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Subject: search.filters.subject.sintering

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    Precipitation Hardening of the Additive-Manufactured 17-4 PH Stainless Steel for Medical Applications
    (2026-01-01)
    Wittayawongsaruji, Chonnakan
    ;
    Vissanuyothin, Pichanan
    ;
    Jintawattanagul, Athicha
    ;
    Methabut, Wathit
    ;
    Jintawattanagul, Siraphat
    This study explores the impact of heat treatment parameters on the hardness and microstructure of 17-4PH stainless steel samples fabricated by additive manufacturing, with a focus on dimensional changes throughout the process. The additive manufacturing method used was Bound Metal Deposition (BMD), which includes digital scanning, 3D metal printing, sintering, and post-processing. It was observed that the printed parts undergo a substantial size increase 16.96% (height) and 18.14% (diameter) to compensate for material loss during the binder removal stage in sintering. Although the sintered parts shrink relative to the printed samples, they remain 3.25% taller and 6.05% wider than the original CAD dimensions. Following sintering, the samples underwent solution treatment and aging at various temperatures and times. Microstructural analysis post-solution treatment revealed a martensitic structure as the predominant phase. Aging caused the formation of strengthening precipitates, leading to peak hardness values of 422.0 and 303.0 HV0.5 at aging temperatures of 480 °C and 620 °C for 1 hour, respectively. Dimensional changes during the precipitation hardening stage were minimal and considered negligible.
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    Characterization of Fluoride-added Hydroxyapatite Derived from Eggshells for Dental Application
    (2023-01-01)
    Uthayaphamornwat, Vilasinee
    ;
    Khantachawana, Anak
    ;
    Kitiwan, Mettaya
    ;
    Srirussamee, Kasama
    ;
    Tunthawiroon, Phacharaphon
    Hydroxyapatite (HA) is one of the potential biomaterials used for treating dental defects. It can be incorporated with fluoride to enhance its anti-caries properties, though other properties could be dependent on processing technique. Hence, this study aims to characterize the influence of sintering on the properties of fluoride-added HA derived from eggshells. FTIR and XRD techniques are used to characterize the chemical and crystal structures of the samples, whilst dissolution test is carried out to characterize material degradation in the acidic environment. The results show that sintering increased the crystallinity in both HA and fluoride-add HA (F-HA) samples, which corresponds with the enhanced stability during the dissolution test. Moreover, it is also found that the addition of fluoride could further stabilize the material structure, though the impurities found in all the samples still need to be minimized. These findings suggest that sintering and fluoride addition could potentially enhance anti-caries properties of eggshell-derived HA, which could be beneficial for dental application in future subject to further process optimization and analysis.
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    Hydrogen Sulfide Adsorption on Alumina/Graphene Oxide Composites at Ambient Temperature
    (2022-11-01)
    Hankoy, Montree
    ;
    Kitiwan, Mettaya
    ;
    Phrompet, Chaiwat
    ;
    Ruttanapun, Chesta
    ;
    Kaewpengkrow, Prangtip Rittichote
    Hydrogen sulfide (H<inf>2</inf>S) is one of the most common pollutants found in natural gas and industrial waste. Over the few decades, the removal of H<inf>2</inf>S has become a significant problem. In the field of a clean environment such as water purification and toxic gas removal, graphene oxide (GO) has been found to have advantages. In this study, the influence of GO on alumina (Al<inf>2</inf>O<inf>3</inf>) as an adsorbent of H<inf>2</inf>S was examined. A series of Al<inf>2</inf>O<inf>3</inf>/GO (AGO) composites with varying graphene oxide addition (0.5–3.0 wt%) were prepared using the high-temperature sintering method. The X-ray diffraction patterns indicate the primary phase of Al<inf>2</inf>O<inf>3</inf> with hexagonal crystal structure for all AGO composites. Raman spectrometry measurements confirmed that the GO particles were incorporated in AGO composites. The TEM image indicated that GO nanosheets were embedded between Al<inf>2</inf>O<inf>3</inf> grains. The efficiency of AGO adsorbent at ambient temperature was investigated and compared with the pristine Al<inf>2</inf>O<inf>3</inf> adsorbent. The AGO composites adsorbent demonstrated the H<inf>2</inf>S breakthrough capacity in the range of 0.07–0.43 mg/g, which is higher than that of pristine Al<inf>2</inf>O<inf>3</inf> (0.06 mg/g). Furthermore, the highest H<inf>2</inf>S breakthrough capacity of 0.43 mg/g was obtained from AGO containing 3.0 wt% GO. This investigation demonstrates that the AGO adsorbent fabricated using a simple method has the potential to be used for H<inf>2</inf>S removal at ambient temperature.