bluuebunny/crossref_metadata_2025 huggingface dataset:
Strength Characteristics of Recycled Concrete after Freezing and Thawing
Authors: Xu Wen Bin , Hu Yu , Liu Teng Fei , Li Xiang
Published: May 2011

Due to the recycling of construction waste, recycled concrete has gradually become a viable material in the construction industry. To study the strength property of the recycled concrete after freeze-thawing experiments, recycled concrete and ordinary concrete were tested for their post-test strength after freeze-thawing for 0, 50, and 100 times. The result shows that the strength of the recycled concrete declined more quickly than that of normal concrete after freeze-thawing. In the paper, the two kinds of concrete underwent permeability test and the two kinds of aggregate underwent mercury intrusion. After the comparison of the inner structure of the concrete and aggregate was obtained, the influence of concrete pore structure on strength after freeze-thawing was further analyzed. The result of the permeability test shows that the porosity of recycled concrete is large when taken as a whole, and the water content is higher after steeping, which reduces the strength of the material. Mercury intrusion results also show that the pore structure of recycled aggregate is poor and that there are more internal micro-cracks. Therefore, in areas with regular freeze-thawing cycles, particularly in humid areas, the use of recycled concrete should be prudently used and handled accordingly.
Studies about the Initial Curing Conditions on the Carbonation Resistance of Fly-Ash Concrete
Authors: Lu En Li , Li Guo , Yuan Ying Shu , Geng Ou , Du Jian Min
Published: May 2011

Studies about the resistance of carbonation capability of fly-ash (FA) concrete at different initial curing regimes and exposure time through accelerated carbonation experiments were made. Firstly, 30% replacement ratio fly-ash concrete specimens were fabricated and cured in 20°C, 30°C and 40°C water for 3d, 7d, 14d and 28d respectively, and cured in a standard air environment (20±2°C, relative humidity ≥95% ) for 28d. As a comparison, ordinary Portland concrete (OPC) specimens were also made and cured in 30°C water for 7d, and standard curing for 28d. After the initial curing, all the specimens were taken out and placed indoor natural environment. When specimen age reach 30d, 60d and 120d, 2 weeks accelerated carbonation experiments were made and concrete carbonation depth were measured. In addition to this, hydration degrees of fly ash at different initial curing conditions were measured using the selective dissolve method. Results show that the initial curing conditions play an important role in the carbonation resistance of FA concrete. Initial water curing is beneficial to the development of carbonation resistance of FA and OPC concrete. Prolonging initial curing time and increasing curing temperature is beneficial for the carbonation resistance of FA concrete. For the same curing conditions, carbonation rate of FA concrete is usually higher than OPC concrete, but with the increase of initial curing temperature, the difference can be reduced.
Effect on Structure and Early Hydration Activity of Steel Slag Modified by Adjusting Materials and Temperature
Authors: Zhao Hai Jin , Yu Qi Jun , Wei Jiang Xiong , Li Jian Xin
Published: May 2011

The aim of this paper is to investigate effect on hydration activity of steel slag by modifying its mineralogical composition and structure incorporating electric arc furnace steel slag (EAFS) and fly ash (FA) into it at high temperature, and the process was simulated in laboratory that mineral admixtures were added to the melting slag during slag-discharging process. The mineralogical composition, microstructure of both basic oxygen steel slag (BOFS) and modified steel slag (MSS) were identified with XRD and optical microscopy. The results show that after modification, silicate minerals in MSS are decreased in amount with FA being increased; furthermore, silicate minerals in which are increased in amount with C/S molar ratio improvement. Three days cumulative hydration heat of GB40-1350 is greater than that of BOFS by 1.9 times.
Study on Determination Method of the Volatile Organic Compounds Emissions from Particleboards for Indoor Finishing
Authors: Sun Shi Jing , Shen Jun , Zhao Zhong Yuan
Published: May 2011

In order to comprehensive understand and control volatile organic compounds (VOCs) release from particleboards, this paper takes Larix gmelini particleboard as example and analyzes VOCs by three different methods. First of all, VOCs of Larix gmelini particles were detected by the static head space solid-phase micro-extraction (HS-SPME) technique. Secondly Larix gmelini particleboards were analyzed using the method of adsorbed by activated carbon, desorpted with methylene dichloride and measured by GC/MS. Finally, Tenax-T Thermal desorption -GC/MS was used to qualitative VOCs emissions. The best method for determination VOCs from particleboards was found. SPME is a simple operation method with short time. But the pretreatment of sample was troublesome and it is not easily measured for lower concentration particleboards. Active carbon absorption method is not suitable for quantitative because of much error in extraction. It is suitable for qualitative analysis. Tenax-T is a simple operation way with short analysis time and good shape of chromatographic. It is a convenient and practical method. Further study of VOCs emission of panels can be supported by this method.
Experimental Study on Static Characteristics of Sandy Pebble Soil
Authors: Jia Bin , Yao Yong , Cheng Lu , Chen Dai Guo
Published: May 2011

Through the consolidation drained triaxial shear test of sandy pebble soil, the stress-strain curve of sandy pebble soil is obtained, analysis manifest that in the shearing process, shear dilatancy deformation and shear contraction deformation of sandy pebble soil are intercoupling, making asymptote of the curve after peak stress nearly a horizontal line. Meanwhile, based on the Duncan-Chang model, elastic modulus and Poisson ratio features of sandy pebble soil are analyzed, and Duncan-Chang model parameters are obtained.
The Implementation of Statistical Inference to Study the Bending Strength of Sustainable Hybrid Sandwich Panel Composite
Authors: Fajrin Jauhar , Yan Zhu Ge , Bullen Frank , Wang Hao
Published: May 2011

