Internal friction of alkaline-earth-iron-metaphosphate glasses

The internal frictions of Mg, Ca, Ba iron-metaphosphate glasses were studied from 120 to 700 K using the low-frequency torsion pendulum technique. The internal friction as a function of temperature revealed two distinct peaks. The low-temperature peak was absent in glass without iron oxide. Its activation energy compared favourably with that for dielectric loss and dc conductivity in similar glasses. This suggests the same mechanism for all three processes, probably connected with electron transfer between iron ions of different valence.     

Internal friction of sodium phosphate glasses

The internal friction of XNa₂O·(1 ? X)P₂O₅ glasses, X varied from 0.29 to 0.59, has been measured from ?100 to +300°C at ～ Hz and from 25 to 300°C at ～ 2000 Hz. Two internal friction peaks were observed. Based on the compositional dependence of the low temperature peak and the agreement between the activation energy of this peak with that calculated from dielectric loss measurements, this peak was assigned to the stress induced movement of the sodium ions. The magnitude of the second peak occurring at higher temperature, in addition to varying with the sodium content, was also very sensitive to the water content; its magnitude increasing with increasing water content. This peak was concluded to be a type of ‘mixed alkali’ peak involving the cooperative movement of sodium ions and protons. Due to the shift of the background damping to lower temperatures with decreasing sodium content, neither peak could be observed for X < 0.30.     

Internal friction and dynamic modulus of metaphosphate glass

Internal friction and dynamic modulus were measured by a forced torsional vibration method at 0.5-5 Hz in the range of −120 to 300 °C for four kinds of metaphosphate glasses, 50MgO · 50P₂O₅(MgP), 48SrO · 52 P₂O₅(SrP), 25MgO · 25SrO · 50P₂O₅(MgSrP) and 25Na₂O · 25MgO · 50P₂O₅(NaMgP). Three internal friction peaks appeared for MgP at ∼−30, ∼105 and ∼230 °C, and the activation energies of the relaxation behavior obtained from the low, intermediate and high temperature regions were ∼110, ∼250 and ∼580 kJ/mol, respectively. For SrP, those three peaks were also obtained at ∼−45, ∼60 and ∼195 °C, and the activation energies were estimated as ∼95, ∼200 and ∼600 kJ/mol at each temperature, respectively. Two peaks appeared at ∼−50 and ∼160 °C for MgSrP, and ∼−55 and ∼70 °C for NaMgP, respectively. The obtained activation energies were ∼100 and ∼180 kJ/mol for MgSrP, and ∼75 and ∼200 kJ/mol for NaMgP, respectively. It is assumed that the primary peaks (the low temperature region) were influenced by the behavior of Mg²⁺, Sr²⁺ and Na¹⁺ ions, and the secondary peaks (the intermediate temperature region) were based on non-bridging oxygen associated with Mg²⁺, Sr²⁺ and Na¹⁺ ions. Dynamic modulus showed a decreased gradually with increasing temperature in the present temperature range for all the compositions.     

Internal friction in phosphoaluminate and borate glasses

Internal friction in sodium phosphoaluminate and borate glasses was investigated by torsion pendulum, beam vibration and pulse-echo methods. The Arrhenian relationship was verified in a frequency interval covering eight decades. A detailed analysis of the first peak was made to obtain the distribution of relaxation times and the distribution of activation entropy ΔS and activation enthalpy ΔH. The log-normal distributions were further compared to the Doremus theory and the observed discrepancy discussed.     

Internal friction in three component metaphosphate glasses

The internal friction of three component metaphosphate glasses in the quasi-binary system MO·P₂O₅-M′O·P₂O₅ was measured as a function of temperature by a free torsional vibration method. The high-temperature peak of these glasses which include the various combinations of the modifying ions M and M′ where M or M′Ca, Sr and Ba appeared unanimously at ≈160°C. The peak height seemed to be dominated by a modifying ion of larger radius. The ionic radius is in the order Ba²⁺ > Sr²⁺ > Ca²⁺. For the glasses containing the modifying ions, M  Ca, Sr, Ba and M′  Mg, Zn, the internal friction appeared to be governed strongly by the ions which have a lower coordination number and a larger ionic radius. The MgO·P₂O₅ZnO·P₂O₅ glass exhibited a completely different behavior compared with the parent glasses MgO·P₂O₅ and ZnO·P₂O₅.     

