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An investigation was conducted to explore the optimum composition to fabricate a zinc silicate glass substrate for optoelectronic device applications. The composition was determined based on the empirical formula (ZnO)x-(SiO2)1-x, where x = 0.40, 0.50, 0.60 and 0.70 wt%, which was prepared by the conventional melt quenching technique. The focus is on characterizing the physical and structural aspects as well as the optical properties of the glass substrate. The physical properties of zinc silicate samples were assessed using the densitometer and their physical appearance. In addition, the materials' amorphous and glassy characteristics were verified using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques. Finally, ultraviolet–visible (UV–Vis) spectroscopy and photoluminescence spectrometer were used to study the optical properties of samples. The density of the samples was observed to increase from 2805 to 3878 kg/m3 as the percentage of ZnO in the glass composition increased. X-ray diffraction analysis indicated the absence of sharp peaks in the samples containing up to 0.60 wt% of ZnO, suggesting the presence of an amorphous phase. Furthermore, the results of this study indicate that ZnO-SiO2 glass substrate samples favor direct forbidden transitions, with an increase in ZnO leading to higher absorption and consequently a lower band gap. The photoluminescence spectrum showed blue light emissions at 422 nm, associating with the variation of band gaps in the ZnO phase. Overall, from the interesting results achieved, this zinc silicate-based composite material at 0.60 wt% ZnO can be a potent candidate in optoelectronic applications, among other concentrations used in this study.

Eu3+ incorporated zinc-borosilicate glass was synthesized using melt-quenching method. XRD and FTIR verified the amorphous nature of the samples. The absorption spectra indicate the Eu3+ ions in the UV-visible region at ∼394 nm. The direct and indirect band gap decrease from 5.152 eV to 5.082 eV and 4.133 eV to 3.837 eV, respectively. Meanwhile, the refractive index decrease from 2.145 to 2.202, while the Urbach energy ranges from 0.682 eV to 0.733 eV. All the samples have a good transmission percentage at 70–75%. Under the excitation of 400 nm, the intensity of the PL spectra increased when the Eu3+ dopant increased. The optimum content for Eu3+ incorporated ZnO–B2O3–GB glass is 3 wt.% among the other Eu3+ content (0, 1, and 2 wt.%) in this work. The reddish-orange emission at 612 nm (5D0 → 7F2) indicates the most intense emission and the CIE chromaticity coordinates imply in the reddish-orange region.

Non-destructive pulse-echo ultrasonic testing was conducted to measure ultrasonic parameters, i.e. longitudinal velocity (Vl), shear velocity (Vs) and attenuation coefficient (α) in Al–Al2O3 nanocomposites. Elastic constants were also determined using the relationship between Vl and Vs. The aim was to reveal the correlation between ultrasonic parameters and the microstructural features of Al–Al2O3 nanocomposites. The effect of addition of Al2O3 nanoparticles on the Vl and Vs velocities is mainly attributed to variation in the elastic modulus of Al–Al2O3 nanocomposites. Both Vl and Vs velocities and Young's modulus (E) were found to vary approximately in linear fashion with the increase of Al2O3 content. A considerable effect of milling process on Vl and Vs velocities was revealed, where they increase by increasing the milling time. The increment of Vl and Vs is owing to refinement of Al particles, homogenous dispersion of Al2O3 and particularly reducing porosity by proceeding milling time. In addition, increasing of Al2O3 content, better dispersion uniformity of Al2O3 and refinement of Al particles contribute to increase α values. Elastic constants were found to vary in the same manner as ultrasonic velocities. Interestingly, the improvement in E values by increasing Al2O3 content and milling time is attained, while the ductility did not change significantly.

Hetrometal oxides of (1 − x)Al2O3/xPbO2 (NPs) nanoparticles with different PbO2 content (x = 0, 0.3, 0.4, 0.5, 0.6 and 0.7) have been prepared by irradiation method. The NPs powder has been checked by X-ray diffraction (XRD). XRD measurements affirmed the presence of both pure NPs and nanocomposites of (1 − x)Al2O3/xPbO2 NPs with different PbO2 contents. The calculated structural parameters which using the experimental result of XRD charts to give a complete image of these measurements. Moreover, the results using FLUKA code showed that the values attenuation coefficient (μm), high effective atomic number (Zeff) and neutron shielding parameters increase as the lead dioxide increase in the Al2O3/PbO2 samples. While the values of half-value layer (HVL) and mean free path (MFP) decrease with increasing PbO2 content. The investigated shielding features of the chosen Al2O3/PbO2 would be advantageous for exposure control.

An apatite-mullite glass ceramics composition derived from clam shell (CS) and soda lime silicate (SLS) glass has been fabricated from a heat treatment process of composition, [xCaF₂⋅(45−x)SLS⋅15CS⋅20Al₂O₃⋅20P₂O₅], where x is 5, 10, 15 and 20 (wt%). The result concluded that the Ca and Si elements were found in the CS and SLS glass respectively as a major weight composition, thereby promoting the use of waste materials in the manufacture of glass ceramic samples. Besides, the CaF2 addition lowers the glass transition temperature (Tg) and crystallisation temperature (Tc) of the glass composition. The density and percentage of the linear shrinkage of the samples differs with the addition of CaF₂ and various heat treatment temperatures. For the structural properties' analysis, the formation of fluorapatite with a needle-like microstructure and mullite phase was enhanced with a higher CaF₂ content, while the growth of the anorthite phase was observed to occur at a higher heat treatment temperature. Generally, the addition of a high CaF₂ content with the help of heat treatment in apatite-mullite glass ceramics composition greatly promotes the crystallisation of the fluorapatite phase, which is crucial for denture glass ceramics.

This research attempts to propose the fabrication and characterization of highly amorphous zinc silicate glasses derived from zinc oxide (ZnO) and white rice husk ash (WRHA). Three zinc silicate glasses were produced based on empirical formula (ZnO)x(WRHA)1−x where x = 0.50, 0.55 and 0.60 wt.% by using melt-quenching methods. When ZnO increased, the transparency of the three glasses increased. Meanwhile, X-ray diffraction (XRD) analysis of the zinc silicate glasses revealed that the glassy state of the zinc silicate glasses increased along with the increment of ZnO, and at lowest ZnO (0.50 wt.%), the presence of silicon dioxide (SiO2) peak were observed showing uncomplete melted of silica. Additional vibrational band due to the presence of tridymite was found in the Fourier transform infrared spectroscopy (FTIR) at lowest ZnO content supporting the XRD result while other glasses showed the formation of zinc silicate glasses with the presence of SiO4 and ZiO4 vibrational band. The zinc silicate absorption also increased as the ZnO increased as a result from the formation of non-bridging oxygen (NBO's). Hence, optical band gap of zinc silicate glasses was decreased from 4.35 to 4.23 eV as the ZnO increased due to increment of NBO's. All zinc silicate glasses showed three different emission peaks which is at 535, 596 and 728 nm correspond to green, yellow and red emission respectively. This luminescence properties of zinc silicate were attributed to the defect inside the ZnO particle.

