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Complexity of the KNa2ZrF7, KNa2HfF7, and KNa2(Hf,Zr)F7 compounds

Abstract

New mixed-cation fluorides KNa 2 HfF 7 ( Pmn 2 1 , a = 8.213(2) & Aring;, b = 6.126(2) & Aring;, c = 5.979(2) & Aring;, Z = 2) and KNa 2 (Hf,Zr)F 7 (refined composition KNa 2 Hf 0.44(1) Zr 0.56(1) F 7 ; Pmn 2 1 , a = 8.2210(8) & Aring;, b = 6.1288(6) & Aring;, c = 5.979 (1) & Aring;, Z = 2) together with isostructural KNa 2 ZrF 7 ( Pmn 2 1 , a = 8.221(2) & Aring;, b = 6.118(2) & Aring;, c = 5.994(2) & Aring;, Z = 2) have been synthesised in aqueous solutions and structurally characterised at room temperature by powder and single-crystal X-ray diffraction. The solid-solid phase transformations have been revealed during the differential scanning calorimetry experiments and further confirmed by temperature-dependent X-ray powder diffraction. It has been found that mixed-cation phases KNa 2 ZrF 7 , KNa 2 HfF 7 and KNa 2 (Hf,Zr)F 7 undergo irreversible phase transformations, which can be explained by their decomposition over 673 K. XPS analysis confirmed the presence of exclusively terminated fluorines around the transition metals and the absence of oxygen impurities in the crystal structures of compounds.

article Article

date_range 2024

language English

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Matselko Oksana

Poupon Morgane

Samolova Erika

Vaskova Zuzana

Kubikova Blanka

Netriova Zuzana

Micusik Matej

Boca Miroslav

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Crystal structure

DSC

Fluoride

Hafnium

Phase transition

Zirconium

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Effect of corrosion on flexural strength of reinforced concrete beams with polypropylene fibers

Abstract

An experimental study was performed to investigate the effects of polypropylene fibers on uncorroded and corroded reinforced concrete beams. Three different volume fractions of polypropylene fibers having 0, 0.5, and 1.5%, were tested at four corrosion levels of 0% and approximately 5, 7, and 9%. A full scale of an accelerated corrosion pool was used for the accelerated corrosion process. Reinforced concrete beams were used for an under monotonic bending test. The contribution of the actual corrosion levels of transverse and longitudinal reinforcement bars to the total corrosion levels were obtained from reinforcement bars fully extracted from concrete. Flexural strength, bond-slip, and moment-curvature relationships were examined for uncorroded and corroded reinforced concrete beams. A new model was developed to predict the flexural strength of corroded reinforced concrete beams. The proposed model for predicting the residual flexural strength of corroded beams was compared with test data published in previous studies. Furthermore, a novel model is presented for improved predictions between the actual and theoretically estimated corrosion mass losses, based on Faraday’s law, with the aid of fully extracted reinforcement bars. The model used to predict the flexural strength of corroded reinforced concrete beams with large sizes demonstrated good agreement with current and previously published literature data. In the case of corroded beams comprising differing amounts of polypropylene fibers, the performance of the corroded beams was limited by a fiber volume fraction of 1.5% at low corrosion levels.

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date_range 2018

language English

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