Triboelectric nanogenerators(TENGs)as a clean energy-harvesting technology are experiencing significant growth in the pursuit of carbon neutrality,accompanied by the increasing use of environmentally friendly biomater...Triboelectric nanogenerators(TENGs)as a clean energy-harvesting technology are experiencing significant growth in the pursuit of carbon neutrality,accompanied by the increasing use of environmentally friendly biomaterials.However,biomaterials exhibit inferior triboelectric properties compared with petromaterials,hindering the development of bio-based TENGs.Here,leveraging the crystal boundary-tuning strategy,we develop a chitosan aerogel-based TENG(CS-TENG)that is capable of delivering power density over 116 W m-2,beyond that of the previous reports for CS-TENG by an order of magnitude.With a high output voltage of 3200 V,the CS-TENG directly illuminated 1000 LEDs in series.Notably,the CS aerogel exhibits self-healing,waste recycling and gas-sensitive properties,ensuring the long-term durability,environmental benignity and sensing characteristics of the CS-TENG.Furthermore,a breathactivated mask-integrated CS-TENG ammonia monitoring system is engineered,which accurately detects changes in ammonia concentration within the range of 10-160 ppm,enabling real-time monitoring of ammonia in the environment.Our results set a record for the ultrahigh power density of CS-TENG,representing a significant advancement in the practical application of TENGs.展开更多
To address the persistent challenges of low sensingd performance,ambiguous sensing mechanisms,and difficult portable monitoring in existing MXene-based NH,sensors,this study developed a high-performance MoO_(3)@Ti_(3)...To address the persistent challenges of low sensingd performance,ambiguous sensing mechanisms,and difficult portable monitoring in existing MXene-based NH,sensors,this study developed a high-performance MoO_(3)@Ti_(3)C_(2)T_(x)room-temperature NHs sensor through ultrasonic composite modification.The MoO_(3)@Ti_(3)C_(2)T_(x)sensor demonstrated significant sensitivity to NH,at room temperature,with excellent long-term stability,fast response recovery time(14 s/24 s),and excellent selectivity,which are superior to those of most reported Ti_(3)C_(2)Txbased and intrinsic MoOs sensors.Owing to the unique microstructure of MoO_(3)@Ti_(3)C_(2)T_(x),the dual active sites of Ti_(3)C_(2)T_(x)functional groups(-O/-F/-OH)and oxygen vacancies facilitate the oxidative adsorption and dissociation of NH3.The formation of interfacial Schottky junctions and charge regulation significantly enhanced the gas sensitivity of MoO_(3)@Ti_(3)C_(2)T_(x)toward NH,,Densityl functional theory(DFT)simulations further revealed an increased NH,adsorption energy and strong atomic orbital hybridization at the heterointerface.Furthermore,this study integrated the MoO_(3)@Ti_(3)C_(2)T_(x)sensor into a multifunctional Internet of Things(loT)lmonitoring system,which enabled real-time visualization of NH,detection through threshold-triggered alarms,demonstrating its utility in smart agriculture.展开更多
Self-healable and flexible all-in-one self-powering smartsensing devices have recently attracted great attention.Herein,a flexible all-in-one solid-state electronic system of polyvinyl alcohol(PVA)hydrogel-based super...Self-healable and flexible all-in-one self-powering smartsensing devices have recently attracted great attention.Herein,a flexible all-in-one solid-state electronic system of polyvinyl alcohol(PVA)hydrogel-based supercapacitors for self-powering ammonia smartsensors has been fabricated.Self-healing supercapacitors are prepared by integrating polypyrrole(PPy)and boron crosslinked PVA/KCl hydrogel as a sandwich configuration,exhibiting large specific capacitance of 244.81 mF cm^(-2)at 0.47 mA cm^(-2),and good charging/discharging stability of 2000 cycles,while ammonia sensors are realized by a SnO_(2)/PPy-modified conductive PVA hydrogel film,demonstrating an excellent sensing behavior toward NH_(3) vapor under 50 ppb–500 ppm.As a result,selfhealing supercapacitors could well store energy and then self-power sensing unit for remotely real-time detection via a smartphone,acquiring high flexibility of energy-sensing system.With attractive biocompatibility and selfhealing performance toward various environment,this all-in-one flexible energy-smartsensor system would pave the way to novel fabrication process in realization of wearable self-healing smart devices.展开更多
