Fracture Toughness of Poly (Methyl Methacrylate)/Hydroxyapatite Denture Base Composite: Effect of Planetary Ball Milling Mixing Time

Hydroxyapatite (HA) has great potential as a reinforcing filler for poly (methyl methacrylate) (PMMA) denture base materials. Nevertheless, filler particles need to be homogeneously distributed throughout the PMMA particles to get the maximum benefit from using the filler. Therefore, the physical mixing of the powder components (PMMA and the filler) is strongly preferred to provide the required dispersion of the filler in the matrix. However, conventional techniques that have been tried, such as hand mixing and stirrer mixing techniques, were not effective. Therefore, the current study was designed to experimentally investigate the effect of different mixing times on the fracture toughness of PMMA/HA using a developed ball milling method. In this study, heat cured PMMA reinforced with 15 wt% HA ceramic powder was ground for different times (i.e., 10, 20, 30, and 40 min) via the technique of planetary ball milling (PBM). The ground powder mixtures were used for the fabrication of denture base testing samples. The particle size and distribution of the PMMA/HA composites after milling for several times were determined by the laser light scattering technique. The X-ray diffraction (XRD) patterns of the PMMA/HA composites were obtained. However, no new phase was observed. The effects of mixing time using the PBM technique on the fracture toughness were investigated. The effect of mixing time on the microporosity (voids) on the fractured surface of PMMA/HA was studied with field emission scanning electron microscopy (FESEM). Within the limitation of the current study, 30 min is considered the optimum mixing time for the tested PMMA/HA composite.

Nanomagnetite Extraction from Iron Sand Prepared by Mechanical Alloying Method

In this paper, the magnetic properties of Aceh iron sand was studied. The iron sand was collected from the Syiah Kuala coastal area, Banda Aceh and obtained by mechanical alloying method using planetary ball milling. The mineral compositions were investigated by XRD and XRF analysis tests. The XRF test showed that the sand mostly contain magnetite, Fe3O4 (85.80%) in association with other impurities of SiO2, TiO2, Al2O3 and some others minor minerals. Compare to XRD results, the phase compositions were mainly magnetite (Fe3O4). So, it is consistent with the XRF data. The electron microscopy observation (SEM) showed the fine crystalline structure and the main morphology was micro-crystalline in agglomerate forms. Furthermore, the magnetic properties after 20 hours milling showed the increasing in the coercivity (Hc) and remanent (Br), while the magnetic saturation (Ms) was decreased. This behavior can be explained that nano-Fe3O4 phase after the milling process plays an important role in the magnetic properties of iron sand.

Investigation of the Cause-Effect Relationships between the Exothermic Reaction and the Microstructures of Reactive Ni-Al Particles Produced by High Energy Planetary Ball Milling

Reactive particles consisting of nickel and aluminum represent an adaptable heat source for joining applications, since each individual particle is capable of undergoing a self-sustaining exothermic reaction. Of particular interest are particles with intrinsic lamellar microstructures, as they provide large contact areas between the reactants nickel and aluminum. In this work, the exothermic reaction as well as the microstructure of such lamellar reactive particles produced by high energy planetary ball milling were investigated. Based on statistically designed experiments regarding the milling parameters, the heat of reaction was examined by means of differential scanning calorimetry (DSC). A statistical model was derived from the results to predict the heat of reaction as a function of the milling parameters used. This model can be applied to adjust the heat of reaction of the reactive particles depending on the thermal properties of the joining partners. The fabricated microstructures were evaluated by means of scanning electron microscopy (SEM). Through the development of a dedicated SEM image evaluation algorithm, a computational quantification of the contact area between nickel and aluminum was enabled for the first time. A weak correlation between the contact area and the heat of reaction could be demonstrated. It is assumed that the quantification of the contact areas can be further improved by a higher number of SEM images per sample. The findings obtained provide an essential contribution to enable reactive particles as a tailored heat source for joining applications.