For a climate-neutral future mobility,the socalled e-fuels can play an essential part.Especially,oxygenated e-fuels containing oxygen in their chemical formula have the additional potential to burn with significantly ...For a climate-neutral future mobility,the socalled e-fuels can play an essential part.Especially,oxygenated e-fuels containing oxygen in their chemical formula have the additional potential to burn with significantly lower soot levels.In particular,polyoxymethylene dimethyl ethers or oxymethylene ethers(PODEs or OMEs)do not contain carbon-carbon bonds,prohibiting the production of soot precursors like acetylene(C2H2).These properties make OMEs a highly interesting candidate for future climate-neutral compression-ignition engines.However,to fully leverage their potential,the auto-ignition process,flame propagation,and mixing regimes of the combustion need to be understood.To achieve this,efficient oxidation mechanisms suitable for computational fluid dynamics(CFD)calculations must be developed and validated.The present work aims to highlight the improvements made by developing an adapted oxidation mechanism for OME1-6 and introducing it into a validated spray combustion CFD model for OMEs.The simulations were conducted for single-and multi-injection patterns,changing ambient temperatures,and oxygen contents.The results were validated against high-pressure and high-temperature constantpressure chamber experiments.OH*-chemiluminescence measurements accomplished the characterization of the auto-ignition process.Both experiments and simulations were conducted for two different injectors.Significant improvements concerning the prediction of the ignition delay time were accomplished while also retaining an excellent agreement for the flame lift-off length.The spatial zones of high-temperature reaction activity were also affected by the adaption of the reaction kinetics.They showed a greater tendency to form OH*radicals within the center of the spray in accordance with the experiments.展开更多
含亚甲氧基桥键负性单体液晶由于具有较大的负介电各向异性,较低的旋转粘度、良好的相溶性而被广泛应用于VA-TFT配方中,但其合成步骤长,合成及提纯难度大。本文讨论了含亚甲氧基桥键及苯环侧向氟取代的负介电各向异性单体液晶的合成方法...含亚甲氧基桥键负性单体液晶由于具有较大的负介电各向异性,较低的旋转粘度、良好的相溶性而被广泛应用于VA-TFT配方中,但其合成步骤长,合成及提纯难度大。本文讨论了含亚甲氧基桥键及苯环侧向氟取代的负介电各向异性单体液晶的合成方法,该方法主要采用2,3-二氟-4-乙氧基苯酚与含不同长度烷基链的苯磺酸酯反应引入亚甲氧基桥键,避免了常用醚化方法中卤代物的使用和卤素离子对单体液晶性能的影响。使用1 H NMR对目标单体液晶的结构进行了表征;采用DSC、热台偏光显微镜、LCR测试仪等对目标单体液晶的相变温度、光学各向异性、介电各向异性等一系列液晶性能参数进行了测试。展开更多
用辐照的方法将反应性聚合物接枝到纳米 Ca CO3表面 ,研究接枝 Ca CO3对聚甲醛形态的影响 ,同时还就聚醚型聚氨酯 (TPU)及相容剂对聚甲醛复合材料的分散形态影响进行了讨论。研究结果表明 ,聚丙烯腈接技的 Ca CO3改善了与聚甲醛的界面...用辐照的方法将反应性聚合物接枝到纳米 Ca CO3表面 ,研究接枝 Ca CO3对聚甲醛形态的影响 ,同时还就聚醚型聚氨酯 (TPU)及相容剂对聚甲醛复合材料的分散形态影响进行了讨论。研究结果表明 ,聚丙烯腈接技的 Ca CO3改善了与聚甲醛的界面粘结状态 ,TPU的加入增强了 Ca展开更多
A series of polyvinylpyrrolidone-stabilized heteropolyacids(PVP-HPAs)are generated by self-assembly of HPAs and PVP in methanol.The PVP-HPAs are then employed as catalysts for the synthesis of poly(oxymethylene)dimeth...A series of polyvinylpyrrolidone-stabilized heteropolyacids(PVP-HPAs)are generated by self-assembly of HPAs and PVP in methanol.The PVP-HPAs are then employed as catalysts for the synthesis of poly(oxymethylene)dimethyl ethers(DMMn,n1)by the methanolysis of trioxane.The results suggest that the acidity of PVP-HPAs is tunable by changing the ratio of PVP and HPAs,which is a key factor for the selectivity of the DMMn product.By optimizing the composition and reaction conditions,two types of PVP-HPA,PVP-phosphotungstic acid(PVP-HPW)in a PVP/HPW ratio of 1/4:1 and PVP-silicotungstic acid(PVP-HSi W)in a PVP/HSi W ratio of 1/4:3/4,respectively afford 52.4%and 50.3%yields of DMM2–5.The optimized catalysts are reusable for a minimum of 10 times without a significant drop in performance.展开更多
