Characterization of Spinel Phase Formed in the Kaolin-Mullite Thermal Sequence

The spinel phase formed on the thermal reaction of kaolin group minerals was characterized by X-ray quantitative analysis, lattice constant determination, and chemical analysis by analytical TEM. The spinel phase was determined to be nearly γ-Al₂O₃ with ∼8 wt% of SiO₂, significantly less than previously reported.     

Structural Characterization of the Spinel Phase in the Kaolin-Mullite Reaction Series Through Lattice Energy

Kaolinite undergoes structural transformation on heating. X-ray photographs reveal the existence of a spinel-type phase when kaolin is heated at 980°C. The kaolinite decomposes into a spinel phase with the expulsion of silica. A controversy arises as to whether the spinel phase is γ-Al₂O₃ or Si-Al spinel. Calculating the lattice energies of the structures confirms that the spinel phase is γ-Al₂O₃ and not Si-Al spinel, as proposed earlier. The heat involvement in phase transformation, as obtained from experimental observation at 980°C, is also explained in the light of lattice energies.     

堇青石对镁铝尖晶石质耐火材料抗热震性能的影响

镁铝尖晶石堇青石复合耐火材料是以各种级配的镁铝尖晶石和1 ～Omm的堇青石为骨料,0.088 mm镁铝尖晶石和二氧化硅微粉为基质,加入硅溶胶结合剂制成的烧结耐火材料.所获得的材料经过1200℃烧结具有优良抗热震性以及满足要求的其他性能,随着堇青石掺量的增加,材料的抗折强度降低,抗热震性增强.     

氧化硅在尖晶石型晶相中的固溶范围

通过共析技术,用硝酸铝九水化合物和四乙基正硅酸盐合成了具有不同化学成分的Al2O3-SiO2混合凝胶。通过X射线衍射技术和29Si金属-氧化铝-硅的核磁共振分析得到这些凝胶晶相演变的研究结果。测出了中间型Al-Si尖晶石相的晶格参数,所得数据显示,如不考虑所选混合凝胶的成分,尖晶石相的成分就没有变化。这些结果证实了略小于28％的SiO2量好象在Al—Si尖晶石结构中与γ-Al2O3共同作为固溶体。对化学计量莫来石的两种成分混合凝胶的莫来化反应进行了叙述。     

Phase Transformations in Chemically Precipitated Mixtures for Alumomagnesium Spinel

The hydroxide precipitation method is used to produce initial materials for subsequent synthesis of alumomagnesium spinel. Using the IR spectroscopy and x-ray phase analysis methods, the processes of interaction between the materials obtained, phase transformations, and structure formation in alumospinel under thermal treatment are investigated. It is established that the spinel formation process passes via an intermediate phase, i.e., crystal hydrate Mg₅Al₄O₁₁ ? 15H₂O, which in heat treatment transforms into aluminomagnesium spinel. With increasing temperature its structure is perfected and its quantity increases significantly. The formation of this phase ends at a temperature of 1300 – 1350°C.     

Characterization of Scale Formed on the Surfaces of Toilet Bowls

Repeated use of a toilet results in the build-up of a deposit derived from urine and hard water on the surface of the toilet bowl. The hardened mineral scale is difficult to clean completely, especially in the case of deposits under the rim. A number of studies have focused on kidney stones, which are also caused by urine in the urinary tract; little attention, however, has been paid to the detailed composition and structure of the toilet scale. To develop powerful products for removing the toilet scale effectively instead of relying on acid-cleaning and scrubbing, the composition and the accumulation mechanism of the scale must be clarified. Scale samples collected from the bowl surface were characterized by IR, XRF, XRD, ICP–AES, SEM–EDS and HPLC techniques and found to consist mainly of calcium phosphates, struvite, calcium carbonate, uric acid and proteins. After acid treatment of the scale, a film-like structure of protein, produced as a result of the metabolism of bacteria and mold, was left behind. The scale had composite structures that were composed of the inorganic minerals and the organic materials listed above. This structure might be critical to making the scale resistant to removal by acid-containing cleaners.     

高温液相对熟料方镁石形成的影响

分别制备了由白云石分解产生的方镁石和不同高温液相量及液相粘度的高镁水泥熟料,并利用化学分析、XRD、SEM及熟料岩相结构分析等测试方法,研究了高温液相对熟料中方镁石形成的影响.研究结果表明:与白云石分解产生的方镁石相比,熟料液相显著促进了方镁石晶体的发育;熟料液相增多时,方镁石含量有所减少;液相粘度降低时,方镁石在熟料中的分布更加均匀.     

Influence of Coarse Aggregate Content on the Thermal Conductivity of Alumina–Spinel Castables

The thermal conductivity of three commercial-quality alumina-spinel castables containing 90–96 wt% A1₂O₃ was measured in the range room temperature to 1000°C by a hot wire method. Experimental results indicate that the thermal conductivity increases with an increase in coarse aggregate content; higher corundum content and purer alumina aggregates are more important than coarse aggregate content for higher thermal conductivity of alumina-spinel castables.     

组成和添加剂对镁铝尖晶石热膨胀性能的影响

研究了镁铝摩尔比为2：1、1：1和1：2的3种不同尖晶石组成，以确定其线性热膨胀性。不同的添加剂，即Cr2O3、TiO2和MgSO4以2％的量加入到所有组成中，并借助于膨胀研究，确定烧结产物的特性。富镁成分始终显示出较高的膨胀性，添加物没有显示出对任何组成有大的影响，与相分析研究结果相似。     

A Novel Study on the Gel Phase Formed in a Catanionic Surfactant System

A novel gel phase was constructed in a catanionic surfactant system with the compositions of 1-tetradecyl-3-methylimidazolium chloride (C₁₄mimCl) and sodium dodecyl sulfate (SDS). The gel phases were studied through visual observations, differential scanning calorimetry (DSC), rheological measurements, and scanning electron microscopy (SEM). The visual observation and DSC confirmed the formation of gels and phase transitions from gel to sol. The dynamic rheological results showed the viscoelastic properties of gels. The SEM technique was used to further indicate the microstructure of gels. Finally, the formation mechanisms of gels are proposed based on the critical packing parameter. We expect to develop a new route to construct the gels.