Examining the pozzolanicity of supplementary cementitious materials using isothermal calorimetry and thermogravimetric analysis

It has recently been proposed that the pozzolanicity of supplementary cementitious materials can be determined by monitoring the heat released when supplementary cementitious materials are mixed with calcium hydroxide at high temperature and high pH. In this study, the heat release is measured using this procedure for a variety of different supplementary cementitious materials. In addition, thermogravimetric analysis is performed on the reacted material to determine the amount of calcium hydroxide consumed. The heat release and calcium hydroxide consumption can be used in conjunction to compare supplementary cementitious materials. Calcium hydroxide consumption can be used to determine the extent of reaction of supplementary cementitious materials in pastes where supplementary cementitious materials are used to replace a portion of cement.     

白炭黑/炭黑复合填充对NR性能的影响

在白炭黑和炭黑填料总量一定的情况下,研究了不同白炭黑/炭黑配比对NR性能的影响。结果表明,白炭黑用量增加,NR硫化速率下降,体系中炭黑填料网络被破坏且白炭黑-橡胶间较弱的相互作用也会对NR硫化胶力学性能产生一系列影响。DMA结果表明,加入20~25份白炭黑对提高硫化胶的抗湿滑性和降低滚动阻力最为有效。     

Clustering of Yb in silica-based glasses synthesized by SPCVD

Light absorption and scattering are studied in silica-based slab lightguides with different contents of aluminum, ytterbium and phosphorous in the silica core. The slab lightguides used in the experiments were fabricated from the structures of doped silica deposited on the inner surface of a substrate silica tube via surface-plasma chemical vapor deposition (SPCVD). The synthesized glasses contained 0.004–0.4 at. % of Yb, as well as various contents of Al and P ranging from 0 to 1 at. %. Loss spectra of the slab lightguides are measured in the 300–1050 nm wavelength band, with the influence of the profusion of deposited glass on the loss spectra investigated by means of substrate tube external processing at a temperature of ∼1600 °C in the flame of a hydrogen-oxygen burner. We found that a combination of the temperature of the inner surface of the substrate tube during the deposition process and the subsequent profusion of the deposited structure essentially influence the distribution uniformity of ytterbium ions in the glass volume. If aluminum and phosphorous are present in the glass, such profusion can influence the formation of ytterbium clusters in opposite ways.     

Cell membrane disruption induced by amorphous silica nanoparticles in erythrocytes,lymphocytes, malignant melanocytes,and macrophages

It is of critical importance to examine carefully the potential adverse effects of engineered nanoparticles (NPs) on human health and environments. In the present study, we have investigated the disruption of cell membranes induced by amorphous silica NPs in erythrocytes, lymphocytes (Jurkat), malignant melanocytes (B16F10), and macrophages (J774.1); these four types of mammalian cells have distinctive characteristics in terms of nucleated/non-nucleated cells, adherent/non-adherent cells, endocytosis, and phagocytosis. The silica-induced membranolysis was examined by exposing these different cells to serum-free culture media containing the amorphous silica NPs of different diameters (28, 50, 55, 156, and 461 nm) under similar conditions. We investigated how the silica-induced membranolysis of the cells of different origins is influenced by the size and dose of the silica NPs. Additionally, the interaction forces of a silica microsphere with a living cell or a giant unilamellar vesicle composed of zwitterionic phosphatidylcholine lipids were measured by colloid-probe atomic force microcopy, whereby the affinities of silica surface for plasma membranes and protein-free phospholipid membranes were estimated. Possible mechanism of the silica-induced membranolysis was discussed.     

Potassium promoted Ru/meso-macroporous SiO2 catalyst for the preferential oxidation of CO in H2-rich gases

A series of potassium promoted Ru/meso-macroporous SiO₂ catalysts were prepared and used for the preferential oxidation of CO (CO-PROX) in H₂-rich gases. The catalysts were characterized by using techniques of TEM, SEM TPR, XPS, and N₂ adsorption/desorption. The catalytic activity of Ru/meso-macroporous SiO₂ was markedly improved by the introduction of potassium. The catalyst of K-5 wt.% Ru/meso-macroporous SiO₂ with molar ratio of K:Ru = 5:7 exhibited relatively high activity and selectivity for CO-PROX. Nanoparticles of ruthenium species can be highly dispersed on the meso-macroporous SiO₂ support by the simple impregnation method. The addition of potassium weakened the interaction between metallic Ru and the silica support. Lowering the reduction temperature of ruthenium ions could keep ruthenium in the state of metallic Ru, and it was proposed that potassium acted as an electron donating agent. The electron donating effect of potassium improved the low temperature activity for CO oxidation and increased the selectivity of O₂ for CO oxidation, thus K-modified Ru/meso-macroporous SiO₂ catalyst showed obviously a wide temperature window for CO elimination from H₂-rich gases, meanwhile the related mechanism was discussed.     

