A series of photoreactive polymers containing poly(N,N-dimethylacrylamide) and 2-hydroxy-(4-methacryloyloxybenzophenone), P(DMAA-n%MABP-OH), was explored to modify sheet-formed carbonated hydroxyapatite/gelatin (cHA/g...
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A series of photoreactive polymers containing poly(N,N-dimethylacrylamide) and 2-hydroxy-(4-methacryloyloxybenzophenone), P(DMAA-n%MABP-OH), was explored to modify sheet-formed carbonated hydroxyapatite/gelatin (cHA/gelatin) scaffold. Under UV-light illumination, the benzophenones react with any c-H bonds in their vicinity through a c,H-insertion mechanism, enabling PDMAA-based hydrogel formation that is covalently attached to the gelatin. NMR spectroscopy confirmed the chemical structure of P(DMAA-n%MABP-OH) polymers with aimed n = 1, 5, 10, while GPc determined their molecular masses. The benzophenone reactivity under UV-light illumination for 0-240 min. was demonstrated using UV-Vis spectroscopy at 240-400 nm. After immobilization of P(DMAA-n%MABP-OH) onto the cHA/gelatin scaffold, typical FTIR vibration bands of both compounds could be detected on the spectra of the modified scaffolds. SEM images showed that the scaffold is highly porous with approximately 100 mu m thickness. P(DMAA-n%MABP-OH) addition led to 2-3 times increase in thickness and 15-19% mass addition. Furthermore, it was shown that chemical (degradation and ca2+ release profile), physical (4-7 swelling index), mechanical (0.06-0.17 MPa wet tensile strength and 0.2-0.8 MPa elastic modulus), and biological (cell adhesion) properties of the scaffold could be tailored by varying the photocrosslinker content. cytotoxicity test showed that all studied cHA/gelatin-based scaffolds were nontoxic (>80% cell viability).
In this study, the deformation response and failure behavior of a plain-woven c/Siccomposite were investigated under on-axis and off-axis tensile loading. Digital image correlation (DIc) was utilized to characterize ...
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In this study, the deformation response and failure behavior of a plain-woven c/Siccomposite were investigated under on-axis and off-axis tensile loading. Digital image correlation (DIc) was utilized to characterize the full field deformation and mesoscale strain distribution. The test results indicate a strong influence of the woven architecture on the mechanical properties and strain distribution, and the materials exhibit failure modes dependent on the loading directions or off-axis angles: the fracture positions of different layers are the same under off-axial load, while for on-axil loading, the fracture positions of different layers do not affect each other. SEM results provide direct evidence that the width of the off-axis specimen has a great influence on the mechanical properties. The reduction of the modulus and strength of off-axis specimen, is not only due to the off axis loading, but also due to the reduction of effective bearing area or effective bearing fiber.
The cathode materials of scrapped lithium-iron phosphate battery are mainly composed of LiFePO4/c, conductive agent and PVDF, etc. Unreasonable disposal will cause serious environmental pollution and waste of scarce r...
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The cathode materials of scrapped lithium-iron phosphate battery are mainly composed of LiFePO4/c, conductive agent and PVDF, etc. Unreasonable disposal will cause serious environmental pollution and waste of scarce resources. In this paper, cathode materials were regenerated by pre-oxidation and reduction method. Impurities such as carbon coating, conductive agent, and PVDF were removed and LiFePO4/c was converted to Fe2O3 and Li3Fe2(PO4)(3) by pre-oxidation. After the addition of sucrose, regeneratedLiFePO(4)/c was synthesized under reduction process. The effects of calcination temperature and sucrose addition on the microstructure and electrochemical properties of regenerated LiFePO4/c were studied. The regenerated LiFePO4/c had excellent cycling stability when the sucrose addition was 12% and calcined at 700 celcius. The initial discharge specificcapacity of regenerated LiFePO4/c was 145.51 mAh g(-1) at 0.5 c. After 200 cycles, the discharge specificcapacity was 145.25 mAh g(-1) (capacity retention rate: 99.82%). It provides a new inspiration for the high-value recycling and regeneration of the other scrapped lithium-ion batteries.
In this study, Ti-Fe-Si composites were prepared by one step ball-milling method as anode materials for Li-ion batteries. The effects of ball-milling speed and time were studied by X-ray diffraction, electron microsco...
