Showing papers in "Materials Technology in 2011"

Magnetic sensors for data storage: perspective and future outlook

Abstract: Sensors based on various magnetic principles and mechanisms are gaining wide acceptance in the data storage industry. The focus here is to make a comparative analysis of the practice and properties of current and past magnetic recording systems. Both longitudinal magnetic recording and perpendicular magnetic recording are addressed in the context of the media and magnetic sensors used in the recording head. An outlook for future data storage, such as patterned media and heat assisted recording, is also presented.

Rhodamine based bright red colourimetric and turn-on fluorescence chemosensor for selective detection of Cu2+

Abstract: Copper is one of the essential trace nutrients in biological systems. Apart from its biological role, copper is predominantly being used in ceramics, alloys, household utensils, electrical wires, fertiliser preparation and in various engineering purposes, owing to its high malleability, electrical conductivity and antibacterial activity. Such widespread use leads to accumulation of copper in the environment, which subsequently gets into the human body. Therefore, environmental and biological detection of copper is necessary to assess its concentration levels. We have developed 4-(diethylamino)-salicylaldehyde rhodamine hydrazone ligand 1 as a naked eye chemosensor for Cu2+ with enhanced turn-on fluorescence emission in the longer wavelength region that works even in aqueous media. The observed turn-on colourimetric and fluorescence emission upon binding of ligand 1 to Cu2+ was attributed to the ring opening of spirolactam moiety and the strong coordination ability of ring opened form to t...

Application of carbon filament (CF) for structural health monitoring of textile reinforced thermoplastic composites

Abstract: Textile reinforced composites are a leading trend in lightweight structure design. The demand for additional function integration for the online health monitoring of lightweight structures using multimaterial design is growing rapidly. Carbon filament (CF) seems to be the simplest, most cost effective and most durable functional element for use in textile reinforced composites as a strain sensor. This paper reports on the production of functional hybrid yarn made with DREF-2000 friction spinning using CF yarn as the core component and polypropylene fibres as the sheath component. A comparative study was performed on the suitability of friction spun hybrid yarn and as spun CF yarn (i.e. in the form received from the manufacturer). The differences in electromechanical characteristics were analysed specifically for glass/polypropylene thermoplastic composite applications. Moreover, various types of connectors of CFs were also investigated.

Characterisation of piezoelectric PVDF monofilaments

Abstract: The piezoelectric effect of poly(vinylidene fluoride) is demonstrated in monofilaments These fibres produce electrical signal upon mechanical deformation The structure of the monofilaments is analysed by wide angle X-ray diffraction and differential scanning calorimetry, whereas the crystalline fraction mainly consists of the piezoelectric β phase For polarisation and electromechanical characterisation, poly(vinylidene fluoride)-epoxy composites are manufactured, whereas all the filaments are aligned parallel to the composite structure The electric signal is two magnitudes of order larger for the polarised samples compared to the unpolarised ones Furthermore, there is a clear anisotropy, allowing the direction dependent measurement of stress and strain Mechanical stress in the fibre direction produces a much larger signal compared to the same stress in the perpendicular direction

Micromagnetic modelling of new generation of FePt and FeRh nanostructures for heat assisted magnetic recording

Abstract: High magnetocrystalline anisotropy FePt can be considered to be a potential candidate for increasing the areal recording density up to ∼1 Tb in−2. The writing head fields available are not adequately high for magnetic reversal (writing) because of the high coercivity of FePt. However, by uniquely combining FePt and FeRh, we can overcome the writing field limitation in the heat assisted magnetic recording approach. In this regard, we describe individually simulated FeRh and FePt nanodot cuboids and comparison of the data with the experimental observations made on FePt and FeRh nanoparticles. Furthermore, the hysteresis behaviour of FeRh/FePt bilayer cuboids was simulated with different values of the exchange constants, and the dependence of coercivity on the exchange constant was examined. The FePt/FeRh bilayer cuboids experienced a typical two-stage magnetic reversal, and the effects of the exchange constants on the reversal and coercive fields were examined.

Surface modification of conductive PEDOT coated textile yarns with silicone resin

Abstract: Electroactive textile fibres and fabrics have been used in smart and interactive clothing for medical,military and sports applications. The improved surface properties of conductive textiles are re ...

