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Text|a: A view of history
Editor|aHistorical view
Introduction:
Graphene polyaniline nanocomposites refer to a composite material prepared by mixing polyaniline with graphene nanosheets. Due to the high electrical conductivity, high mechanical strength and good acid and alkali resistance of polyaniline, graphene polyaniline nanocomposites have a wide range of application prospects in the field of anti-corrosion. However, how to accurately evaluate its anti-corrosion performance has become the focus and difficulty of research.
1. Quality loss method
The mass loss method is a common method to evaluate the corrosion resistance of materials. The specific operation is to measure the quality change of the material after the graphene polyaniline nanocomposite to be evaluated is in contact with the corrosive medium for a period of time. By comparing the quality difference before and after the composite, the corrosion resistance can be initially evaluated.
Overview of plasma surface modification techniques
Plasma surface modification is a commonly used method to improve the properties of plastic surfaces. Plasma is a highly excited gas in which the molecular density of electrons and ions, as well as excited states, is high. Treating plastic surfaces with plasma can trigger a series of chemical and physical reactions that alter the properties of plastic surfaces.
This technology has different application methods, including plasma spraying technology, plasma enhanced chemical vapor deposition technology and plasma polymerization modification technology.
Plasma spraying technology Plasma spraying technology is a method of spraying activated particles generated by plasma onto the surface of plastics through spraying equipment. Plasma spraying technology can modify the plastic surface by controlling the spraying atmosphere and parameters. During plasma spraying, activated particles react with the plastic surface, resulting in changes in surface chemistry, surface topography and surface energy.
Plasma-enhanced chemical vapor deposition technology Plasmon-enhanced chemical vapor deposition technology is a method that uses plasma to activate a reaction gas to form a layer of chemicals on the surface of plastics through a chemical reaction.
This technology enables precise control of the plastic surface by adjusting parameters such as atmosphere, temperature and deposition time. Through plasma-enhanced chemical vapor deposition technology, thin films of different materials can be formed on the surface of plastics, thereby changing the surface properties.
Plasma polymerization modification technology Plasma polymerization modification technology is a method of using plasma to activate monomer molecules to polymerize on the surface of plastics to form polymer layers. Through plasma polymerization modification technology, polymer layers with specific properties can be formed on the surface of plastics, such as hydrophilicity, wear resistance, chemical resistance, etc. This technology can achieve customized improvements to the surface properties of plastics by selecting different monomers and reaction conditions.
The main principle of plasma surface modification technology is to use plasma-activated substances to interact with the plastic surface to initiate a series of chemical and physical reactions to change the properties of the plastic surface. These changes can include changes in surface chemistry, enhancement of surface energy, regulation of surface roughness, etc. During plasma treatment, plasma-activated particles react with the plastic surface, resulting in the breaking and recombination of surface chemical bonds, or the removal and addition of surface adsorbates, thereby changing the composition and properties of the surface.
The advantage of plasma surface modification technology is its high degree of controllability and tunability. By adjusting the parameters of plasma treatment, such as plasma energy, atmosphere composition, treatment time, etc., precise regulation of the surface properties of plastics can be achieved. In addition, plasma surface modification technology is efficient, fast and environmentally friendly. =
Plasma surface modification technology has a wide application prospect in plastic surface improvement. Through plasma spraying technology, a film with good coverage and adjustable particle size can be formed on the surface of the plastic, improving its anti-corrosion performance, wear resistance and weather resistance. Plasma-enhanced chemical vapor deposition technology can deposit coatings with specific functions such as antimicrobial and chemical resistance on plastic surfaces. The plasma polymerization modification technology can realize the regulation of the hydrophilic, oily and antifouling properties of the plastic surface through the formation of polymer layers.
Plasma surface modification technology still faces some challenges. First of all, the parameter optimization of plasma treatment needs to be further studied in order to achieve optimal regulation of the surface properties of plastics. Secondly, the consistency and stability of the plasma treatment process are also problems that need to be solved. In addition, for different types of plastic materials, it is necessary to develop suitable plasma treatment methods and suitable plasma equipment.
2. Electrochemical impedance spectroscopy
First, the basic principle of electrochemical impedance spectroscopy
Electrochemical impedance spectroscopy is based on the kinetic process of electrochemical reactions and obtains information on charge transport and charge transfer by applying a small alternating current signal in an electrochemical system and measuring the response. In an electrochemical system, when an applied alternating current signal passes through the electrolyte solution, a phase difference, or impedance, occurs between the current and the voltage. The magnitude and phase difference of impedance change with frequency, forming an impedance spectrum of frequency response.
In electrochemical impedance spectroscopy, the commonly used electrochemical technique is alternating current analysis. By measuring the current and voltage response under an alternating current signal over the frequency range, the impedance spectrum of an electrochemical system can be obtained. The impedance spectrum is usually expressed in complex numbers, consisting of a real part (resistance) and a imaginary part (reactance). The real part represents the direct relationship between current and voltage, reflecting the charge transport process, while the imaginary part represents the phase difference, reflecting the kinetics of the electrochemical reaction.
