The copolymers of 10% acrylic acid (AAc) and 90% acryl amide (AAm) were synthesized by free radical polymerization with 5% ethylene glycol dimethacrylate (EGDMA) as a crosslinker. The basic physical feature such as density, fixed charge density, average molecular weight, equilibrium water contentment and crosslink density were studied. In this investigation, the equilibrium and kinetic experiments were performed under three different ionic strengths, the equilibrium behavior of the hydrogels was characterized by varying the designed stimulus and by measuring the weight of hydrogel disc using a high accuracy balance. The ionic strength of the solution was adjusted with NaCl and the buffer solution was phosphoric acid. Potentiometric titration was performed to investigate the quantity of dissociated H+. Last, diffusion coefficients of aqueous sodium chloride in water swollen cross-linked poly (AAc-co-AAm) membranes were studied. A self-planned cell was used for the measurement of NaCl diffusion coefficients.
Tensile tests were conducted on poly (AAc-co-AAm) hydrogel sensitive to variations in environmental pH and ionic strength. Mechanical properties (Young’s modulus) were determined at different levels of swelling equilibrium. The results show that there are great shift in the modulus number between the swollen and unswollen states, corresponding to the maximum, the Young’s modulus data in the pH7 buffers is a decrease of 80%. The Poisson’s ratio of the samples tested in the pH2 with 1.0M ionic strength solution is nearly 0.5, which implying its incompressibility. Analyzing its inner structure, the reason may be the high polymer chains entangled highly, they can resist the deformation. The further investigations of SEM micrographs prove our suggestions about the microstructure change.
The polymer was prepared by the radical copolymerization. Tensile tests were conducted on a N-isopropylacrylamide (NIPA)-acrylamide (AAm) comonomer gel sensitive to variations in environmental temperature. and salinity Mechanical properties (Young’s modulus) were determined at different levels of swelling equilibrium. Shifts in the mechanical properties were observed between samples tested in the swollen and unswollen states. Additional tests were conducted to determine the effect of salinity on the LCST. Increasing the salinity from 0M to 1.0M resulted in a decrease in LCST (55centigrade to 28centigrade).It is found that adjustment of the salinity of the environment solution is an effective method of controlling the LCST of the gel. Keywords: Salinity, hydrogels, mechanical properties
Ni-based WC composite coatings conducted on the surface of 45 steels by free spraying followed with high frequency induction remelting were investigated. The influences of induction remelting time on properties of the coating were discussed. The wear resistance of the coating and the elemental diffusion cross the interface between the coatings and the substrate were analyzed. The compositions and microstructure of the coating before and after a wear test were characterized by scanning electron microscope with energy dispersive X-ray microanalysis. The results indicate that a coating which is free from crackers and pores composed of Ni-based solid solution and dispersed tungsten carbide is obtained by free spraying and induction remelting. The interface is a white lamellar zone. The mutual diffusion of iron and nickel in the interface proves it’s an atomic bonding between the substrate and the coating. The wear mechanisms of the coated sample are abrasive wear and microplowing. The wear resistance of Ni-based WC composite coatings is superior to that of quenched high carbon steels.
From the point of view of molecule design, pH/temperature responsive hydrogels were prepared based on the acrylic acid with the excellent pH sensitivity and N-isopropylacrylamide (NIPA) with the excellent temperature sensitivity by the traditional radical polymerization. Study focus on the swelling of the hydrogels, measurement of the swelling and deswelling under different ionic strength with various temperatures of the hydrogels were performed in our work. The results show that the ionic strength, the pH value and temperature are three key factors that affect the LCST of the hydrogel. In the same pH buffer solution, the swelling ratio decreases with temperature rises, and the ionic strength greatly affects the swelling of the pH temperature responsive hydrogel, the higher the ion concentration is, the lower the swelling ratio and the LCST are.
From the point of view of molecule design, a series of pH/electronic field responsive hydrogels were prepared based on the acrylic acid with the excellent pH and electronic field sensitivity. Studyed on the basic physical characteristic, like density, molecular weight, equilibrium water content, crosslink density and fixed charge density etc.discussed the effect mechanism and trends that ionic strength,pH value and electronic field to the swelling ratio of the hydrogels .
In order to improve corrosion resistance of widely used carbon steels, self-fusion Ni60 alloys coating was prepared by free-spraying and induction heating, taking 45 steel as substrate. The microstructure and corrosion resistance of the coating and the elements diffusion cross the interface between the coatings and the substrate were analyzed. The results indicate that Ni60 coating free from cracks is obtained by free spraying and induction heating. The microstructure of the Ni60 coated substrate consists of top surface, intermediate layer, dendritic crystal zone and lamellar zone from outside to inside. The corrosion resistance of Ni60 coatings is markedly superior to that of the substrate in acid and alkali solution, and surpasses stainless steel in reductive and alkali solutions
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