Energy Dispersive X-ray Diffraction Techniques Research Articles

Extreme conditions research using the large-volume press at the P61B endstation, PETRA III.

Penetrating, high-energy synchrotron X-rays are in strong demand, particularly for high-pressure research in physics, chemistry and geosciences, and for materials engineering research under less extreme conditions. A new high-energy wiggler beamline P61 has been constructed to meet this need at PETRA III in Hamburg, Germany. The first part of the paper offers an overview of the beamline front-end components and beam characteristics. The second part describes the performance of the instrumentation and the latest developments at the P61B endstation. Particular attention is given to the unprecedented high-energy photon flux delivered by the ten wigglers of the PETRA III storage ring and the challenges faced in harnessing this amount of flux and heat load in the beam. Furthermore, the distinctiveness of the world's first six-ram Hall-type large-volume press, Aster-15, at a synchrotron facility is described for research with synchrotron X-rays. Additionally, detection schemes, experimental strategies and preliminary data acquired using energy-dispersive X-ray diffraction and radiography techniques are presented.

Malaysia’s Rare Earth Element Story: Characterizing the "Amang"

Amang is known as a waste product after extraction of tin oxide (cassiterite, SnO2) from its ore. Not long ago, in Malaysia, these tin ore tailings were left in abundance after long years of mining activities. Little had it been realized then, of the importance and future economics of the heavy minerals present in these tailing ‘deposits’ may offer. It is known that the heavy minerals from amang contained rare earth elements that are beneficial in various applications in different types of industries, such as monazite ([Ce, La, Nd, Gd, Th] PO4), zircon (ZrSiO4), ilmenite (FeOTiO2), xenotime (YPO4) and struverite (NbTaTiO2). This paper looks briefly in Malaysia’s REE story and the contents of amang, that makes the story. Amang samples from Kinta Valley were chosen to be characterized, being reminiscent of the country’s REE exploits. Mineral characterization were achieved via various equipment and techniques; this includes utilizing Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray spectroscopy (EDX), X-ray Fluorescence (XRF) and X-ray diffraction (XRD) techniques, to determine (amongst others) surface morphology and morphological element/mineral identification, chemical element identification and mineral phases present, respectively. Mineralogical studies were also done by scrutinizing polished sections, interpreted under the reflected-light microscope and SEM/EDX, providing more insight into the mineral distribution in the amang and the possibility of liberation. All analyses were done at different size fractions for good comparison with possible indication of ample physical processing, before any proposed chemical processing can take place. Results showed that the chemical and phase constituents in amang were conclusively identified, with the complex distribution of mineral phases reaching 80% liberation at sizes below 125 μm.

Using Sawdust Derived Biochar as a Novel 3D Particle Electrode for Micropollutants Degradation

This work examined the use of a 3D combined electrochemical process based on particle electrodes from sawdust-derived biochar pyrolized at T = 550–850 °C to remove persistent pollutants. The as-prepared biochar was characterized by scanning electron microscopy with an X-ray energy dispersive spectrometer (SEM/EDS), nitrogen adsorption (BET method) and X-ray diffraction (XRD) techniques. The use of sawdust biochar pyrolized at 650 °C led to a significant increase in efficiency against the sum of conventional 2D electrochemical systems and adsorption, and the synergy index estimated equal to 74.5% at optimum conditions. Sulfamethoxazole (SMX) removal was favored by increasing particle electrode loading. Despite that, the reaction was slightly favored in near-neutral conditions; the system retained most of its activity in the pH range 3–10. The proposed 3D system could degrade different micropollutants, namely SMX, Bisphenol A (BPA), Propylparaben (PP), and Piroxicam (PR). Of particular interest was that no significant reduction in degradation was observed in the case of complex or real water matrices. In addition, the system retained its efficiency regarding SMX removal after five sequential experiments in the 3D combined electrochemical process. However, further investigation is needed to estimate the contribution of the different mechanisms of micropollutant removal in the proposed system.