The study reported here involves the evaluation of the ultimate bending stress (bending strength) of hybrid sandwich panels using a simple comparative statistical analysis. Four sets of beam were tested with each set consisting of modified beams (MB) and unmodified beam (UB) samples. A total of 42 beam samples were tested using 3 point bending followed by statistical inference analysis using a t-test. The results show that the introduction of an intermediate layer has a significant effect on increasing the bending strength of the new hybrid sandwich panel composite.
Properties of Fly Ash Based Geopolymer Concrete Exposed to Sustained Elevated Temperatures
Authors: Sudarshan M.S. , Ranganath R.V.
Published: May 2011

Fly ash based geopolymer concrete is gaining importance in the context of developing alternatives to cement concrete. The research work available in the literature shows many beneficial effects of the material in terms of its high early compressive strength, tensile strength, reduced shrinkage, good acid resistance etc., However, there are very few studies carried out on the influence of sustained elevated temperature on the properties of geopolymer concrete. This paper presents the results of some of the properties of fly ash based geopolymer concrete activated using sodium silicate and sodium hydroxide and subjected to elevated temperature at 150°C, 200°C, 300°C, 400ºc under sustained durations of 1 hour, 2 hours and 4 hours. The results show that residual compressive strength is about 20% less than the normal at about 200°C itself possibly due to the development of vapour pressure formed by the non-reactive water present in the system. Beyond 2 hours of sustenance, there is not much of a difference in the properties of concrete.
Experimental Study of the Effect of Water Reducer on the Plaster Board Production in Low Energy-Consumed Way
Authors: Sun Jing , Cong Xiao Hong , Liu Hong Bo , Sun Li
Published: May 2011

As a green building material, the demand for plaster board is growing with the promotion of the wall materials reform policy and development of the construction industry in China. In terms of its production technology, the technique formula of the raw materials for gypsum board is not only the main factors to determine the quality, but also determine the use of equipment related to production technology. In this paper, according to the actual production conditions of Beijing New Building Materials Group Industrial Park in Zhuozhou, water-reducing agent is introduced in its raw materials and specific researches are made about the properties of gypsum when water reducer, foam, coagulant agent and other additives are mixed. The results show that the suitable water-reducing agent used in conjunction with other gypsum admixtures not only improve the quality, but also play an important role in saving energy, improving production efficiency, and reducing production costs.
Effect of Cement Clinker on the Properties of Flue Gas Desulphurization Gypsum-Steel Slag Cementitious Composites
Authors: Wang Zhi , Zhang Lei , Fan Li Ying , Shi Guo Pu
Published: May 2011

The effects of cement clinker on the properties of flue gas desulphurization gypsum-based steel slag composites were analyzed in this article and the influence rules of setting time, final setting time, flexural strength and compressive strength of cementitious composites were also discussed. The micro-morphology of the composite was observed by scanning electron microscope. At the same time, the excitation mechanism of cement clinker on gas desulphurization gypsum-based steel slag was put forward. It was demonstrated that cement clinker with content of 2% in the composites can better stimulate the activation of steel slag and improve the mechanical properties of the composites.
Al-Film/Si-Substrate System Nanoscratching Response Based upon Molecular Dynamics Simulation in NEMS
Authors: Malik M. Rizwan , Shi Tie Lin , Tang Zi Rong , Peng Ping
Published: May 2011

A growing scientific effort is being devoted to the study of nanoscale interface aspects such as thin-film adhesion, abrasive wear and nanofriction at surfaces by using the nanoscratching technique but there remain immense challenges. In this paper, a three-dimensional (3D) model is suggested for the molecular dynamics (MD) simulation and experimental verification of nanoscratching initiated from nano-indentation, carried out using atomic force microscope (AFM) indenters on Al-film/Si-substrate systems. Hybrid potentials such as Morse and Tersoff, and embedded atom methods (EAM) are taken into account together for the first time in this MD simulation (for three scratching conditions: e.g. orientation, depth and speed, and the relationship between forces and related parameters) in order to determine the mechanisms of nanoscratching phenomena. Salient features such as nanoscratching velocity, direction and depth - as well as indenter shape- and size-dependent functions such as scratch hardness, wear and coefficient of friction - are also examined. A remarkable conclusion is that the coefficient of friction clearly depends upon the tool rake-angle and therefore increases sharply for a large negative angle.
Prediction of Transient Temperature Distribution, HAZ Width and Microstructural Analysis of Submerged Arc-Welded Structural Steel Plates
Authors: Ghosh Aniruddha , Chattopadhyaya Somnath
Published: May 2011

Critical investigation of the transient temperature distribution is important for maintaining the quality of the Submerged Arc Welding of structural steel plates. The aim of this paper is to derive an analytical solution to predict the transient temperature distribution on the plate during the process of Submerged Arc Welding. An analytical solution is obtained from the 3D heat conduction equation. The main energy input that is applied on the plate is taken as the heat lost from the electric arc. The kinetic energy of filler droplets, electromagnetic force and drag force are also considered as input to the process. The electric arc is assumed to be a moving double Central Conicoidal heat source which follows approximately the Gaussian distribution. It is observed that the predicted values are in good agreement with the experimental results. The heat-affected zone (HAZ) width calculation is also done with the help of the analytical solution of the transient 3D heat conduction equation. Analysis of microstructural changes is critically investigated to comprehend the HAZ softening phenomenon and for the validation of the predicted HAZ width.
Evaluation of the Effect of Catalyst Pore-Size Distribution on the Effectiveness Factor in Ethylbenzene Dehydrogenation by Orthogonal Collocation
Authors: Zeynali Mohammad Ebrahim
Published: May 2011

