Elegant Surface of CoNi Alloys toward Efficient Magnetorheological Performances Realized with Carbon Quantum Dots

Abstract

of superwetting surfaces. [3,4] Up to now, many methods have been developed to produce superhydrophobic surface via creating rough structures or attaching small particles on the surface through various strategies. [5][6][7] Nowadays, transition metals cobalt (Co) and nickel (Ni) and their bimetallic alloys are of great interest on account of their unique and desirable properties, such as high values of saturation magnetization (M s ), excellent mechanical strength, and facile synthesis routes. [8,9] The CoNi alloys have been used in many fields, such as catalysis, microwave absorption, biomedical devices, and magnetic resonance imaging. [10][11][12] In general, the applications of CoNi alloys depend on two factors: chemical composition and morphology, which determine their intrinsic magnetic moment, magnetic permeability, and wettability. In general, Co-rich CoNi alloys possess high values of M s . Stimuli control of magnetic particles is a challenge for basic research, whereas it is a promising way for advanced applications. In contrast to conventional carbonyl iron particles, Co, Ni, and their bimetallic alloys provide a viable alternative for magnetorheological (MR) materials owning to their high values of M s and good controllability for their morphology.MR fluids are a kind of intelligent materials, which usually consist of micrometer-sized magnetizable particles dispersed in a liquid media. [13][14][15] When exposed to an external magnetic field, the dispersed particles get magnetized and develop magnetic moments, which give rise to strong magnetostatic attraction between adjacent particles and consequently build up aligned fiber-like structures. [15,16] The resulting field-induced structures hinder the free flow of the former Newtonian fluid, and high values of the yield stress and viscosity are observed, which is called MR effect. [17] Applications based on MR fluids, such as couplings, actuators, clutches, and vibration dampers, employ the shearing and squeezing strength of MR fluids. [18][19][20] The hottest topics on MR fluids are finding ways to improve their yield stress, stability upon settling, and activity over a wide temperature range. Current fundamental research on MR fluids mainly focuses on the alleviation of settling issues for MR suspensions, which may restrict their use in practical applications. To achieve this goal, several promising strategies Designing and fabricating a rational surface architecture is one of the critical factors to achieve desirable physical and chemical properties and still remains an immense challenge. Herein, a series of CoNi-based hierarchical microspheres with different surface morphologies, including litchi-like, seed-of-plane-tree-like, and waxberry-like shapes, are obtained via surface nucleation of carbon quantum dots (CQDs) with different concentrations in liquid polyol. Microstructure investigations suggest that all the CoNi microspheres are uniformly with enhanced surface roughness with the increasing concentration of CQDs. This study provides insight into...

Review of Carbon and Graphene Quantum Dots for Sensing

“…The variety of properties discussed above for CQDs and GQDs make them potential for applications in bioimaging and sensing. ,, It is envisaged in particular that CQDs could be employed as fluorescent probes for the detection of various analytes due to their intrinsic fluorescent properties. In general, the sensors prepared thus far with CQDs and GQDs can be divided into luminescence sensors, electrochemical sensors, optical biosensors, electrochemical biosensors, and photoelectrochemical (PEC) biosensors.…”

Bimetal Synergistic Effect Induced High Reversibility of Conversion-Type Ni@NiCo2S4 as a Free-Standing Anode for Sodium Ion Batteries

“…Furthermore, ex situ XRD (Figure a) and ex situ XPS (Figure c,d) were performed on three electrodes in the discharge state after 100 cycles. Compared to those of Ni@CoS x , the XRD peak positions of Co of Ni@NiCo 2 S 4 shifted to the peak of Ni, revealing that Co and Ni atoms have penetrated each other’s crystal lattices partly and formed an alloyed phase during long-term cycles . The size of the discharge products calculated by the Scherrer equation showed the smallest size of the Na 2 S, Ni, and Co products in Ni@NiCo 2 S 4 electrodes, suggesting the bimetallic alloy could alleviate the growth of the product crystalline grain during the multicycle conversion reaction (Figure b).…”

“…Compared to those of Ni@ CoS x , the XRD peak positions of Co of Ni@NiCo 2 S 4 shifted to the peak of Ni, revealing that Co and Ni atoms have penetrated each other's crystal lattices partly and formed an alloyed phase during long-term cycles. 47 The size of the discharge products calculated by the Scherrer equation showed the smallest size of the Na 2 S, Ni, and Co products in Ni@NiCo 2 S 4 electrodes, suggesting the bimetallic alloy could alleviate the growth of the product crystalline grain during the multicycle conversion reaction (Figure 4b). Compared with those of pure Ni and Co sulfide, the binding energies of the Ni and Co peaks in Ni@ NiCo 2 S 4 in the discharge state were slightly positive and negative, respectively.…”

Bio-Inspired Passion Fruit-like Fe3O4@C Nanospheres Enabling High-Stability Magnetorheological Performances

“…The MR effects (such as yield stress, viscoelasticity, apparent viscosity, etc.,) mainly depend on the intensity of magnetic field and the volume fraction of the magnetic particles. Many paramagnetic particles, including carbonyl iron (CI), − Fe 3 O 4 nanoparticles, and CoNi alloys, , have been extensively utilized as MR particles because of their certain advantages, such as superior saturation magnetization ( M s ), small coercive force, and an appropriate particle size. , Despite there are several successful applications in industries, the wide applications of MR fluids are still severely limited in accurate control fields because of their inferior stability arising from the density mismatch and weak wettability between the magnetic particles and the continuous mediums . Over the past decade, much effort has been devoted to solving the stability problem, such as coating protective layers on magnetic particles, addition of fillers, or use of viscoplastic carrier mediums .…”