17 research outputs found
An integrated experimental and theoretical approach to probe Cr (VI) uptake using decorated halloysite nanotubes for efficient water treatment
No full textHalloysite nanotubes (HNTs) were surface functionalized using four distinct chemical moieties (amidoxime, hydrazone, ethylenediamine (EDA), and diethylenetriamine (DETA)), producing modified HNTs (H1–H4) capable of binding with Cr(VI) ions. Advanced techniques like FTIR, XRD, SEM, and EDX provided evidence of the successful functionalization of these HNTs. Notably, the functionalization occurred on the surface of HNTs, rather than within the interlayer or lumen. These decorated HNTs were effective in capturing Cr(VI) ions at optimized sorption parameters, with adsorption rates ranging between 58–94%, as confirmed by atomic absorption spectroscopy (AAS). The mechanism of adsorption was further scrutinized through the Freundlich and Langmuir isotherms. Langmuir isotherms revealed the nearest fit to the data suggesting the monolayer adsorption of Cr(VI) ions onto the nanotubes, indicating a favorable adsorption process. It was hypothesized that Cr(VI) ions are primarily attracted to the amine groups on the modified nanotubes. Quantum chemical calculations further revealed that HNTs functionalized with hydrazone structures (H2) demonstrated a higher affinity (interaction energy −26.33 kcal mol−1) for the Cr(VI) ions. This can be explained by the formation of stronger hydrogen bonds with the NH moieties of the hydrazone moiety, than those established by the OH of oxime (H1) and longer amine chains (H3 and H4), respectively. Overall, the findings suggest that these decorated HNTs could serve as an effective and cost-efficient solution for treating water pollution.This article is published as Shah, Syed Nadeem Ahmad, Sonia Zulfiqar, Fernando Ruipérez, Muhammad Rafique, Mudassir Iqbal, Michael J. Forrester, Muhammad Ilyas Sarwar, and Eric W. Cochran. "An integrated experimental and theoretical approach to probe Cr (VI) uptake using decorated halloysite nanotubes for efficient water treatment." RSC advances 14, no. 5 (2024): 2947-2960. doi: https://doi.org/10.1039/D3RA07675J. © 2024 The Author(s). This Open Access Article is licensed under a Creative Commons Attribution-Non Commercial 3.0
First-principles study of electronic and optical properties of boron and nitrogen doped graphene
No full textProbabilistic modeling and simulation of microstructural evolution in zr based bulk metallic glass matrix composites during solidification
No full text© The Minerals, Metals & Materials Society 2018. Bulk metallic glass and their composites are unique new materials which have superior mechanical and structural properties as compared to existing conventional materials. However, their mechanical behavior is dubious, unpredictable and requires extensive experimentation to draw conclusive results. In present study, which is continuation of previous work of author, a non-linear one-dimensional iterative deterministic model is combined with two-dimensional probabilistic cellular automaton method to describe nucleation and growth of primary ductile phase from melt in glassy matrix during solidification. Preliminary methodology ad philosophy of model making is described with an aim to explain the grounds on which this approach is adopted. MATLAB® is chosen as programing platform. Results indicate that the effect of incorporating all heat transfer, mass transfer and diffusion coefficients with appropriate interpolation play a vital role in refining the model and bringing it closer to actual experimental observations. Two types of hypo and hyper eutectic systems were studied with different inoculants
Electrochemical Investigations of BaCe0.7-xSmxZr0.2Y0.1O3-δ Sintered at a Low Sintering Temperature as a Perovskite Electrolyte for IT-SOFCs
No full textPerovskite materials have gained a lot of interest in solid oxide fuel cell (SOFC) applications owing to their exceptional properties; however, ideal perovskites exhibit proton conduction due to availability of low oxygen vacancies, which limit their application as SOFC electrolytes. In the current project, Sm was doped at the B-site of a BaCe0.7-xSmxZr0.2Y0.1O3-δ perovskite electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs). BaCe0.7-xSmxZr0.2Y0.1O3-δ electrolytes were synthesized through a cost-effective coprecipitation method and were sintered at a low sintering temperature. The effects of samarium (Sm) doping on the electrochemical performance of BaCe0.7-xSmxZr0.2Y0.1O3-δ were investigated. X-ray