Spark plasma sintering of hydroxyapatite powders

Gu, Yang; Loh, N.H.; Khor, K.A.; Tor, Shu Beng; Cheang, P.

doi:10.1016/s0142-9612(01)00076-x

Cited by 198 publications

(117 citation statements)

References 17 publications

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“…Instead of using an external heat source, pulsed current passes through the electrically conducting pressure dyes, thereby generating the sintering temperature [21][22][23]. SPS has been used to generate dense ceramics with minimum grain growth [19] for many applications [23], including electroceramics [24,25], composites [26,27], bioceramics [28], thermoelectric materials [29], and transparent polycrystalline alumina (PCA) [30]. Only a few publications present SPS sintering of ZnO nanopowders, even though there is great potential in this technique.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Sintering of ZnO Nanopowders

et al. 2017

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Nanopowders are continuously under investigation as they open new perspectives in numerous fields. There are two main challenges to stimulating their development: sufficient low-cost, high throughput synthesis methods which lead to a production with well-defined and reproducible properties; and for ceramics specifically, the conservation of the powders' nanostructure after sintering. In this context, this paper presents the synthesis of a pure nanosized powder of ZnO (dv 50~6 0 nm, easily redispersable) by using a continuous Segmented Flow Tubular Reactor (SFTR), which has previously shown its versatility and its robustness, ensuring a high powder quality and reproducibility over time. A higher scale of production can be achieved based on a "scale-out" concept by replicating the tubular reactors. The sinterability of ZnO nanopowders synthesized by the SFTR was studied, by natural sintering at 900 • C and 1100 • C, and Spark Plasma Sintering (SPS) at 900 • C. The performance of the synthesized nanopowder was compared to a commercial ZnO nanopowder of high quality. The samples obtained from the synthesized nanopowder could not be densified at low temperature by traditional sintering, whereas SPS led to a fully dense material after only 5 min at 900 • C, while also limiting the grain growth, thus leading to a nanostructured material.

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Section: Introductionmentioning

confidence: 99%

Synthesis and Sintering of ZnO Nanopowders

et al. 2017

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“…The PECS method has been shown to produce a sintered body with a relative density of 100% at low temperature and in a shorter time than conventional methods due to the rapid heating rate. 27)29 ) The results indicated that the PECS method was useful for fabrication of a sintered body that retained the radioactive iodine and it was confirmed that the HA nanolayer on zeolite A plays an important role in preventing the elution of iodine molecules in low O 2 content water. Rapid crystal growth of HA is also well known to occur at temperatures above 800°C, which would allow it to cover the Sr-zeolite phase (Sr-feldspar phase after sintering), further improving its stability in alkaline solutions.…”

Section: )7)mentioning

confidence: 90%

Long-term immobilization of strontium ions using zeolite A/calcium phosphate nanocomposites

Watanabe

Miwa

Ikoma

et al. 2010

J. Ceram. Soc. Japan

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Zeolite A whose surface was evenly covered with tiny scaly calcium deficient hydroxyapatite (Ca-def HA) nanocrystals was prepared through the ion exchange reaction of ammonium and calcium ions as a novel encapsulation material for the long-term immobilization of radioactive Sr-90. The maximum capacity for Sr ion uptake in the zeolite A/Ca-def HA nanocomposite was determined to be 0.40 mmol g ¹1, which was comparable to the value for zeolite A alone; this was because of the loose arrangement of Ca-def HA nanocrystals on the surfaces. The nanocomposite obtained was heated at 800 to 1200°C to improve the solution stability of adsorbed Sr ions. The low crystalline Ca-def HA became tricalcium phosphate (TCP) after heating at over 850°C. A phase change from zeolite A to an amorphous phase was observed at 850°C and to feldspar at 1000°C. The elution of Sr ions from the nanocomposites heated was compared to those from the heated zeolite A, under alkaline conditions (pH 10.2) similar to those found in geological layers deeper than 300 m. The elution amounts of Sr ions from the nanocomposites decreased with heating temperatures over 950°C compared with those of zeolite A, due to the complete coverage of TCP crystals. These results indicate that calcium phosphate nano-layers on the zeolite A surfaces play an important role for the long-term encapsulation of Sr ions in the nanocomposites.

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“…A three-component sintered body consisting of I 2 -zeolite A, an HA nanolayer, and hydroxyfluorapatite (HFA) was fabricated at 950 • C by pulsed electric current sintering (PECS) method [136][137][138]; it had a relative density of up to 98.1±2.2%, which was calculated by considering the HFA/zeolite weight ratio. The sintered body was brown owing to the retained iodine ( figure 14(I)).…”

Section: Zeolite/apatite Compositesmentioning

confidence: 99%

Geomaterials: their application to environmental remediation

Yamada

Tamura

Watanabe

et al. 2011

Science and Technology of Advanced Materials

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Geomaterials are materials inspired by geological systems originating from the billion years long history of the Earth. This article reviews three important classes of geomaterials. The first one is smectites-layered silicates with a cation-exchange capacity. Smectites are useful for removing pollutants and as intercalation compounds, catalysts and polymer nanocomposites. The second class is layered double hydroxides (LDHs). They have an anion-exchange capacity and are used as catalysts, catalyst precursors, sorbents and scavengers for halogens. The third class of geomaterials is zeolites-microporous materials with a cation-exchange capacity which are used for removing harmful cations. Zeolite composites with LDHs can absorb ammonium and phosphate ions in rivers and lakes, whereas zeolite/apatite composites can immobilize the radioactive iodine. These geomaterials are essential for environmental remediation.

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Spark plasma sintering of hydroxyapatite powders

Cited by 198 publications

References 17 publications

Synthesis and Sintering of ZnO Nanopowders

Synthesis and Sintering of ZnO Nanopowders

Long-term immobilization of strontium ions using zeolite A/calcium phosphate nanocomposites

Geomaterials: their application to environmental remediation

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