Key Engineering Materials Vols. 373-374

Abstract: Synchrotron radiation photoemission spectroscopy was used to study the initial growth of Er2O3 films on Si in O2 pressures of 7×10-6 Torr. An interface layer was observed at the initial growth of Er2O3 film on Si, which is supposed to be attributed to the effect of the Er atom catalytic oxidation effect. With the film growth process continued, oxygen deficient Er oxide will capture oxygen from the interface layer which is formed inevitably at the initial growth of Er2O3 film and thus reduce and even remove the interface layer if the condition of O2 pressure is a little insufficient at a high substrate temperature.

Abstract: In this work, surface modification of silk fibroin was conducted by grafting dimethylaminoethyl methacrylate (DMAEMA) via ATRP to produce well controlled grafting silk. First, the amino groups and hydroxyl groups on the side chains of the silk fibroin reacted with 2-bromoisobutyryl bromide (BriB-Br) to obtain efficient initiator for ATRP. Subsequently, the functional silk fibroin was used as macroinitiator of DMAEMA in 1,2-dichlorobenzene in conjunction with CuBr/N,N,N',N",N" -pentamethyldiethylenetriamine (PMDETA) as a catalyst system. FT-IR characterization of the modified silk substrate showed a peak corresponding to DMAEMA indicating that the polymer had been formed on the silk surface. Following the polymerization, the tertiary amino groups on the grafted silk fibroin were quaternized to produce a large concentration of quaternary ammonium groups, which endowed the silk substrate with potential antibacterial surface. The graft chains were cleaved by acid hydrolysis and analyzed by gel permeation chromatography (GPC). The GPC results indicated that the graft layer were well-controlled.

Abstract: Amphiphilic polysulfone-poly(ethylene oxide) block copolymers (PSF-b-PEOs) with different contents of PEO, have been successfully synthesized and employed as the drug carrier for use in drug-eluting stent (DES) systems. They are well soluble in organic solvents such as tetrahydrofuran (THF). Cell growth, hemolysis, cell hyperplasia, toxicity and sensitization tests revealed that PSF-b-PEOs have good biocompatibility. Silolimus was selected as the drug and the loading level was controlled at 10 or 20 wt%. PSF-b-PEO-coated stents were fabricated by the widely used ultrasonic spray coating technique. Pre- and post-expansion morphologies of the coatings were observed by optical microscopy (OM) and scanning electron microscopy (SEM). Under the optimal operation conditions, the stents have uniform and smooth coating surface. No cracks or peels were observed when the coating stents were expanded. No drug particles were observed on the stent surface. PEO content in PSF-b-PEOs greatly influences drug release rate, and the higher the PEO content, the faster the release rate. PSF-b-PEO film comprising 30% PEO displayed relatively reasonable drug release rate, i.e., about 80% silolimus were released from the film after release tests in phosphate buffer solutions (PH = 7.4) containing 10 v% ethanol at 37 °C for 24 days.

Abstract: MMCs wire can be produced by infiltration of molten metal into carbon fiber bundles. To protect the fibers from damage, the desized fibers must be pretreated before fabrication into wire. This paper deals with the formation of SiO2 coating on the carbon fibers using plasma chemical method and compares the coating produced by plasma method with the one by sol-gel method. The SiO2 coating produced by the sol-gel method on the carbon fibers is very rough. It is also discovered that the quality of the SiO2 coating is controlled by the power of plasma equipment and the flow rate of plasma gases. As the power of the plasma equipment and the flow rate of plasma gases increased, the coating surface became smoother.

Abstract: Under SOFCs operating condition, the cathode reaction rate is determined by triple phase boundary (TPB) areas which are associated with the geometry of the interface between the cathode and the electrolyte. In this paper, YSZ electrolyte was deposited by atmospheric plasma spraying (APS). A nano-scaled lanthanum strontium manganate (LSM) cathode was prepared by sol-gel process on APS YSZ with different surface roughness to aim at increasing the TPB. The polarization curves of LSM cathode were characterized by potentiostat. The influence of the roughness of APS YSZ on the polarization of LSM cathode was investigated. It was found that the overpotential of the LSM cathode is significantly reduced with the increase of YSZ surface roughness.

