Measurement of low magnetic field has played an important role in many electronics applications such as navigation, military, non-destructive test, traffic detection as well as medical diagnosis and treatment. The presence of magnetic field, particularly its strength and direction, can be measured using magnetometer. There are many types of magnetometers being investigated through the years and one of the prominent types is fluxgate magnetometer. The main components of fluxgate magnetometer consisting of driving coils, sensing coils and magnetic core are developed by MEMS silicon processing technology. In this paper, an investigation on physical characteristics of the three-dimensional coil structure for a micro-scaled fluxgate magnetometer is presented. The physical characteristics such as width of the coil, distance between successive coils, and gap between the top and bottom coils which would influence the magnetic energy in magnetometer is discussed. In this work, finite-element method simulations to investigate the physical characteristics of the sensing coils were carried out, where the parameter of interest is the coils’ inductance as well as the magnetic flux density. Based on the simulation results, the varying of physical characteristics of the coils had its effects particularly in coil inductance, magnetic flux density, and magnetic energy. It could also be seen that the simulated results agreed with the theoretical aspects of magnetism in a coil. From the investigations, suitable coil dimensions were proposed.
Low-temperature growth, as well as the transfer free growth on substrates, is the major concern of graphene research for its practical applications. Here we propose a simple method to achieve the transfer free graphene growth on SiO2 covered Si (SiO2/Si) substrate at 250 °C based on a solid-liquid-solid reaction. The key to this approach is the catalyst metal, which is not popular for graphene growth by chemical vapor deposition. A catalyst metal film of 500 nm thick was deposited onto an amorphous C (50 nm thick) coated SiO2/Si substrate. The sample was then annealed at 250 °C under vacuum condition. Raman spectra measured after the removal of the catalyst by chemical etching showed intense G and 2D peaks together with a small D and intense SiO2 related peaks, confirming the transfer free growth of multilayer graphene on SiO2/Si. The domain size of the graphene confirmed by optical microscope and atomic force microscope was about 5 μm in an average. Thus, this approach will open up a new route for transfer free graphene growth at low temperatures.
The influence of SiO2/TiO2 nanocomposites (STNCs) content on non-radiative energy transfer (Förster-type) from poly (9,9'-dioctylfluorene-2,7-diyl) (PFO) to poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) using steady-state and time-resolved photoluminescence spectroscopies was investigated at room temperature. The improved energy transfer from PFO to MEH-PPV upon an increment of the STNCs was achieved by examining absorbance, emission (PL) and photoluminescence excitation (PLE) spectra. The shorter values of the quantum yield (φDA) and lifetime (τDA) of the PFO in the hybrid thin films compared with the pure PFO, indicating efficient energy transfer from PFO to MEH-PPV with the increment of STNCs in the hybrid. The energy transfer parameters can be tuned by increment of the STNCs in the hybrid of PFO/MEH-PPV. The Stern-Volmer value (kSV), quenching rate value (kq), Förster radius (R0), distance between the molecules of PFO and MEH-PPV (RDA), energy transfer lifetime (τET), energy transfer rate (kET), total decay rate of the donor (TDR), critical concentration (Ao), and conjugation length (Aπ) were calculated. The gradually increasing donor lifetime and decreasing acceptor lifetime, upon increasing the STNCs content, prove the increase in conjugation length and meanwhile enhance in the energy transfer.
The production of cement releases an enormous amount of CO2 into the environment. Besides, industrial wastes like silica fume and fly ash need effective utilization to reduce their impacts on the environment. This research aims to explore the influence of silica fume (SF) and fly ash (FA) individually and combine them as binary cementitious material (BCM) on the hardened properties and embodied carbon of roller compacted concrete (RCC). A total of ten mixes were prepared with 1:2:4 mix ratio at the different water-cement ratios to keep the zero slump of roller compacted concrete. However, the replacement proportions for SF were 5%-15%, and FA were 5%-15% by the weight of cement individually and combine in roller compacted concrete for determining the hardened properties and embodied carbon. In this regard, several numbers of concrete specimens (cubes and cylinders) were cast and cured for 7 and 28 days correspondingly. It was observed that the compressive strength of RCC is boosted by 33.6 MPa and 30.6 MPa while using 10% of cement replaced with SF and FA individually at 28 days, respectively. Similarly, the splitting tensile strength of RCC is enhanced by 3.5 MPa at 10% cement replaced with SF and FA on 28 days, respectively. The compressive and splitting tensile strength of RCC is increased by 34.2 MPa and 3.8 MPa at SF7.5FA7.5 as BCM after 28 days consistently. In addition, the water absorption of RCC decreased while using SF and FA as cementitious material individually and together at 28 days. Besides, the embodied carbon of RCC decreased with increasing the replacement level of SF and FA by the mass of cement individually and combined.
