Characterisation of mechanical and thermal properties in flax fabric reinforced geopolymer composites

This paper presents the mechanical and thermal properties of flax fabric reinforced fly ash based geopolymer composites. Geopolymer composites reinforced with 2.4, 3.0 and 4.1 wt% woven flax fabric in various layers were fabricated using a hand lay-up technique and tested for mechanical properties such as flexural strength, flexural modulus, compressive strength, hardness, and fracture toughness. All mechanical properties were improved by increasing the flax fibre contents, and showed superior mechanical properties over a pure geopolymer matrix. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) studies were carried out to evaluate the composition and fracture surfaces of geopolymer and geopolymer/flax composites. The thermal behaviour of composites was studied by thermogravimetric analysis (TGA) and the results showed significant degradation of flax fibres at 300 °C

Long term behaviour of ferronickel slag inorganic polymers in various environments

Δημοσίευση σε επιστημονικό περιοδικόSummarization: In the present experimental study the long term behaviour of ferronickel slag-based inorganic polymers in various environments is assessed. Specimens were synthesised by mixing ferronickel slag with alkali activator solution. After curing, heating and setting, the durability and structural integrity of the specimens were studied by immersion in various solutions, subjection to accelerated freeze-thaw cycles and high temperature heating. The experimental results show that inorganic polymers exhibit very good behaviour in most cases; the compressive strength remains at quite high values and their matrix retains most of its structural integrity.Παρουσιάστηκε στο: Fresenius Environmental Bulleti

Use of analytical techniques for identification of inorganic polymer gel composition

Δημοσίευση σε επιστημονικό περιοδικόSummarization: In the present experimental study, a number of analytical techniques were used to identify the composition of gel and thus elucidate to a certain extent the mechanisms involved during synthesis of inorganic polymers. The raw materials used, low calcium slag from a ferronickel plant and commercial glass, were alkali activated by Na2SiO3 and KOH solutions. X-ray diffraction (XRD) is used to identify new formed phases; deconvolution of the amorphous peaks in X-ray powder diffraction patterns enables the quantitative estimation of the amorphous phases present. The morphology and composition of the inorganic polymer gel may be defined by optical reflection microscopy (ORM) and scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) is a useful tool for the identification of specific molecular structures including Si–O–Si and Al–O bonds, which define the degree of polysialation. Thermogravimetric analysis (TG) determines water evaporation rates in inorganic polymer structures by recording the weight loss under controlled heating. Finally, the effect of the presence in the starting mixture of heavy metals such as Pb or Cu and anions such as NO3 − or SO4 2− on the quality of the gel formed and subsequently on the compressive strength of inorganic polymers are studied and discussed.Παρουσιάστηκε στο: Journal of Materials Scienc

Effect of additives on the compressive strength of slag-based inorganic polymers

Δημοσίευση σε επιστημονικό περιοδικόSummarization: The present paper aims to assess the effect of various additives on the compressive strength of inorganic polymers (geopolymers) synthesised using low Ca electric arc ferronickel slag and alkali activating solutions. The main operating parameters include pre-curing (48 hours), temperature (40 to 80 o C), heating time (24 or 48 h) and aging period (7 days). Addition of kaolinite, pozzolan, fly ash, red mud or CaO in the initial mixture has a detrimental effect on the final compressive strength. Addition of pulverised silica sand improves strength slightly, whereas addition of commercial glass results in strength values exceeding 60 MPa. XRD analysis was carried out to identify new formed phases and the degree of amorphicity, while SEM and element mapping analysis were used to identify the morphology of the final products as well as to elucidate to a certain degree the mechanisms involved in inorganic polymer synthesisΠαρουσιάστηκε στο: Global NES

Quantification of three beta-lactam antibiotics in breast milk and human plasma by hydrophilic interaction liquid chromatography/positive-ion electrospray ionization mass spectrometry

The use of cephalosporins during breast feeding raises several issues, including the risk of drug exposure through breast milk for the infant. In this paper, a hydrophilic interaction liquid chromatography/positive ion electrospray mass spectrometric assay (HILIC/ESI-MS) was developed for the quantitation of cefuroxime, cefoxitin, and cefazolin in breast milk and human plasma. The assay was based on the use of small sample size, 25 μL of biological samples, following acetonitrile precipitation of proteins and filtration that enabled injection into the HILIC/ESI-MS system. All analytes and the internal standard, alfuzosin, were separated by using a ZIC®-HILIC analytical column (150.0 × 2.1 mm i.d., particle size 3.5 µm, 200 Å) with isocratic elution. The mobile phase was composed of a 6% 12.5 mM ammonium acetate water solution in acetonitrile and pumped at a flow rate of 0.25 mL min-1. The assay was linear over a concentration range of 0.2 to 5 µg mL-1 and 0.4 to 20 µg mL-1 for all the analytes in breast milk and in human plasma, respectively. Intermediate precision was found to be less than 4.2% over the tested concentration ranges. A run time of less than 12 min for each sample made it possible to analyze a large number of biological samples per day. The method is the first reported application of HILIC in the analysis of antibiotics in breast milk and human plasma and it can be used to support a wide range of clinical studies. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd