American Journal of Materials Science最新文献

{"title":"Piezochromic Polymer Materials Displaying Pressure Changes in Bar-Ranges","authors":"A. Seeboth, D. Loetzsch, R. Ruhmann","doi":"10.5923/J.MATERIALS.20110102.23","DOIUrl":"https://doi.org/10.5923/J.MATERIALS.20110102.23","url":null,"abstract":"A piezochromic material exhibiting a pressure dependent reversible shift of the selective reflection wavelength via the entire visible range is developed. The material consists of a cholesteric mixture embedded in a cholesteric elastomer matrix bearing mesogenic side chains with similar molecular structure. The change of the selective reflection has its origin in a compressible helix structure. Thus, the pitch length is switched by pressure changes. To trigger the reversible piezochromic effect already pressure changes in bar-range are sufficient. The pressure controlled colour changes are excellent detectable by the human eye and still appear even after 100 cycles. Piezochromic effects based on modification changes of inorganic crystalline materials, such as LiF or NaCl monocrystals, are known phenomena since several decades. For example, the transition from the green α- into the red γ-modification of CuMoO4 requires a pressure of 2.5 kbar and transitions in palladium complexes are reported to re- quire pressures ranging from 1.4 to 6.5 GPa (=14 to 65 kbar)(1,2). However, the high pressure which is necessary for the modification changes makes these materials unsuit- able as pressure sensors in the ordinary area of life. Colour changes by pressure in organic polymer materials are fre- quently but not systematically described in literature so far. A bathochromic shift of the absorption band of poly (3-dodecylthiophene) was observed by increasing the pres- sure from atmospheric pressure to 8 kbar(3). In reference(4) a bathochromic shift from 605 nm to 672 nm (∆λ = 67 nm) is reported for poly(3-(1-dodecyl) thiophene-2,5-diyl) when the pressure is increased from normal pressure to 10.71 GPa (=107.1 kbar). The piezochromic effect of these conjugated polymers is based on pressure dependent shifts of the ab- sorption band. The aim of the present work was to develop piezochromic polymer materials exhibiting, for the first time, colour changes detectable with the human eye in dependence of pressure differences as small as a few bar. Such material could be used as an optical pressure sensor in the ordinary area of life. Our strategy is based on the knowledge about the preparation of cholesteric polymer materials with a selective","PeriodicalId":7420,"journal":{"name":"American Journal of Materials Science","volume":"73 1","pages":"139-142"},"PeriodicalIF":0.0,"publicationDate":"2012-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90141234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sliding Behavior of C/C and C/C-SiC Composites in Acidic Environment-Against High Chromium Steel Disc","authors":"V. Srivastava","doi":"10.5923/J.MATERIALS.20110102.17","DOIUrl":"https://doi.org/10.5923/J.MATERIALS.20110102.17","url":null,"abstract":"The wear behaviour of carbon-carbon (C/C) and carbon-carbon-silicon-carbide (C/C-SiC) composites were studied using a pin-on-disc test rig under dry condition before and after immersion in 25% concentrated H2SO4. The influence of the weight loss and worn temperature against sliding distance and time were investigated. It was found that the weight loss increases with increasing of sliding distance and time, where worn surface temperature increases slowly up to 1.5 Km sliding distance and then tended to become constant. Also, weight loss and worn surface temperature reduces with the exposure of 25% concentrated sulphuric acid. However, the C/C-SiC composites exhibiting a lower weight loss but higher worn surface temperature compare to C/C composites at constant load. The wear and worn temperature of C/C composite gradually in- creases compare to C/C-SiC composite, with an average fading ratio of 7.7% (C/C composite) and 7.4% (C/C-SiC composite). Scanning electron microscope and projection microscope micrographs show that the graphite film was transferred on the test pin side, which stabilized the increase in test pin temperature after the formation of a thick film of graphite debris.","PeriodicalId":7420,"journal":{"name":"American Journal of Materials Science","volume":"79 1","pages":"103-107"},"PeriodicalIF":0.0,"publicationDate":"2012-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84107680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Adsorption and Inhibitive Properties of Leaf Extract of Newbouldia leavis as a Green Inhibitor for Aluminium Alloy in H 2 SO 4","authors":"L. Nnanna, Onyinyechi C. Nwadiuko, Nneka D. Ekekwe, C. F. Ukpabi, S. C. Udensi, K. Okeoma, B. N. Onwuagba, I. M. Mejeha","doi":"10.5923/J.MATERIALS.20110102.24","DOIUrl":"https://doi.org/10.5923/J.MATERIALS.20110102.24","url":null,"abstract":"The corrosion inhibition of Al and its alloys is the subject of tremendous technological importance due to the increased industrial applications of these materials. This study reports the corrosion inhibition of AA8011 aluminium alloy in acidic solutions using Newbouldia leavis leaf extract by way of gravimetric measurements. It was shown that the presence of Newbouldia leavis leaf extract inhibited the corrosion of aluminium in the test solutions and the inhibition efficiency de- pended on the concentration of the plant extract as well as on the time of exposure of the aluminium samples in H2SO4 