To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure no-reply@cambridge.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Tata is a household name in India. Starting well over a century ago, the Tatas began their foray into industry, and the brand represents more than a diversifed conglomerate. The Tatas are well-respected, having endeared themselves in every walk of Indian life. Their businesses are all-pervasive, from building automobiles and generating electric power to making steel and building supercomputers. Their charitable trusts and endowments are as extensive as their businesses. They have founded and funded outstanding educational institutions and human welfare organizations, and they have supported research on alleviating human suffering. The incumbent of the Tata Group is Ratan Naval Tata, a Cornell University graduate in architecture. In the 20 years since he took over the mantle, he has set the Tata industries on a steep growth trajectory, increasing the revenue of the Tata industries 12-fold, making automobiles—the famed Nano—available at very affordable prices in India, and introducing effcient steelmaking. The business empire he heads, the Tata Group, has over 90 companies with footholds in 80 countries. In the midst of his busy globe-trotting schedule, we managed to steal an hour of his time at the Tatas' “Bombay House” headquarters for him to tell us how he sees the global energy challenges and the opportunities they create.
Extensive research activity is currently devoted to controlled drug delivery systems, mainly as nano-sized particles. Although biocompatible and (bio)degradable polymers play a key role in this field, their shaping into colloidal particles (e.g., polymeric micelles and nanoparticles) usually requires the proper design of amphiphilic copolymers as effective stabilizers. Strategies for synthesizing these copolymers that preserve the intrinsic properties of the constitutive polymers are discussed in this article. Synthesis of amphiphilic copolymers with a more complex structure and endowed with functionality is also considered, with the purpose of enhancing the performance of the nanocarriers. The focus is increasingly on nanocarriers of the third generation, which resist coalescence and elimination by the immune system, and which are readily incorporated into chosen target cells. The more recent quest is for smart nanocarriers that exhibit the additional capacity of being stimuli-responsive.
Flowerlike submicrometer gold particles were synthesized through a simple one-step method using p-diaminobenzene as a reductant in the presence of poly(sodium 4-styrenesulfonate) in aqueous solution. The particle size with diameters ranging from 267 to 725 nm could be tuned by varying the molar ratio of poly(sodium 4-styrenesulfonate) to HAuCl4, which also resulted in tunable roughness. The gold particles were confirmed by scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, and x-ray photoelectron spectroscopy. Cyclic voltammetry showed that the specific surface area of the flowerlike particles was larger than that of sphere particles. The obtained flowerlike particles with higher surface area also exhibited higher electrocatalytic activity toward H2O2 and O2. The increase of electrocatalytic activity could be attributed to the increase of the active surface area.
Ni0.8Zn0.2Fe2O4/Ba0.6Sr0.4TiO3 (NZO/BST) composites with high permittivity and low loss were synthesized via the hybrid processing route. The composites possess very dense and homogenous microstructure. The NZO/BST composites show good dielectric properties and magnetic properties with low loss in high frequency range. This indicates that this kind of magnetodielectric composites can be used in high-frequency communications for the capacitor-inductor integrating devices such as electromagnetic interference filters and antennas. The permittivities of the composites were also fitted using the combination of Maxwell–Wagner polarization and modified Curie–Weiss law.
When MRS Bulletin published its expanded special issue in April 2008, “Harnessing Materials for Energy,” it was not a project done lightly. The impetus for this effort was the desire to describe the veritable options that materials provide in energy technologies. These options can then be evaluated in the context of other imperatives such as economic viability and environmental concerns, which all interact to determine societal choices for energy.
The dependence of the dielectric properties on the uniaxial compressive stress and the stress-strain properties was investigated for the case of (1-x)Na0.5Bi0.5TiO3–xNaTaO3 ceramics. Special attention was focused on the time component and the reversibility of the permittivity–stress dependence. The results were interpreted according to the samples' polar and symmetry states and the ferroelasticity. The time dependence and irreversible changes of the dielectric properties were connected with the domain structure of the materials, which is modified under the applied stress. The irreversible changes observed in the macroscopically nonferroelectric compositions were related to the ferroelastic properties. The stress sensitivity increased with the addition of NaTaO3 from 3% in pure Na0.5Bi0.5TiO3 to 14% in the sample with 15 mol% of NaTaO3 (at 200 MPa and 1 MHz). The reversibility was improved by mechanical modification of the samples' domain state, while the dielectric response remained time dependent.
