Publications by authors named "Tielin Shi"

52 Publications

Embedded growth of colorful CsPbX3 (X = Cl, Br, I) nanocrystals in metal-organic frameworks at Room Temperature.

Nanotechnology 2022 Jan 13. Epub 2022 Jan 13.

Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Wuhan, 430074, CHINA.

Herein, we develop a novel strategy for preparing all-inorganic cesium lead halide (CsPbX3, X= Cl, Br, I) perovskite nanocrystals (NCs)@Zn-based metal-organic framework (MOF) composites through interfacial synthesis. The successful embedding of fluorescent perovskite NCs in Zn-MOFs is due to the in-situ confined growth, which is attributed to the re-nucleation of water-triggered phase transformation from Cs4PbBr6 to CsPbBr3. The controllable synthesis of mixed-halide based composites with various emission wavelength can be achieved by adding the desired amount of halide (Cl or I) salts in the re-nucleation process. More importantly, the anion exchange reaction is inhibited among various composites with different halogen atoms by being trapped in MOFs. Besides, a white light-emitting diode (WLED) is produced using a blue LED chip with the green-emitting and red-emitting composites, which has a color coordinate of (0.3291, 0.3272) and a wide color gamut. This work provides a novel route to achieving perovskite NCs growth in MOFs, which also can be extended to the other NCs embedded in frames as well.
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http://dx.doi.org/10.1088/1361-6528/ac4b2dDOI Listing
January 2022

Broadening the Spectral Response of Perovskite Photodetector to the Solar-Blind Ultraviolet Region through Phosphor Encapsulation.

ACS Appl Mater Interfaces 2021 Sep 8;13(37):44509-44519. Epub 2021 Sep 8.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.

Hybrid perovskite photodetectors generally exhibit brilliant performance for photodetecting in the visible spectrum but poor detectability in the solar-blind ultraviolet (UV) region. To break through the bottleneck, we demonstrate a novel strategy to broaden the spectral response of perovskite photodetectors to the solar-blind UV region through phosphor encapsulation. The high photoluminescence quantum yield trichromatic phosphor capping layer achieves an extended spectral response to the solar-blind UV region through effectively down-converting the incident UV light into visible light. In addition, an external quantum efficiency of up to 12.13%@265 nm is achieved without bias voltage, while the initial value is near zero. The corresponding spectral responsivity and detectivity are 0.0269 A/W and 7.52 × 10 Jones, respectively. Thus, the photodetectors show a high photocurrent and on/off ratio, increasing by roughly 2 orders of magnitude. Moreover, the photodetectors exhibit a large linear dynamic range of 105 dB, fast response times of 50.16/51.99 μs, and excellent stability. The practical applications for flame detection and UV-based communication are further explored. This work provides a new way to achieve UV light detection based on perovskite photodetectors. Perhaps, it may also be a promising alternative for wide-band gap semiconductors to realize the urgent pursuit of UV detection.
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http://dx.doi.org/10.1021/acsami.1c09719DOI Listing
September 2021

Molecular Understanding of Electrochemical-Mechanical Responses in Carbon-Coated Silicon Nanotubes during Lithiation.

Nanomaterials (Basel) 2021 Feb 24;11(3). Epub 2021 Feb 24.

State Key Laboratory of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.

Carbon-coated silicon nanotube ([email protected]) anodes show tremendous potential in high-performance lithium ion batteries (LIBs). Unfortunately, to realize the commercial application, it is still required to further optimize the structural design for better durability and safety. Here, the electrochemical and mechanical evolution in lithiated [email protected] nanohybrids are investigated using large-scale atomistic simulations. More importantly, the lithiation responses of [email protected] nanohybrids are also investigated in the same simulation conditions as references. The simulations quantitatively reveal that the inner hole of the SiNT alleviates the compressive stress concentration between a-LiSi and C phases, resulting in the [email protected] having a higher Li capacity and faster lithiation rate than [email protected] The contact mode significantly regulates the stress distribution at the inner hole surface, further affecting the morphological evolution and structural stability. The inner hole of bare SiNT shows good structural stability due to no stress concentration, while that of concentric [email protected] undergoes dramatic shrinkage due to compressive stress concentration, and that of eccentric [email protected] is deformed due to the mismatch of stress distribution. These findings not only enrich the atomic understanding of the electrochemical-mechanical coupled mechanism in lithiated [email protected] nanohybrids but also provide feasible solutions to optimize the charging strategy and tune the nanostructure of SiNT-based electrode materials.
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http://dx.doi.org/10.3390/nano11030564DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7996296PMC
February 2021

A Novel End-To-End Fault Diagnosis Approach for Rolling Bearings by Integrating Wavelet Packet Transform into Convolutional Neural Network Structures.

Sensors (Basel) 2020 Sep 2;20(17). Epub 2020 Sep 2.

School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.