so- lutions containing the extract. The experimental data complied to the Langmuir adsorption isotherm and the value and sign of the Gibb's free energy of adsorption obtained suggested that inhibitor molecules have been spontaneously adsorbed onto the aluminium surface through a physical adsorption mechanism.","PeriodicalId":7420,"journal":{"name":"American Journal of Materials Science","volume":"9 1","pages":"143-148"},"PeriodicalIF":0.0,"publicationDate":"2012-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76342502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Influence of Process Parameters on Microstructure and Mechanical Properties of Friction Stir Welded Al 5083 Alloy Lap Joint","authors":"H. Bisadi, M. Tour, A. Tavakoli","doi":"10.5923/J.MATERIALS.20110102.15","DOIUrl":"https://doi.org/10.5923/J.MATERIALS.20110102.15","url":null,"abstract":"Recently the aircraft and military industries widely have been using aluminum alloys particularly because of their fine strength to weight ratio. However in compare with steels they represent welding difficulties and also lower ductility. In last years it has been observed that Friction Stir Welding (FSW) method represents better microstructure and mechanical properties than conventional methods in welding aluminum alloys. In this study experiments were performed to investigate the effects of FSW process parameters including rotational and welding speed on the microstructure and mechanical prop- erties of aluminum 5083 alloy in lap joint welding and different joint defects were analyzed. It was observed that the nugget area had the best grain size and also higher hardness in compare with the other welding areas. Also the best joint properties were achieved at the rotational speed of 825rpm and welding speed of 32mm/min.","PeriodicalId":7420,"journal":{"name":"American Journal of Materials Science","volume":"81 1","pages":"93-97"},"PeriodicalIF":0.0,"publicationDate":"2012-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80119136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sem Studies of Tensile Fractured Surfaces of Expanded Graphite/Acrylonitrile/Methyl Methacrylate Nanocomposites Prepared via in-Situ Polymerization","authors":"S. C. Udensi, L. Nnanna","doi":"10.5923/J.MATERIALS.20110102.20","DOIUrl":"https://doi.org/10.5923/J.MATERIALS.20110102.20","url":null,"abstract":"Expanded graphite/Acrylonitrile/methyl methacrylate nanocomposites of different weight contents (0 to 5 wt. %) of Expanded Graphite (EG) were prepared via polymerization and examined for their yield and failure behaviours under uniaxial stress state. The failure mechanism shows transitions from sheared to crazed states as the volume contents of EG were increased. SEM photomicrographs also confirmed the brittle to ductile microstructural transitions of the nano- composites. The toughness of the nanocomposite with 3 wt. % EG was optimum, and the process of crack growth which led to this high toughness could be seen. The decisive parameter which influenced the fracture data of EG/AN/MMA nano- composites was found to be volume fraction of EG and interfacial adhesion of AN/MMA matrix and EG particles.","PeriodicalId":7420,"journal":{"name":"American Journal of Materials Science","volume":"6 1","pages":"123-127"},"PeriodicalIF":0.0,"publicationDate":"2012-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77032110","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution of Dislocation Substructures in Fatigue Loaded and Failed Stainless Steel Processed by High-intensity Electron Beam","authors":"S. Konovalov, S. Vorobyev, Y. Ivanov, S. V. Gorbunov, V. I. Myasnikova, V. Gromov","doi":"10.5923/J.MATERIALS.20120203.11","DOIUrl":"https://doi.org/10.5923/J.MATERIALS.20120203.11","url":null,"abstract":"Electron-beam treatment of 08Cr18Ni10Ti steel in the mode of ~5 μm surface layer melting (electron beam energy density is 25 J/cm 2 ) results in increase in fatigue durability by a factor of 3.44. Investigations of the structure-phase states and defective substructure and the factors responsible for increase in fatigue durability of steel have been carried out by the methods of optical, scanning and transmission electron diffraction microscopy.","PeriodicalId":7420,"journal":{"name":"American Journal of Materials Science","volume":"39 1","pages":"95-98"},"PeriodicalIF":0.0,"publicationDate":"2012-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80049130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Photoluminescence Studies on Nanocrystalline Tin Oxide Powder for Optoelectronic Devices","authors":"L. C. Nehru, V. Swaminathan, C. Sanjeeviraja","doi":"10.5923/J.MATERIALS.20120202.02","DOIUrl":"https://doi.org/10.5923/J.MATERIALS.20120202.02","url":null,"abstract":"Nanocrystalline tin oxide (SnO2) powders have been synthesized by a low temperature chemical precipitation method. As-prepared and heated powders were characterized by XRD, SEM and luminescence studies. Crystallographic parameters such as crystallite size, lattice parameters and dislocation density in SnO2 nanocrystalline powders were calcu- lated by Rietveld analysis. The average crystallite size of 9 - 43 nm was obtained for SnO2 powders through controlled heat treatment process. The washed powders morphology was almost spherical in shape and average agglomerate crystal size was between 0.2 - 0.4 μm. A Photoluminescence (PL) study was measured at an excitation wavelength of 265 nm for as-prepared and annealed powders; it showed a broad