In this research investigation, three microalgal species were screened (Pleurosigma sp., Amphora sp., and Amphiprora sp.) for lipid content before choosing the potential microalgae for biodiesel production. It was found that the lipid content of Amphiprora sp. was 41.48 ± 0.18%, which was higher than the Pleurosigma sp. (27.3 ± 0.8%) and Amphora sp. (22.49 ± 0.21%). The diatom microalga, Amphiprora sp. was isolated and exposed to a controlled environment. Two different media were prepared, and the main research was on the SiO2-NP medium as the cell wall of diatom was made up of silica. Essential growth parameters were studied such as dry cell weight and chlorophyll a content. The results revealed that Amphiprora sp. cultured in the modified medium showed a higher biomass yield and growth rate in all the analyses. In Soxhlet extraction method, biodiesel yield of Amphiprora sp. in modified medium under 24 μmol m-2 s-1 of light intensity was 81.47 ± 1.59% when using 2% of catalyst amount with 1.5:1 volume ratio of methanol/oil in 3 h reaction time at 65 °C. Results reveled that Amphiprora sp. diatom has a higher yield of oil 52.94 ± 0.42% and can be efficiently optimized with further studies with modified nanomaterial culture medium. The present research revealed the series of experiments on microalgal lipid transesterification and in future investigation different types of nanomaterials should be used in culture medium to identify the lipid production in microalgal cells.
Research for alternative binders has become a necessity due to cement's embodied carbon, climate change, and depletion of natural resources. These binders could potentially reduce our reliance on cement as the sole binder for concrete while simultaneously enhancing the functional characteristics of concrete. Theoretically, the use of finer particles in the cement matrix densifies the pore structure of concrete and results in improved properties. To validate this hypothesis, current research was designed to investigate how the value-added benefits of nano-silica (NS) and metakaolin (MK) in fly ash (FA)-blended cement affect the mechanical and durability characteristics of concrete when used as ternary and quaternary blends. Additionally, the cost-benefit analysis and environmental impact assessment were conducted. It was observed that the synergy of MK and NS used in FA-blended cement had a greater impact on enhancing the functional characteristics of concrete, while 10% MK as ordinary Portland cement (OPC) replacement and 1% NS as an additive in FA-blended OPC concrete was the optimum combination which achieved 94-MPa compressive strength at the age of 91 days and showed more than 25% increment in the flexural and splitting tensile strengths compared to the control mix (MS00). The ultrasonic pulse velocity and dynamic modulus of elasticity were significantly improved, while a significant reduction in chloride migration of 50% was observed. In terms of environmental impact, MS100 (30% FA and 10% MK) exhibited the least embodied CO2 emissions of 319.89 kgCO2/m3, while the highest eco-strength efficiency of 0.268 MPa/kgCO2·m-3 with respect to 28-day compressive strength was exhibited by MS101. In terms of cost-benefit, MS00 was determined the cheapest, while the addition of MK and NS increased the cost. The lowest cost of producing 1 MPa was exhibited by MS01 with a merely 0.04-$/MPa/m3 reduction compared to MS00.
This study aimed at determining the effects of propagation medium and cutting types on the early growth performance of fig (Ficus carica L.) root and shoot. The experiment was conducted at the Glasshouse and Nursery Complex (GNC), International Islamic University Malaysia (IIUM). The split-plot design was employed with the main plot (propagation medium) and sub-plot (types of cutting). The propagation medium were sand:topsoil (1:3) (M1), topsoil:peat:sawdust (1:1:1) (M2) and peat:perlite (1:1) (M3). Two types of cutting were semi-hardwood (C1) and hardwood (C2). As a result, there were a significant effect of propagation medium on measured parameters. This study revealed that the most effective propagation medium and cutting types for the propagation of fig were a combination of peat and perlite at 1:1 ratio (M3) and hardwood cutting (C2), respectively as evidenced by significantly higher root and shoot growth quality as compared to other treatments.
