Sulfur in chromia

The solubility of sulfur in chromia has been studied in H₂-H₂O-H₂S tagged with³⁵S at 973 and 1173 K at low oxygen and sulfur partial pressures typical for coal gasification-systems. For monocrystalline samples, it has been shown that sulfur-containing species are only present adsorbed on the surface of the specimens and can be removed by ultrasonic cleaning in acetone. The surface coverage after 4 weeks of exposure to H₂-H₂O-H₂S was between 2.8 and 19.3% of a monolayer. In polycrystalline chromia, sulfur was located only in pores and cracks of the sample. In dense, compact areas of the specimens the solubility of sulfur was below the detection limit of autoradiography, which was estimated to be better than 0.17 ppm.     

Synthesis of Thermally Stable χ-Alumina by Thermal Decomposition of Aluminum Isopropoxide in Toluene

Thermal decomposition of aluminum isopropoxide in toluene at 315°C resulted in χ-alumina that had high thermal stability, whereas the reaction at lower temperatures resulted in formation of an amorphous product. The χ-alumina thus obtained directly transformed to α-alumina at ∼1150°C, bypassing the other transition alumina phases, whereas the amorphous product transformed to γ-alumina and then to θ-alumina before final transformation to α-alumina. When the χ-alumina, solvothermally synthesized at 315°C, was recovered by the removal of the solvent at the reaction temperature, thermal stability of the product was improved further. This procedure is convenient because it avoids bothersome work-up processes that yield large-surface-area and large-pore-volume alumina.     

Direct Observation of Internal Structure in Spray-Dried Alumina Granules

The internal structure of spray-dried alumina granules was characterized by optical microscopy by immersing them in a liquid having a refractive index close to that of alumina. This method provides a unique technique for the detailed analysis of the internal structure of spray-dried granules.     

Phase-Separated Polyzwitterionic Hydrogels with Tunable Sponge-Like Structures for Stable Solar Steam Generation

Solar steam generation (SSG) through hydrogel-based evaporators has shown great promise for freshwater production. However, developing hydrogel-based evaporators with stable SSG performance in high-salinity brines remains challenging. Herein, phase-separated polyzwitterionic hydrogel-based evaporators are presented with sponge-like structures comprising interconnected pores for stable SSG performance, which are fabricated by photopolymerization of sulfobetaine methacrylate (SBMA) in water-dimethyl sulfoxide (DMSO) mixed solvents. It is shown that driven by competitive adsorption, the structures of the resulting poly(sulfobetaine methacrylate) (PSBMA) hydrogels can be readily tuned by the volume ratio of DMSO to achieve phase separation. The optimized phase-separated PSBMA hydrogels, combining the unique anti-polyelectrolyte effects of polyzwitterionic hydrogels, demonstrate a rapid water transport capability in brines. After introducing photothermal polypyrrole particles on the surface of the phase-separated PSBMA hydrogel evaporators, a stable water evaporation rate of ≈2.024 kg m⁻² h⁻¹ and high solar-to-vapor efficiency of ≈97.5% in a 3.5 wt.% brine are obtained under simulated solar light irradiation (1.0 kW m⁻²). Surprisingly, the evaporation rates remain stable even under high-intensity solar irradiation (2.0 kW m⁻²). It is anticipated that the polyzwitterionic hydrogel evaporators with sponge-like porous structures will contribute to developing SSG technology for high-salinity seawater applications.     

Shape Transformations and Self-Assembly of Hairy Particles under Confinement

Molecular dynamics simulations are used to investigate the behavior of polymer-tethered nanoparticles between two inert or attractive walls. The confinement in pores creates new possibilities for controlling the shape transformation of individual hairy particles and their self-organization. We introduce a minimalistic model of the system; only chain-wall interactions are assumed to be attractive, while the others are softly repulsive. We show how the shape of isolated particles can be controlled by changing the wall separation and the strength of the interaction with the surfaces. For attractive walls, we found two types of structures, “bridges” and “mounds”. The first structures are similar to flanged spools in which the chains are connected with both walls and form bridges between them. We observed various bridges, symmetrical and asymmetrical spools, hourglasses, and pillars. The bridge-like structures can be “nano-oscillators” in which the cores jump from one wall to the other. We also study the self-assembly of a dense fluid of hairy particles in slit-like pores and analyze how the system morphology depends on interactions with the surfaces and the wall separation. The hairy particles form layers parallel to the walls. Different ordered structures, resembling two-dimensional crystalline lattices, are reported. We demonstrate that hairy particles are a versatile soft component forming a variety of structures in the slits.     

