| 1. |
- Hakeem, Abbas Saeed, et al.
(författare)
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Synthesis and characterization of alkaline earth and rare earth doped sialon Ceramics by spark plasma sintering
- 2021
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Ingår i: International journal of refractory metals & hard materials. - : Elsevier. - 0263-4368. ; 97
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Tidskriftsartikel (refereegranskat)abstract
- Several sialon ceramics compositions were synthesized by selecting metal oxides (MOs) in the nanosize range as additives in the oxynitride network. Nanosized precursors, including Si3N4, SiO2, AlN, Al2O3, and MO (MO =MgO, CaO, SrO, BaO, Y2O3, La2O3, CeO2, Nd2O3, Eu2O3, Dy2O3, Er2O3 and Yb2O3,) were used in the present study. Probe sonication and spark plasma sintering techniques were used for mixing the powder precursors and subsequent synthesis of sialon ceramics at a relatively low temperature of 1500 ◦C. Formation of α-sialon(general formula represented by Mm/vSi12-(m+n)Alm+nOnN16-n) was investigated for m and n values of 1.1 and 0.6, respectively and their structural, morphological, thermal, and mechanical properties were evaluated. The synthesized samples were characterized using X-ray diffractometry and field emission scanning electron microscopy to study the effect of the MOs on the microstructure and resulting densification, hardness, fracture toughness, thermal expansion, and thermal conductivity. The sialon samples synthesized using the selected MOs exhibited similar relative densities in the range of 96 to 99% among all the samples and Vickers hardness (HV10) values, in the range of 15 to 20.8 GPa, depending on the type of MO. However, RE MOs exhibited a higher HV than AE MOs.Fracture toughness (KIc) was ~4 MPa⋅m1/2 for most of the samples, but the sample doped with Yb2O3 had the highest KIc of 6.3 MPa⋅m1/2. The thermal conductivity decreased as the atomic number (atomic radii) of the AE increases and in the case of RE exhibited a random tendency. On the other hand, the thermal expansion coefficient increased with increasing atomic radii of the AE, and a mixed trend, with values in the range of 2.63 to2.83 ppm⋅K-1, was observed for RE doped sialon ceramics. These behaviors are attributed to the resulting morphology and structure of alpha sialon comprised of both equiaxed and elongated grains. The properties of these sialon ceramics could be tailored by the proper selection of suitable precursors and synthesis parameters.
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| 2. |
- Irshad, Hafiz Musammil, et al.
(författare)
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Effect of Ni content and Al2O3 particle size on the thermal and mechanical properties of Al2O3/Ni composites prepared by spark plasma sintering
- 2018
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Ingår i: International journal of refractory metals & hard materials. - : Elsevier. - 0263-4368. ; 76, s. 25-32
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Tidskriftsartikel (refereegranskat)abstract
- Alumina-nickel composites were prepared by carrying out spark plasma sintering (SPS) of nano-sized and micro-sized Al2O3particles with 15–45 wt% Ni powders. The powder materials were sintered at a temperature of1400 °C under a constant uniaxial pressure of 50 MPa. FESEM micrographs of the products showed uniformlydispersed nickel inclusions in both matrices at intergranular positions. Presence of Al2O3as the major phasealong with Ni as the minor phase was confirmed using XRD analysis. Thermal and mechanical properties of thenano- and micro-sized Al2O3/Ni composites were investigated. The thermal conductivity of nano-sized aluminacomposites was seen to increase with the increase in nickel content, however, an opposite trend was observed formicro-sized alumina-based composites. Moreover, thermal conductivities of all the composites decreased withincrease in temperature. The composites also showed high hardness and fracture toughness values of up to19.6 GPa and 4.71 MPa ∗ m1/2, respectively, and relative density values, between 79 and 99%, that decreasedwith increasing Ni content. Furthermore, the nano-sized Al2O3/Ni composites showed thermal and mechanicalproperties superior to those of the micro-sized Al2O3/Ni composite.
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| 3. |
- Hakeem, Abbas Saeed, et al.