Copper (Cu) ion in wastewater is considered as one of the crucial hazardous elements to be quantified. This research is established to predict copper ions adsorption (Ad) by Attapulgite clay from aqueous solutions using computer-aided models. Three artificial intelligent (AI) models are developed for this purpose including Grid optimization-based random forest (Grid-RF), artificial neural network (ANN) and support vector machine (SVM). Principal component analysis (PCA) is used to select model inputs from different variables including the initial concentration of Cu (IC), the dosage of Attapulgite clay (Dose), contact time (CT), pH, and addition of NaNO3 (SN). The ANN model is found to predict Ad with minimum root mean square error (RMSE = 0.9283) and maximum coefficient of determination (R2 = 0.9974) when all the variables (i.e., IC, Dose, CT, pH, SN) were considered as input. The prediction accuracy of Grid-RF model is found similar to ANN model when a few numbers of predictors are used. According to prediction accuracy, the models can be arranged as ANN-M5> Grid-RF-M5> Grid-RF-M4> ANN-M4> SVM-M4> SVM-M5. Overall, the applied statistical analysis of the results indicates that ANN and Grid-RF models can be employed as a computer-aided model for monitoring and simulating the adsorption from aqueous solutions by Attapulgite clay.
The junctionless nanowire transistor is a promising alternative for a new generation of nanotransistors. In this letter the atomic force microscopy nanolithography with two wet etching processes was implemented to fabricate simple structures as double gate and single gate junctionless silicon nanowire transistor on low doped p-type silicon-on-insulator wafer. The etching process was developed and optimized in the present work compared to our previous works. The output, transfer characteristics and drain conductance of both structures were compared. The trend for both devices found to be the same but differences in subthreshold swing, 'on/off' ratio, and threshold voltage were observed. The devices are 'on' state when performing as the pinch off devices. The positive gate voltage shows pinch off effect, while the negative gate voltage was unable to make a significant effect on drain current. The charge transmission in devices is also investigated in simple model according to a junctionless transistor principal.
The idea of applying a simple Fabry-Perot fiber laser (FPFL) set-up in a free-running condition as an acoustic sensing medium is proposed. Conventional optical microphone requires a stringently aligned diaphragm to mediate the acoustic impedance mismatch between air and silica fiber. Motivated by the difficulty of optical sensing of airborne acoustic waves, a new sensing method is proposed to sense acoustic waves without the assistance of a diaphragm as transducer. By studying the output power fluctuation of the FPFL, the operating bandwidth and sensitivity of the proposed sensing method are determined. The tunability of the resonant frequency from 5 kHz to 85 kHz allows sensing of acoustic waves in the range of 100 Hz to 100 kHz. Tuning of the resonant frequency can be performed by changing the optical pumping power from as low as 10 mW to 68.5 mW or higher.
In this paper, the bifurcation behavior of light in the PANDA ring resonator is investigated using the signal flow graph (SFG) method, where the optical transfer function for the through and drop ports of the PANDA Vernier system are derived. The optical nonlinear phenomena, such as bistability, Ikeda instability, and dynamics of light in the silicon-on-insulator (SOI) PANDA ring resonator with four couplers are studied. The transmission curves for bistability and instability as a function of the resonant mode numbers and coupling coefficients for the coupler are derived by the SFG method and simulated. The proposed system has an advantage as no optical pumping component is required. Simulated results show that closed-loop bistable switching can be generated and achieved by varying mode resonant numbers in the SOI-PANDA Vernier resonator, where a smooth and closed-loop bistable switching with low relative output/input power can be obtained and realized. The minimum through-port switching time of 1.1 ps for resonant mode numbers of 5;4;4 and minimum drop port switching time of 1.96 ps for resonant mode numbers of 9;7;7 of the PANDA Vernier resonator are achieved, which makes the PANDA Vernier resonator an operative component for optical applications, such as optical signal processing and a fast switching key in photonics integrated circuits.
Lightweight cementitious composite (LCC) produced by incorporating lightweight silica aerogel was explored in this study. Silica aerogel was incorporated as 60% replacement of fine aggregate (sand/crushed glass) in producing the LCC. The effect of aerogel on the drying shrinkage and alkali-silica expansion of LCC was evaluated and compared with those of lightweight expanded perlite aggregate. At the density of 1600 ± 100 kg/m3, the aerogel/ expanded perlite LCC had attained compressive strength of about 17/24 MPa and 22/26 MPa in mixtures with sand and crushed glass as a fine aggregate, respectively. The inclusion of aerogel and expanded perlite increased the drying shrinkage. The drying shrinkage of aerogel LCC was up to about 3 times of the control mixtures. Although the presence of aerogel and expanded perlite could reduce the alkali-silica expansion when partially replacing crushed glass, the aerogel-glass LCC still recorded expansion exceeding the maximum limit of 0.10% at 14 days. However, when 15% cement was replaced with fly ash and granulated blast furnace slag, the alkali-silica expansion was reduced to 0.03% and 0.10%, respectively. Microstructural observations also revealed that the aerogel with fly ash can help in reducing the alkali-silica expansion in mixes containing the reactive crushed glass aggregate.
