Effects of Ce+Gd on the structural features and thermal stability of iron-boron-phosphate glasses

2017 ◽  
Vol 201 ◽  
pp. 170-179 ◽  
Author(s):  
Fu Wang ◽  
Zhiwei Fang ◽  
Hong Wang ◽  
Qilong Liao ◽  
Hanzhen Zhu
2008 ◽  
Vol 254 (16) ◽  
pp. 5129-5133 ◽  
Author(s):  
Xiaoxue Zhang ◽  
Mari Honkanen ◽  
Mikael Järn ◽  
Jouko Peltonen ◽  
Viljami Pore ◽  
...  

2013 ◽  
Vol 118 (1) ◽  
pp. 338-345 ◽  
Author(s):  
Oleg V. Surov ◽  
Marina I. Voronova ◽  
Vladimir P. Barannikov ◽  
Gennady P. Shaposhnikov

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4058
Author(s):  
M. Mohan Babu ◽  
P. Syam Prasad ◽  
P. Venkateswara Rao ◽  
S. Hima Bindu ◽  
A. Prasad ◽  
...  

Zirconium doped calcium phosphate-based bioglasses are the most prominent bioactive materials for bone and dental repair and regeneration implants. In the present study, a 8ZnO–22Na2O–(24 − x)CaO–46P2O5–xZrO2 (0.1 ≤ x ≤ 0.7, all are in mol%) bioglass system was synthesized by the conventional melt-quenching process at 1100 °C. The glass-forming ability and thermal stability of the glasses were determined by measuring the glass transition temperature (Tg), crystallization temperature (Tc), and melting temperature (Tm), using differential thermal analysis (DTA). The biological activity of the prepared samples was identified by analyzing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy dispersive spectra (SEM-EDS), before and after immersion in simulated body fluid (SBF) for various intervals of 0, 1 and 5 days, along with the magnitude of pH and the degradation of glasses also evaluated. The obtained results revealed that the glass-forming ability and thermal stability of glasses increased with the increase in zirconia mol%. The XRD, FTIR, and SEM-EDS data confirmed a thin hydroxyapatite (HAp) layer over the sample surface after incubation in SBF for 1 and 5 days. Furthermore, the development of layer found to be increased with the increase of incubation time. The degradation of the glasses in SBF increased with incubation time and decreased gradually with the increase content of ZrO2 mol% in the host glass matrix. A sudden rise in initial pH values of residual SBF for 1 day owing to ion leaching and increase of Ca2+ and PO43− ions and then decreased. These findings confirmed the suitability of choosing material for bone-related applications.


2006 ◽  
Vol 519-521 ◽  
pp. 389-394 ◽  
Author(s):  
Dalibor Vojtěch ◽  
Jan Verner ◽  
Barbora Bártová ◽  
Karel Saksl

Rapidly solidified (RS) Al-TM (TM = transition metal) alloys are perspective materials from scientific, as well as technological point of view. Generally, they are produced by the melt atomization or by the melt spinning. Subsequent compaction is commonly performed by the hot extrusion. Since transition metals, such as Cr, Fe, Ni, Zr, Ti, Mn and others, have low diffusion coefficients in solid aluminium (lower by several orders of magnitude than those of common alloying elements like Cu, Si, Mg, Zn etc.) the RS Al-TM alloys are characterized by a high thermal stability. In this paper, several RS Al-TM (TM = Cr, Fe, Ti, Mn, Ni) alloys prepared by the melt spinning and melt atomization are compared to commercially available 2xxx, 6xxx and 7xxx wrought alloys. The main structural features of both RS and wrought alloys are described. The RS alloys are characterized by the presence of micro and nano-scale crystalline and/or quasi-crystalline phases and supersaturated solid solutions. The elevated-temperature behaviour is compared for both groups of materials. The thermal stability of the investigated materials is determined by room temperature hardness measurements after various annealing regimes and a high thermal stability of the RS alloys is demonstrated. The microstructural changes and phase transformations occurring in the investigated materials upon heating are described. In the Al-TM alloys, very slow decomposition of the supersaturated solid solutions, precipitation and decomposition of the metastable quasi-crystalline phases occur.


2014 ◽  
Vol 88 (8) ◽  
pp. 1329-1335 ◽  
Author(s):  
O. V. Surov ◽  
M. I. Voronova ◽  
E. V. Plevina ◽  
V. P. Barannikov ◽  
P. R. Smirnov ◽  
...  

1993 ◽  
Vol 295 (3) ◽  
pp. 827-831 ◽  
Author(s):  
A Villa ◽  
L Zecca ◽  
P Fusi ◽  
S Colombo ◽  
G Tedeschi ◽  
...  

Investigations were performed on the structural features responsible for kinetic thermal stability of a thermostable carboxypeptidase from the thermoacidophilic archaebacterium Sulfolobus solfataricus which had been purified previously and identified as a zinc metalloprotease [Colombo, D'Auria, Fusi, Zecca, Raia and Tortora (1992) Eur. J. Biochem. 206, 349-357]. Removal of Zn2+ by dialysis led to reversible activity loss, which was promptly restored by addition of 80 microM ZnCl2 to the assay mixture. For the first-order irreversible thermal inactivation the metal-depleted enzyme showed an activation energy value of 205.6 kJ.mol-1, which is considerably lower than that of the holoenzyme (494.4 kJ.mol-1). The values of activation free energies, enthalpies and entropies also dropped with metal removal. Thermal inactivation of the apoenzyme was very quick at 80 degrees C, whereas the holoenzyme was stable at the same temperature. These findings suggest a major stabilizing role for the bivalent cation. Chaotropic salts strongly destabilized the holoenzyme, showing that hydrophobic interactions are involved in maintaining the native conformation of the enzyme. However, the inactivation rate was also increased by sodium sulphate, acetate and chloride, which are not chaotropes, indicating that one or more salt bridges concur in stabilizing the active enzyme. Furthermore, at the extremes of the pH-stability curve, NaCl did not affect the inactivation rate, confirming the stabilizing role of intramolecular ionic bonds, as a pH-dependent decrease in stability is likely to occur from breaking of salt bridges involved in maintaining the native conformation of the protein.


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