diffraction (XRD) analysis confirmed that the BaCe0.7-xSmxZr0.2Y0.1O3-δ electrolyte material retained the perovskite structure. The secondary phase of Sm2O3 was observed for BaCe0.4Sm0.3Zr0.2Y0.1O3-δ. Scanning electron microscopic (SEM) imaging displayed the dense microstructure for all the compositions, while prominent crystal growth was observed for composition x = 0.3. The formation of the perovskite structure and the presence of the hydroxyl groups of metal oxides for all the compositions were confirmed by Fourier transform infrared spectroscopy (FTIR). An increased symmetrical disturbance was also observed for the increased doping ratio of the Sm. Thermogravimetric analysis (TGA) of all the compositions showed no major weight loss in the SOFC operating temperature range. It was also noted that the conductivity of BaCe0.7-xSmxZr0.2Y0.1O3-δ gradually decreased with the increased contents of the Sm metal. The maximum power density of 390 mW cm−2, and an open-circuit voltage (OCV) of 1.0 V at 600 °C, were obtained, showing that BaCe0.7-xSmxZr0.2Y0.1O3-δ, synthesized by a cost-effective method and sintered at a low temperature, can be used as a proton-conducting electrolyte for IT-SOFCs.Rivers, Ports, Waterways and Dredging Engineerin
Effect of surface roughness at elevated temperature and pressure on the oxidation behaviour of co-based alloy
No full textCo-based alloys are promising to offer high-temperature corrosion resistance under extreme environmental conditions. Here, we report a novel approach that exploits the characteristics of the oxidation scale by making the specimens ground at three different levels to compare the effects of surface roughness in the presence and absence of external pressure. At a constant pressure of 2.5 MPa, the influence of surface roughness on the oxidation behaviour at an elevated temperature of 1050°C for 430 h has been investigated via scanning electron microscopy coupled with an energy-dispersive X-ray spectrometer and X-ray diffraction. The results have revealed that for rough surfaces the thickness of the oxide scale with Ra = 76.0 nm is significantly higher compared to a smooth surface with Ra = 13.0 nm. Furthermore, the oxide scale on the rough surface has some micro defects and protrusion compared to smooth surfaces. Besides that, under the applied external pressure and surface roughness, more pressure- and roughness-induced cracks and discontinuity have been observed on the oxide scale. Graphical Abstract: (Figure presented.
Proceedings of the National Conference on Managing Irrigation for Environmentally Sustainable Agriculture in Pakistan, Islamabad, November 5-7, 1996. Volume III - Papers on the theme, Water management below the Mogha
No full textWater allocationWater distributionWatercoursesIrrigation waterIrrigation canalsWaterloggingSalinityWater useDecision makingSurface drainageIrrigation designIrrigation requirementsSprinkler irrigationWheatSurface irrigationIrrigation schedulingCottonCrop yieldSoil reclamationSodic soilsSoil salinityConjunctive useGroundwaterSurface waterFlow measurementIrrigation practicesMonitoringEvaluationFarmer participationFarmers' attitudes
Influence of Sintering Temperature on the Structural, Morphological, and Electrochemical Properties of NiO-YSZ Anode Synthesized by the Autocombustion Route
No full textIn this study, nickel oxide–Y2O3-doped ZrO2 (NiO-YSZ) composite powder as an anode material was synthesized using a cost-effective combustion method for high-temperature solid oxide fuel cell (SOFC). Further, the effects of sintering temperatures (1200, 1300, and 1400 °C) were studied for its properties in relation to the SOFC performance. The prepared and sintered NiO-YSZ materials were characterized for their surface morphology, composition, structure, and conductivity. The cubic crystalline nature of NiO and YSZ was sufficed by X-ray diffraction, and SEM images revealed an increase in the densification of microstructure by an increase in the sintering temperature. EDX spectrum confirmed the presence of nickel, yttrium, and zirconia without any impurity. Conductivity measurements, under a hydrogen environment, revealed that NiO-YSZ, sintered at 1400 °C, exhibits better conductivity compared to the samples sintered at lower temperatures. Electrochemical performance of button-cells was also evaluated and peak power density of 0.62 Wcm−2 is observed at 800 °C. The citrate combustion method provided peak performance for cells containing anode sintered at 1200 °C, which was previously reported at higher sintering temperatures. Therefore, the citrate combustion method is found to be a suitable route to synthesize NiO-YSZ at low sintering temperature.Rivers, Ports, Waterways and Dredging Engineerin