(författare)
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Microstructural and thermal evaluation of the formation of tin-tellurium (Sn-Te) alloy by ball milling process
- 2023
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Ingår i: Powder Technology. - : Elsevier. - 0032-5910 .- 1873-328X. ; 428
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Tidskriftsartikel (refereegranskat)abstract
- A mechanically induced phase transition in tin-tellurium (Sn-Te) system and its dependence on the milling time of the masses of metastable Sn-Te phase(s) produced during ball milling have been investigated. The synthesis approach involves top-down ball milling of elemental Sn and Te powders in an argon environment with a milling time of 1 to 5 h at a low ball milling speed of 300 RPM. The Sn-Te solid solution forms as particles, resulting in large masses due to the ball milling operation. Ball milling of initial micron-sized powders of Sn and Te resulted in a homogenized nano-sized powder mixture. This mechanical mixture of Sn and Te powders exhibiting in-termediate phases with a crystal structure similar to that of elemental Sn and Te were detected in the ball-milled mixtures at various milling times, which resulted in a stable phase that ultimately transformed into a Sn-Te solid solution. Morphological and structural modifications at different stages of ball milling were investigated through X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry, dynamic light scattering, density measurement, and surface analysis. Subsequently, dense pellets were fabricated by spark plasma sintering from synthesized Sn-Te solid-solution powders produced by ball milling for 5 h. The sintered samples showed excellent structural integrity with densities of up to 6.35 g/cm3. It is to be noted that the formation of large quantities of uniform Sn-Te powder alloy produced by ball milling is reported for the first time in this study. These findings could be extended in the future to prepare bulk quantities of many solid solutions of the elements of the same periodic group.
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| 4. |
- Ilyas, Muhammad Tasaduq, et al.
(författare)
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Substantial performance of copper sulfide nanotubes at high current densities for energy storage applications
- 2024
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Ingår i: Journal of Energy Storage. - : Elsevier. - 2352-152X .- 2352-1538. ; 85
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Tidskriftsartikel (refereegranskat)abstract
- This study presents the direct growth of CuS nanotubes (NTs) on nickel foam using a facile solution synthesis route. The structural, elemental and morphological analyses of CuS NTs grown Ni foam were conducted through X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscope, and field emission scanning electron microscope. The electrochemical performance of the prepared electrodes was comprehensively characterized by cyclic voltammetry (CV), galvanostatic charge discharge and electrochemical impedance spectroscopy. The CuS NTs grown electrodes delivered a specific capacitance of 1539 Fg−1 at 1 mVs−1 and 1365 Fg−1 at 5 Ag−1, demonstrating a remarkable rate capability of 66 % at an extremely high current density of 25 Ag−1. Notably, the CuS NTs electrode demonstrated good cyclic stability, as evidenced by a charge retention of 75.5 % after 3000 cycles at a high current density of 20 Ag−1. The charge storage mechanism was predominantly diffusion controlled, accomplished by analyzing CV data. Overall, this work evinces that the as-synthesized CuS NTs hold a significant promise as electrode materials for high-performance electrochemical energy storage applications.
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| 5. |
- Latif, Umar, et al.
