Phase transformation of transient B4C to CaB6 during production of CaB6 from colemanite

Yıldız, Ömer; Telle, Rainer; Schmalzried, C.; Kaiser, A.

doi:10.1016/j.jeurceramsoc.2004.09.001

Cited by 22 publications

(9 citation statements)

References 21 publications

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“…Bodies containing 10 wt% CaB 6 and fired at 15001C yield the best densification parameters, which is the highest bulk density (2.55 g/cm 3 ) and minimum apparent porosity. On using 10 wt% CaB 6 and sintered at 14001C, the bulk density slightly decreased to (2.45 g/ cm 3 ). The increase of CaB 6 content results in a gradual decrease of bulk density and an increase of apparent porosity.…”

Section: Resultsmentioning

confidence: 99%

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Synthesis and Characterization of Aluminum Borate Ceramic Whiskers

Kenawy

2010

International Journal of Applied Ceramic Technology

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Aluminum borates are synthesized via a precipitation process. Aluminum nitrate and calcium hexaboride (CaB 6 ) as a source of B 2 O 3 were used. Various proportions of aluminum nitrate were mixed with CaB 6 powder and to a solution of ammonium hydroxide. The resulting mixtures were evaporated and calcined up to 6501C. A porous ceramic with a framework structure of aluminum borate whiskers was synthesized in situ by firing the green compact bodies up to 14001C under argon gas avoiding the oxidation of the CaB 6 . The structure and morphology were investigated by XRD and SEM. The results indicate that whiskers exhibit a well-crystallized structure with an average diameter distribution of about 500 nm and lengths ranging from 5 to 8 mm. Porous aluminum borate ceramic consisted of whiskers with a porosity of 9-21% for samples sintered up to 14001C. Increasing the sintering temperature to 15001C and CaB 6 addition (15 wt%) deteriorated both the flexural strength and modulus of elasticity of the ceramic bodies.

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Section: Resultsmentioning

confidence: 99%

“…2 Numerous papers have been already published on the production CaB 6 and its characterization. [3][4][5] New investigations in the last 15 years are concerned with the electronic structure and magnetism of CaB 6 . 6 According to Kino et al,7 CaB 6 has a quasiparticle band structure and is of semimetallic character in bonding.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Aluminum Borate Ceramic Whiskers

Kenawy

2010

International Journal of Applied Ceramic Technology

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“…Similar studies were also performed in the fields of ceramics‐ and glass‐production. Yildiz and Yildiz et al report that calcined colemanite can be used as a starting material in the production process of CaB 6 , whereas the use of colemanite as source of boron in the production of borosilicate glasses and heatproof ceramics was reported by Pavlyukevich et al and Kichkailo and Levitskii, respectively. This interest in the use of colemanite in different production processes is triggered by the presence of large volumes of colemanite‐rich tailings at the mining extraction sites, which is the source for a low‐cost material.…”

Section: Introductionmentioning

confidence: 99%

“…In this light, and in view of the reported drawbacks following the use of colemanite as an additive in concretes and in ceramics production processes, a detailed characterization of the structure‐property relationships of this borate is advisable.…”

Section: Introductionmentioning

confidence: 99%

High‐pressure behavior and P‐induced phase transition of CaB₃O₄(OH)₃·H₂O (colemanite)

et al. 2017

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Colemanite (ideally CaB3O4(OH)3·H2O, space group P21/a, unit‐cell parameters: a ~ 8.74, b ~ 11.26, c ~ 6.10 Å, β ~ 110.1°) is one of the principal mineralogical components of borate deposits and the most important mineral commodity of boron. Its high‐pressure behavior is here described, for the first time, by means of in situ single‐crystal synchrotron X‐ray diffraction with a diamond anvil cell up to 24 GPa (and 293 K). Colemanite is stable, in its ambient‐conditions polymorph, up to 13.95 GPa. Between 13.95 and 14.91 GPa, an iso‐symmetric first‐order single‐crystal to single‐crystal phase transition (reconstructive in character) toward a denser polymorph (colemanite‐II) occurs, with: aCOL‐II=3·aCOL, bCOL‐II=bCOL, and cCOL‐II=2·cCOL. Up to 13.95 GPa, the bulk compression of colemanite is accommodated by the Ca‐polyhedron compression and the tilting of the rigid three‐membered rings of boron polyhedra. The phase transition leads to an increase in the average coordination number of both the B and Ca sites. A detailed description of the crystal structure of the high‐P polymorph, compared to the ambient‐conditions colemanite, is given. The elastic behaviors of colemanite and of its high‐P polymorph are described by means of III‐ and II‐order Birch‐Murnaghan equations of state, respectively, yielding the following refined parameters: KV0=67(4) GPa and KV′=5.5(7) [βV0=0.0149(9) GPa−1] for colemanite; KV0=50(8) GPa [βV0=0.020(3) GPa−1] for its high‐P polymorph.

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“…Zheng et al [1] synthesized CaB 6 by the reaction of CaCO 3 with B 4 C and carbon. Yildiz et al synthesized CaB 6 from colemanite and petroleum coke [17]. Otani [18] prepared CaB 6 crystals by an RF-heated floating zone method.…”

Section: Introductionmentioning

confidence: 99%

Electrolytic preparation of CaB6 by molten salt technique

Angappan

Helan

Visuvasam

et al. 2011

Ionics

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Calcium hexaboride (CaB 6 ) crystals with high melting point (2,235°C) have been conveniently synthesized at low temperature (900°C) from molten salt electrolysis. The synthesis was carried out using CaO-B 2 O 3 -LiF melt under argon atmosphere. Electrochemical experiments were carried out in an inconel reactor to having a high purity graphite crucible, which served as an electrolyte holding vessel as well as the anode. An electropolished molybdenum rod was employed as the cathode. The electrolysis was performed at 900°C under argon atmosphere at current densities ranging from 0.5 to 1.5 A/cm 2 at 1:6 M ratios of calcium and boron content. After the electrolysis, the cathode product was removed and cleaned using dilute HCl solution followed by triple distilled water. Characterization of the crystalline product by TG/DTA, XRD, CHNS, EDAX, XPS, EPR, and SEM were reported. From the studies, it has been observed that CaB 6 can be synthesized at all current densities and the products have some impurities.

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Phase transformation of transient B4C to CaB6 during production of CaB6 from colemanite

Cited by 22 publications

References 21 publications

Synthesis and Characterization of Aluminum Borate Ceramic Whiskers

Synthesis and Characterization of Aluminum Borate Ceramic Whiskers

High‐pressure behavior and P‐induced phase transition of CaB₃O₄(OH)₃·H₂O (colemanite)

Electrolytic preparation of CaB6 by molten salt technique

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Phase transformation of transient B4C to CaB6 during production of CaB6 from colemanite

Cited by 22 publications

References 21 publications

Synthesis and Characterization of Aluminum Borate Ceramic Whiskers

Synthesis and Characterization of Aluminum Borate Ceramic Whiskers

High‐pressure behavior and P‐induced phase transition of CaB3O4(OH)3·H2O (colemanite)

Electrolytic preparation of CaB6 by molten salt technique

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High‐pressure behavior and P‐induced phase transition of CaB₃O₄(OH)₃·H₂O (colemanite)