Electrorheological properties and creep-recovery behavior of polythiophene/polyoxymethylene-blend having PT（50%）/POM（50%） composition were investigated.Particle size,conductivity and dielectric values were measure...Electrorheological properties and creep-recovery behavior of polythiophene/polyoxymethylene-blend having PT（50%）/POM（50%） composition were investigated.Particle size,conductivity and dielectric values were measured to be 24.77μm,3.85×10^（-5） S·m^（-1） and 26.75,respectively.Sedimentation ratio was measured to be 64%at the end of 16 days.The effects of dispersed particle volume fraction,external electric field strength,shear rate,frequency and temperature on ER properties and storage modulus of PT/POM-blend/silicone oil（SO） suspensions were examined.Enhancement were observed in the electric field viscosities of the suspensions and thus they were classified as a smart material.Shear thinning non-Newtonian viscoelastic behavior was determined for PT/POM-blend/SO system.Further,time-dependent deformation was examined by creep-recovery tests and recoverable viscoelastic deformation established.展开更多
The morphologies of poly(L-lactic acid)(PLLA)spherulites,when crystallized within the pre-existed poly(oxymethylene)(POM)crystal frameworks,have been investigated.PLLA/POM blend is a melt-miscible crystalline/crystall...The morphologies of poly(L-lactic acid)(PLLA)spherulites,when crystallized within the pre-existed poly(oxymethylene)(POM)crystal frameworks,have been investigated.PLLA/POM blend is a melt-miscible crystalline/crystalline blend system.Owing to the lower melting point but much faster crystallization rate than PLEA,POM crystallized first upon cooling from the melt state and then melted first during the subsequent heating process in this blend system.Lamellar assembly of PLLA crystals within the pre-existed POM spherulitic frameworks was directly observed with the polarized light microscopy by selectively melting the POM frameworks.The investigation indicated that PLLA crystals fully replicated the spherulitic morphology and optical birefringence of the POM crystal frameworks,which was independent of T_(o).On the other hand,POM could also duplicate the pre-existed PLLA morphologies.The result obtained provides us a possibility to design the lamellar assembly and crystal structures of polymer crystals in miscible crystalline/crystalline polymer blends.展开更多
文摘For a climate-neutral future mobility,the socalled e-fuels can play an essential part.Especially,oxygenated e-fuels containing oxygen in their chemical formula have the additional potential to burn with significantly lower soot levels.In particular,polyoxymethylene dimethyl ethers or oxymethylene ethers(PODEs or OMEs)do not contain carbon-carbon bonds,prohibiting the production of soot precursors like acetylene(C2H2).These properties make OMEs a highly interesting candidate for future climate-neutral compression-ignition engines.However,to fully leverage their potential,the auto-ignition process,flame propagation,and mixing regimes of the combustion need to be understood.To achieve this,efficient oxidation mechanisms suitable for computational fluid dynamics(CFD)calculations must be developed and validated.The present work aims to highlight the improvements made by developing an adapted oxidation mechanism for OME1-6 and introducing it into a validated spray combustion CFD model for OMEs.The simulations were conducted for single-and multi-injection patterns,changing ambient temperatures,and oxygen contents.The results were validated against high-pressure and high-temperature constantpressure chamber experiments.OH*-chemiluminescence measurements accomplished the characterization of the auto-ignition process.Both experiments and simulations were conducted for two different injectors.Significant improvements concerning the prediction of the ignition delay time were accomplished while also retaining an excellent agreement for the flame lift-off length.The spatial zones of high-temperature reaction activity were also affected by the adaption of the reaction kinetics.They showed a greater tendency to form OH*radicals within the center of the spray in accordance with the experiments.