Second, the measurement method of electrochemical impedance spectroscopy
Measurements by electrochemical impedance spectroscopy consist of two main steps: applying an alternating current signal and measuring the response. Common electrochemical impedance spectroscopy measurement devices are electrochemical workstations or impedance spectrometers. The following are typical measurement steps:
Set the measurement conditions: including frequency range, amplitude and type of AC signal, electrode area, electrolyte solution, etc.
Apply an alternating current signal: Depending on the selected frequency range and signal type, an alternating current signal is applied to an electrochemical system. Common signal types include sine waves, square waves, and multi-frequency sweeping signals.
Measurement response: Current and voltage responses are measured and recorded. Measurements are usually made using potential scanning or potentiostat methods. At each frequency point, the amplitude and phase difference of current and voltage are measured.
Obtaining the impedance spectrum: By calculating the ratio of current and voltage, the impedance value at each frequency point is obtained. The impedance spectrum can be represented in complex numbers and presented as amplitude-phase plots or real-imaginary plots.
Data processing and analysis: Data processing and analysis of measured impedance spectra to obtain information about the electrochemical system. Common analysis methods include equivalent circuit model fitting, Bode plot analysis, Nyquist plot analysis, and related electrochemical parameter calculation.
Third, the data analysis of electrochemical impedance spectroscopy
The impedance spectra measured by electrochemical impedance spectroscopy provide a wealth of information that can be used to study the properties of the electrochemical interface, charge transport mechanism, electrode reaction rate, etc. Common data analysis methods include:
Equivalent circuit model fitting: Fitting the actual impedance spectrum to the equivalent circuit model to extract the parameters of the electrochemical system. Commonly used equivalent circuit models include Randles equivalent circuits, Warburg components, and electric double-layer capacitance models.
Bode diagram analysis: By plotting Bode plots of amplitude-frequency characteristics and phase-frequency characteristics, the frequency response of electrochemical systems can be analyzed. The amplitude-frequency characteristics reflect the electrode reaction rate and charge transport process, and the phase-frequency characteristics reflect the interface reaction kinetics.
Nyquist plot analysis: By plotting a Nyquist plot, the interface properties and charge transport mechanisms of electrochemical systems can be analyzed. The Nyquist plot consists of real and imaginary parts, providing information such as interface impedance, charge transfer resistance, and interface capacitance.
Electrochemical parameter calculation: By calculating the impedance spectrum, some important electrochemical parameters can be obtained, such as charge transfer resistance, electric double layer capacitance, electrode reaction rate, etc.
Fourth, the application of electrochemical impedance spectroscopy
Electrochemical impedance spectroscopy has a wide range of applications in materials science and related fields. Here are some typical application examples:
Material surface modification: Electrochemical impedance spectroscopy can be used to evaluate the anti-corrosion performance, corrosion resistance and anti-fouling performance of the coating material. By analyzing impedance spectroscopy, it is possible to understand the interfacial properties and charge transport mechanisms between the coating and the substrate.
Battery research: Electrochemical impedance spectroscopy can be used to evaluate the performance and stability of batteries. By analyzing impedance spectroscopy, it is possible to understand the internal resistance of the battery, the charge transport at the electrode interface, and the ion transport of the electrolyte.
Corrosion studies: Electrochemical impedance spectroscopy can be used to evaluate the corrosion behavior and corrosion resistance of metallic materials. By measuring the impedance spectrum of the metal surface, it is possible to understand the kinetics of charge transport and corrosion reactions between the metal and the electrolyte.
Biosensors: Electrochemical impedance spectroscopy can be used for performance evaluation and detection of biomolecules. By measuring the impedance spectrum of the electrochemical interface, it is possible to understand the interaction and charge transport process of biomolecules with the sensor interface.
Catalyst research: Electrochemical impedance spectroscopy can be used to evaluate the activity and stability of catalysts. By measuring the impedance spectrum of the catalyst surface, the charge transport and reaction kinetics between the catalyst and the reactants can be understood.
3. Scanning electron microscopy (SEM) observation
Scanning electron microscopy is a commonly used characterization technique to observe the surface topography and microstructure of materials. Through SEM observation, possible defects, holes, corrosion products, etc. in the composite can be found to evaluate the corrosion resistance of the material.
X-ray diffraction (XRD) analysis
X-ray diffraction is a commonly used means of material characterization to study the crystal structure and phase of materials. XRD analysis can determine whether there are corrosion products or phase transitions in graphene polyaniline nanocomposites, and then evaluate their corrosion resistance.
Author's point of view
Graphene polyaniline nanocomposites have good anti-corrosion properties and can be evaluated by a variety of methods. The mass loss method can provide a preliminary assessment of the corrosion properties of the composite, the electrochemical impedance spectroscopy can provide more detailed electrochemical parameters, and the scanning electron microscope and X-ray diffraction analysis can further observe the microstructure and phase transition phenomena of the material. The comprehensive application of these evaluation methods can comprehensively and accurately evaluate the corrosion resistance of graphene polyaniline nanocomposites.
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- WANG Weiyan, CHEN Liming, XU Chen, et al. Preparation and Properties of Graphene Polyaniline Nanocomposites [J]. Chemical Engineer,2017,41(7):40-44.