Electronic waste has become a global concern, as it has been steadily increasing over the years. The lack of regulation and appropriate processing facilities has rendered these wastes an environmental hazard. However, they represent excellent alternative sources of precious metals, which are highly in demand in various industries. Adsorption has been a popular method for metal removal/recovery because of several advantages, such as ease of use and low cost. In this regard, it is crucial to develop an inexpensive and functionalized adsorbent to selectively adsorb precious metals. Thus, silica, which is derived from rice husk and is abundantly present in Indonesia, was functionalized using an ionic liquid (SiRH_Im) and used for Au(III) adsorption from a simulated mobile phone leach liquor. SiRH_Im exhibited a high adsorption capacity (232.5 mg g-1). The Au(III) adsorption kinetic suitably fitted with the pseudo-second-order kinetic model. The Au(III) adsorption followed a chemisorption route that suited the monolayer model. Thomas' and Yoon-Nelson's models were well suited for the continuous Au(III) behavior. Selective recovery of Au(III) from SiRH_Im was achieved via sequential desorption. SiRH_Im also showed excellent reusability, as indicated by a negligible decrease in adsorptive performance over three cycles. The functionalization of silica derived from rice husk using an ionic liquid led to the successful creation of a solid adsorbent with a high adsorption capacity toward precious metals present in a simulated leach solution. Our results highlight the benefit of the functionalization of biomass through the immobilization of an ionic liquid toward the enhancement of its adsorption capability.
In this work, a simple sol-gel approach was used for the preparation of cyanopropyl (CNPr) functionalized silica nanoparticles (SiO2-CNPr) that tetraethoxysilane (TEOS) and cyanopropyltriethoxysilane (CNPrTEOS) used as precursors. This as-prepared SiO2-CNPr nanoparticle sorbent was first characterized using FESEM, EDX, FTIR, TGA, and BET techniques. Then, the SiO2-CNPr nanoparticle was applied as a new SPE sorbent for determining trace levels of OPPs in environmental water samples. To enhance the simultaneous extraction of non-polar or/and polar OPPs and to obtain the most efficient sorbent, several sol-gel synthesis parameters were studied. In addition, the effect of several effective parameters on SPE performance was investigated toward simultaneous extraction of non-polar or/and polar OPPs. Moreover, the figures of merit such as precision, linearity, LOQ, LOD, and recovery were evaluated for the sorbent. Finally, the designed SiO2-CNPr SPE was used to determine OPPs in real water samples, and its extraction performance was compared to commercial cartridges based on cyanopropyl.
A method for improving the thermoluminescence (TL) yield of silica-based optical fibres is demonstrated. Using silica obtained from a single manufacturer, three forms of pure (undoped) fibre (capillary-, flat-, and photonic crystal fibre (PCF)) and two forms of Ge-doped fibre (capillary- and flat-fibre) were fabricated. The pure fibre samples were exposed to 6 and 21MeV electrons, the doped fibres to 6MV photons. The consistent observation of large TL yield enhancement is strongly suggestive of surface-strain defects generation. For 6MeV irradiations of flat-fibre and PCF, respective TL yields per unit mass of about 12.0 and 17.5 times that of the undoped capillary-fibre have been observed. Similarly, by making a Ge-doped capillary-fibre into flat-fibre, the TL response is found to increase by some 6.0 times. Thus, in addition to TL from the presence of a dopant, the increase in fused surface areas of flat-fibres and PCF is seen to be a further important source of TL. The glow-curves of the undoped fibres have been analysed by computational deconvolution. Trap centre energies have been estimated and compared for the various fibre samples. Two trap centre types observed in capillary-fibre are also observed in flat-fibre and PCF. An additional trap centre in flat-fibre and one further trap centre in PCF are observed when compared to capillary fibre. These elevated-energy trap centres are linked with strain-generated defects in the collapsed regions of the flat fibre and PCF.