Synthesis and Physical Properties of Iridium-Based Sulfide Ca1−xIr4S6(S2) [x = 0.23–0.33

We present the synthesis and characterization of the iridium-based sulfide Ca1−xIr4S6(S2). Quality and phase analysis were conducted by means of energy-dispersive X-ray spectroscopy (EDXS) and powder X-ray diffraction (XRD) techniques. Structure analysis reveals a monoclinic symmetry with the space group C 1 2/m 1 (No. 12), with the lattice constants a = 15.030 (3) Å, b = 3.5747 (5) Å and c = 10.4572 (18) Å. Both X-ray diffraction and EDXS suggest an off-stoichiometry of calcium, leading to the empirical composition Ca1−xIr4.0S6(S2) [x = 0.23–0.33]. Transport measurements show metallic behavior of the compound in the whole range of measured temperatures. Magnetic measurements down to 1.8 K show no long range order, and Curie–Weiss analysis yields θCW = −31.4 K, suggesting that the compound undergoes a magnetic state with short range magnetic correlations. We supplement our study with calculations of the band structure in the framework of the density functional theory.

Performance of graphene-zinc oxide nanocomposite coated-glassy carbon electrode in the sensitive determination of para-nitrophenol

Graphene: zinc oxide nanocomposite (GN:ZnO NC) platform was tried for the sensitive determination of para-nitrophenol (p-NP) through the electrochemical method. ZnO nanoparticles (NPs) were synthesized by the modified wet-chemical method where in potassium hydroxide and zinc nitrate were used as precursors and starch as a stabilizing agent. A green and facile approach was applied to synthesize GN:ZnO NC in which glucose was employed as a reductant to reduce graphene-oxide to graphene in the presence of ZnO NPs. The synthesized NC was characterized using scanning and high-resolution transmission electron microscopy, energy dispersive x-ray analysis, X-ray diffraction and Raman spectroscopic techniques to examine the crystal phase, crystallinity, morphology, chemical composition and phase structure. GN:ZnO NC layer deposited over the glassy carbon electrode (GCE) was initially probed for its electrochemical performance using the standard 1 mM K3[Fe(CN)6] model complex. GN:ZnO NC modified GCE was monitored based on p-NP concentration. An enhanced current response was observed in 0.1 M phosphate buffer of pH 6.8 for the determination of p-NP in a linear working range of 0.09 × 10–6 to 21.80 × 10–6 M with a lower detection limit of 8.8 × 10–9 M employing square wave adsorptive stripping voltammetric technique at a deposition-potential and deposition-time of − 1.0 V and 300 s, respectively. This electrochemical sensor displayed very high specificity for p-NP with no observed interference from some other possible interfering substances such as 2, 4-di-NP, ortho-NP, and meta-NP. The developed strategy was useful for sensitive detection of p-NP quantity in canals/rivers and ground H2O samples with good recoveries.

Protective TixSiy coatings for enhanced oxidation resistance of the ɣ-TiAl alloy at 900 °C

Due to well-balanced mechanical properties and density ratio, ɣ-TiAl alloys have been extensively investigated for potential aircraft jet engine applications. However, their use is restricted by limited oxidation resistance at temperatures above 750 °C. The present study focuses on the development of titanium silicide protective coatings using different Si reservoirs (3.0 μm, 6.0 μm and 9.5 μm of initial Si thickness) deposited by magnetron sputtering, followed by different periods (2 h to 24 h) of vacuum thermal annealing at 950 °C. The growth of titanium silicides and evolution of the composition and microstructure following oxidation was investigated using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD) techniques. The initial Si thickness and annealing time have an influence on the formation of different zones of composition, assigned as the TixSiy layer, interdiffusion zone and TiAl2 zone, which are correlated with their oxidation behavior at 900 °C in laboratory air after 100 h. The ɣ-TiAl substrates with Si-based coatings presented a protective inner layer of TixSiy. The coatings with initial 3 μm of Si show formation of mixed Si and Ti oxides as well as minor Al content, and traces of Cr at the oxide scale. The oxidation process is described by the parabolic oxidation coefficient, kp, with values of kp = 3.5–8.9 × 10−12 g2·cm−4·s−1 for the coated surfaces, one order of magnitude lower than for the bare substrate. In comparison, the coating systems possessing a higher initial Si thickness (6.0 μm and 9.5 μm) mainly exhibit the mixed formation of dense Si and Al oxide scales with significant Cr enrichment.

