Papers by Keyword: Surface Modification

Abstract: Metal hydride (MH) alloy (MmNi_3.81Mn_0.41Al_0.19Co_0.76) is modified by the electroless nickel plating and used as the electroactive material of negative electrode in Ni/MH batteries. The effect of the concentrations of reductant (NaH₂PO₂×H₂O), complex agent (Na₃C₆H₅O₇×2H₂O), reaction time, and reaction temperature on the Ni loadings and the utilization of the modified MH are systematically studied. The experimental results reveal that the appropriate reaction time and temperature of electroless nickel plating are 30 min and 70 °C in this work. The loading amount of Ni-P on MH alloy is increased and decreased by increasing the concentration of reductant and complex agent, respectively. The steady utilization of unmodified MH alloy is 94.7±1.0 % in the forming process under the charge/discharge conditions of 0.2C charge to 160% SOC (state of charge) and 0.2C discharge to 0.95V. The utilization of MH alloys modified with conditions of [NaH₂PO₂×H₂O] = 40 g L^-1 and [Na₃C₆H₅O₇×2H₂O] = 20 g L^-1, T = 70 °C, t = 30 min and [MH] = 2g/100 ml, respectively, is improved to 101.9±0.3 %.

Abstract: Cornstalk fibers were modified with surface modification and the properties of cornstalk fiber/gypsum composites was studied. The results showed that mechanical properties of cornstalk fiber/gypsum composites were enhanced by adding unmodified cornstalk fibers, but composites waterproof performance was decreased greatly. Through surface modification on cornstalk fibers, composites mechanical properties were further enhanced, and composites waterproof performance was improved obviously. The mechanism of surface modification was discussed, and the model of interfacial zone between modified cornstalk fiber and gypsum matrix was proposed.

Abstract: In order to improve the hemocompatibility of polycarbonateurethane (PCU), the biomimetic phosphorylcholine (PC) group was introduced onto material surface. Brush structure having PC groups was formed by ultraviolet (UV) initiated polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) to improve the hydrophilicity and hemocompatibility of PCU surfaces. Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electrical microscopy (SEM) and water contact angle were used to characterize the chemical and physical properties of the modified PCU surfaces. Compared with original PCU, the PC-grafted PCU surfaces showed significantly high hydrophilicity as indicating by low water contact angle. The hemocompatibility of the PC-grafted PCU surfaces was evaluated by platelet adhesion test. The PCU surfaces modified with phosphorylcholine zwitterionic brushes showed effective resistance to platelet adhesion and high hemocompatibility. These PC-grafted PCU materials will have potential application as blood-contacting materials or devices due to their good mechanical and hemocompatible properties.

Abstract: Hemp fiber is an excellent sustainable and renewable alternative to glass fiber as a reinforcing component in composite system, owing to its unique features of fast growth, high mechanical strength, low density, low cost, biodegradable, and low energy consumption. In this study a systematic investigation of physical and chemical treatment on hemp fiber was conducted, and their effects on thermal stability of hemp fiber were analyzed. Oxygen plasma treatment was used as physical modification approach, 5 wt% sodium hydroxide solution was used for chemical modification. Surface chemical composition and thermal stability were characterized by Fourier transform infrared spectroscopy and thermo gravimetric analysis. The results indicated that 5 wt% of NaOH with 16 hours treatment time increased hemp fiber thermal stability, while the plasma treatment had no impact on thermal stability of hemp fiber.

Abstract: Silica alcogels were prepared by hydrolysis with hydrochloric acid and condensation with NH₄OH of ethanol diluted tetraethylorthosilicate (TEOS) precursor and trimethylchlorosilane and hexane as surface modifying agent. The physical properties such as density, appearance, hydrophobicity, surface area, pore size distribution and thermal stability were measured. It was found that the physical and hydrophobic properties of the silica aerogels depend on the TMCS/hexane (V) volume ratio. The density decreased with increase of V, and the aerogels are more hydrophobic as V=3%. The aerogels were thermally stable up to a temperature of 350 °C, and the aerogel prepared has a high surface area and large pore volume.

