The atmospheric corrosion behavior of pure copper exposed for three years in Turpan, China, which is a typical hot and dry atmosphere environment, was investigated using mass-loss tests, morphology observations, com...The atmospheric corrosion behavior of pure copper exposed for three years in Turpan, China, which is a typical hot and dry atmosphere environment, was investigated using mass-loss tests, morphology observations, composition analyses, and electrochemical techniques. The results indicated that the annual corrosion rate of pure copper was approximately 2.90 μm/a. An uneven distribution of corrosion products was observed by scanning electron microscopy; this uneven distribution was attributed to the dehydration process during wet–dry and cold–hot cycles, and the compositions mainly consisted of cuprite （Cu2O） and atacamite （Cu2Cl（OH）3）. Electrochemical measurements showed that deposits on copper improved its resistance to corrosion and the protectiveness decreased with increasing temperature. On the other hand, results obtained using the scanning vibrating electrode technique showed that the porous and uneven structure of the deposit layer generated a spatial separation of cathodic and anodic reaction sites, which accelerated the corrosion process in wet and rainy weather.展开更多
A three dimensional nano-scale finite element model （FEM）, called the chemical bond element model, is proposed for the simulation of mechanical properties of single-walled carbon nanotubes （SWCNTs） based upon mole...A three dimensional nano-scale finite element model （FEM）, called the chemical bond element model, is proposed for the simulation of mechanical properties of single-walled carbon nanotubes （SWCNTs） based upon molecular mechanics method. Chemical bonds between carbon atoms are modeled by chemical bond elements. The constants of a sub-stiffness matrix are determined by using a linkage between molecular mechanics and continuum mechanics. In order to evaluate the correctness and performance of the proposed model, simulation was done to determine the influence of nanotube wall thickness, radius and length on the elastic modulus （Young＇s modulus and shear modulus） of SWCNTs. The simulation results show that the choice of wall thickness significantly affects the Young＇s modulus and shear modulus. The force field constants is also very important, because the elastic modulus is sensitive to force field constants and the elastic properties of SWCNT are related to the radii of the tubes. The contribution of length to elastic modulus is insignificant and can be ignored. In comparison with the Young＇s modulus and shear modulus reported in the literature, the presented results agree very well with the corresponding theoretical results and many experimental measurements. Furthermore, if the force constants are properly chosen, the present method could be conveniently used to predict the mechanical behavior of other single-walled nanotubes such as boron nitride nanotubes. The results demonstrate the value of the proposed model as a valuable tool in the study of mechanical behaviors of carbon nanotubes and in the analysis of nanotube-based equipments.展开更多
On the basis of a general model of fuel cells, the entropy production rates of a fuel cell system under different conditions are derived by using theories of electrochemistry and thermodynamics. In order to analyze th...On the basis of a general model of fuel cells, the entropy production rates of a fuel cell system under different conditions are derived by using theories of electrochemistry and thermodynamics. In order to analyze the influence of the irreversible losses existing in an actual fuel cell, the equivalent circuit of the fuel cell is introduced, so that the irreversible factor of the fuel cell may be determined directly as a function of the internal, leak and load resistances. Moreover, the maximum power output and efficiency of the fuel cell are calculated, the optimal operation of the fuel cell is discussed, and the matching condition of the load resistance is determined.展开更多
The electrochemical mechanism of anode oxidation of HCHO in electroless copper plating solution with N, N, N′, N′-tetrakis(2-hydroxypropyl)ethylenediamine (THPED) was investigated by measuring cyclic voltammetry cur...The electrochemical mechanism of anode oxidation of HCHO in electroless copper plating solution with N, N, N′, N′-tetrakis(2-hydroxypropyl)ethylenediamine (THPED) was investigated by measuring cyclic voltammetry curves and anodic polarization curves. Three different oxidation peaks occur at the potentials of -0.62 V (Peak 1), -0.40 V (Peak 2) and -0.17 V (Peak 3) in the anode oxidation process of THPED-containing solution. The reaction at Peak 1, a main oxidation reaction, is the irreversible reaction of adsorbed HCHO with hydrogen evolution. The reaction at Peak 2, a secondary oxidation reaction, is the quasi-reversible reaction of adsorbed HCHO without hydrogen evolution. The reaction at Peak 3 is the irreversible oxidation of anode copper. The current density of Peak 1 increases gradually, that of Peak 2 remains constant and that of Peak 3 decreases with the increase of HCHO concentration. The current density of Peak 3 increases with the increase of THPED concentration and the complexation of THPED promotes the dissolution of anode copper.展开更多
