Materials Science Forum Vol. 1074

Abstract: In recent decades, polymer composites have gained significant interests within the research community due to its high strength-to-weight ratio. Its properties, such as low cost, lightweight, corrosion resistance, and impact resistance, make it desirable for both household and industrial applications. However, the reliability of the composite model with density influence is still challenging. In this study, experiments were carried out using epoxy systems of varying densities to fabricate oil palm empty fruit bunch (OPEFB) carbon nanoparticle composites to investigate the influence of matrix density on its Weibull modulus. It is found that the increase in matrix density increases the nanocomposite reliability. A Weibull modulus of 9.5, 82.2 and 183.4 were obtained for low, medium and high matrix density nanocomposites, respectively. Such findings would facilitate the development of particle-reinforced composites.

Abstract: In this paper, a series of polyvinyl alcohol (PVA) aerogels hybrid with cellulose nanocrystal (CNC) was successfully prepared using freeze-drying process. The influence of different fractions of CNC and crosslinking agent; glutaraldehyde (GA) on the mechanical of PVA/CNC hybrid aerogels property was evaluated by means of compressive strength. Results show that the mechanical property of hybrid aerogels has been improved with the addition of CNC and GA. Variation in the CNC and GA content also led to differences in the porous structure morphologies. Nevertheless, higher content of GA caused adverse effect to the strength of hybrid aerogel which associated to the excessive crosslinking and smaller number of pores formation as evident from scanning electron microscopy (SEM) analysis.

Abstract: In this work, hydroxyapatite ceramics were prepared from hydroxyapatite micropowder and nanopowder. The hydroxyapatite nanopowder was obtained from natural buffalo bone by using a high speed vibro-milling machine for 2 hour. The green compacted pellets of all HA powders were subsequently sintered at 1200, 1250, 1300 and 1350°C for 3 hour and then the physical and mechanical characterizations as well as microstructural evaluation have been carried out. It was found that the optimum sintering temperature were 1250°C by fabricated from nanopowder which gave the HA nanoceramic with the maximum bending strength of 78.6±2.6 MPa. This is about 200% higher than that of the sample which fabricated from HA micropowder.

Abstract: Abstract. This study investigates the synthesis, chemical, and physical properties of isothiocyanate poly(methyl eugenol) or IPME and thiosemicarbazide poly(methyl eugenol) or TPME. The IPME synthesis as a precursor was firstly carried out by reacting Methyl Eugenol (ME) with potassium hydrogen sulfate and potassium thiocyanate in chloroform solution at room temperature. The TPME was synthesized using the intermediate compound and hydrazine in an ethanol-based at 70 °C for five hours. The IPME and TPME were observed by FTIR, dissolution test, SEM-EDX, XRD, GCMS, and LCMS-MS. The methyl eugenol : HSCN = 1:10 (mmol) ratio for 30 hours of reaction time was determined for the optimum IPME production. FTIR spectra consecutively identified specific wavenumbers at around 2049 cm^-1 and 3488 cm^-1 for isothiocyanate and thiosemicarbazide functional groups. IPME and TPME compounds were entirely soluble in DMSO and slightly soluble in n-hexane. SEM-EDX study showed that IPME had a denser surface than TPME; however, they all consisted of Carbon, Oxygen, Nitrogen, and Sulfur elemental composition. XRD analysis indicates that these two products were high and moderate crystalline compounds. The GCMS analysis showed m/z 503 for IPME, predicting that IPME was a copolymer composed of one methyl eugenol isothiocyanate molecule and two methyl eugenol bonded. The LCMS-MS chromatogram with m/z 449 for TPME proved the occurrence of a polymerization reaction.Keywords: Isothiocyanate, methyl eugenol, thiosemicarbazide.

Abstract: The preparation of hydroxyapatite nanopowders in this experiment demonstrated a novel method for milling of animal bone powder to nanoparticle size prior to calcination. The buffalo bone was deproteinized by hot water before it was dried at 200°C for 24 h. The resulting product was crushed into small pieces and milled in a ball mill pot for 24 h. After that, the bone powders were ground by a high speed vibro-milling method with various milling times. Characteristics of the powders were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS). The experimental results of SEM showed that the shape of the buffalo bone particles was regular with the particle size less than 100 nm from using high speed vibro-milling time of 2 h. The buffalo bone nanopowder were calcined at various temperatures. XRD and SEM results showed that material obtained is a HA according to JCPDS file-9432 pattern in a 1.66 Ca/P molar ratio at calcination temperature of 600°C. The average diameter of powder less than 100 nm.

