Papers by Keyword: Mechanism

Abstract: Carbon dioxide (CO₂) capture is a significant chemical process that has attracted considerable interest in both academic and industrial sectors. It is essential for mitigating climate change and its related impacts on the environment and human health. Various technologies are implemented for CO₂ capture, with physical adsorption using porous material standing out as one of the most widely employed methods. Gallate-based metal-organic frameworks (MOFs) are reported to offer remarkable CO₂ adsorption capacity values, with Mg-gallate exhibiting the highest capacity, followed by Co-gallate and Ni-gallate. The mechanism of CO₂ adsorption on gallate-based MOFs, however, lacks extensive discussion. A thorough understanding of the adsorption mechanism helps in designing and synthesizing MOFs with enhanced CO₂ capture performance. Therefore, this work aims to discuss the mechanism of CO₂ adsorption on gallate-based MOFs based on the experimental pure isotherms. The experimental isotherms exhibited S-shaped curves that are related to the occurrence of gate-opening effect. These S-shaped isotherms corresponded to multistep adsorption, classifying gallate-based MOFs as flexible MOFs. The flexibility of these frameworks can be controlled by the pressure and temperature, which is important for designing specific gas storage and separation systems. In addition, the intra-particle diffusion model supported that the CO₂ adsorption occurred at the surface and mesopore of gallate-based MOFs. Given these characteristics, gallate-based MOFs can be considered as the promising physisorbent for CO₂ capture.

Abstract: In this paper, the alkali sulfadiazine neodymium (NdSD) was prepared from sulfadiazine and neodymium nitrate hexahydrate under alkaline conditions, and used as a heat stabilizer on PVC. The structure of NdSD was characterized by elemental analysis and infrared spectrum. The results show that the molecular formula of NdSD is Nd (SD)₂·OH·H₂O. The thermal degradation process of NdSD at 25-800°C was characterized by thermogravimetric analysis. The results show that the decomposition temperature of NdSD is higher than 200°C, which is suitable for PVC thermal stabilizer. The thermal stabilizer time of PVC by NdSD was characterized by static Congo red method. The results showed that the thermal stabilizer time of PVC increased from 2.7min to 23.2 min after adding NdSD. The discoloration effect of NdSD on PVC was characterized by oven discoloration method. The results indicate that PVC samples added with NdSD show better effect than other heat stabilizers. By means of silver nitrate solution method and Fourier transform infrared spectroscopy, it was proved that sulfadiazine neodymium can absorb and react with HCl, and further proposed a possible mechanism of NdSD stabilization of PVC.

Abstract: In recent years, the frequent use of antibiotics has led to the continuous release of antibiotics into the water environment, which not only poses a potential threat to public health, but also contributes to the generation and spread of antibiotic resistance. In addition, due to the high environmental persistence and low biodegradability of antibiotics, it is difficult to be effectively degraded by traditional water treatment processes. Therefore, it is urgent to develop clean and efficient treatment technologies. Advanced oxidation processes (AOPs), which can effectively remove refractory organic pollutants from water, has become a promising water treatment technology. In this regard, persulfate (PS)-based AOPs (PS-AOPs) has attracted extensive attention of researchers. In this system, PS can be activated by energy and catalysts to produce highly oxidizing active species, and achieve efficient degradation of antibiotics. Due to its rich surface functional groups, high specific surface area and high adsorption properties, researches on the activation of PS by carbonaceous materials have been reported continuously. In this paper, the research progress of carbon nanotubes, graphene, biological carbon, active carbon and hetero-atom doped carbon materials as catalysts to activate PS and degrade antibiotics is reviewed. In addition, the structure and properties of different carbon materials and the activation mechanism of free radical and non-free radical mediated by carbon materials were introduced, and the effects of PS dosage, catalyst dosage, temperature and pH on the degradation of antibiotics were discussed. Finally, this paper points out the important development direction in the future, that is, the development of environmental protection, high efficiency, low cost carbon materials and further research on the actual wastewater treatment performance.

Abstract: From the microscopic point of view, combining experiment with simulation, the thermal decomposition mechanism of solid propellant was discussed. At first, the thermo gravimetric curves of HTPB film and propellant were studied based on DSC-TG thermal analysis experiment technology. The thermal decomposition process of propellant was simulated by establishing the physical model of meso-structure cell. The results show that the simulation is consistent with the experimental trend. The above research is helpful to further understand the thermal decomposition mechanism of propellant.

