Pulse Echo Overlap Research Articles

The dynamic and static mechanical characteristics of Sn-7Zn-based solder alloy modified with microalloying of In, Fe and Co elements

Tensile creep experiments and pulse-echo overlap (PEO) method were utilized to analyze the impact of small additions of 2.5%wt In, Fe and Co (0.1%wt for each) on the creep resistance and elastic properties of a cast Sn-7Zn alloy. The In-modified alloy displays noticeably enhanced creep resistance and increased the fracture time (~ 2.7 times) due to precipitation strengthening and formation of γ-InSn4 particles. The In-modified alloy exhibits an as-solidified grain structure, which is finer than the Sn-7Zn alloy, and predicted to enhance deformation resistance by lattice self-diffusion creep. Nonetheless, the creep resistance of Sn-7Zn alloy deteriorates after Fe and Co addition, highlighting the excellent coarsening of the new γ-Zn21Co5, γ-Co2Sn2Zn, and α-Fe0.92Sn0.08 precipitates. The obtained results implied that the creep strain rate follows the Garofalo hyperbolic sine equation, and the computed creep stress exponent is consistent with a climb-controlled dislocation creep. Consequently, for all PEO tests, the values of resulting Young's modulus (E) (66.7 GPa) and shear modulus (G) (20.5 GPa) of In-modified Sn-7Zn alloy were superior to those of the conventional plain Sn-7Zn alloy and Fe and Co modified alloy in its cast condition.

Thermophysical Properties of 1-Butanol at High Pressures

1-Butanol can be considered as a good fuel additive, which can be used at high pressures. Therefore, the knowledge of high-pressure thermophysical properties is crucial for this application. In this paper, new experimental data on the speed of sound in 1-butanol in the temperature range from 293 to 318 K and at pressures up to 101 MPa are reported. The speed of sound at a frequency of 2 MHz was measured at atmospheric and high pressures using two measuring sets operating on the principle of the pulse–echo–overlap method. The measurement uncertainties were estimated to be better than ±0.5 m·s−1 and ± 1 m·s−1 at atmospheric and high pressures, respectively. Additionally, the density was measured under atmospheric pressure in the temperature range from 293 to 318 K using a vibrating tube densimeter Anton Paar DMA 5000. Using the experimental results, the density and isobaric and isochoric heat capacities, isentropic and isothermal compressibilities, isobaric thermal expansion, and internal pressure were calculated at temperatures from 293 to 318 K and at pressures up to 100 MPa.

Effect of sulfur on sound velocity of liquid iron under Martian core conditions

Sulfur has been considered to be a predominant light element in the Martian core, and thus the sound velocity of Fe-S alloys at relevant high pressure and temperature is of great importance to interpret its seismological data. Here we measured the compressional sound velocity (VP) of liquid Fe, Fe80S20 and Fe57S43 using ultrasonic pulse-echo overlap method combined with a Kawai-type multi-anvil apparatus up to 20 GPa, likely corresponding to the condition at the uppermost core of Mars. The results demonstrate that the VP of liquid iron is least sensitive to its sulfur concentration in the Mars’ whole core pressure range. The comparison of seismic wave speeds of Fe-S liquids with future observations will therefore tell whether the Martian core is molten and contains impurity elements other than sulfur.

Influence of permanent magnet stirring on dendrite morphological and elastic properties of a novel Sn–Ag–Cu–Sb–Al solder alloy by ultrasonic pulse echo method