Anomalous codeposition of NiCo alloy coatings and their corrosion behaviour

Here, we report the electrodeposition NiCo alloy coatings from a new bath using the glycine, as additive. A bright and uniform coatings NiCo alloy have been developed at different current densities and their corrosion performances have been evaluated. The surface morphology, composition and phase structure of alloy coatings have been analyzed using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray diffraction (XRD) techniques, respectively. The compositional information of NiCo alloy coatings revealed that the proposed bath follows anomalous type of codeposition over range of current density studied (1.0–4.0 A dm−2), by demonstrating more Wt. % of Co in the deposits, than in the bath. A constant increase in the Wt. % of Ni with current density was found, supported by XRD analyses; and it may be attributed to the depletion of more readily depositable Co+2 ions at cathode film by following the principle of codeposition of NiCo alloy. The corrosion study revealed that NiCo alloy deposited at 4.0 A dm−2, represented as (NiCo) 4.0 A dm-2 coating is the most corrosion resistant compared to all other coatings. The highest corrosion stability of (NiCo) 4.0 A dm-2 alloy attributed to its highest Ni content (38.6 wt%) and increased surface smoothness, supported by EDS and SEM study.

Entomopathogenic fungus, Metarhizium anisopliae, anchored onto MCM-41 silica nanomaterial: A novel and effective insecticide against potato tuber moth in stored potatoes

Summary Phthorimaea operculella (PTM) is an economically significant invasive potato insect pest in tropical and sub-tropical regions. Due to many problems concerning chemical insecticides, biocontrol agents such as entomopathogenic fungi have attracted researchers’ interest regarding their application as a part of integrated potato tuber moth management strategies in several countries. Hence, in the present study, we examined the lethal effects of entomopathogenic fungus, Metarhizium anisopliae (used as pure culture (PEF) or formulated with MCM-41 silica nanomaterial (MCM-41@fungus)) on eggs and neonate larvae of PTM. The MCM-41was completely characterized by Fourier transform infrared (FT-IR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDS), X-ray diffraction (XRD), and Thermogravimetric analysis (TGA) techniques. The morphology of MCM-41@fungus was evaluated by scanning electron microscope (SEM). The morphology of the mesoporous structure was exhibited to be homogeneous, regular, and spherical. LC50 values of PEF and MCM-41@fungus were estimated to be 1.7×107 and 2×105 conidia/ml for eggs and 1.8×106 and 1.5×104 conidia/ml for neonate larvae, respectively. Hence, bioassays demonstrated that MCM-41@fungus was more toxic than the pure culture at egg and neonate larval stages of the pest. The results exhibited that pure M. anisopliae and its nano-formulation could play key roles as biopesticides in management programmes of P. operculella.

Microstructure evolution, mechanical properties, and fractography of AA7068/ Si3N4 nanocomposite fabricated thorough ultrasonic-assisted stir casting advanced with bottom pouring technique