Abstract: Taguchi based optimization of natural frequency of perforated stiffened hypars is performed to consider the role of fibre lamination, width/thickness ratio of shell and position of perforation centre along x- and y-direction. Natural frequency of stiffened shell is obtained for simply supported boundary condition using finite element procedure based on L27 orthogonal array (OA) considering three settings of each parameter. Main effect plot is analyzed to identify the significant parameters. Natural frequency becomes maximum for a combination of 45⁰ fibre lamination, width/thickness value of 20 and perforation centre position (0.4, 0.4). Interaction graphs identify the interaction parameters. ANOVA study provides the significant contribution of the parameters considered here. Present analysis identifies width/thickness as the most significant factor and other parameters yield very little significance while no interaction is found to be significant. Width/thickness value of shell yields major (98.64%) contribution to natural frequency and other factors yield very little significance. Residual analysis for natural frequency and confirmatory test validate the present study. S/N ratio gets improved by 38.3% at optimal condition compared to the initial parameter setting.

Abstract: The present study discusses the fabrication of non-lead ceramic/polymer composites employing (Na_1/2Bi_1/2)TiO₃ (NBT) ceramic powder as a filler and poly(vinylidene fluoride); PVDF as a polymer matrix. The NBT (volume fraction, ϕ = 1) ceramics were synthesized using the conventional mixed-oxide method followed by the high-energy ball milling method whereas (1-ϕ)PVDF/ϕ(Na_1/2Bi_1/2)TiO₃; 0 ≤ ϕ ≤ 0.3 composites were prepared from a melt-mixing process. It was observed that the real and imaginary parts of dielectric permittivity, ac conductivity, and longitudinal piezoelectric charge coefficient increase with the increase in NBT-content. Different dielectric mixing models were presented to determine the effective complex permittivity of the composites. Five dielectric mixture equations have been chosen to test the acceptability of experimental data. It was revealed that theoretical models as given by Bruggman, Rother-Lichtenecker, and modified Rother-Lichtenecker show good agreement with the experimental results of filler-concentration dependent alteration of effective relative permittivity and loss factor of the PVDF/NBT composite. A mathematical model of first-order exponential growth has also been proposed, which fitted excellently the experimental data (r² > 0.998).

Abstract: The X-ray diffraction, microstructure, impedance, electric modulus, and ac-conductivity of Ba(Fe_1/2Ta_1/2)O₃–(Na_1/2Bi_1/2)TiO₃ solid-solutions were studied utilising a traditional high-temperature mixed-oxide technique. The phase-formations of the solid-solutions were determined utilising X-ray data, while SEM micrographs revealed a non-uniform dispersion of grains in the sample of unequal size (~1 – 20 mm). In all of the developed solid-solutions, the frequency (1Hz - 1MHz) dependence of imaginary and real parts of electric impedance in the temperature region of 50 and 500°C showed the NTCR character and hopping type of electrical conduction. The modulus spectrum variation was intrigued by the hopping mechanism for charge transport (temperature-dependent) in the samples with non-Debye type of behaviour. Besides, the low electrical conductivity of these solid-state solutions makes them ideal for industrial applications, particularly as capacitors.

Abstract: Low weight is one of the most important factors in the design process of road and flight vehicles. The design engineers are careful with regards to the weight decrease without thinking twice about the primary strength. The composite is a lightweight material that has decent underlying properties and it is generally utilized. Fiber-supported polymer composites assumed a prevailing part for quite a while in an assortment of uses for their high explicit strength. The current work portrays the turn of events and the portrayal of another arrangement of GFRP. Experiments are carried out to study the effect of the addition of fillers by varying their percentages. The present work focus on the effect of the fillers on properties of Glass fiber epoxy laminates with aluminum oxide and magnesium hydroxide powders as the fillers. In the present work, fabrication and experimental investigation on unidirectional glass epoxy composites are carried out. Initially, glass fiber reinforced polymer laminate fabricated without filler material, hand layup followed by vacuum bagging methods are used . Then, by adding Aluminium oxide and Magnesium hydroxide as a filler material with different percentages like 5%, 10%, and 15% by weights and laminates are fabricated and experimental investigation is conducted to study their mechanical behavior. The comparative studies on the laminates are carried out and the obtained results are analyzed and those are quite interesting.