Tight networks of interwoven carbon nanotube bundles are formed in our highly conductive composite. The composite possesses properties suggesting a two-dimensional percolative network rather than other reported dispersions displaying three-dimensional networks. Binding nanotubes into large but tight bundles dramatically alters the morphology and electronic transport dynamics of the composite. This enables it to carry higher levels of charge in the macroscale leading to conductivities as high as 1600 S/cm. We now discuss in further detail, the electronic and physical properties of the nanotube composites through Raman spectroscopy and transmission electron microscopy analysis. When controlled and used appropriately, the interesting properties of these composites reveal their potential for practical device applications. For instance, we used this composite to fabricate coatings, which improve the properties of an electromagnetic antenna/amplifier transducer. The resulting transducer possesses a broadband range up to GHz frequencies. A strain gauge transducer was also fabricated using changes in conductivity to monitor structural deformations in the composite coatings.
A number of congruent LiNbO3 crystals homogeneously doped with 5 mol% Mg in growth melt were subjected to Li-rich vapor transport equilibration (VTE) treatments at 1100 °C for different durations. Secondary ion mass spectrometry study shows that the VTE induces the Mg diffusion within the crystal and an inhomogeneous Mg depth profile. The surface Mg concentration, determined from measured ordinary refractive index, shows a strong VTE duration dependence. Neutron activation analysis shows that the amount of MgO diffusing out of the crystal is ignorable, allowing to conclude that the Mg ions counter diffuse to the crystal surface at the early stage of VTE and then come back toward equilibrium as the Li concentration comes to equilibrium. The VTE-induced Li2O content increase in crystal was determined by the gravimetric method. The crystalline phase, crystal composition, and site occupation of Mg and Li are discussed.
A new method to accurately and reliably extract the actual Young's modulus of a thin film on a substrate by indentation was developed. The method involved modifying the discontinuous elastic interface transfer model to account for substrate effects that were found to influence behavior a few nanometers into a film several hundred nanometers thick. The method was shown to work exceptionally well for all 25 different combinations of five films on five substrates that encompassed a wide range of compliant films on stiff substrates to stiff films on compliant substrates. A predictive formula was determined that enables the film modulus to be calculated as long as one knows the film thickness, substrate modulus, and bulk Poisson's ratio of the film and the substrate. The calculated values of the film modulus were verified with prior results that used the membrane deflection experiment and resonance-based methods. The greatest advantages of the method are that the standard Oliver and Pharr analysis can be used, and that it does not require the continuous stiffness method, enabling any indenter to be used. The film modulus then can be accurately determined by simply averaging a handful of indents on a film/substrate composite.
Two laser processes, flat plate ablation (FPA) and laser ablation of microparticle aerosols (LAMA), capable of producing nanoparticles and nanoparticulate thick films of Terfenol-D (Fe1.92Tb0.3Dy0.7) were investigated. The influence of processing parameters on the sizes, compositions, and morphologies of the nanoparticles produced using these processes were studied by transmission electron microscopy. The nanoparticles were used to deposit nanoparticulate films by supersonic impaction with thicknesses ranging from 4 to 50 μm, depending on processing conditions. The microstructures and properties of the films were studied using scanning electron microscopy and magnetometry. The LAMA process produced nanoparticles with a mean size and standard deviation (SD) of 8 to 10 nm ± 5 nm, depending on the type of gas used during synthesis. In contrast, nanoparticles produced using the FPA process exhibited a much broader size distribution varying from 5 to 150 nm and a much greater variation in compositions compared to the LAMA process. Films produced using LAMA also had lower levels of porosity compared to those produced using FPA as a result of the smaller, more uniform nanoparticles from which they were produced and the resulting higher impaction velocities. Compared to the FPA-produced films, the LAMA-produced films exhibited greater resistance to oxidation, higher magnetizations (13–15 emu/g versus 9–11 emu/g, depending on processing conditions) and lower coercivities (versus 41–59 Oe versus 80–110 Oe).
Individual nanotubes made of carbon, boron nitride, iron, silicon, or other materials have properties such as high strength, toughness, electrical and thermal conductivity, and light weight that cannot be matched by conventional materials. Nanotubes also change their properties in response to external fields and change one type of energy into another, which are useful for design. This article explores three main steps in exploiting responsive materials based on nanotubes: nanotube synthesis, macroscale material fabrication, and incorporation into device structures for novel applications. Nanotubes are always synthesized as individual particles in the form of powders, smoke particles, or aligned forests. To be industrially important, nanotubes generally must be processed to form derivative materials such as functionalized/coated powders and forests and macroscale intermediate materials such as sheets, ribbon, and yarn. The processed nanotubes are then used to develop responsive materials and devices that are able to resist, react to, or generate energy from their environment. This article provides background information and ideas on how to develop nanotube responsive materials for everyday use.
