Microstructures and strength of microporous MgO-Mg(Al,Fe)2O4 refractory aggregates

Microporous MgO-Mg(Al, Fe)₂O₄ refractory aggregates were prepared using magnesite, Al(OH)₃ and Fe₂O₃ applying an in-situ decomposition synthesis method. At 1400–1600 °C, there was a Mg(Al, Fe)₂O₄ with Fe³⁺, which had two structures. One was a ring structure formed from Al(OH)₃ pseudomorph particle as a template and a low content of Fe³⁺. The other was the dot and strip structures precipitated in magnesite pseudomorph particles with a high content of Fe³⁺. Besides, at 1550–1600 °C, microporous MgO-Mg(Al, Fe)₂O₄ refractory aggregates had an excellent compressive strength (75.8–81.5 MPa) and apparent porosity (26.8%?28.2%).     

Shape and size of microfine aggregates: X-ray microcomputed tomography vs. laser diffraction

Microfine rock aggregates, formed naturally or in a crushing process, pass a #200 ASTM sieve, so have at least two orthogonal principal dimensions less than 75 μm, the sieve opening size. In this paper, for the first time, we capture true 3-D shape and size data of several different types of microfine aggregates, using X-ray microcomputed tomography (μCT) with a voxel size of 2 μm. This information is used to generate shape analyses of various kinds. Particle size distributions are also generated from the μCT data and quantitatively compared to the results of laser diffraction, which is the leading method for measuring particle size distributions of sub-millimeter size particles. By taking into account the actual particle shape, the differences between μCT and laser diffraction can be qualitatively explained.     

骨架密实型二灰集料的室内击实试验研究

采用碎卵石作为集料,通过分析二灰集料室内击实试验和无侧限抗压强度试验,探讨了不同级配类型对二灰集料最大干密度和最佳含水量的影响,及其对二灰集料无侧限抗压强度的影响,得出了相应的变化规律。     

Slag resistance mechanism of MgO–Mg2SiO4–SiC–C refractories containing porous multiphase aggregates

The slag resistance of MgO–SiC–C (MSC) refractories should be improved because of the mismatch in the thermal expansion coefficient between the aggregates and matrix, as well as the defects caused by the affinity between periclase and slag. In this study, MgO–Mg₂SiO₄–SiC–C (MMSC) refractories were prepared using porous multiphase MgO–Mg₂SiO₄ (M-M₂S) aggregates to replace dense fused magnesia aggregates. Compared to MSC, the slag penetration index of MMSC decreased by 43.5%. The structure of the porous aggregates increased the surface roughness, and the multiphase composition of the aggregates decreased the mismatch of the thermal expansion coefficient with the matrix, thus reducing debonding between the aggregates and matrix. The aggregates and matrix in the MMSC formed an interlocking structure, which bound them more tightly to improve the slag resistance. The slag viscosity at different depths from the initial slag/refractory interface was calculated using the Ribond model. The M-M₂S aggregates increased Si_xO_y^z− in the slag, which increased the slag polymerization and slag viscosity. The aggregates and matrix in the MMSC reacted with the slag to form high melting point phases, which reduced the channel of the slag. In addition, the penetration depth and velocity derived from the Washburn Equation were modified for the CaO–SiO₂–Al₂O₃–MgO–FeO slag and magnesia based refractory to accurately evaluate slag penetration.     

热诱导大豆蛋白纤维聚集体的分离及性质研究

酸性热处理条件下,随着大豆分离蛋白(SPI)自发形成纤维聚集体,仍有部分未自组装聚集的多肽分子存在其中,二者比例对蛋白功能性质产生较大影响。本文以超滤手段对热诱导大豆蛋白纤维聚集体和多肽进行大量分离,确定分离方法并研究两者的理化性质。结果表明:100 ku超滤膜反复分离两次即能获得较好的分离效果;SPI经热处理后,其等电点溶解度提高,但中性p H下溶解度变小,且蛋白水解致使其表面电位绝对值明显提高;分离所得纤维聚集体的氨基酸组成和表面电位与热处理蛋白相似,在等电点和中性p H溶解度更低;多肽则含有较少疏水氨基酸和较多负电氨基酸,在p H 2.0~9.0溶解度较好,其在酸性p H下电荷量和静电排斥力较低,导致其以无定形聚集体的形式存在,而中性p H其电荷量较高导致多肽分子间相互作用减弱,聚集体解离。     

磷酸化与钙交联处理对刺参胶原聚集体凝胶特性的影响

磷酸化与钙交联是影响刺参胶原聚集体凝胶特性的最重要因素之一。本文通过质构剖面(TPA)实验、应力松弛实验、低场核磁、VG染色等,研究了磷酸化与钙交联凝胶的质构学特征、水分迁移规律、化学键型变化以及胶原纤维特征的改变。结果表明:用2%三聚磷酸钠进行磷酸化对刺参胶原聚集体的凝胶特性有一定的破坏,其黏性、咀嚼性、η1、E1与空白组相比发生明显降低,其结合水含量降低,自由水含量升高,水分活度Aw明显升高;而在磷酸化基础上进行1%Ca Cl2交联则会对刺参胶原聚集体凝胶特性产生明显影响,其硬度及粘性比磷酸化刺参高,水分活度降低,提高了胶原聚集体与水分的结合程度,增强了凝胶性,使得胶原纤维结构更加稳定。与高温高压处理相比较,磷酸化与钙交联处理能够增强刺参胶原聚集体的凝胶特性,为刺参的加工及改性工艺提供了新途径。     

The relationship between squaraine dye surface morphology and sensitization behavior on SnS2 electrodes

Bis(4-dimethylamino-2-dihydroxyphenyl)squaraine (1-1 OHSQ) dyes were deposited on van der Waals surfaces of SnS₂ single crystals by two methods, dipping in a dye solution and evaporation of dye solution. Dye morphologies and photosensitization properties on the same samples were studied with atomic force microscopy (AFM) and photoelectrochemical measurements. AFM experiments in air revealed two distinct morphologies of dye aggregates and photocurrent measurements on the same samples in aqueous electrolytes showed correspondingly different photocurrent spectra. Three-dimensional needle-shaped 1-1 OHSQ aggregates aligned along crystal directions and showed a broad excitation spectrum that extended into the near-IR region with a peak around 800 nm. In contrast, flat aggregates presumably consisting of monolayers of 1-1 OHSQ molecules, had a sensitization maximum around 680 nm. Both peaks were red-shifted from absorption peak of 1-1 OHSQ in bulk dichloromethane solution. Spectral differences between these dye aggregates are discussed in terms of intermolecular interactions.     

Fractal Dimension of Alumina Aggregates Grown in Two Dimensions

The concepts of fractal geometry are applied to the analysis of 0.4-μm alumina constrained to agglomerate in two dimensions. Particles were trapped at the bottom surface of a drop of a dilute suspension, and the agglomeration process was directly observed, using an inverted optical microscope. Photographs were digitized and analyzed, using three distinct approaches. The results indicate that the agglomerates are fractal, having a dimension of approximately 1.5, which agrees well with the predictions of the diffusion-limited cluster–cluster aggregation model.