The mathematical model for multicomponent diffusion in styrene production is given considering all six reactions involved in styrene production. The diffusion coefficients for catalyst pellet are calculated for unimodal and bimodal pore size distributions using trapezoidal rule of integration. The effects of standard deviation and average pore size on the diffusion coefficient are determined. The differential equations are converted to algebraic equations and solved by the orthogonal collocation method. The effectiveness factor of catalyst pellet in styrene production is calculated for various pore sizes. It is seen that the average pore size and pore size distribution affects the production rate and effectiveness factor significantly.
Structural Rigidity, Percolation and Transition-Temperature Study of the Ge19Se81-xSbx System
Authors: Sharma Neha , Sharda Sunanda , Sharma Vineet , Sharma Pankaj
Published: May 2011

Selenium-based glasses are attractive candidate materials because of their low transmission losses and other optical properties. In the present paper, samples of Ge19Se81-xSbx (x = 0, 4, 8, 12, 16, 17.2, 20) were prepared by using the melt-quench technique, and their X-ray diffraction spectra were studied. Some of the physical parameters were calculated theoretically. It was observed that the glass transition temperature increased up to x = 17.2 and then decreased whereas the theoretically calculated band-gap decreased with increasing Sb content.
Structural and Electrical Changes in BIMNVOX Oxide-Ion Conductor
Authors: Beg Saba , Hafeez Shehla , Al-Areqi Niyazi A.S.
Published: May 2011

Ceramic solid solutions Bi4MnxV2–xO11–(x/2)–δ in the composition range 0.07 ≤ x ≤ 0.30 were obtained by solid state synthesis. Structural investigations were carried out by using a combination of FT-IR and powder X-ray diffraction technique. Polymorphic transitions (β↔γ and γ′↔γ) were detected by DTA and variation in the Arrhenius plots of conductivity. The solid solutions with composition 0.07 ≤ x ≤ 0.17 are isostructural with the orthorhombic β-phase, and those with x ≤ 0.30 represent tetragonal γ-phase. With increasing Mn concentration, the conductivity of solid solutions increases from 3.684×10-6 (x = 0.07) to 2.467×10-5 (x = 0.17). AC impedance plots show that the conductivity is mainly due to the grain contribution which is evident in the enhanced short range diffusion of oxide ion vacancy in the grains with increasing temperature.
Microstructure and Microhardness of a Nanostructured Nickel-Iron Based Alloy
Authors: Mukhtarov Shamil Kh. , Sauvage Xavier
Published: May 2011

This paper presents an overview and some original results about the mechanical properties and phase analysis of a nanostructured (NS) nickel-iron based alloy INCONEL 718. This structure was obtained by severe plastic deformation (SPD) via high pressure torsion (HPT) and multiple isothermal forging (MIF) of the alloy with an initial coarse-grained (CG) structure. Materials before and after SPD were analyzed by scanning, transmission electron microscopes and atom probe tomography (APT). Experimental data indicate that after HPT at room temperature - phase was partly dissolved and that precipitation of the -phase occurs during post deformation aging. A hardness up to 8 GPa was recorded for the NS alloy after SPD and annealing at 600°C.
Mechanical Properties and Fracture Behaviour of Nanostructured and Ultrafine Structured TiAl Alloys Synthesised by Mechanical Milling of Powders and Hot Isostatic Pressing
Authors: Zhang De Liang , Yu Hong Bao , Chen Yuong
Published: May 2011

Bulk nanostructured (grain sizes in the range of 50-200nm) and ultrafine structured (grain sizes in the range of 100-500nm) -TiAl based alloys with compositions Ti-47Al (in at%) and Ti–45Al–2Cr–2Nb–1B–0.5Ta (in at%), respectively, have been produced using a combination of high energy mechanical milling of mixtures of elemental powders and hot isostatic pressing at 800 and 1000oC respectively, and the microstructures of the samples have been characterised. At room temperature, the HIPed samples fractured prematurely at tensile stresses in the range of 200-300MPa and showed no ductility, very likely due to the relative high oxygen content (0.6wt%) in the samples and very low tolerance of TiAl based alloys on dissolved oxygen. At 800oC, the HIPed samples showed a yield strength in the range of 55-70MPa, a tensile strength in the range of 60-80MPa, a large amount of elongation to fracturing around 100% and clear strain softening. Examination of the fractured tensile test specimens at room temperature and 800oC showed that the level of the consolidation was fairly high, but the HIPed samples do contain a small fraction of interparticle boundaries with weak atomic bonding. The fracture of the HIPed samples in tensile testing at room temperature and 800oC, respectively, is predominately intergranular, and the large amount of plastic deformation prior to fracture at 800oC is achieved mainly through grain boundary sliding in conjunction with dislocation gliding, in agreement with the deformation mechanisms of nanostructured and ultrafine structured alloys generally agreed by researchers.
Structure Evolution and Deformation Resistance in Production and Application of Ultrafine-Grained Materials – the Concept of Steady-State Grains
Authors: Blum Wolfgang , Eisenlohr Philip
Published: May 2011