Accidental failures of rotating machinery components such as rolling bearings may trigger the sudden breakdown of the whole manufacturing system, thus, fault diagnosis is vital in industry to avoid these massive economical costs and casualties. Since convolutional neural networks (CNN) are poor in extracting reliable features from original signal data, the time-frequency analysis method is usually called for to transform 1D signal into a 2D time-frequency coefficient matrix in which richer information could be exposed more easily. However, realistic fault diagnosis applications face a dilemma in that signal time-frequency analysis and fault classification cannot be implemented together, which means manual signal conversion work is also needed, which reduces the integrity and robustness of the fault diagnosis method. In this paper, a novel network named WPT-CNN is proposed for end-to-end intelligent fault diagnosis of rolling bearings. WPT-CNN creatively uses the standard deep neural network structure to realize the wavelet packet transform (WPT) time-frequency analysis function, which seamlessly integrates fault diagnosis domain knowledge into deep learning algorithms. The overall network architecture can be trained with gradient descent backpropagation algorithms, indicating that the time-frequency analysis module of WPT-CNN is also able to learn the dataset characteristics, adaptively representing signal information in the most suitable way. Two experimental rolling bearing fault datasets were used to validate the proposed method. Testing results showed that WPT-CNN obtained the testing accuracies of 99.73% and 99.89%, respectively, in two datasets, which exhibited a better and more reliable diagnosis performance than any other existing deep learning and machine learning methods.
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http://dx.doi.org/10.3390/s20174965DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7506762PMC
September 2020

Patterning Ag nanoparticles by selective wetting for fine size Cu-Ag-Cu bonding.

Nanotechnology 2020 Aug 18;31(35):355302. Epub 2020 May 18.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, People's Republic of China.

Metal nanoparticles (NPs) are promising bonding materials to replace Sn alloys in fine size Cu-Cu bonding. However, the method of rapidly patterning NPs on solder joints with sizes less than 30 µm is one of the main barriers that impede the practical applications of NPs in Cu-Cu bonding, especially in mass production. In this paper, a novel method of patterning Ag NPs on Cu pads by selective wetting was introduced. Cu pads with diameters down to 5 µm were coated with Ag NPs successfully. When sizes of Cu pads were larger than 10 μm, high density could be achieved and the ratio of diameters to pitches of Cu pads could reach 2/3. Furthermore, the thickness and the coverage of the Ag NPs layer could be raised by repeating coating. In the bonding test, the shear strength increased significantly with the increase of the bonding temperature and the bonding time. It could reach 22.92 MPa after sintering for 5 min at 250 °C under a bonding pressure of 20 MPa in N. With the aforementioned advantages, patterning NPs by selective wetting will be one of the potential methods for applying NPs to Cu pads in Cu-NPs-Cu bonding.
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http://dx.doi.org/10.1088/1361-6528/ab93f0DOI Listing
August 2020

Controllable Synthesis of All Inorganic Lead Halide Perovskite Nanocrystals with Various Appearances in Multiligand Reaction System.

Nanomaterials (Basel) 2019 Dec 9;9(12). Epub 2019 Dec 9.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology (HUST), Wuhan 430074, China.

All inorganic cesium lead halide (CsPbX, X = Cl, Br, I) perovskite nanocrystals (PNCs) exhibit promising applications in light-emitting devices due to their excellent photophysical properties. Herein, we developed a low-cost and convenient method for the preparation of CsPbX PNCs in a multiligand-assisted reaction system where peanut oil is applied as a ligand source. The mixed-halide PNCs with tunable optical-band gap were prepared by mixing the single-halide perovskite solutions at room temperature. The resulting PNCs had good monodispersity, with dimensions of 8-10 nm, high photoluminescence quantum yield (96.9%), narrow emission widths (15-34 nm), and tunable emission wavelength (408-694 nm), covering the entire visible spectrum. Additionally, various morphologies of PNCs, such as nanospheres, nanocubes, and nanowires, were obtained by controlling reaction temperature and time, and the amount of oleamine with multiple ligands in peanut oil potentially playing a dominant role in the nucleation/growth processes of our PNCs. Finally, the resulting CsPbBr PNCs were employed to develop a white light-emitting diode (WLED), demonstrating the potential lighting applications for our method.
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http://dx.doi.org/10.3390/nano9121751DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6955694PMC
December 2019

Ultrafast Self-Assembly MoS/Cu(OH) Nanowires for Highly Sensitive Gamut Humidity Detection with an Enhanced Self-Recovery Ability.

ACS Appl Mater Interfaces 2019 Dec 22;11(49):46368-46378. Epub 2019 Nov 22.

Shenzhen Huazhong University of Science and Technology Research Institute , Shenzhen Virtual University Park , Shenzhen 518000 , PR China.

