In the present work, composites of poly (methyl methacrylate)/titanium oxide nanoparticles (100/0, 97.5/2.5, 95/5, 92.5/7.5, 90/10 and 0/100 wt/wt%)were prepared to be used as bioequivalent materials according to thei...In the present work, composites of poly (methyl methacrylate)/titanium oxide nanoparticles (100/0, 97.5/2.5, 95/5, 92.5/7.5, 90/10 and 0/100 wt/wt%)were prepared to be used as bioequivalent materials according to their importance broad practical and medical applications. Thermal properties as well as X-ray diffraction analyses were employed to characterize the structure properties of such composite. The obtained results showed variations in the glass transition temperature (Tg), the melting temperature (Tm), shape and area of thermal peaks which were attributed to the different degrees of crystallinity and the existence of interactions between PMMA and TiO2 nanoparticle molecules. The XRD patterns showed sharpening of peaks at different concentrations of nano-TiO2 powder with PMMA. This indicated changes in the crystallinity/amorphosity ratio, and also suggested that the miscibility between the amorphous components of homo- polymers PMMA and nano-TiO2 powder is possible.The results showed that nano-TiO2 powder mix with PMMA can improve the thermal stability of the homo-polymer under investigation, lead- ing to interesting technological applications.展开更多
The hydrogenation/dehydrogenation kinetics and thermodynamic behaviors of the MgH2- WS2 composites were investigated. The TPD （Temperature-Programmed-Desorption） curves showed that the onset dehydrogenation temperat...The hydrogenation/dehydrogenation kinetics and thermodynamic behaviors of the MgH2- WS2 composites were investigated. The TPD （Temperature-Programmed-Desorption） curves showed that the onset dehydrogenation temperature of the MgH2 ＋ 20wt% WS2 composite was 615 K, 58 K lower than that of the pristine MgH2. The kinetic measurements showed that within 21 rain, the MgH2 ＋ 20wt% WS2 composite could absorb 2.818wt% at 423 K, and release 4.244 wt% of hydrogen at 623 K, while the hydriding/ dehydriding capacity of MgH2 reached only 0.979wt% and 2.319wt% respectively under identical conditions. The improvement of hydrogenation/dehydrogenation performances for the composite was attributed to the co- catalytic effect between the new phases W and MgS which formed durin~ the ball-milliw, ~rocess.展开更多
A Fe modified Na2WO4 compound was synthesized by a solution impregnation method and was ball-milled with MgH2 to constitute a novel MgH2-Fe2O3/Na2WO4 composite. The effects of the Fe2O3/Na2WO4 additive on the hydrogen...A Fe modified Na2WO4 compound was synthesized by a solution impregnation method and was ball-milled with MgH2 to constitute a novel MgH2-Fe2O3/Na2WO4 composite. The effects of the Fe2O3/Na2WO4 additive on the hydrogen storage properties of MgH2 together with the corresponding mechanism were investigated. At 423 K, within the first 200 seconds, the hydrogen absorption amount of MgH2+20 wt% Fe2O3/Na2WO4 was almost 5 times that of pure MgH2. And at 573 K, its total hydrogen desorption amount was 7 times that for pure MgH2. Meanwhile, its onset dehydrogenation temperature was 110 K lower than that of pure MgH2. It was worth noting that the MgH2+20 wt% Fe/Na2WO4 presented the lower dehydrogenation reaction activation energy(Ea) of 35.9 kJ·mol^-1 compared to that of pure MgH2. The active MgWO4, Mg2 FeH6 and MgO formed during the milling process were responsible for the improvement of the hydrogen storage properties for MgH2.展开更多
Ti_(3)C_(2)T_(x) nanosheets have attracted significant attention for their potential in electromagnetic wave absorption(EWA).However,their inherent self-stacking and exorbitant electrical conductivity inevitably lead ...Ti_(3)C_(2)T_(x) nanosheets have attracted significant attention for their potential in electromagnetic wave absorption(EWA).However,their inherent self-stacking and exorbitant electrical conductivity inevitably lead to serious impedance mismatch,restricting their EWA application.Therefore,the optimization of impedance matching becomes crucial.In this work,we developed polymethyl methacrylate(PMMA)@Ti_(3)C_(2)T_(x)@SiO_(2) composites with a sandwich-like core–shell structure by coating SiO_(2) on PMMA@Ti_(3)C_(2)T_(x).The results demonstrate that the superiority of the SiO_(2) layer in combination with PMMA@Ti_(3)C_(2)T_(x),outperforming other relative graded distribution structures and meeting the requirements of EWA equipment.The resulting PMMA@Ti_(3)C_(2)T_(x)@SiO_(2) composites achieved a minimum reflection loss of-58.08 dB with a thickness of 1.9 mm,and an effective absorption bandwidth of 2.88 GHz.Mechanism analysis revealed that the structural design of SiO_(2) layer not only optimized impedance matching,but also synergistically enhanced multiple loss mechanisms such as interfacial polarization and dipolar polarization.Therefore,this work provides valuable insights for the future preparation of high-performance electromagnetic wave absorbing Ti_(3)C_(2)T_(x)-based composites.展开更多
