Papers by Keyword: Surface Modification

Abstract: Yttria stabilized tetragonal zirconia (Y_0.08Zr_0.94O₂, YSZ) nanopowders were successfully synthesized by microwave solvothermal method (MSM). The synthesizing temperature, holding time and mineralizer concentration were optimized. The crystallization and particle distribution of as-prepared YSZ nanopowders were identified by DSC/TG, XRD, FESEM, TEM, FTIR, DLS, and BET. The dispersion of YSZ nanopowders dried by different methods and modified by polyethyleneimine (PEI) was analyzed and discussed. The results show that the PEI modified samples have the best dispersion, and the dispersion of freeze-dried samples is better than that of traditional dried ones. The particle size of the PEI modified samples calculated from the surface area determined by BET is 15.7 nm, which is consistent with that determined by TEM (16.5 nm), but slightly smaller than that calculated by the Scherrer formula according to XRD (22.3 nm). This may be attributed to the different testing principles in these methods.

Abstract: Membrane distillation (MD) is a thermally driven membrane separation process. In recent years, MD is considered as a key technology for desalination applications. It has been proven that it has numerous advantages compared to other desalination processes such as reverse osmosis. The thermal driving force, no osmotic pressure effect on membrane fluxes are among the advantages of this MD process. Membranes fabricated from hydrophobic polymers such as polyvinylidene fluoride (PVDF) can be a great choice for MD for the desalination process. However, MD membranes are still held back by some problems, most notably due to pore wetting effects, thereby limiting their use in treating seawater for desalination propose. This study proposes the use of carboxylic acid to modify the PVDF membrane to increase its hydrophobicity as a solution to avoid wetting in MD for water desalination. As a first step, membrane produced using PVDF pellets under the phase inversion method. Then the membrane underwent modification using 5wt%, 10wt% and 15wt% of formic acid via immersion technique. The characteristics of membrane produced observed by the contact angle, Fourier-transform infrared spectroscopy (FTIR) and membrane performance test. The impact of the concentration of formic acid solution and feed temperature on the membrane was evaluated. The result showed that by modifying the membrane with formic acid resulted in the increase in contact angle from unmodified PVDF membrane, 83.03° to 100.88° when the membrane modified with formic acid with concentration was 10 wt%. It was subsequently shown through FTIR peaks that formic acid successfully modified the PVDF membranes. Highest salt rejection percentage was also obtained with 68.9% when the feed temperature is 60 °C.

Abstract: The work is devoted to the basics of surface modification of structural materials for the effective protection of machine parts and mechanisms operated in extreme conditions from the mechanical impact of aggressive media, by the method of plasma-chemical exposure to concentrated streams of matter and energy by means of plasma generators, which allow for surface renovation and engineering.

Abstract: This paper studied the alternative method for determination of percentage of grafted content in the grafted low density polyethylene (LDPE) film with black seed oil (BSO). BSO was grafted onto LDPE by pre-irradiation grafting method and the grafted samples were evaluated using FTIR qualitative and quantitative analysis. The grafting yield was calculated quantitatively from absorbance peak of two difference peak (1464cm^-1 and 1746cm^-1). Control LDPE film shows no absorbance peak at wavenumber of 1746cm^-1 while, a peak appears for grafted film at the same wavenumber. Therefore, it is possible to consider the peak area in this wavenumber as the grafting extension of BSO in LDPE film. Meanwhile, concerning the infrared (IR) fingerprint of LDPE film, consistent peak characteristic bands of LDPE are also present for all grafted sample at 1464cm^-1. Thus, the grafting yield is computed by using these peaks. Then, further confirmation grafting of BSO onto LDPE film was supported by the XPS spectroscopy. The atomic composition of C decreased 13% after LDPE film was grafted with BSO. While, the O content increases from values of 6.9% to 19.2% after grafting reaction. The increment percentage of O1s after grafting reaction mainly caused by the incorporation of oxygen content of a new polar functional groups of BSO on the surface of LDPE films. These results are in good agreement with FTIR analysis.

