Othman Mamat

Studying the Effects of Adding Silica Sand Nanoparticles on Epoxy Based Composites

The research about the preparation of submicron inorganic particles, once conducted in the past decade, is now leading to prepare polymer matrix composite (PMC) reinforced with nanofillers. The objective of present research is to study the modified effects of reinforcement dispersion of nanoparticle silica in epoxy resin on the physical properties, mechanical and thermal behaviour, and the microstructure of resultant composites. Stirrer mixing associated with manual mixing of silica sand nanoparticles (developed in our earlier research) (Ahmad and Mamat, 2012) into epoxy was followed by curing being the adopted technique to develop the subject nanocomposites. Experimental values showed that 15 wt.% addition of silica sand nanoparticles improves Young’s modulus of the composites; however, a reduction in tensile strength was also observed. Number of holes and cavities produced due to improper mixing turn out to be the main cause of effected mechanical properties. Addition of silica sand nanoparticles causes a reduction in degree of crystallinity of the nanocomposites as being observed in differential scanning calorimetry (DSC) analysis.

Recent Progress on the Dispersion and the Strengthening Effect of Carbon Nanotubes and Graphene-Reinforced Metal Nanocomposites: A Review

ABSTRACT This article reviews the available literature published to date on the reinforcement of metals with carbon-nanofillers (CNTs and graphene), and also offers a specific focus on issues related to the mechanical and tribological properties of nanocomposites. Carbon-nanofillers (later denoted by C-nanofillers) are known to have extraordinary mechanical properties and multifaceted characteristics and are ideal candidates for the reinforcement of metals for numerous applications. However, their incorporation for practical applications has been challenging researchers for decades. The most important issue is uniform dispersion due to sizeable surface differences between carbon-nanofillers and metals. Other concerns are structural integrity, wetting with metals, and interfacial connections. Nanocomposite applications can only be effective when these challenges are properly addressed and overcome. Section 1 assesses the importance of C-nanofillers and expressly highlights current research efforts to optimize dispersion in different metals along with processing techniques in section 2. The authors give special attention on C-nanofillers reinforcement contribution to enhanced mechanical strength of metals presented in section 3. C-nanofillers dispersion evaluation tools are highlighted in section 4. Authors also focuses on C-nanofillers role and factors directly associated with metal nanocomposite strength, as reported in the literature. Particular consideration is also given to knowledge sharing of attendant strengthening mechanisms along with contribution reported for empirically derived models used to predict strength. Section 6 solely dedicated to the tribological aspects of C-nanofillers reinforced metallic nanocomposites. Lastly, future recommendations and works need attention is summarized.

Estimating young’s modulus of single-walled zirconia nanotubes using nonlinear finite element modeling

The single-walled zirconia nanotube is structurally modeled and its Youngs modulus is valued by using the finite element approach. The nanotube was assumed to be a frame-like structure with bonds between atoms regarded as beam elements. The properties of the beam required for input into the finite element analysis were computed by connecting energy equivalence between molecular and continuum mechanics. Simulation was conducted by applying axial tensile strain on one end of the nanotube while the other end was fixed and the corresponding reaction force recorded to compute Youngs modulus. It was found out that Youngs modulus of zirconia nanotubes is significantly affected by some geometrical parameters such as chirality, diameter, thickness, and length. The obtained values of Youngs modulus for a certain range of diameters are in agreement with what was obtained in the few experiments that have been conducted so far. This study was conducted on the cubic phase of zirconia having armchair and zigzag configuration. The optimal diameter and thickness were obtained, which will assist in designing and fabricating bulk nanostructured components containing zirconia nanotubes for various applications.

Process Parameters Optimization of Silica Sand Nanoparticles Production Using Low Speed Ball Milling Method

Experiments are designed using Taguchi method to find the optimum parameters for silica sand nanoparticles production using low speed ball milling. Orthogonal array and signal-to-noise ratio are applied to study performance characteristics of machining parameters which are the ball to powder weight ratio, volume of milling jar, and rotation speed. Results obtained from signal-to-noise ratio analysis showed that ball to powder weight ratio is the most influential parameter.

Influence of surfactant type on the dispersion state and properties of graphene nanoplatelets reinforced Aluminium matrix nanocomposites

ABSTRACT Graphene dispersion in aluminium matrix is a critical concern for the attainment of composite improved mechanical and tribological properties which hinders broad applications of Al nanocomposites. Herein, graphene nanoplatelets (GNPs) dispersion in Al matrix achieved by colloidal processing, i.e., combining sonication and surfactant dispersing aid. In this work, the performance of the two types of surfactant (anionic, sodium dodecyl benzene sulfonate (SDBS), and nonionic polymeric, ethyl cellulose (EC)) were evaluated for effective GNPs dispersion in a solvent and Al matrix. Surfactant assisted GNPs solvent dispersion characterized through sedimentation test and UV-vis spectroscopy to optimize surfactant concentration. Density, hardness, wear properties and microstructural characterizations of GNPs/Al powder and sintered discs were performed to gauge the effect of surfactant type. It was found that surfactant addition enhances dispersion ability of GNPs than neat GNPs but at low GNPs fractions. The results show that EC assisted GNPs/Al nanocomposites of 0.5 wt% GNPs concentration has shown an increase in hardness (31%) and reduce wear rate (98%). Whereas, 0.3 wt% SDBS assisted GNPs/Al nanocomposites shown maximal increases in hardness (18%) and reduce wear rate (98%) as compared to pure aluminium, respectively. Conclusively, it has been revealed that polymeric EC based surfactant GNPs owing to steric repulsion shows better dispersion effect resulting in high density and improved wear resistance and performed better than SDBS based surfactant GNPs in Al matrix.