This proof-of-concept study proposes a novel sensing mechanism for selective and label-free detection of 2,4,6-trinitrotoluene (TNT). It is realized by surface chemistry functionalization of silica nanoparticles (NPs) with 3-aminopropyl-triethoxysilane (APTES). The primary amine anchored to the surface of the silica nanoparticles (SiO2-NH2) acts as a capturing probe for TNT target binding to form Meisenheimer amine-TNT complexes. A colorimetric change of the self-assembled (SAM) NP samples from the initial green of a SiO2-NH2 nanoparticle film towards red was observed after successful attachment of TNT, which was confirmed as a result of the increased separation between the nanoparticles. The shift in the peak wavelength of the reflected light normal to the film surface and the associated change of the peak width were measured, and a merit function taking into account their combined effect was proposed for the detection of TNT concentrations from 10-12 to 10-4 molar. The selectivity of our sensing approach is confirmed by using TNT-bound nanoparticles incubated in AptamerX, with 2,4-dinitrotoluene (DNT) and toluene used as control and baseline, respectively. Our results show the repeatable systematic color change with the TNT concentration and the possibility to develop a robust, easy-to-use, and low-cost TNT detection method for performing a sensitive, reliable, and semi-quantitative detection in a wide detection range.
Using irradiated doped-silica preforms from which fibres for thermoluminescence dosimetry applications can be fabricated we have carried out a range of luminescence studies, the TL yield of the fibre systems offering many advantages over conventional passive dosimetry types. In this paper we investigate such media, showing emission spectra for irradiated preforms and the TL response of glass beads following irradiation to an 241Am-Be neutron source located in a tank of water, the glass fibres and beads offering the advantage of being able to be placed directly into liquid. The outcomes from these and other lines of research are intended to inform development of doped silica radiation dosimeters of versatile utility, extending from environmental evaluations through to clinical and industrial applications.
The oxidative and thermal stability of low diglycerides palm oil produced via silica treatment (sPO) and enzymatic treatment (ePO) compared with standard quality palm oil (SQ) and premium quality palm oil (PQ) was investigated. Both of the oils displayed better oxidative stability compared with SQ as well as significantly higher (P < 0.05) thermal resistance and oxidative strength than SQ and PQ due to lower amounts of partial glycerides. Although the initial induction periods (IPs) of sPO and ePO were significantly lower compared with SQ and PQ, both the oils showed slower drops in their IP values. The darkening effect after frying was significantly (P < 0.05) slower in sPO compared with SQ, PQ, and ePO. Besides, there is no difference p > 0.05 in the rate of FFA formation between sPO and PQ. The anisidine value and peroxide values were lowest in sPO, followed by ePO, PQ, and SQ.
Over the past decade and more, considerable interest has been shown in the thermoluminescence (TL) properties of silica-based single-mode optical fibres, in particular investigating potential ionising radiation dosimetry applications. Herein, study has been made of TL glow curve, dose response, reproducibility and fading of 6mol% Ge-doped silica, fabricated in-house and produced in the form of cylindrical fibres. Three different pairings of doped-core and silica cladding diameters were produced: (40, 241)µm, (80, 483)µm and (100, 604)µm. The TL results were compared against that of TLD-100, one of the most sensitive commercially available LiF-based TL media. For all three pairings of diameters, closely similar TL glow curve were obtained, formed of a single peaked structure with a maximum TL yield located between the temperatures 250 and 310°C. The TL yield of the fibres were linear over the range of doses investigated, from 1Gy up to 10Gy, their dose response exceeding that of TLD-100, the samples also being found to be reusable, without evidence of degradation.
The study reports the preparation of a composite consisting of magnetite coated with nanosilica extracted from oil palm leaves (OPL) ash as nanosupports for immobilization of Candida rugosa lipase (CRL) and its application for the synthesis of butyl butyrate. Results of immobilization parameters showed that ∼ 80% of CRL (84.5 mg) initially offered was immobilized onto the surface of the nanosupports to yield a maximum protein loading and specific activity of 67.5 ± 0.72 mg/g and 320.8 ± 0.42 U/g of support, respectively. Surface topography, morphology as well as information on surface composition obtained by Raman spectroscopy, atomic force microscopy, field emission scanning electron microscopy and transmission electron microscopy showed that CRL was successfully immobilized onto the nanosupports, affirming its biocompatibility. Under optimal conditions (3.5 mg/mL protein loading, at 45 ℃, 3 h and molar ratio 2:1 (1-butanol:n-butyric acid) the CRL/Gl-A-SiO2-MNPs gave a maximum yield of 94 ± 0.24% butyl butyrate as compared to 84 ± 0.32% in the lyophilized CRL. CRL/Gl-A-SiO2-MNPs showed an extended operational stability, retaining 50% of its initial activity after 17 consecutive esterification cycles. The results indicated that OPL derived nanosilica coated on magnetite can potentially be employed as carrier for lipase immobilization in replacement of the non-renewable conventionalsilica sources.