Key Engineering Materials Vol. 694

Abstract: In this research, the effect of PEG 2000 and Degussa P25 as additives on the characteristic of Ag-TiO₂ coating was reported. The TiO₂ coatings were produced via sol gel method using titanium (IV) isopropoxide (TTiP) as a precursor from solutions that contains additive and without additive. Seven layers of TiO₂ coating were deposited on specially made unglazed ceramic tiles produced from waste glass. All coatings were deposited using dip coating technique and were sintered at 500 °C. The TiO₂ coating was then immersed in an Ag nanoparticles solution before dried at 90 °C in an oven to form Ag-TiO₂ coating. The coating phases and coating morphologies were analyzed using GAXRD and SEM analysis, respectively. Results show that Ag-TiO₂ coating added with Degussa P25 additive exhibits a presence of more anatase and more homogenous microstructure which gives advantages for antimicrobial application as compared to others

Abstract: In cermet coatings with both ceramic and metal present, these can have very different corrosion potentials. Therefore, determination of the corrosion behaviour performance and its mechanism is crucial, especially in very acidic and alkaline environment. A conventional high velocity oxy-fuel (HVOF) tungsten carbide (WC)-Co coatings and a weld overlay tungsten carbide-nickel alloy cermet with carbide size of ~0.3-5 mm and ~50-140 mm respectively are used. Potentiodynamic tests are carried out in acidic and alkaline electrolytes: 0.5 M sulphuric acid, pH 0.45 and bentonite drilling fluid, pH 10.45. The behaviour of both coating types tested were pH dependent. The HVOF coating showed preferential dissolution of the binder in both electrolytes, with material loss being approximately twice as severe in the 0.5 M sulphuric acid compared to the alkaline drilling fluid. For the weld overlay coatings, with the larger carbide particles, the Ni₃B phase in the binder was preferentially removed in the acidic electrolyte whereas the Ni rich dendritic phase underwent preferential dissolution in the alkaline environment.

Abstract: Corrosion on the water pipelines can potentially cause substantial human and economic losses. This paper concentrates on corrosion observation on the underground pipeline material as a part of our continuous study regarding this work. The samples which is mild steel taken from actually used pipeline at the site. Mild steels have been investigated intensively as a promising pipe material for underground pipeline due to their advantages such as high availability, low cost, environmental friendliness and high resistance to corrosion. However, their practical application exposes them to the attack of corrosion related to the soil condition. In this study, microscopic observations were performed on the surface of pipeline material using scanning electron microscope (SEM) and energy-dispersive x-ray (EDX) technique in order to study the morphology and basic composition of the corrosion, respectively. Based on the observation and visual analyses, it was determined that the surface of the mild steel was affected by continuous exposure to moist soil, which leads to pitting type of corrosion.

Abstract: The purpose of this study is to investigate the effect of spent bleach earth (SBE) loading on the properties of green glass ceramic (GGC) composite. GGC was prepared using SBE and recycled soda lime silicate (SLS) glass. SLS glass was crushed then sieved to approximately 45µm. These GGC composites were formed with different weight fraction of SBE loading (40, 45 and 55 wt.%) by uniaxial dry pressing and sintered at different sintering temperature (700 °C, 750 °C and 850 °C). The sintering temperatures were selected based on Tg of the glass which is around 416 °C. The GGC specimens were analyzed in terms of its physical properties (density, water absorption and porosity), phase presence (X-Ray diffraction) and sintered microstructure (scanning electron microscopy). X-Ray diffraction pattern indicated that cristobalite, quartz and wallastonite phases were formed during sintering. It was found that the GGC with 45 wt.% of SBE loading sintered at 850 °C produced minimum water absorption which was 4.01% accompanied by density of 2.12 g/cm³ and a porosity of 8.49%. This shows that GGC composite produced with considerable higher amount of waste loading able to obtain acceptable physical durability.

Abstract: Lime sludge (LS) is a solid waste from lime making industry and normally disposed in landfill or recycled. LS has been studied as one of the raw materials in various ceramic productions such as bricks, ceramic tiles and glass-ceramics. In this study, LS was utilized in the preparation of bioactive glass using the 45S5 bioactive glass. The 45S5 bioactive glass contains SiO₂ (45 wt.%), Na₂O (24.5 wt.%), CaO (24.5 wt.%) and P₂O₅ (6 wt.%). It has the ability to bond with soft tissue and promote bone growth. The LS was combined with bioactive glass as a potential replacement of calcium carbonate (CaCO₃). The ratio between LS:CaO was varied (0:100, 25:75, 50:50, 75:25 and 100:0) to study the effect of LS weight percentage on the bioctive glass. The preparations of bioactive glasses involved batching, mixing, melting at 1400 °C, water quench and milling. LS was characterized using X-ray diffraction (XRD), while the fabricated glasses were characterized using particle size analyzer, XRD and scanning electron microscopy (SEM). The XRD results proved that the phase and chemical composition of bioactive glass were not affected by the addition of LS. The XRD and SEM results indicated that the addition of lime sludge in bioactive glass was effective to promote the formation of hydroxyapatite (HA) layer.