Thermal shock and fatigue behavior of pressureless sintered Al2O3–SiO2–ZrO2 composites

The thermal shock and fatigue behavior of pressureless sintered Al2O3–SiO2–ZrO2 (ASZ) composites was studied. The influence of the thermal shock and fatigue on the strengthening response of ASZ has been investigated by measuring the strength retention and microstructural changes. The magnitude of the flexural strength and fracture of the ASZ has been compared with that of the monolithic Al2O3 (A) and Al2O3–ZrO2 (AZ) composites under the same experimental conditions. Results indicated that the ASZ composites possess the highest resistance against thermal shock and fatigue, in comparison with A and AZ. The improvements were attributed to the enhancement in the fracture toughness of ASZ and the presence of multi-phase reinforcement.

A novel method for high volume production of nano silica from rice husk: process development and product characteristics

One problem with research on nanoparticles production is the lack of scalability from laboratory to levels of production necessary for commercial or industrial applications at low cost. Several methods, which often involve the use of chemicals, have been employed to produce silica nanoparticles from rice husk, but output levels cannot be said to meet industry requirements. This paper reports the design of a novel method – hydro thermo-baric processing, which was used to produce high purity silica from rice husk. The process factors were optimised using the method of factorial design of experiments. The produced nanoparticles were characterised using XRF, XRD, FESEM and EDX. XRD results show that the silica produced, which by XRF analysis had approximately 99% purity, is amorphous in nature. FESEM images showed that the particles have nanometric size. However, EDX results show an increase in residual carbon in the silica, with increase in the processing temperature.

Numerical modelling of non-isothermal flow of fibre suspensions: prediction of fibre orientation in three-dimensional cavities

The most important phenomenon observed in fibre suspensions is flow induced fibre orientation. Fibre size is the key parameter in prediction of fibre orientation which in turn describes the microstructures of injection moulded parts. This paper focuses on developing a three-dimensional numerical model for the analysis of fibre orientation prediction incorporating the effect of fibre size distribution using the finite volume method FVM. The flow was considered to be incompressible, and behaves as non-Newtonian fluid flowing under non-isothermal condition. The hybrid closure model of Advani and Tucker was used to approximate the evolved fourth order orientation tensor. To validate the developed simulation model, several cases were modelled and compared with available experimental data for rectangular and cylindrical geometries. The simulation results showed that they are in good agreement with the experimental data. Hence, the numerical model could assist in decisions regarding the design of composite products.

Modelling the Elastic Constants of Cubic Zirconia Using Molecular Dynamics Simulations

Analysis of structural and mechanical properties of cubic zirconia was conducted using a simulation code (GULP) that is based on the concept of energy minimization. Some mechanical properties of zirconia were computed such as elastic constant tensors, shear modulus, bulk modulus, Youngs modulus and others along the lattice planes. The stiffness constants obtained (C11, C22 and C33) were equal, implying that zirconia is flexible in all directions of the lattice plane. The predicted bulk modulus was 285 GPa with the shear modulus ranging between 78 and 105 GPa. The Youngs modulus of 577 GPa indicates higher ductile behavior as confirmed by the compressibility of 0.0035. The Poissons ratio with values ranging from 0.16 to 0.31 may indicate high anisotropy. Other acoustic features related to mechanical properties of zirconia such as velocity wave ratio, stress matrix dielectric constants and others were also analyzed. All estimations obtained show good agreement to recent measured properties of zirconia.

Hydro Thermo-Baric Processing and Properties of Nano Silica from Rice Husk

Several processing methods have been used to obtain silica from rice husk with a persistent problem of lack of scalability from laboratory scale to levels of production necessary for commercial or industrial applications, at low cost. To address this draw-back, a novel method- hydro thermo-baric process, was developed and used to process high purity silica from rice husk. Since the suitability of rice husk silica in a given application is dependent on the nature of its structure and morphology and the two parameters are affected by the processing methods used in obtaining the silica, this paper reports the preliminary studies done on the silica obtained from this novel method using XRF, XRD, FESEM and EDX. XRD results show that the silica produced, which by XRF analysis had purity approaching 98%, is amorphous in nature. FESEM images showed that the particles have nanometric size. However, EDX results show an increase in residual carbon in the silica, with increase in the processing temperature. BET analysis showed an increased surface area from 21.42m2/g to 133.94m2/g for the untreated and treated samples, respectively.