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.

A new thermophoretic particle precipitator has been developed for representative and efficient collection of aerosol particles from the ambient air and technological pipelines. The device consists of hot and cold plates (5 × 5 cm2) capable of operation at temperature gradients ranging from 20 000 to 100 000 K/m. A gas sample is made to pass through a 1‐mm slot between the plates at a flow rate of up to 1.5 L/min, which makes the device suitable for operation in conjunction with common aerosol instruments including DMA and diffusion batteries with similar operational flow rates. It was shown that the efficiency of the device was highest for the lowest gas flow rate used (0.3 L/min) reaching a level of above 99%. The efficiency was decreased reaching its minimal values at the highest flow rate investigated (1.5 L/min). However, even for highest flow rate, the average efficiency for removal of particle smaller than 60 nm was around 50%.

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Elongated aerosol particle removal on fibrous filters has been investigated. It was shown that particle agglomerates are removed much more efficiently compared to the regularly shaped single particles with identical electrical mobility diameter at two filtration velocities tested. The experimental results were compared with the classical filtration theory and it was shown that the theoretical predictions, which are based on the assumption that the particles are spherical, are significantly different compared to an agglomerate filtration efficiency value. In order to account for a particle shape non-regularity, dominating nanoparticle removal mechanisms were firstly evaluated for a regular particle of certain size and then adjusted by fitting coefficients k 1 (for diffusion component) and k 2 (for interception). These coefficients were determined by fitting the theoretical values that gives the best coincidence with the measured data points. As was further demonstrated theoretically, the coefficient k 1 is identical to the ratio of the actual particle surface area to the surface area of the spherical particle of the equivalent diameter. On the other hand, the coefficient k 2 was found to be equal to the ratio of the projection of a given particle on a plane perpendicular to a streamline, to that of the spherical particle of the equivalent diameter. The reported findings would allow undertaking more accurate evaluation of the removal efficiency of non-regular aerosol particle, which is especially important for industrial applications where non-regular aerosols are frequently met.