As an excellent room temperature sensing material,polyaniline(PANI)needs to be further investigated in the field of high sensitivity and sustainable gas sensors due to its long recovery time and difficulty to complete...As an excellent room temperature sensing material,polyaniline(PANI)needs to be further investigated in the field of high sensitivity and sustainable gas sensors due to its long recovery time and difficulty to complete recovery.The ZnO/PANI film with p-n heterogeneous energy levels have successfully prepared by spraying Zno nanorod synthesized by hydrothermal method on the PANI film rapidly synthesized at the gas-liquid interface.The presence of p-n heterogeneous energy levels enables the ZnO/PANI film to detect 0.1-100 ppm(1 ppm=10^(-6))NH_(3)at room temperature with the response value to 100 ppm NH_(3)doubled(12.96)and the recovery time shortened to 1/5(31.2s).The ability of high response and fast recovery makes the ZnO/PANI filmto be able to detect NH_(3)at room temperature continuously.It provides a new idea for PANI to prepare sustainable room temperature sensor and promotes the development of room temperature sensor in public safety.展开更多
Ammonia sensors have broad spectrum of applications for industrial process control as well as for environ-mental monitoring. An optical fiber ammonia sensor probe has been developed by using a bent optical fiber havin...Ammonia sensors have broad spectrum of applications for industrial process control as well as for environ-mental monitoring. An optical fiber ammonia sensor probe has been developed by using a bent optical fiber having dual poly(methyl methacrylate) (PMMA)/chlorophenol red (CPR) coatings as a transducer. This sen-sor probe was tested for monitoring trace ammonia in gas samples using air as sample matrix. The reaction of ammonia with CPR causes a color change of the reagent, which was detected by using fiber optic evanes-cent wave absorption spectrometry as a sensing signal. By adopting a dual layer coating structure, the sensor probe has faster response compared to a sensor using a broadly accepted sensing reagent-immobilized poly-mer coating structure. The sensor developed in this work is sensitive, has a detection limit of 2.7 ppb NH3 in air, which is the most sensitive among the reported optical fiber ammonia sensors to the best knowledge of the authors. The sensor is also reversible and has a response time of 25 minutes. The features of high sensi-tivity, reversibility and reasonable response time make this sensor technique very attractive for air quality monitoring.展开更多
Conventional metal-oxide-semiconductor(MOS)gas sensors are limited in wearable gas detection due to their non-flexibility,high operating temperature,and less durability.In this study,a yarn-based superhydrophobic flex...Conventional metal-oxide-semiconductor(MOS)gas sensors are limited in wearable gas detection due to their non-flexibility,high operating temperature,and less durability.In this study,a yarn-based superhydrophobic flexible wearable sensor for room-temperature ammonia gas detection was prepared based on the nano-size effect of both nanocore yarns prepared through electrostatic spinning and MOS gas-sensitive materials synthesized via a two-step hydrothermal synthesis approach.The yarn sensor has a response sensitivity of 13.11 towards 100 ppm(1 ppm=10^(−6))ammonia