Preparation of equiaxed α-Al2O3 by adding oxalic acid

Chen, Haiyang; Ren, Bo; Chen, Linchao; Zhao, Fei; Bai, Qijing; Chen, Junhong; Li, Bin

doi:10.1016/j.ceramint.2021.08.029

Cited by 7 publications

(9 citation statements)

References 37 publications

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“…Among these absorption bands presented by A2-A5, the absorption bands centered at 3621, 3526, 3456, and 3393 cm −1 can be assigned to the stretching vibrations of hydroxyl groups in Al(OH)3 and adsorbed water [34]. The intensive bands shown at 1704, 1415, and 1297 cm −1 were related to the stretching vibration of carboxyl COO − , implying that a surface complex (Al2C2O8H4), as we reported previously, had been formed due to the interaction of oxalic acid and Al(OH)3 [33]. Regarding the bands in the 400 to 1200 cm −1 interval (local amplification in Figure 1b), the weak band observed at 915 cm −1 was caused by the deformation of surface hydroxyls.…”

Section: Resultssupporting

confidence: 70%

“…In our previous report [33], oxalic acid was confirmed to be helpful in reducing the resultant temperature of α-Al 2 O 3 by 100 • C. Therefore, in this paper, we proposed for the first time adding oxalic acid and NH 4 F as additives in the preparation process of plate-like α-Al 2 O 3 . The synergistic influences of oxalic acid and NH 4 F on the crystal transition order of Al(OH) 3 were studied, and the optimum F content was explored.…”

Section: Introductionmentioning

confidence: 86%

“…As in our previous work [ 33 ], first, oxalic acid solution with a concentration of 0.16 mol/L was prepared. Subsequently, 20 g of Al(OH) 3 and 60 mL of oxalic acid solution were mixed and ball-milled for 11 h. Then, 0, 0.25, 0.5, 1, and 2 wt.% NH 4 F by weight of Al(OH) 3 was added to continue the ball milling for 1 h. Afterward, the resulting mixtures were air dried at 50 °C for 72 h. The obtained samples were labeled A1 (0 wt.%), A2 (0.25 wt.%), A3(0.5 wt.%), A4 (1 wt.%), and A5(2 wt.%), according to the amount of NH 4 F. Finally, specimens A1–A5 were heated from room temperature to distinct temperatures (700, 750, 800, 850, 900, and 950 °C) at a heating rate of 5 °C/min holding for 3 h.…”

Section: Methodsmentioning

confidence: 99%

“…In our previous report [ 33 ], oxalic acid was confirmed to be helpful in reducing the resultant temperature of α-Al 2 O 3 by 100 °C. Therefore, in this paper, we proposed for the first time adding oxalic acid and NH 4 F as additives in the preparation process of plate-like α-Al 2 O 3 .…”

Section: Introductionmentioning

confidence: 94%

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Low-Temperature Fabrication of Plate-like α-Al2O3 with Less NH4F Additive

Chen

Meng

et al. 2023

Materials

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Fluorinated compounds are effective mineralization agents for the fabrication of plate-like α-Al2O3. However, in the preparation of plate-like α-Al2O3, it is still an extremely challenging task to reduce the content of fluoride while ensuring a low synthesis temperature. Herein, oxalic acid and NH4F are proposed for the first time as additives in the preparation of plate-like α-Al2O3. The results showed that plate-like α-Al2O3 can be synthesized at a low temperature of 850 °C with the synergistic effect of oxalic acid and 1 wt.% NH4F. Additionally, the synergistic effect of oxalic acid and NH4F not only can reduce the conversion temperature of α-Al2O3 but also can change the phase transition sequence.

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Section: Resultssupporting

confidence: 70%

Section: Introductionmentioning

confidence: 86%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

See 2 more Smart Citations

Low-Temperature Fabrication of Plate-like α-Al2O3 with Less NH4F Additive

Chen

Meng

et al. 2023

Materials

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“…04-015-8995 from the ICDD database). Chen et al [ 49 ] and Álvarez et al [ 36 ] in their works adjusted the α-Al 2 O 3 phase to the diffraction effects appearing at similar angular positions.…”

Section: Resultsmentioning

confidence: 99%

Influence of Alumina Grade on Sintering Properties and Possible Application in Binder Jetting Additive Technology

Kwiatkowski,

Marczyk,

Putyra

et al. 2023

Materials

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Alumina is one of the most popular ceramic materials widely used in both tooling and construction applications due to its low production cost, and high properties. However, the final properties of the product depend not only on the purity of the powder, but also, e.g., on its particle size, specific surface area, and the production technology used. These parameters are particularly important in the case of choosing additive techniques for the production of details. Therefore, the article presents the results of comparing five grades of Al2O3 ceramic powder. Their specific surface area (via Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods), particle size distribution, and phase composition by X-ray diffraction (XRD) were determined. Moreover, the surface morphology was characterized by the scanning electron microscopy (SEM) technique. The discrepancy between generally available data and the results obtained from measurements has been indicated. Moreover, the method of spark plasma sintering (SPS), equipped with the registration system of the position of the pressing punch during the process, was used to determine the sinterability curves of each of the tested grades of Al2O3 powder. Based on the obtained results, a significant influence of the specific surface area, particle size, and the width of their distribution at the beginning of the Al2O3 powder sintering process was confirmed. Furthermore, the possibility of using the analyzed variants of powders for binder jetting technology was assessed. The dependence of the particle size of the powder used on the quality of the printed parts was demonstrated. The procedure presented in this paper, which involves analyzing the properties of alumina varieties, was used to optimize the Al2O3 powder material for binder jetting printing. The selection of the best powder in terms of technological properties and good sinterability makes it possible to reduce the number of 3D printing processes, which makes it more economical and less time-consuming.

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