Room temperature synthesis of highly hemocompatible hydroxyapatite, study of their physical properties and spectroscopic correlation of particle size

Needle shaped nanoparticles of hydroxyapatite (HA) have been synthesized at room temperature using orthophosphoric acid as the source of (PO4)3- ions, while calcium chloride, the calcium source, is suitably complexed with citric acid/tartaric acid/acetic acid. The presence of ligands inhibits the growth along [001] and [100] directions of the crystal and thus, helps in formation of needle shaped nanoparticles. The chemical compositions of the samples have been established through AAS and FTIR spectroscopy, while the crystallinity has been assessed through XRD and by the spectral changes in the υ1 and υ3 frequencies of the phosphate group in the respective FTIR spectra. The particle sizes of the samples have been determined from line broadening studies and correlations have been established between the curve fitted percentage area of FTIR and full width half height (FWHH) of the XRD peaks. TEM studies revealed the particle to be needle-shaped with a length and diameter in the range of 20-65 nm and 4-11 nm respectively. Changes in the surface charge of the water dispersed HA samples have been determined at different pH and the isoelectric point for the samples have been found in the range of 3.1-3.4. Finally, the morphology, surface area and hemocompatibility characteristics of the HA samples, prepared by using different complexing agents, have been compared.     

Nanomechanical Characterization of Indium Nano/Microwires

Nanomechanical properties of indium nanowires like structures fabricated on quartz substrate by trench template technique, measured using nanoindentation. The hardness and elastic modulus of wires were measured and compared with the values of indium thin film. Displacement burst observed while indenting the nanowire. ‘Wire-only hardness’ obtained using Korsunsky model from composite hardness. Nanowires have exhibited almost same modulus as indium thin film but considerable changes were observed in hardness value.     

Influence of Cobalt Doping on the Physical Properties of Zn<Subscript>0.9</Subscript>Cd<Subscript>0.1</Subscript>S Nanoparticles

Zn_0.9Cd_0.1S nanoparticles doped with 0.005–0.24 M cobalt have been prepared by co-precipitation technique in ice bath at 280 K. For the cobalt concentration >0.18 M, XRD pattern shows unidentified phases along with Zn_0.9Cd_0.1S sphalerite phase. For low cobalt concentration (≤0.05 M) particle size, d _XRD is ~3.5 nm, while for high cobalt concentration (>0.05 M) particle size decreases abruptly (~2 nm) as detected by XRD. However, TEM analysis shows the similar particle size (~3.5 nm) irrespective of the cobalt concentration. Local strain in the alloyed nanoparticles with cobalt concentration of 0.18 M increases ~46% in comparison to that of 0.05 M. Direct to indirect energy band-gap transition is obtained when cobalt concentration goes beyond 0.05 M. A red shift in energy band gap is also observed for both the cases. Nanoparticles with low cobalt concentrations were found to have paramagnetic nature with no antiferromagnetic coupling. A negative Curie–Weiss temperature of −75 K with antiferromagnetic coupling was obtained for the high cobalt concentration.     

Effect of A2O3 (A = La,Y, Cr,Al) on thermal and crystallization kinetics of borosilicate glass sealants for solid oxide fuel cells

Influence of various intermediate oxides on thermal, structural and crystallization kinetics of 30BaO–40SiO₂–20B₂O₃–10A₂O₃ (A = Y, La, Al, Cr) glasses has been studied. The highest glass transition temperature (T_g) with high thermal stability is observed in Y₂O₃ containing glasses as compared to other glasses. The thermal expansion coefficient (TEC) increases with increasing heat treatment duration in all the glasses. The maximum increase in TEC is observed in Cr₂O₃ containing glass ceramics. FTIR study showed that transmission bands due to silicate and borate chains become sharper with splitting after heat treatment. A selected glass sample (BaCr) has been tested for interaction and adhesion with Crofer 22 APU interconnect material for its application as a sealant in solid oxide fuel cell.     

