Application of Rice Husk Ash as Thermal Insulation Materials

A low thermal diffusivity SiO2-based ceramic was fabricated by sintering Malaysia agricultural waste rice husk at 800 °C. This paper presents the effect of sintering temperatures on the phase transformation, microstructure and thermal diffusivity of rice husk ash (RHA) as a thermal insulating material. A series of SiO2-based ceramics were fabricated from rice husk via two sintering stages. Rice husk was pre-sintered at 700 °C and then ground into powder. The RHA powder was compacted into pellets and then re-sintered at a single temperature between 700 and 1400 °C. Sintering of the RHA induces phase transformation from amorphous silica to crystalline α-cristobalite, α-tridymite and β-tridymite. The thermal diffusivities of RHA were evaluated using the laser flash analysis technique. The results indicate RHA-800 °C has the lowest thermal diffusivity, which is 0.17 ± 0.1 mm 2 s −1 at 25 °C. The RHA particle morphologies were observed using a field-emission scanning electron microscopy. Low-frequency vibrational modes of silica such as lattice vibration were investigated using Fourier-transform infrared spectroscopy technique. X-ray fluorescence result indicated that RHA-800 °C contains ~90 wt % of SiO2

Investigation of the siliceous hydrogel phase formation in glass-ionomer cement paste

The microstructure evolution of a complex glass-ionomer cement (GIC) paste over the first 72 h of the cement setting reaction was investigated by small-angle neutron scattering (SANS) and infrared spectroscopy. GIC is a biocompatible material which is clinically used for dental fillings. In this study, GIC pastes were prepared, following the ISO9917-1:2007 cement preparation method, from medical grade poly(acrylic acid), SiO₂–Al₂O₃–P₂O₅–CaO–CaF₂ -based fluoroaluminosilicate glass and H₂O/D₂O solvent. During the setting reaction, polyacrylic acid attacks the fluoroaluminosilicate glass particles to form a siliceous hydrogel phase, glass core and hydrated polyacrylate matrix. The formation of the siliceous hydrogel structure and cross-linking of polyacrylate chains play important roles to harden the GIC. Infrared spectroscopy was used to identify the formation of the hydrogel phase and cross-linkage in GIC paste. In addition this paper reports SANS measurements for GIC pastes at different contrast conditions (H₂O:D₂O ratio) from the Bilby instrument at the Australian Centre for Neutron Scattering, ANSTO, Australia. The SANS data provide microstructure information for the hydrogel phase in GIC paste over the length scale of 10–5000 Å

Elastic moduli prediction and correlation in soda lime silicate glasses containing ZnO

Soda lime silicate glass (SLS) containing zinc oxide (ZnO) was prepared and its elastic properties through the principle of Rocherulle's model were investigated. Different density, dissociation energy and elastic moduli were calculated theoretically for each glass samples containing different weight percentage of ZnO and these values were compared with experimental results by using ultrasonic pulse echo technique. Thereafter, the values of elastic moduli (including Young's modulus, bulk modulus, shear modulus and Poisson's ratio), derived from experimental data of the glass were compared with those theoretically results calculated in term of Rocherulle's model. According to Rocherulle model, the value of Poisson's ratio decreased as weight percentage of ZnO in SLS glass increased and the elastic moduli tends differ to the experimental values and it was further discussed

Small angle neutron scattering study of a gehlenite-based ceramic fabricated from industrial waste

This paper presents a small angle neutron scattering (SANS) study of a novel porous gehlenite-based ceramic, synthesised from a homogeneous powder mixture of soda-lime-silicate (SLS) glass, α-alumina, calcite and calcium fluoride via solid-state sintering at 1200 °C. The products of sintering at single temperatures from 600 to 1200 °C are examined by X-ray diffraction (XRD). Sintering of the mixture below 1200 °C forms two intermediate phases (Na₂ CaSi₃ O₈ and Ca₄ Si₂ O₇ F₂ ). Nepheline and α-alumina are minor phases in the gehlenite-based ceramic fabricated through sintering at 1200 °C. The microstructure of the gehlenite-based ceramic is investigated using field-emission scanning electron microscopy (FESEM) and SANS at the Australian Centre for Neutron Scattering. This study also evaluated the specific surface area of the gehlenite-based ceramic (~3.0 m² cm⁻ ³) from quantitative analysis of SANS data

Association of maternal Vitamin D status with glucose tolerance and caesarean section in a multi-ethnic Asian cohort: the growing up in Singapore towards healthy outcomes study

10.1371/journal.pone.0142239PLoS ONE10111-16GUSTO (Growing up towards Healthy Outcomes

Effects of heat treatment on structure and thermal diffusivities of SiO₂-A1₂O₃-Na₂O-CaO-CaF₂ glass-ceramics from waste materials

Recycling waste materials into dental application is a developing field of study. Soda-lime-silica (SLS) glass and clamshell (CS) were used in this research to make dental glass-ceramics. The manufacture of glass-ceramics by using waste materials for dental industries can reduce a large amount of solid wastes produced daily. This research was focused on the phase transformations and thermal diffusivities of SiO2- Na2O-Al2O3-CaO-CaF2 glass-ceramics which made by different weight ratio of CS and CaF2 powders. This research is important to obtain an optimum composition and heat treatment temperature to improve the properties of glass-ceramic for dental applications. Two series of SiO2-Na2O-Al2O3-CaO-CaF2 mixture samples (SM1- SM4) and glass samples (SG1-SG4) were produced. The raw materials used in this research were SLS glasses, α-alumina (Al2O3) powder, CS and calcium fluoride (CaF2) powder. Both SLS glasses and CS were collected from waste products in food industries. The weight formula of the samples were (SLS)0.4 (Al2O3)0.3 (CS)0.3-x (CaF2)x , where x = 0, 0.1, 0.2 and 0.3. The SM1-SM4 were produced by mixing raw materials according to their weight ratio and followed by pressing them into pellet form. Heat treatments at 500-1200 ºC for 3 hours were carried out on these pellets to obtain crystalline phases. XRD, FTIR, TGA, DTA, FESEM, and thermal diffusivity tests were carried out on SM1-SM4. The SG1-SG4 were produced by rapid cooling of molten mixture powders which based on their weight ratio. The glasses obtained were ground into powder form and followed by pressed them into pellet form. Heat treatments at 500-1300 ºC for 3 hours were carried out on these pellets to obtain crystalline phases. The crystallized SG1-SG4 glasses after being heat treated were called as glass-ceramics. XRD, FTIR, DTA, FESEM, and thermal diffusivity tests were also carried out on SG1-SG4. The result shows that all the SM1-SM4 and SG1-SG4 consists of nepheline and gehlenite phases after heat treatment at high temperature. The nepheline phase is an important phase in various dental materials, especially for dental crown. The nepheline phase at lowest heat treatment temperature was found in SG3 at 800 ºC. The glass transition and crystallization temperatures of SG3 were 680 and 872 ºC respectively

The synthesis and microstructure characterisation of bioglasses, bioglass-ceramics and glass-ionomer cements for bone and dental restoration

This PhD thesis presents the synthesis and microstructure characterisation of Ca-fluoroaluminosilicate (CFAS) glasses, fluorapatite glass-ceramics and glass-ionomer cements (GICs) for bone and dental restoration. The first part of the thesis presents the crystallographic, chemical and thermal characterisation of starting waste materials. CO2-sequestration was exploited to convert aluminium cans to aluminas. The microstructures of aluminas were investigated using a SEM-EDX and SANS. The effects of heat treatment on the phase transformation of oyster shells and rice husk ash are also reported. The second part of the thesis includes the synthesis and microstructural investigations of 13 CFAS glasses. These are synthesised in parts from waste materials via melt-quench technique. The CFAS glass compositions are varied within the SiO2–Al2O3–CaO–Na2O–CaF2–P2O5 system. The microstructures of these glasses are studied using SANS, USANS and SAXS. The results provide microstructural information for the glass particles over a size range from 1 nm to 10 µm. The third part presents sinter-crystallisation of the CFAS glasses to fluorapatite glass-ceramics. The conditions to synthesise fluorapatite-mullite, fluorapatite-anorthite and fluorapatite-albite glass-ceramics are also established. The phase transformations of glass-ceramics are studied using PXRD, infrared spectroscopy, SANS and STA. The last part reports the chemical and microstructural evolution of GIC pastes during the cement setting reaction. GIC pastes are formulated from a mixture of CFAS glass, polyacrylic acid and water. The setting reaction of GIC pastes is investigated using in-situ infrared spectroscopy and SANS. The results showed the formation of cross-links within polyacrylate chains and the thickening of siliceous hydrogel layers surrounding the glass particles. The GICs acquired high mechanical strength (~60 MPa) after one month of setting, and performed as well as the commercial LG26 glass

