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Journal of Materials Science Letters
Chapman and Hall
Journal of Materials Science Letters

Chapman and Hall

0261-8028

Journal of Materials Science Letters/Journal Journal of Materials Science LettersSCI
正式出版
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    Photoreactivity and cell adhesiveness of amino-group-modified titanium dioxide nano-particles on silicone substrate coated by covalent linkage

    T. FuruzonoM. IwasakiS. YasudaA. Korematsu...
    4页
    查看更多>>摘要:Titanium dioxide (TiO_2) has been used in many industrial ways, such as in pigments, photo-catalysts and UV fillers. Recently, this material has attracted much interest in environmental or medical fields as an antibacterial or deodorization agent due to its photoreactivity. For example, Cai et al. reported that photoexited TiO_2 particles effectively induced cytotoxicity against HeLa cancer cells [1]. Morioka et al. also reported that TiO_2 particles showed an antibacterial effect against oral germ, cariogenic streptococcus mutans [2]. Nontoxicity to experimental animals is also one of its unique properties. TiO_2 is, therefore, very useful for medical fields.

    Study of the phase boundary in PS/SBS blends as revealed by microindentation analysis

    M. BoyanovaF. J. Balta CallejaS. Fakirov
    3页
    查看更多>>摘要:Polymer blends, with new exploitable combinations of properties, are an alternative to meet the steady increasing demands on polymer materials and the synthesis of new polymers. The mechanical behavior of these multicomponent materials, in relation to their formulation, composition and phase has been the subject of much work [1]. Similar to polymer composites [2], the blend properties strongly depend on the adhesion at the interphase boundary between the blend components. In order to enhance the dispersion and to stabilize the degree of dispersion reached, as well as to improve the adhesion, a third component (compatibilizer) is commonly used [3]. The compatibilizer has to be distributed on the phase boundary between the two components. For this reason it is important to have appropriate techniques for introduction of the compatibilizer as well as methods for proving its distribution on the phase boundary. Very recently [4-7] it was demonstrated that microindentation hardness can be successfully used for testing polymer phase boundaries.

    Comment on "A new probability index for estimating Weibull modulus for ceramics with the least-square method"

    Dongfang WuHong Jiang
    2页
    查看更多>>摘要:The Weibull distribution has been commonly used to describe the statistical variation in the fracture strength of brittle materials. Using Weibull's two-parameter equation, the probability of failure P at stress σ represented by [1] P = 1 - exp [-(σ/σ_0)~m] (1) where m and σ_0 are the Weibull modulus and scale parameter, respectively. The most widely used method to estimate the two parameters from a set of experimentally measured fracture stresses is by using linear regression (LR), involving the ranging of the strength data in an ascending order and the assignment of probability of failure to each datum [2]. There are several expressions to define the probability estimator [1]. In a letter entitled "A new probability index for estimating Weibull modulus for ceramics with the least-square method" [3], Gong proposed another one as follows: P_i = i-0.999/n=1000 (2) where n is the sample size, i.e. the number of specimens tested, and P_i is the probability of failure for the ith ranked datum. Equation 2 was recommended by the author because with correction factors used, it may result in a more accurate estimation of the Weibull modulus than the following two commonly used.

    Novel technique for the synthesis of lithium aluminate (LiAlO_2) powders from water-based sols

    M. ChatterjeeM. K. Naskar
    3页
    查看更多>>摘要:Lithium aluminate, LiAlO_2 (LA) in the Li_2O-Al_2O_3 system is long been known to be used as an important material in molten carbonate fuel cell and nuclear applications [1-5]. LA exists as three polymorphic forms: α-, β- and γ- with hexagonal, monoclinic and tetragonal structures respectively [2,4]. The α- form (low temperature phase) undergoes transformation to the γ-form (the high temperature phase) at about 900℃, while the metastable β-form is assumed to transform to the γ-phase at about 900℃. As the γ-LA exhibits the essential chemical, thermophysical and mechanical stability at high temperature along with the required irradiation behavior, it finds application as a tritiumbreeding blanket in fusion reactors. The capture of neutron by ~6Li is known to occur as follows [4].

    Effects of fine fiber structures on the mechanical and electrical properties of cold rolled Cu-Ag sheet

    Won-Bae LeeEui-Han YoonSeung-boo Jung
    4页
    查看更多>>摘要:The recent progress in the electrical, electronic, and automobile industries requires conductive materials to possess not only a high conductivity, but also high strength, as well as reasonable cost. In order to reach this goal, extensive studies have been carried out on various Cu alloys including Nb [1], Fe [2], Cr [3] and Ag [4] in situ composite with cold deformation and intermediate heat treatment. Among many Cu composite alloys, Cu-Ag alloy has a eutective two-phase structure. During the cold deformation such as rolling, drawing, forging and swaging, two phases composed of Cu-rich solid solution and Ag-rich solid solution, are compressed and elongated along the direction of deformation; the two phases form a fine fiber microstructure. Severe cold deformed Cu composites have ultra-high tensile strength which is larger than the value predicted by the rule of the mixture of the two materials. The ultra high strength can be explained by the very fine fibrous microstructure and the high dislocation density between the interfaces of two materials. The electricals conductivity is generally inversely proportional to the mechanical property. This problem can be overcome by an intermediate heat treatment which results in the precipitation of a second phase.