Severe plastic predeformation of crystalline materials leads not only to formation of a steady-state dislocation structure including low-angle boundaries, but also brings the high-angle boundary structure into a steady state. When the steady-state flow stress is high enough, the material becomes ultrafine-grained or even nanocrystalline. The change from coarse-grained to ultrafine-grained is accompanied by a distinct change in the steady-state deformation resistance that is measured after predeformation. This is explained by two opposing effects of high-angle boundaries, namely enhanced dislocation storage and accelerated dislocation recovery. The first one causes net hardening at high temperature-normalized strain rate Z (Zener–Hollomon), the second one net softening at low Z. This means that the rate-sensitivity of the flow stress is enhanced, which causes the paradoxon of enhanced strength at enhanced ductility. Tests with abrupt large changes of deformation conditions bring the strain associated with dynamic recovery into the focus. The results of such tests indicate that the boundaries, low-angle as well as high-angle ones, migrate under concentrated stress during deformation and thereby contribute to straining and recovery. The corresponding system of differential equations needed to model structure evolution and deformation kinetics on a semi-empirical basis is briefly discussed.
Vortices and Mixing in Metals during Severe Plastic Deformation
Authors: Beygelzimer Yan
Published: May 2011

We present a model of severe plastic deformation of metals under the assumption of turbulence in their representative volume element. It provides simple and natural answers to a number of questions at the border between mechanics of solids and materials science.
Process Design Concepts for the Production of Ultrafine Grained Steels through Multi-Pass Warm Rolling: Bridging Science and Technology
Authors: Narayana Murty S.V.S. , Torizuka Shiro
Published: May 2011

Steel bars having a cross section of 18mm square with uniform distribution of ultrafine ferrite grains were produced through a multi-pass warm caliber rolling process in a 0.15%C-0.3%Si-1.5%Mn steel. The average ferrite grain sizes of 0.43μ m, 0.70μ m and 1.2 μ m were obtained in the isothermal warm caliber rolling processes at 773K, 823K and 873K respectively. Even though caliber rolling results in inhomogeneous strain distribution, multi-pass caliber rolling to large cumulated strains of 2 or 3 can be uniformly introduced in to the bar samples. Strain accumulation due to the multi-pass warm deformations was confirmed by comparing microstructural evolution through the multi-pass deformations with that of single pass deformation. The size of ultrafine grains formed through warm deformation was found to depend on the Zener-Hollomon parameter. The similarity of the microstructural evolution with single pass deformation reveals that the multi-pass warm deformation is an effective method to obtain ultrafine grained ferrite structure in bulk materials. It is proposed that compressive strain-Z parameter plots along with grain size-Z parameter plots help in establishing the processing conditions for obtaining products with a desired microstructure and grain size. Finally, such “processing maps” developed for a variety of materials serve useful purpose in bridging the science and technology of developing bulk ultrafine grained materials in semi-finished / finished products.
Achievable Strength of Nanostructured Composites with Co-Deformable Components
Authors: Han Ke , Chen Jing Ping
Published: May 2011

Large amount of research has been undertaken on the effects of conventional thermomechanical treatment and chemistry variations on the mechanical properties of nanostructured bulk materials developed for wire rod and sheet products. The thermomechanical treatments are selected to refine as much as possible the microstructure to achieve high strength. In most of the cases, the alloy additions are deliberated added to be beneficial to the mechanical properties of the nanostructured materials, especially the tensile strength. In addition to refine the microstructure, both the thermomechanical treatments and chemistry variations may also alter the shape and distribution of the strengthening phases. This article describes the nanostructured composites with face-centered cubic (fcc) copper or body-centered cubic (bcc) ferrite as matrix and discusses several factors that affect the mechanical strength of such materials.
On the Cyclic Deformation Response and Microstructural Mechanisms of ECAPed and ARBed Copper - an Overview
Authors: Kwan Charles C.F. , Wang Zhi Rui
Published: May 2011

With the increase of interest in using ultra-fine and nano-grained metals for structural purposes, the need to build on the knowledge pool regarding the response and behaviour of those metals under a mechanical load becomes more vital. However, it is well known that, especially for this type of materials such as the ECAPed and ARBed materials, the thermo-mechanical history affects the mechanical behaviour of the product strongly. Although ECAP and ARB are different techniques under the category of severe plastic deformation, similarities in their cyclic deformation response is observed from time to time. Specifically, the microstructural mechanisms involved in accommodating cyclic plastic strain in these two types of materials is seemingly comparable. The similarities arise from the similar microstructures in the majority of the volume of the bulk. In this report, the cyclic deformation response, and the related microstructural mechanisms of ECAPed copper will be discussed first and those of ARBed second. A comparison between ECAPed copper and ARBed copper will then be performed. Furthermore, the differences due to the unique features of ARBed material will be discussed. Lastly, the reasons behind the observed similarities in cyclic deformation behaviour and the related micro-mechanisms for metals process with the two different techniques will also be explored.
Improvement of Fracture Toughness (K1c) of 7075 Al Alloy by Cryorolling Process
Authors: Das P. , Jayaganthan R. , Chowdhury T. , Singh Inderdeep
Published: May 2011

