Advanced Materials Research Vols. 1025-1026

Abstract: It’s quite often that dispensing a topping material like concrete crystalline penetration sealer materials onto the surface of a plastic substance such as concrete to extend its service life span by surface protections from outside breakthrough. When applied to concrete it reacts with calcium hydroxide and reduces the porosity and permeability of the concrete matrix. This serves to increase the hardness and chemical resistance which, in turn, increases the service life span of the surface. A series of tests, such as rapid chloride permeability test, scanning electron microscope, and mercury intrusion porosimetry, were performed on the concrete test samples to examine the durability, by taking the penetration depth of concrete crystalline penetration sealer materials as a characterization parameter describing the durability in relation to water resistance. The penetration depth is a critical property for concrete crystalline penetration sealer materials to function effectively. The deeper the penetration, the greater the thickness of concrete strengthened, thus improving wear resistance, the life span and durability. The desirable depth drawn from tests is about 10mm with a minimum of 5mm. However the regular attainment of such penetration will require considerable care in surface preparation and in assuring that the concrete is properly dry. The quality of the concrete will also be a major factor in the depth of penetration obtained. Penetration depths may be greater with poor quality porous concrete while a 10mm depth may not be possible with high-quality dense concrete. Other Factors affecting concrete sealer penetration depth are related to the process, such as coverage and application, a user who should understand how it works, and material itself, having its own image.

Abstract: Nanocrystalline CoFe films were fabricated by electrodeposition process for an investigation of the relationship between the alloys’ characteristics and their magnetic properties. The study shows that coating thickness promotes softer magnetic properties of the films, and induces changes of film roughness, preferred orientation and domain pattern. The preferred orientation of the ~1 μm films (thin films) is (110) plane, whereas that of the ~3 μm films (thick films) are (110) and (200) planes. The magnetic domain of the thin films exhibit a stripe-liked pattern, whereas a bubble-liked pattern appears in the thick films. Iron content significantly affects the magnetic properties of the thick films. In this study, the 57.3wt.%Fe thick film has the highest saturation magnetization, and the 80.0wt.%Fe thick film shows the lowest coercivity.

Abstract: A malononitrile derivative, 6-Amino-5,5,7-tricyano-3,3a,4,5-tetrahydro-2H-indene-4- Spirocyclopentane was synthesized in ethanol with malononitrile and cyclopentanone as raw materials. It was characterized by X-ray single crystal diffraction analysis.The crystal of the title complex belongs to Triclinic, P21/c space group with a=6.4687(13)Å, b=8.9901(18)Å, c=12.004(2)Å, α=93.55(3) deg, β=91.86(3) deg, γ=92.25(3) deg. V=695.8(2)Å3, Z=2, F(000)=278 and final R₁=0.0524,WR₂=0.1497. X-ray analysis reveals that The cyclohexene ring has a distorted half-chair conformation and the cyclopentene and cyclopentane rings adopt envelope conformations. The dihedral angles between planar fragments of the cyclohexene and cyclopentene rings and of the cyclohexene and cyclopentane rings are 10.67 (7) and 87.33 (3)°, respectively. In the crystal, intermolecular N-HN hydrogen bonds link the molecules into infinite chains running in the [10] direction.

Abstract: Galvanized steels are widely used in construction, electronic, and automotive applications. By applying heat treatment after the hot-dip galvanizing process, zinc and iron in the galvanized coatings are interacted and series of zinc-iron intermetallic phases are developed. Correspondingly, the properties of galvanized steels may be enhanced. In the recent past, attempts have been made to develop kinetics models to help predict the interdiffusion of zinc and iron in the hot-dip and annealing steps, yet they are generally complicated and sometimes do not agree well with the actual data. In this work, we extend the prior works to develop a mathematical model for predicting the interdiffusion of zinc and iron and the growth of intermetallic phases during annealing that is less complicated, yet provides reasonably accurate results, by using an explicit finite difference method (FDM) along with a special treatment at the boundaries of each phase. The data from literatures are compared and discussed to justify the accuracy of the model.

Abstract: Nickel alloys have been widely used for high temperature applications such as gas turbine engine, turbine blade and many high temperature resistance components. Aluminizing is one of effective to increase oxidation resistant of nickel alloys by forming nickel aluminide compounds on nickel surface. Nickel aluminide is formed by the diffusion mechanism. This research aims to study the diffusion behavior of nickel in Ni₂Al₃ compound. The diffusion coefficient is determined using Ni/Al diffusion couple forming Ni₂Al₃ and NiAl₃ phases. The temperatures under study are 873, 973, and 1073 K, which are at above and below melting point of aluminum. Determination of diffusion coefficient of Ni in Ni₂Al₃ is from mass balance concept: flux difference at interphase causes accumulation of atoms in compound layer, which as be derived as: dx_αβ/dt = [1/(n^β-n^α)] * [D_α *(dn^α/dx) - D_β *(dn^β/dx)] From this equation, diffusion coefficient of Ni in Ni₂Al₃ at 873 and 1073 K are calculated as 6.243×10^-11 and 6.82×10^-9 m²/s, respectively. From Arrhenius equation of diffusivity, D = D_oexp (-Q/RT), the activation energy for diffusion of nickel in Ni₂Al₃ is found to be 183 kJ/mol. The result obtained in this research is of great use in controlling aluminizing process.