Preventing columnar β-Sn grains forming during manufacture have undoubtedly become major challenges. Columnar grains are commonly considered as unfavorable as their existence can relocate defects of solidification and deterioration in mechanical properties; however, the practical application of permanent magnetic stirring (PMS) during manufacture assuredly makes columnar grains easy to avert. In this published work, we studied the influence of PMS application on the solidification microstructures (growth morphology), elastic properties using pulse echo overlap (PEO) method, electrical resistivity and tensile properties of SAC(0505)–Sb–Al solder alloy. The direct result shows that the equiaxed β-Sn grains produced with applying PMS instead of higher aspect ratio columnar β-Sn grains was expected due to the induced Lorentz force. Hence, both the elastic modulus and hardness are typically decreased as the ratio of Poisson increased with applying PMS. In addition, the Pugh ratio has elucidated the ductility behavioral of the alloy sample. The tensile testing results exhibited possible enhancement in ductility by PMS, which could tremendously increase the elastic compliance of bulk solders. The electrical resistivity displays increase in the ionic contribution with PMS. These remarkable results offer innovative methods for predicting the final microstructure to properly control dendritic growth in metallic alloys.

Investigation of structural and ultrasonic properties of ternary borate glass specimen

New ternary calcium borate glass systems of composition 60B2O3-(40-x) CaO-xCuO, (where x = 5, 10, 15 & 20) were successfully prepared by melt quenching technique and characterized by XRD, SEM and ultrasonic measurements. The non-existence of Bragg peaks in the XRD patterns identifies the amorphous nature of the samples. SEM is carried out to study the morphological modification created by the modifier oxide. The ultrasonic velocities and Density are measured at room temperature using pulse echo overlap method and Archimedes’ principle using deionized water as immersion liquid respectively. The elastic moduli such as longitudinal, shear, bulk and Young’s moduli, Poisson’s ratio, acoustic impedance, micro hardness and Debye temperature are calculated using the measured data. These parameters are discussed due to variations in composition as well as modifying action of CuO. In this glasses, CuO plays a network former role.

Investigation of mechanical and radiation shielding features of heavy metal oxide based phosphate glasses for gamma radiation attenuation applications

In this study, xPbO2 − [(100 − x)(0.5Na2O − 0.5P2O5)] glass samples where x = 0, 5, 10, 15, 20 and 30 mol%, were prepared and their radiation shielding and mechanical properties were investigated. A 3 × 3 inch NaI (Tl) scintillation detector has been used to detect the emitted gamma-ray. The obtained results revealed the increase of both PbO2 content and the photon energy from 0.356 to 1.33 MeV increase the mass attenuation coefficient (MAC), the effective atomic number (EAN), and the radiation protection efficiency (RPE) and in the same time decrease the values of the half-value layer (HVL) and the mean free path (MFP). The G-P fitting method was used to calculate the exposure buildup factor in the photon energy range of 0.015–15 MeV along with the use of SRIM code, ESTAR database and the removal cross-sections to calculate the proton, alpha and electron mass stopping power of the prepared glasses. These parameters are affected mainly with Zn (n = 2 or 4). Moreover, the elastic properties of the glass samples have been calculated by measuring both longitudinal (VL) and shear (VS) velocities using the pulse-echo overlap technique at 5 MHz. The sample that had 30 PbO2 mol% had the highest elastic properties that gives confidence in the possibility of using these glasses for radiation shielding application.

Influence of native structural defects activated by illumination and under the memory effect conditions on ultrasonic wave propagation in TlInS2 ferroelectric–semiconductor with incommensurate phase

This paper presents data about experimental observation and theoretical validation effect of native defect states activated by illumination and under the memory effect conditions on the velocity of longitudinal and shear elastic waves propagating in layered TlInS2 ferroelectric-semiconductor in different directions. These longitudinal and transverse ultrasonic velocities were worked out by using the pulse echo overlap technique in the range of temperature ∼90–300 K and correspond to and elastic constants of TlInS2. The investigations reveal the illumination-induced spike-like peaks in the temperature dependence of longitudinal wave velocity centered at different temperatures in the range of temperature 225–300 K of high-temperature paraelectric phase. The temperature dependence of ultrasonic velocity of shear wave corresponding to mode exhibits a steep decrease in the slope under illumination at ∼190 K. Influence of the memory effects on the velocities of ultrasonic waves, which is associated with annealing times of about five hours inside the incommensurate (INC) phase, show similar features in the same temperature ranges: a similar well-defined spike-like anomalies in the temperature dependence of longitudinal ultrasonic wave velocity at and pronounced shear acoustic-mode softening below ∼190 K. The experimental results have been discussed in the frame of phenomenological the Landau phase transition theory. It has demonstrated that native deep level defects and crystal imperfections charged under light excitation and the memory effect condition and may essentially distort a crystal lattice of TlInS2 in the high-temperature paraelectric phase.