Humidity sensors have attracted intense interest in various fields because of the importance of humidity detection. Different methods have been adopted to enhance sensing performances of humidity sensors, while it is challenging for researchers to avoid the invalidation of the sensors after being wet. Here, we, for the first time, introduce self-assembly MoS/Cu(OH) nanowires fabricated by liquid self-spreading-coating-evaporating as sensing materials and present MoS/Cu(OH) nanowire-based quartz crystal microbalance gamut humidity sensors with superior sensitivity and self-recovery ability. The sensors deliver a remarkable sensitivity (60.8 Hz/% RH) under a wide range (0-97% RH) with fast response (1.9 s)/recovery time (3.8 s) and upgrade self-recovery ability that can maintain their original performances even after being wet, frozen, and heated or immersed in water. The sensors are also employed to monitor water counting, dew alarming, and human breathing (within 4 s), further showing their ultrahigh sensitivity for water molecules. The underlying humidity-sensing mechanism is interpreted by density functional theory calculations and in-situ Fourier transform infrared spectra experiments adequately, revealing that the high sensing performances are attributed to abundant adsorption sites and physisorption of water molecules. Our work proposes a strategy for transferring materials to arbitrary nanostructures swiftly and demonstrates new perspectives for highly sensitive humidity detection as well as self-recovery ability.
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http://dx.doi.org/10.1021/acsami.9b17155DOI Listing
December 2019

In situ formation of metal-organic framework derived CuO polyhedrons on carbon cloth for highly sensitive non-enzymatic glucose sensing.

J Mater Chem B 2019 08;7(32):4990-4996

Berkeley Sensor & Actuator Center, University of California, Berkeley, California 94720, USA. and Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, USA.

Metal-organic frameworks (MOFs) are considered promising templates for the fabrication of nanostructured materials with high porosities and high surface areas, which are important parameters for enhanced performance in sensing applications. Here, a facile in situ synthetic strategy to construct MOF-derived porous CuO polyhedrons on carbon cloth (CC) is reported. Uniform Cu(OH)2 nanorods are first synthesized on carbon cloth, followed by the conversion of Cu(OH)2 nanorods into porous CuO polyhedrons via a copper-based MOF, Cu-BTC, as the intermediate species. When evaluated as a glucose sensing electrode, the as-fabricated CuO polyhedrons/CC composite exhibits a high sensitivity of 13 575 μA mM-1 cm-2 with a fast response time (t90) of 2.3 s and a low detection limit of 0.46 μM. This work exemplifies the rational fabrication of porous nanostructures on conductive substrates for enhanced performance in glucose detection.
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http://dx.doi.org/10.1039/c9tb01166hDOI Listing
August 2019

Three-dimensional MoS/Graphene Aerogel as Binder-free Electrode for Li-ion Battery.

Nanoscale Res Lett 2019 Mar 8;14(1):85. Epub 2019 Mar 8.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China.

Hybrid MoS/reduced graphene aerogels with rich micro-pore are fabricated through a hydrothermal method, followed by freeze-drying and annealing treatment. The porous structure could act as an electrode directly, free of binder and conductive agent, which promotes an improved electron transfer, and provides a 3D network for an enhanced ion transport, thus leading to an increased capacity and stable long cycle stability performance. Notably, the specific capacity of MoS/reduced graphene aerogel is 1041 mA h g at 100 mA g. Moreover, reversible capacities of 667 mA h g with 58.6% capacity retention are kept after 100 cycles. The outstanding performance is beneficial from the synergistic effect of the MoS nanostructure and graphene conductive network, as well as the binder-free design. These results provide a route to integrate transition-metal-dichalcogenides with graphene to fabricate composites with rich micro-pores and a three-dimensional network for energy storage devices.
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http://dx.doi.org/10.1186/s11671-019-2916-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6408559PMC
March 2019

Size Distribution Control of Copper Nanoparticles and Oxides: Effect of Wet-Chemical Redox Cycling.

Inorg Chem 2019 Feb 31;58(4):2533-2542. Epub 2019 Jan 31.

In this work, we studied the effect of liquid-phase redox cycling on the size of Cu nanoparticles and oxides. The mixed solution of sodium hydroxide and ammonium persulfate was applied as the oxidation system at room temperature, and ascorbic acid was used as reduction agent at 80 °C in the cycling process. It was found that pristine copper particles with average size of around 800 nm and wide distribution from 300 to 1300 nm could be turned into the resulting particles with the average size of around 162.3 nm with the distribution from 75 to 250 nm after 5 redox cycles. It was also observed that uniform copper oxide nanowires formed after 5 oxidation cycles could be easily reduced into fine copper nanoparticles. The critical tuning factors including the precursor size, morphology, defects, reaction time, and the way of adding oxidant were investigated. It was suggested that the synergetic driving effect of chemical reduction and nanostructure thermodynamic instability in solution accounted for the size reformation of the copper nanoparticles. This proposed method of size-shrinking could be developed as a general strategy for large-scale tuning the properties of copper nanoparticles for wide applications and extended to other metal particles as well.
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http://dx.doi.org/10.1021/acs.inorgchem.8b03125DOI Listing
February 2019

One-Step Mask-Based Diffraction Lithography for the Fabrication of 3D Suspended Structures.

Nanoscale Res Lett 2018 Dec 5;13(1):394. Epub 2018 Dec 5.

State Key Lab of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China.

