Conventional Melting Technique Research Articles

A comparative study of microwave assisted and conventional melting techniques to glass properties

The present work focuses on the investigation of the properties of 33TeO2: 30B2O3: 30ZnO: 5BaO: 2Eu2O3 glass prepared using microwave and conventional techniques. The prepared glasses were characterized by TGA/DSC analysis, density, refractive index, FTIR, XPS, absorption spectra, photoluminescence, lifetime, quantum efficiency, and X-ray-induced luminescence properties. The photoluminescence of the samples exhibited the strongest luminescence intensity of the Eu3+ ion at 614 nm (7F2) under 394 nm excitation, resulting in a relatively high photoluminescence quantum yield of 39.64%. The luminescence decay time from the 5D0 to 7F2 level of glass prepared by the microwave technique is lower than that of a sample prepared by the conventional technique, with a luminescence decay time of 1.269 and 1.425 ms, respectively. X-ray-excited luminescence spectroscopy identified an emission peak at 614 nm in the samples, which can be attributed to 5D0-7F2 transitions in the Eu3+ ion. These high-intensity samples were compared with bismuth germanate oxide (BGO) crystals used in radiation detection applications. From the various results examined, it is clear that the 33TeO2: 30B2O3: 30ZnO: 5BaO: 2Eu2O3 glass prepared using the microwave technique is suitable for use as a scintillation material.

Synthesis and characterization of multi-walled carbon nanotube-reinforced Ti–Mg alloy prepared by mechanical alloying and microwave sintering

Titanium-magnesium (Ti–Mg) alloy is a widely accepted bimetallic material suitable for biomedical applications. However, reduced wear and corrosion resistance, low strength and hardness, and stress shielding effect limit their widespread applications. Reinforcing multi-walled carbon nanotubes (MWCNTs) possessing low density, high modulus, and improved mechanical properties overcome the shortcomings of Ti–Mg alloy. In the present work, nanostructured Ti–Mg alloy was synthesized at room temperature and simultaneously reinforced with MWCNTs. The high energetic ball milling process (HEBM) has been successfully utilized to mechanically alloy Ti with Mg at room temperature by decreasing the grain size to the nanoscale and reinforcing the alloy with MWCNTs. The synthesized nanostructured powder size was 25 nm. Characterization results have shown the emergence of new phases like Ti4C4 and Mg2C3 as a result of mechanical alloying (MA). The reinforced alloy powder was consolidated by cold compaction and followed by microwave sintering. The consolidated sample crystallite size attained was 72 nm and then characterized by Nanoindentation, XRD, and SEM. XRD results show intermetallic compounds Mg2C3 and TiC in bulk samples. SADP TEM confirmed the retention of Nano and partial amorphous structures in the consolidated samples. The nanoindentation test revealed the hardness and elastic modulus values 0.93 GPa and 28.12 GPa, respectively, equivalent to CpTi and its associated alloys. The results are prevalent in those alloys used in biomedical applications produced by conventional melting and casting techniques and can be a potential biomaterial.

An insight into the structure of nanocomposites in porous glasses and their interactions after contact with the environment

Porous sodium borosilicate (SBS) glasses were prepared by conventional charge melting technique and TGS nanocomposites were prepared by introducing TGS crystals from a saturated solution into a pores matrix. The aim of this paper is to clarify the structure and surface changes of the SBS porous glasses before and after introducing TGS crystals. Thermal and dielectric measurements revealed the presence of phase transitions in TGS nanocomposites and confirmed the influence of crystallite size on the phase transition temperature. Powder X-ray diffraction (PXRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) revealed the morphological changes of the sample surfaces upon immersion in a TGS saturated solution. Additionally, the atomic ratio of empty porous glasses and TGS-PG nanocomposites was obtained by the XPS analysis. The visible differences in surface properties between empty porous glasses and TGS nanocomposites have been observed and discussed.