Impact of permanent magnet stirring on dendrite growth and elastic properties of Sn–Bi alloys revealed by pulse echo overlap method

Studying and understanding the dendritic growth process is a challenging topic related to liquid-solid phase transition, as it helps to predict the final microstructure controlling the solder properties. In a specific case of the design of Sn-Bi and Sn-Bi-Cu alloys, the solidification microstructures and corresponding electrical and elastic properties were studied with and without permanent magnetic stirring (PMS), as their influence on the growth morphology of dendrites is not yet fully assessed to date. We use pulse echo overlap (PEO) method for measuring the polycrystalline bulk modulus K, Young's modulus E, shear modulus G, Poisson ratio υ and hardness H. The PMS-driven flow caused a disruption of the columnar β-Sn dendrites and columnar-to-equiaxed transition (CET). Such behavior is believed to evolve from dendrite fragmentation, arises through complex hyper-branched morphologies at the origin of Lorentz force and Seebeck effect that acting on the melt. Both the hardness and elastic modulus are increased as the Poisson's ratio decreased. Moreover, the Pugh ratio clarified the ductility behavior of the alloy samples, while Poisson's ratio and electrical resistivity display slight decrease in the ionic contribution with applying PMS and/or Cu content. These results open new ways to predict the final microstructure controlling the dendritic growth in metallic alloys.

Characterization of semiconducting mixed electronic-ionic TeO2[sbnd]V2O5[sbnd]Ag2O glasses by employing ultrasonic measurements and Vicker's microhardness

In this paper, silver tellurovanadate 40TeO2-(60-x)V2O5-xAg2O, 0 ≤ x ≤ 50 mol%, glasses (abbreviated as TVAgx) are prepared by melt-quenching to study the correlation between structural and acoustical properties of TVAgx resulting from the substitution of V2O5 by Ag2O. Elastic aspects of these glasses are investigated by measuring the longitudinal (UL) and shear (US) wave velocities using the pulse-echo overlap technique at a frequency of 5 MHz at room temperature. Ultrasonic velocities showed non-linear trends: increasing behavior for 0 ≤ x ≤ 20 mol% and decreasing trend for 20 < x ≤ 50 mol%. The structural elucidation was achieved by studying the ultrasonic wave velocities and material density at room temperature. Longitudinal modulus L, shear modulus G, Young's modulus E, bulk modulus K, Poisson's ratio σ as well as other physical properties such as Debye temperature ϴD have been determined and discussed up on the number of bonds per unit volume nb, oxygen ion packing density OPD and mean atomic volume V¯. All mentioned quantities are obtained as functions of Ag2O content, in which they show a behavior change at x = 20 mol% in excellent coincidence with the previously reported results of thermal stability (ΔT), optical band gap (Eg), and oxygen molar volume (VO*). The findings indicate the important role of non-bridging oxygens NBOs. The room temperature ultrasonic wave velocities, glass transition temperature and other mentioned quantities show a critical content of silver oxide as x = 20 mol%, indicating that the addition of a silver oxide modifier changes the compactness, rigidity and content of non-bridging oxygens (NBOs). Compositional dependence of all elastic and other mentioned properties, imply to two composition regions as: relatively strength structure for 0 ≤ x ≤ 20 and loose packing structure for 20 < x ≤ 50, which is attributed to the increase of NBOs in the second region. It is also inferred that the glass with x = 20 is more stable, in agreement with the data of calorimetric analysis. Moreover, the glass transition temperature Tg, crystallization temperature Tcr and thermal stability show a behavior change at x = 20, indicating that this glass as possess the highest thermal stability. Therefore, glass with x = 20 mol% of Ag2O has the a more rigid structure, the highest thermal stability, the highest elastic moduli, a narrower band gap, the highest OPD, and a lower VO*, which makes it an excellent and promising sample in optothermal and acousto-optic applications. Vickers microhardness of the samples vary with composition, indicating the highest value for the case of x = 20. The hardness testing results comply with those of acoustical, optical, thermal and structural tests. Also, the scanning electron microscopy (SEM) confirms the amorphous structure of the studied glasses and gives more light on their morphological aspects and their microhardness.