The effects of cryorolling (Rolling at liquid nitrogen temperature) and optimum heat treatment (short annealing + ageing) on fracture toughness of 7075 Al alloy are reported in the present work. The Al 7075 alloy was rolled for different thickness reductions (40% and 70%) at cryogenic temperature and its mechanical, fracture toughness properties were studied. The microstructural characterization of the alloy was carried out by using Optical microscopy and Field emission scanning electron microscopy (FESEM). The cryo-rolled (CR) Al alloy after 70% thickness reduction exhibits ultrafine grain structure as observed from its FESEM micrographs. It is observed that the yield strength and fracture toughness of the CR material with 70% thickness reduction have increased by 108% and 73% respectively, compared to the starting material. The CR 7075 Al alloy shows improved fracture toughness and tensile strength due to high dislocation density, grain refinement, and ultrafine-grain (UFG) formation by multiple cryorolling passes. The CR samples were subjected to short annealing for 5 min at 190 0C, 170 0C and 150 0C followed by ageing at 160 0C, 140 0C and 120 0C for both 40% and 70% reduced samples. The combined effect of short annealing and ageing improves the fracture toughness, tensile strength, and ductility of cryorolled samples, which is due to precipitation hardening and subgrain coarsening mechanism respectively. The scanning electron microscopy (SEM) fractographs of the Al 7075 alloy samples reveals that starting bulk Al alloy specimens is fractured in a total ductile manner, consisting of well-developed dimples over the entire surface and dimple size got decreased continuously for cryorolled specimens at different percentage of thickness reduction (40% and 70%) as observed in the present work.
Composition-Dependent Basics of Smart Heusler Materials from First- Principles Calculations
Authors: Entel Peter , Dannenberg Antje , Siewert Mario , Herper Heike C. , Gruner Markus E. , Buchelnikov Vasiliy D. , Chernenko Volodymyr A.
Published: May 2011

The structural and magnetic order are the decisive elements which vastly determine the properties of smart ternary intermetallics such as X2YZ Heusler alloys. Here, X and Y are transition metal elements and Z is an element from the III-V group. In order to give a precise prescription of the possibilities to optimize the magnetic shape memory and magnetocaloric effects of these alloys, we use density functional theory calculations. In particular, we outline how one may find new intermetallics which show higher Curie and martensite transformation temperatures when compared with the prototypical magnetic shape-memory alloy Ni2MnGa. Higher operation temperatures are needed for technological applications at elevated temperatures.
Crystal Structures of Modulated Martensitic Phases of FSM Heusler Alloys
Authors: Righi Lara , Albertini Franca , Fabbrici Simone , Paoluzi Antonio
Published: May 2011

Multifunctional ferromagnetic shape memory Heusler alloys are frequently characterized by structural modulation in martensitic phases. In particular, modulated martensitic phases, showing the higher magnetic field induced strain (MFIS) performance, are the most promising candidates for technological applications. Depending on the composition, as well as pressure and temperature conditions, this periodic structural distortion, consisting of shuffling of atomic layers along defined crystallographic directions, accompanies the martensitic transformation. Over the years, different Ni-Mn-Ga modulated martensitic structures have been observed and classified depending upon the periodicity of corresponding ideal nM superstructure (where n indicates the number of basic unit cells constituting the superlattices). On the other hand, it has been demonstrated that in most cases such structural modulation is incommensurate and the crystal structure has been fully determined by applying superspace formalism. The results, obtained by structure refinements on powder diffraction data, suggest a unified crystallographic description of the modulated martensitic structures, here presented, where every different “nM” periodicity can be straightforwardly represented.
Magnetic Microstructure Analysis of Ferromagnetic Shape Memory Alloys and Related Compounds
Authors: Murakami Y. , Kainuma Ryosuke , Shindo Daisuke , Tonomura Akira
Published: May 2011

We performed magnetic imaging of Ni-based ferromagnetic shape memory alloys. The magnetic microstructure was revealed by Lorentz microscopy and electron holography, which are powerful tools based on transmission electron microscopy. Observations of Ni51Fe22Ga27 and Ni50Mn25Al12.5Ga12.5 alloys, both of which have an L21-ordered structure in the parent phase, demonstrated that the antiphase boundaries (i.e., a type of planer defects) caused significant changes in the magnetization distribution due to depression of the atomic order—actually, the magnetization in these alloys depends upon the degree of chemical order. We propose a method which estimates the important magnetic parameters (the magnetocrystalline anisotropy constant and exchange stiffness constant) based on transmission electron microscopy observations. This method should be useful in magnetic measurements of nanometer-scale areas, for which conventional techniques cannot be applied.
Metamagnetic Shape Memory Effect and Magnetic Properties of Ni-Mn Based Heusler Alloys
Authors: Kainuma Ryosuke , Ito W. , Umetsu R.Y. , Khovaylo V.V. , Kanomata T.
Published: May 2011

In some Ni-Mn-In- and Ni-Mn-Sn-based Heusler-type alloys, martensitic transformation from the ferromagnetic parent phase to the paramagnetic martensite phase appears and magnetic field-induced reverse transformation, namely, metamagnetic phase transition, is detected. In this paper, the metamagnetic shape memory effect due to the metamagnetic phase transition and the magnetostress effect in the Ni-Co-Mn-In alloys are introduced and the phase diagrams of Ni50Mn50-yXy (X: In, Sn, Sb) alloys are shown as basic information. Furthermore, the magnetic properties of both the parent and martensite phases in the Ni-Mn-In- and Ni-Mn-Sn-based metamagnetic shape memory alloys are also reviewed.
Reverse Magnetostructural Transitions by Co and In Doping NiMnGa Alloys: Structural, Magnetic, and Magnetoelastic Properties
Authors: Albertini Franca , Fabbrici Simone , Paoluzi Antonio , Kamarad Jiri , Arnold Zdenek , Righi Lara , Solzi Massimo , Porcari Giacomo , Pernechele Chiara , Serrate David , Algarabel Pedro
Published: May 2011

