The agitated thin-film evaporator(ATFE)plays a crucial role in evaporation and concentration processes.The design of the scraper for processing high-viscosity non-Newtonian fluids in the ATFE is complex.The intricate ...The agitated thin-film evaporator(ATFE)plays a crucial role in evaporation and concentration processes.The design of the scraper for processing high-viscosity non-Newtonian fluids in the ATFE is complex.The intricate scraping action of the scraper introduces gas into the liquid film,leading to the formation of a gas ring along the wall.This process subsequently reduces wall heat flow,thereby affecting heat transfer.Computational fluid dynamics(CFD)is used to simulate the flow field of the non-Newtonian fluid in the ATFE.The investigation focuses on understanding the mechanism behind the formation of gas rings in the liquid film and proposes methods to prevent their formation.The results demonstrate a transition of the gas from a gas ring suspended in the liquid to a gas ring attached to the wall after entering the liquid film.The scraping action around the circumference of the scraper helps to expel gas rings,indicating the necessity of adjusting the scraper arrangement and increasing the frequency of scraping to enhance gas ring expulsion.The spiral motion of the bow wave serves as the source of gas entry into the liquid film.Therefore,the rotation speed can appropriately increase to reduce the size of the bow wave,thereby inhibiting the formation of the gas ring from the source.This research investigates the mechanism of gas ring generation and expulsion,offering theoretical guidance for processing high-viscosity non-Newtonian materials in the flow field of the ATFE.展开更多
The flow field and flow state of thin-film evaporators are complex,and it is significant to effectively divide and quantify the flow field and flow state,as well as to study the internal flow field distribution and ma...The flow field and flow state of thin-film evaporators are complex,and it is significant to effectively divide and quantify the flow field and flow state,as well as to study the internal flow field distribution and material mixing characteristics to improve the efficiency of thin-film evaporators.By using computational fluid dynamics(CFD)numerical simulation,the distribution pattern of the high-viscosity fluid flow field in the thin-film evaporators was obtained.It was found that the staggered interrupted blades could greatly promote material mixing and transportation,and impact the film formation of high-viscosity materials on the evaporator wall.Furthermore,a flow field state recognition method based on radial volume fraction statistics was proposed,and could quantitatively describe the internal flow field of thin-film evaporators.The method divides the high-viscosity materials in the thin-film evaporators into three flow states,the liquid film state,the exchange state and the liquid mass state.The three states of materials could be quantitatively described.The results show that the materials in the exchange state can connect the liquid film and the liquid mass,complete the material mixing and exchange,renew the liquid film,and maintain continuous and efficient liquid film evaporation.展开更多
Graphene has exceptional electrical,optical and thermal properties,and is widely used to create thinner,lighter and faster sensors.In this study,graphene was fabricated by mechanically exfoliating on the SiO_(2)/Si su...Graphene has exceptional electrical,optical and thermal properties,and is widely used to create thinner,lighter and faster sensors.In this study,graphene was fabricated by mechanically exfoliating on the SiO_(2)/Si substrate and the graphene field effect transistor(FET)was prepared by photolithography.Platinum(Pt)particles were doped on the surface of graphene by the hydrazine hydrate reduction method to endow a