(författare)
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In situ growth of nickel ammonium phosphate ribbons on nickel foam for supercapacitor applications
- 2023
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Ingår i: Journal of Energy Storage. - : Elsevier. - 2352-152X .- 2352-1538. ; 73:Part B
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Tidskriftsartikel (refereegranskat)abstract
- We report the in-situ growth of the nickel ammonium phosphate (NAP) ribbons on nickel (Ni) foam in a single step process using hydrothermal approach. The morphology, structure and elemental analysis of the NAP-ribbons grown on Ni foam were analyzed by scanning electron microscope (SEM), energy-dispersive x-ray analysis (EDX) and x-ray diffraction. The NAP-coated Ni foam sample was sonicated in ethanol and the obtained suspension was observed through AFM analysis to analyze the lateral dimensions of the NAP-ribbons. The obtained NAP ribbons powder was also characterized by x-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Further, the NAP ribbons based electrodes were electrochemically characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge discharge analysis (GCD). NAP ribbons grown on Ni foam as electrodes achieved a specific capacitance (Csp) of 1196 Fg- 1 at 1 mVs- 1 and 1188 Fg- 1 at 1 Ag-1. The charge storage mechanism was identified and quantified by evaluating the CV data in 1-10 mVs- 1 scan rate range. It was established that at low scan rate the charge was dominantly stored by diffusion of electrolyte ions within the gaps of the NAP ribbons resulting in high energy density of 105.5 WhKg-1 at 1 Ag-1. NAP electrodes also demonstrated good cyclic stability by showing 92 % charge retention after 5000 cycles. A symmetric 2-elec-trode device comprised of NAP ribbons electrodes gave Csp of 309 Fg-1 at 1 mVs- 1 with energy density of 42.06 Wh/Kg and power density of 0.5 KW/Kg at 1 A/g current density, which is an exceptional for a symmetric supercapacitor device. The study confirms that NAP ribbons have a promising potential to be employed in the next-generation energy storage devices.
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| 6. |
- Mansha, Saira, et al.
(författare)
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Development of pH-Responsive, Thermosensitive, Antibacterial, and Anticancer CS/PVA/Graphene Blended Hydrogels for Controlled Drug Delivery
- 2024
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Ingår i: Gels. - : MDPI. - 2310-2861. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Drug delivery techniques based on polymers have been investigated for their potential to improve drug solubility, reduce systemic side effects, and controlled and targeted administration at infection site. In this study, we developed a co-polymeric hydrogel composed of graphene sheets (GNS), polyvinyl alcohol (PVA), and chitosan (CS) that is loaded with methotrexate (MTX) for in vitro liver cancer treatment. Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) was employed to check the structural properties and surface morphology. Moreover, tests were conducted on the cytotoxicity, hemolytic activity, release kinetics, swelling behaviour and degradation of hydrogels. A controlled release of drug from hydrogel in PBS at pH 7.4 was examined using release kinetics. Maximal drug release in six hours was 97.34%. The prepared hydrogels did not encourage the HepG2 growth and were non-hemolytic. The current study highlights the potential of GNS-based hydrogel loaded with MTX as an encouraging therapy for hepatocellular carcinoma. HepG2 cell viability of MTX-loaded CS-PVA-GNS hydrogel was (IC50 5.87 mu g/200 mL) in comparison to free MTX (IC50 5.03 mu g/200 mL). These outcomes recommend that hydrogels with GNS ensure improved drug delivery in cancer microenvironment while lessening adverse consequences on healthy cells.
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| 7. |
- Raza, Mohsin Ali, et al.
(författare)
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Synthesis and characterization of zinc aluminate electrodes for supercapacitor applications
- 2024
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 475
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Tidskriftsartikel (refereegranskat)abstract
- We report, for the first time, the thorough electrochemical characterization of zinc aluminate spinel. Four different stoichiometric composition of zinc aluminate (ZnAl1.5O3.25, ZnAl2O4, ZnAl2.87O5.30, and ZnAl4O7) were prepared by solution combustion method. The obtained powders after calcination at 1000 °C were characterized through scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDX) and x-ray diffraction to analyze the morphology, elemental composition and structure, respectively, of the zinc aluminate compositions. The electrodes were prepared by coating slurry of zinc aluminate, carbon black and polyvinylidene fluoride on nickel foam in a ratio of 8:1:1. The electrochemical characterization was carried out by cyclic voltammetry (CV), galvanostatic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS). ZnAl1.5O3.25 exhibited the highest specific capacity of 546 C/g at 1 mV/s and 336 C/g at 1 A/g, as appraised by CV and GCD analysis, respectively. EIS test revealed that ZnAl1.5O3.25 had the modest impedance value. The energy density value for ZnAl1.5O3.25 sample was 16.79 Wh/kg at 1 A/g with a power density of 179.9 W/kg. The as developed electrodes showed predominantly pseudo-capacitive charge storage mechanism.
