue durin WWII for
palladium) for that ever to happen.
How about for starters it has a melting temp 1000F greater than
platinum! And the pure metal has a hardness of 220 HV comparable to
the hard nickel white golds. Then there is the problem that it
readily oxidizes and that oxide is toxic and unstable to the point
it is explosive and the metal stains human skin. There may be a few
more reasons but those are a few good ones
I know forms of the Ruthenium oxides are toxic, but they do not
appreciably form in any sizable quantities until about 800C is
reached from the technical papers I have read. However, becuase of
the reaction, that is why they use a cover gas and induction melting
just like for Pd. The metal is actually very inert against many
substances. It doesnt react very vigrously at all with aqua regia
unless heated to fairly high temperatures. Even gold is more reactive
to aqua regia than Ru. I dont think the metal is nearly as bad as
osmium, which is the other predominantly close-packed hexagonal PGM.
If it is really that bad, why ever use it for ANY purpose in any
amount? Its in many of the Pd and Pt materials out there as well as
in some of the gold alloys in levels commonly up to 5%.
All I am saying is that no one seems to be even interested to even
try studying it seriously. It is simply written off as something to
be used in tiny amounts for special applications or for catalysis
and that is that. I know people who still consider palladium to be
inferior in many ways to platinum and the other PGM. Pd is more
reactive than any of the other PGMs and some of its salts are also
toxic. Pd reacts slowly with many single mineral acids even at lower
temperatures, and it is the metallic “Hindenburg” of metals. Yet now
it is becoming accepted in jewelry quite in a quite widespread way.
Maybe because Pd looks good, has low density, and is far less than
the cost of platinum?
I am a chemist by trade. I have kind of learned the hard way that
the jewelry trade can be rather conservative about new things often,
and I do respect that. If the older materials and methods have
worked to this point, why change? I can still experiment on my own,
and if I find out anything of interest, I will let people know.
I believe the use of ruthenium in fountain pens was strictly limited
to electro-formed end tips on 14k or 18k. I use the expression
electro-formed here because, though the ruthenium is plated to an
already formed tip, the plating process is more complicated than
normal and quit thick on quality pens. Pen makers like Mont Blanc
and other have their proprietary methods.
I know forms of the Ruthenium oxides are toxic, but they do not
appreciably form in any sizable quantities until about 800C is
reached from the technical papers I have read. However, becuase of
the reaction, that is why they use a cover gas and induction
melting just like for Pd.
At 800C you are not even getting it warm. To be a successful jewelry
metal must be workable in the shop. With a melting point of 4190F
you are not going to have standard refractory materials that can be
used for casting investment or crucibles. Alumina and silica are both
molten at the melting point of Ru, zirconium is way to unstable for
repeated use at those temperatures and I would be willing to bet
metal crucible reactions would be a problem as well with the Ru
picking up either the oxides or possibly even the metals themselves
from the refractory. The only commercial metal fabrication processes
for Ruthenium are powder metallurgy based. It can be also be
electroplated and vacuum sputter deposited. Other than that it is not
worked as a pure metal.
The metal is actually very inert against many substances. It doesnt
react very vigrously at all with aqua regia unless heated to fairly
high temperatures.
Well I am not a chemist but there are a large number of ruthenium
compounds so I am not certain how it can be called inert. It is acid
resistant but to me inert means non reactive and I do not believe it
qualifies.
I dont think the metal is nearly as bad as osmium, which is the
other predominantly close-packed hexagonal PGM.
for jewelry use, How are you going to sell jewelry that stains the
skin?
I am a chemist by trade. I have kind of learned the hard way that
the jewelry trade can be rather conservative about new things
often, and I do respect that. If the older materials and methods
have worked to this point, why change? I can still experiment on my
own, and if I find out anything of interest, I will let people
know.
It has nothing to do with being conservative there is no reasonable
way to make anything with the metal. Yes if you have the tools for
powder metallurgy you can sinter it. You will need a very expensive
special furnace that can both reach very high temperatures and
provide an inert atmosphere along with other specialty tools.
I know people who still consider palladium to be inferior in many
ways to platinum
Seech, Im one of those people – I wont go into why because its just
opinion, really. On some level the answer to your questions is, “If
it aint broke, why fix it?” Whats wrong with gold? Thats not to say
that other materials are bad, or the exploration of them is bad, but
especially on a commercial level its unneccessary. The trend towards
palladium is fueled by one thing and one thing only: Money. It does
make a fine alloy with gold, though. You are a chemist, so you surely
know that osmium oxides arent just poisonous, they are
extraordinarily so, and ruthenium isnt so far behind. The choice of a
metal is based on many factors, safety and comfort being in the front
on the line. Much of what you are asking is a matter of novelty -
what real properties do the metals in question have that make them a
truly better choice that existing metals?
Please see in the google patent search the following regarding
workable Ru alloys:
patent 3194657 - process for making workable ruthenium and product
thereof
patent 2328580 - ruthenium alloy pen point
patent 2206615 - tip for small bases
patent 2093502 - pen nib
These are obviously older patents, but still illustrate the work
done with Ru. Another application I am told they use Ru alloys for
now is for high-price sunglasses.
Also Platnimum Metals Review, 1965, 9, (2), 51-56. Discusses the
oxidation of ruthenium and osmium in detail. They are not believed
to form solid oxide films in an oxidizing atmosphere, but can exist
as solids. Figure 1 on page 53 is very important, showing the
partial pressure of the oxides.
A patent does not mean that the invention works. The patent office
only assess the originality of the patent claim not whether or not
it works. There are many unworkable or unusable patents.
Did you read the patent 3194657 - “process for making workable
ruthenium and product thereof” ? By workable he means hot working at
temperatures in excess of 1200C. This is not workable in terms of
jewelry making.
There are lab and industrial processes that can allow for the
processing of difficult to work elements. However that does not make
them suitable for jewelry use. I have had alloys made by the same
equipment referred to in the 3194657 patent. It costs about $300 for
one button of about an inch in diameter and 1/4 in thick to be
melted in the machine. Maybe in aerospace or medical uses you can pay
for the costs of these types of processing but not in the jewelry
business.