Ceramic particulate embedded aluminum metal matrix nanocomposites (AMNCs) possess superior mechanical and surface properties and lightweight features. AMNCs are a suitable replacement of traditional material, i.e., steel, to make automotive parts. The current work deals with developing Si3N4 strengthened high strength AA7068 nanocomposites via novel ultrasonic-assisted stir casting method advanced with bottom pouring setup in the proportion of 0.5, 1.0, 1.5, and 2 wt.%. Planetary ball milling was performed on a mixture of AA7068 powder and Si3N4 (in the proportion of 3:1) before incorporation in aluminum alloy melt to avoid rejection of fine particles. Finite element scanning electron microscope (FESEM), Energy dispersive spectroscopy (EDS), X-Ray diffraction (XRD), and Elemental mapping techniques were used in the microstructural investigation. Significant grain refinement was observed with increasing reinforcing content, whereas agglomeration was found at higher weight %. Hardness, Tensile strength, ductility, porosity content, compressive strength, and impact energy were also examined of pure alloy and each composite. Improvement of 72.71%, 50.07%, and 27.41 % was noticed in hardness value, tensile strength, and compressive strength, respectively, at 1.5 weight % compared to base alloy because of various strengthening mechanisms. These properties are decreased at 2 wt.% due to severe agglomeration. In contrast, nanocomposite’s ductility and impact strength continuously decrease compared to monolithic AA7068. Fracture analysis shows the ductile and mixed failure mode in alloy and nanocomposites.

High Temperature Corrosion Behavior of High Velocity Oxy Fuel Sprayed NiCrMoFeCoAl-30%SiO2 and NiCrMoFeCoAl-30%Cr2O3 Composite Coatings on ASTM SA213-T22 Steel in a Coal-fired Boiler Environment

High-velocity oxy fuel (HVOF) sprayed coatings can improve the corrosion resistance of bare ASTM SA213-T22 boiler steel. In this report, we have investigated the NiCrMoFeCoAl-30%SiO2 and NiCrMoFeCoAl-30%Cr2O3 composite coatings were deposited on bare ASTM SA213-T22 boiler steel for corrosion protection. High-temperature corrosion studies were conducted in a molten salt (Na2SO4-60%V2O5) environment at 700ºC under thermo-cyclic conditions. The as-sprayed composite coatings are characterized for microstructure and mechanical properties. The thermo-gravimetric method was utilized to understand the kinetics of corrosion. Characterization of the corrosion products was examined by using scanning electron microscope (SEM)/ Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The obtained results suggest both the composite coatings are favorable to corrosion resistance over the bare ASTM SA213-T22 boiler steel. The NiCrMoFeCoAl-30%Cr2O3 composite coating was concluded to present a superior corrosion resistance in the high-temperature corrosion environment because of the uniform distribution of the composite coating matrix and the development of protective protection Cr2O3 in the scale. The molten salt heat-treated chromium oxide containing coating shows good corrosion stability than the silica composite. This could be attributed to the high temperature assisted formation metal chromates, chromites and oxide layers.

The corrosion behaviour of stainless steels and Ni-based alloys in nitrate salts under thermal cycling conditions in concentrated solar power plants

Molten nitrate salts are widely used as heat transfer fluids and heat storage media for concentrated solar power (CSP) plants due to their favourable thermo-physical properties. The corrosion of alloys in nitrate salts used in CSP plants poses a critical challenge to the safety, cost and efficiency of their operations under high temperature. In this study, the corrosion behaviour of stainless steels; 321 and 347, and Ni-based alloy; IN 625 and In 825, in Solar (nitrate) salts has been experimentally investigated under isothermal (at 600 °C) and thermal cycling (between 600 °C and 250 °C) conditions, and under argon atmosphere. Corrosion assessment of test materials was achieved using gravimetric measurements in a simulated metal – molten salt environment in a furnace for 7 days. The micro-morphology and cross-sectional analysis of the corroding interface was carried out using a combination of scanning electron microscopy, energy dispersive X-ray spectroscopy and X-Ray diffraction techniques. Compared with isothermal condition, thermal cycling between the 250 °C (for 12 hrs) and 600 °C (for 12 hrs) reduces the corrosion rate of test materials, the severity of corrosion attack and the thickness of corrosion product layers. The result also shows that corrosion product breakdown due to spallation was also reduced by lower time at maximum temperature and cooling effect during thermal cycling, especially in stainless steels when compared with isothermal conditions at 600 °C. The spallation process became prominent with the formation of a Na-Fe oxide layer at the corrosion interface. Ni-based alloys show better corrosion resistance than stainless steels under both isothermal and thermal cycling conditions due to the superior passivation behaviour from combined Cr and Ni enrichment. Cr2O3 and NiO were formed as an inner layer in a multi-layered corrosion products on the metal surface from reaction with oxygen. Oxygen was made available from the decomposition of nitrate ions at 600 °C.