Carbon nanotube coated glass fibres for interphase health monitoring in textile composites

Abstract: In this study, a novel approach for health monitoring in textile composites is reported. Coating glass fibre (GF) yarns with a carbon nanotube (CNT) filled film former results in the formation of electrically conductive paths on the GF surface. By embedding the CNT modified yarns into a polypropylene matrix, a functional interphase is created which can be used for highly localised health monitoring in textile composites. The health monitoring is based on the resistance change of the percolated CNT network in the composites interphase due to applied external stresses. The interphase sensor can be used for an indirect measurement of interphase strain as well as for the determination of the accumulated interphase damage during mechanical loading. Moreover, the system is sensitive to the breakage of the reinforcement fibres.

Electrical circuit model of elastic and conductive yarns produced by hollow spindle spinning

Abstract: The implementation of electronic textiles which are capable of being applied as electrodes, sensors or heating elements is crucial in several fields of application, ranging from automotive to sports, from rehabilitation to art and design. However, current electronic textiles often suffer from poor mechanical properties, low drape and unstable electroconductive characteristics. One possibility to overcome these shortcomings is to introduce the electroconductive properties at a fibre or yarn level by combining traditional fibres and yarns with metal wires or metalised yarns. In this paper, we describe the production of multicomponent yarns which combine electroconductive properties with elasticity, drape and mechanical strength. We discuss the electroconductive properties of the yarns produced with hollow spinning technology. An electrical model based on Kirchhoff’s law was designed and validated with the abovementioned measurements.

Effects of sputtering pressure on properties of copper oxide thin films prepared by rf magnetron sputtering

Abstract: Copper oxide thin films produced by rf magnetron sputtering on glass substrates have been characterised by XRD, SEM, AFM, spectrophotometer and four-point probe measurements. It is shown that process parameters can be varied to produce films of varying compositions, and optical and electrical properties. Depositions at 200 W power and an oxygen flowrate of 2 sccm in particular are found to favour the formation of single phase cuprous oxide. The optical and electrical properties of the films prepared under the stated conditions are of potential interest for application in semiconducting materials.

Techniques related to graphene biosensors and their potential combination with optical fibres

Abstract: From zero-dimensional fullerene to one-dimensional carbon nanotube and to two-dimensional graphene, nanostructures based on carbon element are always one of the most exciting topics in modern science and technology. The work published in the open literature dealing with the properties, synthesis and sensor applications of graphene is overviewed. The potential techniques to realise optical fibre graphene sensors are presented and discussed.

Simulation of plasma potential and ion energies in magnetron sputtering

Abstract: From experimental findings of magnetron sputtering processes, it is well known that the flux and energy distribution of ions at the substrate strongly depend on the operation mode of the electric power source. In reactive magnetron sputtering processes, this has a major impact on the properties of deposited films such as morphology, crystalline structure and etching behaviour. Thus, in the development of coated products with improved properties, it is an issue to maintain a tailored and reproducible ion energy distribution at the substrate in industrial sputtering coaters. We address this issue via particle-in-cell Monte-Carlo (PIC-MC) simulations on a two-dimensional cross-sectional model of magnetron sputter sources within our in-line sputter coater, whereas DC, MF and RF mode are assumed as different power supply operation modes. For each mode, the simulations reveal the relevant ion creation mechanisms as well as the formation of the electric potential distributions. From the simulatio...

Application of AFM for identification of fibre surface changes after plasma treatments

Abstract: The application of low pressure argon and oxygen plasma treatment as an eco-friendly process of Lyocell textile modification was investigated. Using atomic force microscopy, the changes in nanomorphology induced by plasma treatments were recorded. The chemical groups of the outer fibre layer treated with plasmas and silver compounds (AgNO3 and AgCl) were analysed using Fourier transform infrared-attenuated total reflectance spectroscopy. The viscosimetric method was used to determine possible changes of the cellulose polymer molecular weight after plasma treatments. The experimental results provided data useful for better understanding the art of plasma action on the fibre surface, depending on the nature of gases. They also indicate different mechanisms of silver nanoparticle binding and their distribution on the surface of the treated Lyocell fabric, depending on the parameters of the applied plasma process.

