Entity

Time filter

Source Type


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.


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.


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.


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.

Discover hidden collaborations