Detection of anomalies in NLO sulphamic acid single crystals by ultrasonic and thermal studies

The ultrasonic pulse echo overlap technique (PEO) has been used to measure the velocities of 10 MHz acoustic waves in sulphamic acid single crystals in the range of 300–400 K. This study evaluated all the elastic stiffness constants, compliance constants and Poisson’s ratios of the crystal. The temperature variations of the elastic constants have been determined. The phase transition studies above room temperature were investigated using ultrasonic PEO technique. This study has suggested new weak elastic anomalies for the crystal around 330 K. The transverse elastic constants C 44 and C 66 have shown clear thermal hysteresis of 2 K. The present differential scanning calorimetric (DSC) studies carried out at a slow heating rate have also suggested weak phase transition around 331 K. The present elastic and thermal studies have been substantiated by already reported DC electrical conductivity studies around 330 K.

Towards a consensus on the pressure and composition dependence of sound velocity in the liquid Fe–S system

Recent advances in techniques for high-pressure and high-temperature experiments enable us to measure the velocity of sound in liquid Fe alloys. However, reported velocities in liquid Fe–S differ among research groups (e.g., by >10% at 5GPa), even when similar methods are used (i.e., the ultrasonic pulse–echo overlap method combined with a large volume press). To identify the causes of the discrepancies, we reanalyzed previous data and conducted additional sound velocity measurements for liquid Fe–S at 2–7GPa, and evaluated the potential error sources. We found that the discrepancy cannot be explained by errors in the sound velocity measurements themselves, but by inaccuracies in determining the temperature, pressure, and chemical composition in each experiment. Of particular note are the significant errors introduced when determining pressures from the unit-cell volume of MgO, which is a temperature-sensitive pressure standard, using inaccurate temperatures. To solve the problem, we additionally used h-BN as a pressure standard, which is less sensitive to temperature. The pressure dependence of the sound velocity became smaller than that of the original data because of the revised pressure values. Our best estimate for the seismic velocity of the Moon’s liquid outer core is 4.0±0.1km/s, given a chemical composition Fe83S17.

Optical, elastic properties and DTA of TNZP host tellurite glasses doped with Er3+ ions

Novel quaternary tellurite glasses within the composition 75TeO2–10Nb2O5–10ZnO–5PbO (TNZP) doped with the following Er3+ concentrations: 2500, 3750, 5000, 6250, 7500 and 8750 ppm have been prepared by using conventional melt quenching method. The thermal parameters, such as the glass transition temperature (Tg), crystallization temperature (Tc) and thermal stability (ΔТ) were determined. It is described that this system shows a stable glass formation, high thermal stability and low tendency crystallization. The linear refractive index, n, the optical energy gap, Eg, the nonlinear refractive index, n2, two photon absorption TPA, third order susceptibility, χ(3), of prepared glasses have been determined. Moreover elastic properties like longitudinal (λ), shear (μ), Bulk (β) and Young's (Y) moduli, Poisson's ratio, Debye temperature, and the microhardness of the glasses were evaluated by measuring both longitudinal and shear velocities using the pulse-echo overlap technique at 5 MHz. The present glasses is a promising candidate for optical application.