The radiation shielding effects and elastic properties of adding lead (Pb) and bismuth (Bi) to glasses was analyzed. Six different glasses, coded as G1-G6, were simulated with varying compositions of bismuth oxide and lead oxide, with G1 having the lowest density and G6 having the greatest. MCNP-5 code was used to calculate the mass attenuation coefficient, half value layer, tenth value layer, and mean free path of the glasses, the latter of which was compared with other radiation shields. These parameters were investigated between 0.015 MeV and 15 MeV. The bond compression model was utilized to analyze various parameters that describe the elastic properties of the glass samples. From the ultrasonic wave measurement result, the substitution of PbO and Bi2O3 which working as a network modifier towards SiO2 glass systems would break up the Si–O–Si bonds along with all the formation of non-bridging oxygen's which give the impact in the elastic moduli analysis of the glasses.

The influence of boron oxide on glass-forming ability, phase transformation, and optical properties of new zinc-boro-soda-lime-silicate (ZBSLS) glass system with formulation 60–x(ZnO)x(B2O3)40(SLS) where x = 0, 1, 5, 10 and 15 wt.% using the conventional melt-quenching technique was comprehensively studied. The glass powder samples were subjected to true density measurement using Helium Pycnometer. Besides, the XRD and FTIR spectroscopy was used to examining the phase and structural rearrangement in the ZBSLS glass system. The XRD result emphasizes the glass samples (G3, G4, and G5) in amorphous nature when boron concentration is more than 5 wt.% in the ZBSLS glass matrix. Also, the UV–Vis spectra were observed within 200–800 nm. At that point, the data from optical absorbance was converted to justify the optical band gap energy using Mott and Davis theory. The optical band gap energy show increment behavior from 4.35 to 5.25 eV for direct allowed transition and 3.25–4.30 eV for indirect allowed transition with the progress of boron concentration, respectively.

This study was conducted to synthesize foam glass-ceramic using SLS glass as a precursor; eggshell (ES) as a foaming agent and investigated the effect of sintering temperature on the crystal growth, microstructure and mechanical properties of the final product. The samples undergo the sintering process at different temperatures such as 700, 800 and 900 °C for 60 min with the heating rate of 10 °C/min. The structural properties were studied by XRD, FTIR and FESEM measurement. The cristobalite (SiO2) and wollastonite (CaSiO3) phases were identified after the sintering process and their microstructure was recorded by the FESEM micrograph. The physical properties of the samples were measured by average density measurement, linear expansion and compressive strength. The lowest density measurement using the Archimedes principle was achieved by 0.421 g/cm3 with the highest volumetric expansion at 92% after the sample sintered at 800 °C. Good correlations between porosity, mechanical strength and crystal phase were observed. The invention of foam glass-ceramics from waste materials can be applied as a potential building insulation material that gives benefit to the environment and energy usage.

Glass Ionomer Cement (GIC) is produced from an acid-base reaction between various type of alkaline glass powder and polymeric acid. In this research, calcium fluoro-alumino-silicate (CFAS) glass was derived from waste materials such as soda-lime-silica (SLS) glass and clam shell (CS) which are sources of silica and calcium oxide respectively. The polyacrylic acid (PAA) is used to produced mobile carboxyl group and then, react with metal ions on the surface of CFAS glass. To study the influence of ageing time on physical, structural and mechanical properties of GIC, deionized water was used as a soaking medium. The density results increase throughout the ageing time from 7–28 days. The density of GIC at 7 days shows 1.622 g/cm3 and increasing to 1.789 g/cm3 at 28 days. However, the molar volume shows the opposite action comparing with the density of GIC. The molar volume shows continue decreasing from 357.63–324.25 cm3 mol−1. From the XRD result, GIC was indicating amorphous structure during ageing range between 7–28 days. FTIR analysis shows this phenomenon occurs due to the deformation of Si−OH bonding and formation of Si-O-Si simultaneously in the presence of water which is influence the mechanical strength of GIC. The mechanical properties of GIC increase by ageing time through the compressive test from 42.23–50.28 MPa. Thus, the observed results in this study promise the GIC derived from waste materials have a high potential in dental application due to excellence structural and mechanical properties against ageing.

The effect of three different initial alkaline pH values (pH= 8, 9 and 10) in synthesised hydroxyapatite (HA) via a wet chemical precipitation approach was investigated. Waste ark clam shells (ACS) were used in this work as a source of calcium oxide in order to utilise waste materials in the production of synthetic Hydroxyapatite (HA). The HA was treated at different sintering temperature from 200 to 1000 °C to study the effect on the physical, the structural properties, the phase formation, the Vickers microhardness and the molar ratio of calcium to phosphate (Ca:P). From the results, the crystallite size and density of the HA obtained were increased as the sintering temperature increased. However, the appearance of biphasic HA and β-tricalcium phosphate (β-TCP) was detected at pH 9 with 1000 °C, but did not occur at pH 8 and 10. In addition to the obtained results, it was clearly identified that the formation of β-TCP in the HA phase is related to the initial pH value, sintering temperature and Ca:P ratio. The Vickers microhardness showed that the single-phase HA was the hardest one compared to the biphasic HA/β-TCP. It shows the optimal value of the Vickers microhardness for the single-phase HA with a pH 10 at 1000 °C is 4.15 MPa.

A study on the effect of sintering temperature to the physical and structural of Alumino-Silicate-Fluoride (ASF) glass ceramics fabricated from clam shell (CS) and soda lime silicate (SLS) glass is conducted through conventional melt-quench technique. ASF glass ceramics composition with 25SLS-20CS-20P2O5-20Al2O3-15CaF2 by weight percentage is analysed by using Energy X-ray (EDX), density (ρ), linear shrinkage, X-ray Diffraction (XRD), Fourier Transforms Infrared (FTIR) and Field Emission Scanning Electron Microscopy (FESEM). High content of Ca and Si in CS and SLS glass respectively promote the use of waste materials in production of ASF composition. The density and linear shrinkage of the samples varies with sintering temperature. Besides, XRD results showed that fluorapatite (Ca5(PO4)3F) is a main phase existed in all samples meanwhile FTIR confirmed the presence of silica and also the formation of CaP phase in the composition. FESEM analysis showed the increasing of grain size and formation of needle-like microstructure known as fluorapatite when sintering temperature increase. Overall results promoted the ASF glass ceramics samples produced from waste materials as a high potential candidate for dental application. Keywords: Alumino-Silicate-Fluoride composition, Clam shell, Soda lime silicate glass, Sintering, Fluorapatite

This paper reported the formation of biphasic hydroxyapatite, (HA) and β-tricalcium phosphate, (β-TCP) sintered at various sintering temperature from waste material. The phase stability of HA ceramic was investigated by imposing the high sintering temperature in order to study the transformation of the single phase of HA to biphasic HA/β-TCP ceramic. The evolution microstructure of HA and biphasic HA/β-TCP ceramic was studied at various sintering temperature reach up to 1400 °C. The single phase of HA was observed from 200 to 1200 °C and the secondary phase β-TCP appears due to the decomposition of partial HA at 1300–1400 °C. The optimum temperature for a single phase of HA was identified after sintering at 1200 °C to produce HA with high mechanical hardness about 5.11 GPa. This is clearly related to the phase stability and morphology of HA. The particles size of HA as-synthesized were recorded in nano range scale at ∼9 to 20 nm. However, the average particle sizes become larger and compact between ∼0.21 and ∼3.3 μm from 600 to 1200 °C. Thus, the sintering temperature gives an impact on the phase stability, microstructure and microhardness of HA derived from high potential waste sources. Keywords: Hydroxyapatite, β-tricalcium phosphate, Biphasic, Crystallization, Sintering