at room temperature,a response time and a recovery time of 36 and 21 s,respectively,and a detection limit as low as 10 ppm with the sensitivity of up to 4.76 towards ammonia.In addition,it displays commendable linearity within the concentration range of 10‒100 ppm,accompanied by remarkable selectivity and stability,while the hydrophobicity angle reaches 155.74°.Furthermore,its sensing performance still maintains stability even after repeated bending and prolonged operation.The sensor also has stable mechanical properties and flexibility,and can be affixed onto the fabric surface through sewing,which has a specific potential for clothing use.展开更多
生鲜农产品易发生品质劣变,其中氨气是反映其品质变化的重要检测指标。针对传统有芯片氨气传感器电路设计复杂、寿命有限问题,设计了一种无芯片射频识别(Radio frequency identification,RFID)氨气传感器,用于生鲜农产品挥发性氨气检测...生鲜农产品易发生品质劣变,其中氨气是反映其品质变化的重要检测指标。针对传统有芯片氨气传感器电路设计复杂、寿命有限问题,设计了一种无芯片射频识别(Radio frequency identification,RFID)氨气传感器,用于生鲜农产品挥发性氨气检测。首先,基于高频电磁仿真软件(High frequency structure simulator,HFSS)设计了微带贴片天线结构,研究了传感器天线的电磁场分布、回波损耗S11和极化特性,通过在微带天线上加载金属短路和寄生单元优化了传感器结构;采用激光雕刻技术制备传感器标签,并选择了在室温下对氨气具有良好选择性的ZnO/TiO_(2)纳米复合材料,将其喷涂在微带天线表面辐射单元上;其次,结合氨气射频检测原理,搭建了基于无芯片RFID的生鲜农产品挥发性氨气测试系统,分析了传感器的交叉敏感性和低温高湿环境下的稳定性,最后,对实际测试结果进行了主成分分析和Pearson相关分析。试验结果表明,该无芯片RFID传感器中心谐振频率为2.25 GHz,加载金属短路后增益提升0.13 dB,在实验室氨气质量浓度0~100 mg/L环境下灵敏度达到0.11 dB·L/mg,实际测试过程中,鸡肉氨气传感响应值较高,为9.0 dB;虾肉氨传感响应值较低,为4.5 dB。此外,传感器检测响应能有效区分干扰气体(H_(2)S、CO_(2)、CH_(4)、C2H5OH),相关系数绝对均值均小于0.5;在低温高湿环境下,传感器能够有效完成氨气检测,且稳定性良好。展开更多
Polypyrrole (Ppy) was synthesized using Ferric Chloride (FeCl3) as oxidant. The ratio of monomer to oxidant was 1:2.4. The polymerization was carried out at 5。C. Attempts were made to increase the electrical conduc-t...Polypyrrole (Ppy) was synthesized using Ferric Chloride (FeCl3) as oxidant. The ratio of monomer to oxidant was 1:2.4. The polymerization was carried out at 5。C. Attempts were made to increase the electrical conduc-tivity by using various dopants viz. Lithium per Chlorate (LiClO4), para-Toluene Sulfonate (p-TS) and Nap-thalene Sulfonic acid (NSA). The materials were characterized using FTIR, X-Ray diffraction and SEM. The electrical conductivity was measured by two probe method and was found to be in the range of 10-3 to 10-2 S/cm. Thin films of these preparations were casted on the interdigited electrodes to study the detection of gases such as ammonia and LPG. It was found that for the pure Ppy and one doped with LiClO4, when ammonia gas was allowed to flow in, there was a sudden increase in the current, which decreased rapidly when gas was stopped. This behavior is in contradiction to that observed in earlier investigations where Ppy was prepared by electrochemical method. However when Ppy doped with p-TS and NSA were used, the trend was reversed. Similarly it was noted that for pure Ppy and one doped with LiClO4, p-TS and NSA there was an increase in the current when LPG gas was brought in. However the response to LPG was somewhat low as compared ammonia gas.展开更多
Polypyrrole (Ppy) was synthesized using Ammonium Peroxy Disulfate (APS) as oxidant in a standard ratio of monomer to oxidants at 5℃. Attempts were made to increase the electrical conductivity by using various dopants...Polypyrrole (Ppy) was synthesized using Ammonium Peroxy Disulfate (APS) as oxidant in a standard ratio of monomer to oxidants at 5℃. Attempts were made to increase the electrical conductivity by using various dopants viz. Lithium per Chlorate (LiClO4), para-Toluene Sulfonate (p-TS) and Napthalene Sulfonic acid (NSA). The materials were characterized using FTIR, X Ray diffraction and SEM. The electrical conductivity was measured by two probe method and was found to be in the range of 10-3 S/cm. Thin films of these preparations were casted on the interdigited electrodes to study the detection of gas such as ammonia. It was found that for the pure Ppy when ammonia gas was allowed to flow in, there was a sudden increase in the current, which decreased rapidly when gas was stopped. However when Ppy doped with p-TS, NSA and LiClO4, the trend was reversed.展开更多