AlxIn1–xN films were grown on (0001) sapphire substrates by reactive radiofrequency (RF) magnetron sputtering in an ambient of Ar and N2. The XRD patterns are shown from AlxIn1–xN films grown on AlN/sapphire substrates using a wide range of magnetron power ratio settings. The wurtzite structure films have high crystal quality with full-width at half-maximum (FWHM) in the range of 0.22°–0.52°. The surface morphologies were observed by scanning electron microscopy (SEM). Raman spectra were measured on the AlxIn1–xN surfaces in a backscattering configuration at room temperature with 532 nm laser excitation and show A1(LO) bimodal behavior. Electrical resistivity and electron mobility were measured by the Hall effect method in the conventional Van der Pauw geometry at room temperature. The lowest electrical resistivity is 1 × 10−3 Ω·cm. This work suggests that reactive magnetron sputtering is a promising method for growing AlxIn1–xN films in over a large composition range.
Trace additions of boron to cast zirconium result in significant microstructural changes similar to those observed with additions of boron to titanium alloys. These changes include the promotion of dendritic growth and a refinement in both the prior β and α grain size. The refinement of the prior β grain size is explained using a model of grain refinement in association with values calculated from the binary Zr–B phase diagram. It is proposed that the refinement of the α phase occurs through a combination of increased nucleation and altered diffusion mechanisms during cooling through the β transus.
Structural origin of the high glass-forming ability (GFA) in multicomponent bulk metallic glasses (BMGs) caused by minor alloying was investigated using state-of-the-art synchrotron radiation techniques. It is found that a two-shell icosahedral cluster with one Y center is the basic structural unit in the representative Cu46Zr42Al7Y5 BMG, which may be densely packed with the help of shared and glue atoms, leading to enhanced ordering at short and medium range. This cluster dense packing may play a key role in achieving the high GFA in CuZrAlY alloy, which also explains the strong dependence of GFA on Y content observed in many experiments. The present work may be extended to a series of multicomponent amorphous alloys, the formation of which is strongly dependent on minor alloying.
The asymmetrical hysteresis loops were observed for the annealed Fe65Co15Si5B15 amorphous ribbons. The curves, which shift from the zero point of H axis with a unilateral step magnetization, exhibit the special magnetic features of the ribbons. A few magnetic crystalline phases were identified in the amorphous matrix of annealed ribbons by microstructure measurement. It was also found that the Z-oriented local magnetic domains emerge in the surface of ribbons with the loops shift behavior. Subsequent magnetic torque measurement indicated that the unidirectional magnetic anisotropy was induced in the amorphous ribbons with proper thermomagnetic annealing. These obtained evidences support our understanding that the magnetic history caused by thermomagnetic treatment plays a main role in promoting the formation of the asymmetrical loops.
A dye-sensitized photoelectrochemical (DS-PEC) cell consisting of SnO2 and ZnO nanoparticles was found to yield higher solar energy conversion efficiency than similar cells made of the individual oxide semiconductors when they were sensitized with an indoline dye. The SnO2/ZnO composite solar cell gave an overall energy conversion efficiency of 3.8% while the SnO2 and ZnO individual cells yielded efficiencies of 2.8% and 1.2%, respectively, under standard AM 1.5 irradiation (100 mW cm−2). The broadening of the absorption spectra and a large red shift of the absorption peak were observed by the adsorbing dyes on the composite film suggesting the formation of various kinds of J-aggregates. It is suggested that the formation of the J-aggregates and the presence of the ZnO barrier were responsible for the higher efficiency of the composite cell.
Soft matter—also known as complex fluids—is a field of growing interest and importance, spanning many classes of materials, including polymers, biopolymers, colloids, and liquid crystals. Different approaches for microstructural characterization are more appropriate than those used for hard (and usually fully crystallized) materials such as metals and inorganic materials because of the time and length scales involved. This article discusses a range of techniques applicable to the characterization of soft matter, including environmental scanning electron microscopy (SEM) and microrheology. The former offers two key advantages for this class of material over conventional SEM because it requires neither a high vacuum—which is a problem for hydrated samples—nor that an insulator be coated with a conductive material. Microrheology is well suited to small volumes of fluid with low moduli that may be heterogeneous; it is capable of measuring gelation in real time.