Bionics （the imitation or abstraction of the ＂inventions＂ of nature） and, to an even greater extent, syn- thetic biology, will be as relevant to engineering development and industry as the silicon chip was over th...Bionics （the imitation or abstraction of the ＂inventions＂ of nature） and, to an even greater extent, syn- thetic biology, will be as relevant to engineering development and industry as the silicon chip was over the last 50 years. Chemical industries already use so-called ＂white biotechnology＂ for new processes, new raw materials, and more sustainable use of resources. Synthetic biology is also used for the devel- opment of second-generation biofuels and for harvesting the sun＇s energy with the help of tailor-made microorganisms or biometrically designed catalysts. The market potential for bionics in medicine, en- gineering processes, and DNA storage is huge. ＂Moonshot＂ projects are already aggressively focusing on diseases and new materials, and a US-led competition is currently underway with the aim of creating a thousand new molecules. This article describes a timeline that starts with current projects and then moves on to code engineering projects and their implications, artificial DNA, signaling molecules, and biological circuitry. Beyond these projects, one of the next frontiers in bionics is the design of synthetic metabolisms that include artificial food chains and foods, and the bioengineering of raw materials; all of which will lead to new insights into biological principles. Bioengineering will be an innovation motor just as digitalization is today. This article discusses pertinent examples of bioengineering, particularly the use of alternative carbon-based biofuels and the techniques and perils of cell modification. Big data, analytics, and massive storage are important factors in this next frontier. Although synthetic biology will be as pervasive and transformative in the next 50 years as digitization and the Intemet are today, its ap- plications and impacts are still in nascent stages. This article provides a general taxonomy in which the development of bioengineering is classified in five stages （DNA analysis, bio-circuits, minimal genomes, protocells, xenobiology） from the familiar to the unknown, with implications for safety and security, in- dustrial development, and the development of bioengineering and biotechnology as an interdisciplinary field. Ethical issues and the importance of a public debate about the consequences of bionics and syn- thetic biology are discussed.展开更多
The electrochemical behavior of X70 pipeline steel in (0.5mol·L-1 Na2CO3+1 mol·L-1 NaHCO3) solution was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). X-ray photoel...The electrochemical behavior of X70 pipeline steel in (0.5mol·L-1 Na2CO3+1 mol·L-1 NaHCO3) solution was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to analyze the composition and microstructure of the surface film. The results showed that there were two anodic peaks at -600 mV and -350 mV. The surface film formed at -600 mV mainly consisted of ferrous carbonates and ferrous hydroxycarbonates. It had a small reaction resistance. It was metastable and possessed poor protective property. Numerous pits and microcracks existed on the film, which could be the active paths for the initiation of stress corrosion cracking. The surface film formed at -350 mV, mainly consisted of ferric oxides. It has high reaction resistance and offered good protection for the substrate.展开更多
基金Project(51222106)supported by the National Natural Science Foundation of ChinaProject(FRF-TP-14-011C1)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2014CB643300)supported by the National Basic Research Program of China
文摘The atmospheric corrosion behavior of pure copper exposed for three years in Turpan, China, which is a typical hot and dry atmosphere environment, was investigated using mass-loss tests, morphology observations, composition analyses, and electrochemical techniques. The results indicated that the annual corrosion rate of pure copper was approximately 2.90 μm/a. An uneven distribution of corrosion products was observed by scanning electron microscopy; this uneven distribution was attributed to the dehydration process during wet–dry and cold–hot cycles, and the compositions mainly consisted of cuprite （Cu2O） and atacamite （Cu2Cl（OH）3）. Electrochemical measurements showed that deposits on copper improved its resistance to corrosion and the protectiveness decreased with increasing temperature. On the other hand, results obtained using the scanning vibrating electrode technique showed that the porous and uneven structure of the deposit layer generated a spatial separation of cathodic and anodic reaction sites, which accelerated the corrosion process in wet and rainy weather.
文摘A three dimensional nano-scale finite element model （FEM）, called the chemical bond element model, is proposed for the simulation of mechanical properties of single-walled carbon nanotubes （SWCNTs） based upon molecular mechanics method. Chemical bonds between carbon atoms are modeled by chemical bond elements. The constants of a sub-stiffness matrix are determined by using a linkage between molecular mechanics and continuum mechanics. In order to evaluate the correctness and performance of the proposed model, simulation was done to determine the influence of nanotube wall thickness, radius and length on the elastic modulus （Young＇s modulus and shear modulus） of SWCNTs. The simulation results show that the choice of wall thickness significantly affects the Young＇s modulus and shear modulus. The force field constants is also very important, because the elastic modulus is sensitive to force field constants and the elastic properties of SWCNT are related to the radii of the tubes. The contribution of length to elastic modulus is insignificant and can be ignored. In comparison with the Young＇s modulus and shear modulus reported in the literature, the presented results agree very well with the corresponding theoretical results and many experimental measurements. Furthermore, if the force constants are properly chosen, the present method could be conveniently used to predict the mechanical behavior of other single-walled nanotubes such as boron nitride nanotubes. The results demonstrate the value of the proposed model as a valuable tool in the study of mechanical behaviors of carbon nanotubes and in the analysis of nanotube-based equipments.