For all-solid-state lithium batteries(ASSLBs),polymer-blended solid composite electrolytes(SCEs)have drawn wide interest owing to their significance in improving the interfacial solid-solid contacts and inhibiting the...For all-solid-state lithium batteries(ASSLBs),polymer-blended solid composite electrolytes(SCEs)have drawn wide interest owing to their significance in improving the interfacial solid-solid contacts and inhibiting the growth of lithium dendrites.In this work,SCEs based on PVDF-HFP/PMMA matrix containing MOFs(NH2-MIL-53(Al))and LiTFSI were designed and synthesized employing an easy solution casting method.The synthesized samples were examined by XRD,SEM,EDS,and electrochemical tests.It was found that MPP-2 SCE not only has excellent ionic conductivity at 60℃ of 5.54×10^(−4) S cm^(−1),but also exhibits superior interfacial compatibility in Li||Li symmetric batteries,which can constantly cycle for about 800 h at 0.1 mA cm^(−2) with no short-circuiting.The assembled Li|MPP-2|LiFePO4 cell exhibited a first discharge specific capacity of up to 157.1 mAh g^(−1) at 60℃ and 0.2 C.This work may help to further advance the progress of ASSLBs in the future.展开更多
PMMA matrices were doped with nano-crystalline neodymium oxides synthesized by thermal decomposition process. X-ray diffraction and high-resolution transmission electron microscopy measurements were carried out to inv...PMMA matrices were doped with nano-crystalline neodymium oxides synthesized by thermal decomposition process. X-ray diffraction and high-resolution transmission electron microscopy measurements were carried out to investigate the structure, phase, and the morphology of the Nd_2O_3 nanocrystals and those embedded in the PMMA matrix. The average grain sizes were estimated 35 ± 6 nm and 46 ± 4 nm for non-annealed and annealed Nd_2O_3 particles, respectively. The grain size distributions（GSD） were calculated from the diffraction peaks of the annealed and non-annealed Nd_2O_3 powders and doped PMMA samples. The mass density, refractive index. UV-Visible absorption spectra were measured and the data were analyzed using the Judd-Ofelt approach to determine the oscillator strengths, the spontaneous emission probabilities and the branching ratios as a function of the nano-crystalline Nd_2O_3 content in the range of 0.1 wt.%-20 wt.% of MMA. Luminescence spectra upon 808 nm diode laser excitation were carried out in the wavelength range of 850-1550 nm at room temperature. The photoluminescence study has shown that the reasonably sharp emission peaks were observed upon heat treatment at 800 ℃ for 24 h for all concentrations of Nd_2O_3 nanopowders in PMMA. The infrared laser transition of Nd^（3＋） ions at about 1.06 μm due to the ~4F_（3/2）→~4I_（11/2） transition was analyzed and discussed in Nd_2O_3 system for their possible applications in the photonic technology.展开更多
文摘In the present work, composites of poly (methyl methacrylate)/titanium oxide nanoparticles (100/0, 97.5/2.5, 95/5, 92.5/7.5, 90/10 and 0/100 wt/wt%)were prepared to be used as bioequivalent materials according to their importance broad practical and medical applications. Thermal properties as well as X-ray diffraction analyses were employed to characterize the structure properties of such composite. The obtained results showed variations in the glass transition temperature (Tg), the melting temperature (Tm), shape and area of thermal peaks which were attributed to the different degrees of crystallinity and the existence of interactions between PMMA and TiO2 nanoparticle molecules. The XRD patterns showed sharpening of peaks at different concentrations of nano-TiO2 powder with PMMA. This indicated changes in the crystallinity/amorphosity ratio, and also suggested that the miscibility between the amorphous components of homo- polymers PMMA and nano-TiO2 powder is possible.The results showed that nano-TiO2 powder mix with PMMA can improve the thermal stability of the homo-polymer under investigation, lead- ing to interesting technological applications.
