Publications by authors named "Siu Wing Or"

Metal chalcogenides are primarily used for thermoelectric applications due to their enormous potential to convert waste heat into valuable energy. Several studies focused on single or dual aliovalent doping techniques to enhance thermoelectric properties in semiconductor materials; however, these dopants enhance one property while deteriorating others due to the interdependency of these properties or may render the host material toxic. Therefore, a strategic doping approach is vital to harness the full potential of doping to improve the efficiency of thermoelectric generation while restoring the base material eco-friendly.

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High performance of an electrode relies largely on scrupulous design of nanoarchitectures and smart hybridization of bespoke active materials. Here, a 3D heterostructured core-shell architecture was fabricated as a supercapacitor electrode, in which Co3O4 nanowire cores were grown on nickel foam prior to the in situ deposition of layered double hydroxide (LDH) nanosheet shells. Owing to the unique configuration and hybridization, the as-fabricated Co3O4@LDH core-shell electrode exhibited high capacities of 818.

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As a step towards efficient and cost-effective electrocatalytic cathodes for Li⁻O₂ batteries, highly porous hausmannite-type Mn₃O₄ hollow nanocages (MOHNs) of a large diameter of ~250 nm and a high surface area of 90.65 m²·g were synthesized and their physicochemical and electrochemical properties were studied in addition to their formation mechanism. A facile approach using carbon spheres as the template and MnCl₂ as the precursor was adopted to suit the purpose.

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A novel gradient-type magnetoelectric (ME) current sensor operating in magnetic field gradient (MFG) detection and conversion mode is developed based on a pair of ME composites that have a back-to-back capacitor configuration under a baseline separation and a magnetic biasing in an electrically-shielded and mechanically-enclosed housing. The physics behind the current sensing process is the product effect of the current-induced MFG effect associated with vortex magnetic fields of current-carrying cables (i.e.

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We report, theoretically and experimentally, the realization of a high detection performance in a novel magnetoelectric (ME) transverse gradient sensor based on the large ME effect and the magnetic field gradient (MFG) technique in a pair of magnetically-biased, electrically-shielded, and mechanically-enclosed ME composites having a transverse orientation and an axial separation. The output voltage of the gradient sensor is directly obtained from the transverse MFG-induced difference in ME voltage between the two ME composites and is calibrated against transverse MFGs to give a high detection sensitivity of 0.4-30.

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An elasto-magnetic (EM) and magneto-electric (ME) effect based elasto-magneto-electric (EME) sensor has been proposed recently by the authors for stress monitoring of steel cables with obvious superiorities over traditional elasto-magnetic sensors. For design optimization and engineering application of the EME sensor, the design theory is interpreted with a developed model taking into account the EM coupling effect and ME coupling effect. This model is able to approximate the magnetization changes that a steel structural component undergoes when subjected to excitation magnetic field and external stress, and to simulate the induced ME voltages of the ME sensing unit located in the magnetization area.

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Magnetite (Fe3O4) hollow nanospheres with an average diameter of 300 nm and an average shell thickness of 40 nm were synthesized by a surfactant-free solvothermal reduction method, and their structure and electromagnetic (EM) properties were investigated. The Fe3O4 hollow nanospheres showed single-crystalline features along the [111] crystal growth direction and a ferrimagnetic behavior at room temperature. The Fe3O4 hollow nanosphere/paraffin composites exhibited a flatter response in the real complex relative permittivity (epsilon') and a lower value of -0.

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A force sensing device capable of sensing dc (or static) compressive forces is developed based on a NAS106N stainless steel compressive spring, a sintered NdFeB permanent magnet, and a coil-wound Tb(0.3)Dy(0.7)Fe(1.

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Ternary Pb(In(1/2)Nb(1/2))O(3)-Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PIN-PMN-PT) single crystal was investigated for potential application in ultrasonic linear array. Orientation and temperature dependences of height extensional electromechanical coupling coefficient k'(33) for PIN-PMN-PT single crystal were studied. It was found that the [001] poled PIN-PMN-PT diced along the [100] direction would achieve a maximum k'(33) (~87%) and the service temperature was up to 110 °C.

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We report an enhanced magnetoelectric (ME) effect in a heterostructure consisting of a long-type, longitudinally-longitudinally polarized 0.71Pb(Mg(1∕3)Nb(2∕3))O(3)-0.29PbTiO(3) (PMN-PT) piezoelectric single-crystal transformer with its input part sandwiched between two longitudinally magnetized Tb(0.

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A sandwich composite consisting of one layer of ferromagnetic shape memory Ni-Mn-Ga crystal plate bonded between two layers of piezoelectric PVDF polymer film was fabricated, and its magnetic field-induced strain (MFIS) and magnetoelectric (ME) effects were investigated, together with a monolithic Ni-Mn-Ga crystal, as functions of magnetic fields and mechanical load. The load-free dc- and ac-MFISs were 0.35 and 0.

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In this paper we theoretically and experimentally present a nonresonant vibration energy harvesting device based on the shear mode of 0.71Pb(Mg(1/3)Nb(2/3))O3-0.29PbTiO3 single crystals.

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