Diffusional reactions between Mo and Si in the synthesis and densification of MoSi2

In combustion synthesis, and in simultaneous reaction synthesis and hot pressing of Mo + 2Si powders, a heterogeneous reaction occurs between liquid Si and Mo powder. When the reactant mixture is heated at low heating rates, Mo₅Si₃ is observed as a secondary phase along with MoSi₂. Application of pressure during the reaction synthesis of MoSi₂ eliminates the need to hot press a pre-alloyed powder. The technique can be applied to obtain composites and alloys of MoSi₂ and various other transition metal silicides.     

Miscibility,water uptake,ion exchange capacity,conductivity and dielectric studies of poly(methyl methacrylate) and cellulose acetate blends

In the last few decades, polymer blends with good miscibility and conductivity have been the focus of study for material scientists. Here, polymer blends of Poly(methyl methacrylate) (PMMA) and Cellulose acetate (CA) of varying blend compositions have been prepared by solution casting method and their miscibility, water uptake, ion exchange capacity (IEC) proton conductivity, and dielectric properties have been studied. Dimethyl formamide (DMF) was used as solvent. Fourier transform infrared spectra (FTIR) and Differential scanning calorimetry (DSC) measurements have been used to analyze the miscibility of the blends. Up to 50/50 PMMA/CA, water uptake showed an increasing trend and for other compositions the value decreased. Ion exchange capacity and conductivity of the blends decreased with increase in PMMA content of the blends. The variations in the blend properties have been attributed to the presence of specific interactions and exchangeable groups in the blend system. The proton conductivity of the blends is in the order of 10^?3 S cm^?1. Impedance analysis of the blends indicated the absence of any relaxation phenomenon in the blend system. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3074–3081, 2013     

Inheritance of sugar concentration in stalk (brix), sucrose content,stalk and juice yield in sorghum

Sweet sorghum is gaining importance as a raw material for ethanol production. Information on genetics of sugar content in stalk is required to facilitate the breeding of cultivars with high ethanol yield. Generation mean analysis and frequency distribution studies were carried out in crosses 27 B × kellar, and 27 B × BJ 204 for sweet stalk during 2006 and 2007. Kellar (a US sweet sorghum line) and BJ 204 (a Chinese line) are high brix (sweet stalk) lines. The traits studied were: brix, sucrose, stalk, and juice yield and plant height. The mean performance of families showed that the F₁ in crosses for high brix and sucrose percentage were tending towards P₂ (higher sugar percentage parent) implying these traits to be dominant for higher brix and sucrose content. However, the mean values of F₁ for stalk and juice yields and plant height showed over-dominance for the traits. Frequency distribution of F₂ showed that brix and sucrose percentage are polygenic traits, and stalk and juice yields are oligogenic traits. Generation mean analysis showed that both additive and dominant gene actions for traits, sucrose and brix in stalk juice were significant. Since the plant traits important for high stalk sugar percentage show dominance and over-dominance inheritance, hybrid breeding will be useful. Selection for pure lines with high brix is to be practised in later generations.     

A feasibility study of a post-buckled beam for actuating helicopter trailing edge flap

Active trailing edge flaps (TEFs) are one of the most promising devices for helicopter vibration reduction. Smart actuators such as the piezoelectric stack actuators (PEAs) are used for TEF actuation. PEAs possess high energy density and have large force in dynamic condition but are limited to small displacements. In this investigation, we study a linear to rotary motion amplification mechanism (AM-2) based on a pinned–pinned post-buckled beam to actuate trailing edge flaps. A linear motion amplification mechanism is developed and coupled with AM-2 to amplify angular flap deflections. Experiments are conducted on bench top-test setup, and maximum flap angle deflections of the order of 12° are achieved in the static case. An aeroelastic analysis is performed and 91 % reduction in helicopter vibration is obtained with multiharmonic control inputs.     

Temperature variation of thermoelectric power of vacuum deposited PbSe thin films and its thickness dependence

PbSe thin films of thicknesses in the range 20 to about 170 nm have been prepared on glass substrates held at room temperature by thermal evaporation of the bulk alloy at a pressure of 5×10^–5 torr. The thermoelectric power of these films has been evaluated as a function of temperature in the range 300 to 500 K from the thermal e.m.f. data. It was found that the thermoelectric power of all the films initially increases with increasing temperature, then reaches a maximum, and, with a further increase in temperature, decreases rapidly and also changes sign. The possible reasons for this peculiar behaviour have been given. It is also found that there is no systematic variation of thermoelectric power with thickness of the films. This is probably due to completely specular scattering at the external and internal surfaces of PbSe thin films or to changes in stoichiometry of different films.     

Direct Magnetic Patterning due to the Generation of Ferromagnetism by Selective Ion Irradiation of Paramagnetic FeAl Alloys

Sub‐100‐nm magnetic dots embedded in a non‐magnetic matrix are controllably generated by selective ion irradiation of paramagnetic Fe₆₀Al₄₀ (atomic %) alloys, taking advantage of the disorder‐induced magnetism in this material. The process is demonstrated by sequential focused ion beam irradiation and by in‐parallel broad‐beam ion irradiation through lithographed masks. Due to the low fluences used, this method results in practically no alteration of the surface roughness. The dots exhibit a range of magnetic properties depending on the size and shape of the structures, with the smallest dots (<100 nm) having square hysteresis loops with coercivities in excess of µ₀H_C = 50 mT. Importantly, the patterning can be fully removed by annealing. The combination of properties induced by the direct magnetic patterning is appealing for a wide range of applications, such as patterned media, magnetic separators, or sensors.