| The International Thermonuclear Experimental Reactor(ITER)program was initiated in 1985.ITER is an important international cooperative project aimed at solving the future energy pro blems of mankind.Plasma facing materials(PFMs)in nuclear fusion energy devices are subjected to multiple effects such as particles,light and heat,so the selection of materials is very strict.Tungsten is considered the best choice for PFMS because of its high melting point,high thermal conductivity,low sputtering rate(which minimizes the production of impurities)and low tritium retention rate.However,tungsten is prone to oxidation,and if a failure occurred in the fusion energy plant,exposing tu ngsten to oxidation would be a serious problem.Therefore,it is of great significance to study the oxidation behavior of tungsten.In this paper,the oxidation behavior of pure tungsten prepared by chemical vapor deposition(CVD)was investigated.Because the metal platinum has good oxidation resistance,and the thermal expansion coefficient of the same order of magnitude as the metal tungsten.The metal platinum was chosen as an oxidation resistant coating.Platinum coating was prepared on pure tungsten s urface and the oxidation resistance of platinum coating was studied.This provides experimental and theoretical basis for the oxidation of pure tungsten.The specific research contents of this paper are as follows:(1)The oxidation behavior of CVD pure tungsten adopts the constant temperature oxidation method.CVD pure tungsten oxidizes at 600?,and its oxidation behavior follows a parabolic rule.In the initial stage of oxidation,the black outer surface oxide film is W18O49.With the increase of time and temperature,the yellow oxide film on the outer surface was observed to be WO 3.At 1000?,the oxidation behavior of CVD pure tungsten deviated from the parabolic rule and appeared destructive oxidation.The effect of grain size on the oxidation behavior of pure tungsten is studied.It is found that fine grain reduces the oxidation rate of pure tungsten and has a positive effect on the oxidation behavior of pure tungsten.(2)Platinum coating was prepared by means of coating sintering by means of chloroplatinic acid decomposition/platinum paste method.In the first step,chloroplatinic acid decomposition method was used to form the first layer of platinum coating by sintering at 800?,holding for 30min and in argon a tmosphere.In the second step,a second layer of platinum coating was sintered under the condition of850?,holding for 15min and air.The smooth and smooth platinum coating without tungsten oxide was successfully prepared on pure tungsten surface of CVD b y chloroplatinic acid decomposition/platinum paste method.(3)By using the cyclic oxidation method,the oxidation behavior of CVD pure tungsten matrix at 600?,700?and 800?follows a linear rule.After being oxidized at 600?for 9h,the oxidation gain is 2.2173mg/cm2,and the oxidation rate constant is 0.18237mg/cm2/h.After oxidation at 700?for 9h,the oxidation weight gain is 7.6278mg/cm2,and the oxidation rate constant is 0.65932mg/cm2/h.After oxidation at 800?for 9h,the oxidation weight gain is 57.3405mg/cm2,and the oxidation rate constant is 5.92197mg/cm2/h.(4)Platinum coating was prepared on the surface of CVD pure tungsten matrix by chloroplatinic acid decomposition/platinum paste method.The oxidation weight gain of platinum coating at 600?for 9h is 65.16%lower than that of CVD pure tungsten matrix.The oxidation weight gain of platinum coating at 700?for 9h is18.98%lower than that of CVD pure tungsten matrix.The oxidation weight ga in of platinum coating at 800?for 9h is 21.52%lower than that of CVD pure tungsten matrix.When the oxidation temperature of PVD pure tungsten coated with Pt is 600?,the oxidation weight gain is reduced to some extent,and the platinum coating shows oxidation resistance. |
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