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In this study, Ti-Fe-Si composites were prepared by one step ball-milling method as anode materials for Li-ion batteries. The effects of ball-milling speed and time were studied by X-ray diffraction, electron microscopy, and Fe-57 Mossbauer spectroscopy. changes in the composition and microstructure of the composites were observed and related to the electrochemical performance. Increasing ball-milling speed led to the formation of FeSix alloys that reduced the specificcapacity while increasing the ball-milling time improved the particle size morphology and homogeneity. Discharge/charge profiles for the first two cycles were carried out at 0.05ccurrent rate (1c = 1260 mAh.g(-1)for Li3.75Si). The first discharge for Ti-Fe-Si showed a LixSi reaction plateau of 1100 mAh.g(-1), which were reversible and yielded columbic efficiency (cE) 77% and 90% in the first and second cycles, respectively. This capacity plateau indicated the insertion of about 3.25 Li into silicon. For the composite containing an additional 10% carbon SP, the theoretical capacity was about 1130 mAh.g(-1), the discharge curve showed that the first discharge plateau reaches 1030 mAh.g(-1) corresponding to 3.5 Li with the first cE was about 85%, and 98% for the second cycle. The addition of carbon to Ti-Fe-Si-c played a key role in capacity retention. The best results were obtained for the composite Fe/Ti/Si (1:1:2) with 10 wt% of carbon, ball-milled at 500 rpm for 48 hours. The specificcapacities were about 900 mAh.g(-1) at c/5 and 700 mAh.g(-1) at 1c (c = 1200 mAg(-1)) with a capacity retention of about 90% for 100 cycles.
In order to understand the role of fiber-matrix adhesion (FMA) at carbon fiber-reinforced polymer (cFRP) stage on the microstructure and mechanical properties of c/c-Siccomposite via liquid silicon infiltration (LSI)...
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In order to understand the role of fiber-matrix adhesion (FMA) at carbon fiber-reinforced polymer (cFRP) stage on the microstructure and mechanical properties of c/c-Siccomposite via liquid silicon infiltration (LSI) process, the FMA was adjusted by thermal treatment of carbon fibers at different temperatures and evaluated by means of single fiber push-out technique. The microstructure was characterized by optical microscopy and scanning electron microscopy. The mechanical properties were measured by the double-notched shear test, three-point flexural test, and single edge-notched beam test, respectively. Results indicated that the microstructure and mechanical properties of c/c-Siccomposite via LSI were closely associated with the FMA at cFRP stage. The microstructure of c/c-Siccomposite fabricated by using the cFRP with high FMA presented nonhomogeneous distribution and concentration of Sic matrix. In contrast, the c/c-Siccomposite fabricated by using the cFRP with low FMA, the high content of Sic distributed homogeneously and surrounded the fiber, which resulted in a strong bonded c-Sic interface. The strong c-Sic interface is detrimental to the fracture toughness, but it is beneficial to the improvement of oxidation resistance. To obtain desired mechanical properties of c/c-Siccomposite, the control of interface bonding is important, which can be realized by modifying the FMA at cFRP stage.
An active Ag-based filler metal, containing trace alloy elements of Al, cu and Ti, was successfully applied to braze c/ccomposite and Nb. The microstructure and formation mechanism of the c/ccomposite and Nb brazed ...
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An active Ag-based filler metal, containing trace alloy elements of Al, cu and Ti, was successfully applied to braze c/ccomposite and Nb. The microstructure and formation mechanism of the c/ccomposite and Nb brazed joint were investigated in this study. Moreover, the influence of brazing parameters on microstructural evolution and mechanical properties of brazed joints was evaluated. The typical interfacial microstructure of the joint obtained at 950 degrees c for 600 s was c/c/Tic + Alcu2Ti/Ag(s, s) + Alcu2Ti + particle cu/Alcu2Ti + AlcuTi + (Ti, Nb)3Al + Nb(Ti)/Nb. The dispersive Alcu2Ti phase was uniformly distributed in the Ag matrix, which was a beneficial structure for the brazed joint. The shear strength of the brazed joint was sensitive to the brazing temperature and holding time, which was closely related to the Tic layer bordering the c/ccomposite. The thickness of the Tic layer first increased as temperature increased to 950 degrees c, and then decreased when temperature reached 970 degrees c. The carbon fiber eroded by the filler at 970 degrees c entered to the brazing seam and reacted with Ti, resulting the reduction of the thickness of Tic, thus damaging the strength of the joint. With extension of holding time from 300 s to 1200 s, the interface reaction became more sufficient. Therefore, the thickness of the Tic layer increased. However, at 1200 s, the over-thick Tic broke the c/c substrate because of the mismatch of coefficient of thermal expansions. The maximum shear strength of the joint (950 degrees c/600 s) reached 55 MPa at room temperature and 35 MPa tested at 550 degrees c.