Through the traditional approach of the melt-water quenching technique, it is seen that Alumino-Silicate-Fluoride (ASF) bioglass system is assembled. Through the very investigation of this paper, it is noted that preparation of ASF bioglass is composed of Clam Shells (CS), Soda Lime Silicate (SLS), CaF2, P2O5, and Al2O3 with the empirical formula [xCS⋅(45 − x)SLS⋅15CaF2⋅20P2O5⋅20Al2O3] where x= 5, 10, 15 and 20 (wt%). The waste materials used to produce ASF bioglass were CS and SLS. The physical and structural properties of bioglass are obtained through Energy X-ray (EDX), density (ρ), molar volume (Vm), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) and Field Emission Scanning Electron Microscopy (FESEM) spectroscopy. Such measured physical parameters like density and molar volume were found to vary linearly with increasing the CaO content in the bioglass composition. X-ray powder diffractrogram showed that the ASF bioglass samples with higher amount of CaO content are in amorphous phase, but a small and sharp peak crystal phase was observed and known as fluorapatite (Ca5(PO4)3F). Meanwhile, FTIR spectroscopy revealed various bonds such as SiOSi, POP, CO and OH, indicated to the formation of ASF bioglass before sintering occurred. FESEM analysis showed non-uniform particle distribution, irregular in shape and random grain size of the bioglass. Although this type of bioglass is well established for dental application, its effect on waste materials such as CS and SLS for used in dental field has not been extensively studied. Revealed various bonds, stretching and bending vibrations within the samples before sintering occurred. Keywords: Bioglass, Melt-water quenching, Soda lime silica, Clam shell, Waste materials, Fluorapatite

In this work, waste coconut husk was explored as potential raw material for silica production. Coconut husk was burned in controlled environment inside electrical furnace at 500, 600 and 700 °C. These ashes were treated by using two different chemical treatments to extract the highest percentage of silica. XRF analysis of coconut husk ash (CHA) revealed that the content of SiO2 varies between 8 and 11% and increased up to 90% after chemical treatment. Based on the XRD spectrum, silica obtained was in crystalline form after acid treatment but was in amorphous form after the alkali treatment. The CHA morphology on FESEM images observed to be rod-like structure but changed to irregular shapes and started to agglomerate together after the chemical treatments. EDX results show good agreement with XRF data as the same elements detected during both analysis. Alternative source of high purity silica can be obtained from CHA and it has high potential in optoelectronic application. Keywords: Coconut husk ash, Silica, XRD, XRF, FESEM, Agricultural waste

The alumino-silicate-fluoride (ASF) bioglass system with empirical formula [(45-x)SiO2-xCaF2-20P2O5-20Al2O3-15CaO] where x = 5, 10, 15, and 20 (wt.%) has been synthesised by using conventional melt-quenching method. In this study, soda lime silica (SLS) glass and clam shell (CS) vitreous waste were utilized as a source of silicon dioxide (SiO2) and calcium oxide (CaO), respectively. The different physical behaviors of ASF bioglass were closely related to the CaF2 content in each composition. The structural analysis shows the presence of various chemical bonds showing the formation of ASF bioglass. The ASF bioglass has many applications in dental field and efforts to improve its formulation can promise a better future in medical procedures.

This study investigated the effect of the addition of montmorillonite into a hydroxyapatite nanocomposite for biomedical application. Hydroxyapatite (HA)/montmorillonite (MMT) nanocomposite was prepared using a powder sintering technique at 800 °C for 2 h. The specific surface area and pore volume were found to decrease linearly with the addition of MMT. The addition of 10–20% MMT led to a more homogeneous pore size distribution, which resulted in an increase in flexural strength by 18.9–17.1% and an increase in compressive strength by 107.9–63.1%. However, further addition of 30–60% MMT led to a less homogeneous pore size distribution, resulting in a decrease in flexural and compressive strength. The homogeneity of the pore size distribution was found to offer significant control over the strength of the nanocomposites. The addition of MMT resulted in the presence of an anhydrite phase, and this phase is useful to enhance the bioactivity of the nanocomposite. This study shows that the addition of MMT to HA for the formation of HA/MMT nanocomposite has a beneficial effect and has the potential to be used as a biomaterial, especially for non-load bearing sites in bone substitutions. Keywords: Mechanical properties, Porosity, Hydroxyapatite, Montmorillonite

In this work, zinc silicate glass system (ZnO-SiO2) doped with various europium ion (Eu3+) concentrations derived from white rice husk ash (WRHA) were synthesized using melt and quench method. All samples determined by X-ray diffractometer (XRD) showed amorphous phase structure. The surface micrographs detected by Field emission scanning electron microscopy (FESEM) showed Eu3+ addition had reduced the sample’s porosity. Fourier transform infrared (FTIR) revealed the presence of Eu3+ ions had weakened the absorption peaks of SiO4. Meanwhile, ultra-violet visible spectroscopy (UV–vis) showed the absorption edges were shifted towards higher wavelength with Eu3+ addition. Band gap values were increased from 2.97 eV to 4.23 eV when Eu3+ dopant increased but decreased back to 3.98 eV at highest concentration. Photoluminescence spectroscopy (PL) analysis showed intense red emission at 600 nm corresponding to 5D0 → 7F2 transition were enhanced by Eu3+ doping. Hence, their luminescent properties are useful for optical device such as white light emitting diodes. Keywords: Zinc silicate glass, Europium, Rice husk, Optical properties, Solid state

In this work, manganese (II, III) oxide, (Mn3O4) doped zinc soda lime silica glasses have been synthesized using a conventional melt-quenching process and followed by control heat treatment process. The crystal phase composition and optical properties of α-Zn2SiO4:Mn3O4 based glass-ceramics are comprehensively studied. The physical properties and crystal growth of α-Zn2SiO4 phase were measured by density analysis, linear shrinkage, X-ray diffraction (XRD) and Fourier transform infrared reflection (FTIR) spectroscopy. From the measurement, the average density and linear shrinkage of α-Zn2SiO4:Mn3O4 based glass-ceramics increased with increasing heat treatment temperature. Besides, the presence of Zn–O–Si bands indicates the formation of α-Zn2SiO4 crystal phase and causing the decrement of energy band gap. The photoluminescence spectra of Mn2+ ions exhibit emission transitions of 4T1(G)–6A1(S) and show a prominent green emission colors of α-Zn2SiO4 phase at 524 nm. Keywords: α-Zn2SiO4, Glass-ceramic, Phosphor, Crystal growth, Optical properties

A binary (CuO)0.6 (CeO2)0.4 nanoparticles were prepared via thermal treatment method, using copper nitrate, cerium nitrate as precursors, PVP as capping agent and de-ionized water as a solvent. The structures, morphology, composition of the element and optical properties of these nanoparticles have been studied under different temperatures using various techniques. The XRD spectrum of the samples at 500 °C and above confirmed the existence of both monoclinic (CuO) and cubic fluorite (CeO2) structures. The findings of FESEM and TEM exhibited the average practical size and agglomeration increment with an elevation in the calcination temperature. The synthesized nanoparticles were also characterized by FTIR, which indicated the formation of binary Cu−O and Ce−O bonds. The EDX analysis was performed to indicate the chemical composition of the sample. The double energy band gaps of (CuO)0.6(CeO2)0.4 reduction with rising calcination temperature, can be referred to the enhancement of the crystallinity of the samples. PL intensity of (CuO)0.6(CeO2)0.4 nanoparticles peaks, which increased with the elevation of the calcination temperature to 800 °C was observed from the PL spectrum; this was due to the increment of the particle size that occurred. Keywords: CuO nanoparticles, CeO2 nanoparticles, Calcination temperatures

Tellurite glass systems in the form of [ZnO]x [(TeO2)0.7-(PbO)0.3]1-x with x = 0.15, 0.17, 0.20, 0.22 and 0.25 mol% were prepared using the melt quenching technique. XRD of the prepared samples have been measured for all samples. Both FTIR (280–4000 cm−1) and UV-Vis (200–800 nm) spectra have been measured. Optical band gap and refractive index were calculated for every glass sample. Density of glass, molar volume and oxygen packing density (OPD) were obtained. Values of the direct, indirect band gap ranged were found in the range 3.41–3.94 eV and 2.40–2.63 eV with increasing of ZnO concentration. Refractive index 2.58 and dielectric constant 6.66 were heigh at 17 ZnO mol% concentration. Molar polarizability, metallization criterion, polaron radius have been calculated for every glass composition. Keywords: Tellurite, Glass, Optical band gap, Refractive index

Abstract Synthesis of nanocrystalline strontium ferrite (SrFe12O19) via sol–gel is sensitive to its modification parameters. Therefore, in this study, an attempt of regulating the pH as a sol–gel modification parameter during preparation of SrFe12O19 nanoparticles sintered at a low sintering temperature of 900 °C has been presented. The relationship of varying pH (pH 0 to 8) on structural, microstructures, and magnetic behaviors of SrFe12O19 nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning microscope (FESEM), and vibrating sample magnetometer (VSM). Varying the pH of precursor exhibited a strong effect on the sintered density, crystal structure and magnetic properties of the SrFe12O19 nanoparticles. As the pH is 0, the SrFe12O19 produced relatively largest density, saturation magnetization, M s, and coercivity, H c, at a low sintering temperature of 900 °C. The grain size of SrFe12O19 is obtained in the range of 73.6 to 133.3 nm. The porosity of the sample affected the density and the magnetic properties of the SrFe12O19 ferrite. It is suggested that the low-temperature sintered SrFe12O19 at pH 0 displayed M s of 44.19 emu/g and H c of 6403.6 Oe, possessing a significant potential for applying in low-temperature co-fired ceramic permanent magnet.

This study presents the utilization of mill scale waste, which has attracted much attention due to its high content of magnetite (Fe3O4). This work focuses on the extraction of Fe3O4 from mill scale waste via magnetic separation, and ball milling was used to fabricate a microwave absorber. The extracted magnetic powder was ground-milled using two different techniques: (i) a conventional milling technique (CM) and (ii) mechanical alloying (MM) process. The Fe3O4/CM samples were prepared by a conventional milling process using steel pot ball milling, while the Fe3O4/MM samples were prepared using a high-energy ball milling (HEBM) method. The effect of milling time on the structural, phase composition, and electromagnetic properties were examined using X-ray diffraction (XRD) and a vector network analyzer (VNA). XRD confirmed the formation of magnetite after both the magnetic separation and milling processes. The results revealed that Fe3O4 exhibited excellent microwave absorption properties because of the synergistic characteristics of its dielectric and magnetic loss. The results showed that the Fe3O4/CM particle powder had a greater absorption power (reflection loss: 3O4/MM powders had higher absorption properties, including a higher RL of −20.59 dB and a broader bandwidth of 2.43 GHz at a matching thickness of only 1 mm. The higher microwave absorption performance was attributed to the better impedance matching property caused by the porous microstructure. Furthermore, the magnetite, Fe3O4 showed superior microwave absorption characteristics because of the lower value of permittivity, which resulted in better impedance matching. This study presents a low-cost approach method by reutilizing mill scale waste to fabricate a high purity crystalline Fe3O4 with the best potential for designing magnetic nano-sized based microwave absorbers.

With the trend for green technology, the study focused on utilizing a forgotten herb to produce an eco-friendly coating. Andrographis paniculata or the kalmegh leaves extract (KLE) has been investigated for its abilities in retarding the corrosion process due to its excellent anti-oxidative and antimicrobial properties. Here, KLE was employed as a novel additive in coatings and formulations were made by varying its wt%: 0, 3, 6, 9, and 12. These were applied to stainless steel 316L immersed in seawater for up to 50 days. The samples were characterized and analyzed to measure effectiveness of inhibition of corrosion and microbial growth. The best concentration was revealed to be 6 wt% KLE; it exhibited the highest performance in improving the ionic resistance of the coating and reducing the growth of bacteria.

The Er3+ doped zinc soda lime silica (ZnO-GSLS) glass system was prepared by the conventional melt-quenching technique using waste green soda lime silica (GSLS) glass, zinc oxide (ZnO) and erbium oxide (Er2O3) powder as starting materials. Er3+ doped willemite based glass-ceramics (Zn2SiO4:Er3+) were derived from this precursor glass by a controlled sintering process. The effect of sintering temperature on the density and linear shrinkage of the sample was investigated. XRD analysis revealed the presence of thermodynamically stable zinc orthosilicate (α-Zn2SiO4) phase at sintering temperatures above 700 °C. FESEM image shows the presence of densely packed grains as the sintering temperature increase. FTIR spectroscopy was used to observe the structural of SiO4 and ZnO4 groups in the formation of willemite phase evolution. The UV–Vis absorption spectra reveals four peaks centered at excitation of electron from ground state 4I15/2 to 4G11/2 (∼363 nm), 4F7/2 (∼488 nm), 2H11/2 (∼523 nm), and 4F9/2 (∼652 nm). PL spectroscopy measurements were performed at room temperature using 385 nm excitation wavelengths. Enhancement of the Er3+ luminescence was observed with the progression of sintering temperature. Keywords: Glass ceramic, Willemite, Erbium oxide, SLS glass, Sintering, Optical, Photoluminescence

In this study, an investigation was conducted to explore and synthesize silicate (SiO2) glass from waste rice husk ash (RHA). MnO2 doped zinc silicate glasses with chemical formula [(ZnO)55 + (WRHA)45]100-X[MnO2]X, (where X = 0, 1, 3 and 5 wt%) was prepared by conventional melt quenching technique. The glass samples were characterized using energy dispersive X-ray fluorescence (EDXRF), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy, and ultraviolet–visible (UV–Vis) spectroscopy. The results revealed that by increasing the concentration of MnO2, the color of glass samples changed from colorless to brown and the density of glass increased. XRD results showed that a broad halo peak which centered on the low angle (2θ = 30°) indicated the amorphous nature of the glass. FTIR results showed basic structural units of Si-O-Si in non-bridging oxygen, Si-O and Mn-O in the glass network. FESEM result showed a decreasing porosity with an increasing MnO2 content, which was attributed to the Mn ions resort to occupy interstitial sites inside the pores of glass. Besides, the absorption intensity of glass increased and the band gap value decreased with increasing the MnO2 percentage. In this synthesized glass system of MnO2 doped zinc silicate glasses using RHA as a source of silica, the MnO2 affect most of the properties of the glass system under investigation. Keywords: Rice husk, Manganese dioxide, Glass, Zinc silicate, Sintering, Optical properties