Abstract: The fourth generation of poly amide amine molecular self-assembled monolayer (PAMAM (G4.0)-SAM) was prepared on hydroxylated Si (111) substrate by a self-assembled technique from specially formulated solution. The PAMAM (G4.0)-SAM were characterized by means of contact angle measurement, ellipsometry, X-ray photoelectron spectroscope (XPS), and atomic force microscopy (AFM). The tribological properties of the as-prepared thin films sliding against a steel ball were evaluated on a friction and wear tester. The tribological results show that the friction coefficient of monocrystal line silicon substrate reduces from 0.6 to 0.18 due to the formation of PAMAM-SAMs on its surface. And the PAMAM (G4.0) -SAM has longer wear life (18000 sliding pass). It is demonstrated that PAMAM (G4.0) -SAM exhibited good wear resistant property. In conclusion, the PAMAM (G4.0)-SAM which possesses good wear resistant property was successfully prepared and the film.

Abstract: The Self-assembled monolayers (SAMs) of Schiff base had been formed on oxidized surfaces of copper. Schiff base used in this paper is N-2-hydroxyphenyl- (3-methoxy-salicylidenimine), designated V-bso. X-ray photoelectron spectroscopy (XPS), polarization curves, electrochemistry impedance spectroscopy (EIS) and the interface capacitance measurements have been employed to investigate the structure, formation and composition of these monolayers. XPS analysis show that the valence of the copper in the surface films is +2. The polarization curves and the EIS results indicate that the films of CuO, V-bso, and V-bso modified oxidized copper all have good corrosion inhibition efficiency. The IE of the V-bso modified oxidized copper is higher than that of the V-bso modified copper and the oxidized copper layer, just because the former has two layers. The results of the interface capacitance show that the self-assemble films of the V-bso on the oxidized copper surface have good potential stability.

Abstract: In this study, the surface modification and biocompatibility of the biologic chitosan scaffold were investigated. The chitosan scaffold with excellent reticular structure was attained after being purified, emulsionized, cross-linked, molded and freeze-dried step by step by using the native materials, coming from such as lobster shell, crab shell etc.. After that, its surface modification was operated with film coating by using gelatin. Then the bone marrow mesenchymal stem cells (BMSCs) derived from New Zealand rabbits were used as the seed cells and were inoculated onto the modified biologic chitosan scaffolds at 3×105 cells/ml to investigate the biocompatibility and bone conductive efficiency of this kind of scaffold in static culture for one week. As a control, the cell suspensions with same densities were inoculated onto the chitosan scaffold without being treated. During the whole culture process, the cellular adherence and expansion were observed under inverted microscope. After culture, the biological properties of the fabricated cell-scaffold tissues were detected by scanning electron microscope (SEM) and HO/PI fluorescent double staining. The results showed that the biologic chitosan scaffold treated with gelatin or rat-tail collagen promoted a higher adhesion and proliferation of BMSCs in comparison to the untreated samples. Besides, the BMSCs within the treated scaffold were more regular and well-distributed than those in untreated one. It is concluded that this kind of surface modification can be used to change the physicochemical properties of chitosan scaffold. The improved biologic chitosan scaffold is suitable to be an ideal biomedical scaffold for tissue engineering.

Abstract: Three copolymers containing isobutyl p-styrenesulfonate (IBSS) and carboxyl units, i.e. methyl methacrylate (MMA) and methacrylic acid (MAA), were synthesized and their chemical structures and thermal behaviors were investigated by using TGA, DSC, FTIR and other methods. Films were prepared by using the synthesized copolymers in combination with a bisvinyl ether compound, i.e. 2,2-bis(4-(2-(vinyloxy)ethoxy)phenyl)propane (BVPP), to applied onto an aluminum plate. Crosslinking and de-crosslinking reactions would readily take place when the polymer films were baking treated at 100 oC and 200 oC for a short period of time, respectively. Along with the chemical structural changes during thermal treatments, an affinity change was achieved from being insoluble to completely soluble in neutral water. A positive-working and neutral water-developable imaging material was proposed and preliminary studies on the imaging properties were conducted.

Abstract: A room temperature fast curing epoxy resin nano-adhesive was prepared and modified by nano-SiO2 and liquid rubber CTBN. It shows good shear strength value and heat-durability and also meets the conditions of room temperature and short solidified time. Compared with conventional resin mixing method, adhesive modified by nanomaterial can achieve better heat-durability. Compound cation/nonionic surfactants were used for modifying nano-SiO2 and solution mix method was used for preparation of nano-SiO2 epoxy resin adhesive. The effects of nano-SiO2 to adhesive’s mechanical property and heat-durability were investigated. Adhesive with 2wt% nano-SiO2 shows improved properties which shear strength value is 17.9 MPa and vitrification point is 216.5°C. Micropores and grains of nano-SiO2/liquid rubber CTBN modifying system were observed using scanning electron microscope. Adhesives were investigated using infrared spectroscopy analysis. Nano-SiO2 modified using compound surfactant has higher reacting activity and accelerates the reaction of adhesive. It can be used as catalyst.