In order to enhance the mechanical strength of Hagi Porcelain (Hagiyaki), one of the oldest and famous potteries in Japan, new preparation condition was examined. Tempered Hagi porcelain, denominated as ‘Hagi Porcelain B’, was prepared with the Porcelain clay originating from Daido district, Yamaguchi Prefecture, Japan. Structural change of ‘Hagi Porcelain B’ was investigated by means of 57Fe-Mossbauer spectroscopy, X-ray diffractometry (XRD) and three-point bending test. Mechanical strength of the ‘original Hagi Porcelain B’ was estimated to be 43.1 MPa by means of the three-point bending test, while much larger value of 104.5 MPa could be achieved when tempered by a chemical modification. Mossbauer spectrum of the ‘original Hagi porcelain B’ was composed of a paramagnetic doublet and a magnetic sextet due to Fe(III) of γ-Fe2O3(maghemite), while only one paramagnetic doublet due to to octahedral Fe(II)O6 was observed for the ‘tempered Hagi Porcelain B’ with isomer shift and quadrupole splitting values of 1.13 and 2.15 mm s−1, respectively. It is considered that the absence of magnetic phase causes an increase of the mechanical strength because the maghemite phase has a defect spinel structure. These results indicate that mechanical strength of the ‘Hagi porcelain B’ could be enhanced by controlling the sintering condition.

Iron Oxides and Oxyhydroxides

Mechanically strengthened new Hagi porcelain developed by controlling the chemical environment of iron

The mineralogy and chemistry of a hydrothermal veinlet intruded into a gabbroic rock alteration profile (Serpa, Portugal)

A total of 30 clay samples were collected from the area around Riyadh city, Saudi Arabia. A complete chemical analysis was carried out using different techniques. X-ray diffraction studies showed that the clay samples were mainly of the smectite group with traces of the kaolinite one. The samples studied were classified as nontronite clay minerals. One of the clay fraction has been studied by Mossbauer spectroscopy as raw clay fraction and after being fired at 950–1,000 °C. The Mossbauer spectra showed accessory iron compounds in the form of hematite and goethite. The structural iron contents disintegrate on firing transforming into magnetic iron oxide and a paramagnetic small particles iron oxide.

http://medc.dicp.ac.cn/conference/isiame2012/volume/HI218/Preprint%20Hyperfine%20Interactions%20218%20%282013%29%20113-121%20Khalil.pdf

Crystal chemistry and Mössbauer spectroscopic analysis of clays around Riyadh for brick industry

A simple one-pot synthesis was utilized to prepare Mn-doped maghemite nanoparticles. A homogenized mixture of Mn- and Fe-acetylacetonates was heated in air atmosphere at 300 °C to produce Mn-doped maghemite. XRD showed only the presence of a spinel crystal structure with a linear increase of the unit-cell volume up to 20 mol% of the Mn dopant. Possible structural changes with increased Mn doping are briefly discussed.57Fe Mossbauer spectra recorded at 77 K were fitted with two sextets of lines corresponding to Fe3+ ions at A-tetrahedral and B-octahedral sites in maghemite. FE SEM images showed that Mn-doped maghemite nanoparticles were of good uniformity, with the crystallite size varying from 24 to 35 nm, as determined by XRD.

One-pot synthesis and properties of Mn-doped maghemite nanoparticles using acetylacetonate precursors

The formation of oxide phases at 900 °C in the system Fe2O3-“Pr2O3” was investigated. With a decrease in the molar fraction of Fe2O3 a corresponding increase in PrFeO3 was observed. For equal molar fractions of Fe2O3 and “Pr2O3” the formation of PrFeO3 and very small fractions of α-Fe2O3 plus an addi¬tional oxide phase, which could not be identified with certainty, were observed. With further increase in “Pr2O3” fraction the praseodymium oxides Pr6O11 and PrO2 started to become dominant in the phase com¬position. The small fraction (< 0.02) of the same unidentified oxide phase was also obtained when Pr(OH)3 was calcined in air at 900 °C ; this was probably a mixture of other praseodymium oxides with different average oxidation numbers of Pr. The results of XRD, 57Fe Mossbauer and FT-IR spectroscopies are discussed.

/pdf/formation-of-oxide-phases-in-the-system-pr-fe-o-3kjpxfq5ne.pdf

Formation of Oxide Phases in the System Pr-Fe-O

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Iron Oxides and Oxyhydroxides

Citations

Mechanically strengthened new Hagi porcelain developed by controlling the chemical environment of iron

The mineralogy and chemistry of a hydrothermal veinlet intruded into a gabbroic rock alteration profile (Serpa, Portugal)

Crystal chemistry and Mössbauer spectroscopic analysis of clays around Riyadh for brick industry

One-pot synthesis and properties of Mn-doped maghemite nanoparticles using acetylacetonate precursors

Formation of Oxide Phases in the System Pr-Fe-O

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