Optical properties, FTIR, and electron spin resonance analysis on the impact of gamma irradiation on fluorophosphate glasses doped with Iron(III) oxide

In the present investigation, conventional melting techniques were employed to fabricate the fluorophosphate glass composites with a composition of 20NaF–60P2O5–20Na2O–3Fe2O3 (mol.%). An investigation was conducted to analyze the impact of various doses of gamma-ray irradiation on certain optical properties. The alteration in the localized defects caused by gamma irradiation can explain the reduction in the refractive index (n) as the doses of gamma-ray irradiation increase, up to 10 kGy. The results of the solar skin protection factor (SSPF) and solar material protection factor (SMPF) tests demonstrate that the un-irradiated composite offers the highest level of protection against the harmful effects of solar energy on both human skin and materials. Some optical parameters, such as the concentrations of the charge carrier (Nopt), the relaxation time (τ), the optical electronegativity (ηopt), and the optical mobility (μopt) showed gamma dose-dependent. The effects of gamma-ray irradiation on the composites were analyzed using Electron Spin Resonance (ESR) and Fourier Transform Infrared (FTIR) spectroscopic studies, both before and after exposure to 10 and 20 kGy.

The effect of Tb substitution for Ni on microstructure, martensitic transformation and cyclic stability of elastocaloric effect in Ni–Mn–Sn magnetic shape memory alloys

Cyclic stability of elastocaloric effect is the key factor that restricts the elastocaloric cooling application of Ni–Mn–Sn alloys fabricated by the conventional melting technique. Element doping is an effective way to enhance the performance of materials. In this work, the effect of Tb substitution for Ni on martensitic transformation (MT) temperature, microstructure, mechanical properties and cyclic stability of elastocaloric effect in the Ni43.5–xTbxMn45.5Sn11 (x = 0, 0.6, 1.2 and 1.8) magnetic shape memory alloys has been investigated. MT temperatures increase with increasing x from 0 to 1.2 and then decrease with further increasing x to 1.8. The substitution of Tb for Ni introduces γ phase (Tb-rich second phase in Tb-doping alloys). The volume fraction of γ phase increases with increasing Tb content and thus the mechanical properties and the cyclic stability of elastocaloric effect increase with the increase of Tb content. Among these alloys, Ni42.3Tb1.2Mn45.5Sn11 alloy shows a large adiabatic temperature change of 10.0 K induced by applying the uniaxial stress of 550 MPa. In addition, a constant temperature change of 6.5 K shows no apparent degradation under the compressive stress of 350 MPa during 1000 cycles for this alloy. The excellent elastocaloric properties make this alloy a promising candidate for the room-temperature elastocaloric cooling application. The underlying mechanism of the enhanced cyclability of elastocaloric effect and mechanical properties is also revealed.

A biodegradable 3D woven magnesium-based scaffold for orthopedic implants

Porous Magnesium (Mg) is a promising biodegradable scaffold for treating critical-size bone defects, and as an essential element for human metabolism, Mg has shown sufficient biocompatibility. Its elastic moduli and yield strengths are closer to those of cortical bone than common, inert metallic implants, effectively reducing stress concentrations around host tissue as well as stress shielding. More importantly, Mg can degrade and be absorbed in the human body in a safe and controlled manner, thereby reducing the need for second surgeries to remove implants. The development of porous Mg scaffolds via conventional selective laser melting techniques has been limited due to Mg’s low boiling point, high vapor pressures, high reactivity, and non-ideal microstructures in additively manufactured parts. Here we present an exciting alternative to conventional additive techniques: 3D weaving with Mg wires that have controlled chemistries and microstructures. The weaving process offers high throughput manufacturing as well as porous architectures that can be optimized for stiffness and porosity with topology optimization. Once woven, we dip-coat the weaves with polylactic acid to enhance their strength and corrosion resistance. Following fabrication, we characterize their mechanical properties, corrosion behavior, and cell compatibility in vitro, and we use an intramuscular implantation model to evaluate their in vivo corrosion behavior and tissue response.

