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•This study found that an anionic triblock copolymer can be used as the dispersant candidate to obtain alumina suspension with cost-effective, suspension-excellent, and uniform ...particle size.•The adsorption isotherm indicated that the adsorption of dispersants on alumina particles was consistent with Langmuir model and the adsorption intensity of PAEG was extremely high, and the total potential energy between particles in suspension with different dispersants was calculated for theoretical analysis of the inter-particle interactions.•The stabilization mechanisms of PEG (polyethylene glycol), PAAS (sodium polyacrylate), and PAEG (their triblock copolymer PAA-b-PEG-b-PAA) dispersants were proposed as the steric stabilization mechanism, electrostatic stabilization mechanism, and electrosteric stabilization mechanism, respectively.•This suspension not only can be used for efficient processing of super-hard semiconductor materials (such as SiC, GaN and sapphire substrates) but also has reference significance for manufacturing other pure metals (such as tungsten, nickel and steel).
The dispersion stability of alumina suspensions is an obstacle to its large-scale application for chemical mechanical polishing (CMP) since the aggregation of particles will cause scratches on the wafer surface during polishing. Therefore, this study was devoted to improving the physicochemical properties of alumina suspensions using different polymeric dispersants, including polyethylene glycol (PEG) with nonionic properties, sodium polyacrylate (PAAS) with anionic properties, and their triblock copolymer poly(acrylic acid)-b-PEG-b-poly(acrylic acid) (PAEG). The characterization results of dispersion stability showed that, compared with PEG and PAAS, the suspensions containing a suitable dosage of PAEG exhibited the advantages of low-viscosity (Viscosity < 3 mPa·s), good-stability (Zeta potential < -50 mV), and monodisperse (Polydispersity index < 0.1). The adsorption isotherm indicated that the adsorption of dispersants on alumina particles was consistent with Langmuir model. Furthermore, the total potential energy between particles in suspension was calculated for theoretical analysis of the inter-particle interactions. Besides, the dispersion mechanisms of PEG, PAAS, and PAEG were proposed as steric stabilization, electrostatic stabilization and electrosteric stabilization, respectively. Finally, CMP experiments showed that the suspension prepared by using PAEG as a dispersant to polish SiC substrates resulted in better removal rates (382 nm/h) and lower surface roughness (Ra: 1.85 nm).
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•A novel chemical mechanical polishing (CMP) efficiency-enhancement method for SiC substrate based on the synergistic effect of mixed abrasive slurry (MAS) and photocatalysis is ...proposed for the first time.•Compared with a single Al2O3 abrasive slurry, the material removal rate increase from 318 nm/h to 694 nm/h and Ra reduces from 2.12 nm to 0.489 nm for polishing SiC substrates by using the MAS (consisted of Al2O3 and ZrO2 particles) under UV irradiation.•We summarize this SiC-CMP efficiency-enhancement method into two steps, including ball milling to prepare MAS and polishing under UV irradiation, and provide an in-depth analysis of the improvement mechanism.•This research also has important reference significance for difficult-to-process materials (such as GaN) with extremely high hardness and strong chemical inertness.
Silicon carbide (SiC) is challenging to process by chemical mechanical polishing (CMP) given its anomaly mechanical hardness and chemically inert. However, improving the SiC-CMP performance including machining efficiency and surface quality is critical for developing power semiconductor devices with low cost, high efficiency, and high stability. Here, this research aims at combining mixed abrasive slurry (MAS) with photocatalytic effect in the SiC-CMP process, thus enabling an efficient enhanced CMP technology with low-cost and high-performance. Specifically, this paper describes the fabrication process of MAS through a high-energy ball milling method and discusses the polishing performance of the slurry with or without the presence of UV irradiation. By using MAS consisting of Al2O3 and ZrO2 abrasives, a material removal rate of 694 nm/h and surface roughness (Ra) of 0.489 nm can be obtained under UV irradiation. Additionally, the abrasive morphology, element composition, particle size distribution, Zeta potential, and its chemical effect of the MAS are also analyzed. In particular, a two-step strategy, namely the preparation of MAS and polishing with UV irradiation, is proposed to enhance the SiC-CMP efficiency, and an in-depth analysis of the improvement mechanism for each step is discussed.
