Non Ferrous Materials Technology Development Center

Hyderabad, India

Non Ferrous Materials Technology Development Center

Hyderabad, India
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Kumar G.S.V.,Non Ferrous Materials Technology Development Center | Kumar G.S.V.,Helmholtz Center Berlin | Sundarraj S.,India Science Laboratory
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science | Year: 2010

An investigation into the effect of ternary alloying element additions such as copper, magnesium, manganese, zinc, and nickel on pore formation in cast Al-12.6-wt pct Si eutectic alloy by employing a novel pore characterization technique is reported here. In this approach, the low-pressure testing method was combined with the metal foam manufacturing technique of intentionally adding TiH 2, which enhances hydrogen pore formation and offers a method to distinguish the effect of individual alloying elements on hydrogen porosity formation. © The Minerals, Metals & Materials Society and ASM International 2010.


Rajyalakshmi A.,Non Ferrous Materials Technology Development Center
International journal of nanomedicine | Year: 2011

One of the important prerequisites for a successful orthopedic implant apart from being osteoconductive is the elicitation of a favorable immune response that does not lead to the rejection of the implant by the host tissue. Anodization is one of the simplest surface modification processes used to create nanotextured and nanotubular features on metal oxides which has been shown to improve bone formation. Anodization of titanium (Ti) leads to the formation of TiO(2) nanotubes on the surface, and the presence of these nanotubes mimics the natural nanoscale features of bone, which in turn contributes to improved bone cell attachment, migration, and proliferation. However, inflammatory cell responses on anodized Ti remains to be tested. It is hypothesized that surface roughness and surface feature size on anodized Ti can be carefully manipulated to control immune cell (specifically, macrophages) responses. Here, when Ti samples were anodized at 10 V in the presence of 1% hydrofluoric acid (HF) for 1 minute, nanotextured (nonnanotube) surfaces were created. When anodization of Ti samples was carried out with 1% HF for 10 minutes at 15 V, nanotubes with 40-50 nm diameters were formed, whereas at 20 V with 1% HF for 10 minutes, nanotubes with 60-70 nm diameters were formed. In this study, a reduced density of macrophages was observed after 24 hours of culture on nanotextured and nanotubular Ti samples which were anodized at 10, 15, and 20 V, compared with conventional unmodified Ti samples. This in vitro study thus demonstrated a reduced density of macrophages on anodized Ti, thereby providing further evidence of the greater efficacy of anodized Ti for orthopedic applications.


Rahul S.H.,Non Ferrous Materials Technology Development Center | Balasubramanian K.,Osmania University | Venkatesh S.,Osmania University
Materials Today: Proceedings | Year: 2015

Dense 5 mol% Y2O3 doped ZrO2(5YSZ) thin film is grown on α-Al2O3 porous substrates through drop on demand inkjet printing process (DOD-IJP). 5YSZ inks are prepared throughhigh energy milling(HEM) process in non aqueous media withbinder which contributes to stability caused by ionic and electrostatic repulsion of particles in suspended state. Inkjet print architecture over sintered α-Al2O3 porous substrates aided in the development of dense microstructure with stabilization of c-ZrO2 phase in the presence of toughened m-ZrO2 phase at room temperature. After high temperature sintering process, thin film surface coarsens due to formation of c-ZrO2 /m-ZrO2 phases with visible signs of grain pullout. Multiple depositions of variable particle size 5YSZ suspensions by inkjet printing process yielded epitaxial growth, improved adhesion, fine grains, decreased porosity, higher shrinkage and dense non columnar grain structure on porous substrates. © 2015 Elsevier Ltd.