The impact of different sintering temperatures on physical, optical and structural properties of wollastonite (CaSiO3) based glass-ceramics were investigated for its potential application as a building material. Wollastonite based glass-ceramics was provided by a conventional melt-quenching method and followed by a controlled sintering process. In this work, soda lime silica glass waste was utilized as a source of silicon. The chemical composition and physical properties of glass were characterized by using Energy Dispersive X-ray Fluorescence (EDXRF) and Archimedes principle. The Archimedes measurement results show that the density increased with the increasing of sintering temperature. The generation of CaSiO3, morphology, size and crystal phase with increasing the heat-treatment temperature were examined by field emission scanning electron microscopy (FESEM), Fourier transforms infrared reflection spectroscopy (FTIR), and X-ray diffraction (XRD). The average calculated crystal size gained from XRD was found to be in the range 60 nm. The FESEM results show a uniform distribution of particles and the morphology of the wollastonite crystal is in relict shapes. The appearance of CaO, SiO2, and Ca-O-Si bands disclosed from FTIR which showed the formation of CaSiO3 crystal phase. In addition to the calculation of the energy band gap which found to be increased with increasing sintering temperature. Keywords: Soda lime silica glass, Wollastonite, Sintering, Structural properties, Optical properties

A novel environmental friendly strategy towards red phosphors in optoelectronic applications employing Pr6O11 doped SLS-ZnO with chemical composition x(Pr6O11)·100-x(SLS·ZnO) where x = 0, 1, 2, 3, 4 and 5 wt% via melt-quenching technique was successfully synthesized. The X-ray Diffraction (XRD) patterns of all these glasses show broad and diffused humps, which confirm the amorphous structure of samples. The Differential Thermal Calorimetry (DSC) indicated that the value of glass transition is higher from 625 °C to 637 °C with increasingly of Pr6O11 content. Fourier Transform Infrared Spectra (FTIR) spectra display a decreasing trend towards a smaller wavenumber with the increase of Pr content is due to the formation of non-bridging oxygen (NBO) in SLS-ZnO host matrix. The absorption spectra had revealed the most intense absorption band at ∼444 nm, which was assigned as excitation wavelength to determine the photoluminescence (PL) emission intensity of the glass. The indirect band gap values varies from ∼2.44 eV to ∼3.02 eV as a function of Pr6O11 concentration. The PL emission bands at ∼530 (blue), ∼556 (green), ∼613 (red) and ∼650 (red) nm increases from 0 wt% to 4 wt% and slightly decreases as Pr6O11 increases with a maximum at 5 wt%. Therefore, the SLS-ZnO doped with Pr6O11 as a good potential as red phosphors in an optoelectronic application in accordance with the highest red emission intensity at ∼613 nm and ∼650 nm. Keywords: X-ray Diffraction, Differential Thermal Calorimetry, Fourier Transform Infrared Spectra, Photoluminescence

An aqueous medium composed of polyvinylpyrrolidone (PVP) and cerium nitrates at calcination temperature was utilised in the production of cerium oxide (CeO2) semiconductor nanoparticles. A variety of analytical approaches was utilized to examine the structural, morphological and optical characteristics of the resulting nanoparticles. Differential thermal (DTA) and thermogravimetric (TGA) analyses, indicated that the best calcination temperatures for achieving CeO2 nanoparticle production were more than 485 °C. The results from Fourier-transform infrared (FTIR) verified the formation of a crystalline structure after calcination procedures were performed to remove residual organic compounds. Additionally, results from X-ray diffraction (XRD) analysis confirmed the cubic fluorite structure of the CeO2 produced. Samples were also analysed by energy dispersive spectroscopy (EDXA) which indicated the existence of O and Ce in the samples. Field emission scanning electron microscopy (FESEM) was used in the characterisation of nanoparticle morphological features. Transmission electron microscopy (TEM) was employed to estimate typical nanoparticle and distribution within sample. This analysis indicated that mean particle sizes were inversely correlated with PVP concentration, with nanoparticle sizes ranging between 12 ± 7 nm at 0.03 g/mL PVP and 6 ± 2 nm at 0.05 g/mL PVP. These results corroborated those obtained by XRD analysis. A UV–vis spectrophotometer was utilised in the demonstration of optical properties and to examine the band gap energy of samples. The potential UV-shielding properties of the nanoparticles were demonstrated by the observed blue shift of the estimated optical energy band, i.e. from 3.35 to 3.43 eV, whilst PL spectra results indicated that decreasing particle size was associated with diminishing photoluminescence intensity. Keywords: Cerium oxide nanoparticles, Heat treatment technique, Structural properties, Optical properties

This paper investigated the effects of Pr6O11 and Co3O4 on the electrical properties of ZnO-BaTiO3 varistor ceramics. The Pr6O11 doping has a notable influence on the characteristics of the nonlinear coefficient, varistor voltage, and leakage current where the values varied from 2.29 to 2.69, 12.36 to 68.36 V/mm and 599.33 to 548.16 µA/cm2, respectively. The nonlinear varistor coefficient of 5.50 to 7.15 and the varistor voltage of 7.38 to 8.10 V/mm was also influenced by the use of Co3O4 as a dopant. When the amount of Co3O4 was above 0.5 wt.%, the leakage current increased from 202.41 to 302.71 μA/cm2. The varistor ceramics with 1.5 wt.% Pr6O11 shows good nonlinear electrical performance at higher breakdown voltage and reduced the leakage current of the ceramic materials. Besides, the varistor sample that was doped with 0.5 wt.% Co3O4 was able to enhance the nonlinear electrical properties at low breakdown voltage with a smaller value of leakage current.

Glass ionomer cement (GIC) is a well-known restorative material applied in dentistry. The present work aims to study the effect of hydroxyapatite (HA) addition into GIC based on physical, mechanical and structural properties. The utilization of waste materials namely clam shell (CS) and soda lime silica (SLS) glass as replacements for the respective CaO and SiO2 sources in the fabrication of alumino-silicate-fluoride (ASF) glass ceramics powder. GIC was formulated based on ASF glass ceramics, polyacrylic acid (PAA) and deionized water, while 1 wt.% of HA powder was added to enhance the properties of the cement samples. The cement samples were subjected to four different ageing times before being analyzed. In this study, the addition of HA caused an increment in density and compressive strength results along with ageing time. Besides, X-ray Diffraction (XRD) revealed the formation of fluorohydroxyapatite (FHA) phase in HA-added GIC samples and it was confirmed by Fourier Transform Infrared (FTIR) analysis which detected OH‒F vibration mode. In addition, needle-like and agglomeration of spherical shapes owned by apatite crystals were observed from Field Emission Scanning Electron Microscopy (FESEM). Based on Energy Dispersive X-ray (EDX) analysis, the detection of chemical elements in the cement samples were originated from chemical compounds used in the preparation of glass ceramics powder and also the polyacid utilized in initiating the reaction of GIC.