Selective Catalytic Reduction (SCR) catalysts respond slowly to transient inputs, which is troublesome when designing ammonia feed controllers. An experimental SCR test apparatus installed on a slipstream of a Coo-per...Selective Catalytic Reduction (SCR) catalysts respond slowly to transient inputs, which is troublesome when designing ammonia feed controllers. An experimental SCR test apparatus installed on a slipstream of a Coo-per-Bessemer GMV-4, 2-stroke cycle natural gas engine is utilized. Ammonia (NH3) feed rate control algo-rithm development is carried out. Two control algorithms are evaluated: a feed forward control algorithm, using a pre ammonia injection ceramic NOx sensor and a feed forward plus feedback control algorithm, us-ing a pre ammonia injection ceramic NOx sensor and post catalyst ceramic NOx sensor to generate feedback signals. The feed forward algorithm controls to constant user input NH3/NOx molar ratio. The data show the lack of pressure compensation on the ceramic NOx sensors cause errors in feed forward NOx readings, re-sulting in sub optimal ammonia feed. The feedback system minimizes the post catalyst ceramic NOx sensor signal by adjusting the NH3/NOx molar ratio. The NOx sensors respond to ammonia + NOx;therefore, the feed forward plus feedback algorithm minimizes the sum of NOx emissions and ammonia slip. Successful application of the feedback control minimization technique is demonstrated with feedback periods of 15 and 5 minutes with molar ratio step sizes of 5 and 2.5%, respectively.展开更多
氨气是畜禽场景中的主要有害气体之一,针对有源传感器不适于电路有线连接受限的畜禽场景问题,该研究基于高频电磁仿真软件(high frequency structure simulator,HFSS)设计了无源传感器仿真模型,选择聚酰亚胺(polyimide,PI)作为基板材料...氨气是畜禽场景中的主要有害气体之一,针对有源传感器不适于电路有线连接受限的畜禽场景问题,该研究基于高频电磁仿真软件(high frequency structure simulator,HFSS)设计了无源传感器仿真模型,选择聚酰亚胺(polyimide,PI)作为基板材料,采用丝网印刷技术研制了基于射频识别(radio frequency identification,RFID)原理的无源氨气传感标签。通过对氨气无源检测原理的解析,选择了具有高表面积的碳纳米管作为氨气敏感材料,推导了通过测量射频接收功率变化实现无源检测的数学模型;考虑谐振频率的动态调整,无源RFID传感标签采用开口间隙可调的裂环谐振器结构,通过分析传输系数的变化对RFID传感标签的检测过程进行模拟;搭建了用于实验室和畜禽场景氨气检测的射频测试系统,围绕功率反射系数、谐振频率、传输系数开展测试分析。试验结果表明,该标签检测效率易受到到二氧化碳、温湿度因素的影响,由于人工切割、基板变形、环境干扰等因素,实物标签的谐振频率与2.4 GHz的仿真谐振频率之间存在0.05 GHz左右的偏差,传感标签的灵敏度约为15 MHz·L/mg,最大阅读距离为24 cm,相比于商用氨气传感器,该传感标签在使用寿命、响应时间方面有明显优势。研究结果为畜禽场景的氨气无源检测提供了有效的理论和实践依据。展开更多
基金Key Program of the National Natural Science Foundation of China,Grant/Award Number:U22B2089General Program of National Natural Science Foundation of China,Grant/Award Number:52075061Science Fund for Distinguished Young Scholars of Chongqing,Grant/Award Number:CSTB2022 NSCQJQX0006。
文摘Triboelectric nanogenerators(TENGs)as a clean energy-harvesting technology are experiencing significant growth in the pursuit of carbon neutrality,accompanied by the increasing use of environmentally friendly biomaterials.However,biomaterials exhibit inferior triboelectric properties compared with petromaterials,hindering the development of bio-based TENGs.Here,leveraging the crystal boundary-tuning strategy,we develop a chitosan aerogel-based TENG(CS-TENG)that is capable of delivering power density over 116 W m-2,beyond that of the previous reports for CS-TENG by an order of magnitude.With a high output voltage of 3200 V,the CS-TENG directly illuminated 1000 LEDs in series.Notably,the CS aerogel exhibits self-healing,waste recycling and gas-sensitive properties,ensuring the long-term durability,environmental benignity and sensing characteristics of the CS-TENG.Furthermore,a breathactivated mask-integrated CS-TENG ammonia monitoring system is engineered,which accurately detects changes in ammonia concentration within the range of 10-160 ppm,enabling real-time monitoring of ammonia in the environment.Our results set a record for the ultrahigh power density of CS-TENG,representing a significant advancement in the practical application of TENGs.
