| 1. |
- Stjernberg, Jesper, et al.
(författare)
-
Degradation of refractory bricks used as thermal insulation in rotary kilns for iron ore pellet production
- 2009
-
Ingår i: International Journal of Applied Ceramic Technology. - : Wiley. - 1546-542X .- 1744-7402. ; 6:6, s. 717-726
-
Tidskriftsartikel (refereegranskat)abstract
- Degradation of bricks in an iron ore pellet producing kiln has been investigated. Lab-scale tests of brick/slag interaction performed under different temperatures, atmospheres, and alkali additions show that addition of alkali dissolves the mullite in the brick and leads to formation of the phase nepheline (Na2O·Al2O3·2SiO2). At a high temperature, the grain boundary where nepheline is formed disintegrates due to volume expansion. At increased temperature, the nepheline transforms to an amorphous phase. Thus, a wear mechanism is proposed in the kiln using these bricks that involves these chemical reactions in combination with erosion by the continuously flowing slag.
|
|
| 2. |
- An, Di, et al.
(författare)
-
Additive manufacturing and characterization of complex Al2O3 parts based on a novel stereolithography method
- 2017
-
Ingår i: International Journal of Applied Ceramic Technology. - : Wiley. - 1546-542X .- 1744-7402. ; 14:5, s. 836-844
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we prepared Al2O3 ceramic green parts with complex geometry and architecture using an additive manufacturing process based on stereolithography. The rheological and thermal behavior of Al2O3 slurry was firstly examined and used to establish the conditions for molding and debinding. As opposed to previous researches that only focused on manufacture techniques, the sintering behavior and densification process were systematically investigated. In addition, special attentions were paid to the evolution of microstructure between green bodies and sintered parts. The results showed that debound parts were equipped with uniform particle packing and narrow pore size distribution. The dimensions of the Al2O3 parts changed anisotropically with the different processing steps. The densification process was greatly accelerated by the decrease in pore size and annihilating of interconnected pores in which significant grain growth was observed above 1450 degrees C. The sintered part also had a homogeneous microstructure and no interface between adjacent layers. High densification (relative density of 99.1%) and much desirable Vickers hardness (17.9 GPa) of Al2O3 parts were achieved at the sintering temperature of 1650 degrees C.
|
|
| 3. |
- Fu, Le, et al.
(författare)
-
Fabrication of mechanically robust nanoporous ZrSiO4 ceramics at low temperature with a low doping level of Mn dopant
- 2024
-
Ingår i: International Journal of Applied Ceramic Technology. - : John Wiley & Sons. - 1546-542X .- 1744-7402. ; 21:3, s. 1954-1964
-
Tidskriftsartikel (refereegranskat)abstract
- Zircon (ZrSiO4) ceramics have been widely used in many fields due to their excellent physical and chemical properties. However, ZrSiO4 ceramics typically possess moderately low mechanical properties, which hinders their wider application. Meanwhile, elevated temperatures (similar to 1500 degrees C) are required to obtain high-purity synthetic ZrSiO4 ceramics, which is time- and energy-consuming. In the present study, we prepared mechanically robust ZrSiO4 ceramics at low temperature (similar to 1170 degrees C) with a low doping level of Mn dopant (<2 mol%). The ZrSiO4 ceramic processed by hot isostatic pressing with .5 mol% Mn dopant achieved the highest flexural strength (512 MPa), elastic modulus (341 GPa), and nanohardness (20.8 GPa). These values are significantly higher than conventional ZrSiO4 ceramics. The strengthening mechanisms of the prepared ZrSiO4 ceramics were attributed to the formation of homogeneously-distributed nanopores due to incomplete densification and submicron ZrSiO4 grains (similar to 300 nm). The nanopores avoided stress concentration and deflected microcracks during loading, and the submicron ZrSiO4 grains endowed the ZrSiO4 ceramics with grain refinement strengthening. The results reported in this study would offer guidance to fabricate mechanically robust ZrSiO4 ceramics at low temperatures with a low doping level of dopant.
|
|
| 4. |
- Ganvir, Ashish, 1991-, et al.