In this paper, the structural and optical properties of ZnO-SiO2-based ceramics fabricated from oil palm empty fruit bunch (OPEFB) were investigated. The OPEFB waste was burned at 600, 700 and 800 °C to form palm ash and was then treated with sulfuric acid to extract silica from the ash. X-ray fluorescence (XRF) and X-ray diffraction (XRD) analyses confirmed the existence of SiO2 in the sample. Field emission scanning electron microscopy (FESEM) showed that the particles displayed an irregular shape and became finer after leaching. Then, the solid-state method was used to produce the ZnO-SiO2 composite and the samples were sintered at 600, 800, 1000, 1200 and 1400 °C. The XRD peaks of the Zn2SiO4 showed high intensity, which indicated high crystallinity of the composite. FESEM images proved that the grain boundaries were larger as the temperature increased. Upon obtaining the absorbance spectrum from ultraviolet–visible (UV–Vis) spectroscopy, the energy band gaps obtained were 3.192, 3.202 and 3.214 eV at room temperature, 600 and 800 °C, respectively, and decreased to 3.127, 2.854 and 2.609 eV at 1000, 1200 and 1400 °C, respectively. OPEFB shows high potential as a silica source in producing promising optical materials.

The contemporary market needs for enhanced solid–state lighting devices has led to an increased demand for the production of willemite based phosphors using low-cost techniques. In this study, Ce3+ doped willemite nanoparticles were fabricated using polymer thermal treatment method. The special effects of the calcination temperatures and the dopant concentration on the structural and optical properties of the material were thoroughly studied. The XRD analysis of the samples treated at 900 °C revealed the development and or materialization of the willemite phase. The increase in the dopant concentration causes an expansion of the lattice owing to the replacement of larger Ce3+ ions for smaller Zn2+ ions. Based on the FESEM and TEM micrographs, the nanoparticles size increases with the increase in the cerium ions. The mean particles sizes were estimated to be 23.61 nm at 1 mol% to 34.02 nm at 5 mol% of the cerium dopant. The optical band gap energy of the doped samples formed at 900 °C decreased precisely by 0.21 eV (i.e., 5.21 to 5.00 eV). The PL analysis of the doped samples exhibits a strong emission at 400 nm which is ascribed to the transition of an electron from localized Ce2f state to the valence band of O2p. The energy level of the Ce3+ ions affects the willemite crystal lattice, thus causing a decrease in the intensity of the green emission at 530 nm and the blue emission at 485 nm. The wide optical band gap energy of the willemite produced is expected to pave the way for exciting innovations in solid–state lighting applications.

Background: The aim of this study was to investigate whether boron nitride (BN) and BN–chromium (BN–Cr) coatings applied with the sputtering method would change the characteristics of hardness and discoloration of the ceramic veneer surface. Materials and Methods: In this experimental study, thirty disc-shaped cores (10 mm in diameter and 0.8 mm in thickness) were prepared. Three different ceramic systems, IPS Empress (E) (Ivoclar Vivadent, Schaan, Liechntenstein), IPS e.max Press (EP) (Ivoclar Vivadent, Schaan, Liechntenstein), and Turkom Cera (T) (Turcom-Ceramic SDN-BHD, Kuala Lumpur, Malaysia), were tested, each with n = 10. The specimens were divided into two subgroups (n = 5) according to the coating on the veneering ceramic: BN or BN–Cr. The Vickers hardness and color differences (ΔE) values were measured before and after coating. Surface analysis was performed with X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopic. The Wilcoxon signed-rank test was performed to compare hardness values. The Kruskal–Wallis test was performed to compare ΔE values among all groups. The post hoc tests was used after Kruskal–Wallis, with level of statistical significance set at P ≤ 0.05. Results: BN–Cr coating statistically significantly increased the hardness of all types of ceramics (P < 0.05). BN coating did not change the hardness statistically significantly (P > 0.05). The mean ΔE values indicated clinically noticeable (over the limit of 3.7) color change in all groups except for the EP-BN and T-BN groups. Conclusion: Although BN–Cr coating in this thickness had a negative effect on color, it increased the hardness of the ceramics and could be useful in the palatal region.

This research paper proposes the usage of a simple thermal treatment method to synthesis the pure and Eu3+ doped ZnO/Zn2SiO4 based composites which undergo calcination process at different temperatures. The effect of calcination temperatures on the structural, morphological, and optical properties of ZnO/Zn2SiO4 based composites have been studied. The XRD analysis shows the existence of two major phases which are ZnO and Zn2SiO4 crystals and supported by the finding in the FT-IR. The FESEM micrograph further confirms the existence of both ZnO and Zn2SiO4 crystal phases, with progress in the calcination temperature around 700–800 °C which affects the existence of the necking-like shape particle. Absorption humps discovered through UV-Vis spectroscopy revealed that at the higher calcination temperature effects for higher absorption intensity while absorption bands can be seen at below 400 nm with dropping of absorption bands at 370–375 nm. Two types of band gap can be seen from the energy band gap analysis which occurs from ZnO crystal and Zn2SiO4 crystal progress. It is also discovered that for Eu3+ doped ZnO/Zn2SiO4 composites, the Zn2SiO4 crystal (5.11–4.71 eV) has a higher band gap compared to the ZnO crystal (3.271–4.07 eV). While, for the photoluminescence study, excited at 400 nm, the emission spectra of Eu3+ doped ZnO/Zn2SiO4 revealed higher emission intensity compared to pure ZnO/Zn2SiO4 with higher calcination temperature exhibit higher emission intensity at 615 nm with 700 °C being the optimum temperature. The emission spectra also show that the calcination temperature contributed to enhancing the emission intensity.

In this study, the authors attempted to propose the very first study on fabrication and characterization of zinc-boro-silicate (ZBS) glass-ceramics derived from the ternary zinc-boro-silicate (ZnO)0.65(B2O3)0.15(RHA)0.2 glass system through a conventional melt-quenching method by incorporating rice husk ash (RHA) as the silica (SiO2) source, followed by a sintering process. Optimization of sintering condition has densified the sintered samples while embedded beta willemite (β-Zn2SiO4) and alpha willemite (α-Zn2SiO4) were proven in X-ray diffraction (XRD) analysis. Field emission scanning electron microscopy (FESEM) has shown the distribution of willemite crystals in rhombohedral shape crystals and successfully form closely-packed grains due to intense crystallization. The photoluminescence (PL) spectra of all sintered ZBS glasses presented various emission peaks at 425, 463, 487, 531, and 643 nm corresponded to violet, blue, green, and red emission, respectively. The correlation between the densification, phase transformation, microstructure, and photoluminescence of Zn2SiO4 glass-ceramic phosphor is discussed in detail.

Grog is an additive material that plays important roles in ceramic making. It improves the fabrication process of green bodies as well as the physical properties of fired bodies. Few low-cost materials and wastes have found their application as grog in recent years, thus encouraging the replacement of commercial grogs with cost-saving materials. Coal fly ash, a combustion waste produced by coal-fired power plant, has the potential to be converted into grog owing to its small particle sizes and high content of silica and alumina. In this study, grog was derived from coal fly ash and mixed with kaolin clay to produce ceramics. Effects of the grog addition on the resultant ceramics were investigated. It was found that, to a certain extent, the grog addition reduced the firing shrinkage and increased the total porosity of the ceramics. The dimensional stability of the ceramics at a firing temperature of 1200 °C was also not noticeably affected by the grog. However, the grog addition in general had negative effects on the biaxial flexural strength and refractoriness of the ceramics.

