Mitsuru Wakamatsu

Mineralizing action of iron in amorphous silica

Abstract The mineralizing action of iron in amorphous silica was investigated by firing mixtures of silica gel and iron oxides at 1100 and 1150°C. Silica gel did not crystallize in the absence of ferrous ion below 1200°C. When silica gel mixed with ferrous oxalate was heated at 1100°C in a mildly reducing atmosphere(N2, CO2, CO), quartz, cristobalite and ferrous silicate (Fe2SiO4) were formed. Application of the reducing atmosphere from room temperature promoted the crystallization to quartz, while that from the soaking temperature after heating in N2 accelerated the formation of cristobalite. Chemical analysis revealed that the N2 atmosphere acted as a mildly oxidizing atmosphere to FeO possibly due to the coexistence of water vapor released from silica gel and impurity O2. Furthermore, tentative crystallization mechanism is proposed where mildly reduced and mildly oxidized Fe2SiO4 produced nuclei for quartz and cristobalite, respectively.

Effect of heating and cooling atmospheres on colors of glaze and glass containing copper

Abstract ESR and ESCA analyses of a copper red glaze prepared by firing under a strongly reducing atmosphere followed by oxidation during a cooling period showed that Cu 1+ and Cu 2 O were major species in it. From the investigation of behavior and chemical states of copper and tin under various firing conditions, mechanisms of the formation of Cu 2 O and its protection were assumed as follows: Cu 2+ and Sn 4+ are reduced to metals during reducing firing and then the metals aggregate in the glaze surface layer, forming alloy. In the next oxidation process, metallic copper and tin are oxidized to Cu 2 O or Cu 1+ and SnO respectively. Due to the affinity of SnO on Cu 2 O for glass, glass containing Sn 2+ surrounds and consequently protects Cu 2 O from excessive oxidation. A colorless copper glass before striking contained copper mainly as Cu 1+ . ESCA analysis showed that striking of the glass caused the selective formation of Cu 2 O.

Effect of furnace atmosphere on color of iron glaze

The glaze containing 1.8wt% Fe 2 O 3 were invariably yellow when fired under oxidizing and neutral atmospheres, but showed a wide range of color when fired under reducing atmosphere depending on the concentration of reducing gases and cooling conditions. From chemical analysis, it was found that the glazes fired in air and nitrogen contained iron mostly in a state of Fe 3+ and that those fired under reducing atmosphere contain major part of Fe 2+ and a small amount of Fe 3+ . The ESR signals of Fe 3+ and metallic iron were not observed in the greenish blue glaze. This result suggested that the greenish blue color was produced by Fe 2+ associated with a small amount of Fe 3+ . The X-ray diffraction analysis showed the presence of metallic iron in the black glaze fired under strong reducing atmosphere. From the EPMA results that iron was highly enriched in the surface layer of this black glaze it was assumed that iron aggregated into metal during firing.

Role of Sn2+ in development of red color during reheating of copper glass

It was found that migrations of both Cu 1+ and Sn 2+ in glass occurred above 500 °C. In the case of conventional copper glass containing both Cu 1+ and Sn, Cu 2 O formation during striking takes place dominantly in its interior but in contrast, on reheating the glass in vacuo which did not contain Sn 2+ , Cu 1+ scarcely precipitated in the interior of the glass but aggregated as Cu 2 O on its surface. Thus, the role of Sn 2+ in striking was considered to be the formation of the nucleus on which Cu 1+ could deposit as Cu 2 O. In some cases, metallic copper was detected in the struck glasses by ESCA. These results indicate that metallic copper formed by reduction of Cu 1+ by Sn 2+ acts as the center of deposition for Cu.

Model Experiments on the Flow of Gases in an End-Port Tank Using Water and Hot Gases as the Fluids

Experiments on the Flow patterns of gases in the melting chamber of an end-port tank were carried out by means of the two dimensional model with water and also the three dimensional model with gases of medium temperature.The cold model experiments have thrown some new light upon the relation between the flow pattern of fluid and the working characteristic of this type of furnace, namely;(1) the location of ports exerts considerable influences on the flow of gases, so that the so-called U-turn flow is not always stable in the case of gaseous fuel to say the least of it.(2) the nearer are the ports locate to the side wall of the furnace the more stable will be the U-turn flow.(3) the U-turn flow will be more or less stabilized with a new type of bridge wall projecting triangularly toward the direction of the flow of glass.(4) in spite of the authors hope the even distribution of the flowing gases was found to be insufficient.(5) there would be many chances for the stronger erosion of the furnace refractories as compared with the side port furnaces.The lack of thermal similitude in two dimensional model was then made up by the three dimensional gas model in which the temperature at many points were measured to search for the pattern of flowing gases. The results obtained may be summarized as follows;(1) owing to the effect of buoyancy the burner inclining less than 15° towards glass level does not give the flame which hits the glass surface.(2) the deeper the burner is inserted into the melting chamber the longer and milder flame will be obtained.(3) excepting the flame having comparatively larger momentum the so-called complete U-turn flame can scarecely be obtained.(4) larger stagnant areas are formed in the center as well as near the various corners of the melting chamber.(5) it was also observed that the U-turn flow was not always stable. The flow pattern will more or less be influenced by the furnace design, the operating pressure, the method of burning fuel, and especially the kind of the fuel.(6) with the exception of buoyancy effects nearly all the phenomena observed in the hot model could will be interpreted from the results obtained in the cold model experiments, and the authors are coming round to the idea that a cold model is a very powerful means for studying the flow characteristics as well as the performance of a furnace.