Keywords : porosity

Concrete Electrical Resistivity at Varied Water, Chloride Contents and Porosity – Experiment, Modelling & Application

Yu Wang; Hayder Oleiwi; Nan Xiang

Advanced Materials Letters, 2020, Volume 11, Issue 7, Pages 1-4
DOI: 10.5185/amlett.2020.071536

Understanding and characterizing the relationship between the electrical resistivity and the major influencing factors of the concrete have been all the time a topical research in relation to structural durability. This paper reports an experimental study on the influences of water and chloride contents, and porosity on the electrical resistivity of the Portland cement concrete. The results indicate that the electrical resistivity has a strong correlation with the water and chloride contents in concrete. A new characteristic model has been proposed to represent the correlation. The proposed model has been implemented into a numerical modelling case study of cathodic protection for reinforced concrete structure in saline environment.

Porous hydroxyapatite scaffolds fabricated from nano-sized powder via honeycomb extrusion

Mohammed Elbadawi; James Meredith; Mosalagae Mosalagae; Ian M. Reaney

Advanced Materials Letters, 2017, Volume 8, Issue 4, Pages 377-385
DOI: 10.5185/amlett.2017.7063

In this study, we have developed hydroxyapatite (HA) scaffolds for synthetic bone graft from nano-sized HA particles using ceramic extrusion. We also demonstrate that these HA scaffolds show enhanced compressive strength (29.4 MPa), whilst possessing large pore sizes (> 600 µm) that are suitable for bone grafting. The extrusion process involved forming a ceramic paste by mixing the HA powder with a binder and distilled water. The ceramic paste was then fabricated using a ram extruder that was fitted with a honeycomb die to impart large, structured pores. Several green bodies were extruded and then subjected to the same drying and thermal debinding treatment. The samples underwent three different sintering temperatures and two varied dwell times, in order to determine the optimum sintering parameters. The scaffolds were then analysed for their chemical, physical, mechanical and biological properties to elucidate the effects of the sintering parameters on extruded HA scaffolds. The results revealed that the nano-sized particles exhibited a high sinterability, and XRD analysis showed phase purity until 1300 o C. At 1300 o C, trace amounts of phase impurities were detected, however, scaffolds sintered at this temperature exhibited the highest mean compressive strength. The findings demonstrated that traces of phase impurities were not detrimental to the scaffold’s compressive strength. In addition, scanning electron microscopy and density measurements revealed a highly densified solid phase was attained.

Contact Angle Measurement Studies On Porous Anodic Alumina Membranes Prepared Using Different Electrolytes

P. Ramana Reddy; Ajith K. M.;N. K. Udayashankar

Advanced Materials Letters, 2016, Volume 7, Issue 5, Pages 398-401
DOI: 10.5185/amlett.2016.6230

This paper investigates the effect of pore widening duration on the wetting properties of nanostructured porous anodic alumina (PAA) membranes fabricated using sulphuric and oxalic acid as electrolytes by two step anodization process. XRD analysis shows that prepared PAA membranes were amorphous in nature. With increasing of pore widening durations from 0 to 120 min, the contact angle of PAA membranes varied from 21 to 78Ëš. It was noticed that PAA membranes were hydrophilic in nature in the present of water medium. In the presence of acetone medium, PAA membranes prepared with 1hr pore widening time showed super hydrophilic behaviour. 

 Fabrication And Plasmonic Characterization Of Au Nanowires With Controlled Surface Morphology

Ina Schubert; Wilfried Sigle; Loic Burr; Peter A. van Aken; Christina Trautmann; Maria Eugenia Toimil-Molares

Advanced Materials Letters, 2015, Volume 6, Issue 5, Pages 377-382
DOI: 10.5185/amlett.2015.5721

Gold nanowires are attracting great attention due to their ability to sustain surface plasmons and are thus promising candidates for sensing applications such as surface enhanced Raman and infrared spectroscopy. Controlling all nanowire parameters is crucial to adjust the resonance wavelengths and to obtain high electric field enhancements. We have fabricated Au nanowires with controlled dimensions and surface morphology by electro-deposition of Au and Au-Ag nanowires in the pores of ion-track-etched polymer templates. Smooth and rough nanowires are fabricated by the use of different polymer types. By dealloying of Au-Ag wires, porous Au wires are being created. In addition, we have analyzed the surface plasmonic properties of smooth and porous Au nanowires by scanning transmission electron microscopy combined with electron energy-loss spectroscopy. Our results reveal the excitation of five different longitudinal modes in the smooth as well as in the porous Au wire. The resonance energies of the porous wire are red-shifted compared to the energies of a smooth Au wire with same dimensions, which demonstrates that the surface morphology of the nanowire is an important parameter to tune the multipole surface plasmon modes to specific energies. Knowledge on the plasmonic properties of nanowires dependent on their surface morphology is indispensable for their efficient application for sensor technology.

On The Molecular Basis Of Silica Gel Morphology

Agnieszka Kierys; Jacek Goworek; Michal Rawski; Istvan Halasz

Advanced Materials Letters, 2015, Volume 6, Issue 1, Pages 40-46
DOI: 10.5185/amlett.2015.amwc1194

Distinction between molecular constitutions of differently made silica gels succeeded only recently.  This paper seeks relationship between the different molecular structures of acid and base set gels and their morphology and pore structure.  Gels were fabricated from both tetraethyl orthosilicate, TEOS, in organic solvent environment and from an economically more desirable, commercial, aqueous Na-silicate solution.  When their gelling was performed in the pores of an organic resin, Amberlite, further molecular differences were observed, along with associated morphology and porosity differences.  We present here unprecedented atomically resolved TEM pictures that visually prove that the molecular structures of gels deduced from their 29 Si NMR and Raman spectra are real, which could also be demonstrated by computer models.