We present a first velocity map imaging study on the 234 nm photodissociation dynamics of two carbon-chain branched alkyl bromides, neopentyl bromide （denoted as NPB） and tert- pentyl bromide （denoted as TPB）. Unl...We present a first velocity map imaging study on the 234 nm photodissociation dynamics of two carbon-chain branched alkyl bromides, neopentyl bromide （denoted as NPB） and tert- pentyl bromide （denoted as TPB）. Unlike the 234 nm photodissociation of the unbranched n-C5H11Br molecule where only a direct fission of the C-Br bond is involved, the branched NPB and TPB molecules exhibit one and two more independent dissociation pathways with much energy being decayed via an extensive excitation of the bending modes of the parent molecules prior to the C-Br bond fission. This observation strongly suggests that the dissociation coordinate for the two carbon-chain branched molecules is no longer solely ascribed to the C-Br stretching mode but rather a combination of the bending-stretching modes.展开更多
A novel UV-curable prepolymer neopentyl glycol diglycidyl ether diacrylate (NPGGEA) was synthesized by using neopentyl glycol diglycidyl ether (NPGGE) and acrylic acid (AA) as starting materials, N, N-dimethylbenzylam...A novel UV-curable prepolymer neopentyl glycol diglycidyl ether diacrylate (NPGGEA) was synthesized by using neopentyl glycol diglycidyl ether (NPGGE) and acrylic acid (AA) as starting materials, N, N-dimethylbenzylamine as catalyst and p-hydroxyanisole as inhibitor. The optimum synthetic conditions were taken as follows: The concentration of N,N-dimethylbenzylamine, 0.80% of reactants; the concentration of p-hydroxyanisole, 0.3% of reactants; the reaction temperature, 90-110 ; the molar ratio of NPGGE to AA, 1:2.2. Meanwhile, 1-hydroxycyclohexyl phenyl ketone of a UV-cured initiator was added to the synthesized NPGGEA to prepare a kind of UV-cured coating. Mechanical properties of the UV-cured films were determined, giving 28.75 MPa of tensile strength, 923.82 MPa of Young’s modulus and 5.51% of elongation at tear.展开更多
Plastic crystal neopentyl glycol(NPG)exhibits colossal barocaloric effect with high entropy changes.However,their application is restricted in several aspects,such as low thermal conductivity,substantial supercooling ...Plastic crystal neopentyl glycol(NPG)exhibits colossal barocaloric effect with high entropy changes.However,their application is restricted in several aspects,such as low thermal conductivity,substantial supercooling effect,and poor springback properties.In this work,multi-walled carbon nanotubes(MWCNTs)with ultra-high thermal conductivity and high mechanical strength were selected for performance enhancement of NPG.The optimal mixing ratio was determined to be NPG with 3 wt%MWCNTs composites,which showed a 6K reduction in supercooling without affecting the phase change enthalpy.Subsequently,comprehensive performance of the composites with optimal mixing ratio was compared with pure NPG At 40 MPa,390J·K^(-1)·kg^(-1)change in entropy and 9.9 K change in temperature were observed.Furthermore,the minimum driving pressure required to achieve reversible barocaloric effect was reduced by 19.2%.In addition,the thermal conductivity of the composite was increased by approximately 28%,significantly reducing the heat exchange time during a barocaloric refrigeration cycle.More importantly,ultra-high pressure release rate resulted in a73.7%reduction in the springback time of the composites,offering new opportunities for the recovery of expansion work.展开更多
Barocaloric refrigeration is regarded as one of the next-generation alternative refrigeration technology due to its environmental friendliness.In recent years,many researchers have been devoted to finding materials wi...Barocaloric refrigeration is regarded as one of the next-generation alternative refrigeration technology due to its environmental friendliness.In recent years,many researchers have been devoted to finding materials with colossal barocaloric effects,while neglecting the research on barocaloric refrigeration devices and thermodynamic cycles.Neopentyl glycol is regarded as one of the potential refrigerants for barocaloric refrigeration due to its giant isothermal entropy changes and relatively low operating pressure.To evaluate the performance of the barocaloric system using Neopentyl glycol,for the first time,this study establishes a thermodynamic cycle based on the metastable temperature-entropy diagram.The performance of the proposed system is investigated from the aspects of irreversibility,operating temperature range,and operating pressure,and optimized with finite-rate heat transfer.The guidance for the optimal design of the system is given by revealing the effect of the irreversibility in two isobaric processes.The results show that a COP of 8.8 can be achieved at a temperature span of 10 K when the system fully uses the phase transition region of Neopentyl glycol,while a COP of 3 can be achieved at a temperature span of 10 K when the system operates at room temperature.Furthermore,this study also shows that the system performance can be further improved through the modification of Neopentyl glycol,and some future development guidance is provided.展开更多
基金This work was supported by the National Natural Science Foundation of China （No.20873133）, the Ministry of Science and Technology of China （No.2007CB815203 and No.2010CB923302）, the Chinese Academy of Sciences （No.KJCX2-YW-N24 and No.KJCX2-EW-W09）, the Fundamental Research Funds for the Central Universities of China （No.WK2340000012）, and the USTC-NSRL Joint Funds （No.KY2340000021）.