We propose a novel one-step exposure method for fabricating three-dimensional (3D) suspended structures, utilizing the diffraction of mask patterns with small line width. An optical model of the exposure process is built, and the 3D light intensity distribution in the photoresist is calculated based on Fresnel-Kirchhoff diffraction formulation. Several 3D suspended photoresist structures have been achieved, such as beams, meshes, word patterns, and multilayer structures. After the pyrolysis of SU-8 structures, suspended and free-standing 3D carbon structures are further obtained, which show great potential in the application of transparent electrode, semitransparent solar cells, and energy storage devices.
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http://dx.doi.org/10.1186/s11671-018-2817-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6281547PMC
December 2018

Leaf Vein-Inspired Hierarchical Wedge-Shaped Tracks on Flexible Substrate for Enhanced Directional Water Collection.

ACS Appl Mater Interfaces 2018 Dec 30;10(51):44815-44824. Epub 2018 Nov 30.

State Key Lab of Digital Manufacturing Equipment and Technology , Huazhong University of Science and Technology , Wuhan 430074 , People's Republic of China.

Water collection has been extensively researched due to its potential for mitigating the water scarcity in arid and semiarid regions. Numerous structures mimicking the fog-harvesting strategy of organisms have been fabricated for improving water-collecting efficiency. In this contribution, we demonstrate four-level wedge-shaped tracks inspired by leaf vein for enhancing directional water collection. Superhydrophilic Cu(OH) nanowires are introduced and prepared on flexible hydrophobic polyethylene terephthalate (PET) substrates by alkali-assisted surface oxidation at room temperature. They provide abundant capillary paths for promoting droplet absorption and forming water film tracks. Then, the hierarchical wedge-shaped tracks enable the water to be transported to a certain accumulation region spontaneously owing to the continuous Young-Laplace pressure difference. As a result, the four-level wedge-shaped tracks on PET substrate achieve the highest water-collecting efficiency, increasing by nearly 1150 and 510% compared to the bare PET and Cu(OH) nanowires on PET, respectively. After being bent for 10 cycles at a radius of 10 mm, the samples can still preserve high efficiency, indicating that the synthetic structures possess outstanding durability. Our approach provides a novel strategy for water collection and paves ways for directional liquid transportation and microfluidic devices.
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http://dx.doi.org/10.1021/acsami.8b13012DOI Listing
December 2018

Microscopic Three-Dimensional Measurement Based on Telecentric Stereo and Speckle Projection Methods.

Sensors (Basel) 2018 Nov 11;18(11). Epub 2018 Nov 11.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.

Three-dimensional (3D) measurement of microstructures has become increasingly important, and many microscopic measurement methods have been developed. For the dimension in several millimeters together with the accuracy at sub-pixel or sub-micron level, there is almost no effective measurement method now. Here we present a method combining the microscopic stereo measurement with the digital speckle projection. A microscopy experimental setup mainly composed of two telecentric cameras and an industrial projection module is established and a telecentric binocular stereo reconstruction procedure is carried out. The measurement accuracy has firstly been verified by performing 3D measurements of grid arrays at different locations and cylinder arrays with different height differences. Then two Mitutoyo step masters have been used for further verification. The experimental results show that the proposed method can obtain 3D information of the microstructure with a sub-pixel and even sub-micron measuring accuracy in millimeter scale.
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http://dx.doi.org/10.3390/s18113882DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6263875PMC
November 2018

Efficient Carbon-Based CsPbBr Inorganic Perovskite Solar Cells by Using Cu-Phthalocyanine as Hole Transport Material.

Nanomicro Lett 2018 16;10(2):34. Epub 2018 Jan 16.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China.

Metal halide perovskite solar cells (PSCs) have attracted extensive research interest for next-generation solution-processed photovoltaic devices because of their high solar-to-electric power conversion efficiency (PCE) and low fabrication cost. Although the world's best PSC successfully achieves a considerable PCE of over 20% within a very limited timeframe after intensive efforts, the stability, high cost, and up-scaling of PSCs still remain issues. Recently, inorganic perovskite material, CsPbBr, is emerging as a promising photo-sensitizer with excellent durability and thermal stability, but the efficiency is still embarrassing. In this work, we intend to address these issues by exploiting CsPbBr as light absorber, accompanied by using Cu-phthalocyanine (CuPc) as hole transport material (HTM) and carbon as counter electrode. The optimal device acquires a decent PCE of 6.21%, over 60% higher than those of the HTM-free devices. The systematic characterization and analysis reveal a more effective charge transfer process and a suppressed charge recombination in PSCs after introducing CuPc as hole transfer layer. More importantly, our devices exhibit an outstanding durability and a promising thermal stability, making it rather meaningful in future fabrication and application of PSCs.
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http://dx.doi.org/10.1007/s40820-018-0187-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6199080PMC
January 2018

Fitting an Optical Fiber Background with a Weighted Savitzky-Golay Smoothing Filter for Raman Spectroscopy.

Appl Spectrosc 2018 Nov 15;72(11):1632-1644. Epub 2018 Aug 15.

1 12443 State Key Lab of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, China.