Pt/graphene sensor with gas-sensing properties.By being tested on a gas detection platform,the characteristics of the electrical(Ⅰ-Ⅴ)curves and resistance response curves were obtained in different hydrogen environments.The results show that the Pt/graphene sensor exhibits a high sensitivity to hydrogen at room temperature,with a resistance response rate of 33.35%at a hydrogen volume fraction of 1.00%.However,the sensitivity lifetime study shows an essential hysteresis in desorption process,which leads to gradually decreases in the resistance response rate.This research provides an improved production method of graphene-based gas sensors,which has a wide range of potential applications in aero-space industry.展开更多
Copper nanowires were fabricated by electrochemical deposition inside anodic alumina template anodized on aluminum substrate. The morphology, composition and structure of the copper nanowires were characterized by mea...Copper nanowires were fabricated by electrochemical deposition inside anodic alumina template anodized on aluminum substrate. The morphology, composition and structure of the copper nanowires were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive (EDS) and X-ray diffraction spectroscopy (XRD). The results revealed that copper nanowires were dense, continuous, highly-crystalline and uniform with diameters. The electrical properties of copper nanowires wrer characterized with two-terminal electrical measurements. Different current-voltage (I-V) characteristics of single copper nanowire were observed and possible conductive mechanisms were discussed. The crystalline copper nanowires are promising in application of future nanoelectronic devices and circuits.展开更多
原子力显微镜(Atomic force microscopy,AFM)对微纳尺度机械加工实施检测和表界面力学性质测量等需要对AFM探针受到的侧向力进行实时测量,因而探针侧向力的标定直接影响测试准确性。基于不同原理的侧向力标定方法,对同一探针通过楔形法...原子力显微镜(Atomic force microscopy,AFM)对微纳尺度机械加工实施检测和表界面力学性质测量等需要对AFM探针受到的侧向力进行实时测量,因而探针侧向力的标定直接影响测试准确性。基于不同原理的侧向力标定方法,对同一探针通过楔形法、反磁悬浮法和非接触法三种常用方法进行标定,对比三种标定方法的稳定性、误差和实用性,对比结果如下:三种标定方法的稳定性都较高,反磁悬浮法和非接触法相对于楔形法的标定误差分别为13.6%和20.4%。探针法向力标定的准确性和侧向力信号随载荷变化的线性度都会影响楔形法标定的准确性;针尖和悬浮石墨片的相对滑动会使反磁悬浮法标定结果偏大,但通过计算滑移距离可以对标定结果进行校正,减小标定误差;非接触法标定结果受探针尺寸的影响较大,可通过对探针尺寸进行表征提高标定结果的准确性。探针标定方法准确性和差异性的分析对比为不同情况下探针标定方法的选择提供了参考依据。展开更多
基金National Natural Science Foundation of China(No.51905089)Fundamental Research Funds for the Central Universities,China(No.2232020D-31)。
文摘The agitated thin-film evaporator(ATFE)plays a crucial role in evaporation and concentration processes.The design of the scraper for processing high-viscosity non-Newtonian fluids in the ATFE is complex.The intricate scraping action of the scraper introduces gas into the liquid film,leading to the formation of a gas ring along the wall.This process subsequently reduces wall heat flow,thereby affecting heat transfer.Computational fluid dynamics(CFD)is used to simulate the flow field of the non-Newtonian fluid in the ATFE.The investigation focuses on understanding the mechanism behind the formation of gas rings in the liquid film and proposes methods to prevent their formation.The results demonstrate a transition of the gas from a gas ring suspended in the liquid to a gas ring attached to the wall after entering the liquid film.The scraping action around the circumference of the scraper helps to expel gas rings,indicating the necessity of adjusting the scraper arrangement and increasing the frequency of scraping to enhance gas ring expulsion.The spiral motion of the bow wave serves as the source of gas entry into the liquid film.Therefore,the rotation speed can appropriately increase to reduce the size of the bow wave,thereby inhibiting the formation of the gas ring from the source.This research investigates the mechanism of gas ring generation and expulsion,offering theoretical guidance for processing high-viscosity non-Newtonian materials in the flow field of the ATFE.
