High-performance graphite materials have important roles in aerospace and nuclear reactor technologies because of their outstanding chemical stability and high-temperature performance.Their traditional production meth...High-performance graphite materials have important roles in aerospace and nuclear reactor technologies because of their outstanding chemical stability and high-temperature performance.Their traditional production method relies on repeated impregnation-carbonization and graphitization,and is plagued by lengthy preparation cycles and high energy consumption.Phase transition-assisted self-pressurized selfsintering technology can rapidly produce high-strength graphite materials,but the fracture strain of the graphite materials produced is poor.To solve this problem,this study used a two-step sintering method to uniformly introduce micro-nano pores into natural graphite-based bulk graphite,achieving improved fracture strain of the samples without reducing their density and mechanical properties.Using natural graphite powder,micron-diamond,and nano-diamond as raw materials,and by precisely controlling the staged pressure release process,the degree of diamond phase transition expansion was effectively regulated.The strain-to-failure of the graphite samples reached 1.2%,a 35%increase compared to samples produced by fullpressure sintering.Meanwhile,their flexural strength exceeded 110 MPa,and their density was over 1.9 g/cm^(3).The process therefore produced both a high strength and a high fracture strain.The interface evolution and toughening mechanism during the two-step sintering process were investigated.It is believed that the micro-nano pores formed have two roles:as stress concentrators they induce yielding by shear and as multi-crack propagation paths they significantly lengthen the crack propagation path.The two-step sintering phase transition strategy introduces pores and provides a new approach for increasing the fracture strain of brittle materials.展开更多
从实际工程应用出发,建立了单塔双循环湿式烟气脱硫(Single-tower and double-circulation wet flue gas desulfurization,SD-WFGD)系统的控制系统。首先,利用历史运行数据,考虑SD-WFGD系统运行过程吸收塔变频浆液循环泵在不同浆液pH时...从实际工程应用出发,建立了单塔双循环湿式烟气脱硫(Single-tower and double-circulation wet flue gas desulfurization,SD-WFGD)系统的控制系统。首先,利用历史运行数据,考虑SD-WFGD系统运行过程吸收塔变频浆液循环泵在不同浆液pH时单位频率变化对烟气SO_(2)浓度的影响,建立了系统动态模型。然后,基于浆液pH脱硫能力提出了直接硫量平衡控制(Direct sulfur balance control,DSC)策略,将已建立的动态模型作为控制模型,并利用传统PID控制器结合DSC策略,建立了SD-WFGD系统串联控制系统。仿真实验结果表明:与传统的PID控制方案相比,所提优化控制方案减小了供浆流量和出口SO_(2)浓度的波动,能够大幅度提升SD-WFGD系统的控制性能,从而更好地保证脱硫系统在燃煤电站灵活运行的背景下安全、稳定、经济及灵活运行。展开更多
基金Natural Science Foundation of Shanghai(24ZR1400800)he Natural Science Foundation of China(U23A20685,52073058,91963204)+1 种基金the National Key R&D Program of China(2021YFB3701400)Shanghai Sailing Program(23YF1400200)。
文摘High-performance graphite materials have important roles in aerospace and nuclear reactor technologies because of their outstanding chemical stability and high-temperature performance.Their traditional production method relies on repeated impregnation-carbonization and graphitization,and is plagued by lengthy preparation cycles and high energy consumption.Phase transition-assisted self-pressurized selfsintering technology can rapidly produce high-strength graphite materials,but the fracture strain of the graphite materials produced is poor.To solve this problem,this study used a two-step sintering method to uniformly introduce micro-nano pores into natural graphite-based bulk graphite,achieving improved fracture strain of the samples without reducing their density and mechanical properties.Using natural graphite powder,micron-diamond,and nano-diamond as raw materials,and by precisely controlling the staged pressure release process,the degree of diamond phase transition expansion was effectively regulated.The strain-to-failure of the graphite samples reached 1.2%,a 35%increase compared to samples produced by fullpressure sintering.Meanwhile,their flexural strength exceeded 110 MPa,and their density was over 1.9 g/cm^(3).The process therefore produced both a high strength and a high fracture strain.The interface evolution and toughening mechanism during the two-step sintering process were investigated.It is believed that the micro-nano pores formed have two roles:as stress concentrators they induce yielding by shear and as multi-crack propagation paths they significantly lengthen the crack propagation path.The two-step sintering phase transition strategy introduces pores and provides a new approach for increasing the fracture strain of brittle materials.
文摘从实际工程应用出发,建立了单塔双循环湿式烟气脱硫(Single-tower and double-circulation wet flue gas desulfurization,SD-WFGD)系统的控制系统。首先,利用历史运行数据,考虑SD-WFGD系统运行过程吸收塔变频浆液循环泵在不同浆液pH时单位频率变化对烟气SO_(2)浓度的影响,建立了系统动态模型。然后,基于浆液pH脱硫能力提出了直接硫量平衡控制(Direct sulfur balance control,DSC)策略,将已建立的动态模型作为控制模型,并利用传统PID控制器结合DSC策略,建立了SD-WFGD系统串联控制系统。仿真实验结果表明:与传统的PID控制方案相比,所提优化控制方案减小了供浆流量和出口SO_(2)浓度的波动,能够大幅度提升SD-WFGD系统的控制性能,从而更好地保证脱硫系统在燃煤电站灵活运行的背景下安全、稳定、经济及灵活运行。