We review the composition dependence of the structural and magnetic properties of the Co-doped Ni–Mn–Ga Ferromagnetic Shape Memory Alloy around the Mn-rich composition Ni50Mn30Ga20. The presence of Co affects the critical temperatures and alters the exchange interactions of martensite and austenite to different extents; by varying the composition it is possible to tune the critical temperatures and to induce a “paramagnetic gap” between the magnetically ordered martensite and magnetic austenite, thus giving rise to a reverse magnetostructural transformation. The magnetic and structural properties display noticeable discontinuities across the martensitic transformation: remarkable values of the saturation magnetization jump at the transformation (DM), of the field dependence of the martensitic transformation temperature (dTM/dH), and of the crystalline volume change (DV/V) are reported, and are considerably enhanced by additional Indoping of the quaternary alloy. These properties give rise to a remarkable phenomenology which is of interest for multifunctional applications; magnetic superelasticity and high values of reversible strain are found.
Long-Term Cyclic Loading of 10M Ni-Mn-Ga Alloys
Authors: Aaltio Ilkka , Söderberg Outi , Ge Yan Ling , Hannula Simo Pekka
Published: May 2011

Martensitic 10M Ni-Mn-Ga single crystals are usually applied in the magnetomechanical actuators. Their behavior in the long-term cycling and the factors influencing upon are thus important to know. There are several publications concerning this. However, consistent statistical data is still missing to large extent. In this report we review and analyze the data available in the literature. In conclusion it can be stated that 10M Ni-Mn-Ga single crystals survive well in long-term actuation (millions of cycles) when the frequency of twin variant reorientation is not exceeding 250 Hz, and the strain used in actuation is below 3 %. There are several factors influencing the long-term behavior and these are discussed in more details in this work.
Surface Study of Ni2MnGa(100)
Authors: D'Souza S.W. , Dhaka R.S. , Rai Abhishek , Maniraj M. , Nayak J. , Singh Sanjay , Schlagel D.L. , Lograsso T.A. , Chakrabarti Aparna , Barman S.R.
Published: May 2011

The (100) surface of Ni2MnGa ferromagnetic shape memory alloy exhibits intrinsic surface property dissimilar to the bulk as well as influence of compositional variation at the surface. It is shown that by sputtering at room temperature and annealing at high temperature, it is possible to obtain a clean, ordered and stoichiometric surface. However, for even higher annealing temperatures, the surface becomes Mn rich. The (100) surface of Ni2MnGa is found to have Mn–Ga termination. A surface reconstruction to p4gm symmetry is observed in the austenite phase, while the expected bulk truncated symmetry at surface is p4mm. For the stoichiometric surface, the XPS valence band is compared with our calculations based on first principles density functional theory and good agreement is obtained. The ultraviolet photoelectron spectroscopy (UPS) valence band spectra depend sensitively on composition varying from Ni rich to Mn rich surfaces. A satellite feature observed in both Ni 2p core-level and valence band spectra is related to the narrow 3d valence band in Ni2MnGa.
Magnetic Anisotropy of Ferromagnetic Martensites
Authors: L'vov Victor A. , Chernenko Volodymyr A.
Published: May 2011

The analytic survey of experimental and theoretical studies of the magnetic anisotropy of ferromagnetic shape memory alloys (FSMAs) is presented. The interdependence between the magnetic anisotropy of FSMAs, their lattice parameters, microstructure, and magnetostrain properties is considered. The temperature dependencies of the magnetocrystalline anisotropy energy density (MAED) and magnetically induced mechanical stress are described in the framework of magnetoelastic model based on Landau theory of phase transitions. The magnetic anisotropy of thin martensitic platelets/films and wires is considered. The effect of compensation of magnetocrystalline anisotropy by the magnetostatic one is studied. The reduction of MAED as a result of internal twinning of single crystal is discussed. The possibility of observation of reversible magnetic-fieldinduced strain in the twinned FSMAs with reduced MAED is demonstrated.
Entropy Changes in Ferromagnetic Shape Memory Alloys
Authors: Cesari Eduard , Salas Daniel , Kustov Sergey
Published: May 2011

Several features of the entropy change S related to the martensitic transformation (MT) in metamagnetic alloys are discussed. In these alloys a change in magnetic order is concomitant with the MT, as it occurs between ferromagnetic austenite and non-magnetic (weakly magnetic) martensite. In this case it has been shown that S strongly decreases as the MT temperature range go far below the Curie temperature of austenite. The behavior of S can be understood considering the different signs of the lattice and magnetic contributions to the total entropy change. It has been shown that the so called kinetic arrest of the MT is directly related to the decrease of S, which in the limit S → 0 leads to the suppression of the driving force for the transformation.
Stress-Temperature Phase Diagram of Ni2MnGa and Structural Relations between its Constituent Phases
Authors: Fukuda Takashi , Terai Tomoyuki , Maeda Hidefumi , Kakeshita Tomoyuki
Published: May 2011