Measurement of Ultrasonic Velocity and Attenuation Coefficient on Cell Density and Disruption of Aspergillus Niger

The present study envisaged the measurement of ultrasonic velocity and attenuation coefficient on cell density of A.niger by using novel Pulse Echo Overlap (PEO) technique. The author reported parameters like acoustic impedance, adiabatic compressibility and free length were computed by applying Jacobson’s Free Length Theory (FLT). The cell density was carried out by using hemocytometer. The ultrasound transducer of 10 mm gap between transmitting and reflecting surfaces was immersed into the sonication vessels which were filled with varied cell density of 101 to 108 per ml to measure ultrasonic parameters for 2 and 10 MHz ultrasound. The sonication vessel kept inside the water bath to maintain constant environmental temperature of 303K by using automatic temperature controlled bath. In addition, the cell disruptions were carried out at 2 and 10 MHz high power ultrasound of output power of 600 watts by using ultrasonic processor. The ultrasonic velocity and attenuation coefficient were measured simultaneously with disruption of cell density as a function of sonication time. The uncertainty in measuring of ultrasonic velocity (v) is ± 0.02% and the attenuation coefficient (α) is ± 0.0015%. It was observed that both ultrasonic velocity and attenuation coefficient linearly increased with increasing concentration of cells. It was reported that the increased ultrasonic velocity was due to decreased adiabatic compressibility and free length with increased cell density. It was investigated that the attenuation coefficient was high at 10 MHz than 2 MHz high absorption losses occurred at 10 MHz. It was concluded that ultrasound waves propagated through culture of A.nigerdisturb the equilibrium between cells presented in the suspension and this retarded equilibrium shifts between the number of cells and their sizes and shapes, in turn, the ultrasound velocity and absorption.

Determination of elastic constants of epoxy resin/biochar composites by ultrasonic pulse echo overlap method

This study is carried out in order to determine the elastic properties of Epoxy Resin (ER) Composites reinforced with various mixtures of China Poplar Char (CPC) and Pine Cone Char (PCC) as biochars by ultrasonic wave velocity measurement method. The prepared chars are mixed with epoxy resin matrix at weight percentages of 10%, 20%, and 30% for preparing the ER/Biochars (BC) composites. The effect of biochar amounts on the elastic properties of the ER/BC composites are investigated by ultrasonic pulse echo overlap method. The morphologies of the samples are investigated by scanning electron microscopy. Based on the findings obtained from the present study, forming of the ER/CPC composites gives better values of elastic properties compared to forming of the ER/PCC composites. According to the obtained results, the composition ratio of 70:30 is the most appropriate composition ratio for both of the ER/CPC and the ER/PCC composites. POLYM. COMPOS., 37:2907–2915, 2016. © 2015 Society of Plastics Engineers

Equation of state of hercynite, FeAl2O4, and high-pressure systematics of Mg-Fe-Cr-Al spinels

AbstractIn this work a single crystal of synthetic hercynite, FeAl2O4, was investigated by X-ray diffraction up to 7.5 GPa and at room temperature, in order to determine its pressure–volume equation of state. The unit-cell volume decreases non-linearly with a reduction of 3.4% (i.e. 18.43 Å3). The pressure–volume data were fitted to a third-order Birch-Murnaghan equation of state providing the following coefficients:V0= 542.58(3)Å3,KT0= 193.9(1.7) GPa,K' = 6.0(5). These results are consistent with previous investigations of Cr and Al spinels measured with the same experimental approach but theKT0differs significantly from the experimental determination carried out more than 40 years ago by Wang and Simmons (1972) by the pulse echo overlap method. Our new results were used to redetermine the FeAl2O4(hercynite)= FeO(wüstite)+ Al2O3(corundum)equilibrium inP–Tspace and obtain geobarometric information for Cr-Al spinels found as inclusions in diamond.