Synthesis of Nb0.8Hf0.2FeSb0.98Sn0.02 and Hf0.25Zr0.25Ti0.5NiSn0.98Sb0.02 Half-Heusler Materials and Fabrication of Thermoelectric Generators

In this study, half-Heusler (HH) thermoelectric materials Nb0.8Hf0.2FeSb0.98Sn0.02 (p-type) and Hf0.25Zr0.25Ti0.5NiSn0.98Sb0.02 (n-type) were synthesized using induction melting and spark plasma sintering. For alloying, a conventional induction melting technique was employed rather than arc melting, for mass production compatibility, and the thermoelectric properties of the materials were analyzed. The maximum dimensionless figures of merit (zTmax) were 0.75 and 0.82 for the p- and n-type material at 650 oC and 600 oC, respectively. These materials were then used to fabricate generator modules, wherein two pairs of p- and nlegs without interfacial metal layers were brazed on direct bonded copper (DBC)/Al2O3 substrates using a Zrbased alloy. A maximum power of 0.57 W was obtained from the module by applying a temperature gradient of 476 oC, which corresponds to a maximum power density of 1.58 W cm -2 when normalized by the area of the material. The maximum electrical conversion efficiency of the module was 3.22% at 476 oC temperature gradient. This value was negatively affected by the non-negligible contact resistivity of the brazed interfaces, which ranged from 6.63 × 10 -9 Ωm2 to 7.54 × 10 -9 Ω m2 at hot-side temperatures of 190 oC and 517 oC, respectively. The low electrical resistivity of the HH materials makes it especially important to develop a brazing technique for ultralow resistance contacts.

ZnO-Bi2O3-B2O3 glasses doped with rare earth oxides: Synthesis, physical, structural characteristics, neutron and photon attenuation attitude

A group of newly zinc bismo-borate glasses doped with various rare earth (RE) oxides with composition 20ZnO-20Bi2O3-(60-xRE)B2O3: xRE= 0, 0.5La2O3, 0.5CeO2, 0.5Nd2O3, and 0.5Gd2O3 mol% named as GB, GL, GC, GN, and GG, respectively have been prepared via conventional melt technique. The influence of (RE) ions on the structural, physical characteristics, neutron, and gamma radiation competences glasses have been investigated. Glass density was increased progressively (4.1131–4.3157 g/cc) with the reduce in molar volume (36.77–35.38cc/mol) for GB-GG glasses. The oxygen packing density (OPD) was increased from 70.7 to 73.4 (g atm/l). Mass attenuation coefficient (MAC) was found that 71.657, 71.668, 71.744, 71.779, and 71.931 cm2/g for GB, GL, GC, GN, and GG. The half value layer (HVL) has the trend of (GG) HVL< (GN) HVL< (GC) HVL< (GL) HVL< (GB) HVL. Generally, the GG glass sample (doped with Gd2O3) was achieved the least HVL which assured that it has the best shielding ability among all prepared glasses.

Radiation shielding competencies for waste soda–lime–silicate glass reinforced with Ta2O5: experimental, computational, and simulation studies

In this study, the authors emphasized an incisive purpose as the valorization of waste soda–lime–silicate glass (SLS) for a potential gamma-rays shielding material. For this, xTa2O5-(100-x)SLS glass systems where x: 0, 0.005, 0.05, and 0.5 wt% were fabricated via conventional melting technique. The synthesized four glass specimens (RG and RGT1 to RGT3) were then subjected to physical, optical, and radiation shielding measurements. Simulation studies (MCNP-5) and theoretical computations (XCOM) were conducted to validate the findings. The results clearly showed that the insertion of Ta2O5 improved both physical and optical properties. In particular, RGT3, having a higher amount, possessed the highest glass density (ρglass) and refractive index (n) values. On the other hand, the transmission factor (TF) data revealed that increasing the thickness of the glass sample caused a notable decrease in the TF values. RG decreases from 92.233% to 78.461%, 61.562%, and 48.302% for thicknesses of 0.5 cm, 1.5 cm, 3 cm, and 4.5 cm. RGT3 shows the best radiation shielding potential out of the investigated waste SLS samples according to the several radiation shielding factors.

