Corrosion behavior and in vitro biocompatibility of Zr–Al–Co–Ag bulk metallic glasses: An experimental case study

Ni- and Cu–free Zr–Al–Co–Ag bulk metallic glasses (BMGs) were synthesized by copper mold casting. The effects of Ag addition for partially replacing Co of Zr₅₃Al₁₆Co₃₁ BMG on the corrosion behavior, surface chemistry and in vitro biocompatibility of BMGs were investigated. The Zr–Al–Co–Ag BMGs are spontaneously passivated with low passive current densities in phosphate buffered saline (PBS) solution. Partial substitution of Co by Ag is effective in improving the corrosion resistance of the Zr–Al–Co BMG. X-ray photoelectron spectroscopy (XPS) measurements reveal that the Ag addition increases the concentration of Zr and decreases the concentration of Al in the surface passive film of BMGs, which is responsible for the enhanced corrosion resistance of Zr–Al–Co–Ag BMGs. Mouse MC3T3-E1 pre-osteoblast cell proliferation results and morphology observations show that the Zr–Al–Co–Ag BMGs exhibit comparable cell viability and proliferation activity with those of Ti–6Al–4V alloy, demonstrating their good biocompatibility. The high corrosion resistance in PBS and low in vitro cytotoxicity of Zr–Al–Co–Ag BMGs suggest an initial biocompatibility for biomedical applications.     

Rheological and thermodynamic behavior of calcium aluminosilicate melts within the anorthite–wollastonite–gehlenite compatibility triangle

For melts within the compatibility triangle anorthite–wollastonite–gehlenite (An–Wo–Geh) (CaAl₂Si₂O₈–CaSiO₃–Ca₂Al₂SiO₇), the relationships between the chemical composition, the melt structure, and the rheological and thermodynamic properties are studied for each of the boundary lines, i.e. the An–Wo, Wo–Geh and Geh–An join. The influences of the degree of polymerization of the structural network and the amount of Al–O–Al linkages on the fragility and the configurational entropy of the melts are studied along the boundary lines. For the An–Wo join, the degree of polymerization dominates the responses of both fragility and configurational entropy to compositional variations. For the Wo–Geh and Geh–An joins, the amount of the Al–O–Al linkages dominates those responses. It is found that the depolymerization of the structural network and the formation of Al–O–Al linkages increase the fragility of the melt and the degree of structural disordering.     

Melting Diagrams of the Quaternary Systems Ga–In–As–Ge and Ga–In–As–Sn

Equilibria between quaternary liquid phases Ga–In–As–Ge(–Sn) and the ternary solid phase Ga–In–As have been calculated by application of the KRUPKOWSKI formalism on the excess free enthalpy. Experimental liquidus data were obtained from solubility experiments in a LPE equipment. Results of calculation and experimental liquidus data are compared.     

Heavy-tail properties of relaxation time distributions underlying the Havriliak–Negami and the Kohlrausch–Williams–Watts relaxation patterns

A detailed discussion of asymptotic properties of the Havriliak–Negami and the Kohlrausch–Williams–Watts relaxation time distributions is presented. The heavy-tail property of the Havriliak–Negami relaxation time distribution, leading to the infinite mean relaxation time, is discussed. In contrast, the existence of the finite mean relaxation time for the Kohlrausch–Williams–Watts response is shown. The discussion of the Cole–Davidson and the Cole–Cole cases is also included. Using the Tauberian theorems we show that these properties are determined directly by the asymptotic behavior of the considered empirical functions.     

Crystal Structure of Potentially Mesomorphic 4-Nonyloxyphenyl-4'-Metacryloyloxy-Benzoate CH2=C(CH3)–COO–C6H4–COO–C6H4–O–С9Н19

Crystallography Reports - The crystal structure of 4,4'-substituted phenyl benzoate CH2=C(CH3)–COO–C6H4–COO–C6H4–O–С9Н19 has been investigated by...     

Melting enthalpy ΔHm for describing glass forming ability of bulk metallic glasses