Abstract: Surface modification with plasma has been widely applied to polymeric materials. This treatment is intended to improve the surface properties of the polymer including its wettability and adhesiveness. The aim of this paper is to provide a review of the literature on the surface treatment of polymers with plasma, which focuses on the effects of adhesive and surface tribology properties. The related surface properties are also reviewed in order to strengthen the review of adhesive properties and tribology. Various types of plasma treatments that have been reviewed reported that plasma can be effectively used to improve surface properties, especially adhesive and tribological properties. On a small surface treatment has been developed plasma jet treatment which has been widely applied in biomedical applications.

Abstract: Ongoing studies show that an effective demand for using natural fibers as a substitution of an artificial fiber in fiber-reinforced composites formation has increased their applicability in an industrial area worldwide. The hydrophobic nature of natural fiber makes week adhesion among the cellulose fiber and matrix components; these problems are usually encountered in fiber-reinforced composites production. To overcome such a limitation of a cellulose fiber, specific physical and chemical treatment strategies were advised by researchers around the world for surface modification of natural cellulose fibers. One of the most basic and efficient surface modification approaches adopted today by the researchers was alkali treatment, widely used in natural fiber composites formation. This technique effectively improved the Mechanical property of natural cellulose fiber, such as tensile strength and flexural properties, while the impact strength result was reduced.

Abstract: The paper considers the applications of foamed glassy phosphate materials as carriers of biologically active substances. One of the advantages of phosphate materials is their ability to effectively support the life of microorganisms. This feature of phosphate glassy materials opens up the prospects for the application of microorganism strains - destructors of oil products to their foamed samples, that is, the creation of biosorbents for purification of water and soil from hydrocarbon contamination. The advantages of a biosorbent are explained by the high biological activity of microorganisms on the surface of foamed glassy phosphates and the possibility of active development of microorganisms with the simultaneous destruction of petrochemical contaminants. The use of biosorbent eliminates the problem of its utilization and regeneration, thus it is suitable for repeated use. The formation of porous glassy phosphate materials on the surface by the method of molecular layering of monolayer coatings allows obtaining chemically modified composite materials, which improves their performance characteristics such as strengthening the material structure with a simultaneous increase in the catalytic activity of biochemical processes.

Abstract: The article discusses the possibility of using pulsed laser ablation of nanosecond duration to modify the surface of a cutting tool after regrinding and restoration. Experimental studies of the resistance characteristics of cutting tools with modified surfaces via laser ablation in air and in liquid have been carried out. It was found that after modifying the surface of cutting plates via laser ablation in air, the wear on the trailing surface of the cutting tool at a processing speed of V = 50 m/min is 8 times less than that of the untreated one, the build-up is 20 times less. The wear of the trailing surface of the plates at V = 70 m/min is 2 times less than that of the untreated sample. The resistance studies show surface modification of the cutting tool increases the tool life of the remanufactured tool, overall tool life and savings in tool costs.

Abstract: This article discusses the possibility of the fabrication of a highly sensitive sensor based on single-walled boron-carbon BC₅ nanotubes surface modified with functional carboxyl groups (-COOH). The sensor potential for detection of alkali (lithium, potassium, and sodium) metals were investigated. The results of computer simulation of the interaction process between the sensor and an arbitrary surface of the modified tube containing atoms of the studied metals are presented. The carboxylated BC₅ nanotube and a similarly modified BC₃ nanotube was compared. The effect of boron atoms on sensory properties of the obtained system is concluded. The calculations were carried out within the framework of the density functional theory (DFT) method using the molecular cluster model. It has been proved that surface-modified boron-carbon nanotubes by carboxyl group show high sensitivity for the metal atoms under study and can be used as the sensor device.

Abstract: The threshold of optical breakdown of the nickel alloy ChS57 (Inconel) was measured at a wavelength of 0.355 μm with a laser pulse duration of 10 ns. Heat treatment of ChS57 above pulse energy density threshold (1 - 2.5 J/cm²) occurred mainly in the ablative mode with almost no melting. The elemental composition of the surface layer did not change at an irradiation in a fixed spot. When a laser beam moves along the surface of the sample at a speed of 1 mm / s and at pulse energy density of about 0.02 J/cm², oxygen was detected in the elemental composition (3 – 4 wt. %). However, the proportions of the elemental composition of the alloy remained virtually unchanged. Heat treatment under threshold at pulse energy density ≥ 0.25 J/cm² revealed a rise of the surface layer with traces of high-temperature plastic deformation in the form of slippage on grain boundaries and crystallographic slip.