基金supported in part by the National Natural Science Foundation of China(No.52077177)the Graduate Research and Innovation Project of Southwest University(No.SWUS23096).
文摘To address the persistent challenges of low sensingd performance,ambiguous sensing mechanisms,and difficult portable monitoring in existing MXene-based NH,sensors,this study developed a high-performance MoO_(3)@Ti_(3)C_(2)T_(x)room-temperature NHs sensor through ultrasonic composite modification.The MoO_(3)@Ti_(3)C_(2)T_(x)sensor demonstrated significant sensitivity to NH,at room temperature,with excellent long-term stability,fast response recovery time(14 s/24 s),and excellent selectivity,which are superior to those of most reported Ti_(3)C_(2)Txbased and intrinsic MoOs sensors.Owing to the unique microstructure of MoO_(3)@Ti_(3)C_(2)T_(x),the dual active sites of Ti_(3)C_(2)T_(x)functional groups(-O/-F/-OH)and oxygen vacancies facilitate the oxidative adsorption and dissociation of NH3.The formation of interfacial Schottky junctions and charge regulation significantly enhanced the gas sensitivity of MoO_(3)@Ti_(3)C_(2)T_(x)toward NH,,Densityl functional theory(DFT)simulations further revealed an increased NH,adsorption energy and strong atomic orbital hybridization at the heterointerface.Furthermore,this study integrated the MoO_(3)@Ti_(3)C_(2)T_(x)sensor into a multifunctional Internet of Things(loT)lmonitoring system,which enabled real-time visualization of NH,detection through threshold-triggered alarms,demonstrating its utility in smart agriculture.
基金financial support from National Natural Science Foundation of China(Grant No.22074010)Dalian Science and Technology Bureau,China(Grant No.2019J12SN54)+1 种基金Basic and Applied Basic Research Program of Guangzhou City,China(Grant No.202002030434)Zhang Dayu School of Chemistry,Dalian University of Technology,China。
文摘Self-healable and flexible all-in-one self-powering smartsensing devices have recently attracted great attention.Herein,a flexible all-in-one solid-state electronic system of polyvinyl alcohol(PVA)hydrogel-based supercapacitors for self-powering ammonia smartsensors has been fabricated.Self-healing supercapacitors are prepared by integrating polypyrrole(PPy)and boron crosslinked PVA/KCl hydrogel as a sandwich configuration,exhibiting large specific capacitance of 244.81 mF cm^(-2)at 0.47 mA cm^(-2),and good charging/discharging stability of 2000 cycles,while ammonia sensors are realized by a SnO_(2)/PPy-modified conductive PVA hydrogel film,demonstrating an excellent sensing behavior toward NH_(3) vapor under 50 ppb–500 ppm.As a result,selfhealing supercapacitors could well store energy and then self-power sensing unit for remotely real-time detection via a smartphone,acquiring high flexibility of energy-sensing system.With attractive biocompatibility and selfhealing performance toward various environment,this all-in-one flexible energy-smartsensor system would pave the way to novel fabrication process in realization of wearable self-healing smart devices.
