Impact of high temperature on the compression behavior of carbon-bonded alumina filters with functionalized coatings

Compression Behavior of Carbon‐Bonded Alumina Spaghetti Filters at Room and High Temperatures

“…The uncoated foam filters tested by Ranglack-Klemm et al [30] exhibited compressive strength of 100-190 N at 1100 C, whereas the CNT-ANS-and CNT-ANB-coated ones were 100-300 and 130-220 N, respectively. According to a recent study, [29] uncoated foam filters as well as those coated by AC6.3 and alumina had, considering the high scatters, compressive strengths less than %400 N. All these values are significantly lower than the compressive strength of the spaghetti samples tested at 800 C in this study (i.e., 1532 AE 390 N). According to Solarek et al, the compression at maximum force of uncoated Al 2 O 3 -C foam filters at 800 C was %0.19 AE 0.14 mm.…”

“…[29] In comparison, the compressive strength of spaghetti filters tested at 1500 C was higher than 1440 N and, thus, exceeding the foam filters by far. Also, the compression at maximum force (although not recorded due to the protective test interruption) was higher than for the foam filters as the value for uncoated foam filters was no more than 0.7 mm and that for coated foam filters was less than 0.8 mm at 1500 C. [28,29] For Al 2 O 3 -C foam filters, a brittle-to-ductile transition occurred between 1300 and 1400 C. [28,29] According to Solarek et al, such a transition arises from the transformation of the carbonaceous matrix into highly ordered pyrolytic graphite (HOPG) or graphite whiskers as well as thermally activated mechanisms. [28] Therefore, it is not surprising that the Al 2 O 3 -C spaghetti filters with almost the same bulk material composition behaved brittle at room temperature and 800 C, and exhibited ductility at 1500 C.…”

“…Compression tests for cylindrical Al 2 O 3 -C foam filters of %Ø 20 mm  25 mm height at high temperatures were reported previously. [28][29][30] The compositions as well as some parameters and testing conditions of these filters are shown in Table 2. All these filters were prepared through the replica method using ten pores per inch polyurethane foam templates.…”

“…[31] As regard to foam filters, a higher coking temperature may increase the mechanical strength of coated foam filters due to a stronger shrinkage of the coating materials compared with the bulk. [13] For uncoated foam filters, no significant difference was found within scatter for both coking temperatures comparing the compression test results at 1100 C [28,30] as well as at 1300, 1400, and 1500 C. [28,29] These previous studies revealed that Al 2 O 3 -C foam filters were brittle below 1300 C and ductile at and above 1400 C. For uncoated foam filters, Solarek et al [28] showed that the average compressive strength of filter samples with 20 mm diameter and 25 mm height at 800 C was %120 N. The values at 1000, 1100, 1200, and 1300 C were even lower (%90-110 N). The uncoated foam filters tested by Ranglack-Klemm et al [30] exhibited compressive strength of 100-190 N at 1100 C, whereas the CNT-ANS-and CNT-ANB-coated ones were 100-300 and 130-220 N, respectively.…”

“…All these factors also apply to the previously studied foam filters which exhibited such kind of scatter as well. [28][29][30] One reason for the superior compressive strength of the spaghetti filters, either as brittle material at lower temperatures or as ductile material at a higher temperature, should be the stronger full struts which are considered as one of the major advantages against the foam filters with hollow struts. The hollow space with a triangular cross section in the middle of a strut was inevitable in the case of foam filters prepared by the replica method.…”