Furnace oxidation testing

For comparison, isothermal and cyclic furnace oxidation tests were carried out using the same temperatures and durations as used in the resistance heating tests. These tests were either performed isothermally in a microbalance (SETERAM) in synthetic air or in a conventional resistance heated vertical tube furnace in laboratory air. In the latter tests each cycle consisted of 300 s heating and 900 s cooling. The test specimens used in the furnace tests were coupons of 20 x 5 mm in size which were cut from the 50 pm thick foils. 

When this is done, the calcium hydroxide is included in the melting furnace slag, and the unspent calcium carbide is either used or oxidized in the melting furnace. Little testing has been done to determine the actual fate of the sulfur. Most of it may be included in the slag, but it may also be emitted to the air as sulfur dioxide, or, for foundries with wet emission control systems, it may be dissolved in the water. 

E. Metcalfe, A.R. Thomas, and M.K. Patel, The thermo-oxidative degradation of PTFE in the NBS cup furnace toxicity test, Fire and Materials, 15, 53-58, 1991. 

Specimens with the dimensions of 10 X 1.5 X 1 mm were cut from cast rods and were ground with SiC paper to a 4000 grit surface finish. Before the oxidation tests the samples were cleaned ultrasonically in ethanol. Two kinds of oxidation experiments were carried out isothermal exposure tests at temperatures of 800 to 1000°C for 0.5 h up to 4 h and continuous mass change measurements at 900°C, both in laboratory air. To ensure rapid heating up the exposure tests were started by introducing the samples directly into the hot furnace. The same test conditions were used for the continuous thermogravimetric measurements by raising the hot furnace around the specimen chamber. 

After being cut and ground into 5mmx2mmx20mm specimens, a SiC coating of -lOpm thickness was deposited to isolate the sample cross-sections from the air for oxidation. Oxidation tests were performed in a muffle furnace. The specimens were pushed into the furnace at 1000°C and then taken out quickly to weigh the mass after each 2h oxidation. 

In an effort to bridge the gap between furnace oxidation studies and arcjet oxidation tests, ManLabs performed a series offumace studies on UHTCs under various ranges oftime, gas velocity, temperature and pressure. " " " Furnace test conditions covered temperatures between 500°C and 2500°C, times from five minutes to four hours at air flow rates in two regimes, low velocity between 0.3 and 3 m/s and high velocity, between 3 and 75 m/s. Cyclic exposures were also performed for most of the candidates. 

Figure 1 shows the set-up for high-temperature oxidation tests. The test specimen (020x30 mm) was suspended by a nickle-chromium wire inside a vertical alumina tube furnace controlled at a constant temperature. 

Ribbon furnace used for thermal cycle oxidation tests (a) cross-section of novel experimental set-up for ADSEALS tests,... 

Where closed systems are used, the laboratories utilised bottled gas mixtures, and the reported gas flow rates in such cases are summarised in Table 17.10. As with temperature stability, the recommendations developed in the TESTCORR project should be adopted directly for cyclic oxidation testing, i.e. a linear flow rate of 1-10 mm s". Where the tests are carried out in laboratory air in open furnace systems, the atmosphere is static apart from convection effects. 

Furnace design for short dwell thermal cycling oxidation testing. 

In the gas-cooled reactor, reaction.between the coolant and the moderator results in formation of a proportion of carbon monoxide in the atmosphere. This gas can be carburising to nickel-base alloys but the results of tests in which CO2 was allowed to react with graphite in the furnace indicate that the attack on high-nickel alloys is slight, even at moderately high temperatures and is still mainly due to simple oxidation. 

Self-Test M.1B Reduction of 15 kg of iron(III) oxide in a blast furnace produced 8.8 kg of iron. What is the percentage yield of iron ... 

Closed symbols in Fig. 1 show the effect of reaction temperature on ammonia oxidation over CuO by heating with a conventional electric furnace. The reaction started at about 400 K and the conversion of NH3 became 1 at temperatures higher than 500 K. Fig. 1 also indicates that selectivity to N2 was high at low temperatures but it decreased as the temperature increased. Both N2O and NO increased instead of N2, except at 623 K, at which N2O decreases. NO was detected above 583 K, and it monotonously increased by the temperature. High reaction temperature seems to tend deeper oxidation to NOx. Considering that oxidation of N2 to N2O and NO is difficult in the tested temperature range. 

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