The Raman background arising from optical fiber materials poses a critical problem for fiber optic surface-enhanced Raman spectroscopy (SERS). A novel filter is developed to fit the optical fiber background from the measured SERS spectrum of the target sample. The general model of the filter is built by incorporating a weighted term of matching the similarity between the estimated background spectrum and the measured background spectrum into the classic Savitzky-Golay (SG) smoothing filter model. Through respectively selecting Euclidean cosine coefficient (ECos) and Pearson correlation coefficient (PCor) as the similarity index, two different models of the weighted SG smoothing filter are derived and named as SG-ECos and SG-PCor accordingly. Furthermore, the algorithm is presented, implemented, successfully applied to experimentally measured SERS spectra of rhodamine 6G and crystal violet, and validated with mathematically simulated Raman spectra. Experimental and simulation results show that the SG-ECos filter is effective, fast, flexible, and of certain anti-noise capability in background fitting. It is suggested that the proposed filter may be also applicable for other Raman spectra measurements to remove spectral contaminants originated from sampling substrates such as glass slides.
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http://dx.doi.org/10.1177/0003702818785884DOI Listing
November 2018

Multiband Envelope Spectra Extraction for Fault Diagnosis of Rolling Element Bearings.

Sensors (Basel) 2018 May 8;18(5). Epub 2018 May 8.

Department of Power Engineering, Naval University of Engineering, Wuhan 430033, China.

Bearing fault features are presented as repetitive transient impulses in vibration signals. Narrowband demodulation methods have been widely used to extract the repetitive transients in bearing fault diagnosis, for which the key factor is to accurately locate the optimal band. A multitude of criteria have been constructed to determine the optimal frequency band for demodulation. However, these criteria can only describe the strength of transient impulses, and cannot differentiate fault-related impulses and interference impulses that are cyclically generated in the signals. Additionally, these criteria are easily affected by the independent transitions and background noise in industrial locales. Therefore, the large values of the criteria may not appear in the optimal frequency band. To overcome these problems, a new method, referred to as multiband envelope spectra extraction (MESE), is proposed in this paper, which can extract all repetitive transient features in the signals. The novelty of MESE lies in the following aspects: (1) it can fuse envelope spectra at multiple narrow bands. The potential bands are selected based on Jarque-Bera statistics of narrowband envelope spectra; and (2) fast independent component analysis (fastICA) is introduced to extract the independent source spectra, which are fault- or interference-related. The multi-band strategy will preserve all impulse features and make the method more robust. Meanwhile, as a blind source separation technique, the fastICA can suppress some in-band noise and make the diagnosis more accurate. Several simulated and experimental signals are used to validate the efficiency of the proposed method. The results show that MESE is effective for enhanced fault diagnosis of rolling element bearings. Bearing faults can be detected even in a harsh environment.
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http://dx.doi.org/10.3390/s18051466DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5982408PMC
May 2018

Cost-Effective Fabrication of Inner-Porous Micro/Nano Carbon Structures.

J Nanosci Nanotechnol 2018 Mar;18(3):2089-2095

School of Mechanical and Electronic Engineering, Nanjing Forestry University, Nanjing 210037, China.

This paper reports the fabrication of a new micro/nano carbon architecture array which owns the characteristics of inner-porous, desired conductivity and large effective surface area. The micro/nano inner-porous carbon structures were fabricated for the first time, with ordinary and cost-effective processes, including photolithography, oxygen plasma etching and pyrolysis. Firstly, micro/nano hierarchical photoresist structures array was generated through photolithography and oxygen plasma etching processes. By introducing a critical thin-film spin-coating step, and followed with carefully pyrolyzing process, the micro/nano photoresist structures were converted into innerporous carbon architectures with good electric connection which connected the carbon structures array together. Probably the inner-porous property can be attributed to the shrinkage difference between positive thin film and negative photoresist structures during pyrolyzing process. It is demonstrated that the simple method is effective to fabricate inner-porous carbon structures with good electric connection and the carbon structures can be used as electrochemical electrodes directly and without the addition of other pyrolysis or film coating processes. The electrochemical property of the carbon structures has been explored by cyclic voltammetric measurement. Compared with solid carbon microstructures array, the cyclic voltammetry curve of inner-porous carbon structures shows greatly enhanced current and improved charge-storage capability, indicating great potential in micro energy storage devices and bio-devices.
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http://dx.doi.org/10.1166/jnn.2018.14256DOI Listing
March 2018

Construction of porous CuCoS nanorod arrays via anion exchange for high-performance asymmetric supercapacitor.

Sci Rep 2017 07 27;7(1):6681. Epub 2017 Jul 27.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, China.