Effects of free quartz on mechanical behaviour of kaolinite based geopolymers

Abstract: Quartz is usually detected as an impurity of kaolinite clays. The present work attempts to evaluate the role and behaviour of quartz particles in geopolymerisation and its probable effects on mechanical behaviour of geopolymeric products. Two kaolinite clays with different free quartz contents were used as raw materials to produce geopolymers. Results showed that using high content quartz kaolin causes higher compressive strength. Scanning electron microscopy studies confirmed that quartz does not participate in geopolymerisation and completely remains in the structure as fine particles. High hardness quartz particles by retarding crack growth in the geopolymer matrix enhance mechanical behaviour of the samples. Changing the calcination temperature of starting kaolins also showed that strength of geopolymer gel is the most important factor influencing the compressive strength of geopolymers. The positive effect of quartz particles on compressive strength for kaolins calcined at 750°C was m...

Pulsed DC reactive magnetron sputtering of vanadium dioxide thermochromic thin films

Abstract: Vanadium oxides are an important class of materials with a large diversity of physical and chemical properties which derive from a range of single or mixed valences and a large variety of structures. They are already being used in many technological applications such as electrical and optical switching devices, light detectors, temperature sensors, etc. There has been a great interest in a particular phase, VO2(M), due to its thermochromic behaviour near room temperature which allows the development of smart windows with active control of the solar spectrum, for energy efficiency purposes. However, stoichiometric VO2 is difficult to deposit because of a narrow stability range due to the complex vanadium-oxygen reactive system. In this work, vanadium oxide thin films were synthesised on glass substrates by reactive pulsed direct current magnetron sputtering from a vanadium metal target in an O2/Ar atmosphere. Different processing conditions have been chosen in order to evaluate their influ...

Investigation and application of high strength low alloy wear resistant cast steel

Abstract: A kind of low alloy wear resistant cast steel that does not contain costly alloy elements such as molybdenum, nickel, copper and vanadium has been successfully developed By the refinement with rare earth and titanium, the purification with blowing argon and improving the hardenability with boron, the cast steel containing 0·25-0·45%C, 0·5-1·5%Si, 0·5-1·5%Mn, 0·5-1·5%Cr and a small quantity of titanium, boron, rare earth, calcium and aluminium has high tensile strength, impact and fracture toughness and excellent wear resistance In the excavator bucket teeth, crusher hammer and ball mill liner, low alloy wear resistant cast steel has 2-4 times longer servicing life than that of Hadfield austenitic steel, and its production cost is equal to that of Hadfield austenitic steel The use of low alloy wear resistant cast steel is safe and reliable, and there is no fracture and scaling in the use The application of low alloy wear resistant cast steel has good economic and social benefits

Emergence of (001) preferred orientation in AlN film using ultrathin intermediate Pt layer

Abstract: The preferred orientations of AlN films with an intermediate Pt layer have been examined using X-ray diffraction and transmission electron microscopy. It is found that the Pt layer encourages the AlN film into c axis preferred orientation deposition, even though the sputtering conditions would normally lead the AlN film to be deposited with other preferred orientations. The Pt layer also promotes the crystallisation of AlN films. The local epitaxial growth of AlN (001) on Pt (111) may elucidate the effect of the Pt layer on the preferred orientation control.

Evaluation of the Strength Variation of Normal and Lightweight Self-Compacting Concrete in Full Scale Walls

Abstract: M. M. Ranjbar1, M. Hosseinali Beygi2, I. M. Nikbin3 , M. Rezvani4, A. Barari5 1Department of Civil Engineering, Guilan University, Rasht, Iran 2Department of Civil Engineering, Babol University of Technology, Babol, Iran 3Department of Civil Engineering Islamic Azad University, Rasht Branch, Rasht 4Institute of Material Science, University of Duisburg-Essen, Universitatstrasse 15, 45141 Essen, Germany 5Department of Civil Engineering, Aalborg University, Sohngardsholmsvej 57, 9000 Aalborg, Aalborg, Denmark ab@civil.aau.dk, amin78404@yahoo.com

New method for preparation of luminescent lanthanide materials BaMoO4:Eu3+

Abstract: A new solid state synthesis method, called the high temperature ball milling (HTBM) method, was developed for the production of high performance single phase BaMoO4:Eu3+ phosphor powders. In this work, X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques and emission spectra test were used to characterise the obtained phosphor powders. Compared with chemical precipitation method often employed for the synthesis of phosphors interested, the HTBM method not only decreased the solid synthesis temperature from 1000 to 600°C, but also enhanced the emission intensity of yielded phosphors in the red light region by 48%. Additionally, BaMoO4:Eu3+ red phosphor powders produced by the HTBM method have relatively small and more uniform particle sizes. The HTBM method thus opens a new path to solid state synthesis, especially for the materials difficult to obtain at low temperature.

