Influence of Composition and Coking Temperature on the Properties and Microstructure of Carbon Bonded Al₂O₃–C Filter Materials

Abstract

To characterize the physical and mechanical properties of carbon-bonded Al 2 O 3 -C filter materials at room and high temperature up to 1600°C, the influence of the amount of binder and the development of the microstructure during coking were analyzed. The bulk samples were manufactured through a slurry route and afterwards pressed uniaxially. The amount of Carbores ® P binder was varied within 5 to 30 wt.% and the samples were coked at temperatures of 800°C and 1400°C. Afterwards, the physical (bulk density, open porosity, shrinkage and mechanical properties (cold crushing strength (CCS), cold modulus of rupture (CMOR), refractoriness under load) were determined. The CCS and CMOR values increased with increasing binder content and the results of the refractoriness under load tests show lower thermal expansion and earlier softening of the samples coked at 800°C.

Prediction of High Temperature Behavior of Open‐Cell Ceramic Foams Using an Experimental‐Numerical Approach

“…The specimens (specimen (1) in Figure 1) are compact with a microporosity of 34%. Detailed information about material preparation were given by Klemm et al [6] …”

Thermophysical Properties of Pressed and Casted Carbon‐Bonded Alumina (Al2O3‐C) up to 800 °C

“…[6] Following the green body production process all samples were pyrolized using a heating rate of 1 K min À1 up to a maximum temperature of 800°C with holding times of 30 min at every 100 K. According to the pyrolysis of industrial filter materials, a holding time of 3 h at the maximum temperature finalized this process step. Afterwards the slurry was casted into a rectangular plaster mould.…”

“…Diffraction patterns were recorded in the angular interval from 15°to 140°in steps of 0.04°. Slurry mass fractions (solid content) of uniaxial (uni) [6] and isostatic (iso) [6] pressed as well as slip casted (cas) materials. [11] The microstructural parameters, namely the mean cluster sizes La, Lc, lattice parameters a, c, and mean square atomic displacements u 2 a and u 2 c of high melting coal-tar pitch-Carbores ® P and carbon black, where both yield the turbostratic structure, [12] were refined using own computer code [13] based on the Warren-Bodenstein approach.…”

“…The minimum value obtained is about 3.75 Â 10 À6 K À1 for casted material containing 10 wt% of Carbores ® P at room temperature, the maximum reaches 6.50 Â 10 À6 K À1 measured for all uniaxially pressed samples at 800°C independently of the Carbores ® P mass fraction. [5,6,15] Reactions responsible for degassing can be avoided by using dwell times of 10-20 h and heating rates of less than 1 K min À1 . This is evident when comparing casted samples (see Figure 8b [Casted]), much less pronounced in case of the isostatically pressed samples (Figure 8b [Isostatic pressed]), but vanishes for the uniaxially pressed ones (Figure 8b [Uniaxial pressed]) parallel to the pressing direction.…”

“…In principle, the thermal conductivity is reduced by increasing the binder mass fraction, although some of the 15 wt% Carbores ® P measurements exceed the thermal conductivity of all others. Still the Carbores ® P can form relatively large agglomerates as the d 90 value is given with <0.2 mm [5,6] which might lead to inhomogeneities like shown in Figure 1b. Taking into account the results reported by Xie et al [23] who stated that a density change leads to an almost proportional change in thermal conductivity, the thermal conductivity of these materials with an appropriate density should be between the 10 and 20 wt% Carbores ® P curves.…”