固态氚增殖包层中球床堆积性能研究

基于球床堆积实验和离散元数值模拟对包层中球床的堆积性能做了初步研究。圆柱形一元(单尺寸颗粒)球床的堆积性能的结果显示随着球床直径与颗粒直径比的增大,球床的平均堆积因子逐渐增高,实验与模拟结果一致;采用二元颗粒(双尺寸颗粒)、提高颗粒粒度比可以显著提高球床的堆积因子,二元球床的堆积因子随着大颗粒体积分数的增加先增加后减小,在大颗粒体积分数约为60%～80%时达到最大。优化了二元球床的填充工艺,最终二元球床的堆积因子基本达到0.8,但球床的均匀性欠佳。

齿科珠状聚甲基丙烯酸甲酯的粒度分布及堆积性能与粉液比的关系

本文采用粉体颗粒特性表征技术 ,对 6组PMMA粉的粒度分布及堆积性能进行测定 ;并测定各组样品的适合粉液比。结果表明 ,近似服从对数正态分布的PMMA粉的粒度分布因平均粒度的不同 ,对其堆积性能产生不同的影响 ;粉液比随着振实空隙率的降低而呈升高趋势。因此 ,通过提高PMMA粉的平均粒度及粒度分布宽度 ,降低堆积空隙率 ,可以在结构上为提高粉液比提供可行性。

高强耐磨水泥基材料的设计与性能

运用最紧密堆积理论对高强耐磨材料的集料进行配比设计,通过提高高强耐磨水泥基材料的集料堆叠密实度,提高其强度和耐磨性能。并参照RPC材料设计原理,通过外加剂的优选降低水固比、矿物掺合料掺量的复配以及增强材料的使用改善材料内部的多尺度结构,从而优化材料的施工工作性、抗裂性能、耐磨性,达到提高耐磨材料的服役性能与年限。

Construction of a 3D meso-structure and analysis of mechanical properties for deposit body medium

For deposit body medium, the internal structural properties may be the controlling factors for the strength of the material and the mechanical response. Based on the results of soil-rock meso-statistics using digital imaging, a simulated annealing algorithm is adopted to expand the meso-structural features of deposit bodies in 3D. The construction of the 3D meso-structure of a deposit body is achieved, and then the particle flow analysis program PFC3 D is used to simulate the mechanical properties of the deposit body. It is shown that with a combination of the simulated annealing algorithm and the statistical feature functions, the randomness and heterogeneity of the rock distribution in the 3D inner structure of deposit body medium can be realized, and the reconstructed structural features of the deposit medium can match the features of the digital images well. The spatial utilizations and the compacting effects of the body-centered cubic, hexagonal close and face-centered packing models are high, so these structures can be applied in the simulations of the deposit structures. However, the shear features of the deposit medium vary depending on the different model constructive modes. Rocks, which are the backbone of the deposit, are the factors that determine the shear strength and deformation modulus of the deposit body. The modeling method proposed is useful for the construction of 3D meso-scope models from 2D meso-scope statistics and can be used for studying the mechanical properties of mixed media, such as deposit bodies.

Glass formation,thermal and mechanical properties of ZrCuAlNi bulk metallic glasses

The glass forming ability, thermal and mechanical properties of some Zr Cu Al Ni bulk metallic glasses were analyzed. The compositions of the alloys were theoretically determined with the dense packing and kinetic fragility index models. Cylindrical and conical ingots were produced by copper mould suction-casting under Ar atmosphere. The conical ingots were characterized by means of X-ray diffraction in order to determine the glassy structure. It was found that both alloys have a critical glassy diameter, Dc, of 3 mm. Thermal behaviours were investigated by differential scanning calorimetry at heating rates of 0.5, 0.67 and 0.83 K/s. The gamma parameter γ, supercooled liquid region ΔTx, and reduced glass transition temperature Trg, of the experimentally obtained glasses indicated high glass forming ability. The glassy compositions showed a fragility index of ~40 GPa. The compression test of the investigated alloys was carried out at a strain rate of 0.016 s^-1, obtaining a elastic modulus of ~83 GPa, total deformation of ~5%, yield strength of 1.6 GPa and hardness of 4 GPa. It was concluded that the use of the dense packing and kinetic fragility index models helped to predict glass-forming compositions in the family alloy investigated.

Tape casting of borosilicate glass/Al_2O_3 composites for LTCC substrate with various relative molecular masses of PVB

The dispersion, stabilization and rheological properties of the slurry with various relative molecular masses of PVB were studied. The sintering properties, microstructure and dielectric properties of borosilicate glass/Al203 composites were also investigated. The intensities of the typical vibrating bands decrease with the decrease of the relative molecular mass of PVB, which demonstrates that the content of butyral groups in PVB binders decreases correspondingly, leading to a rapid decrease in the viscosity of the mixed slurry. The solid content of samples increases with the decrease of the relative molecular mass of PVB, and this further leads to the increase of tape thickness, bulk density and dried-shrinkage coefficient of tapes. The bulk density, relative density, three-point strength and dielectric constant of sintered samples increase with the increase of the solid content, and the shrinkage and dielectric loss decrease. By contrast, samples for PVB-5s exhibit better properties of a bulk density of 3.10 g/cm3, a relative density of 98.1%, a three-point strength of 208 MPa, aεt value of 8.01, a tanδ value of 7.6× 10^-4 at 10 MHz and a well matching with Ag electrodes.

Packed anode derived from cocklebur fruit for improving long-term performance of microbial fuel cells

Packed anode of microbial fuel cells(MFCs),commonly with a dense structure, suffers from the clogging,resulting in unsatisfied long-term stability of MFCs. Herein,we fabricate a biochar-based packed anode with a loose structure to enhance the long-term performance of MFCs equipped with packed anodes. The biochar, derived from cocklebur fruit, endows the packed anode with a loose structure but excellent conductivity. Once incorporated into MFCs, the biochar-based packed anode can yield comparable performance to benchmark materials. Particularly, the biochar-based MFCs present no obvious decrease of the power output during 150 days’ operation, which is attributed to the clogging-resistant effect induced by the loose structure of biochar-based anode. The cocklebur fruit-derived biochar can be a promising candidate for MFC anodes, and should facilitate both scaling-up and practical applications of MFCs.