To push the energy density limit of supercapacitors, proper pseudocapacitive materials with favorable nanostructures are urgently pursued. Ternary transition metal sulfides are promising electrode materials due to the better conductivity and higher electrochemical activity in comparison to the single element sulfides and transition metal oxides. In this work, we have successfully synthesized porous CuCoS nanorod array (NRAs) on carbon textile through a stepwise hydrothermal method, including the growth of the Cu-Co precursor nanowire arrays and subsequent conversion into CuCoS NRAs via anion exchange reaction. The CuCoS NRAs electrode exhibits a greatly enhanced specific capacitance and an outstanding cycling stability. Moreover, an asymmetric supercapacitor using the CuCoS NRAs as positive electrode and activated carbon as negative electrode delivers a high energy density of 56.96 W h kg. Such superior performance demonstrate that the CuCoS NRAs are promising materials for future energy storage applications.
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http://dx.doi.org/10.1038/s41598-017-07102-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5532217PMC
July 2017

Novel Integration of Perovskite Solar Cell and Supercapacitor Based on Carbon Electrode for Hybridizing Energy Conversion and Storage.

ACS Appl Mater Interfaces 2017 Jul 27;9(27):22361-22368. Epub 2017 Jun 27.

State Key Laboratory of Digital Manufacturing Equipment and Technology and ‡Flexible Electronics Research Center, Huazhong University of Science and Technology (HUST) , Wuhan 430074, China.

Power packs integrating both photovoltaic parts and energy storage parts have gained great scientific and technological attention due to the increasing demand for green energy and the tendency for miniaturization and multifunctionalization in electronics industry. In this study, we demonstrate novel integration of perovskite solar cell and solid-state supercapacitor for power packs. The perovskite solar cell is integrated with the supercapacitor based on common carbon electrodes to hybridize photoelectric conversion and energy storage. The power pack achieves a voltage of 0.84 V when the supercapacitor is charged by the perovskite solar cell under the AM 1.5G white light illumination with a 0.071 cm active area, reaching an energy storage proportion of 76% and an overall conversion efficiency of 5.26%. When the supercapacitor is precharged at 1.0 V, an instant overall output efficiency of 22.9% can be achieved if the perovskite solar cell and supercapacitor are connected in series, exhibiting great potential in the applications of solar energy storage and flexible electronics such as portable and wearable devices.
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http://dx.doi.org/10.1021/acsami.7b01471DOI Listing
July 2017

Using Wavelet Packet Transform for Surface Roughness Evaluation and Texture Extraction.

Sensors (Basel) 2017 Apr 23;17(4). Epub 2017 Apr 23.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430000, China.

Surface characterization plays a significant role in evaluating surface functional performance. In this paper, we introduce wavelet packet transform for surface roughness characterization and surface texture extraction. Surface topography is acquired by a confocal laser scanning microscope. Smooth border padding and de-noise process are implemented to generate a roughness surface precisely. By analyzing the high frequency components of a simulated profile, surface textures are separated by using wavelet packet transform, and the reconstructed roughness and waviness coincide well with the original ones. Wavelet packet transform is then used as a smooth filter for texture extraction. A roughness specimen and three real engineering surfaces are also analyzed in detail. Profile and areal roughness parameters are calculated to quantify the characterization results and compared with those measured by a profile meter. Most obtained roughness parameters agree well with the measurement results, and the largest deviation occurs in the skewness. The relations between the roughness parameters and noise are analyzed by simulation for explaining the relatively large deviations. The extracted textures reflect the surface structure and indicate the manufacturing conditions well, which is helpful for further feature recognition and matching. By using wavelet packet transform, engineering surfaces are comprehensively characterized including evaluating surface roughness and extracting surface texture.
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http://dx.doi.org/10.3390/s17040933DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5426929PMC
April 2017

Extracting Optical Fiber Background from Surface-Enhanced Raman Spectroscopy Spectra Based on Bi-Objective Optimization Modeling.

Appl Spectrosc 2017 Aug 24;71(8):1808-1815. Epub 2017 Apr 24.

State Key Lab of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, China.

We propose a bi-objective optimization model for extracting optical fiber background from the measured surface-enhanced Raman spectroscopy (SERS) spectrum of the target sample in the application of fiber optic SERS. The model is built using curve fitting to resolve the SERS spectrum into several individual bands, and simultaneously matching some resolved bands with the measured background spectrum. The Pearson correlation coefficient is selected as the similarity index and its maximum value is pursued during the spectral matching process. An algorithm is proposed, programmed, and demonstrated successfully in extracting optical fiber background or fluorescence background from the measured SERS spectra of rhodamine 6G (R6G) and crystal violet (CV). The proposed model not only can be applied to remove optical fiber background or fluorescence background for SERS spectra, but also can be transferred to conventional Raman spectra recorded using fiber optic instrumentation.
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http://dx.doi.org/10.1177/0003702817696088DOI Listing
August 2017

Low-Temperature and Low-Pressure Cu-Cu Bonding by Highly Sinterable Cu Nanoparticle Paste.

Nanoscale Res Lett 2017 Dec 5;12(1):255. Epub 2017 Apr 5.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, People's Republic of China.