The phenomenon of relaxation in dielectric materials is described as one of the powerful tools to determine the behavior and properties of ion transport. The kinetics of ionic species and dipole in solid-state electrolyte are dependent on frequency, temperature, and dielectric relaxation. Li1+xTi2−xAlx(PO4)3 conducting solid state electrolyte with x = 0.3 was synthesized via conventional solid state technique using the raw materials Li2CO3, TiO2, Al2O3, and NH4H2PO4 as starting materials. TGA/DTG and X-ray diffraction measurements were carried out to study the thermal behavior and phases of the composition. It was observed from the TGA/DTA curves that there is no mass loss above 500 °C. The XRD peaks were observed to start appearing at 500 °C which corresponds to small peaks in TGA. It was also pointed out that at increasing sintering temperatures from 700 °C to 1000 °C the number of phases drastically decreased which is attributed to the complete chemical reaction. Temperature and frequency dependence of dielectric relaxation and electric modulus of the compounds were investigated at temperatures 30–230 °C and at frequencies of 40 kHz–1 MHz. The findings showed that the dielectric relaxation peaks shift to higher temperature as frequency increases and the change in ac conductivity with frequency is in agreement with Jonscher’s power law. Keywords: Sintering behavior, Dielectric permittivity, Universal power law, Electric modulus

A low cost method was employed to synthesize ZnO-SLS:xEu3+ phosphors using recyclable bottle glass as silica source. The structural and optical properties of ZnO-SLS:xEu3+ (x = 0, 1, 2, 3, 4 and 5 wt.%) glasses were determined using X-ray diffraction (XRD), Fourier transform infrared reflectance (FTIR), UV-visible (Uv-Vis) and photoluminescence (PL) spectroscopy. Structural investigation using XRD measurement had broadened the halo peak with the doping of dopants. FTIR spectra showed the glass system consists of –OH and SiO4 bands. Meanwhile, the optical measurement using UV-Vis absorption has been induced a blue shift of the electronic absorption edge. The emission peak intensity of ZnO-SLS:xEu3+ phosphors was enhanced with the progression of doping concentration and thus, revealed their potential as red emitting phosphors under 400 nm excitation. Keywords: Eu3+ doped ZnO-SLS glasses, Solid state method, Optical band gap, Photoluminescence

This study was conducted to fabricate and characterize of glass–ceramic foam derived from soda-lime silica (SLS) glass waste and eggshell (ES) waste as a foaming agent by using empirical formula [ES] × [SLS]100−x where x = 1 wt%, 3 wt%, 6 wt%, 9 wt%. The samples undergo a heat-treatment process at temperature 800 °C with a heating rate of 10 °C/min. The properties of the samples were measured by average density measurement and linear expansion. The structural properties were studied by XRD, FESEM and FTIR concerning the different composition of the foaming agent while the mechanical properties were determined by compressive strength using UTM. The lowest density and compressive strength were achieved by 0.326 g/cm3 and 0.04 MPa, respectively with the highest linear expansion at 77.33% by the addition of 3 wt% of ES. Moreover, the cristobalite phase (SiO2) were identified after the heat treatment process. The production of foam glass–ceramics using SLS glass and ES can be applied to prepare different type of porosity that gives benefit to the environment and energy usage.

A new transparent zinc silicate glass-ceramic was derived from the 55ZnO–5B2O3–40SLS glass system via a controlled heat-treatment method. The precursor glass sample was placed through the heat-treatment process at different temperatures to study the progress in phase transformation, optical performance and emission intensity of the zinc silicate glass-ceramics. For this project, material characterization was measured through several tests using densimeter and linear shrinkage measurement, X-ray diffraction (XRD), Fourier transform infrared reflection (FTIR), ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopy. The density and linear shrinkage measurements show that the density of the particular glass-ceramic samples increases with the progression of heating temperature. The XRD analysis displays the result in which the zinc silicate crystal starts to grow after the sample was treated at 700 °C. In addition, the FTIR spectra indicated that the crystallization of the zinc silicate phase occurred with the appearance of SiO4, ZnO4 and Si-O-Zn bands. UV–visible exhibited the small changes when the value for the optical band gap decreased from 3.867 to 3.423 eV, influenced by the temperature applied to the sample. Furthermore, the PL spectroscopy showed an enhancement of broad green emission at 534 nm upon the increased heat-treatment temperature. Thus, it can be concluded there is the progression of crystal growth as the heat-treatment temperature increased; three emission peaks appeared at 529, 570 and 682 nm for the green, yellow and red emissions, respectively.

For the very first time, a study on the crystallization growth of zinc silicate glass and glass-ceramics was done, in which white rice husk ash (WRHA) was used as the silicon source. In this study, zinc silicate glass was fabricated by using melt–quenching methods based on the composition (ZnO)0.55(WRHA)0.45, where zinc oxide (ZnO) and white rice husk ash were used as the raw materials. The control crystallization technique was used in which the sample was sintered at 700–950 °C; then, the physical, structural, and optical properties of the glass and glass-ceramics were investigated by using a densitometer, linear shrinkage, X-ray diffraction (XRD), Fourier transform infrared radiation (FTIR), field-emission scanning electron microscopy (FESEM), and photoluminescence spectroscopy (PL). The density and linear shrinkage increased as the crystallinity increased and the XRD results showed the progression of the crystal formation, in which the sample was still in an amorphous state at 27 °C and 700 °C; the crystalline phase started at 750 °C. Based on the FTIR spectra, all samples showed sharpened absorption bands as the sintering temperature was increased, and the FESEM image showed the progression of crystal growth, indicating the formation of zinc silicate glass-ceramics. Lastly, the PL spectra emitted three emission peaks, at 529, 570, and 682 nm for the green, yellow, and red emission, respectively.

Cenospheres are small, hard-shelled hollow spheres with high silica and alumina content. These micron-sized aluminosilicate hollow spheres constitute only a small percentage of the coal fly ash (CFA) obtained from the coal combustion processes. In this study, cenospheres were separated from CFA obtained from a coal-fired power plant located in Kapar, Malaysia. The cenospheres were heated at 1000, 1200 and 1400 °C to study the changes in morphologies, compositions, phase formation and thermal expansion. The sintering temperatures were selected based on the differential scanning calorimetry (DSC) curve results. X-ray diffractometry (XRD), field emission electron microscopy (FESEM), energy dispersive spectroscopy (EDS) as well as thermogravimetry and differential scanning calorimetry analysis (TG–DSC) were used for the characterization study. The study found that the cenospheres have excellent weight stability but are thermally unstable as a result of crystallization and melting. The phase ordering process and devitrification of the amorphous aluminosilicate glass phase at high temperatures lead to the increment and enrichment of the mullite phase in cenospheres. It is suggested that a preheating treatment at 1100 °C could be used to enhance the mechanical properties and thermally stabilize the cenospheres, which make it more suitable for use as a pore-forming agent in ceramics.

