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- 저자 : Liaqat Usman (검색결과 6 건)
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Effects of Incorporating Steel and Glass Fibers on Shear Behavior of Concrete Column-Beam Joints
Liaqat Ali Qureshi,Usman Muhammad 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.8
This paper presents the effects of adding steel and glass fibers on structural behavior of concrete column-beam joints in comparisonwith the conventional concrete. Nine full-scaled exterior column-beam joints cast by one traditional concrete (declared as controlcolumn-beam joint), four steel fiber reinforced & four glass fiber reinforced concretes were tested under monotonic loading. Percentage of each fiber added in respective column-beam joint was varied from 0 to 2% with an increment of 0.5%. Steel fiberswere added on weighted basis of concrete while glass fibers were added on the weighted percentage of cement. Results wereevaluated with respect to first crack load, ultimate load, deflections and crack patterns. Finite element modeling was carried out onANSYS version 11 by using material properties evaluated by physical testing of concrete used in the casting of joints. Resultsobtained from FEM and experimental program were found to be in good agreement with each other. It was also found that theincorporation of fibers in column-beam joints improved their stiffness, ductility, strength and it could be one of the likely alternateapproaches for reducing the overcrowding of lateral reinforcement in column-beam joints.
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Elizbit,Liaqat Usman,Hussain Zakir,Baig Mutawara Mahmood,Khan Muzamil Ahmad,Arif Dooa 한국세라믹학회 2021 한국세라믹학회지 Vol.58 No.5
Due to porous structure, larger specifi c area, and potential to functionalize further, metal–organic frameworks (MOFs) are gaining attention in various fi elds, including electrochemical sensing of various analytes. MOFs are known to have excellent electrochemical activity because they mainly constitute a rich metallic center, possess huge specifi c area, and have multiple valence states. However, electrocatalytic activities of MOFs are greatly reduced due to their poor electronic conductivity for which high conductivity species are incorporated into the MOFs. In the present work, Co-based MOF (ZIF-67) was used as a porous matrix to encapsulate silver nanoparticles (Ag NPs) and on the surface of ZIF-67 multi-walled carbon nanotubes (MWCNTs) were decorated to obtain Ag@ZIF-67/MWCNT nanocomposite for the non-enzymatic electrochemical detection of glucose. The surface morphology of the synthesized nanocomposite was investigated by scanning electron microscopy, while crystallographic characterization was performed by X-ray powder diff raction. Cyclic voltammetry and chronoamper- ometry techniques were used to for the electrochemical monitoring of glucose. The electrochemical results demonstrated that Ag@ZIF-67/MWCNT showed an improved catalytic activity towards glucose in the concentration range of 33 μM to 400 μM with a low detection limit of 0.49 μM (S/N = 3), and reaction sensitivity of 13.014 μA μM −1 cm −2 as well as good selectivity in presence of ascorbic acid and uric acid.
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Bone whitlockite: synthesis, applications, and future prospects
Batool Sadaf,Liaqat Usman,Babar Bushra,Hussain Zakir 한국세라믹학회 2021 한국세라믹학회지 Vol.58 No.5
Bone whitlockite (WH) exists in the collagen matrix along with hydroxyapatite (HA) and plays a vital role during earlier stages of bone development. It is present in short-range order and is diffi cult to identify in the bone, as compared to HA mineral, that covers 80% of the bone inorganic phase. It has the same structural analogy with β-TCP, but detailed structural and crystallographic analyses of bone have shown that β-tricalcium phosphate (β-TCP) is merely a synthetic analog of bone whitlockite, having the same crystalline structure but diff erent chemically. WH contains magnesium at Ca(IV), Ca(V) positions, and HPO 4 2− on a threefold axis in a rhombohedral crystal lattice. Its biocompatibility, functionality, negative surface charge, mechanical strength, and stability in physiological solvents make it an ideal bone substitute as compared to hydroxyapatite (HA) and β-TCP. It has magnesium as a major component that has a strong affi nity with integrin protein. Integrin protein plays a vital role in bone tissue integration. It is bioresorbable and biodegradable and the rate of degradation complements with regeneration. However, despite these excellent properties, this material has always been overshadowed by other calcium phosphates (CaPs), because it is diffi cult to synthesize. In this review article, we present a comprehensive study on the diff erence in the crystalline structure of bone whitlockite and β-TCP, its presence in the natural system, and conditions under which its nucleation occurs in native bone and at lab scale. Furthermore, the reaction conditions that favor homogenous precipitation of synthetic WH and the role of magnesium in the stabilization of diff erent CaPs to obtain pure WH phase are also discussed. Finally, the applications of WH in biomedical and for heavy metal adsorption are summarized.
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Awan Anum Ayub,Liaqat Usman,Hussain Zakir 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.6
Hydroxyapatite (HAP) is a prominent bioceramic, notably used in the biomedical field. Fundamental properties of the biomaterials are size and shape dependent. High purity, morphology, and size are the main properties to be addressed for clinical application. Therefore, this work reports the effect of pH and annealing temperature on HAP's shape, crystallite, and particle size. Morphologically different hydroxyapatite nanostructures are synthesised by wet chemical precipitation. Furthermore, the pH of the solution varied from 6 to 11, and the calcination temperature was changed from 300 °C to 900 °C. Various morphologies of hydroxyapatite nanopowders, such as spherical, distorted boxes, aggregated rods, flakes, and beaded rods-like clusters, have been achieved. Moreover, small crystallite and particle sizes of HAP were observed in an alkaline medium. The spherical-shaped hydroxyapatite with particle size between 21.54 nm to 78.89 nm was obtained at pH 11. In contrast, beaded rods, nanorods, nanoflakes and distorted boxes-like morphology with an average particle size between 28.28 nm and 202.43 nm were successfully synthesised in neutral to moderately basic pH. Moreover, the crystallite size between 8.4 to 77.7 nm was achieved by changing the pH and annealing temperature. The synthesised products were analysed by XRD, FTIR, Raman spectroscopy and SEM to determine the crystallinity, purity, chemical composition, vibrational modes, morphology, and particle size.
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