Modification in electrical conductivity correlated with surface, structural & optical characteristics of graphite ions implanted CR-39
No full textIon implantation of laser induced graphite plasma has been performed for modifications in surface, optical, electrical and structural properties of CR-39. KrF Excimer laser (248 nm, 18 ns, 120 mJ), at an irradiance of 2.5 × 108 W cm−2 is utilized for the production of graphite plasma. The energy and fluence of graphite ions are estimated by Thomson parabola technique. The targets are implanted with energy of 710 KeV graphite ions for four fluences ranging from 26 × 1012 to 92 × 1015 ions/cm2, in presence of magnetic field of strength 90 mT. The digital optical analysis reveals well-arranged dendritic and island like structure formation on irradiated polymer surface. Confocal microscopic investigation illustrates the growth of nano/micro sized craters and hillocks for various ion fluences. Dissociation of bonds along with formation of new bonds is confirmed from Raman analysis. UV–Vis spectral analysis reveals that the optical transmittance values for visible regions of CR-39 are drastically reduced from 90 % to 68 % for maximum laser fluence of 92 × 1015 ions.cm−2. Significant improvement in electrical conductivity is achieved from 10−9 to 10−7 Scm−1 for lowest fluence value of graphite ions. SRIM software is utilized for the measurement of stopping power or Linear Energy Transfer (LTE) of 710 Kev graphite ions, is about, 55.53 eV/Ǻ, in the CR-39 targets
Structural, Electrical and Dielectric Properties of Pyrochlore LaCrZr2-xGexO7 Nanospheres
No full textA series of pyrochlore LaCrZr2-xGexO7 (0.0 <= x <= 1.0) zirconate nanospheres have been synthesized by hydrothermal process. All the zirconate nanospheres crystallize in single phase cubic structure as confirmed by powder X-ray diffraction studies. Electrical conductivity has been analyzed in the temperature range from 300 to 673 K. The relation of DC electrical conductivity with temperature revealed a metal-to-semiconductor behavior with increase in Ge substituents concentration. Further, dielectric properties determined in the frequency range of 60 KHz to 1 MHz are in good agreement with electrical conductivity. These results indicate potential use of these zirconate spheres in switching application due to increased electrical resistivity and decreased dielectric constant on Ge substitution. AC conductivity and electric modulus Cole-Cole plots as a function of frequency reveal the dominant contribution of grain boundaries in the hoping conduction mechanism. It is also observed that the AC activation energy is lower than the DC activation energy.SCI(E)ARTICLE85740-57441
Evaluation of BaZr0.8X0.2 (X= Y, Gd, Sm) proton conducting electrolytes sintered at low temperature for IT-SOFC synthesized by cost effective combustion method
No full textIn present work, perovskite structured proton conducting electrolyte materials BaZr0.8Y0.2 (BZY), BaZr0.8Gd0.2 (BZGd) and BaZr0.8Sm0.2 (BZSm) synthesized by cost effective combustion method are investigated for intermediate temperature solid oxide fuel cell (IT-SOFC). The synthesized BZY, BZGd and BZSm materials are sintered at low temperature (1150 degrees C) and the effect of low sintering temperature on electrolyte properties are also explored. Microstructure, surface morphology, elemental composition, functional group and weight loss are studied using different characterization techniques like XRD, SEM, EDX, FTIR and TGA. XRD shows cubic perovskite structure of all synthesized materials. Secondary phase of Y2O3 is observed in BZY while BaO is observed in BZGd and BZSm due to low sintering temperature. SEM micrographs reveals dense microstructure of BZSm compared to BZY and BZGd. EDX analysis confirms the required material composition within all samples with no impurities. FTIR shows the presence of hydroxyl group and metal oxides and it is observed that BZY exhibit more structural symmetry compared to BZSm and BZGd. Highest conductivity observed (2.2 x 10(-3) S/cm) for BZY due to its structural symmetry and characteristic to prefer B-site of perovskite. Also significant power densities of 0.34 Wcm(-2), 0.24 Wcm(-2) and 0.32 Wcm(-2) for BZY, BZGd and BZSm electrolytes based cells at 650 degrees C implies that BZY, BZGd and BZSm can be used as IT-SOFC electrolytes. (C) 2019 Elsevier B.V. All rights reserved.</p