A reliable Cu-Cu bonding joint was achieved by using the highly sinterable Cu nanoparticle paste. Pure copper nanoparticles used in the preparation of nanoparticle paste were synthesized through simple routes, with an average size of 60.5 nm. Under an Ar-H gas mixture atmosphere, the Cu nanoparticle paste exhibited large areas of fusion after sintering at 300 °C and reached a low electrical resistivity of 11.2 μΩ cm. With the same temperature as sintering, a compact Cu-Cu bonding joint was achieved under the pressure of 1.08 MPa and the shear strength of the joint could achieve 31.88 MPa. The shear strength and the elemental composition of the bonded joint were almost unchanged after aging test, which proves that the Cu-Cu bonding with this process has excellent thermal stability.
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http://dx.doi.org/10.1186/s11671-017-2037-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5382117PMC
December 2017

Weighted Kernel Entropy Component Analysis for Fault Diagnosis of Rolling Bearings.

Sensors (Basel) 2017 Mar 18;17(3). Epub 2017 Mar 18.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.

This paper presents a supervised feature extraction method called weighted kernel entropy component analysis (WKECA) for fault diagnosis of rolling bearings. The method is developed based on kernel entropy component analysis (KECA) which attempts to preserve the Renyi entropy of the data set after dimension reduction. It makes full use of the labeled information and introduces a weight strategy in the feature extraction. The class-related weights are introduced to denote differences among the samples from different patterns, and genetic algorithm (GA) is implemented to seek out appropriate weights for optimizing the classification results. The features based on wavelet packet decomposition are derived from the original signals. Then the intrinsic geometric features extracted by WKECA are fed into the support vector machine (SVM) classifier to recognize different operating conditions of bearings, and we obtain the overall accuracy (97%) for the experimental samples. The experimental results demonstrated the feasibility and effectiveness of the proposed method.
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http://dx.doi.org/10.3390/s17030625DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5375911PMC
March 2017

Enhanced cycling stability of [email protected] core-shell nanowire arrays for all-solid-state asymmetric supercapacitors.

Sci Rep 2016 12 7;6:38620. Epub 2016 Dec 7.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.

As a new class of pseudocapacitive material, metal sulfides possess high electrochemical performance. However, their cycling performance as conventional electrodes is rather poor for practical applications. In this article, we report an original composite electrode based on [email protected] core-shell nanowire arrays (NWAs) with enhanced cycling stability. This three-dimensional electrode also has a high specific capacitance of 12.2 F cm at the current density of 1 mA cm and excellent cycling stability (about 89% retention after 10,000 cycles). Moreover, an all-solid-state asymmetric supercapacitor (ASC) device has been assembled with [email protected] NWAs as the positive electrode and active carbon (AC) as the negative electrode, delivering a high energy density of 30.38 W h kg at 0.288 KW kg and good cycling stability (about 109% retention after 5000 cycles). The results show that [email protected] NWAs are promising for high-performance supercapacitors with stable cycling based on the unique core-shell structure and well-designed combinations.
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http://dx.doi.org/10.1038/srep38620DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5141571PMC
December 2016

Nanowire-Assembled Hierarchical ZnCoO Microstructure Integrated with a Low-Power Microheater for Highly Sensitive Formaldehyde Detection.

ACS Appl Mater Interfaces 2016 Nov 14;8(46):31764-31771. Epub 2016 Nov 14.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology , Wuhan 430074, China.

Nanowire-assembled 3D hierarchical ZnCoO microstructure is synthesized by a facile hydrothermal route and a subsequent annealing process. In comparison to simple nanowires, the resulting dandelion-like structure yields more open spaces between nanowires, which allow for better gas diffusion and provide more active sites for gas adsorption while maintaining good electrical conductivity. The hierarchical ZnCoO microstructure is integrated on a low-power microheater platform without using binders or conductive additives. The hierarchical structure of the ZnCoO sensing material provides reliable electrical connection across the sensing electrodes. The resulting sensor exhibits an ultralow detection limit of 3 ppb toward formaldehyde with fast response and recovery as well as good selectivity to CO, H, and hydrocarbons such as n-pentane, propane, and CH. The sensor only consumes ∼5.7 mW for continuous operation at 300 °C with good long-term stability. The excellent sensing performance of this hierarchical structure based sensor suggests the advantages of combining such structures with microfabricated heaters for practical low-power sensing applications.
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http://dx.doi.org/10.1021/acsami.6b11054DOI Listing
November 2016

Sparse Reconstruction for Micro Defect Detection in Acoustic Micro Imaging.

Sensors (Basel) 2016 Oct 24;16(10). Epub 2016 Oct 24.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.

Acoustic micro imaging has been proven to be sufficiently sensitive for micro defect detection. In this study, we propose a sparse reconstruction method for acoustic micro imaging. A finite element model with a micro defect is developed to emulate the physical scanning. Then we obtain the point spread function, a blur kernel for sparse reconstruction. We reconstruct deblurred images from the oversampled C-scan images based on ₁-norm regularization, which can enhance the signal-to-noise ratio and improve the accuracy of micro defect detection. The method is further verified by experimental data. The results demonstrate that the sparse reconstruction is effective for micro defect detection in acoustic micro imaging.
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http://dx.doi.org/10.3390/s16101773DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5087557PMC
October 2016

Titanium Dioxide Nanorods with Hydrogenated Oxygen Vacancies for Enhanced Solar Water Splitting.