c/ccomposite is widely used in aerospace due to excellent high temperature mechanical properties. Improving its ablation resistance has become the focus of attention. Due to anisotropy of composite materials, the dif...
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c/ccomposite is widely used in aerospace due to excellent high temperature mechanical properties. Improving its ablation resistance has become the focus of attention. Due to anisotropy of composite materials, the difference of thermal conductivity and thermal expansion coefficient between fiber and matrix, surface morphologies affect ablation performance greatly. In particular, fiber exposed length (FEL) and crack had a significant impact on its ablation resistance. Therefore, this paper constructed a FEL theoretical model based on machining damage, and verified that the error of the modified model was within 12 % through experiments. Meanwhile, improvement effect of rotary ultrasonic machining (RUM) was clarified. It is found that RUM reduced FEL by 15%~38% in all fiber angles and decreased the crack pores on machined surface. Then, oxyacetylene ablation experiments on c/ccomposite surface under conventional machining (cM) and RUM were carried out. The results showed that RUM surface had better ablation resistance, and interface ablation and porosity decreased significantly.
Two-dimensional (2D) csPbI3 is developed to conquer the phase-stability problem of csPbI3 by introducing bulky organiccations to produce a steric hindrance effect. However, organiccations also inevitably increase th...
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Two-dimensional (2D) csPbI3 is developed to conquer the phase-stability problem of csPbI3 by introducing bulky organiccations to produce a steric hindrance effect. However, organiccations also inevitably increase the formation energy and difficulty in crystallization kinetics regulation. Such poor crystallization process modulation of 2D csPbI3 leads to disordered phase-arrangement, which impedes the transport of photo-generated carriers and worsens device performance. Herein, a type of c3N quantum dots (QDs) with ordered carbon and nitrogen atoms to manipulate the crystallization process of 2D csPbI3 for improving the crystallization pathway, phase-arrangement and morphology, is introduced. combination analyses of theoretical simulation, morphology regulation and femtosecond transient absorption (fs-TA) characterization, show that the c3N QDs induce the formation of electron-rich regions to adsorb bulky organiccations and provide nucleation sites to realize a bi-directional crystallization process. Meanwhile, the quality of 2D csPbI3 film is improved with lower trap density, higher surface potential, and compact morphology. As a result, the power conversion efficiency (PcE) of the optimized device (n = 5) boosts to an ultra-high value of 15.63% with strengthened environmental stability. Moreover, the simple c3N QDs insertion method shows good universality to other bulky organiccations of Ruddlesden-Popper and Dion-Jacobson, providing a good modulation strategy for other optoelectronic devices.
Application of waste biomass resources in heavy metal adsorption and new energy development is of great significance to improving environmental pollution and the adjustment of energy structure. For this purpose, we de...
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Application of waste biomass resources in heavy metal adsorption and new energy development is of great significance to improving environmental pollution and the adjustment of energy structure. For this purpose, we designed a simple method for preparing porous Mo2c/ccomposite materials based on resource-rich biomass carbon (derived from waste pine wood) and ammonium molybdate, and successfully applied it to the above field. The effects of holding time and sintering temperature on the phase compositions and morphological structures of samples were investigated, and the heavy adsorption capacity (cr(III)) and hydrogen evolution reaction of composite materials were also studied. The results showed that porous biomass Mo2c/ccomposite materials had significantly higher oxidation resistance, and more prominent pore structure as compared to the pretreated biomass carbon. In addition, porous biomass Mo2c/ccomposite materials showed excellent adsorption performance for heavy metal cr(III) and catalytic hydrogen evolution reaction performance, its adsorption capacity and Tafel slope were 43.2 mg/g and 123.9 mV/dec, respectively.
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