An investigation of conventional machine learning approaches vs deep learning approaches in manufacturing context : bearing fault detection

In the realisation that ball bearing fault is the number one fault that most commonly occur in industrial applications and the potential hazard that it can bring, this paper aims to tackle the problem of bearing fault detection. With the recent development and boom of Deep-learning approaches in the machine learning space, there is an increasing focus on Smart manufacturing. In traditional machine learning approaches, feature engineering is the most crucial process and bearing fault detection has been heavily reliant on subject matter experts for curating suitable features for prediction. Deep-learning is an alternative method that does not require the feature engineering process. Deep-learning approaches are able to automatically learn features by modelling them as nested layers of abstraction of knowledge from the data itself. Convolutional Neural Network (CNN) is one of such Deep-learning approaches. In this paper, conventional machine learning approaches are compared to CNN in terms of their performances. For conventional machine learning approaches, the result of Fast Fourier Transformed (FFT) is being used as features for classification. For CNN, we will explore the claim of Deep-learning approaches in its ability to automatically learn features. Raw data will be fed to CNN after converting to a 2-dimensional grey image. The result ascertained that Deep-learning approaches are able to learn features automatically without the need of domain knowledge expertise. Besides, the result shows that Deep-learning approaches can greatly outperform conventional machine learning approaches.Bachelor of Engineering (Computer Engineering

Phase Transformations of α-Alumina Made from Waste Aluminum via a Precipitation Technique

Abstract: We report on a recycling project in which α-Al2O3 was produced from aluminum cans because no such work has been reported in literature. Heated aluminum cans were mixed with 8.0 M of H2SO4 solution to form an Al2(SO4)3 solution. The Al2(SO4)3 salt was contained in a white semi-liquid solution with excess H2SO4; some unreacted aluminum pieces were also present. The solution was filtered and mixed with ethanol in a ratio of 2:3, to form a white solid of Al2(SO4)3·18H2O. The Al2(SO4)3·18H2O was calcined in an electrical furnace for 3 h at temperatures of 400–1400 °C. The heating and cooling rates were 10 °C /min. XRD was used to investigate the phase changes at different temperatures and XRF was used to determine the elemental composition in the alumina produced. A series of different alumina compositions, made by repeated dehydration and desulfonation of the Al2(SO4)3·18H2O, is reported. All transitional alumina phases produced at low temperatures were converted to α-Al2O3 at high temperatures. The X-ray diffraction results indicated that the α-Al2O3 phase was realized when the calcination temperature was at 1200 °C or higher

Effects of calcination on the crystallography and nonbiogenic aragonite formation of ark clam shell under ambient condition

This paper presents a study of crystallographic evolution of disposed ark clam shell (ACS) after calcination at 400–1400°C which was kept at room temperature under ambient condition in Malaysia during nine months. A better understanding of hydration and recarbonation of ACS powder (≤63 μm) after calcination was discovered by PXRD and FTIR. The research focuses on the crystallographic transformation, biogenic calcite decomposition, and unusual atmospheric aragonite formation in ACS after calcination and atmospheric air exposure. Ex situ PXRD showed calcite present in ACS at ≤900°C. ACS transformed to pyrogenic fcc CaO at ≥800°C after three months. Long term atmospheric air exposure of decarbonized ACS caused nucleation of nonbiogenic aragonite, vaterite, calcite, and portlandite. However, in situ PXRD analysis of ACS at instantaneous temperature without cooling process does not indicate the presence of aragonite, vaterite, and portlandite crystals. FTIR spectra revealed CaO–CO2 bond in ACS dissociated with temperature (600–900°C) to form CaO and CO2. Ca–OH bond was also traced in FTIR spectra of ≥700°C. It resulted by hydroadsorption of CaO with H2O in atmospheric air