A REVIEW OF PARTICULATE FILLERS IN UNSATURATED POLYESTER COMPOSITES: PROPERTY ENHANCEMENT AND APPLICATIONS

Hadron therapy uses ion beams for irradiation of cancerous tissue taking advantage of the highly localized dose deposition in the target tumor. For a correct estimation of dose deposited in tissue surrounding the target it is necessary to consider also the contribution of energetic secondary radiation generated by primary ions. It was already experimentally demonstrated that this contribution can be measured using the semiconductor pixel detector Timepix (256 × 256 pixels with 55 μm pitch) visualizing traces of secondary particles. The resolving power of the detector enables the differentiation of traces of different types of particles. In this work we studied the possibilities of determination of different types of secondary particles in correlation with their flight direction. Such identification allows correct assignment of dose for each type of particle. The distribution of secondary particles was compared to Monte Carlo simulations. Measurements were performed with a PMMA target irradiated with a therapeutic carbon beam at the Heidelberg Ion-Beam Therapy Center (HIT).

Phase separation in a binary mixture of self-propelled particles with variable speed

In microstereolithography, three-dimensional microstructures are created by scanning an ultraviolet laser on a photocurable resin and stacking several such layers to form the desired structure. By mixing different types of particles in the resin, the formed microstructures exhibit various physical properties. For example, the magnetism and density of the microstructure can be controlled by adding magnetic particles and microcapsules to the resin. This method has been used to fabricate magnetic micromachines. Although such functional resins are useful, the incorporated magnetic particles and microcapsules can affect the fabrication resolution, making it difficult to fabricate microstructures with high precision. Thus, it is necessary to understand the effects of such microparticles and microcapsules on the fabrication process. In this study, we propose a simple model of curing resins containing magnetic particles and microcapsules to explain the effects of the magnetic particles and microcapsules. The proposed model can explain the observed curing characteristics of a resin that contains particles for all concentrations as well as for different types of magnetic particles and microcapsules. Finally, using the proposed model, we discuss how to improve the characteristics of resins containing microparticles to realize the high-resolution fabrication of three-dimensional microstructures with desirable material properties.

Whilst separation techniques relying on gravitational forces have become relatively sophisticated in their application to biology the same is not true for magnetic separation procedures. The use of the latter has been limited to the few cells which contain paramagnetic iron. However with the development of several different types of magnetic particles and selective delivery system (e.g. monoclonal antibodies) the use of magnetic separation techniques is growing rapidly. This review describes the different types of particles currently available, the magnetic separation technique applied to the different magnetic compounds and illustrates major uses to which magnetic separation procedures are currently applied in the area of biology and medicine.

Without the addition of any grain refiner, the inclusion particles in a melt will induce heterogeneous nucleation and grain initiation during the solidification of metallic materials. However, with grain refiner addition, the exogenous particles (from the grain refiner) and the native inclusions (e.g., oxide particles) will co-exist in the melt, and there will be competition for nucleation and grain initiation among different types of solid particles. In this paper, we analyze such competition in Al and Mg alloys using a numerical solidification model that we have developed previously. The numerical calculations show that the competition for nucleation is strongly dependent on nucleation undercooling of the different types of particles, while the competition for grain initiation is closely related to the sizes of solid particles. Based on the numerical results, the general rules of competition for nucleation and grain initiation have been developed: nucleation starts with particles of minimum nucleation undercooling, followed by particles with progressively larger nucleation undercooling; and grain initiation starts with solid particles of the largest size, followed by solid particles with progressively smaller sizes.

Three different synthesis strategies based on the in situ pre-polymerization process were employed in order to obtain High Impact Polystyrene (HIPS) with different type (morphology and size) of particles as the dispersed phase, achieved by the use of two styrene-butadiene rubbers (SBR) in the initial recipes. The rubbers used were tapered polystyrene/polybutadiene copolymers with a polystyrene/polybutadiene composition of 10/90 and 40/60 wt%. Results were discussed in terms of physical–chemical, morphological, mechanical and optical parameters. A combination of two or three types of particle morphologies, i.e. salami, core–shell and droplets in the same sample were evidenced by Transmission Electron Microscopy analysis, independently of the strategy employed. The grafting degree, volume fraction of the dispersed phase and impact strength were positively affected by the increase of the amount of 10/90 SBR in the recipe. Several HIPS samples showed a good balance between impact strength and gloss, particularly those obtained from the strategy herein named as melt blending.