The effect of Nb2O5 on waste soda‐lime glass in gamma‐rays shielding applications

Transparent waste soda-lime glass (SLS) reinforced with Nb2O5 (0.005, 0.05, and 0.5 wt%) was successfully synthesized using a conventional melting technique for gamma-radiation attenuation applications. The synthesized glass series (RG, RGN1 to RGN3) were then subjected to some physical, optical, and radiation shielding measurements. The physical measurements and computations showed that the increasing content of Nb2O5 increased glass density (ρglass), molar volume (Vm), and oxygen molar volume (OMV), however, decreased oxygen-packing density (OPD). Moreover, several optical parameters, such as the refractive index (n), dielectric constant (ϵ), and metallization criterion (M), were evaluated. One can say that the optical and physical properties can be improved owing to the addition of Nb2O5 in waste SLS glass. The gamma-ray transmission method was utilized to measure the linear attenuation coefficient (LAC) for the fabricated RGN glass series for gamma-photon energies 0.662, 1.173, and 1.332 MeV emitted from 137Cs and 60Co, respectively. The accuracy of the obtained results was tested by comparing the experimental data with those simulated by MCNP-5 and those computed theoretically by XCOM. The obtained results showed agreement between the experimental measurements, simulated, and theoretical evaluations. We found that the photons with energy of 0.662 MeV have a lower penetration power. Thus, the LACs are higher at 0.662 MeV for all synthesized glass samples. The LAC values at 0.662 MeV were between 0.1849 and 0.2253 cm− 1 for the glass samples RG and RGN3. The LAC results depicted a significant relationship between the chemical composition and the synthesized glass series’ attenuation coefficients. The LAC’s measured values were enhanced with the insertion of the niobium pentoxide (Nb2O5) contents. The half-value layer (HVL, ∆0.5) was calculated for the synthesized glass series based on the measured LAC. The thinner ∆0.5 layers were achieved at 0.662 MeV and ranged between 3.077 and 3.748 cm for the glasses coded as RGN3 and RG, respectively, while the thicker ∆0.5 layers were found at 1.332 MeV and changed in the range of 4.306–4.914 cm. The influence of the Nb2O5 doping ratio was examined, and we found that the values of the ∆0.5 layers become thinner as the Nb2O5 doping ratio increases.

Spectroscopic investigations on 1.53 μm NIR emission of Er3+ doped multicomponent borosilicate glasses for telecommunication and lasing applications

The multicomponent borosilicate (MBSER) glasses activated with different concentrations of Er3+ ions (varies from 0.1 to 2 mol%) were prepared via conventional melting and rapid quench technique and studied their thermal, structural and spectroscopic characteristics by using DSC, XRD, FTIR, optical absorption, excitation and emission measurements. Judd- Ofelt analysis in correlation with the absorption and emission spectral profiles was performed for the evaluation of several radiative parameters of the as-prepared glasses. Visible and NIR luminescence were recorded at 379 nm excitation and a special consideration is given to 1536 nm emission corresponding to the 4I13/2 → 4I15/2 transition. McCumber theory (MC) is used to determine the stimulated emission cross-section from the calculated absorption cross-section and is found well matched with the emission cross-section obtained from Fuchtbauer-Ladenburg (FL) equation. Better radiative parameters (stimulated emission cross-section (σemi) = 15.78 × 10−21cm2, effective bandwidth (Δλeff) = 67 nm), laser (gain bandwidth (σ(λp) x Δλeff = 1.05 × 10−25 cm3), optical gain (σ(λp) x τR) = 42.5 × 10−25 cm2s)) and gain spectra characteristics suggests the MBSER glasses for optical amplifier and laser applications since they offer a broadened emission spectra in the NIR region.

X‐ray shielding parameters of lanthanum oxide added waste soda‐lime glass

Besides various materials, glass becomes very important, as it has started to be used in many applications. Thus, their radiation shielding properties should be determined for safely using in critical applications such as for medical purposes With this in mind, the present study investigated the radiation shielding parameters of waste soda‐lime (SLS) containing varying amounts of lanthanum oxide (La2O3). The La2O3 content was added as 0.005, 0.05 and 0.5 in wt% into waste SLS glass, and four different glass specimens (La‐0, La‐0.005, La‐0.05, and La‐0.5) were produced via conventional melting technique. The linear attenuation coefficient for glass samples was measured in the photon energies of 511,835 and 1,275 keV and the results were compared with the calculation done by XCOM. One can conclude that adding lanthanum oxide to waste glass is an effective way to improve radiation shielding properties of glass. That is, the sample of La‐0.5 could provide a higher linear attenuation coefficient while lower half‐value thicknesses. Further, the findings obtained both in calculation and experimental showed a good agreement for all types of glass and also for all energies.