白炭黑的液相分散工艺对溶聚丁苯橡胶改性研究

选用数显型高速分散机进行白炭黑环己烷浆液的制备,通过圆盘式离心沉降粒度仪测定了白炭黑在环己烷浆液中的粒径,采用自然沉降法评价了各批次浆液的稳定性。考察了偶联剂种类、用量、搅拌方式、反应温度等条件对浆液分散效果的影响。实验结果表明:硅烷偶联剂KH550的用量为白炭黑质量的10%,在15 000和20 000 r/min搅拌转速下分别分散5 min,温度为10℃时,白炭黑在环己烷中的分散效果最佳。将改性后的白炭黑液相混炼填充至丁苯橡胶中其力学性能相对于干法填充有一定提升。     

Preparation and characterization of dual-responsive spiropyran-based random copolymer brushes via surface-initiated atom transfer radical polymerization

Silica nanoparticles (SiO₂) were grafted with the precursor random copolymer of 1′-(2-acryloxyethyl)-3′,3′-dimethyl-6-nitrospiro-(2H-1-benzopyran-2,2′-indoline) (SPMA) and tert-butyl methacrylate (tBMA) by surface-initiated atom transfer radical polymerization (SI-ATRP), and SiO₂-g-P(SPMA-co-methacrylic acid (MAA)) was obtained via chemical hydrolysis of the resulting precursor random copolymer in acidic conditions. From transmission electron microscopy, we observed the spherical morphology of monodispersed silica nanoparticles and core-shell structure of SiO₂-g-P(SPMA-co-MAA). Energy dispersive spectroscopy, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, and the thermogravimetric analysis indicated that the polymer had been successfully grafted onto the surface of silica nanoparticles. The dual-responsive properties were characterized by means of ultraviolet-visible spectrophotometer and dynamic light scattering. The average hydrodynamic diameter of SiO₂-g-P(SPMA-co-MAA) increased from 185.7 to 212.7 nm under ultraviolet light irradiation for 5 min. Also, the particle size of SiO₂-g-P(SPMA-co-MAA) increased with the rising pH value of surrounding condition.     

弱磁精选设备在磁铁矿降硅提铁中的研究与实践

阐述了弱磁精选设备对磁铁矿降硅提铁技术研究及应用的意义，指出弱磁场磁选设备若可以达到降硅提铁目的，磁选工艺应是首选方法。分析了常规磁选设备用于降硅提铁分选精度不高的原因，介绍了弱磁场降硅提铁磁选设备的研究及应用现状。生产实践表明，磁聚机和磁选柱用于磁铁矿降硅提铁效果明显。     

Organic–inorganic nanomatrix structure and properties of related naturally occurring rubbery macromolecules

The outstanding mechanical properties of soft materials i.e. natural rubber are partly due to the organic–inorganic nanomatrix structure because numerous organic microparticles are dispersed in a small amount of an inorganic nanomatrix composed of inorganic nanoparticles and organic macromolecules. Here we form an organic–inorganic nanomatrix using graft-copolymerization of a vinyl monomer with an inorganic oxide precursor onto natural rubber particles with an average diameter of 1 μm dispersed in water. The inorganic oxide precursor is converted into inorganic oxide nanoparticles through hydrolysis and condensation, forming chemical linkages between natural rubber microparticles and inorganic oxide nanoparticles. Transmission electron microscopy indicates that the organic–inorganic nanomatrix is densely filled with inorganic oxide nanoparticles and the natural rubber microparticles are dispersed in the nanomatrix. This nanomatrix composite realizes both energetic elasticity and entropic elasticity of a soft material, opening a novel field of building block chemistry with respect to a pair of organic microparticles and inorganic nanoparticles.     

硅砖熔洞的成因

通过硅砖熔洞、铁斑在硅砖检验中的重要性的阐述,对生产过程中出现的一些硅砖熔洞进行原因排查,探讨了硅砖铁洞、钙洞的成因及应采取的预防措施。