A new melting enthalpy ΔH_m criterion for the prediction of glass forming ability (GFA) of alloys is proposed and five Zr–Al–Ni–Cu bulk metallic glasses (BMG) with critical dimension Z_max up to ? 7.5 mm are also developed by us in the light of the optimum ΔH_m of Zr–Al–Ni–Cu alloy system. And then, we researched the relationships between ΔH_m and two GFA parameters (critical cooling rate R_c and Z_max) of five bulk metallic glass (BMG) systems, such as Mg–Ni–Nd, Pd–Cu–Si, La–Al–Ni–Cu, Zr–Al–Ni–Cu and Zr–Ti–Ni–Cu–Be, respectively. The results show that the relationships between ΔH_m and R_c are all concave upward parabolas, and the optimum ΔH_ms for Mg–Ni–Nd, Pd–Cu–Si, Zr–Al–Ni–Cu, Zr–Ti–Ni–Cu–Be and La–Al–Ni–Cu are 10.3960 kJ mol^?1, 21.2202 kJ mol^?1, 19.7146 kJ mol^?1, 18.1455 kJ mol^?1 and 13.1558 kJ mol^?1, respectively. On the contrary, the relationships between ΔH_m and Z_max are all concave downward parabolas, and the optimum ΔH_ms for Mg–Ni–Nd, Pd–Cu–Si, Zr–Al–Ni–Cu, Zr–Ti–Ni–Cu–Be and La–Al–Ni–Cu are 10.5530 kJ mol^?1, 21.0830 kJ mol^?1, 19.6603 kJ mol^?1, 19.7231 kJ mol^?1 and 13.1173 kJ mol^?1, respectively. Furthermore, other BMGs’ R_cs or Z_maxs predicted by above-mentioned relationships satisfactorily agree with the tested results, which indicates that these relationships are reliable. However, the predicted results are reliable only if the main components are similar with the fitted BMGs or the additive is sparkle enough that the alloy’s character does not change. On the whole, the ΔH_m can act as a criterion for quickly predicting the alloy’s GFA and be helpful for the development of new BMGs.     

X-Ray Diffraction and Thermographic Study of Mesomorphic 4-Acylphenyl 4'-Nonyloxybenzoate CH3C(O)C6H4–OC(O)–C6H4–OC9H19

Crystallography Reports - The structure and thermal properties of mesomorphic phenyl benzoate CH3–C(O)–C6H4–OC(O)–C6H4–OC9H19 (I) were studied by differential scanning...     

Crystallization behavior of Ce70−xAl10Cu20Cox (x = 0, 1, 3, 5 at.%) amorphous alloys

The effect of Co addition (substituting for Ce) on crystallization behavior of Ce₇₀Al₁₀Cu₂₀ amorphous alloys has been investigated using X-ray diffraction (XRD), differential thermal analysis (DTA) and transmission electron microscopy (TEM). The Co addition has an obvious effect on topological short-range ordering of Ce–Al–Cu–(Co) amorphous alloys. Moreover, the Co addition can slightly improve the thermal stability of Ce–Al–Cu based amorphous alloys. The 1 and 3 at.% Co additions do not obviously change the crystallization behavior of the Ce–Al–Cu–(Co) amorphous alloys, and the final crystallization products are FCC–CeAlCu(Co)O. However, the 5 at.% Co addition can alter the crystallization behavior of the Ce₇₀Al₁₀Cu₂₀ amorphous alloys. Proper content of Co can effectively suppress the formation of oxide phases during annealing of the Ce–Al–Cu–(Co) amorphous alloys.     

Thermodynamic restrictions of LPE of bismuth-containing А3В5 solid solutions

A heterophase equilibrium estimation procedure is proposed for systems InBiAsSb and GaInBiAsSb using the simple solution model and a ‘virtual’ GaBi compound. Thermodynamic characteristics and crystal-chemical parameters of the GaBi compound have been determined for the calculation with the linear interpolation method. Phase equilibrium in In–Bi–As–Sb and Ga–In–Bi–As–Sb systems has been analyzed for the 650–780 K temperature range. The existence limits for solid solutions have been set and the thermodynamic restrictions characterizing the capacity for synthesis have been ascertained. The data obtained may be useful in optimization of LPE methods.     

Aluminum lactate – An attractive precursor for sol–gel synthesis of alumina-based glasses

A novel aluminum precursor, aluminum lactate (Al(lact)₃), was used in the sol–gel synthesis of alumina-based systems. The peculiar chelation properties of aluminum lactate in aqueous solution make this precursor quite attractive for the sol–gel synthesis of alumina-containing materials. Based on the reaction of aluminum lactate with different precursors such as phosphorus, boron, fluorine and others, (Na₂O–)Al₂O₃–P₂O₅, (Na₂O–)Al₂O₃–B₂O₃, (Na₂O–)Al₂O₃–B₂O₃–P₂O₅, (Na–)Al–P–O–F, amorphous gels and glasses were prepared. The local structures of glasses prepared by both sol–gel and melt-cooling methods were compared by using solid state NMR.     

Atomic and electronic structures of nanometer sized silica particles

The Austin Model 1 semi-empirical method combined with geometry optimization procedure was used to study atomic and electronic structures of nanoscale silica particles containing up to 192 atoms (64 Si and 128 O). Twofold Si–O rings were found to dominate in nanometer sized particles. The fraction of larger rings increases with increasing particle sizes. Bond length and bond angle distributions were calculated. The shortest Si–O, O–O and Si–Si interatomic distances are approximately 1.7, 3.0 and 3.3 Å, respectively. Average O–Si–O and Si–O–Si bond angles are approximately 110^∘ and 130^∘. Average electronic energy band gap is 6.9 eV.     