基金National Natural Science Foundation of China(Nos.51905089 and 52075093)Special Fund for Basic Research and Operating Costs of Central Colleges and Universities,China(No.22320D-31)Open Fund for National Key Laboratory of Tribology of Tsinghua University,China(No.SKLTKF20B05)。
文摘The flow field and flow state of thin-film evaporators are complex,and it is significant to effectively divide and quantify the flow field and flow state,as well as to study the internal flow field distribution and material mixing characteristics to improve the efficiency of thin-film evaporators.By using computational fluid dynamics(CFD)numerical simulation,the distribution pattern of the high-viscosity fluid flow field in the thin-film evaporators was obtained.It was found that the staggered interrupted blades could greatly promote material mixing and transportation,and impact the film formation of high-viscosity materials on the evaporator wall.Furthermore,a flow field state recognition method based on radial volume fraction statistics was proposed,and could quantitatively describe the internal flow field of thin-film evaporators.The method divides the high-viscosity materials in the thin-film evaporators into three flow states,the liquid film state,the exchange state and the liquid mass state.The three states of materials could be quantitatively described.The results show that the materials in the exchange state can connect the liquid film and the liquid mass,complete the material mixing and exchange,renew the liquid film,and maintain continuous and efficient liquid film evaporation.
基金National Natural Science Foundation of China(No.51905090)。
文摘Graphene has exceptional electrical,optical and thermal properties,and is widely used to create thinner,lighter and faster sensors.In this study,graphene was fabricated by mechanically exfoliating on the SiO_(2)/Si substrate and the graphene field effect transistor(FET)was prepared by photolithography.Platinum(Pt)particles were doped on the surface of graphene by the hydrazine hydrate reduction method to endow a Pt/graphene sensor with gas-sensing properties.By being tested on a gas detection platform,the characteristics of the electrical(Ⅰ-Ⅴ)curves and resistance response curves were obtained in different hydrogen environments.The results show that the Pt/graphene sensor exhibits a high sensitivity to hydrogen at room temperature,with a resistance response rate of 33.35%at a hydrogen volume fraction of 1.00%.However,the sensitivity lifetime study shows an essential hysteresis in desorption process,which leads to gradually decreases in the resistance response rate.This research provides an improved production method of graphene-based gas sensors,which has a wide range of potential applications in aero-space industry.
基金supported by the National Natural Science Foundation of China (51002030)International Cooperation Project in Suzhou (SH201117)+1 种基金Excellent Young Teacher Support Plan of Southeast University,in part by the New Century Talents of Ministry of Education (NCET-11-0095)the PhD Program Foundation of Ministry of Education of China(20100092120006)
文摘Copper nanowires were fabricated by electrochemical deposition inside anodic alumina template anodized on aluminum substrate. The morphology, composition and structure of the copper nanowires were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive (EDS) and X-ray diffraction spectroscopy (XRD). The results revealed that copper nanowires were dense, continuous, highly-crystalline and uniform with diameters. The electrical properties of copper nanowires wrer characterized with two-terminal electrical measurements. Different current-voltage (I-V) characteristics of single copper nanowire were observed and possible conductive mechanisms were discussed. The crystalline copper nanowires are promising in application of future nanoelectronic devices and circuits.
文摘原子力显微镜(Atomic force microscopy,AFM)对微纳尺度机械加工实施检测和表界面力学性质测量等需要对AFM探针受到的侧向力进行实时测量,因而探针侧向力的标定直接影响测试准确性。基于不同原理的侧向力标定方法,对同一探针通过楔形法、反磁悬浮法和非接触法三种常用方法进行标定,对比三种标定方法的稳定性、误差和实用性,对比结果如下:三种标定方法的稳定性都较高,反磁悬浮法和非接触法相对于楔形法的标定误差分别为13.6%和20.4%。探针法向力标定的准确性和侧向力信号随载荷变化的线性度都会影响楔形法标定的准确性;针尖和悬浮石墨片的相对滑动会使反磁悬浮法标定结果偏大,但通过计算滑移距离可以对标定结果进行校正,减小标定误差;非接触法标定结果受探针尺寸的影响较大,可通过对探针尺寸进行表征提高标定结果的准确性。探针标定方法准确性和差异性的分析对比为不同情况下探针标定方法的选择提供了参考依据。