文摘We present a first velocity map imaging study on the 234 nm photodissociation dynamics of two carbon-chain branched alkyl bromides, neopentyl bromide （denoted as NPB） and tert- pentyl bromide （denoted as TPB）. Unlike the 234 nm photodissociation of the unbranched n-C5H11Br molecule where only a direct fission of the C-Br bond is involved, the branched NPB and TPB molecules exhibit one and two more independent dissociation pathways with much energy being decayed via an extensive excitation of the bending modes of the parent molecules prior to the C-Br bond fission. This observation strongly suggests that the dissociation coordinate for the two carbon-chain branched molecules is no longer solely ascribed to the C-Br stretching mode but rather a combination of the bending-stretching modes.
基金supported by the National High-Technology Research and Development Program of China (Grant No.2002AA6Z3083)
文摘A novel UV-curable prepolymer neopentyl glycol diglycidyl ether diacrylate (NPGGEA) was synthesized by using neopentyl glycol diglycidyl ether (NPGGE) and acrylic acid (AA) as starting materials, N, N-dimethylbenzylamine as catalyst and p-hydroxyanisole as inhibitor. The optimum synthetic conditions were taken as follows: The concentration of N,N-dimethylbenzylamine, 0.80% of reactants; the concentration of p-hydroxyanisole, 0.3% of reactants; the reaction temperature, 90-110 ; the molar ratio of NPGGE to AA, 1:2.2. Meanwhile, 1-hydroxycyclohexyl phenyl ketone of a UV-cured initiator was added to the synthesized NPGGEA to prepare a kind of UV-cured coating. Mechanical properties of the UV-cured films were determined, giving 28.75 MPa of tensile strength, 923.82 MPa of Young’s modulus and 5.51% of elongation at tear.
基金supported by the Basic Research Program of Frontier Leading Technologies in Jiangsu Province(BK20202008)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX23_0240)+3 种基金the key research and demonstration projects of future low-carbon emission buildings(No.BE2022606)Hebei Natural Science Foundation(No.E2022210022)Science and Technology Project of Hebei Education Department(No.BJK2022056)the Introduction Program of Oversea Talents of Hebei Province(No.C20220505)。
文摘Plastic crystal neopentyl glycol(NPG)exhibits colossal barocaloric effect with high entropy changes.However,their application is restricted in several aspects,such as low thermal conductivity,substantial supercooling effect,and poor springback properties.In this work,multi-walled carbon nanotubes(MWCNTs)with ultra-high thermal conductivity and high mechanical strength were selected for performance enhancement of NPG.The optimal mixing ratio was determined to be NPG with 3 wt%MWCNTs composites,which showed a 6K reduction in supercooling without affecting the phase change enthalpy.Subsequently,comprehensive performance of the composites with optimal mixing ratio was compared with pure NPG At 40 MPa,390J·K^(-1)·kg^(-1)change in entropy and 9.9 K change in temperature were observed.Furthermore,the minimum driving pressure required to achieve reversible barocaloric effect was reduced by 19.2%.In addition,the thermal conductivity of the composite was increased by approximately 28%,significantly reducing the heat exchange time during a barocaloric refrigeration cycle.More importantly,ultra-high pressure release rate resulted in a73.7%reduction in the springback time of the composites,offering new opportunities for the recovery of expansion work.
基金supported by the Basic Research Program of Frontier Leading Technologies in Jiangsu Province(BK20202008)Hebei Natural Science Foundation(No.E2022210022)+1 种基金Science and Technology Project of Hebei Education Department(No.BJK2022056)the Introduction Program of Oversea Talents of Hebei Province(No.C20220505)。
文摘Barocaloric refrigeration is regarded as one of the next-generation alternative refrigeration technology due to its environmental friendliness.In recent years,many researchers have been devoted to finding materials with colossal barocaloric effects,while neglecting the research on barocaloric refrigeration devices and thermodynamic cycles.Neopentyl glycol is regarded as one of the potential refrigerants for barocaloric refrigeration due to its giant isothermal entropy changes and relatively low operating pressure.To evaluate the performance of the barocaloric system using Neopentyl glycol,for the first time,this study establishes a thermodynamic cycle based on the metastable temperature-entropy diagram.The performance of the proposed system is investigated from the aspects of irreversibility,operating temperature range,and operating pressure,and optimized with finite-rate heat transfer.The guidance for the optimal design of the system is given by revealing the effect of the irreversibility in two isobaric processes.The results show that a COP of 8.8 can be achieved at a temperature span of 10 K when the system fully uses the phase transition region of Neopentyl glycol,while a COP of 3 can be achieved at a temperature span of 10 K when the system operates at room temperature.Furthermore,this study also shows that the system performance can be further improved through the modification of Neopentyl glycol,and some future development guidance is provided.