    XPS studies of freshly prepared rhenium nanoparticle dispersions from hydrazinium hydrate and borohydride reduction of hexacholororhenate solutions

    K. M. BabuM. R. Mucalo
    3页
    查看更多>>摘要:With an increase in the incorporation of colloidal or nano-sized rhenium particles into advanced materials such as catalysts [1], an intimate knowledge of the surface properties of rhenium in this state is vital. Earlier reports [2-4] have attempted to characterize the colloidal rhenium products obtained from reduction of perrhenate but only led to unproven inferences as to which oxidation states were present in the samples. In general, there is a surprising lack of such fundamental studies in the materials science or chemical literature. X-ray photoelectron spectrometry (XPS) is an authoritative technique for studying the surface speciation of colloidal materials ex situ [6, 7]. Our earlier XPS studies [5] conducted on colloidally unstable rhenium colloids generated from the hydrazinium hydrate reduction of hexachlororhenate (IV) ion showed that colloids prepared 1-2 days before XPS analysis had already undergone extensive oxidation to states even beyond the starting Re(IV) salt (i. e., to Re(VI) or Re(VII) by the time analysis was performed so that the initial oxidation state of the just prepared rhenium colloids was still uncertain. The current report aims to present and interpret XPS data of not only freshly prepared hydrazinium hydrate-generated rhenium colloids but also of the hitherto unstudied borohydride-generated rhenium colloid systems in order to deduce the initial oxidation states of the colloidal rhenium. The choice of hexacholorhenate (IV) as a starting reagent was made because there is an almost complete lack of data on the characterization of colloidal products from this compound.

    Study on compound layer formed during plasma nitrocarburizing of AISI 5140 steel

    A. AlsaranM. KarakanA. CelikF. Bulbul...
    3页
    查看更多>>摘要:Nitrocarburizing is a thermochemical treatment in which nitrogen and carbon are diffused into the surface of ferrous materials at the ferritic phase field of materials, commonly in the temperatures of 520-580℃. Nitrcarburizing can be applied in solid, liquid, gas and plasma atmospheres. The plasma nitrocarburizing is more economical, friendly with environment and produces faster nitrogen and carbon diffusion, lower gas consuption compared to other nitrocarburizing techniques [1-6].

    Influence of thermal treatment on photoconductive properties for TiOPc/SAN composites

    Li-Fang TongLi-Wei LiYong-Gang ShangguanQiang Zheng...
    3页
    查看更多>>摘要:Recently the stability of photoconductive properties and reliability of photoconductive devices composed of polymeric materials have attracted researcher's attention because of the academic interests and increasing commercial applications [1]. For some photoconductive composites containing phthalocyanines, the photoconductivity is strongly influenced by the presence of some impurities, like oxygen [2, 3] and also depends on electron donors and acceptors [4]. On the other hand, it was reported that humidity had influence on the photoconductivity of titanyl phthalocyanine (TiOPc) dispersed in polymer matrix, and the existence of H_2O could increase the photosensitivity of charge generation material, such as TiOPc [5, 6]. Lately we have found that photoconductive performance of titanyl phthalocyanine/poly (styrene-co-acryalonitrile) (TiOPc/SAN) prepared by coating was partly related to thermal-treatment conditions, because the content f residual tetrahydrofuran (THF) solvent in films during preparation was changed. The present article studies the effect of thermal treatment on photoconductive properties of TiOPc/SAN films on their photosensitivity (1/t_(1/2)) and the charging voltage (V_0).

    Formation process and lattice parameter of InAs/GaAs quantum dots

    M. D. KimH. S. LeeJ. Y. LeeT. W. Kim...
    4页
    查看更多>>摘要:The formation of self-assembled InAs quantum dots (QDs) on GaAs substrates has attracted much interest as a growth technique to fabricate promising nanoscale devices such as QD lasers [1] and QD infrared photodetectors [2,3] without an additional lithography process because QDs have discrete atom-like energy levels with good optical properties [4]. Self-assembled QDs in lattice-mismatched system,s such as InAs/GaAs and SiGe/Si, can be achieved by using the Stranski-Krastanov (SK) growth mode [5]. In the SK growth mode, the mismatched layer grows on the substrate two-dimensionally at first, then, above a critical thickness, strain-induced and dislocation-free QDs are formed on a residual two-dimensional wetting layer. An appropriate regulation of the respective growth conditions may provide the possibility for controlling precisely the size and the density of the QDs.

    Determining the confidence intervals of Weibull parameters estimated using a more precise probability estimator

    J. A. GriggsYunlong Zhang
    3页
    查看更多>>摘要:The two-parameter Weibull model [1] has been used to model the statistical variation in the failure stress of nominally identical ceramic components [2]. The probability that a given component will fracture at or below a tensile stress, σ, can be predicted as P_f = 1-exp [-(σ/σ_0)~m] (1) where m is the shape parameter, or Weibull modulus, and σ_0 is the scale parameter, or characteristic strength. The distribution parameters, m and σ_0, can be estimated by fitting Equation 1 to a random sample of n specimens with failure stresses, σ_i, and cumulative probabilities of failure, P_i, where i is the rank of each specimen. Cumulative probability of failure is usually calculated by applying a discrete probability estimator of the form [3-5] P-circumflex_i = i-α/n+β (2) where α and β are constant historically selected to minimize the bias of the sample Weibull modulus, m-cricumflex, so that m-circumflex/m≈1. Gong recently suggested the use of a correction factor, k_M= m-circumflex/k_m, may serve as an unbiased estimate of m [6]. Gong showed that values of α=-0.999 and β=1000 resulted in a low standard deviation for k_M and therefore a precise estimate of m.