The ferromagnetic shape memory alloy Ni2MnGa exhibits a successive martensitic transformation from the L21-type structure to the so-called intermediate phase and then to the martensite phase with an incommensurate structure during cooling under zero stress. In addition to these phases, a new phase, which we call the X-phase, appears when Ni2MnGa is cooled under compressive stress applied in the [001] direction. In this paper, we discuss the structural relations between the X-phase and the other phases on the basis of experimental results of compressive tests, transmission electron microscope observations and neutron diffraction patterns. It is likely that a multicritical point exists in the stress-temperature phase diagram of Ni2MnGa.
Neutron Diffraction Studies of Magnetic Shape Memory Alloys
Authors: Barandiarán José M. , Gutiérrez Jon , Lázpita Patricia , Feuchtwanger J.
Published: May 2011

The characteristics of neutron diffraction applied to the study of Ferromagnetic Shape Memory Alloys are revised. Main studies refer to crystal structure, preferential site occupancy, variant reorientation and magnetic moment distribution in the alloys
Influence of Long-Range Atomic Order on the Structural and Magnetic Properties of Ni-Mn-Ga Ferromagnetic Shape Memory Alloys
Authors: Sánchez-Alarcos Vicente , Pérez-Landazábal José Ignacio , Recarte Vicente
Published: May 2011

This chapter presents a review of the most recent and systematic works performed on the study of the effect of atomic order on the structural and magnetic properties of Ni-Mn-Ga ferromagnetic shape memory alloys. It is shown that a correlation between long-range atomic order and the martensitic and Curie temperatures can be established from the analysis of its evolution under high and low temperature thermal treatments. In particular, it is demonstrated that, irrespectively of the thermal treatment, both transformation temperatures increase with the increasing L21 atomic order degree, showing practically the same linear dependence on the nextnearest- neighbors atomic order parameter, in such a way that the effect of the atomic order on the relative stability between austenite and martensite can be quantitatively determined. In this respect, it is shown that the effect of atomic order on the martensitic (and also the premartensitic) transformation is directly related to the variation of the magnetic exchange coupling.
Iso-Conversional and Isokinetic Methods of Analysis of Non-Isothermal Crystallization in Ti50Cu20Ni30 Metallic Glass
Authors: Dhurandhar Heena , Shanker Rao T. Lilly , Lad Kirit N. , Pratap Arun
Published: May 2011

The crystallization kinetics of metallic glass Ti50Cu20Ni30 has been studied using Differential Scanning Calorimetry (DSC). The DSC thermograms have been analysed using the model-free isoconversional methods and model dependent isokinetic methods. The activation energy(E) for the crystallization process has been determined utilizing; (i) various linear integral isoconversional methods, namely, Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose, Li Tang method (ii) linear differential isoconversional method and (iii) different isokinetic methods. In the present work, we intend to the determination of true value of E. The above methods are found to give consistent results for E.
Glass Forming Ability of Ca-Based Bulk Metallic Glasses
Authors: Patel Ashmi T. , Lad Kirit N. , Pratap Arun
Published: May 2011

Knowledge of glass forming ability (GFA) of amorphous metallic alloys is very important from both theoretical and practical point of view. Thermodynamically, the Gibbs free energy difference, ΔG between the undercooled liquid and the corresponding crystalline state is driving force for crystallization. As a consequence, it is a good indicator for glass forming ability of metallic glasses. A novel expression for ΔG has been used to estimate the GFA of recently developed Ca-based bulk metallic glasses viz. Ca53Mg23Cu24,Ca65Mg15Cu20,Ca40Mg25Cu35, Ca50Mg22.5Cu27.5 and Ca55Mg15Cu30. Different GFA criteria are also evaluated for systems taken up in the study and effect of addition of variation in composition of Ca-Mg-Cu system is also investigated. Present work suggests that among different GFA criteria, ΔG is the best criterion for the prediction of GFA for Ca-based bulk metallic glasses.
Organic Light Emitting Diodes: Effect of Annealing the Hole Injection Layer on the Electrical and Optical Properties
Authors: Predeep P. , Shahul Hameed T.A. , Aneesh J. , Baiju M.R.
Published: May 2011

Organic Light Emitting Diodes (OLED) are receiving increased attention due to tremendous application potential these devices hold in the areas of large area displays and lighting applications. However, the problems of efficiency, stability and shelf life are major challenges for making OLEDs an attractive alternative. The simple device structure involving anode, emissive layer and cathode is no longer the norm. Recently, various buffer layers like Hole Injection Layer (HIL), Hole transport Layer (HTL), Electron Injection Layer (EIL), Electron Transport Layer (ETL) etc. are being widely used as integral parts of the OLED architecture to enhance the performance parameters. The nomenclature of these layers is often confusing and sometimes used by different authors to mean different layers and a common and universal nomenclature for layers is still wanting. Applying a buffer layer, often called as the hole injecting layer (HIL) between anode and emissive layer is a general technique for increasing the efficiency and stability of organic light emitting diodes. Poly- (3,4-ethyhylene dioxythiophene): poly- (styrenesulphonate) (PEDOT:PSS) is a very common and popular such HIL used in OLEDs. In this chapter, a basic structure of OLEDs has been discussed in perspective with this HIL material and the effect of annealing this PEDOT: PSS layer on the characteristics of the device at different temperatures ranging from 100°C to 300°C in vacuum. Devices fabricated in clean room conditions are characterized for their electrical and optical properties. Equivalent circuits of the devices are deduced using impedance spectroscopy and discussed. Surface morphology of the HIL layers using atomic force microscopy (AFM) provides reasons for the variation of the device properties with the annealing of HIL.
Corrosion and Oxidation Behavior of Ti-Based Amorphous and Nanocrystalline Alloys
Authors: Sharma S.K.
Published: May 2011

