International Journal of Material and Mechanical Engineering
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Open Access journal
ISSN (Print) 2162-0695 - ISSN (Online) 2164-280X
Published by Science and Engineering Publishing Company [49 journals]
- Effect of SiO2 Addition on Microwave Dielectric Properties of
Abstract: Effect of SiO2 Addition on Microwave Dielectric Properties of Ca0.61La0.39Al0.39Ti0.61O3 Ceramics
Author Hao LiBin TangLin LiuShuren Zhan
The effects of SiO2 addition on microwave dielectric properties of Ca0.61La0.39Al0.39Ti0.61O3 ceramics prepared by a conventional solid-state ceramic route were investigated. The x-ray diffraction (XRD) results showed that all the samples with less than 2.0 wt% SiO2 addition exhibited only a single phase Ca0.61La0.39Al0.39Ti0.61O3 with tetragonal structure formed. Scanning electron microscopy (SEM) images of SiO2 doping ceramics sintered at 1340 ℃ for 12h showed a compact microstructure. The silica entered the crystal lattice or was diffused to the interstitial sites in ceramic matrix causing the increase of the lattice parameters. SiO2 addition formed the small ambiguous grains, which effectively lowered the sintering temperature. The SiO2-doped Ca0.61La0.39Al0.39Ti0.61O3 ceramics have a low sintering temperature of 1340°C and a near zero τf value. Good microwave dielectric properties with a εr = 41.5, Q × f = 39,491 GHz and τf = -0.1 ppm/°C are obtained for 0.02wt% SiO2 doped ceramics sintered at 1340 ℃ for 12h.
- Low-temperature Sintering of Bi2O3-B2O3 Glass Doped Li2ZnTi3O8 - Li2TiO3
Ceramic and Its Dielectric Properties
Abstract: Low-temperature Sintering of Bi2O3-B2O3 Glass Doped Li2ZnTi3O8 - Li2TiO3 Ceramic and Its Dielectric Properties
Author Yingxiang LiBin TangShu-ren ZhangHao L
The effects of Bi2O3-B2O3 (BBO) glass addition on phase composition, microstructure and microwave dielectric properties of 0.65Li2ZnTi3O8-0.35Li2TiO3 (LZT) ceramics were investigated in this paper. It was found that a small amount of BBO addition could not only effectively lower the sintering temperatures from 1100 ℃ to 840 ℃, but also reduce the temperature coefficient of resonant frequency (τƒ) and the Q×f value of LZT ceramic. When BBO content exceeded 3 wt%, an unknown phase was detected. Typically, the 0.5 wt% BBO doped LZT ceramic sintered at 840 ℃ for 4 h had good microwave dielectric properties of εr = 26.6, Q×f = 40,683GHz and τƒ = +1.0ppm/℃, it a promising ceramic for LTCC technology application.
- Density Analysis on Self-Assembled Monolayers (SAMs) of Functionalized
Alkanethiol on Gold over Polyethylene Terephthalate (PET) Substrate
Abstract: Density Analysis on Self-Assembled Monolayers (SAMs) of Functionalized Alkanethiol on Gold over Polyethylene Terephthalate (PET) Substrate
Author M. Jalal UddinM. Khairul IslamM. Nasir Uddin KhanM. ShahinuzzamanM. Khalid HossainM. Abdul Momi
In this work, an equivalent circuit from electrochemical impedance spectroscopy (EIS) has been designed and executed for qualitative analyzing of leaky behavior of self-assembled monolayers (SAMs) of octadecanethiol [CH3(CH2)17-SH] on gold (Au) suface. Polyethylene terephthalate (PET), the cost-effective substrate has been utilized for metalization of thin Au layer with subsequent formation of octadecanethiol SAM on it with systematic variation of adsorption time. The SAM layer shows its highly dependency on the adsorption time of the surfactants of octadecanethiol with the metal surface.
- Effects of Concrete Compressive Strength of Steel and Polyester Fiber
Admixtures and Vacuumed Dewatering Application
Abstract: Effects of Concrete Compressive Strength of Steel and Polyester Fiber Admixtures and Vacuumed Dewatering Application
Author HAKAN BOLATMUSTAFA CULL
Vacuum dewatering method is the process of removing some of mixing water from fresh concrete. Therefore, excess mix water damages are prevented and mechanical strengths increase after concrete takes the shape of the mold. Fiber admixtures are mostly used for increasing the flexural strength of concrete. However, there are also effects on the compressive strength. In this study, the effects of application of the vacuum dewatering on the compressive strength of concrete are examined with addition of steel and polyester fibers. The parameters of the study are fiber types (steel, polyester), fiber ratios (3 different ratios), fiber lengths (long, short) for concrete class (C16/20-C25/30-C35/45 according to EN) and two different application methods (normal, vacuum). The compressive strengths of the concrete prepared in accordance with these parameters are determined after 1, 3, 7 and 28 days. Thus, it is investigated that each of the parameters is affected concrete compressive strength.
- Separation of Uranium from Rare Earth Elements using Modified Polymeric
Abstract: Separation of Uranium from Rare Earth Elements using Modified Polymeric Resin
Author Emad H. BoraiMahmoud G. Hamed
Poly (Acrylamide- Maleic Acid- Amidoxime) P (AM-MA-AO) resin has been successfully prepared by modification of polymeric resin Poly (Acrylamide- Maleic Acid- Acrylonitrile) prepared by γ radiation grafting polymerization. Conversion of nitrile groups into the amidoxime was carried out by treatment of the polymer with hydroxylamine in alkaline solution. Identification of amidoxime group was qualitatively performed. The structure of the modified resin was confirmed using Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). The modified polymer was tested for separation of U4+ from some selected rare earth elements (REEs) such as La3+ and Eu3+ metal ions from aqueous solutions. U4+ ion was selected to represent the actinides while La3+ and Eu3+ were selected to represent the light and intermediate REEs respectively. Different key parameters such as contact time, pH, and initial metal ion concentration have been tested to optimize the sorption capacity as well as the separation efficiency of U4+ metal ions. Results demonstrated that the new prepared sorbent has higher sorption uptake for U4+ than that for La3+, Eu3+. The results also revealed that the new P(AM-MA-AO) resin has relatively high selectivity and high capacity for U4+ reaching to 123 mg/g at pH 5. The separation factor of the resin for U4+ between La3+ and Eu3+ being maximum at pH 5, reaching to 34.5 and 21.9 respectively.
- Effects of Concrete Compressive Strength of Macro and Micro Polypropylene
Fiber Admixtures and Vacuumed Dewatering Application
Abstract: Effects of Concrete Compressive Strength of Macro and Micro Polypropylene Fiber Admixtures and Vacuumed Dewatering Application
Author HAKAN BOLATMUSTAFA CULL
Polypropylene fibers are manufactured as an alternative to steel fibers. When steel fibers are exposed to adverse environmental conditions, they can lose their properties by time. Therefore, the physical and mechanical properties of the concrete expected from them are weaken. Polypropylene fibers have superior properties compared with steel fibers in terms of chemical and physical properties. There are two types of polypropylene fibers as an admixture in concrete; macro and micro. This study investigated the effects of macro and micro fibers of polypropylene on compressive strengths of normal and vacuum applied concrete. Parameters of the study were as follows: fiber diameter, 3-different fiber ratios, different fiber length, 3-different concrete strength class (C16/20-C25/30-C35/37 according to EN) and two different application methods (normal and vacuum). Compressive strength tests were performed at the end of 1, 3, 7 and 28 days. Consequently, all the parameters affected the compressive strengths and other properties of the macro and micro polypropylene fiber-reinforced concretes.