Within the accuracy of the first-order Born approximation, the far-zone behaviors of light waves on scattering from a particulate medium with two different types of particles, i.e., deterministic particles and random particles, have been discussed. It is shown that both the location of the deterministic particles and the distribution of the random particles in the system play roles in the far-zone scattered spectral density. It is also shown that the distribution of the spectral degree of coherence of the scattered field oscillates with the increase of the scattering angle, and the amplitude of the oscillation is closely related to the location of the deterministic particles and the distribution of the random particles.

In the present search, attempts are made to develop the properties of PMMA resin that used for upper and lower prosthesis complete denture, by addition two different types of particles, which included: nano-hydroxyapatite (nHA) particles and micro-zirconia (ZrO2) particles that added with different volume fractions of (1%, 2% and 3%) to poly methyl methacrylate (PMMA) cold cured resin as new fluid resin as a matrix. Also woven glass fiber kind (E-glass) and woven Kevlar fiber kind (49), it were added with a fixed volume fraction of (5%) to PMMA composites. In this work the composite prosthetic dentures specimens preparation was done by using (Hand Lay-Up) method as six groups which includes: the first group consists of PMMA resin reinforced by nHA particles, the second group consists of PMMA resin reinforced by ZrO2 particles, the third group consists of (PMMA-nHA) and glass fiber layer as laminated composite , the fourth group consists of (PMMA-ZrO2) and glass fiber layer, the fifth group consists of (PMMA-nHA) and Kevlar fiber layer and the sixth group consists of (PMMA-ZrO2) and Kevlar fiber layer. The compression test result shows that the values of compression strength increased with increasing the volume fraction of (nHA and ZrO2) particles for all groups’ specimens. And the results showed the (PMMA-ZrO2) composite has greater values for compression strength. As well as the results shows that the maximum value of compression strength for hybrid laminated composite is obtained in hybrid laminated composite materials for fourth groups’ specimens (PMMA-ZrO2-5% Glass Fiber). Whereas the values of fatigue strength of hybrid laminated composite (PMMA-5% Kevlar fiber-3% nHA), it was higher than the fatigue strength of hybrid laminated composite (PMMA-5% Glass fiber-3% nHA) and the base material (Pure PMMA). The fatigue strength values at (106) loading Cycle for these specimens were (52, 38 and 15 MPa) respectively.

Pauli crystals in harmonic trap and on a sphere

We present the first in situ characterization of the conditioning process of a Vulcan supported precatalyst based on PtRu nanoparticles with either aluminumorganic or tetraalcylammonimum protection shells, obtained by x-ray absorption spectroscopic measurements on the Pt LIII-edge. To perform these measurements, a suitable reaction cell was developed. In combination with results from transmission electron microscopy, these data provide the basis for a detailed understanding of the above-mentioned process. In detail, we find that whereas the increase in particle size during this process and thus agglomeration of particles is rather small, there is a reduction of disorder in both types of particles, especially in the ones with an aluminumorganic protection shell. Furthermore, we observe different behavior of the Pt component in the two different types of particles during the oxidative step of the conditioning process, as only in aluminumorganically stabilized particles Pt atoms are subject to oxidation, whereas in the other sample they remain strictly zerovalent. Tentatively, these findings can be related to the internal structure of the as synthesized particles as obtained from preliminary evaluation of Pt LIII EXAFS-spectra.

High throughput micropatterning of interspersed cell arrays using capillary assembly