Abstract: Ceramic foams, a porous material with a gyroid structures, are becoming highly demanded for various applications such as heat insulation, bone implantation and filtration, because of their unique properties such as high specific surface area, high porosity and low heat transfer rate. In this study, the development of ceramic foam utilised white clay with a combination of precipitated calcium carbonate (PCC). The ceramic foam was successfully developed using this combination after the sample was sintered at 1250 °C for 2 hours holding time. The various compositions of PCC (10.0, 12.5, 15.0, 17.5, 20.0, 22.5 and 25.0 wt.%) affected the chemical composition and compressive strength of the ceramic foam. The chemical composition of ceramic foam was analysed by using X -ray fluorescence (XRF) and the result indicated that the PCC was successfully transformed into calcium oxide (CaO) after the sintering process. The mineralogical composition of the ceramic foam was evaluated using X-ray diffraction (XRD) and has shown the presence of mullite (3Al₂O₃.2SiO₂), gehlenite (Ca₂Al₂SiO₇) and anorthite (2CaAl₂Si₂O₈) after the sintering process. The scanning electron microscope (SEM) analysis showed that the presence of porosity on the strut of the ceramic foam. Meanwhile, the compressive strength of the ceramic foam increased from 0.03 to 1.31 MPa, which is directly proportional to the increased amount of PCC.

Abstract: A new approach of using industrial waste to produce synthetic mineral product was studied in this paper. A synthetic mineral product which is precipitated calcium carbonate (PCC) was synthesized by using ionic sucrose solution method, whereby sucrose solution acts as promoter to increase the production of the PCC. Carbide lime, a waste from acetylene gas industry was used as starting material and first dissolved in the sucrose solution. The concentrations of the sucrose solution were varied from 5 to 15 °Brix. The effect of the sucrose solution concentration was studied by using multiple characterization methods such as X-ray diffraction (XRD), X-Ray Florescence (XRF) and field emission scanning electron microscope (FESEM). The XRD and XRF results had proven that the synthesized PCC was calcium carbonate with > 98% purity. The morphologies of the PCC were observed by FESEM in which cubical shape was formed at 5 to 12 °Brix and grain shape at 13 to 15 °Brix. The distribution of the PCC particles was observed to be homogenous. The yield of the PCC increased as the Brix values increased.

Abstract: An investigation on the effects of hydrogen (H₂) gas dilution on the morphology and growth of carbon nanowalls (CNWs) decorated carbon nanotubes (CNTs) by hot-wire r.f. plasma enhanced chemical vapour deposition technique is presented. With the assistance of nickel nanoparticle catalyst, CNWs decorated CNTs formed only under the presence of 25% of H₂ gas, relative to the methane (CH₄) gas precursor. By varying the amount of H₂ incorporated with CH₄, the role of H₂ dilution in the development of CNWs decorated CNTs was studied. Based on the FESEM and HRTEM results, it is hypothesized that H₂ density and relative carbon radical concentration are the important parameters for the deposition of CNWs decorated CNTs. The effect of H₂ dilution on the formation of CNWs decorated CNTs is presented.

Abstract: This paper reports on the synthesis of iron oxide nanowires using thermal oxidation of iron. The α-Fe₂O₃ (hematite) and Fe₃O₄ (magnetite) were successfully formed using this method. The morphological observation was done through the FESEM, while the XRD, EDX and Raman spectroscopy were used to determine the physical and structural properties of the produced nanostructures. It was found that the peaks intensities relative to the hematite, increased with the extent of oxidation period. The growth and final morphology of hematite was significantly controlled by the heating duration. A surface diffusion mechanism for nano-hematite growth was then proposed to account for the growth phenomena of this nanostructured formation.

Abstract: Environmental pollution problem and depletion of petroleum reserves have driven the researchers to use non-edible oils as a low cost feedstock. This work represents the preparation of nano fluids using kapok (ceiba pentandra) seeds oil (KSO) and multi walled carbon nano tubes (MWCNTs). The present study consists of two stages. The first step is the extraction of KSO through Soxhlet extraction using n-hexane as a solvent. The second step is the mixing of extracted oil with carbon nanotubes using sonicator, with different time intervals, to develop nanofluids. The visualization technique was used by capturing photographs to evaluate the stability of the nanofluids. The photographs showed good agreement for the stability of nanofluids for more than 1 week. KSO and prepared nanofluids were characterized by using Fourier transformed infra-red spectroscopy (FTIR) and scanning electron microscopy (SEM).