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| 8. |
- Ali, Sharafat, 1976-, et al.
(författare)
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A cubic calcium oxynitrido-silicate, Ca2.89Si2N1.76O4.24
- 2011
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Ingår i: Acta Crystallographica Section E. - 1600-5368. ; 67
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Tidskriftsartikel (refereegranskat)abstract
- The title compound, tricalcium oxynitride silicate, withcomposition Ca3-xSi2N2-2xO4+2x (x ’ 0.12), is a perovskiterelatedcalcium oxynitrido silicate containing isolated oxynitridosilicate 12-rings. The N atoms are statistically disorderedwith O atoms (occupancy ratio N:O = 0.88:0.12) and occupythe bridging positions in the 12 ring oxynitrido silicate anion,while the remaining O atoms are located at the terminalpositions of the Si(O,N)4 tetrahedra. The majority of the Ca2+cations fill the channels along [100] in the packing of the 12-ring anions. The rest of these cations are located at severalpositions, with partial occupancy, in channels along the bodydiagonals.
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| 9. |
- Ali, Sharafat, Associate Professor, 1976-, et al.
(författare)
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A novel approach for processing CaAlSiON glass-ceramics by spark plasma sintering : Mechanical and electrical properties
- 2022
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Ingår i: Journal of the European Ceramic Society. - : Elsevier. - 0955-2219 .- 1873-619X. ; 42:1, s. 96-104
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Tidskriftsartikel (refereegranskat)abstract
- Lithium containing glassy materials can be used as solid electrolytes or electrode materials for lithium-ion batteries due to their high energy density. Conventional melt-quenched Ca11Al14Si16O49N10 glass powder containing 24 e/o N, doped with Li-ions (1, 3, and 6 wt. %) and sintered by spark plasma sintering technique (SPS) was studied. The benefits of using SPS to produce glass-ceramics are rapid heating rates compared to conventional consolidation techniques and tuning of properties, adjusting the temperature, holding time (closed to Tg temperature), heating rate (solidification), and pressure (densification) profile during the heat treatment using SPS. Pure glass and glass-ceramic were obtained under identical SPS conditions and compared with pristine oxynitride and soda-lime-silicate (float) glasses. XRD and SEM analysis confirmed that increasing the amount of Li increases the crystallinity in the glass matrix. Nano-indentation analysis showed a decreased hardness and reduced elastic modulus values with the addition of Li-ions. The direct current conductivity increases with the addition of Li due to the high mobility of Li-ions. However, the float glass sample doped with 6 wt.% of Li exhibits even higher values of D.C. conductivity, than the analogously doped Ca11Al14Si16O49N10 glass. The magnitude of activation energy (more than 1 eV) is typical for an ion hopping mechanism and the D.C. conduction mechanism is dominated by Li+ hopping.
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| 10. |
- Ali, Sharafat, 1976-, et al.
(författare)
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Compositional effects on the properties of high nitrogen content alkaline-earth silicon oxynitride glasses, AE = Mg, Ca, Sr, Ba
- 2011
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 31:4, s. 611-618
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Tidskriftsartikel (refereegranskat)abstract
- A series of alkaline-earth element containing high nitrogen content oxynitride glasses (AESiON), with AE = Mg, Ca, Sr, Ba, were prepared in order to investigate the compositional effects on the physical properties of the alkaline-earth element. The physical properties were found to change linearly with the concentration of AE elements. The density of the glasses increases substantially with an increase in the AE atomic mass and slightly with an increase in nitrogen ratio. Ba containing glasses shows the value of density 4.16 g/cm3. Glass transition temperatures are found to be higher for Mg glasses, ca. 1020 °C, in comparison with Ba glasses, ca. 895 °C. The hardness of Mg containing glasses shows high values, up to 12.2 GPa and decreases for Ca, Sr and Ba containing glasses. Ba, containing glasses shows high values of refractive index in comparison with the Sr, Ca and Mg containing glasses.
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