Rahul S.H.,Non Ferrous Materials Technology Development Center | Balasubramanian K.,Non Ferrous Materials Technology Development Center | Venkatesh S.,Osmania University
International Journal of Precision Engineering and Manufacturing | Year: 2015

This paper describes a novel methodology of coating Yttria stabilized Zirconia (YSZ) suspensions on AISI316L steel substrates and involves a micro structural investigation to understand the sintering behavior. Nano sized particles are used at lowering of sintering temperature. Nano particle suspension inks prepared through high energy milling process is visibly stable due to ionic charge carriers in binder and solvent. Deposition of suspended material was done through inkjet printing (IJP) and spin coating (SC) processes. Print head offset in X and Y directions lead to fabrication of homogeneous layers. Inkjet printing at elevated temperatures is useful especially in controlling nano particle seepage through porous substrates. Low temperature sintering of suspended particles in the ink leads to development of porous YSZ films due to the presence of carrier solvent and binder/dispersants in the ink. Sintered films exhibit completely stable tetragonal zirconia with uniformly porous microstructure. Pore sizes of 50 nm and 100 nm have been reported at least for inkjet printed and spin coated films respectively. The homogeneity observed in pores of YSZ film is a typical characteristic of inkjet printing process which is attributed to the layer by layer stacking of nano particles during the deposition process. © 2015, Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg.


Mishra S.,Non Ferrous Materials Technology Development Center | Ranjana R.,Non Ferrous Materials Technology Development Center | Balasubramanian K.,Non Ferrous Materials Technology Development Center
Journal of Alloys and Compounds | Year: 2012

Attempts have been made towards the synthesis of nano-alumina powder through conventional combustion synthesis (CCS) method. Detailed evaluation of the process parameters has been done through XRD and SEM, on the as-synthesized nano-alumina powders. The as-synthesized nano-alumina (-γ phase) were used for developing ceramic spacers for thermal insulation application under load. The densification and mechanical strength of ceramic components consolidated from the alumina powders has been measured. The results have shown that the as-fabricated nano-alumina based components have high structural integrity at green stage (∼65%) with 2 wt.% nano γ-alumina, significant mechanical strength (∼230 MPa) and excellent thermal shock resistance (functional testing at ∼1400 °C temperature and under 50 T dynamic load). The comprehensive study for the fabrication of nano-alumina based ceramic spacers has been illustrated. © 2012 Elsevier B.V.


Mishra S.,Non Ferrous Materials Technology Development Center | Rajyalakshmi A.,Non Ferrous Materials Technology Development Center | Balasubramanian K.,Non Ferrous Materials Technology Development Center
Journal of Biomedical Materials Research - Part A | Year: 2012

Bioceramics are although well known for their osteoinductive and osseointegrative properties in bone tissue regeneration, yet, they are inappropriate for load bearing applications due to inadequate mechanical strength. In this article, the authors report the expansion of hematopoietic stem cells (HSCs) on as-synthesized composite scaffolds from hydroxyapatite and β-tricalcium phosphate for bone tissue engineering, in an adequate load-bearing application. The physical, structural, and mechanical properties of the composite scaffolds have been examined and correlated with the in vitro adhesion pattern of HSCs. The results indicated that the response of HSCs varies with change in the stoichiometry of composite scaffolds. The H2T2 scaffolds have exhibited the highest expansion of CD34+ cells and long-term culture initiating cells when compared with other stoichiometries. The results suggest that H2T2 composite can be a potential strategic bone-graft substitute in contrast with monolithic bioceramics, serving a dual role of bioresorbability and enhanced load-bearing capacity. Copyright © 2012 Wiley Periodicals, Inc.


