Review on titanium and titanium based alloys as biomaterials for orthopaedic applications.

Porous silica and carbon derived materials from rice husk pyrolysis char

https://www.tandfonline.com/doi/pdf/10.1080/21870764.2018.1539210

Rice husk/rice husk ash as an alternative source of silica in ceramics: A review

Synthesis of high specific surface area silica aerogel from rice husk ash via ambient pressure drying

In recent years, silica gels have developed a lot of interest due to their extraordinary properties and their existing and potential applications in science and technology. Silica gel has a wide range of applications such as a desiccant, as a preservation tool to control humidity, as an adsorbent, as a catalyst and as a cata-lyst support. Silica gel is a rigid three-dimensional network of colloidal silica, and is classified as: aqua-gel, alco-gel, xero-gel and aero-gel. Out of all known solid porous materials, aero-gels are particularly known for their high specific surface area, high porosity, low bulk density, high thermal insulation value, ultra low dielectric constant and low index of refraction. Because of these extraordinary properties silica aero-gel has many commercial applications such as thermal window insulation, acoustic barriers, super-capacitors and catalytic supports. However, monolithic silica aero-gel has been used extensively in high energy physics in Cherenkov radiation detectors and in shock wave studies at high pressures, inertial confinement fusion (ICF) radio-luminescent and micrometeorites. Silica gel can be prepared by using various sol gel precursors but the rice husk (RH) is considered as the cheapest source for silica gel production. Rice husk is a waste product abundantly available in rice producing countries during milling of rice. This review article aims at summarizing the developments carried out so far in synthesis, properties, characterization and method of determination of silica, silica gel, silica aero-gel and silica xero-gel. The effect of synthesis parameters such as pH, temperature of burning the rice husk, acid leaching prior to formation of rice husk ash (RHA) on the properties of final product are also described. The attention is also paid on the application of RH, RHA, sil-ica, silica aero-gel and silica xero-gel. Development of economically viable processes for getting rice husk silica with specific properties assumes importance at this juncture. Copyright © 2012 by BCREC UNDIP. All rights reserved. Received: 23th November 2011, Revised: 09th January 2012, Accepted: 10th January 2012 [How to Cite : R. Prasad, and M. Pandey. (2012). Rice Husk Ash as a Renewable Source for the Production of Value Added Silica Gel and its Application: An Overview. Bulletin of Chemical Reaction Engineering & Catalysis , 7 (1): 1-25. doi:10.9767/bcrec.7.1.1216.1-25 ] [How to Link / DOI : http://dx.doi.org/10.9767/bcrec.7.1.1216.1-25 ]

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Rice Husk Ash as a Renewable Source for the Production of Value Added Silica Gel and its Application: An Overview

SiO 2 –Na 2 O–CaO based bioglass-ceramics was synthesized through sol–gel route using rice husk ash as silica source. The decomposition behavior of gel was evaluated. Sodium–calcium–silicate phases were crystallized above 700 °C. Pellet made of glass-ceramics powder was sintered at 900 °C. In vitro bioactivity and biodegradability of glass-ceramics were investigated by incubation in simulated body fluid and Tris buffer solution respectively. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were used to monitor the surface deposition on glass-ceramics during incubation. The material showed a good bioactivity with a formation of carbonated hydroxy apatite phase in 3 days of incubation. A quick degradation of the material was observed in Tris solution associated with an increase of pH due to the dissolution of Ca 2+ and Na + ionic species. All these results suggest the glass-ceramics, prepared utilizing rice husk ash, would be a low cost biomaterial for potential biomedical applications.

Sol―gel synthesis of bioglass-ceramics using rice husk ash as a source for silica and its characterization

Silica aerogel was prepared from rice husk ash by sol-gel process followed by ambient pressure drying. Silica was extracted from ash as sodium silicate by boiling it in sodium hydroxide solution. Sodium silicate was neutralized with nitric acid to form silica gel. To prepare aerogel, first the pore water of the gel was exchanged by ethanol and then surface modification was done by aging alcogel in tetraethylorthosilicate (TEOS)/ethanol solution. Before drying, TEOS/ethanol solvent was exchanged with n-heptane. Capillary stress and shrinkages were greatly reduced due to the low surface tension of n-heptane. The prepaid aerogel was a light and crack-free solid, with bulk de nsity cf 0.67 g.cm−3, porosity of about 80%, total pore volume of 3.1 cm3.g−1 and specific surface area of about 273 m2.g−1. The nature of surface modification and thermal stability of the aerogel was studied by FTIR and DSC/TG respectively.

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Preparation of Silica Aerogel by Ambient Pressure Drying Process using Rice Husk Ash as Raw Material

Silica ceramics were prepared using three types of raw materials derived from rice husk. Cleaned husk and acid-leached husk were burned at 700°C to get brown ash (BA) and white ash, respectively. The third type was silica gel (SG) derived from BA through the alkaline extraction of silica from ash followed by acid neutralization. Granulated powders were pressed and pellets were sintered at 700–1400°C range. Phase-formation behavior, densification characteristics, and mechanical strength of ceramics were investigated and correlated with microstructural features. Ceramics made of SG showed the highest density and mechanical strength among all. All the ceramics were initially amorphous and transformed into crystalline silica above a specific sintering temperature. Microstructure shows the formation of cracks in the ceramics when they contain cristobalite phases. Amorphous-to-crystalline phase transformation temperature in different types of silica source was dependent on the amount of impurity and residual hy...

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Effect of sintering temperature on phase-formation behavior and mechanical properties of silica ceramics prepared from rice husk ash

Effect of sintering temperature on mechanical behaviour and bioactivity of sol–gel synthesized bioglass-ceramics using rice husk ash as a silica source

Rice husk ash has been used to prepare amorphous silica bioactive ceramics. Three varieties of silica powders, namely brown ash, white ash and silica gel containing 96.0, 99.8 and 99.9% silica respectively, were used to prepare silica ceramics. The bioactivity and biodegradability properties of these ceramics were evaluated. The formation of crystalline apatite was observed on all the specimens in simulated body fluid. The phase composition, morphology and calcium/phosphorous ratio of the apatite layer formed were evaluated by X-ray Diffraction, Scanning Electron Microscopy and Energy Dispersive Spectroscopy. Controlled biodegradability of amorphous silica in Tris buffer solution was found. These results suggest that the amorphous silica derived from rice husk ash is a promising and cost effective biomaterial.

J.P. Nayak

Papers

Sol―gel synthesis of bioglass-ceramics using rice husk ash as a source for silica and its characterization

Preparation of Silica Aerogel by Ambient Pressure Drying Process using Rice Husk Ash as Raw Material

Effect of sintering temperature on phase-formation behavior and mechanical properties of silica ceramics prepared from rice husk ash

Effect of sintering temperature on mechanical behaviour and bioactivity of sol–gel synthesized bioglass-ceramics using rice husk ash as a silica source

Bioactivity Characterization of Amorphous Silica Ceramics Derived from Rice Husk Ash