The green synthesis of silica has been extensively explored over the last few decades, as silica compounds found in commercial products can cause negative effects on human health. This calls for alternative ways to produce silica that are safer, cheaper and more environmentally friendly. Some of the agricultural wastes proven to contain silica include rice husk, sugarcane bagasse, coconut shells and coconut husk. This paper describes the synthesis of silica from coconut husk waste, and its physical and optical properties for potential utilization in optical applications. Coconut husk was subjected to fire at 500−700 °C so as to form coconut husk ash (CHA), and was then treated with sulfuric acid to extract silica from the ash. Most of the weight degradation subsequently occurred at temperatures from 221 to 360 °C. X-ray fluorescence (XRF) analysis proved that 91.76% of the silica was obtained, while major peaks on the X-ray diffraction (XRD) spectrum were observed after the acid treatment. Chemical bonds such as Si-O-Si, CH2, -OH and Si-OH were found in the spectrum of the Fourier transform infrared spectroscopy (FTIR). Furthermore, the particles displayed rod-like shapes and irregular sizes, but the particle with sizes ranging from 200−750 nm decreased after the acid treatment. The relationship between the absorption coefficient and photon energy was obtained by finding the optical energy gap, which was found to be 4.3 eV. These data points provide critical information when used in optical applications. The overall studies show that synthesized silica has great potential for use in optical field applications.

Mixture of aluminum dross (AD) and coal fly ash (CFA) was used to produce high-temperature porous mullite for washcoat application. CFA is the combustion by-product of pulverized coal in a coal-fired power plant, while AD is a waste product produced in secondary aluminum refining. In this study, 80 wt% of AD and 20 wt% of CFA was used to prepare a mullite precursor (MP) via acid leaching and dry-milling. The precursor was coated on a substrate and subsequently fired at 1500 °C. The results showed that the precursor transformed to a hierarchical porous microstructure assembled by large interlocked acicular mullite crystals. The pore structures consisted of large interconnected open pores and small pores. The specific surface area of the mullite washcoat was 4.85 m2g−1 after heating at 1500 °C for 4 h. The specific surface area was compatible with the specific surface area of other high-temperature washcoats.

This work focused on the influence of carbon nanotubes (CNT) to the microstructural properties of Zn _2 SiO _4 /CNT (ZSO/CNT) composite. CNT was synthesized via alcohol catalytic chemical vapor deposition (ACCVD) using cobalt oxide as catalyst and ethanol as carbon source. Zinc silicate (ZSO) glass was prepared from quenching the melted commercial waste glass bottle with zinc oxide powder. ZSO/CNT-x composites with various CNT concentration (0, 1, 2 and 3 wt%) was prepared through introducing CNT into ZSO glass via dry processing technique followed by sintering process in Argon gas (Ar) environment and atmospheric (atm) environment, respectively. FESEM, XRD and EDS were employed to determine the surface morphology, phase composition and elemental distribution of sintered sample. Crystallite trigonal willemite (Zn _2 SiO _4 ) phase was observed from argon sintered sample and the crystallite size of willemite phase in ZSO/CNT-3/Ar showed the most reduced lattice strain of 22.85% compared to ZSO/CNT-0/Ar. In contrast, semi-crystalline phase exhibited in atmospheric sintered sample resulted in high lattice strain. It is concluded that dry powder processing and inert gas thermal treatment can be an effective technique in fabricating strain-reduced ceramics/CNT composite without alternating the domain phase. Least internal strain in crystal lattice have potential on enhancing the luminescence properties of phosphor material and lattice thermal conductivity of thermoelectric material.

This study offers a new method to synthesize facilely willemite (Zn2SiO4) based phosphor at the temperature of 800 °C. The ZnO-SiO2 nanocomposite was calcined at different temperatures between 500 and 1000 °C. The structural, morphological and optical properties of the nanocomposite obtained at various calcination temperatures were studied using different techniques. The FT-IR, XRD and the UV-vis result confirmed the formation of willemite phase. The precursor was confirmed to be amorphous by XRD at room temperature, but upon calcination temperature at 500 °C, it was transformed into a crystalline structure. The crystallinity and the particle size of the nanocomposite increase as the calcination temperature were increased as revealed by XRD and TEM measurement. The sample exhibits a spherical morphology from 500 to 800 °C and dumbbell-like morphology above 800 °C as shown by the FESEM images. The absorption spectrum suffers intense in lower temperature and tends to shift to lower wavelength in the UV region as the calcination temperature increases. The band gap values were found to be increasing from 3.228-5.550 eV obtained between 500 to 1000 °C, and all the results confirm the formation of willemite phase at 800 °C.

In this work, the corrosion behavior of welded lap joints of AA6061-T6 aluminum alloy produced by friction stir welding process has been investigated. Corrosion properties of welded lap joints were studied by cyclic polarization and electrochemical impedance spectroscopy tests. All tests were performed in an aerated 0.6 mol L−1 NaCl aqueous solution with pH = 6.5 at a temperature of 30 °C to characterize corrosion morphology and realize corrosion features of weld regions as opposed to the parent alloy. The microstructure of weld nugget (WN), heated affected zone (HAZ), and parent alloy were analyzed using scanning electron microscopy and energy dispersive spectroscopy. The experimental results indicated that the welding process has a major effect on the corrosion resistance, which possibly associated to the break-down and dissolution of intermetallic particles. It is supposed that an increasing in intermetallic distributed throughout the matrix of weld regions increases the galvanic corrosion couples. Furthermore, by decreasing the grain size in the weld regions, the susceptibility to corrosion is enhanced. The pitting corrosion and intergranular attack are the dominant corrosion types in the weld regions and the parent alloy.

The corrosion behavior at different positions (top and bottom) of the weld nugget zone along the thickness plates in AA6061-T6 aluminum alloys welded by friction stir lap welding, under the conditions of 1000 rpm-60 mm/min and 900 rpm-40 mm/min in a 3.5 wt% NaCl solution, was investigated by Tafel polarization at ambient temperature. The morphology of the nugget zone corroded surfaces was analyzed by scanning electron microscopy together with energy dispersive spectroscopy (SEM-EDS) as well as atomic force microscopy (AFM). It was found that the top half of the nugget zone has a better corrosion resistance than that of the bottom half for both welding conditions. A localized pit dissolution with combined intergranular corrosion are the dominant corrosion types across different positions of the nugget zone for various welding conditions and in the parent alloy.

A porous ceramic is made from composite materials which consist of alumina and commercial rice husk ash. This type of ceramics is obtained by mixing the commercial rice husk ash as a source of silica (SiO2) and a pore forming agent with alumina (Al2O3) powder. To obtain this type of ceramic, a solid-state technique is used with sintering at high temperature. This study also investigated the effects of the rice husk ash ratios on the mechanical properties, porosity, and microstructure. The results showed that, by increasing the content of the rice husk ash from 10 to 50 wt%, there is an increase in the porosity from 42.92% to 49.04%, while the mechanical properties decreased initially followed by an increase at 30 wt% and 50 wt%; the hardness at 20 wt% of the ash content was recorded at 101.90 HV1. When the ash content was increased to 30 wt% and 50 wt%, the hardness was raised to 150.92 HV1 and 158.93 HV1, respectively. The findings also revealed that the tensile and compressive strengths experienced a decrease at 10 wt% of the ash content and after that increase at 30 wt% and 50 wt% of rice husk ash. XRD analysis found multiple phases of ceramic formation after sintering for the different rice husk ash content.