Abstract: In this paper, porous NiTi alloy prepared by powder metallurgy method was oxidized at high temperature. The effect of oxidation temperature and time on quality of oxidation layer of porous NiTi was studied. The component and morphology of oxidation layer before and after oxidation at high temperature were analyzed by XPS and SEM. The behavior of Ni ion release of porous NiTi alloy was observed. The results showed uniform and thick oxidation layer was formed on the surface of porous NiTi alloy after oxidation at 550°C for 1h. XPS analysis showed the oxidation layer mainly composed of TiO₂, and the thickness of the film was about 180nm higher than that before oxidation. The research on the behavior of Ni ion release showed the Ni release after oxidation can be significantly reduced at simulated body fluid due to TiO₂ layer.

Abstract: The surface modification of the tourmaline powder with lauroyl chloride was studied in this paper, and discussed the influence of reaction conditions on modified effect with parameters of activation index and contact angle. Results showed that the activation index of modified tourmaline powder reached to 96% while tourmaline powder reacted with equiponderant lauroyl chloride at 80 °C in DMF for 5 hours, and the modified tourmaline had excellent hydrophobic property. Structural analysis revealed that hydrophobic alkyl was attached to the surface of tourmaline powder, but it had no effect on the crystal configuration of tourmaline powder.

Abstract: In this article,we report the results obtained from a study adopting solution of sodium naphthalene complex to modify the poly(chloro-p-xylylene)(parylene C) thin film.In this work,the function group and the crystal structure of the film before and after modifying are characterized separately with Attenuated Total Reflection Fourier transformation infrared spectroscopy(ATR- FTIR)and X-ray diffraction(XRD).The result of test shows that the bond of carbon(C) and chlorine(Cl) is damaged;The crystalline of the film reduces,and the NaCl crystal exist on the film surface.The surface energy of the film is increased from 28.64mJ/m² to 41.48mJ/m².The generalized analysis result indicated that nucleophilic reagent destructs the C-Cl bond on the benzene ring, the chlorine(Cl) atom on the benzene ring and the sodium ion in modified reagent forms the sodium chloride which adheres to the film surface.

Abstract: Ground calcium carbonate (GCC) is usually of smooth/flat surface and pointed edges angles which have disadvantageous effects on the mechanical properties of composite polymer materials filled with the powder. Nanometer calcium carbonate reactants would deposit, nucleate and grow on surface of ground calcium carbonate with micron grain size by adjusting suitable technical parameters in Ca(OH)₂–H₂O–CO₂ system. Compared with the uncoated powder, composite ground calcium carbonate (CGCC) is of rough surface, blunt edges, larger specific surface area, larger in whiteness. In this paper, we reported the successful preparation of CGCC particles, and found GCC/Ca(OH)₂ weight ratio was the key parameter. Some technological parameters were mainly analyzed for the coating process. Furthermore, We also prepared nanosized calcium carbonate coating GCC at higher temperature (40 °C) using additives. Filling tests showed that a rough surface of the CGCC enhanced contact opportunities and improved the interface between polymer and CGCC blended with polypropylene (PP).

Abstract: One of the main hurdles for the wide use of current Ag-filled conductive composites is the high cost of Ag fillers, while the challenge for low cost copper-filled composites is their poor reliability. In this study, the Ag-coated Cu flakes was chosen as conductive fillers and a surface modification with coupling agent, to achieve good bonding between the flakes and the Polydimethylsiloxane (PDMS) matrix, was applied to improve the mechanical and conductive properties of the PDMS based composites. The resulting composites obtained through modification showed an increase in hardness by 13.1% and tensile strength by 28.4% relative to the composites without coupling agent. In addition, the reliability of conducting composites was discussed and the results showed that the coupling agent played a great role in preventing the corrosion of the exposed Cu during aging. The volume resistivity of the composites, filled with untreated Ag-coated Cu flakes, increased from 0.0039Ω·cm to 0.0059Ω·cm under aging at 85°C and 85% room humidity (RH) in a temperature/humidity chamber for 48 h, in contrary, the volume resistivity shift of the composites with treated flakes was almost negligible, just changed from 0.0043Ω·cm to 0.0045Ω·cm. More importantly, the prepared conductive silicone rubber filled with Ag-coated Cu flakes with the resistivity (0.004Ω·cm) comparable to the relative commercial products can be used for electro-magnetic interference (EMI).