Internal friction and dielectric losses of mixed alkali borate glasses

The internal friction and dielectric losses of NaK, LiNa, LiCs, LiK, NaCs, KCs, AgLi, AgNa, AgK and AgCs borate glasses were measured as functions of the temperature at various frequencies. In general, the behavior of mixed alkali borate glasses is very similar to the behavior of the comparable phosphate and silicate glasses. The magnitude of the mixed alkali peak was found to vary systematically with the size of the involved alkali ions. The silver-containing glasses also show the mixed alkali effect. The borate glasses are briefly compared with the silicate and the phosphate glasses and their behavior is found to be in agreement with the recent proposal that the mixed alkali peak is caused by an electro-mechanical cross effect.     

Internal friction of NaPO3 glasses containing water

The internal friction of sodium metaphosphate glasses containing from 0.016 to 0.330 wt% water has been investigated. Weight loss and infrared absorption measurements were used to determine the water content. Of the two internal friction peaks observed between ?100°C and ～250°C, the second peak occurring above room temperature has a pronounced dependence upon the water content; increasing water content causing the activation energy to decrease as the peak increased in size. A mechanism consisting of the cooperative motion of sodium ions and protons has been proposed for this peak. It is concluded that the second peak in the NaPO₃ glasses and the similar peak in alkali silicate glasses is not associated with the movement of the non-bridging oxygen ions.     

Internal friction of mixed alkali metaphosphate glasses: (II). Discussion

The internal friction and dielectric losses of mixed LiNa, LiK, LiCs, LiAg, NaK, NaCs and NaAg metaphosphate glasses are interpreted on the basis of explanation proposed for the mixed alkali effect. It was found that the magnitude of the mixed peak correlates better with size differences than with mass differences. The intermediate temperature peak is treated as a mixed proton-alkali peak. The large mechanical loss peak, appearing when the alkalis are mixed, was attributed to a coupled movement of dissimilar alkali ions and an explanation of the nature of this coupling is proposed. From this model it is predicted that mixed peaks can occur in any electrically insulating material containing dissimilar charge carriers.     

Internal friction of mixed alkali metaphosphate glasses: (I). Results

The internal friction of LiNa, LiK, LiCs, LiAg, NaCs and NaAg metaphosphate glasses was measured at 0.5 Hz and 2 kHz. The dielectric losses were also measured from 40 to 160°C, at frequencies of 300, 3 000 and 30 000 Hz. The densities of the glasses were determined and the molar volume of oxygen was calculated. In general, the mixed alkali behaviour of metaphosphate glasses is very similar to the mixed alkali behaviour of silicate glasses. Silver behaves in this respect like an alkali ion with approximately the same size as a sodium ion.     

Internal friction in vanadium-phosphate glasses doped with Na2O

The internal friction of _xNa₂O·(0.5−x)V₂O₅·O.5P₂O₅(x = 0.025–0.3) glasses was studied using the low-frequency torsion pendulum technique. The temperature spectrum of internal friction reveals three maxima. Maximum 1, the so-called “electron” maximum, is the same as observed in binary vanadium-phosphate glasses. The origin of maximum 2 can be attributed to ion migration. Maximum 3 appears for glasses containing more than 10 mol.% Na₂O and is probably connected with sodium-proton interactions.     

Internal friction data as explained on the basis of structural-energetic parameters of inorganic glasses

On the basis of a previously reported model the diffusive mechanism of internal friction in microheterogeneous inorganic glasses is discussed. A method of calculating the activation energy, the dimensions of the structure complexes and defects, as well as the masses of relaxing structure elements is proposed. The potentialities of the method for a series of binary and ternary alkali-silicate glasses are shown.     

Dissoluble and degradable CaLi-based metallic glasses

We study the degradable and dissoluble features of a Ca-Li-Mg-Zn bulk metallic glass in pure water at room temperature. A remarkable degradable feature of the metallic glasses is that the degradation is controllable by changing the composition and components. The degradable metallic glasses with superior combined properties of polymer-like thermal plasticity at low temperature (40-70 °C), the ultralow elastic moduli comparable to that of human bones, and ultralow density (< 2 g/cm³) in known metallic glasses to date, and good machinability at a lower temperature in the supercooled liquid region could have potential applications. The metallic glasses also provide a model system to study the corrosion behavior in glasses.     