渝东南两套富有机质页岩的孔隙结构特征——来自FIB－SEM的新启示

使用聚焦离子束扫描电镜(FIB-SEM)对渝东南地区下寒武统牛蹄塘组和上奥陶统五峰组—下志留统龙马溪组2套富有机质页岩的孔隙结构进行了系统观察,并对页岩纳米级有机质孔隙进行了三维重构和孔隙结构参数定量分析.研究发现,五峰组—龙马溪组页岩内层间微裂隙、矿物粒内孔、矿物粒间孔和有机质孔隙均较为发育.其中,有机质孔隙呈蜂窝状均匀发育,孔隙半径集中在3~100 nm,孔隙连通性较好,FIB-SEM三维重构计算有机质孔隙度在9.13%~18.42%之间,岩石总孔隙度中有机质孔隙度的贡献受控于TOC含量;牛蹄塘组页岩内溶蚀孔和粒间孔较为发育,有机质孔隙发育不均匀,孔隙呈扁平状或针孔状,孔隙半径集中在3~25 nm,孔隙连通性较差,有机质孔隙度在1.59%以下,有机质孔隙度对岩石总孔隙度的贡献与TOC含量关系较小,页岩的总孔隙度主要来自于矿物基质孔.FIB-SEM揭示了2套页岩有机质孔隙结构存在较大差异.     

Revealing the Removal Mechanism of Vanadium Addition on Nitrogen Pores in 30Cr15Mo1N High-Nitrogen Steel Ingot

The removal mechanism of vanadium addition on nitrogen pores in 30Cr15Mo1N ingot is systematically investigated through statistical analysis and theoretical calculation. The nitrogen solubility is obtained by the thermodynamic model, and the nitrogen content is obtained by combining the ProCAST software and the C–K model. Then, according to the formula of critical nucleation radius and growth rate of nitrogen bubbles, the variation of critical nucleation radius and growth rate of nitrogen bubbles with different vanadium contents is calculated. As the vanadium content increases, the number and mean area of nitrogen pores decrease. In comparison to the 0 V ingot, the number of nitrogen pores decreases in the 0.2 V ingot, but there is an increase in the number of large-sized nitrogen pores (>3000 μm in diameter). When the vanadium content increases to 0.4, the nitrogen pores are completely removed. The results demonstrate that increasing vanadium content can remove nitrogen pores. Since the solidification mode remains unchanged with increasing vanadium content, increasing the vanadium content cannot remove nitrogen pores by changing the solidification mode of the 30Cr15Mo1N ingots. Therefore, increasing the vanadium content removes the nitrogen pores mainly by inhibiting the nucleation of nitrogen bubbles and promoting nitrogen bubble overflow in 30Cr15Mo1N ingots.     

粉煤灰粒径对地质聚合物孔结构及性能的影响

对原状粉煤灰进行分级处理,获得3种不同粒径特征(D50=5.02μm、D50=15.74μm、D50=35.32μm)的粉煤灰颗粒,并利用其制备地质聚合物,研究粉煤灰颗粒粒径对地质聚合物孔隙率、孔径分布、显微结构、抗压强度的影响,探讨了影响抗压强度的关键因素,建立了该体系抗压强度与孔隙率的关系式。结果表明:细化粉煤灰粒径可制备具有高强度、低孔隙率地质聚合物。利用粉煤灰细灰取代粗灰,促进了致密凝胶相的产生,凝胶孔孔隙率明显减小,试样总孔隙率由18.72%降至11.04%;细灰颗粒与铝硅酸盐凝胶结合良好,试样早期强度基本无变化,28 d强度提升明显,达到62.6 MPa。地质聚合物的抗压强度与孔隙率符合y=80.53e~(-2.32x)的指数关系。     

Unmodified SBA-15 adsorbents for the removal and separation of Th(IV) and U(VI) ions: the role of pore channels and surface-active sites

ABSTRACT

The removal of Th(IV) and U(VI) by calcinated, non-calcinated, and methyl grafted SBA-15 (abbreviated as SBA-15, SBA-15-NC and SBA-15-MG, correspondingly) were compared to elucidate the role of pores and surface adsorption sites on SBA-15 adsorbents. It was proposed that the contribution of pores and surface-active sites of SBA-15 increases its higher adsorption capacity with respect to the other examined adsorbents. The kinetic studies revealed that the adsorption and also desorption occurred initially on the surface and then to the pores. Adsorption/desorption of the ions into pores was occurred with slow kinetics.