Microtool coatings using magnetron sputtering

Abstract: This paper presents a deposition process for hard coatings on micromachining cutting tools using closed field unbalanced magnetron sputter ion plating. Any microtools with diameters in the range 0·1-0·5 mm can be coated using this deposition method, with uniform, smooth and ‘defect free’ surface morphology on the cutting corner areas. The coatings, consisting of single or multiple transition metal nitrides or carbonitrides, have also been deposited on the flat, hardened tool steel samples and are shown to have the desirable properties of high hardness, good adhesion and high wear resistance. Evaluation of the coatings and coated microtools is carried out using scanning electron microscopy, microhardness, Rockwell diamond scratch and indentation, and pin-on-disc measurements. Mechanical micromilling is used to test the coatings on WC-Co solid micromills, dry cutting hardened H13 die steel. The results show that this deposition process is capable of producing a range of hard coatings on micr...

Electrical and electromechanical properties of alumina/natural rubber STR 5L composites

Abstract: The influence of micrometre-sized inorganic alumina particles embedded in a natural rubber (NR) on its electrical and electromechanical properties was investigated. Scanning electron micrographs and X-ray diffraction patterns show that the alumina (Al2O3) particles are moderately dispersed within the NR matrix. Without an electric field, the Al2O3 particles merely act as a filler to absorb or store an additional stress. The storage modulus increases by nearly a factor of 4 as the alumina volume fraction is varied from 0 to 0·009. With an electric field on, the ionic and the orientation polarisations and induced dipole moments were generated, leading to interparticle interactions, and an additional increase in the storage modulus; the storage modulus sensitivity at the electric field strength of 2 kV mm−1 varied from 0·10 to 0·20 within the same volume fraction range.

Rotatable magnetron sputtering: downscaling for better understanding

Abstract: In coating applications, magnetron sputtering is frequently the technology of choice. In industrial continuous in-line sputtering processes, such as web coating and glass coating, rotatable magnetrons have, to a large extent, supplanted the more classic rectangular sputter magnetrons and constitute the heart of many coating systems with target lengths up to 4 m. However, for many people in the coating business, rotatable magnetrons are quite unknown. When comparing the two types, it looks as if rotatable magnetrons offer significant advantages over planars, as long as the required cylindrical targets are available. Rotabable magnetrons are still a relatively new technology, and have not been fully investigated on a lab scale due to the lack of availability of small systems. Experiments with an in house developed downscaled rotatable magnetron have allowed some of their typical characteristics to be identified. Especially in reactive sputtering, rotatable magnetrons exhibit unusual properti...

Pulsed DC sputtered DLC based nanocomposite films: controlling growth dynamics, microstructure and frictional properties

Abstract: Surface smoothness of diamond-like carbon based thin films becomes a crucial property for developing nearly frictionless protective coatings. Surface roughness and the dynamic growth behaviour of TiC/a-C nanocomposite films, deposited by non-reactive pulsed DC (p-DC) sputtering of graphite targets, were studied using atomic force microscopy and cross-sectional scanning electron microscopy. Upon increasing the intensity of concurrent ion impingement by raising the frequency of p-DC sputtering, a transition from dynamic roughening to dynamic smoothing was revealed, leading to a transition from a strong columnar to a columnar free microstructure. It was shown that smooth films can be deposited on initial rough surfaces at a higher pulse frequency (350 kHz). Also dense, tough, ultrasmooth and ultralow friction TiC/a-C:H nanocomposite films were successfully deposited on industrial polished steel substrates by reactive p-DC sputtering of Ti targets at 350 kHz frequency in an argon/acetylene atm...