A mass transport and hydrodynamic evaluation of membrane separation cell

This study reports an analysis of membrane permeance and mass transfer coefficient in laboratory test cells for gas separation using computational fluid dynamics. Mass transfer coefficients and species concentration were computed across the membrane surface for gas mixture. The same test cells were examined for the fluid hydrodynamics in liquid separation. It was observed that the uniform flow distribution in the case of gas separation was responsible for improved permeance; whereas, a uniform flow had no significant effect on permeation rate for liquid separation. Also, the potential reasons for the difference in gas and liquid separation are discussed.     

Fe-Zn Alloy Coating on Galvannealed (GA) Steel Sheet to Improve Product Qualities

Galvannealed steel sheets (GA) have become the mainstream steel sheet for automobile applications because of their superior corrosion resistance, paintability, and weldability. To impart specific properties, different coatings on GA steel sheet were reported to improve properties further. In this context, we have developed an electroplating process (flash coating) for bright and adherent Fe-Zn alloy coating on GA steel sheet to enhance performances such as weldability, frictional behavior, phosphatability, and defect coverage. A comparative study with bare GA steel sheet was carried out for better elastration. The electroplating time was reduced below 10 s for practical applicability in an industrial coating line by modulating the bath composition. Electroplating was performed at current density of 200-500 A/m² which yielded with higher cathode current efficiency of 85-95%. The performance results show that Fe-10 wt.% Zn-coated GA steel sheet (coating time 7 s) has better spot weldability, lower dynamic coefficient of friction (0.06-0.07 in lubrication), and better corrosion resistance compared to bare GA steel sheet. Uniform phosphate coating with globular crystal size of 2-5 µm was obtained on Fe-Zn flash-coated GA steel sheet. Hopeite was the main phosphate compound (77.9 wt.%) identified along with spencerite (13.6 wt.%) and phosphophyllite (8.5 wt.%).     

A Multiaxial Low Cycle Fatigue Life Prediction Model for Both Proportional and Non-proportional Loading Conditions

This paper has presented a life prediction model in the field of multiaxial low-cycle fatigue. The proposed model is generally applied for constant amplitude multiaxial proportional and non-proportional loading. Depending upon applied strain path the equivalent strain varies within a cycle. Equivalent average strain amplitude is considered as fatigue damage parameter in the proposed model. The model has requirement of only two material constants and no other tuning parameters. The model is examined by the proportional and non-proportional low-cycle fatigue life experimental data for eight different types of materials. The model is successfully correlated with multiaxial fatigue lives of eight different materials.     

Enhancement of Corrosion Resistance of Zinc Coatings Using Green Additives

In the present work, morphology, microstructure, and electrochemical behavior of Zn coatings containing non-toxic additives have been investigated. Zn coatings were electrodeposited over mild steel substrates using Zn sulphate baths containing four different organic additives: sodium gluconate, dextrose, dextrin, and saccharin. All these additives are “green” and can be derived from food contents. Morphological and structural characterization using electron microscopy, x-ray diffraction, and texture co-efficient analysis revealed an appreciable alteration in the morphology and texture of the deposit depending on the type of additive used in the Zn plating bath. All the Zn coatings, however, were nano-crystalline irrespective of the type of additive used. Polarization and electrochemical impedance spectroscopic analysis, used to investigate the effect of the change in microstructure and morphology on corrosion resistance behavior, illustrated an improved corrosion resistance for Zn deposits obtained from plating bath containing additives as compared to the pure Zn coatings.     

Optical and structural properties of highly porous shell structured Fe doped TiO2 thin films

TiO2thin films with 0.2 wt%, 0.4 wt%, 0.6wt%, and 0.8 wt% Fe were prepared on glass and silicon substrates using sol–gel spin coating technique. The optical cut-off points are increasingly red-shifted and the absorption edge is shifted over the higher wavelength region with Fe content increasing. As Fe content increases, the optical band gap decreases from 3.03 to 2.48 eV whereas the tail width increases from 0.26 to 1.43 eV. The X-ray diffraction（XRD） patterns for doped films at 0.2 wt% and0.8 wt% Fe reveal no characteristic peaks, indicating that the film is amorphous whereas undoped TiO2exhibits（101） orientation with anatase phase. Thin films of higher Fe content exhibit a homogeneous, uniform, and nanostructured highly porous shell morphology.