Chemical mechanical polishing (CMP) has revolutionized the processing of semiconductor material such as silicon carbide (SiC). However, the strong chemical bond between silicon atoms and carbon atoms ...gives SiC materials a very high mechanical hardness and chemical stability. Therefore, SiC wafers may suffer from a low material removal rate (MRR) and serious subsurface damage when traditional CMP methods are used. In this study, to improve the CMP properties of Si-face of the 4H-SiC wafers, the synergistic effect of UV and TiO2 on the activation of persulfate (PS) was investigated for the first time. The response surface method was employed to study the effect of pH, PS concentration, and TiO2 dosage on CMP in-depth, and to ultimately optimize the polishing process. The analysis demonstrated that an MRR of 608 nm/h can be obtained with the average surface roughness (Sq) of 0.521 nm when the pH is 6, in which the TiO2 dosage is 0.015 wt% and the PS concentration is 3 wt%. Polarization curves, AC impedance spectra and X-ray photoelectron spectroscopy tests were performed to further analyze the chemical action of the slurry, which showed that the introduction of UV-TiO2 strongly enhances the chemical action of slurry and results in the formation of a passivated layer on the SiC surface. Finally, based on the radical quenching experiments and the results mentioned above, a model that relates to the removal of 4H-SiC by UV-TiO2 synergistic activation of PS is proposed.
Traditional synthesis/analysis sparse representation models signals in a one dimensional (1D) way, in which a multidimensional (MD) signal is converted into a 1D vector. 1D modeling cannot ...sufficiently handle MD signals of high dimensionality in limited computational resources and memory usage, as breaking the data structure and inherently ignores the diversity of MD signals (tensors). We utilize the multilinearity of tensors to establish the redundant basis of the space of multi linear maps with the sparsity constraint, and further propose MD synthesis/analysis sparse models to effectively and efficiently represent MD signals in their original form. The dimensional features of MD signals are captured by a series of dictionaries simultaneously and collaboratively. The corresponding dictionary learning algorithms and unified MD signal restoration formulations are proposed. The effectiveness of the proposed models and dictionary learning algorithms is demonstrated through experiments on MD signals denoising, image super-resolution and texture classification. Experiments show that the proposed MD models outperform state-of-the-art 1D models in terms of signal representation quality, computational overhead, and memory storage. Moreover, our proposed MD sparse models generalize the 1D sparse models and are flexible and adaptive to both homogeneous and inhomogeneous properties of MD signals.
Room temperature vulcanized (RTV) silicone rubber-g-polyhedral oligomeric silsesquioxanes (POSS) was prepared and its thermal degradation behavior and thermo-oxidative stability were investigated by ...thermogravimetric analysis (TGA). The results demonstrated that the chemical incorporation of POSS into polydimethylsiloxane (PDMS) chains significantly enhanced thermal stability of RTV silicon rubber in both nitrogen and air atmosphere. The degradation behavior was further monitored by TGA coupled with real time Fourier transform infrared spectra (FTIR), and the residues were characterized by FTIR and X-ray photoelectron spectroscopy (XPS). It was found that the remarkable improvement in thermal stability could be attributed to the following reasons: (1) the branched structure of RTV silicone rubber-g-POSS and interaction between POSS molecules and PDMS chains; (2) POSS traps generated and grafted or cross-linked structure formed; (3) intumescent ceramic protective barrier formed; (4) the perfect distribution of POSS in RTV silicone rubber-g-POSS.
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By considering the increasing importance of screen contents, the high efficiency video coding (HEVC) standard includes screen content coding as one of its requirements. In this paper, we demonstrate ...that enabling frame level block searching in HEVC can significantly improve coding efficiency on screen contents. We propose a hash-based block matching scheme for the intra block copy mode and the motion estimation process, which enables frame level block searching in HEVC without changing the HEVC syntaxes. In the proposed scheme, the blocks sharing the same hash values with the current block are selected as prediction candidates. Then the hash-based block selection is employed to select the best candidates. To achieve the best coding efficiency, the rate distortion optimization is further employed to improve the proposed scheme by balancing the coding cost of motion vectors and prediction difference. Compared with HEVC, the proposed scheme achieves 21% and 37% bitrate saving with all intra and low delay configurations with encoding time reduction. Up to 59% bitrate saving can be achieved on sequences with large motions.