Abstract: The work aim to the reaction mechanism of laser engraving polycarbonate (PC)-based films. The calculation of infrared-laser acting on the PC films, was carried out by using one-dimensional heat conduction model. The power density of laser device required for laser engraving polycarbonate-based films was determined to be 4.86~7.73×10⁴ W/cm². Characterized by the FTIR spectra, SEM, DSC and TGA, the reaction mechanism was studied. The results show that the light-sensitive particles in the PC films absorb the laser energy with wavelength of 1064nm. After reaching the temperature of 509°C, the main chain of PC molecule opened due to the breakage of C-O bond in PC molecular terminal group and C-O bond between PC monomers. As the energy continues to be absorbed, the temperature reach to 610°C, the decomposition products decomposed into carbon black, which can form a black carbon spot.

Abstract: The use of tungsten dioxide as a filler for a non-polar polymer matrix is limited due to its high hydrophilicity and abrasiveness, which degrades the properties of the filled polymers. The paper presents the results of studies on the surface modification of tungsten oxide with organosilicon polyethylsiloxane. The mechanisms for modifying the surface of tungsten dioxide, based on the fixation of the modifier under the action of intermolecular forces of attraction and interaction of the hydroxyl groups of the oxide surface with the reactive bonds of the Si-H oligomer, have been established. To create additional active centers in the form of groups (–OH) on the surface of tungsten dioxide, it was boiled, which contributes to the forced hydroxylation of the surface. The adsorption of polyethylsiloxane with powdered tungsten dioxide from n-hexane solution was investigated. The results on determination of the wetting angle of unmodified and modified tungsten dioxide powder are presented. It has been established that modification with polyethylsiloxane leads to an increase in the wetting angle of tungsten dioxide to 121o, which indicates its hydrophobic properties.

Abstract: This paper summarizes the use of antibiotics and the current situation of bacterial resistance and explores the specific causes of bacterial resistance. Several commonly used and emerging detection techniques are described and compared. Finally, several measures and methods to reduce bacterial resistance are proposed.

Abstract: Tubing corrosion is a difficult problem in oilfield production. In order to explore the main factors influencing the tubing corrosion, this study first select some region of northern shaanxi 28 Wells, spent nearly 2 years of tubing corrosion weightlessness method of monitoring and analysis of physical and chemical properties of produced fluid to conduct a comprehensive system, then SPSS program is used to analyze the 11 influence factors such as temperature, moisture content, pH and the correlation of corrosion, at the same time in order to verify the accuracy of the statistical analysis of the results, the spot corrosion coupon for scanning electron microscopy (SEM) and energy spectrum analysis. The results show that the water content, chloride ion and sulfide of the produced fluid are relatively high, and the water quality is alkaline. Through grey correlation calculation, the correlation degree with corrosion rate is 0.8386, 0.8281 and 0.8281, respectively. The results of scanning electron microscopy and energy spectrum analysis are basically consistent with the statistical analysis, indicating that the property of produced fluid can be used to predict the corrosion status of tubing.

Abstract: To further study the formation and corrosion mechanisms of AM60B vanadate films, a vanadate coating was synthesized on AM60B substrate via a chemical conversion at 50°C. The morphologies of the films and the corrosion samples were observed by using scanning electron microscopy(SEM), energy dispersive X-ray analysis(EDAX) was used to analyze the elemental distribution of the film surface and the Electrochemical Impedance Spectroscopy(EIS) and the polarization curves of the films were tested by an electrochemical workstation. The morphology of conversion film is layered structure with white balls. V element preferentially deposits near the base end and the V-rich phase is easily generated on the β-phase(Mg₁₇Al₁₂). In the course of corrosion, corrosion begins near the α-phase(Mg). During the processes of observation and analysis, the concept of micro-zone pH gradients was discovered and applied, and attempts were made to explain some observed phenomena by using this concept. The results show that the concept of pH gradients in micro zones can be used to explain the film formation and corrosion mechanisms well.

Abstract: In order to improve the dimensional stability of cement based materials, the effects of shrinkage reducing admixture (SRA) dosage on the shrinkage and crack properties of cement based materials were investigated. The hydration process of the cement pastes was tracked and monitored by hydration calorimeter and adiabatic temperature rise apparatus respectively. The action mechanism of SRA on hydration process of the cement based materials was characterized by differential scanning calorimeter (DSC). The shrinkage and crack results show that the ability of resist cracking of concrete can be effectively improved by SRA. The results of hydration calorimeter and adiabatic temperature rise indicate that the appear time of hydration temperature peak at early age was delayed and the development of hydration heat changed gently at later period by doped SRA. The results of DSC show that the release amount of hydration heat and the production of early calcium hydroxide can be delayed by SRA, however, there has no effects of SRA on the formation of cement hydration products like calcium hydroxide at the later period.