Abstract: H13 steel has been widely used in several metal working industries. Plasma nitriding is employed for improving surface hardness, but it significantly decreases corrosion resistance of H13 steel. To improve corrosion resistance, Cr plating before and after plasma nitriding is studied in the research. Surface characterization, phase analysis, hardness and corrosion test were done to evaluate the appropriate method to improve corrosion resistance. It was found that Cr plating after plasma nitriding can improve the corrosion resistance close to as-heat treated sample. The formation of Cr can increase the corrosion potential to-310.66 mV(Ag-AgCl) comparing to-349.54 mV(Ag-AgCl) of as-heat treated sample. For the corrosion resistance at constant applied voltage tested by potentiostatic technique, the sample with plasma nitriding prior to Cr plating shows the lowest corrosion current which implies the lowest corrosion rate. For the process in which Cr plating is applied before plasma nitriding, CrN layer can be formed on the surface, but this layer is very thin (about 100 nm thick). This thin layer retards nitrogen diffusion; hence, nitrided layer beneath CrN layer cannot be formed. With only thin layer of CrN, both corrosion resistance and micro-scale surface hardness cannot be improved.

Abstract: In this study, we present a numerical technique for the improvement of computational efficiency for computation of microstructural evolution in alloy during solidification process. The goal of this technique is for the computational domain to grow around the microstructure and fixed the grid spacing, while solidification advances into the liquid region. The growth around the microstructure is controlled according with the solute diffusivity for binary alloy in the liquid region. The computation showed that the microstructure with well-developed secondary arms can be obtained with low computation time and moderate memory demand.

Abstract: In order to reduce the cost of Porous asphalt concrete and the effective use cheap limestone widely distributed in local, the gradation design works of limestone-typed PAC is presented in this paper. Considering convenience of building and testing for local enterprises, Marshall Design Method, still used in local standards, is adopt. Limestone usually shows low strength and easy break, which obviously affect the performance of mixture. Therefore, Forming temperature and beat numbers of Marshall Test is researched. The results show that: a) Regular aggregate, whose shape is similar to a cube, with low flat ratio and low crushing value is important for improving the performance of limestone-typed PAC. b) Forming temperature and Beat number is suggested taking 155°C and 35 times. c) The standard of limestone-typed PAC should not be as same as basalt-typed. The indices can be suitably lessened according to the actual conditions of aggregates.

Abstract: The aim of this study was to evaluate the antimicrobial property of essential oil extracted from the leaves of Ocimum americanum against oral bacteria related to periodontal disease. Three species of periodontal pathogens including Porphyromonas gingivalis W50, Prevotella intermedia ATCC 25611 and Fusobacterium nucleatum ATCC 25586 were included in the study. Agar diffusion was performed initially to screen the antimicrobial activity of O. americanum essential oil. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were then determined using the Millipore Membrane method. The result showed that in the agar diffusion, essential oil extracted from Ocimum americanum exhibited antimicrobial activity against all test bacteria with the zone of inhibition ranging from 24 to 30 mm. The MIC values against P. gingivalis and P. intermedia were 0.35 mg/mL whereas that of F. nucleatum was 0.70 mg/mL. The MBC values against P. gingivalis and P. intermedia were 0.70 mg/mL whereas that of F. nucleatum was 1.4 mg/mL. In conclusion, O. americanum essential oil has an antimicrobial activity which may be a beneficial component of oral health care products to control or prevent periodontal disease by reducing these bacteria in the oral cavity.

Abstract: Liquid crystal was formed in a ternary system of tetraethylene glycol lauryl ether, water and 1-ethyl-3-methylimidazolium hexafluorophosphate. Its structure was identified by polarized optical microscopy and small-angle X-ray scattering techniques. Compared to that in the binary system, lamellar phase was retained with the addition of a small amount of imidazolium salt. Molecules of 1-ethyl-3-methylimidazolium hexafluorophosphate were considered to be solubilized in the polar domain of the ordered assemblies. Results on their influence on the lamellar phase enlighten the use of imidazolium salts to modulate liquid crystalline materials and other assemblies.