Advanced Materials Research Vols. 690-693

Abstract: In this work, a solar flat-plate collector test system is developed. The solar flat-plate collectors with anodic coating, chromium coating and blue core coating are tested. The experimental results indicate that the relative absorption ration α/ε of blue core coating is up to 19. The efficiency of collector with blue core coating is 78.66%, which is 5% higher than collectors with the other two types of coatings. In addition, collector with blue core coating has smaller total thermal loss coefficient. The blue core coating can effectively improve the performance of solar flat-plate collectors.

Abstract: Many surface protection methods have been developed to apply to constructional steels to be used under severe corrosive environments. Thermal spray coating has been known to be an attractive technique due to its relatively high coating speed. However, the high corrosion resistance of coating films deposited by thermal spray method is increasingly required to expand its application. Four types of coated films (DFT: 200um), that is, pure zinc, pure aluminum, and two Al-Zn alloy (Al:Zn=85:15 and Al:Zn=95:5), were coated onto carbon steel (SS401) with arc spraying, and the corrosion behavior of their samples were evaluated by the electrochemical method in this study. The pure aluminum sample had the best corrosion resistance when exposed to seawater solution and alloy (Al:Zn=85:15), so called galvalume and alloy (Al:Zn=95:5) samples followed the pure aluminum sample. The pure zinc sample ranked 4^th in corrosion resistance in this study. Morphology of corroded surfaces of pure aluminum and alloy (Al:Zn=85:15) samples exhibited a general corrosion pattern, however, the patterns of intergranular and pitting corrosion were observed for the pure zinc and alloy (Al:Zn=95:5) samples respectively. Pure zinc sample had the smallest value of porosity ratio compared to other samples due to its heavier density. Keywords : Surface protection methods, Thermal spray, Corrosion resistance, Pure aluminum, Pure zinc, Porosity ratio

Abstract: The mechanical properties of 1Cr11Ni2W2MoV stainless steel after laser peening (LP) and ultrasonic shot peening (USP) were examined and compared. The stainless steel specimens were treated with the two different surface processing techniques. X-ray diffractometry (XRD), scanning electron microscope (SEM), microhardness tester were used to investigate microstructure and mechanical properties. Vibration fatigue tests of untreated, LPed and USPed samples were also conducted. The results indicated that LP treatment can improved the fatigue life of 1Cr11Ni2W2MoV stainless steel more effectively. The increases of the compressive residual stress depth and microhardness in surface layer after LP were greater than that of USP. The SEM studies showed that USP treatment had an advantage in microstructure refinement. The compressive residual stresses make great contributions to the superiority of LP in the improvement of fatigue life of 1Cr11Ni2W2MoV stainless steel to USP.

Abstract: A simple and effective surface coating technique, electro spark deposition (ESD), has been used to produce WC coatings onto H13 steel surface. Influence of process parameter (output voltage, output capacitance, discharge frequency, specific deposition time at el) on the coating thickness was studied. It can be seen, choose output voltage 80V, output capacitance180 μF, discharge frequency 2000 Hz, specific deposition time 8min/cm² obtained to optimal overall quality of coating. The morphology and microstructure of coatings were analyzed using scanning electron microscopy (SEM). The WC coating had an average thickness of about 60 μm and formed metallurgical bonding with the substrate.

Abstract: This study investigated the effects of carrier gases (He and N₂) on the microstructure and properties of Ti coating layers to manufacture high-density Ti layers using the cold spraying. Cold spray coating layers manufactured using He had denser and more homogenous microstructures than those produced using N₂. Layers manufactured using He gas showed porosity of 0.02% and hardness of 229HV, which are better properties than the porosity (0.4%) and hardness (177HV) of N₂ coating layers. The bond strength of coating layers manufactured using He recorded higher value of 74.28MPa than that manufactured using N₂. This could be attributed to the fact that, when coating layers are manufactured using He gas, the powder can be easily deposited because of its high particle impact energy, facilitating the plastic deformation of the particles.

Abstract: As relatively new structure materials, magnesium and its alloys demonstrated significant potential for applications in many industries. However, magnesium alloys were easy to be corroded which greatly limited their development. AZ31B and AZ91D, two widely used commercial magnesium alloys in various industries, were chosen to be produced nanostructure on the surface layer, called Surface Nanocrystallization (SNC) by High Energy Spot Peening (HESP). The microstructure was characterized by Scan Electronic Microscopy (SEM) and X-ray diffraction (XRD) in this paper. Microhardness and corrosion resistance were measured by microhardness tester and electrochemical measurement system respectively. Experimental results showed that after HESP the grain sizes in the surface layer were obviously reduced into nanoscale; microhardness was greatly increased in the treated surface, about two times as much as that of original and corrosion current density in polarization curve was evidently raised while corrosion potential changed little.

Abstract: The wettability between molten impregnating materials and thermal spray coatings is an important factor in post-treatment process of porous coatings. Here, we present the study of wetting behavior of stainless steel substrates by multi-component oxides, using the sessile drop method. The multi-component oxides was mainly composed by SiO₂ and Al₂O₃ and also with a little K₂O, Na₂O etc. At 1273K and 1353K, we found that the contact angles stabilized at around 45° and 75° respectively. The micro-observation confirmed that the evaporation of alkali metal oxides become a leading position in molten multi-component oxides evaporation at 1353K. As a result, the rupture of NaO and KO bonds will occur and lattice network structure of multi-component oxides reconstruct at excessively high temperature, leading the molten oxides to a higher viscosity and poorer wettability. As the basic researches, this paper also provide a theoretical basis for the deeply study on the post penetration treatment.

Abstract: For the development of colon delivery systems (CDS) formulations have to be gastric resistant. The advantage of the CDS is the ability for a local treatment for colon diseases but also its systemic action. CDS can also increase the bioavailability of poorly water soluble drugs e.g. resveratrol, which can be degraded in the upper gastrointestinal tract or by the First-Pass-Effect. In this project the coating technique with different polymer mixtures containing Kollicoat MAE-30DP, Eudragit-NM, Eudragit-L, and Eudragit-NE was investigated. Resveratrol was used as a model drug and all formulations were coated with a polymer mixture in a small scale fluidized bed apparatus. Morphology, roughness and film thickness of the coated tablets were determined by a scanning electron microscope and a 3D light microscope. Drug amount was determined by UV-spectrometry. Release studies were performed in a dissolution apparatus type II. Kinetic profiles of drug release were demonstrated. Results exhibit the advantages of polymer mixtures for CDS in comparison with results of pure Kollicoat MAE-30DP which were published in one of our latest publications.

Abstract: Al₂O₃ ceramic coating was successfully prepared on GH132 super alloy by cathodic plasma electrolytic oxidation in (NO₃)_3·9H₂O electrolyte. The structure and chemical composition of the coatings were characterized. The results showed that the as prepared coating was composed of Al₂O₃ crystal, including much α-Al₂O₃ and some γ-Al₂O₃ two types of Al₂O_3. A few Fe elements entered into in the substrate and nearly no other elements were found in the coating surface. The Al₂O_3. coating showed coarse surface and there were some small pits on the surface. The diameters of pits were not more than 20 um. The thickness of coating was about 50μm.

Abstract: Plasma surface hardening process was performed to improve the surface on the 22SiMn2TiB steel by plasma transferred arc. Experiments were carried out to characterize the hardening qualities. The anti-penetration ability and mechanism were analyzed, and hardness protective layer can improve greatly the ability of armor protection. The dual hardness armor steel composed of high hardness panel and basic backplane was developed based on the experimental results.