Plasma gun sprays metal onto form where it solidifies to build up part RSPD is carried out in a vacuum chamber. Powdered alloys of most any composition are injected into a plasma spray gun, where they melt instantly in the high-temperature (up to 20,000 °F) plasma stream. Propelled from the gun at high speed, the liquid droplets impact a substrate
and are quenched rapidly at a rate of up to a million degrees Fahrenheit per second. Metal is built up layer by layer to the desired size, shape, and thickness of the fabricated part, and the substrate is then etched or machined away, leaving the spray-formed part. Development work on the technique is being carried out by a research team from GE and Drexel University under contract to the Defense Advanced Research Projects Agency. Following a year-long, $2 million first-phase effort, the Aeronautical Systems division's materials laboratory at Wright-Patterson Air Force Base, Ohio, has awarded the team a new two-year, $3.5 million contract. An advantage claimed for RSPD is that it results in extremely dense, small-grained structures, which potentially have much higher tensile strength and thermal-fatigue resistance than can be achieved with conventional methods. Also, the technique can create composite structures having specific properties at selected locations, such as a turbine blade with a corrosion-resistant alloy for the outer skin and an alloy noted for structural strength for the inner skeleton. D
Claim of toxin use in Persian Gulf war questioned Claims that Iraq has pelted Iranian soldiers with a chemical weapon composed of mustard gas and yellow rain toxins "are premature/' says a U.S. intelligence analyst. His statement vocalizes the "extreme skepticism" of many top officials in the State Department about the claims of a Belgian toxicologist. Several weeks ago, Aubin Heyndrickx, head of the toxicology department at the State University of Ghent and a forensic toxicologist of some renown in Europe, said there was "no doubt" that the Iranians had been exposed to "a mixture of yellow rain and yperite." Yperite, or sulfur mustard gas, is the blistering agent last used in World War I. Heyndrickx has analyzed blood, urine, and feces of Iranian soldiers being treated by Herbert Mandl, a plastic surgeon at the Second Surgical Clinic of the University of Vienna.
Heyndrickx has yet to release data to support his claim. But he says that Mandl told him that Swedish scientists had confirmed his analyses. The Swedes have been treating five Iranian victims, three of whom have died. Johan Santesson, research director of the chemistry division of the Swedish National Defense Research Institute, says no Swedish laboratory has yet confirmed Heyndrickx's findings. Santesson's laboratory has "obtained some samples from Swedish physicians treating Iranian soldiers." Santesson expects results this week; they may be made public. Heyndrickx has told C&EN that the two types of chemical agents are combined in one munition, "in the same bomb." This has been confirmed by Iranian soldiers who have been "interrogated separately and at different u n i v e r s i t i e s , " he says. Santesson says he would expect a
chemical reaction if mustard gas and trichothecenes (yellow rain toxins) were mixed in a unitary munition. Furthermore, "it would be impossible to store the munition for a long period of time," Santesson says. U.S. government scientists, who had considered various combinations of agents but not this specific one, are now studying the chemistry of this peculiar mixture. Santesson says, "It would be surprising if these substances are used together. I see no practical use" for the combination. He is also puzzled by Heyndrickx's finding of mustard gas in body fluids eight to nine days after an alleged attack. "In a water solution and at room temperature, the half-life of mustard gas is 10 to 20 minutes. It hydrolyzes rapidly." Heyndrickx does not report finding hydrolysis products but only the parent compound. Heyndrickx says the mixture of mustard gas and toxins "produces a synergistic effect," which Mandl explains by saying "the patients remain intoxicated longer than one would expect from just mustard gas exposure." Yet only three to four weeks have elapsed since Mandl's patients were gassed, and Santesson says recovery from mustard gas can take up to two months, and if the exposure were very intense, victims can be plagued with chronic effects that last a lifetime. "The effects observed [in the victims] are not inconsistent with exposure to mustard gas, but that is not the same as saying that the Iranians have been exposed to mustard gas," Santesson says. The many unanswered questions have elicited few comments from the U.S. Says Gary Crocker, an intelligence analyst on leave from the State Department, "I just don't think that the evidence that has been presented so far will be accepted at face value. There will be a demand for more evidence. Certainly the business of mycotoxin use is very premature." Some answers may soon be forthcoming. The Swedes and the British have samples and their analyses may yet confirm Heyndrickx's findings. Also, the UN team sent to investigate Iranian allegations has returned to Geneva, and its report is expected this week. D March 26, 1984 C&EN
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