Oxide Formation in a Melt Spun Alloy in the Zr-Ni-Cu System

The microstructure of a melt-spun Zr28Ni44Cu28 (at. %) alloy was characterized in order to determine the structures and compositions of the crystalline phases that compete with glass formation during rapid solidification. Two crystalline phases were identified, namely, a face centered cubic (FCC) zirconium oxide phase and a primitive cubic version of the big-cube oxide phase, using a combination of scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscopy techniques. Our results indicate that the Zr-O atomic pair interaction is preferential compared to the other atomic pair possibilities, supporting the formation of Zr-based oxides over the equilibrium phases in the ternary Zr-Ni-Cu system. Further, the results provide insight into the mechanisms of oxygen-induced crystallization in Zr-based BMGs and the corresponding decrease in glass forming ability (GFA) with increasing oxygen concentrations.

Corrosion behavior of electrophoretically deposited boron nitride nanosheets on copper

The prime purpose of this research study is to determine the possibility of corrosion protection offered by boron nitride nanosheets (BNNSs) coated on pure Copper (Cu) strip through electrophoretic deposition (EPD). BNNSs suspension was developed by sonicating hexagonal boron nitride in isopropyl alcohol for 35 h prior to centrifugal partitioning of the supernatant solution, which contained BNNSs having thickness of ca. 11 nm as shown by atomic force microscopy. BNNSs deposition on copper substrate was processed in an EPD electrochemical cell arrangement keeping Cu metal as cathode and platinum as anode. The consequent BNNSs coating on the substrate was critically confirmed through series of microscopies adopting scanning electron, atomic force, and Fourier transform infrared. Energy dispersive x-ray analysis and x-ray diffraction techniques inferred the characterization positively. Tafel analysis and electrochemical impedance spectroscopy both were implied in order to evaluate  the corrosion behavior of coatings developed on substrate copper. The former confirmed an approximate sixfold enhancement in anti-corrosion capacity of copper protected by BN nanosheets than its bare form. The later, EIS analysis indicated a high impedance and charge transfer resistance ability of BNNSs coatings.

Novel and efficient method for loading aptamer-conjugated liposomes with arsenic trioxide for targeting cancer cells

Although the therapeutic effect of liposomal arsenic trioxide arsenic trioxide (ATO) in the treatment of solid tumours has been confirmed, its dose-limiting loading is a challenging issue. To solve the problems in the preparation of liposomal ATO, different loading strategies were evaluated and compared. In addition, liposomes decorated with anti-nucleolin aptamers were developed as a novel formulation for targeted delivery with high loading efficiency and sustained releasing property in order to treat solid tumours. The liposomes were prepared by a thin-film method exploiting the passive loading strategy of Co(II) hydrogen arsenite (CHA). The structural characteristics of the liposomes were also investigated by Fourier transform infra-red spectroscopy (FT-IR), dynamic light scattering (DLS), zeta potentiometry, field emission scanning electron microscopy (FESEM), and Energy Dispersive X-ray Diffraction (EDX) techniques. To evaluate the potential cytotoxicity of this liposomal drug vehicle in vitro, MTT assay was performed on HT-29 cancer cell line. The results showed that the synthesised liposomes loaded with CHA exhibited high entrapment efficiency (77%). MTT assays showed a significant difference between the percentage of viable cells when HT −29 cells were treated with free ATO and liposomal formulation which can be corresponded to the sustained release of the drug from the liposomes. The results of this study may lead to a promising strategy for the effective treatment of solid tumours.