Tantalum based bulk metallic glasses

Ta-based bulk metallic glasses with high strength (2.7 GPa) and hardness (9.7 GPa), high elastic modulus (170 GPa) and high density (12.98 g/mm³) were developed. The best glass forming ability so far for a Ta-Ni-Co system reaches a critical diameter of 2 mm by the copper mold casting method. It shows an exceptionally high glass transition temperature of 983 K and a high crystallization temperature up to 1023 K. The unique mechanical and physical properties make them a promising high strength material.     

Dynamic mechanical properties of metallic glasses

Dynamic mechanical properties of two metallic glasses, Fe₄₀Ni₄₀P₁₄B₆ and Fe₃₂Ni₃₆Cr₁₄P₁₂B₆, have been studied at frequencies ranging from 0.1 to 3 kHz and at temperatures between ? 160 and 390°C. Each of the samples exhibits an internal friction maximum at about ?20°C with activation energies of 25 and 34 kcal/mol. A possible mechanism for the low-temperature internal friction peak is suggested.     

Stability of Ni-based bulk metallic glasses

Several ternary (Ni_xNb_ySn_z) refractory alloy glasses (RAGs) were studied at elevated temperatures in order to assess the stability of the amorphous state, i.e. devitrification, and to identify subsequent phase transformations in these materials. differential scanning calorimetry (DSC) experiments indicated a complex phase transformation sequence with several distinct crystallization and melting events being recorded above the glass transition temperature, T_g. Below T_g the RAG samples were studied with an in situ environmental X-ray furnace facility, which allowed step-wise isothermal ramping experiments commencing at a temperature below the reduced temperature of T/T_g ≈ 0.80. Distinct crystalline phases were observed when T/T_g ≈ 0.84 for ternary RAG alloys, while similar experiments on Zr-based Vit 106 glass alloys did not reveal any apparent phase separation until T/T_g ≈ 0.96. The phase separation kinetics followed an Arrhenius type of relationship with Ni₃Sn, and Nb₂O₅ being the principle crystalline precipitates.     

High mixing entropy bulk metallic glasses

Bulk metallic glasses (BMGs) are usually based on a single principal element such as Zr, Cu, Mg and Fe. In this work, we report the formation of a series of high mixing entropy BMGs based on multiple major elements, which have unique characteristics of excellent glass-forming ability and mechanical properties compared with conventional BMGs. The high mixing entropy BMGs based on multiple major elements might be of significance in scientific studies, potential applications, and providing a novel approach in search for new metallic glass-forming systems.     

Rare earth based bulk metallic glasses

Recently, the rare earth based bulk metallic glasses (REBMGs) have attracted increasing interest due to their unique properties and potential applications as functional glassy materials. These REBMGs display many fascinating properties such as heavy fermion behavior, thermoplastic properties near room temperature, excellent magnetocaloric effect, hard magnetism, and polyamorphism, all of which are of interest not only for basic research but also for metallurgy and technology. These characteristics and properties are ascribed to the unique electronic, magnetic and atomic structures of the REBMGs. In this review paper, the fabrication, glass-forming ability, polyamorphism, elastic, thermal, and physical properties are summarized and discussed. Owing to the unique electronic structure of rare earth elements, the electric and magnetic properties of the REBMGs are especially addressed. The works have implications for seeking novel metallic glasses with controllable properties and for understanding the nature of glass formation. The development of REBMGs as functional materials might promote and extend the commercial applications of metallic glasses.     

Elastic properties of some bulk metallic glasses

The relationships between the elastic moduli, glass forming ability and response to deformation of bulk metallic glasses are investigated. Five bulk metallic glasses are prepared from high purity elements via suction casting. The results confirm that there exists a correlation between energy absorbed to failure during compression testing and the bulk to shear modulus ratio. This finding is developed such that it corresponds only to the elastic component of energy absorption, and that the bulk modulus dominates this. Plastic deformation appears to be favored by a reduced shear modulus, although it shows greater dependence on structural features that are frozen in during the glass transition, and so may well be dependent on the liquid fragility.