文摘On the basis of a general model of fuel cells, the entropy production rates of a fuel cell system under different conditions are derived by using theories of electrochemistry and thermodynamics. In order to analyze the influence of the irreversible losses existing in an actual fuel cell, the equivalent circuit of the fuel cell is introduced, so that the irreversible factor of the fuel cell may be determined directly as a function of the internal, leak and load resistances. Moreover, the maximum power output and efficiency of the fuel cell are calculated, the optimal operation of the fuel cell is discussed, and the matching condition of the load resistance is determined.
基金Project(200501045) supported by Innovation Fund of Guangdong Province of China
文摘The electrochemical mechanism of anode oxidation of HCHO in electroless copper plating solution with N, N, N′, N′-tetrakis(2-hydroxypropyl)ethylenediamine (THPED) was investigated by measuring cyclic voltammetry curves and anodic polarization curves. Three different oxidation peaks occur at the potentials of -0.62 V (Peak 1), -0.40 V (Peak 2) and -0.17 V (Peak 3) in the anode oxidation process of THPED-containing solution. The reaction at Peak 1, a main oxidation reaction, is the irreversible reaction of adsorbed HCHO with hydrogen evolution. The reaction at Peak 2, a secondary oxidation reaction, is the quasi-reversible reaction of adsorbed HCHO without hydrogen evolution. The reaction at Peak 3 is the irreversible oxidation of anode copper. The current density of Peak 1 increases gradually, that of Peak 2 remains constant and that of Peak 3 decreases with the increase of HCHO concentration. The current density of Peak 3 increases with the increase of THPED concentration and the complexation of THPED promotes the dissolution of anode copper.
文摘Bionics （the imitation or abstraction of the ＂inventions＂ of nature） and, to an even greater extent, syn- thetic biology, will be as relevant to engineering development and industry as the silicon chip was over the last 50 years. Chemical industries already use so-called ＂white biotechnology＂ for new processes, new raw materials, and more sustainable use of resources. Synthetic biology is also used for the devel- opment of second-generation biofuels and for harvesting the sun＇s energy with the help of tailor-made microorganisms or biometrically designed catalysts. The market potential for bionics in medicine, en- gineering processes, and DNA storage is huge. ＂Moonshot＂ projects are already aggressively focusing on diseases and new materials, and a US-led competition is currently underway with the aim of creating a thousand new molecules. This article describes a timeline that starts with current projects and then moves on to code engineering projects and their implications, artificial DNA, signaling molecules, and biological circuitry. Beyond these projects, one of the next frontiers in bionics is the design of synthetic metabolisms that include artificial food chains and foods, and the bioengineering of raw materials; all of which will lead to new insights into biological principles. Bioengineering will be an innovation motor just as digitalization is today. This article discusses pertinent examples of bioengineering, particularly the use of alternative carbon-based biofuels and the techniques and perils of cell modification. Big data, analytics, and massive storage are important factors in this next frontier. Although synthetic biology will be as pervasive and transformative in the next 50 years as digitization and the Intemet are today, its ap- plications and impacts are still in nascent stages. This article provides a general taxonomy in which the development of bioengineering is classified in five stages （DNA analysis, bio-circuits, minimal genomes, protocells, xenobiology） from the familiar to the unknown, with implications for safety and security, in- dustrial development, and the development of bioengineering and biotechnology as an interdisciplinary field. Ethical issues and the importance of a public debate about the consequences of bionics and syn- thetic biology are discussed.
基金Supported by State Key Basic Research Plan (G19990650).
文摘The electrochemical behavior of X70 pipeline steel in (0.5mol·L-1 Na2CO3+1 mol·L-1 NaHCO3) solution was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to analyze the composition and microstructure of the surface film. The results showed that there were two anodic peaks at -600 mV and -350 mV. The surface film formed at -600 mV mainly consisted of ferrous carbonates and ferrous hydroxycarbonates. It had a small reaction resistance. It was metastable and possessed poor protective property. Numerous pits and microcracks existed on the film, which could be the active paths for the initiation of stress corrosion cracking. The surface film formed at -350 mV, mainly consisted of ferric oxides. It has high reaction resistance and offered good protection for the substrate.
