Search Results (5)

Soft organic gels are commonly used as tissue phantoms for experiments. In the mimic ultrasound imaging field, researchers are developing approaches to modify the acoustic properties of the gels. Introducing oil liquids and hard solid particles are two common methods to tune acoustic and mechanical properties of the soft gels. In this work, the acoustic wave energy loss mechanisms were studied in detail on Agar gel with both micro-Graphite and nano-Alumina particles. Via experimental measurements, the results show that the effective acoustic energy loss is comparable in these two recipes. However, temporal pulse elongation and scattering behaviors were distinguishable. To understand the sound attenuation mechanism in detail, numerical simulations in controlled conditions were conducted, from wavelengths longer than the particle diameter to wavelengths shorter than particles, and we compared perfect bonding and insufficient bonding between the hard particles surrounding gels. Comparing the experimental observations and numerical simulation results, the Agar gel with nano-Alumina presents stronger dispersion-induced energy loss than the Agar gel with micro-Graphite. On the contrary, the Agar gel with micro-Graphite shows more significant scattering-induced destructive interferences than the Agar gel with nano-Alumina. Full article

It is difficult to select low-cost filler materials. Specifically, carbon-based filling materials are a matter of concern, and developing a carbon-filled polymer composite with enhanced properties is necessary. In this study, the authors developed a polymer composite using virgin polypropylene (PP) as a matrix and affordable micrographite (µG) as a filler. The developed composite has many potential applications in the automotive, aerospace, and electronic industries. To prepare the test specimens, the composite was prepared using a twin-screw extruder containing 3, 6, 9, 12, or 15 wt.% µG powder (BET surface area ≈ 29 m²/g; particle size > 50 µm) followed by injection molding. Different mechanical properties like the tensile, flexural, and impact strengths were determined. The prepared composites were further characterized by means of XRD, TGA, DSC, FTIR, DMA, FESEM, and PLM tests. The results were analyzed and compared with those for PP. Improved tensile (up to ≈ 34 MPa) and flexural (up to ≈ 40 MPa) strength was observed with an increase in the µG content. However, the impact strength continuously decreased (maximum ≈ 32 J/m for PP) with fractures. These findings underscore that graphite plays a significant role in controlling the deformation behavior and ultimate strength of composites. An XRD analysis revealed that adding graphite restructured the crystalline arrangement of PP and altered the composite’s crystallographic properties. Nonetheless, no induction effect (β-phase formation) was observed. A moderate enhancement in the thermal stability was observed owing to a small increase in the melt (T_m), onset (T_onset), and residual (T_R) temperatures. A microstructural analysis showed that the micrographite powder strongly prevented spherulite growth and modified the graphite powder’s rate of dispersion and agglomeration in a polymer matrix. The results show that graphite could be a viable low-cost alternative carbon-based filler material in polypropylene matrices. Full article

A composite is a combination of two or more insoluble materials that have greater characteristics than all of their individual constituents. The current study focuses on manufacturing and testing the mechanical characteristics of A356 alloy composites reinforced with micrographite particles at different weight fractions of 0%, 5%, 10%, and 15%. According to the findings, including micrographite particles up to 10% wt. increases the bulk hardness, tensile strength, and compression strength of the A356 alloy matrix. In addition, scanning electron microscopy (SEM) was employed to inspect the tensile-fractured surfaces of the fabricated composites. Full article

A new Pb-free glass containing several oxides (Bi₂O₃, B₂O₃, SiO₂, Al₂O₃ and ZnO) with sintering temperature reduced down to 600 °C has been developed for applications in a piezoresistive pressure sensor. Using this low sintering temperature glass, it was possible to fabricate micrographite-based pastes and piezoresistive films without losses of graphitic material during the sintering. Good adherence of the films onto alumina substrates was observed and attributed in part to the reactions of ZnO and Bi₂O₃ with alumina substrates. Piezoresistive films with uniformly distributed micrographite particles were produced using sodium carboxymethyl cellulose (NaCMC) in aqueous solutions during the preparation of pastes. NaCMC plays a decisive role in interactions between micrographite particles and glassy matrix, providing good wettability of glass powder particles and homogeneous distribution of MG particles in the pastes. Finally, excellent repeatability of the sensor response to the applied deformations was verified in cycling experiments when the sample was submitted to 1000 load/release cycles. These results demonstrated very high stability of the sensor response (within ±1%), and also evidenced high stability of the film under the cyclic strain loads and good film adherence to the substrate. Full article

Graphene-based materials are highly interesting in virtue of their excellent chemical, physical and mechanical properties that make them extremely useful as privileged materials in different industrial applications. Sonochemical methods allow the production of low-defect graphene materials, which are preferred for certain uses. Graphene nanosheets (GNS) have been prepared by exfoliation of a commercial micrographite (MG) using an ultrasound probe. Both materials were characterized by common techniques such as X-ray diffraction (XRD), Transmission Electronic Microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). All of them revealed the formation of exfoliated graphene nanosheets with similar surface characteristics to the pristine graphite but with a decreased crystallite size and number of layers. An exhaustive study of the particle size distribution was carried out by different analytical techniques such as dynamic light scattering (DLS), nanoparticle tracking analysis (NTA) and asymmetric flow field flow fractionation (AF4). The results provided by these techniques have been compared. NTA and AF4 gave higher resolution than DLS. AF4 has shown to be a precise analytical technique for the separation of GNS of different sizes. Full article