基金supported by the National Natural Science Foundation of China(Grant Nos.21771060 and 61271126)the International Science&Technology Cooperation Program of China(Grant No.2016YFE0115100)+2 种基金the Program for Science and Technology Project of Heilongjiang Province(Grant No.JQ2021B002)the Heilongjiang Provincial Natural Science Foundation of China(Grant No.2019LH0320)the Reform and Development Fund Project of Local University supported by the Central Government,Heilongjiang Touyan Innovation Team Program.
文摘As an excellent room temperature sensing material,polyaniline(PANI)needs to be further investigated in the field of high sensitivity and sustainable gas sensors due to its long recovery time and difficulty to complete recovery.The ZnO/PANI film with p-n heterogeneous energy levels have successfully prepared by spraying Zno nanorod synthesized by hydrothermal method on the PANI film rapidly synthesized at the gas-liquid interface.The presence of p-n heterogeneous energy levels enables the ZnO/PANI film to detect 0.1-100 ppm(1 ppm=10^(-6))NH_(3)at room temperature with the response value to 100 ppm NH_(3)doubled(12.96)and the recovery time shortened to 1/5(31.2s).The ability of high response and fast recovery makes the ZnO/PANI filmto be able to detect NH_(3)at room temperature continuously.It provides a new idea for PANI to prepare sustainable room temperature sensor and promotes the development of room temperature sensor in public safety.
文摘Ammonia sensors have broad spectrum of applications for industrial process control as well as for environ-mental monitoring. An optical fiber ammonia sensor probe has been developed by using a bent optical fiber having dual poly(methyl methacrylate) (PMMA)/chlorophenol red (CPR) coatings as a transducer. This sen-sor probe was tested for monitoring trace ammonia in gas samples using air as sample matrix. The reaction of ammonia with CPR causes a color change of the reagent, which was detected by using fiber optic evanes-cent wave absorption spectrometry as a sensing signal. By adopting a dual layer coating structure, the sensor probe has faster response compared to a sensor using a broadly accepted sensing reagent-immobilized poly-mer coating structure. The sensor developed in this work is sensitive, has a detection limit of 2.7 ppb NH3 in air, which is the most sensitive among the reported optical fiber ammonia sensors to the best knowledge of the authors. The sensor is also reversible and has a response time of 25 minutes. The features of high sensi-tivity, reversibility and reasonable response time make this sensor technique very attractive for air quality monitoring.
基金supported by the Fund of China National-Textile and Apparel Council(Grant Nos.2022033 and 2022015).
文摘Conventional metal-oxide-semiconductor(MOS)gas sensors are limited in wearable gas detection due to their non-flexibility,high operating temperature,and less durability.In this study,a yarn-based superhydrophobic flexible wearable sensor for room-temperature ammonia gas detection was prepared based on the nano-size effect of both nanocore yarns prepared through electrostatic spinning and MOS gas-sensitive materials synthesized via a two-step hydrothermal synthesis approach.The yarn sensor has a response sensitivity of 13.11 towards 100 ppm(1 ppm=10^(−6))ammonia at room temperature,a response time and a recovery time of 36 and 21 s,respectively,and a detection limit as low as 10 ppm with the sensitivity of up to 4.76 towards ammonia.In addition,it displays commendable linearity within the concentration range of 10‒100 ppm,accompanied by remarkable selectivity and stability,while the hydrophobicity angle reaches 155.74°.Furthermore,its sensing performance still maintains stability even after repeated bending and prolonged operation.The sensor also has stable mechanical properties and flexibility,and can be affixed onto the fabric surface through sewing,which has a specific potential for clothing use.
文摘Polypyrrole (Ppy) was synthesized using Ferric Chloride (FeCl3) as oxidant. The ratio of monomer to oxidant was 1:2.4. The polymerization was carried out at 5。C. Attempts were made to increase the electrical conduc-tivity by using various dopants viz. Lithium per Chlorate (LiClO4), para-Toluene Sulfonate (p-TS) and Nap-thalene Sulfonic acid (NSA). The materials were characterized using FTIR, X-Ray diffraction and SEM. The electrical conductivity was measured by two probe method and was found to be in the range of 10-3 to 10-2 S/cm. Thin films of these preparations were casted on the interdigited electrodes to study the detection of gases such as ammonia and LPG. It was found that for the pure Ppy and one doped with LiClO4, when ammonia gas was allowed to flow in, there was a sudden increase in the current, which decreased rapidly when gas was stopped. This behavior is in contradiction to that observed in earlier investigations where Ppy was prepared by electrochemical method. However when Ppy doped with p-TS and NSA were used, the trend was reversed. Similarly it was noted that for pure Ppy and one doped with LiClO4, p-TS and NSA there was an increase in the current when LPG gas was brought in. However the response to LPG was somewhat low as compared ammonia gas.