Nanomechanical property evaluation of tungsten thin film via frequency-domain photoacoustic microscopy

This study investigates the reduction in nanomechanical properties of a tungsten (W) thin film measured using a laser ultrasonic technique. A 96 nm thick W film was prepared via direct-current magnetron sputtering and inspected using scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray reflectivity techniques. Moreover, frequency-domain photoacoustic microscopy was employed to evaluate the Young's modulus (EW) of W. The velocity dispersion of a surface acoustic wave excited by an intensity-modulated laser was measured and curve-fitted using a computational finite element model to estimate EW. In addition, a high-frequency microcantilever resonance test was performed to verify the results. The results show that EW of the film is 45.3% lower than that of the macroscopic property because of the predominant β-W phase. The Young's moduli obtained from the two different techniques agree well with each other, with a relative error of 13.3%. The hardness-to-EW ratio obtained using a nanoindenter was calculated to be 0.025±0.004.

Investigation on pulsed electrolytically polished AlSi10Mg alloy processed via selective laser melting technique

Currently, the surface integrity-related issues of additively manufactured parts are limiting the potential high-end applications. The present work investigates the effectiveness of the pulsed-electropolishing technique to improve the surface integrity of aluminium alloys fabricated using the selective laser melting (SLM) technique. Due to its low density, high corrosion resistance, the aluminium alloys considerably enhance the performance of lightweight critical parts for different industrial applications. In this study, selective laser melted AlSi10Mg samples were subjected to microstructural examinations using optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction technique. The microhardness and tensile properties were determined using a microhardness tester and a universal testing machine, respectively. The pulsed-electropolishing process was employed for the surface finishing of the SLM-processed AlSi10Mg samples. The effect of current density on the electropolishing of selective laser melted AlSi10Mg alloy were also investigated. The microstructures of printed samples revealed a density of greater than 99.9% and weld beads along the build direction (longitudinal) and laser scan paths perpendicular to the build direction (transverse). The microhardness, yield and tensile strength properties were similar in both as-printed conditions. The pulsed electropolishing results showed a beneficial effect of higher current density values, resulting in decreased surface roughness of the SLM-processed AlSi10Mg samples. Compared to as-printed conditions, a significant decrease in surface roughness of about ∼73.35% under optimized electropolishing conditions was noted. The material ratio curve shows that the surface topography becomes more uniform with increased current density and has lesser surface undulations for as-printed samples. The 2D line profilogram and 3D surface topography of electropolished SLM-processed samples reveal the surface finish quality characteristics. The material ratio curve aids as an effective method to assess and qualify the surface topography of electropolished samples.

Fabrication and characterization of Al6063/SiC composites using electromagnetic stir casting process

In this work, metal matrix composites were fabricated using the electromagnetic stir casting process by adding 5 and 10 wt% silicon carbide in Al6063 alloy. Hardness, ultimate tensile strength, and yield strength of the developed Al6063/SiC/5p metal matrix composites have been improved by 17%, 18%, and 37%, respectively, in comparison with Al6063 alloy. Further, an improvement of 25%, 37%, and 71% in hardness, ultimate tensile strength, and yield strength, respectively, have been noted for Al6063/SiC/10p metal matrix composite in comparison with the Al6063 alloy. Results revealed that the hardness and strength of metal matrix composites were increased with silicon carbide addition in Al6063 alloy. The presence of different elements in metal matrix composites was identified by energy-dispersive X-ray spectroscopy and X-ray diffraction techniques. Energy-dispersive X-ray spectroscopy was used for elemental mapping observation of the metal matrix composites. Uniform distribution of reinforcement particles in the matrix with improved mechanical properties of metal matrix composites proved the adequacy of the electromagnetic stir casting process. The presence of facets and dimples in fractographs indicated the mixed mode of fracture. The average percentage porosity presented in Al6063/silicon carbide/5p and Al6063/SiC/10p metal matrix composites was found to be 4.68% and 5.22%, respectively.