J Nanosci Nanotechnol 2016 Jun;16(6):6148-54

We demonstrate that moderate hydrogen annealing is a simple and effective approach to substantially improve the photocatalytic activity of TiO2 nanorods via increasing oxygen vacancies in outer layer. Hydrogenated TiO2 nanorods are obtained by annealing in hydrogen atmosphere at various temperatures ranging from 200 degrees C to 350 degrees C. TEM images directly illustrate the disordered layer on the surface of nanorods induced by hydrogen annealing. The photoelectrochemical measurements reveal that the photocurrent is improved first as the temperature increases and reaches to the maximum value at an appropriate temperature (250 degrees C), corresponding to about 50% enhancement compared to the pristine TiO2. Incident photon-to-electron conversion efficiency spectra reveal that the photocurrent improvement is mainly attributed to the enhanced photocatalytic activity of TiO2 in ultraviolet region. Mott-Schottky plots further betray that hydrogen annealing can significantly enhance the electric conductivity, via increasing the oxygen vacancies density in the outer layer. In addition, time-dependent measurements indicate the hydrogenated TiO2 nanorods possess excellent chemical stability. Thus, we believe the hydrogenated TiO2 nanorods would be a promising candidate for photoanode in solar water splitting.
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http://dx.doi.org/10.1166/jnn.2016.11036DOI Listing
June 2016

Using a low-temperature carbon electrode for preparing hole-conductor-free perovskite heterojunction solar cells under high relative humidity.

Nanoscale 2016 Apr;8(13):7017-23

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China and Flexible Electronics Research Center, Huazhong University of Science and Technology, Wuhan 430074, China.

We demonstrate the application of a low-temperature carbon counter electrode with good flexibility and high conductivity in fabricating perovskite solar cells. A modified two-step method was used for the deposition of nanocrystalline CH3NH3PbI3 under high relative humidity. The carbon counter electrode was printed on a perovskite layer directly, with different sizes of graphite powder being employed. The interfacial charge transfer and transport in solar cells were investigated through photoluminescence and impedance measurements. We find that the existence of nano-graphite powder in the electrode has a noticeable influence on the back contact and cell performance. The prepared devices of hole-conductor-free perovskite heterojunction solar cells without encapsulation exhibit advantageous stability in air in the dark, with the optimal power conversion efficiency reaching 6.88%. This carbon counter electrode has the features of low-cost and low-temperature preparation, giving it potential for application in the large-scale flexible fabrication of perovskite solar cells in the future.
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http://dx.doi.org/10.1039/c5nr07091kDOI Listing
April 2016

In-line mixing states monitoring of suspensions using ultrasonic reflection technique.

Ultrasonics 2016 Feb 2;65:43-50. Epub 2015 Nov 2.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China. Electronic address:

Based on the measurement of echo signal changes caused by different concentration distributions in the mixing process, a simple ultrasonic reflection technique is proposed for in-line monitoring of the mixing states of suspensions in an agitated tank in this study. The relation between the echo signals and the concentration of suspensions is studied, and the mixing process of suspensions is tracked by in-line measurement of ultrasonic echo signals using two ultrasonic sensors. Through the analysis of echo signals over time, the mixing states of suspensions are obtained, and the homogeneity of suspensions is quantified. With the proposed technique, the effects of impeller diameter and agitation speed on the mixing process are studied, and the optimal agitation speed and the minimum mixing time to achieve the maximum homogeneity are acquired under different operating conditions and design parameters. The proposed technique is stable and feasible and shows great potential for in-line monitoring of mixing states of suspensions.
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http://dx.doi.org/10.1016/j.ultras.2015.10.024DOI Listing
February 2016

Inline Measurement of Particle Concentrations in Multicomponent Suspensions using Ultrasonic Sensor and Least Squares Support Vector Machines.

Sensors (Basel) 2015 Sep 18;15(9):24109-24. Epub 2015 Sep 18.

State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.

This paper proposes an ultrasonic measurement system based on least squares support vector machines (LS-SVM) for inline measurement of particle concentrations in multicomponent suspensions. Firstly, the ultrasonic signals are analyzed and processed, and the optimal feature subset that contributes to the best model performance is selected based on the importance of features. Secondly, the LS-SVM model is tuned, trained and tested with different feature subsets to obtain the optimal model. In addition, a comparison is made between the partial least square (PLS) model and the LS-SVM model. Finally, the optimal LS-SVM model with the optimal feature subset is applied to inline measurement of particle concentrations in the mixing process. The results show that the proposed method is reliable and accurate for inline measuring the particle concentrations in multicomponent suspensions and the measurement accuracy is sufficiently high for industrial application. Furthermore, the proposed method is applicable to the modeling of the nonlinear system dynamically and provides a feasible way to monitor industrial processes.
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http://dx.doi.org/10.3390/s150924109DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4610515PMC
September 2015
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