Mishra S.,Non Ferrous Materials Technology Development Center | Mitra R.,Indian Institute of Technology Kharagpur
Journal of Alloys and Compounds | Year: 2010

A novel method for the preparation of ceramic foams with uniform pore and pore size distribution through the addition of isopropanol (iPr-OH) has been discussed. Small amounts of isopropanol were added to silica based aqueous suspensions and the foams were prepared by foam casting method. The rheology of silica based suspensions and properties of the resulting foam are examined and compared with that of samples prepared without iPr-OH addition within similar experimental conditions. Silica foams produced using this novel method displays comparatively higher density, smaller and uniform pores with narrow pore size distribution and significantly improved mechanical strength. The porosity of 79 vol.% and the pore size distribution of 4-25 μm were obtained. The compressive strength of 1.4 MPa with a Young's modulus of 143 MPa was achieved as compared to the low values of compressive strength and elastic modulus of 0.332 and 60 MPa, respectively for the samples without iPr-OH addition. © 2010 Elsevier B.V. All rights reserved.


Mishra S.,Non Ferrous Materials Technology Development Center | Ranjana R.,Non Ferrous Materials Technology Development Center
Materials and Manufacturing Processes | Year: 2010

Dewaxing of investment shells is the most critical step in the investment casting process. It defines the fate of casting because the surface and dimensional characteristics of the wax are transferred to the ceramic shell and so to the final casting. A novel route of dewaxing of investment shells through a modified thermal heating method and the effect of such thermal heating on investment shells has been investigated. The experiments have shown firstly the formation of a "dilatation gap" followed by the reversal of the solidification path, and both facilitate the management of thermal expansion-related problems, resulting in smooth discharge of molten wax. The shells made by this methodology of Reversed Solidification Path Dewaxing (RSPD) enable production with low rejection rates. The investment has been shown to be of high strength, sustaining thermal shock of more than one casting trial. The process can therefore be of great industrial importance pertaining to cost and energy efficiency, reduced defects, and high production rates. Copyright © Taylor & Francis Group, LLC.


Mishra S.,Non Ferrous Materials Technology Development Center | Mitra R.,Indian Institute of Technology Kharagpur | Vijayakumar M.,Indian Defence Research And Development Laboratory
Journal of Alloys and Compounds | Year: 2010

Attempts have been made towards a novel process for the preparation of cellular silica with interconnected cells, tailored porosity and pore size distribution using a combination of hydrophobized fused silica powder and direct foaming methodology. The process has resulted into cellular silica tiles as large as 100 × 100 × 25 mm dimensions. The resulting ceramic foams sintered at 1100 °C, consisted of a highly interconnected network of spherical cells with densities as low as 10% of theoretical. The pore size distributions and cell size have been found in the range of 50-250 μm and ∼6-16 ppi, respectively. The microstructure has shown an open and interconnected porosity with an average permeability occurring in the region of ∼10-8 m2. The creation of highly densified cell walls and tortuous struts between the cells has led to foams with a comparatively high compressive strength and Young's modulus and with an excellent thermal shock properties. © 2010 Elsevier B.V. All rights reserved.


Mishra S.,Non Ferrous Materials Technology Development Center | Mitra R.,Indian Institute of Technology Kharagpur
Journal of Materials Science | Year: 2010

Cellular silica with improved framework, crosslinking, and stability properties are desirable for applications in thermal insulation. A process for the preparation of cellular silica foam with interconnected cells with tailored porosity and pore size distribution has been attempted. The silica foams have been prepared through two different methods; surfactant-and particle-based stabilization. The silica foams prepared through two different processes namely surfactant-stabilized foams (SSF) and particle-stabilized foams (PSF) have exhibited a wide range of differences in their structure which in turn have shown to affect the final properties of the foam. The cell size distributions in SSF (89 vol% porosity) and PSF (85 vol% porosity) have been found in the range of 50-250 μm (monomodal) and 4-10 μm and 50-100 μm (bimodal), respectively, whereas the cell counts of both have been found in close proximity. The microstructure of both the sintered SSF as well as PSF samples foams have shown an open and interconnected porosity with the permeability of both in the region of ∼10-8 m2. The mechanical (compressive) strength and Young's modulus of the PSF are a third of that in SSF. The structure-property relationship of both the SSF and PSF and their comparison have been discussed. © 2010 Springer Science+Business Media, LLC.

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