Elevated temperature erosive wear behavior of superalloy coatings deposited using cold spray technology

The boiler tube components in thermal power plants and steam generating systems suffer from erosion and corrosion problems and are even today posturing a grave threat to industries, resulting in forced outages. Unrelenting efforts to decrease the components’ maintenance costs have been made by protecting with coatings. Among the various coating methodologies are thermal spray, chemical vapour deposition (CVD), physical vapour deposition (PVD), etc., in vogue. However, recently, the additive manufacturing-based cold spray technique is gaining interest among material scientists, incorporating high-velocity impacts associated with the low-temperature regime. Nickel-based superalloy Inconel 625 has been chosen and cold sprayed on The American Society of Mechanical Engineers (ASME) T11 and T22 boiler steels. The coated surface is characterized by scanning electron microscopy and energy dispersive X-ray analysis (EDAX), X-ray diffraction, micro-hardness, and elemental X-ray mapping techniques. The solid particle erosion studies have been carried out both at room and an elevated temperature of 700 °C as per American Society for Testing and Materials (ASTM) standard for 30°C and 90 °C impact angles. An optical profilometer has been used to evaluate the erosion volume loss. The results showed that the coated samples exhibit superior erosion resistance than the uncoated samples at both room and elevated temperatures. The erosion data obtained have been substantiated using scanning electron microscopy by analyzing the damage features and correlating with the erosion data.

Influence of Portland cement on performance of fine rice husk ash geopolymer concrete: Strength and permeability properties

Recently, industrial by-products such as rice husk ash has been identified as potential alternative binders to Ordinary Portland Cement (OPC) in concrete. Yet, it compromises the strength and concrete performance to some extent. One viable way is through partial replacement of such alternative binders with OPC, in order to achieve satisfactory concrete properties for practical applications. Thus far, no thorough study has been conducted to understand the properties of fine rice husk ash (FRHA) based geopolymer concrete (GPC) with different OPC content. This study focused on the influence of OPC as a substitution of FRHA on the strength and permeability of FRHA based GPC. The effects of OPC substitution on various properties, namely compressive strength, flexural strength, splitting tensile strength, modulus of elasticity, water absorption and chloride penetration resistance, were experimentally studied. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques were also conducted to analyse the microstructural features. Experimentally, the optimum content of OPC in GPC was identified as 15%, since the highest compressive strength of 53.69 MPa was achieved at 90 days. Deterioration of the mechanical properties was observed with further increase in OPC replacement. Flexural strength, splitting tensile strength and modulus of elasticity also followed similar trends. In addition, water absorption (4.42%) and charge (1037 Coulombs) achieved by specimens with 15% OPC replacement were the lowest for all ages, suggesting improved durability performance. Microstructural studies also showed the enhanced and denser structure of GPC due to OPC substitution as a result of the formation of higher amount of calcium-silicate-hydrate (CSH) gel alongside calcium-aluminate-silicate-hydrate (CASH) andsodium-aluminate-silicate-hydrate (NASH) gels. These polymerisation gels strengthened the network by filling the voidsand enhancing the properties of GPC. Thus, it was concluded that the optimal combination of FRHA (85%) and OPC (15%) prominently enhanced the GPC properties by improving its overall performance.

Compositional, Structural and Morphological Analyses of Bulk GeS Alloy and its Thin Films

Bulk Germanium monosulphide (GeS) alloy was synthesized using the usual melt-quenching technique. Its grains were used as the source material to deposit thin films by vacuum thermal evaporation. Thin-films samples were doped with 1, 2, and 3 at.% indium by thermal co-evaporation and annealed in a vacuum at temperatures 373, 473 and 550 K for an hour. Compositional, structural, and morphological properties of the bulk GeS alloy and its thin films were investigated by Energy Dispersive X-Ray Spectroscopy (EDS), X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) techniques. The analyses verified the stoichiometry (GeS) of the starting material in the prepared thin films. They also revealed that the thin films under study are amorphous, homogeneous, without any cracks deposited uniformly on the glass substrate with thickness 650 to 700 nm.