The influence of particle shape on filtration processes was investigated. Two types of particles, including spherical polystyrene latex (PSL) and iron oxide, and perfect cubes of magnesium oxide, were examined. It was found that the removal efficiency of spherical particles on fibrous filters is very similar for corresponding sizes within the range of 50-300 nm, regardless of the fact that the densities of PSL and iron oxide differ by a factor of five. On the other hand, the removal efficiency of magnesium oxide cubic particles was measured, and found to be much lower than the removal efficiency for the aerodynamically similar spheres. Such disparity was ascribed to the different nature of the motion of the spherical and cubic particles along the fiber surface, following the initial collision. After touching the fiber surface and before coming to rest, the spherical particles could either slide or roll compared to the cubic ones, which could either slide or tumble. During tumbling, the area of contact between the particle and the fiber changes significantly, thus affecting the bounce probability, whilst for the spheres, the area of contact remains the same for any point of the particle trajectory. The extra probability of particle bounce by the cubes was derived from the experimental data. The particle kinetic energy was proposed to be responsible for the difference in removal efficiency of particles with alternative shapes, if all other process parameters remain the same. The increase in kinetic energy is shown to favor the increase of the bounce probability.

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To study the phase relations in the Bi-2212 and Yb 2 O 3 system, Bi 2 Sr 2 Ca 1−x Yb x Cu 2 O y thick films are prepared by partial melt processing via an intermediate reaction between Bi-2212 and Yb 2 O 3 . When Bi-2212 and Yb 2 O 3 are partially melted and then slowly cooled, solid solutions of Bi 2 Sr 2 Ca 1−x Yb x Cu 2 O y form by reactions between liquid and solid phases which contain Yb. Following these reactions, Ca is partially replaced in Bi-2212 matrix and participates in the formation of secondary phases, such as Bi-free, (Ca, Sr)O x and CaO. Variation of the Bi-2212-Yb 2 O 3 ratios and processing parameters changes the balance between the phases and leads to different Yb:Ca ratios in the Bi-2212 matrix of processed thick films. When the partial melting process is optimized for each sample to minimize the growth of secondary phases, x = 0.42-0.46 for the samples prepared at pO 2 = 0.01 atm, x = 0.24-0.29 for the samples prepared at pO 2 = 0.21 atm, x = 0.18-0.23 for the samples prepared at pO 2 = 0.99 atm are obtained regardless to the starting compositions.It is found that superconducting properties of Bi 2 Sr 2 Ca 1−x Yb x Cu 2 O y thick films strongly depend on the processing conditions, because the conditions result in different Yb content in the Bi-2212 matrix and the volume fraction of the secondary phases. The highest T c (0) of 77, 90 and 91 K were obtained for the samples processed at 0.01, 0.21 and 0.99 atm of O 2 , respectively.

[1] Iron-rich nanoparticles in aeolian mineral dust are of considerable importance to biogeochemical cycles. A major determinant of the chemical characteristics of nanoparticles is the parent sediment they are sourced from. The abrasion of dune sand has previously been shown to produce coarse dust (>1 m) during the occurrence of aeolian saltation. In this study, Australian red dune sands were laboratory abraded and emission of particles 18-414 nm was observed throughout the experiment duration ($1 h). The mean size of particles was 130 nm at the start of the test, but this gradually decreased to 110 nm at the end. The number concentration of particles approximately trebled over the course of the experiment with results suggesting that collisions between mobile sand grains led to the production of new nanosized particles over time. Chemical analysis revealed that these nanoparticles were highly abundant in iron, with some aluminium present. This chemical composition suggests that nanoparticles are produced from the clay coatings surrounding the parent sand grains. The study shows that abrasion from saltation occurring in Australian dune sands can release iron-rich nanoparticles, making them available for downwind transport during blowing dust events.