Synthesis and characteristics of fly ash and bottom ash based geopolymers–A comparative study

The research was carried out to develop geopolymers mortars and concrete from fly ash and bottom ash and compare the characteristics deriving from either of these products. The mortars were produced by mixing the ashes with sodium silicate and sodium hydroxide as activator solution. After curing and drying, the bulk density, apparent density and porosity, of geopolymer samples were evaluated. The microstructure, phase composition and thermal behavior of geopolymer samples were characterized by scanning electron microscopy, XRD and TGA-DTA analysis respectively. FTIR analysis revealed higher degree of reaction in bottom ash based geopolymer. Mechanical characterization shows, geopolymer processed from fly ash having a compressive strength 61.4 MPa and Young's modulus of 2.9 GPa, whereas bottom ash geopolymer shows a compressive strength up to 55.2 MPa and Young's modulus of 2.8 GPa. The mechanical characterization depicts that bottom ash geopolymers are almost equally viable as fly ash geopolymer. Thermal conductivity analysis reveals that fly ash geopolymer shows lower thermal conductivity of 0.58 W/mK compared to bottom ash geopolymer 0.85 W/mK.     

Mechanical properties of MgO–Al2O3–SiO2 glass-infiltrated Al2O3–ZrO2 composite

This work attempts to improve the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria stabilized) composite by infiltrating a glass (magnesium aluminum silicate glass) of lower thermal expansion on the surface at high temperature. The glass improved the strength of the composite at room temperature as well as at higher temperatures. There was a significant improvement in the Weibull modulus after the glass infiltration. Glass-infiltrated samples showed better thermal shock resistance. The magnitude of strength increment was found to be in the order of the surface residual stress generated by thermo-elastic properties mismatch between the composite and the infiltrated glass.     

Antibody library selection by the {beta}-lactamase protein fragment complementation assay

Protein fragment complementation assay (PCA) is based on the interaction between two protein partners (e.g. target antigen and antibody), which are genetically fused to the two halves of a dissected marker protein. Binding of the two partners reassembles the marker protein and hence reconstitutes its activity. In this work we have developed the first application of beta-lactamase-based PCA for the isolation of single chain Fv fragments (scFvs) binding to the human receptor RON from a na?ve library. Specific scFvs with the ability to immunoprecipitate could be isolated after a single round of PCA selection from an scFv repertoire previously pre-selected by phage display. Furthermore, the PCA was used to successfully map the epitopes recognized by the selected scFvs by screening them against a small library of random RON fragments.     

Using archaeal histones for precise DNA fragmentation

The fragmentation of DNA is a useful procedure for many molecular biology procedures. However, most methods used to fragment DNA are poorly controllable, and cannot be used to create small fragments. We describe a method to generate random DNA fragments of a predictable size to be cloned in expression vectors for the construction of display libraries. The DNA is allowed to form complexes with archaeal histones from Methanothermus fervidus (HMf) and the HMf/DNA core complex is naturally protected from nuclease DNaseI activity, giving rise to DNA fragments of approximately 60 bp and multiples thereof. We found that by varying the wt/wt ratio between DNA and HMf, the concentration of DNA and the incubation time with DNaseI, DNA fragments of desired size can be obtained. This approach should be applicable to the efficient fragmentation of DNA for the construction of phage display polypeptide libraries, as well as any other molecular biology procedures in which small DNA fragments of defined size are required.     

Hydroxy propyl cellulose capped silver nanoparticles produced by simple dialysis process

Silver (Ag) nanoparticles (∼6 nm) were synthesized using a novel dialysis process. Silver nitrate was used as a starting precursor, ethylene glycol as solvent and hydroxy propyl cellulose (HPC) introduced as a capping agent. Different batches of reaction mixtures were prepared with different concentrations of silver nitrate (AgNO₃). After the reduction and aging, these solutions were subjected to ultra-violet visible spectroscopy (UVS). Optimized solution, containing 250 mg AgNO₃ revealed strong plasmon resonance peak at ∼410 nm in the spectrum indicating good colloidal state of Ag nanoparticles in the diluted solution. The optimized solution was subjected to dialysis process to remove any unreacted solvent. UVS of the optimized solution after dialysis showed the plasmon resonance peak shifting to ∼440 nm indicating the reduction of Ag ions into zero-valent Ag. This solution was dried at 80 °C and the resultant HPC capped Ag (HPC/Ag) nanoparticles were studied using transmission electron microscopy (TEM) for their particle size and morphology. The particle size distribution (PSD) analysis of these nanoparticles showed skewed distribution plot with particle size ranging from 3 to 18 nm. The nanoparticles were characterized for phase composition using X-ray diffractrometry (XRD) and Fourier transform infrared spectroscopy (FT-IR).     

Nanostructured TiO2 for stone coating: assessing compatibility with basic stone’s properties and photocatalytic effectiveness

Bulletin of Engineering Geology and the Environment - Many building materials have been functionalized to achieve photocatalytic properties, namely self-cleaning and depolluting abilities, through...     

Wollastonite/hydroxyapatite scaffolds with improved mechanical,bioactive and biodegradable properties for bone tissue engineering

Wollastonite/hydroxyapatite composite scaffolds are proposed as bone graft. An investigation on scaffold with varying reinforcing wollastonite content fabricated by polymeric sponge replica is reported. The composition, sintering behavior, morphology, porosity and mechanical strength were characterized. All the scaffolds had a highly porous well-interconnected structure. A significant increase in mechanical strength is achieved by adding a 50% wollastonite phase. The most mechanically resistant (50/50) wollastonite/hydroxyapatite scaffolds were soaked in both simulated body fluid (SBF) and Tris–HCl solution in order to assess bioactivity and biodegradability. A carbo-hydroxyapatite layer formed on their surfaces when immersed in SBF. The biodegradability tests reveals that the composite scaffold shows a higher degradation rate compared to pure hydroxyapatite used as comparison. These results demonstrate that the incorporation of a 50% of wollastonite phase in hydroxyapatite matrix is effective in improving the strength and the bioactive and biodegradable properties of the porous scaffolds.     

An in vivo Evaluation of Ultra-fine Grained Titanium Implants

The present work focuses mainly on an in vivo evaluation of ultra fine grained titanium(UFG-Ti) obtained by severe plastic deformation(SPD).The SPD on commercially produced Grade 2 titanium(Cp-Ti) resulted in the refinement of the grain size by several orders of magnitude.Polished surfaces having similar roughness from both UFG-Ti and Cp-Ti were prepared.In vitro test revealed the presence of fibronectin,which was involved in the attachment of the cells to the substrate.Phase contrast micrographs showed the...     

Cobalt‐Catalysed Addition of Allylidene Dipivalate to Aldehydes. A Formal Homoaldol Condensation

A Co(I)‐catalysed condensation of allylidene dipivalate with aldehydes to give (Z)‐4‐hydroxybut‐1‐enyl pivalates in 62 to 87% isolated yields, is reported. Reactions are run in acetonitrile at 0 or 25 °C depending on the nature of the aldehyde, and exploiting the Co(II)/Zn(0) redox couple for the preparation of the catalytic Co(I) species.     

Stereolitography of ceramic suspensions

The need of fast production of prototypes of complex shapes in very short time lead to the development in the last years of many additive rapid prototyping (RP) technologies for the production of single objects or of very limited series. The new fabrication concept allowed the construction of complex parts, starting from a 3D-CAD model, without using a mould. However, most of these additive processes produce polymeric objects and only recently the laser sintering of metal powders has been commercially introduced. In this work the production of ceramic objects by stereolithography is presented starting from the development of UV curable pre-ceramic suspensions for free form fabrication of alumino-silicate parts. The suspensions are characterized by 40%–50% by volume of powder content and by a reactivity and a viscosity compatible with their application in stereolithography. The ceramic green is built in a stereolithographic system operating with a He-Cd laser (325 nm). Then, the ceramic objects are obtained by pyrolisis of the organic binder and subsequent sintering of the green at 1600 °C. Finally, a characterisation of the mechanical properties and of the microstructure of the samples is presented.