A mixed charge structure is composed of several different types of particles to achieve performance indicators that cannot be achieved by a single particle and usually need to be adjusted and evaluated to determine the parameters in the chamber according to different demand. To balance the accuracy and efficiency, and obtain more calculation parameters, the solid phase is modeled by the particle element method, while the fluid phase is modeled by a computational fluid dynamics solver based on the fifth-order weighted essentially non-oscillatory scheme. In the mixed charge structure of different granular propellant, different particles in different areas are classified and particle elements are divided, and the particle interface position is tracked and captured to form the particle element distribution with different sizes. In the mixed charge structure with central tubular propellant, the granular and the tubular propellants are calculated separately by different types of particle elements, and the source term is used in coupling simulation. Comparing with the calculation results of experiment, the velocity error is less than 1%, and the maximal breech pressure error is less than 3%. In the mixed granular charge structure, due to the differences in combustion rates and movement velocities of the particles, the distribution state of the particles within the chamber is significantly different from that of single particle charge. Additionally, the standard deviation of the porosity is greater in mixed granular charge (0.051: 0.0086). In the mixed charge structure with central tubular propellant, the porosity of tubular and particle distribution in the chamber is discontinuous, and the pressure distribution is effectively predicted. The calculation results show that the perfect consistency of ignition in the chamber, which shows the superior flame-spreading performance of the central tubular propellant. The particle element method can provide a powerful tool for the rapid modeling and simulation of two-phase flow.

This paper describes a concept of concentration and binary separation of particles and its experimental confirmations for digital microfluidics where droplets are driven by the mechanism of electrowetting-on-dielectric (EWOD). As a fundamental separation unit, a binary separation scheme is developed, separating two different types of particles in one droplet into two droplets, one type each. The separation scheme consists of three distinctive steps, each with their own challenges: (1) isolate two different types of particles by electrophoresis into two regions inside a mother droplet, (2) physically split the mother droplet into two daughter droplets by EWOD actuation so that each type of particle is concentrated in each daughter droplet, and (3) free the daughter droplets from the separation site by EWOD to ready them for follow-up microfluidic operations. By applying a similar procedure to a droplet containing only one type of particle, two daughter droplets of different particle concentrations can be created. Using negatively charged carboxylate modified latex (CML) particles, 83% of the total particles are concentrated in a daughter droplet. Successful binary separation is also demonstrated using negatively charged CML particles and no-charge-treated polystyrene particles. Despite the undesired vortex developed inside the mother droplet, about 70% of the total CML particles are concentrated in one daughter droplet while about 70% of the total polystyrene particles are concentrated in the other daughter droplet.

A composite refers to a material composed of two or more distinct constituents with different physical or chemical properties, combined to create a new material with enhanced characteristics. Polymer matrix composites (PMCs) have garnered significant attention due to their versatile properties and wide-ranging applications. The incorporation of fillers into polymer matrices plays a crucial role in tailoring the properties of PMCs. In polymer matrix composites there can be used two different types of fillers, natural and synthetic. In this study, unsaturated polyester resin was used as thermoset matrix material. Calcite and oak wood sawdust are used as fillers. Calcite is used as a synthetic filler and oak wood sawdust is a natural filler. Also, ratios vary depending on filler types, but the total filler ratio is chosen as 20%. Composite samples were prepared by pouring the mixture into an open Teflon mould. The physical properties of the samples such as tensile, impact, density, water absorption and hardness were investigated. Images of broken surfaces were analysed by SEM. As a result of the study, it was evaluated that oak wood sawdust and calcite can be used together in polyester-based composite applications.

Microplastics are ubiquitous in the marine environment and studies on their effects on benthic filter feeders at least partly revealed a negative influence. However, it is still unclear whether the effects of microplastics differ from those of natural suspended microparticles, which constitute a common stressor in many coastal environments. We present a series of experiments that compared the effects of six-week exposures of marine mussels to two types of natural particles (red clay and diatom shells) to two types of plastic particles (Polymethyl Methacrylate and Polyvinyl Chloride). Mussels of the family Mytilidae from temperate regions (Japan, Chile, Tasmania) through subtropical (Israel) to tropical environments (Cabo Verde) were exposed to concentrations of 1.5 mg/L, 15 mg/L and 150 mg/L of the respective microparticles. At the end of this period, we found significant effects of suspended particles on respiration rate, byssus production and condition index of the animals. There was no significant effect on clearance rate and survival. Surprisingly, we observed only small differences between the effects of the different types of particles, which suggests that the mussels were generally equally robust towards exposure to variable concentrations of suspended solids regardless of whether they were natural or plastic. We conclude, that microplastics and suspended solids elicit similar effects on the tested response variables, and that both types of microparticles mainly cause acute responses rather than more persistent carry-over effects.