Ultrasonic Investigation of Elastic Anomalies in Lithium Sodium Sulphate Hexahydrate Single Crystal

An extensive study of the thermal properties of Lithium Sodium Sulphate Hexa hydrate (LSSW) single crystal, with Trigonal structure, has been carried out using ultrasonic Pulse Echo Overlap (PEO) technique, Differential Thermal Analysis (DTA) and Thermo Gravimetric Analysis (TGA). The temperature variation of elastic constants of LiNa3(SO4)2·6H2O single crystal have been reported for the first time. The second order elastic stiffness constants C11, C33, C44, along the various directions in the crystal have been determined in the temperature range 300 - 330 K. The change in velocity with temperature with respect to the room temperature value has been measured using PEO technique. Significant anomalies were observed in C11 and C33 at 316 K. The elastic constant C12 has shown no variation in the temperature range 300 - 319 K. A minor deviation for C44 at 305 K following a parabolic change has been observed. The minor anomalies observed in the elastic constants of LSSW may be due to its dehydration of water of crystallization in the range 304 - 319 K. DTA studies showed an appreciable endothermic change in the range 309 K-369.79 K. TGA curve exhibited a decrease in weight of 1.687 mg in the temperature range 304 K-360 K. The minor anomalies observed in the elastic constants of LSSW may be due to loosing of its water of crystallization in the range 309 - 319 K. On loosing water there will not be any change in chemical structure but there will be physical change associated with loosing of water molecule.

Measurement of Elastic Parameters of Lithium Hydroxylammonium Sulphate Single Crystal, by Ultrasonic Pulse Echo Overlap Technique

Ultrasonics is the most established and precise technique to determine the elastic parameters of materials. Elastic constants are important parameters of a crystal which provide valuable infor-mation about the bonding characteristic between adjacent atomic planes and the anisotropic cha-racter of the bonding and structural ability. Second order elastic constants can be measured by measuring the velocity of the ultrasonic pulses of different polarization along different symmetry directions. Elastic Constants of Lithium Hydroxylammonium Sulphate [LHAS] single crystal by ul-trasonic Pulse Echo Overlap [PEO] technique are reported for the first time. Large single crystals of LHAS of size [26×26×10] mm3 have been grown from supersaturated aqueous solution of the salt by slow evaporation technique over a period of 40 - 45 days at 305 K. Absolute velocities at room temperature (303 K) have been measured for the selected direction and modes with McSkimin criterion. The anisotropy in the elastic properties of LHAS is well studied by measuring ultrasonic velocity in the crystal in certain specified crystallographic directions. The elastic stiffness constants C11, C33, C44, C55, and C66, and Acoustic impedance constants and Rao’s constants in specified directions are evaluated.

다중 반사파 중첩 자료의 상호상관을 이용한 엔지니어링 플라스틱 코어의 초음파속도 측정

여러 가지 초음파 속도 측정법 중 비교적 정확하고 다양한 목적에 활용될 수 있다고 알려진 반사파 중첩법(pulseecho-overlap method)에 의해 초음파의 전파시간을 자동으로 측정할 수 있는 시스템을 구축하고, 엔지니어링 플라스틱 시험편에 대한 초음파 속도를 초동발췌법(first arrival picking method)과 비교하였다. 다섯 가지 종류의 엔지니어링 플라스틱 코어에 대해 반사파 중첩법과 초동발췌법에 의해 초음파 속도를 측정한 결과, 반사파 중첩법은 초동발췌법보다 최소 4배로 긴 다중반사파 자료가 필요하므로 매질의 감쇠특성에 의해 측정가능한 시험편의 길이에 제약이 있다. 또한 측정되는 속도는 초동발췌법에 의한 속도보다 낮게 측정되는 경향을 보였으며, 수신된 파형을 분석한 결과, 이는 전파거리가 길어짐에 따른 매질의 감쇠 및 분산특성에 의한 영향으로 해석되었다. 상호상관을 이용하여 제1반사파가 제2반사파 및 제3반사파와 가장 잘 중첩되는 시간을 실시간으로 자동으로 발췌하도록 프로그램하여 실험자에 의한 측정 편차가 개입될 가능성을 배제함으로써 반복성과 재현성을 높였다. 또한, 실험의 조건이 변하지 않는 경우는 중합수를 늘림으로서 무작위 잡음에 의한 측정오차를 줄일 수 있으며, 실험 조건이 변하는 경우는 속도변화 모니터링에도 활용이 가능하다. An automated ultrasonic velocity measurement system adopting pulse-echo-overlap (PEO) method has been constructed, which is known to be a precise and versatile method. It has been applied to velocity measurements for 5 kinds of engineering plastic cores and compared to first arrival picking (FAP) method. Because it needs multiple reflected waves and waves travel at least 4 times longer than FAP, PEO has basic restriction on sample length measurable. Velocities measured by PEO showed slightly lower than that by FAP, which comes from damping and diffusive characteristics of the samples as the wave travels longer distance in PEO. PEO, however, can measure velocities automatically by cross-correlating the first echo to the second or third echo, so that it can exclude the operator-oriented errors. Once measurable, PEO shows essentially higher repeatability and reproducibility than FAP. PEO system can diminish random noises by stacking multiple measurements. If it changes the experimental conditions such as temperature, saturation and so forth, the automated PEO system in this study can be applied to monitoring the velocity changes with respect to the parameter changes.

