High-speed (subsecond) measurement of heat capacity, electrical resistivity, and thermal radiation properties of molybdenum in the range 1900 to 2800 K

Abstract

A tec hniqu e is described for th e hi gh•speed m e~s ure m e nt of heat capacit y, elec trical res istivit y, he mi s phe rical total and norm al spectral e mitta nces of electri cal condu ctors at high te mpe ra tures (above 1900 K) with milli second resolution. Duration of a n individ ual experim e nt , in which t he s pecim e n is he a ted from r oo m te mperatu re to cl ose to its meltin g po int, is less tha n one second. T e mpera ture m eas ureme nts a re made with a highs peed photoelec tri c pyr ome ter. Quantiti es are recorded by a hi gh•s peed di gita l data acqui s ition sys te m whic h has a resolutio n of ap proximately one pa rt in 8000. T ime resolutio n of th e entire syste m is 0.4 ms. Results on th e abo ve prope rties of molybd enum in th e te mpe rature ra nge 1900 to 2800 K are re ported a nd are co mpared with th ose in the literature. Estimated inacc uracy of measl're d pro pe rti es in the a bove te mperature ra nge is: 2 to 3 per cent for heat capacity, 0.5 pe rce nt fo r electrical res isti vit y, 3 perce nt fo r he mi s ph e ric al total emittance and 2 percent for no rm al spectral e mittance. Key word s: El ectrical res isti vi ty; e mitta nce; heat ca pac ity; hi g h-s peed meas ure me nts; high tem pe ratu re; mo lybde num ; th e rm a l radi ati on pro pe rties; the rm od yna mics.

High-speed (subsecond) measurement of heat capacity, electrical resistivity, and thermal radiation properties of tungsten in the range 2000 to 3600 K

“…calibrated before and after the entire set of expenments. The details of the calibration procedures are given in an earlier publication [2].…”

“…U.S. Air Force Offi ce of Sci en Ii fie Hesea rch und e r contra ct ISSA -70-0002. 1 Figures in brac ke ts ind icate th e lit e rature refe rences allhe e nd of thi s pape r. of rela tion s for properties e tc., a re give n in earli er publi cations [2,3] in co nn ection with m eas ure me nts on molybdenum and tantalum.…”

Radiance temperature of niobium at its melting point

“…From table 1 (last column) it may be seen that for the "rough" specimens a considerable difference exists between 3 Inacc uracy refers to the estimated total error (random and systematic). This difference in temperature corresponds to a difference in normal spectral emittance ranging from 7 to 14 percent for the four "rough" specimens.…”

“…The cir· cular area viewed by the pyrometer was 0.2 mm in diameter. The recordings of temperature were made with a high·speed digital data acquisition system [3] , which is capable of recording data at the rate of 2400 points per second with a full-scale signal resolution of approximately one part in 8000. Details regarding the construction and operational characteristics of the entire measurement system are given in an earlier publication [4] .…”

“…The details of sources and estimates of errors in high-speed experiments similar to those conducted in this study are given in an earlier publication [3]. Specific items in the error analysis were recomputed whenever the present conditions differed from those in the earlier study_ The imprecision 2 of temperature measurements , during heating as well as melting periods, 2 Imprecision refers to the standard deviation of an individual temperature as computed from the differen ce between the measured value and that from the smooth function obtained by the least squares method.…”