Ashok Kumar Mandal

Direct somatic embryogenesis and plantlet regeneration from cotyledonary leaves of safflower

Somatic embryos were induced directly on adaxial surface of cotyledonary leaves within 8–10 days of culture on Murashige and Skoog medium containing 5.37 to 10.74 μM 1 — napthaleneacetic acid and 2.22 μM benzyl adenine. Germinated embryos with shoot axes developed into complete plants after transfer onto half stength Murashige and Skoog medium containing 1.07 μM 1 — napthaleneacetic acid. Histological studies suggested direct origin of somatic embryos with broad-base attachment.

Synthesis of Mg(OH)2 micro/nano flowers at room temperature

The inexpensive and green method of synthesis for self-assembled micro/nano structures is an important area of emerging research. Such structures can be chemically tuned with predesigned functional properties. Therefore, they hold very good promise for future applications, e.g., biomedicine, electronic device, solar energy, gas sensing. Here we report for the first time an inexpensive and green method for chemical deposition of magnesium hydroxide (Mg(OH)2) micro/nano flowers in thin films on commercial soda lime silica glass substrates at room temperature. Under identical conditions, chemically synthesized Mg(OH)2 powders are also prepared in absence of the soda lime silica glass substrates. The condition that favors the growth of micro/nano flowers in thin films is identified from X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX) data. Finally, the possible growth mechanism of micro/nano flowers in thin films is discussed.

Chemically deposited magnesium hydroxide thin film

Abstract Here we report for the first time to the best of our knowledge the processing techniques, nucleation kinetics and the nanoindentation behaviour of a 1·5 μm magnesium hydroxide thin film chemically deposited on a commercially available soda lime silica glass substrate at room temperature. The phase and microstructure of the films were analysed by X-ray diffraction, scanning electron microscopy, field emission scanning electron microscopy as well as transmission electron microscopy. An exponential nucleation kinetics was identified for the growth of the thin films. The nanomechanical properties, e.g. nanohardness and Young’s modulus of the films were measured by the nanoindentation technique at ultralow loads of 50, 70 and 100 μN. Finally, the nature of deformation of the thin film was analysed in terms of the energetics of the nanoindentation process and the microstructure.

Iron ore tailing: a waste material used in ceramic tile compositions as alternative source of raw materials

In the present study, three batch compositions were prepared utilizing iron ore tailing in the range of 45-60 wt%, clay 25-35 wt% and feldspar 15-20 wt%. The compacts were heated in the temperature range of 1100o-1150oC. All the samples heated at 1150oC possess very high cold crushing strength (>150 MPa) and high flexural strength (>60 MPa) with less than 0.1% water absorption. Such high mechanical strength is beneficial for floor tiles to prevent impact damage. The phase evolution during heating of the mixture of iron ore tailing, clay and feldspar have been characterized by X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) studies with energy dispersive X-ray analysis (EDX) of selected samples.

Growth of dip coated magnesium oxide nanoflower thin films

The present work reports the synthesis of dip coated MgO nanoflower thin films. The films are developed without employing any capping agent and catalyst. A simple chemical deposition technique is adopted for this purpose. The MgO nanoflower thin films are characterised by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy and the related energy dispersive X-ray spectroscopy techniques. The results establish the phase purity and microstructural details of the MgO nanoflower thin films. These results are explained in terms of a proposed mechanism that suggests the growth process for the MgO nanoflower structures.

Nanomechanical responses of human hair

Here we report the first ever studies on nanomechanical properties e.g., nanohardness and Young׳s modulus for human hair of Indian origin. Three types of hair samples e.g., virgin hair samples (VH), bleached hair samples (BH) and Fe-tannin complex colour treated hair samples (FT) with the treatment by a proprietary hair care product are used in the present work. The proprietary hair care product involves a Fe-salt based formulation. The hair samples are characterized by optical microscopy, atomic force microscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy (EDAX) genesis line map, EDAX spot mapping, nanoindentation, tensile fracture, and X-ray diffraction techniques. The nanoindentation studies are conducted on the cross-sections of the VH, BH and FT hair samples. The results prove that the nanomechanical properties e.g., nanohardness and Young׳s modulus are sensitive to measurement location e.g., cortex or medulla and presence or absence of the chemical treatment. Additional results obtained from the tensile fracture experiments establish that the trends reflected from the evaluations of the nanomechanical properties are general enough to hold good. Based on these observations a schematic model is developed. The model explains the present results in a qualitative yet satisfactory manner.

Comparative Study of Indentation Size Effects in As-Sintered Alumina and Alumina Shock Deformed at 6.5 and 12 GPa

Nanohardness of alumina ceramics determines its performance in all contact-related applications because the issue of structural integrity gets determined at the nanoscale of contact. In spite of the wealth of the literature, however, it is not yet known in significant details how the high-strain rate flyer-plate impact at different pressure affects the nanohardness of dense, coarse grain alumina ceramics. Thus, the load controlled nanoindentation experiments were performed with a Berkovich indenter on an as-received coarse grain (~10 μm), high density (~3.98 gm·cc−1) alumina, and shock recovered tiny fragments of the same alumina obtained from gas gun experiments conducted at 6.5 GPa and 12 GPa shock pressures with stainless steel flyer plates. The nanohardness of the as-received alumina was much higher than that of the 6.5 GPa and 12 GPa shock-recovered alumina. The indentation size effect (ISE) was the strongest in alumina shocked at 12 GPa and strong in alumina shocked at 6.5 GPa, but it was mild in the as-received alumina sample. These results were rationalized by analysis of the experimental load depth data and evidences obtained from field emission scanning electron microscopy. In addition, a rational picture of the nanoindentation responses of the as-received and shocked alumina ceramics was provided by a qualitative model.

A New Mechanism for ISE in Alumina Shock Deformed at 6.5 GPa

With a view to understand how high strain rate flyer plate impact affects the nanohardness of a coarse (10 μm) grain high density (3.978 gm.cc−1) alumina, load controlled nanoindentation experiments were conducted with a Berkovich indenter on as received alumina (ARA) and shocked alumina fragments (SA) of obtained from a flyer plate shock impact study at 6.5 GPa. The results showed that the nanohardness of the shocked alumina (SA) samples was much lower than that of the as received alumina (ARA) samples and that the indentation size effect (ISE) was mild in the ARA but quite severe in the SA samples. Extensive additional characterization by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and a physical model based analysis of the experimental load depth data were utilized to provide a new explanation for the presence of strong indentation size effect in the shock recovered alumina.