Elastic and structural changes of xNa2O–(35 − x)V2O5–65TeO2 glass system with increasing sodium

Sodium vanadotellurite glass system with composition xNa2O–(35 − x)V2O5–65TeO2; (x = 5–25 mol%) was prepared by melt-quenching method. Elastic moduli and structural changes were studied by measuring ultrasonic shear and longitudinal velocities using the pulse-echo–overlap technique and Raman spectroscopy, respectively. Both shear and longitudinal velocities showed small steady decrease with addition of Na2O from x = 5 mol% to x = 15 mol% followed by large decrease at x > 15 mol%. Longitudinal modulus (CL), shear modulus (μ), Young's modulus (Y), Hardness (H) and Debye Temperature (θD) also showed similar behaviour to the ultrasonic velocities. The decrease in elastic moduli is suggested to be due to weakening of network rigidity of the glass system with increase in formation of non-bridging oxygen, NBO as revealed by Raman spectroscopy. Additional analysis using bulk compression and ring deformation models showed that ratio between theoretical bulk modulus, Kbc and experimental bulk modulus, Ke was around 2.1 for x = 5–20 mol% before an increase to around 2.4 for x > 20 mol% indicating that the main compression mechanism is ideal isotropic compression.

Enhancement of elastic properties by WO3 partial replacement of TeO2 in ternary (80 − x)TeO2–20PbO–xWO3 glass system

Tellurite–tungsten (80−x)TeO2–20PbO–xWO3 (x=0–20mol%) glass with concurrent reduction of TeO2 and addition of WO3 was prepared by the melt-quenching method. Elastic and structural properties of the glasses were investigated by measuring both longitudinal and shear velocities using the pulse-echo overlap method at 5MHz and Fourier Transform Infrared (FTIR) spectroscopy, respectively. Both longitudinal modulus (L) and shear modulus (G) showed a slight decrease at x=5mol% followed by a large and almost linear increase for x>5mol%. Interestingly, bulk modulus (K), Young's modulus (E) and hardness (H) recorded almost similar trends where the values showed large increase for x>5mol%. At x=20mol% the elastic moduli increased by more than 30% compared to binary 80TeO2–20PbO glass. FTIR analysis showed an increase in intensity of TeO4 assigned peaks concurrent with the decrease in intensity of TeO3 assigned peaks for x>5mol% which indicates an increase in number of bridging oxygen (NBO) and a decrease in non-bridging oxygen (BO), respectively. The enhancement of L, G and other related moduli for x>5mol% is suggested to be due to the increase in BO which caused the increase in rigidity and stiffness of the glass network. Quantitative analysis based on bulk compression and ring deformation models showed kbc/ke ratio monotonously decreased from 2.69 (x=5mol%) to 2.09 (x=20mol%) which infers that the glass system became a relatively more open 3D network for x>5mol% WO3 addition.