文摘含亚甲氧基桥键负性单体液晶由于具有较大的负介电各向异性,较低的旋转粘度、良好的相溶性而被广泛应用于VA-TFT配方中,但其合成步骤长,合成及提纯难度大。本文讨论了含亚甲氧基桥键及苯环侧向氟取代的负介电各向异性单体液晶的合成方法,该方法主要采用2,3-二氟-4-乙氧基苯酚与含不同长度烷基链的苯磺酸酯反应引入亚甲氧基桥键,避免了常用醚化方法中卤代物的使用和卤素离子对单体液晶性能的影响。使用1 H NMR对目标单体液晶的结构进行了表征;采用DSC、热台偏光显微镜、LCR测试仪等对目标单体液晶的相变温度、光学各向异性、介电各向异性等一系列液晶性能参数进行了测试。
基金financially supported by the National Basic Research Program of China(2011CBA00508)the National Natural Science Foundation of China(21173175,21303141)+1 种基金the Research Fund for the Doctoral Program of Higher Education(20110121130002)the Program for Changjiang Scholars and Innovative Research Team in University(IRT1036)
文摘A series of polyvinylpyrrolidone-stabilized heteropolyacids(PVP-HPAs)are generated by self-assembly of HPAs and PVP in methanol.The PVP-HPAs are then employed as catalysts for the synthesis of poly(oxymethylene)dimethyl ethers(DMMn,n1)by the methanolysis of trioxane.The results suggest that the acidity of PVP-HPAs is tunable by changing the ratio of PVP and HPAs,which is a key factor for the selectivity of the DMMn product.By optimizing the composition and reaction conditions,two types of PVP-HPA,PVP-phosphotungstic acid(PVP-HPW)in a PVP/HPW ratio of 1/4:1 and PVP-silicotungstic acid(PVP-HSi W)in a PVP/HSi W ratio of 1/4:3/4,respectively afford 52.4%and 50.3%yields of DMM2–5.The optimized catalysts are reusable for a minimum of 10 times without a significant drop in performance.
基金financially supported by Turkish Scientific and Technological Research Council(No.107 T 711)
文摘Electrorheological properties and creep-recovery behavior of polythiophene/polyoxymethylene-blend having PT（50%）/POM（50%） composition were investigated.Particle size,conductivity and dielectric values were measured to be 24.77μm,3.85×10^（-5） S·m^（-1） and 26.75,respectively.Sedimentation ratio was measured to be 64%at the end of 16 days.The effects of dispersed particle volume fraction,external electric field strength,shear rate,frequency and temperature on ER properties and storage modulus of PT/POM-blend/silicone oil（SO） suspensions were examined.Enhancement were observed in the electric field viscosities of the suspensions and thus they were classified as a smart material.Shear thinning non-Newtonian viscoelastic behavior was determined for PT/POM-blend/SO system.Further,time-dependent deformation was examined by creep-recovery tests and recoverable viscoelastic deformation established.
基金financially supported by the National Natural Science Foundation of China(Nos.21674033,21374027)National Key R&D Program of China(No.2017YFB0307704)
文摘The morphologies of poly(L-lactic acid)(PLLA)spherulites,when crystallized within the pre-existed poly(oxymethylene)(POM)crystal frameworks,have been investigated.PLLA/POM blend is a melt-miscible crystalline/crystalline blend system.Owing to the lower melting point but much faster crystallization rate than PLEA,POM crystallized first upon cooling from the melt state and then melted first during the subsequent heating process in this blend system.Lamellar assembly of PLLA crystals within the pre-existed POM spherulitic frameworks was directly observed with the polarized light microscopy by selectively melting the POM frameworks.The investigation indicated that PLLA crystals fully replicated the spherulitic morphology and optical birefringence of the POM crystal frameworks,which was independent of T_(o).On the other hand,POM could also duplicate the pre-existed PLLA morphologies.The result obtained provides us a possibility to design the lamellar assembly and crystal structures of polymer crystals in miscible crystalline/crystalline polymer blends.