Most reported wearable electronic devices lack self-healing chemistry and flexible function to maintain stable energy output while irreversible damages and complex deformations. In this work, we ...report a dual-dynamic network electrolyte synthesized by micellar elastomers introduced into strong hydrogel matrix. The gel electrolyte is fabricated by physically cross-linking the borax-polyvinyl alcohol (B-PVA) network as tough matrix and poly (ethylene oxide) (PEO)-poly (propylene oxide) (PPO)-poly (ethylene oxide) (Pluronic) to frame elastic network, followed by immersion in potassium chloride solution. Under the action of dynamic borate ester bond and multi-network hydrogen bond, the as-prepared electrolyte exhibits high stretchability (1535%) and good self-healing efficiency. Based on the electrolyte, we assemble the interfacial compatible micro-supercapacitor (MSC) by multi-walled carbon nanotubes (MWCNT) interdigital electrode printed on cellulosic paper by direct ink writing (DIW) technique. Thanks to the large specific area and compressive deformation resistance of cellulosic paper, the MSC with tightly interfacial contact achieves high volumetric capacitance of 801.9 mF cm
at the current density of 20 μA cm
. In the absence of stimulation of the external environment, the self-healing MSC demonstrates an ideal capacity retention (90.43%) after five physical damaged/healing cycles. Our research provides a clean and effective strategy to construct wearable MSC.
The power sector bears significant responsibility for achieving carbon neutrality. Low-carbon, high-flexibility generation technologies are pivotal in the generation mix of the foreseeable future. In ...this paper, a mixed-integer operation model of combined-cycle gas-turbine generators is developed, featuring a new mode-based modeling of post-combustion carbon capture plants. The model is applied to a day-ahead adaptive robust unit commitment problem considering wind power uncertainties. Numerical results from a case study on a modified 39-bus benchmark system demonstrate the correctness and practicality of the model. Compared to the linear model widely adopted in the literature, the proposed mode-based model achieves a 4.91% wider operating range in the net electric power output. Besides, the initial solvent ratio is identified as a non-negligible parameter for the short-term operation of carbon capture plants, whose optimal setting leads to a wider operating range in the net electric power output of up to 21.96%.
•The coaxial binary composite MnO2/polyaniline was prepared.•The coaxial structure is convenient for the ion and electrons transportation.•The MnO2/polyaniline composite exhibit excellent capacitive ...behavior.•The assembled asymmetric supercapacitor displays high performance.•The composite can produce microsupercapacitor combining 3D-printed stamp.
Controllable design over the structure and morphology of activematerial is highly desirable for high performance supercapacitors. Here,coaxial binary composite MnO2/polyaniline was prepared by introducing tetraphenyl porphyrin tetrasulfonic acid interlayer (TPPS), as a crosslinking agent and dopant, to fabricate the three-dimensionalhollowpolyaniline (PANI) nanotube gel and then synthesizing nanoflaky MnO2 uniformly on the surface of PANI. Moreover, this coaxial structure is convenient for the ion and electrons transportation to exhibit excellent capacitive behavior with the capacitance of 575 F/g at 0.4 A/g. In addition, we assembled an asymmetric supercapacitor using MnO2/PANI as positive electrode, displaying high energy density (52.7 Wh/kg), remarkable durability and long cycling life (maintaining 90.2% initial capacitance after 2000 cycles). Using MnO2/PANI as inks for 3D-printed stamping is promising to be a novel fabricating method which can rapidly produce flexible microsupercapacitor for wearable micro devices.
This study accounts the controllable design over the structure and morphology of Ni-P nanomaterials directly growing on cellulose paper, and its excellent non-enzymatic electrocatalytic performance ...to urea. The Ni-P papers were prepared by simple solution soaking and electroless bathing. And the simple experimental steps and mild experimental conditions make it possible for large-scale industrial production, and potential for practical applications. In addition, tuning the pH and concentration of the electroless bath, the Ni-P nanomaterials with different morphologies of nanoflower, nanosheet, nanowire microsphere and microsphere were obtained. The Ni-P nanomaterials impart conductivity to cellulose paper while being potently sensitive to urea owing to its high catalytic activity. Cellulose paper has a large specific area and open macroporous framework which hadn't been damaged during the process of electroless bathing, providing much more activated sites for Ni-P deposition. And the prepared Ni-P papers, as composite materials of cellulose papers loading Ni-P nanomaterials, have high electrocatalytic properties to urea. Comparing the electrochemical behaviors of the four Ni-P paper electrodes with different morphologies, the Ni-P nanoflower paper electrode showed the best electrochemical performance with highest sensitivity of 683.46 μA mM−1 cm−2 in the low concentration range (0–1 mM) and 1140 μA mM−1 cm−2 in the high concentration range (1–11 mM), lowest detection limit of 12 μM, shortest response time of 3 s, which may owes to the highest surface area of the Ni-P nanoflower structure. It also has a good stability in room environment remaining 97% after 35 days of storage. Moreover, the electrocatalytic activities of the four Ni-P paper electrodes are ranked as follows: nanoflower > nanosheet > nanowire microsphere > microsphere. What's more, the long-term stability and repeatability, good selectivity of the flexible Ni-P paper make it successfully applied to swimming pool water quality monitoring.
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