(författare)
-
Characterization of Thermal Barrier Coatings Produced by Various Thermal Spray Techniques Using Solid Powder, Suspension, and Solution Precursor Feedstock Material
- 2016
-
Ingår i: International Journal of Applied CeramicTechnology. - : Wiley-Blackwell. - 1546-542X .- 1744-7402. ; 13:2, s. 324-332
-
Tidskriftsartikel (refereegranskat)abstract
- Use of a liquid feedstock in thermal spraying (an alternative to the conventional solid powder feedstock) is receiving an increasing level of interest due to its capability to produce the advanced submicrometer/nanostructured coatings. Suspension plasma spraying (SPS) and solution precursor plasma spraying (SPPS) are those advanced thermal spraying techniques which help to feed this liquid feedstock. These techniques have shown to produce better performance thermal barrier coatings (TBCs) than conventional thermal spraying. In this work, a comparative study was performed between SPS- and SPPS-sprayed TBCs which then were also compared with the conventional atmospheric plasma-sprayed (APS) TBCs. Experimental characterization included SEM, porosity analysis using weight difference by water infiltration, thermal conductivity measurements using laser flash analysis, and lifetime assessment using thermo-cyclic fatigue test. It was concluded that SPS coatings can produce a microstructure with columnar type features (intermediary between the columnar and vertically cracked microstructure), whereas SPPS can produce vertically cracked microstructure. It was also shown that SPS coatings with particle size in suspension (D50) <3 μm were highly porous with lower thermal conductivity than SPPS and APS coatings. Furthermore, SPS coatings have also shown a relatively better thermal cyclic fatigue lifetime than SPPS.
|
|
| 5. |
- Mahade, Satyapal, et al.
(författare)
-
Isothermal Oxidation Behavior of Gd2Zr2O7/YSZ Multilayered Thermal Barrier Coatings
- 2016
-
Ingår i: International Journal of Applied Ceramic Technology. - : Wiley-Blackwell. - 1546-542X .- 1744-7402. ; 13:3, s. 443-450
-
Tidskriftsartikel (refereegranskat)abstract
- Efficiency of a gas turbine can be increased by increasing the operating temperature. Yttria-stabilized zirconia (YSZ) is the standard thermal barrier coating (TBC) material used in gas turbine applications. However, above 1200°C, YSZ undergoes significant sintering and CMAS (calcium magnesium alumino silicate) infiltration. New ceramic materials of rare earth zirconate composition such as gadolinium zirconate (GZ) are promising candidates for thermal barrier coating applications (TBC) above 1200°C. Suspension plasma spray of single-layer YSZ, double-layer GZ/YSZ, and a triple-layer TBC comprising denser GZ on top of GZ/YSZ TBC was attempted. The overall coating thickness in all three TBCs was kept the same. Isothermal oxidation performance of the three TBCs along with bare substrate and bond-coated substrate was investigated for time intervals of 10 h, 50 h, and 100 h at 1150°C in air environment. Weight gain/loss analysis was carried out by sensitive weighing balance. Microstructural analysis was carried out using scanning electron microscopy (SEM). As-sprayed single-layer YSZ and double-layer GZ/YSZ showed columnar microstructure, whereas the denser layer in the triple-layer TBC was not columnar. Phase analysis of the top surface of as-sprayed TBCs was carried out using XRD. Porosity measurements were made by water intrusion method. In the weight gain analysis and SEM analysis, multilayered TBCs showed lower weight gain and lower TGO thickness compared to single-layer YSZ.
|
|
| 6. |
- Zaki, Zaki I., et al.
(författare)
-
Combustion synthesis of NbC/ZrO2 composites : Influence of Cr additives on the microstructure and mechanical properties
- 2021
-
Ingår i: International Journal of Applied Ceramic Technology. - : John Wiley & Sons. - 1546-542X .- 1744-7402. ; 18:5, s. 1502-1509
-
Tidskriftsartikel (refereegranskat)abstract
- Composites of NbC/ZrO2 reinforced with different weight ratios of Cr metal were prepared by dynamic compaction combustion from a blend of Nb2O5-Zr-Cr powders. Factors controlling the synthesis process, the microstructure and the mechanical properties of the samples, such as Cr wt% and the compression loads were studied. The samples were characterized by XRD, SEM, porosity and hardness measurements. The porosity value of sample with no additives was high and reached 31.6 vol%. A sudden decrease in the sample porosity to 2.4 vol % was noticed for sample containing 3.0 wt% of Cr. A high density sample with less than 2.0 vol % porosity and a maximum hardness of 1038 HV was produced using 5.0 wt% Cr under 300 MPa compression load. Detailed thermodynamic calculations for the effect of Cr additives on the physico-chemical properties of the system were introduced.
|
|
| 7. |
|
|
| 8. |
- Dehestani, Mahdi, et al.