Continual development keeps reactive sputter deposition at the forefront of surface engineering processes

Abstract: (2011). Continual development keeps reactive sputter deposition at the forefront of surface engineering processes. Materials Technology: Vol. 26, No. 1, pp. 1-2.

Microwave assisted hydrothermal synthesis of hierarchical structured ZnO nanorods

Abstract: ZnO nanorods with hierarchical structures were prepared using the micowave hydrothermal method. The structure, morphology and the crystalline phase of the synthesised nanorods were characterised using X-ray diffractometer, field emission scanning electron microscopy equipped with energy dispersive X-ray analysis, high resolution transmission electron microscopy, and fluorescence spectrometer respectively. The experimental results showed that the hierarchical structured ZnO nanorods have an average diameter ∼400 nm, the thorn-like nanostructures grown on the surface of nanorods in high density have different length from about 10 to 80 nm, and approximately in a diameter of 20 nm respectively. The photoluminescence spectrum exhibited that the hierarchical structured ZnO nanorods have a strong green band emissions at 415 and 465 nm respectively. The photocatalytic experiment results shown that the as prepared ZnO hierarchical structured nanorods exhibit excellent photocatalytic activity becau...

Mullite fibre preparation by extrusion method using alumina sol as binder

Abstract: Long fibres of mullite were prepared by extrusion method using kaolin, with alumina sol as a binder. The alumina sol was synthesised from dissolution of aluminium in aluminium chloride solution. Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy were used to characterise the properties of the precursor and ceramic fibres. The precursor fibres completely transformed to mullite at 1600°C for 2 h, and dense fibres were obtained at 1600°C for 10 h.

Microstructure and wear behaviour of WC-steel composite cladding

Abstract: WC-steel composite coatings were deposited on the ASTM 1045 steel substrates by modified arc spraying and then remelted on gas tungsten arc welding. The wear behaviours of the cladding were examined by an MM-200 tester at room temperature with the same condition. The microstructures, phase compositions and worn surface morphologies of the coatings were observed by optical microscope, X-ray diffractometer and SEM respectively. The wear mechanism of the cladding was discussed as well. The results show that the coating deposited by modified arc spraying consisted of Fe-Cr, Fe-Ni and WC particles and mechanically bonded with the substrate. The remelted cladding is compact with fewer defects and metallurgical bonded with the substrate. The cladding with 35 wt-%WC whose wear mass loss is minimum has the best wear resistance. Its dominant wear mechanism is mainly slight cutting and spalling. It is slight spalling and heavy cutting for the cladding with 25 wt-%WC content and spalling for that with...

Functionalisation of solid material surface with functional protein molecules for bioelectronic properties

Abstract: Molecularly functionalizations of electrodes, including semiconductors, open new function and application. Especially in cases of a molecular electronic materials with molecular-catalyst and electrochemical reaction, functional connection between molecule and electrode is a key part of whole process to provide device function. In the case of such the man-made molecular-catalytic electrochemical reaction systems, there are two interfaces on an electrode; a solution phase-enzyme layer interface and an enzyme layer-electrode interface. These interfaces act as a chemical reaction (including enzymatic reaction) interface and a physicochemical reaction interface respectively. There are late-limits in both interfaces. The interfacial rate limits become conspicuous in cases of macro-molecular interface, as such as enzyme. In order to break down the interfacial rate-limits, the molecular interfaces have to be designed as optimized both physical structure and chemical structure. In the present manus...

Contact reliability in ohmic microswitches

Abstract: The contact reliability issue in ohmic radio frequency microelectromechanical system switches is particularly challenging due to their low actuation force (the contact/restoring force is typically on the scale of 100 μN or less) and small device geometry (the typical dimensions are from 1 to 100s μm). As a result of the low actuation force, the breaking surface adsorbed film becomes difficult; thus, the contact resistance is extremely sensitive to surface condition in the contact area. In addition, a low restoring force during switch operation could cause stiction issue, especially for pure gold microcontacts. In addition, due to the fundamental scaling law, the risk of applying current or voltage to microswitches becomes much larger due to worsened heat constriction and enhanced electrical field in the microscale structures. In this article, we review recent experimental efforts to address these issues so that an improved understanding of the contact reliability in ohmic microelectromecha...