基金Funded by the National Natural Science Foundation of China(Nos.50971112 and 51471065)the Scientific Research Projects in Colleges and Universities in Hebei Province,China(ZD2014004)
文摘The hydrogenation/dehydrogenation kinetics and thermodynamic behaviors of the MgH2- WS2 composites were investigated. The TPD （Temperature-Programmed-Desorption） curves showed that the onset dehydrogenation temperature of the MgH2 ＋ 20wt% WS2 composite was 615 K, 58 K lower than that of the pristine MgH2. The kinetic measurements showed that within 21 rain, the MgH2 ＋ 20wt% WS2 composite could absorb 2.818wt% at 423 K, and release 4.244 wt% of hydrogen at 623 K, while the hydriding/ dehydriding capacity of MgH2 reached only 0.979wt% and 2.319wt% respectively under identical conditions. The improvement of hydrogenation/dehydrogenation performances for the composite was attributed to the co- catalytic effect between the new phases W and MgS which formed durin~ the ball-milliw, ~rocess.
基金Funded by the National Natural Science Foundation of China(No.51771164)Scientific Research Projects in Colleges and Universities in Hebei Province,China(No.ZD2019307)+2 种基金the Fundamental Research Funds for the Central Universities(No.3142019013)the Natural Science Foundation of Hebei Province of China(No.E2019508214)the Program for Top-notch Young Talents in University of Hebei Province(No.BJ2016043)
文摘A Fe modified Na2WO4 compound was synthesized by a solution impregnation method and was ball-milled with MgH2 to constitute a novel MgH2-Fe2O3/Na2WO4 composite. The effects of the Fe2O3/Na2WO4 additive on the hydrogen storage properties of MgH2 together with the corresponding mechanism were investigated. At 423 K, within the first 200 seconds, the hydrogen absorption amount of MgH2+20 wt% Fe2O3/Na2WO4 was almost 5 times that of pure MgH2. And at 573 K, its total hydrogen desorption amount was 7 times that for pure MgH2. Meanwhile, its onset dehydrogenation temperature was 110 K lower than that of pure MgH2. It was worth noting that the MgH2+20 wt% Fe/Na2WO4 presented the lower dehydrogenation reaction activation energy(Ea) of 35.9 kJ·mol^-1 compared to that of pure MgH2. The active MgWO4, Mg2 FeH6 and MgO formed during the milling process were responsible for the improvement of the hydrogen storage properties for MgH2.
基金supported by the National Natural Science Foundation of China(No.U2004177)Henan Province Key Research Project for Higher Education Institutions(No.23B430017)+1 种基金the Outstanding Youth Fund of Henan Province(No.212300410081)the Science and Technology Innovation Talents in Universities of Henan Province(No.22HASTIT001).