(författare)
-
Phase stability and mechanical properties of zirconia and zirconia composites
- 2013
-
Ingår i: International Journal of Applied Ceramic Technology. - : Wiley. - 1546-542X. ; 10:1, s. 129-141
-
Tidskriftsartikel (refereegranskat)abstract
- Monolithic zirconia materials (3Y-TZP, 10Ce-TZP, and 12Ce-TZP) and their composites with 30 vol% alumina were produced. Low-temperature aging degradation (LTAD) and mechanical properties of materials were investigated. For assessment of phase stability in the materials, aging experiments were performed in water at 90°C for 32, 64, and 128 days. The aging phenomenon was characterized and monitored using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Four-point bending was used to determine the flexural strength of materials before and after aging treatment in water at 90°C for 2, 4, and 6 months. The aging experiments resulted in different phase transformation rates for the materials studied. The 12Ce-TZP containing materials showed the highest resistance to low-temperature aging and 3Y-TZP containing materials showed the highest bending strength. When compared, no change in flexural strength was observed between the materials not exposed to aging and the aged materials.
|
|
| 9. |
- Frodelius, Jenny, 1978-, et al.
(författare)
-
Annealing of thermally sprayed Ti2AlC coatings
- 2011
-
Ingår i: INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY. - : Blackwell. - 1546-542X. ; 8:1, s. 74-84
-
Tidskriftsartikel (refereegranskat)abstract
- Phase transformations during annealing of coatings sprayed with the High Velocity Oxy-Fuel technique using Ti2AlC powder have been investigated by in-situ x-ray diffraction. The asdeposited coatings, consisting of Ti2AlC, Ti3AlC2, TiC, Ti-Al, and oxides, are stable up to 500 °C. Ti3AlC2 forms above 550 °C and Ti2AlC forms above 700 °C by intercalation of Al into TiCx. For temperatures between 900 and 1100 °C, Ti3AlC2 and Ti2AlC decompose by losing Al to the surrounding matrix resulting in TiCx, and Al2O3. The thermal expansion coefficient between ambient and 700°C is 11.9·10-6 K-1. The thermal diffusivity at room temperature is 1.9·10-6 m2/s.
|
|
| 10. |
- Shen, Qiuwan, et al.
(författare)
-
Highly stable CuFe1.2Al.8O4 catalyst with low CO selectivity for hydrogen production in HT-PEMFCs application
-
Ingår i: International Journal of Applied Ceramic Technology. - 1546-542X.
-
Tidskriftsartikel (refereegranskat)abstract
- Methanol steam reforming (MSR) is considered as an effective way to provide on-board hydrogen production technology for fuel cell applications. CuFe1.2Al.8O4 spinel catalyst was synthesized by sol–gel method and the chemical and physical properties were studied in-depth. X-ray diffraction, hydrogen-temperature programmed reduction (H2-TPR), BET, and scanning electron microscopy were used to characterize the catalysts with reaction times of 20, 50, and 100 h. The results of H2-TPR showed that 90% of spinel Cu2+ was released after 100 h reaction. BET results show that the specific surface area and pore characteristics of the catalyst have not changed greatly after reaction for 20, 50, and 100 h. Furthermore, in the unsteady-state test, CuFe1.2Al.8O4 exhibited excellent catalytic activity and thermal stability under long-term repeated start-up and stop cycles. At 275°C, the methanol conversion rate remained around 94% and the CO selectivity remained below 1%. Therefore, the catalyst synthesized in this study has excellent stability and low CO selectivity, making it a highly promising on-board hydrogen production catalyst in the field of HT-proton exchange membrane fuel cells (PEMFCs).
|
|