emission peak at 417 nm for all powders. The highest PL emission was attained for the powder annealed at 500℃. The synthesized nanocrystalline SnO2 oxide semiconductor material could be suitable for making optoelectronic and sensor devices.","PeriodicalId":7420,"journal":{"name":"American Journal of Materials Science","volume":"115 1","pages":"6-10"},"PeriodicalIF":0.0,"publicationDate":"2012-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79416133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Artificial Neural Network Modeling for Al-Zn-Sn Sacrificial Anode protection of Low Carbon Steel in Saline Media","authors":"O. Oluwole, N. Idusuyi","doi":"10.5923/J.MATERIALS.20120203.05","DOIUrl":"https://doi.org/10.5923/J.MATERIALS.20120203.05","url":null,"abstract":"This work presents the artificial neural network(ANN) modeling for sacrificial anode cathodic protection of low carbon steel using Al-Zn-Sn alloys anodes in saline media. Corrosion experiments were used to obtain data for developing a neural network model. The Feed forward Levenberg-Marquadt training algorithm with passive time, pH, conductivity,% metallic composition used in the input layer and the corrosion potential measured against a silver/silver chloride(Ag/AgCl) reference electrode used as the target or output variable. The modeling results obtained show that the network with 4 neurons in the input layer, 10 neurons in the hidden layer and 1 neuron in the output layer had a high correlation coefficient (R-value) of 0.850602 for the test data, and a low mean square error (MSE) of 0.0261294. 9","PeriodicalId":7420,"journal":{"name":"American Journal of Materials Science","volume":"63 2 1","pages":"62-65"},"PeriodicalIF":0.0,"publicationDate":"2012-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79769627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Natural Rubber/ Organoclay Nanocomposite from Tea ( Camellia S inensis ) Seed Oil Derivative","authors":"L. Yahaya, K. Adebowale, A. Menon, B. I. Olu-owolabi","doi":"10.5923/J.MATERIALS.20120202.01","DOIUrl":"https://doi.org/10.5923/J.MATERIALS.20120202.01","url":null,"abstract":"Sodium salt of tea seed oil (TSO-Na) was organomodified with kaolin (China clay). The organo-kaolin was characterized by determining the FTIR and XRD. Results indicated that TSO-Na was successfully intercalated onto the kaolin surface. Nanocomposite of rubber copolymer with tea seed oil organomodified kaolin was prepared by incorporating 5phr organo-kaolin. The mechanical testing of the rubber vulcanizate involved the determination of tensile and tear property. The performance characteristics showed that there was considerable improvement in the tensile strength, tear strength and elongation at break properties of the organoclay filled vulcanizate compared to the unmodified polymer. Scanning electron microscopy (SEM) studies revealed that the incorporation of 5phr organoclay has remarkable effect on the failure mechanism of the NR filled vulcanizate. This is an indication that the failure mechanism is strongly dependent on the reinforcement effect of the modified filler marked by a higher extent of rubber-filler matrix interaction. There is therefore indication that tea seed oil can be organomodified with kaolin to serve as nanofiller.","PeriodicalId":7420,"journal":{"name":"American Journal of Materials Science","volume":"86 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2012-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83752077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Application of the Experiment Design Method in Modelling the Temperature Effect on the Behaviour at a Low Velocity Impact Damage of Epoxy Matrix Reinforced with Unidirectional Carbon Fiber Composite","authors":"Zenasni Ramdane, H. Ahmed, J. Olay","doi":"10.5923/J.MATERIALS.20120203.02","DOIUrl":"https://doi.org/10.5923/J.MATERIALS.20120203.02","url":null,"abstract":"The present study was carried out to evaluate the temperature effect on the mode II interlaminar fracture be- haviour of two unidirectional carbon fiber composite materials subject to low velocity impact damage. Before testing, the specimens were exposed at positive and negative temperatures. The delamination crack energy was calculated at the maximum loading point according to the directed beam theory, to the corrected beam theory and to the compliance calibra- tion. Two types of carbon fiber epoxy composite materials were investigated of denominations AS4/8552 and AS4/3501-6. Unidirectional panels of 32 plies were fabricated according to the prepreg manufacturers. A thin film of PTFE was intro- duced between the mid-planes of the panels in order to provide an artificial starter crack of length 60 mm. Of each materials, five specimens were tested at the statically and the dynamical mode II at the temperatures of:-30,-15, 0, 15, 30, 45 and 60°C. From the experimental results, we conclude that the two composites have a similar behaviour, with a slightly effect of a temperature. The experimental design method was used to obtain a mathematical model describing the effect of the tem- perature on the crack delamination energy. The compliance calibration method gives conservative values of the crack delamination energy.","PeriodicalId":7420,"journal":{"name":"American Journal of Materials Science","volume":"19 1","pages":"44-48"},"PeriodicalIF":0.0,"publicationDate":"2012-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85267825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}