文摘Polypyrrole (Ppy) was synthesized using Ammonium Peroxy Disulfate (APS) as oxidant in a standard ratio of monomer to oxidants at 5℃. Attempts were made to increase the electrical conductivity by using various dopants viz. Lithium per Chlorate (LiClO4), para-Toluene Sulfonate (p-TS) and Napthalene Sulfonic acid (NSA). The materials were characterized using FTIR, X Ray diffraction and SEM. The electrical conductivity was measured by two probe method and was found to be in the range of 10-3 S/cm. Thin films of these preparations were casted on the interdigited electrodes to study the detection of gas such as ammonia. It was found that for the pure Ppy when ammonia gas was allowed to flow in, there was a sudden increase in the current, which decreased rapidly when gas was stopped. However when Ppy doped with p-TS, NSA and LiClO4, the trend was reversed.
文摘Selective Catalytic Reduction (SCR) catalysts respond slowly to transient inputs, which is troublesome when designing ammonia feed controllers. An experimental SCR test apparatus installed on a slipstream of a Coo-per-Bessemer GMV-4, 2-stroke cycle natural gas engine is utilized. Ammonia (NH3) feed rate control algo-rithm development is carried out. Two control algorithms are evaluated: a feed forward control algorithm, using a pre ammonia injection ceramic NOx sensor and a feed forward plus feedback control algorithm, us-ing a pre ammonia injection ceramic NOx sensor and post catalyst ceramic NOx sensor to generate feedback signals. The feed forward algorithm controls to constant user input NH3/NOx molar ratio. The data show the lack of pressure compensation on the ceramic NOx sensors cause errors in feed forward NOx readings, re-sulting in sub optimal ammonia feed. The feedback system minimizes the post catalyst ceramic NOx sensor signal by adjusting the NH3/NOx molar ratio. The NOx sensors respond to ammonia + NOx;therefore, the feed forward plus feedback algorithm minimizes the sum of NOx emissions and ammonia slip. Successful application of the feedback control minimization technique is demonstrated with feedback periods of 15 and 5 minutes with molar ratio step sizes of 5 and 2.5%, respectively.
文摘氨气是畜禽场景中的主要有害气体之一,针对有源传感器不适于电路有线连接受限的畜禽场景问题,该研究基于高频电磁仿真软件(high frequency structure simulator,HFSS)设计了无源传感器仿真模型,选择聚酰亚胺(polyimide,PI)作为基板材料,采用丝网印刷技术研制了基于射频识别(radio frequency identification,RFID)原理的无源氨气传感标签。通过对氨气无源检测原理的解析,选择了具有高表面积的碳纳米管作为氨气敏感材料,推导了通过测量射频接收功率变化实现无源检测的数学模型;考虑谐振频率的动态调整,无源RFID传感标签采用开口间隙可调的裂环谐振器结构,通过分析传输系数的变化对RFID传感标签的检测过程进行模拟;搭建了用于实验室和畜禽场景氨气检测的射频测试系统,围绕功率反射系数、谐振频率、传输系数开展测试分析。试验结果表明,该标签检测效率易受到到二氧化碳、温湿度因素的影响,由于人工切割、基板变形、环境干扰等因素,实物标签的谐振频率与2.4 GHz的仿真谐振频率之间存在0.05 GHz左右的偏差,传感标签的灵敏度约为15 MHz·L/mg,最大阅读距离为24 cm,相比于商用氨气传感器,该传感标签在使用寿命、响应时间方面有明显优势。研究结果为畜禽场景的氨气无源检测提供了有效的理论和实践依据。