Crystallization of Co-based amorphous alloys under the impact of the ion irradiation and recovery of the amorphous phase

Crystallization behavior of the amorphous phase in the Co–Fe–B–Si alloy system was investigated by X-ray diffraction technique under the influence both of thermal and irradiation activation. Crystallization starting temperature decreases by 200–300 ^°C under the influence of the irradiation. After partial crystallization of the amorphous alloy under the action of the irradiation annealed below the thermal crystallization temperature, the amorphous phase was again formed while annealing the alloy without irradiation. During irradiation and thermal annealing formation of the new metastable phase has been discovered with the diffraction pattern similar to the previously discovered cubic aperiodical phase in the Fe–Nb–Cu–B–Si alloy.     

Synthesis and crystal structure of a novel polymeric silver(I) complex

The complex of [Ag₂(μ–L)₂(μ–NO₃)₂]_n, where L?=?2–methyl–5–(2–pyridyl)–1,3,4–oxadiazole, has been synthesized and characterized by single–crystal X–ray diffraction analysis. The crystals are in triclinic system with space group P–1. Complex [Ag₂(μ–L)₂(μ–NO₃)₂]_n is a polymeric silver(I) complex bridged through the 1,3,4–oxadiazole rings and the nitrate ions, and the center Ag1(I) atoms have distorted trigonal bipyramidal geometries [AgN₃O₂].     

Free volume and viscosity of Fe–Co–Cr–Mo–C–B–Y bulk metallic glasses and their correlation with glass-forming ability

In this work, the variation of the glass-forming ability (GFA) in Fe–Co–Cr–Mo–C–B–Y alloy system with Co addition has been investigated from the viewpoints of non-isothermal viscosity and free volume. The best GFA for the alloy containing 7% Co is found to closely relate with its highest viscosity, and the minimum sizes and lowest concentrations of the intermediate and largest open volumes. The results may provide more insights into the formation mechanism of metallic glasses.     

Correlation between bulk and surface properties in Cd–X (X = Hg,Mg) liquid alloys

A theoretical investigation of the energetics and its effect on the alloying behaviour of Cd–Hg and Cd–Mg liquid alloys have been carried out with the aim of correlating their bulk and surface phenomena. Using the Quasi-chemical approximation for regular solution model, our results indicate that Cd–Hg and Cd–Mg are weakly heterocoordinated both in the bulk and on the surface. We observed that the degree of chemical order in Cd–Mg liquid alloy is more than that of Cd–Hg liquid alloy.     

The Study of Phase Equilibria in the Cs2SO4–Rb2SO4–H2SO4–H2O System

Crystallography Reports - The phase equilibria in the quaternary water–salt system Cs2SO4–Rb2SO4–H2SO4–H2O have been studied. The crystallization ranges are determined, and...     

Untersuchung der lokalisierten magnetischen Momente und der Nahordnung in Fe-Cr-Al- und Fe-Mn-Al-Legierungen mittels Neutronenstreuung

Short range order effects of two ferromagnetic alloy systems with low electrical conductivity (Fe–Cr–Al, Fe–Mn–Al) and the localized magnetic moments of Fe, Cr, and Mn have been investigated by magnetic diffuse neutron scattering. For Fe–Cr–Al the short range order parameters of the first three neighbour shells are given. The distribution of Al and Mn in the Fe-Mn-Al system has been qualitatively discussed. The cross section of the magnetic diffuse neutron scattering on systems with short range order was extended from binary to ternary alloys.     

Mesophase-Preceding Crystal Packing of 4,4'-Dialkyl-Substituted Salicylideneanilines; C10H21O–C6H3(OH)–CH=N–C6H4–С7Н13) Structure

Crystallography Reports - The crystal structure of 4,4'-substituted salicylideneaniline C10H21O–C6H3(OH)–CH=N–C6H4–C7H13 has been investigated by X-ray diffraction. A...     

Corrosion of electrocast AZS refractories by CAS glass–ceramics melting

Extensive corrosion experiments on electrocast alumina–zirconia–silica (AZS) refractories by molten CaO–Al₂O₃–SiO₂ (CAS) and Na₂O–CaO–SiO₂ (NCS) glasses were carried out at various temperatures under static condition. The features and mechanism of the corrosion were compared and analyzed. The changes of microstructure and phase composition of refractories in the course of the melt corrosion were also studied. X-ray diffraction (XRD), scanning electron microscope (SEM) and chemical analysis were used to characterize the corroded refractory materials and reacted melts. The reasons of alumina–zirconia–silica bricks corroded are the meltdown of their own composition, penetration or permeation of alkali oxide in the glass melt and scouring of the glass melt. The results show that the refractories resistance against corrosion of the oxides like Na₂O, K₂O or CaO is weak, and that the corrosion mechanism of NCS/AZS is different from that of CAS/AZS. In a static condition, CaO–Al₂O₃–SiO₂ melts corroded alumina–zirconia–silica brick more severely than Na₂O–CaO–SiO₂. The result provides useful reference to a prospective selection of refractory materials in glass and glass–ceramics manufacture.