Amorphous alloys, in general, exhibit superior mechanical and chemical properties as compared to their crystalline counterparts, which is attributed to their chemical homogeneity and to the absence of crystal-like structural defects. Nanocrystalline and fully crystallized forms of these alloys can be easily obtained by a suitable thermal annealing treatment. It is important to have the knowledge of corrosion/oxidation behavior of amorphous and nanocrystalline alloys for various possible applications. In contrast to many investigations on corrosion and oxidation behavior of amorphous alloys reported in the literature, only limited studies have been carried out on comparison of corrosion/oxidation behavior of amorphous and nanocrystalline states of the same alloy. With this motivation potentiodynamic polarization studies were carried out on amorphous and nanocrystalline states of the alloy Ti60Ni40 in several aqueous media at room temperature. The oxidation in air was also investigated in the temperature range 2800C-3800C using a thermogravimetric analyzer. It was found from these investigations that nanocrystalline state exhibits the maximum corrosion/oxidation resistance in comparison to amorphous and crystalline states. The better corrosion/oxidation resistance of nanocrystalline state can be explained in terms of the nature of the nanocrystalline phase/phases and the size of the crystallites. The results of the present study are supported by other similar studies reported in the literature. A short review on comparison of corrosion/oxidation behaviour of amorphous and nanocrystalline Ti-based alloy is also presented in the paper.
Influence of Co Doping on Structural and Magnetic Properties of Fe2P
Authors: Kumar Sudhish , Krishnamurthy Anjali , Srivastava Bipin K.
Published: May 2011

The aim of this article is to provide an overview on the effect of Co doping for Fe in Fe2P on the lattice parameters, magnetic transition point, saturation magnetic moment, paramagnetic Curie point and paramagnetic moment. Five alloys in the series (Fe1-xCox)2P (x= 0.03, 0.10, 0.30, 0.50, 0.70) were synthesized and investigated using X-ray diffraction, magnetization and paramagnetic susceptibility measurements. Alloys with x=0.03 and 0.10 crystallize in Fe2P type hexagonal structure while those for x= 0.30, 0.50, 0.70 crystallize in Co2P type orthorhombic structure. In the hexagonal phase, the substitution of Co for Fe leads to a very little enhancement in the unit cell volume but in the orthorhombic phase the increase in Co concentration leads to monotonic decrease in the unit cell volume. All the five alloys are ferromagnetically ordered and  display nonlinearity in the -1-T curves above Tc. Interestingly, the compounds for x= 0.10, 0.30 and 0.50 shows a sharp first order type ferromagnetic to paramagnetic phase transition. The paramagnetic Curie temperature (θP) increases up to x=0.50. The saturation magnetizations and paramagnetic moments monotonically decrease with the increase in the Co concentration. Both Ni and Co substitution for Fe in Fe2P are known to strengthen the ferromagnetic ordering, however, the effect of Co substitution has stronger influence on the structural parameters and magnetic properties than the Ni. The observed nonlinearity in the -1-T curves above Tc and the Rhodes- Wohlfarth ratio (μP/μs) greater than one, gives a clear evidence of presence of large magnetic correlations far above Tc and itinerant magnetism in these compounds.
Lack of Peripheral Memory B Cell Responses in Recovered Patients with Severe Acute Respiratory Syndrome: A Six-Year Follow-Up Study
Authors: Tang Fang , Quan Yan , Xin Zhong-Tao , Wrammert Jens , Ma Mai-Juan , Lv Hui , Wang Tian-Bao , Yang Hong , Richardus Jan H. , Liu Wei , Cao Wu-Chun
Published: May 2011

Six years have passed since the outbreak of severe acute respiratory syndrome (SARS). Previous studies indicated that specific Abs to SARS-related coronavirus (SARS-CoV) waned over time in recovered SARS patients. It is critical to find out whether a potential anamnestic response, as seen with other viral infections, exists to protect a person from reinfection in case of another SARS outbreak. Recovered SARS patients were followed up to 6 y to estimate the longevity of specific Ab. The specific memory B cell and T cell responses to SARS-CoV Ags were measured by means of ELISPOT assay. Factors in relation to humoral and cellular immunity were investigated. Six years postinfection, specific IgG Ab to SARS-CoV became undetectable in 21 of the 23 former patients. No SARS-CoV Ag-specific memory B cell response was detected in either 23 former SARS patients or 22 close contacts of SARS patients. Memory T cell responses to a pool of SARS-CoV S peptides were identified in 14 of 23 (60.9%) recovered SARS patients, whereas there was no such specific response in either close contacts or healthy controls. Patients with more severe clinical manifestations seemed to present a higher level of Ag-specific memory T cell response. SARS-specific IgG Ab may eventually vanish and peripheral memory B cell responses are undetectable in recovered SARS patients. In contrast, specific T cell anamnestic responses can be maintained for at least 6 y. These findings have applications in preparation for the possible reemergence of SARS.