文摘Ti_(3)C_(2)T_(x) nanosheets have attracted significant attention for their potential in electromagnetic wave absorption(EWA).However,their inherent self-stacking and exorbitant electrical conductivity inevitably lead to serious impedance mismatch,restricting their EWA application.Therefore,the optimization of impedance matching becomes crucial.In this work,we developed polymethyl methacrylate(PMMA)@Ti_(3)C_(2)T_(x)@SiO_(2) composites with a sandwich-like core–shell structure by coating SiO_(2) on PMMA@Ti_(3)C_(2)T_(x).The results demonstrate that the superiority of the SiO_(2) layer in combination with PMMA@Ti_(3)C_(2)T_(x),outperforming other relative graded distribution structures and meeting the requirements of EWA equipment.The resulting PMMA@Ti_(3)C_(2)T_(x)@SiO_(2) composites achieved a minimum reflection loss of-58.08 dB with a thickness of 1.9 mm,and an effective absorption bandwidth of 2.88 GHz.Mechanism analysis revealed that the structural design of SiO_(2) layer not only optimized impedance matching,but also synergistically enhanced multiple loss mechanisms such as interfacial polarization and dipolar polarization.Therefore,this work provides valuable insights for the future preparation of high-performance electromagnetic wave absorbing Ti_(3)C_(2)T_(x)-based composites.
基金supported by National Natural Science Foundation of China(grant Nos.21701083,22179054)The Ministry of Science and Technology of the People's Republic of China(grant No.G2023014022L)Jiangsu Provincial Key Research and Development Program(grant No.BZ2023010).
文摘For all-solid-state lithium batteries(ASSLBs),polymer-blended solid composite electrolytes(SCEs)have drawn wide interest owing to their significance in improving the interfacial solid-solid contacts and inhibiting the growth of lithium dendrites.In this work,SCEs based on PVDF-HFP/PMMA matrix containing MOFs(NH2-MIL-53(Al))and LiTFSI were designed and synthesized employing an easy solution casting method.The synthesized samples were examined by XRD,SEM,EDS,and electrochemical tests.It was found that MPP-2 SCE not only has excellent ionic conductivity at 60℃ of 5.54×10^(−4) S cm^(−1),but also exhibits superior interfacial compatibility in Li||Li symmetric batteries,which can constantly cycle for about 800 h at 0.1 mA cm^(−2) with no short-circuiting.The assembled Li|MPP-2|LiFePO4 cell exhibited a first discharge specific capacity of up to 157.1 mAh g^(−1) at 60℃ and 0.2 C.This work may help to further advance the progress of ASSLBs in the future.
基金Project supported by Istanbul Technical University Scientific Research Projects Department(ITU BAP,project number 39283)
文摘PMMA matrices were doped with nano-crystalline neodymium oxides synthesized by thermal decomposition process. X-ray diffraction and high-resolution transmission electron microscopy measurements were carried out to investigate the structure, phase, and the morphology of the Nd_2O_3 nanocrystals and those embedded in the PMMA matrix. The average grain sizes were estimated 35 ± 6 nm and 46 ± 4 nm for non-annealed and annealed Nd_2O_3 particles, respectively. The grain size distributions（GSD） were calculated from the diffraction peaks of the annealed and non-annealed Nd_2O_3 powders and doped PMMA samples. The mass density, refractive index. UV-Visible absorption spectra were measured and the data were analyzed using the Judd-Ofelt approach to determine the oscillator strengths, the spontaneous emission probabilities and the branching ratios as a function of the nano-crystalline Nd_2O_3 content in the range of 0.1 wt.%-20 wt.% of MMA. Luminescence spectra upon 808 nm diode laser excitation were carried out in the wavelength range of 850-1550 nm at room temperature. The photoluminescence study has shown that the reasonably sharp emission peaks were observed upon heat treatment at 800 ℃ for 24 h for all concentrations of Nd_2O_3 nanopowders in PMMA. The infrared laser transition of Nd^（3＋） ions at about 1.06 μm due to the ~4F_（3/2）→~4I_（11/2） transition was analyzed and discussed in Nd_2O_3 system for their possible applications in the photonic technology.