Theoretical and experimental gamma-rays attenuation characteristics of waste soda-lime glass doped with La2O3 and Gd2O3

The present study explored the gamma-rays shielding characteristics of waste soda-lime glass (SLG) containing lanthanum oxide (La2O3) and gadolinium oxide (Gd2O3) by utilizing theoretical and experimental determinations. For this purpose, both La2O3, and Gd2O3 were separately added as 0.005, 0.05, and 0.5 wt% in place of waste SLG. The glass series of SLGL and SLGG were successfully fabricated via conventional melting techniques. Some physical analyses were done while radiation shielding parameters were figured out by using gamma-rays spectroscopy and XCOM computations to the produced glass specimens. One can easily state that the synthesized glasses showed a transparent appearance without any glass defects. Further, the glass density revealed an increasing trend with the insertion of both substances, but the SLGG series enhanced more. According to the experimental measurements, it was figured out that both oxide additions had the ability to increase the linear attenuation coefficient (LAC) values. The LAC was improved from 0.151 to 0.242 cm−1 for Gd2O3 insertion ration whereas 0.148 to 0.202 cm-1 for La2O3 series. Moreover, a good agreement between the experimental measurements and theoretical calculations was fulfilled. Based on the measured LAC values, other important parameters including mass attenuation coefficient (MAC), half-value layer (HVL), and mean free path (MFP) were evaluated for the investigated glass series. All in all, the authors concluded that SLGG3 glass can compete with commercial radiation shielding glasses.

Microstructure refinement and mechanical properties of the NiCoMnIn alloy obtained by arc melting technique from mechanically alloyed powder

The Ni45.5Co4.5Mn36.6In13.4 alloy was produced by mechanical alloying during high energy ball milling for 70 h. Then, the powder of NiCoMnIn was cold compressed followed by melting of the green compact by vacuum arc melting technique. The structure and mechanical properties of the obtained alloy were systematically studied. The sub-grain refinement of the Ni45.5Co4.5Mn36.6In13.4 alloy produced by the arc melting from the pre-alloyed powder was observed. It was achieved due to the specific distribution of the γ, parent (L21) and martensite (14 M) phases. The average subgrain size was about 10 μm, which is 100 times lower than grain size observed in the reference bulk sample produced by conventional melting technique. The improvement in mechanical strength from 260 MPa to 1250 MPa for reference and bulk alloy prepared from powders respectively was achieved. Reduced Young’s modulus from nanoindentation experiment was lower in bulk alloy produced from pre-alloyed powder than in reference specimen.

Effective sensitization of Eu3+ ions on Eu3+/Nd3+ co-doped multicomponent borosilicate glasses for visible and NIR luminescence applications

Eu3+/Nd3+ co-doped multicomponent borosilicate glasses (ND1E: 10BaO +10ZnF2+10K2O +20SiO2+(49-x) B2O3+1Nd2O3+xEu2O3) were prepared by conventional melting and rapid quench technique to evaluate the effect of Eu3+ ions in the Nd3+ doped glasses. Thermal stability, structural and spectroscopic characteristics of the ND1E glasses were investigated by using DSC, XRD, FTIR, Optical absorption, excitation and emission measurements. The Judd – Ofelt (JO) analysis is implemented to the absorption spectrum of the prepared glassy matrix in order to identify their potential applicability in lasing devices. Enhancement of 7F0 → 5L6 band (394 nm) with the increasing concentration of Eu3+ ion in the Nd3+ excitation spectra (λemi = 1060 nm) reveals the possibility of obtaining the characteristic fluorescence spectra of Nd3+ ion with the typical excitation wavelengths (Nd3+ = 584 nm and Eu3+ = 394 nm) of both rare earth ions and it is further verified from the emission spectrum. This interesting luminescence effect of showing excellent visible and NIR emission under 394 nm excitation mainly attributes the energy transfer mechanism between the RE3+ ions and the reason underlying this effect is discussed in detail with the help of partial energy level diagram. Energy transfer efficiency between the Eu3+ and Nd3+ ions were evaluated by using the radiative lifetimes of the prepared glasses. Also, a comparison of radiative properties and lasing characteristics of Eu3+/Nd3+ co-doped glasses with other Nd3+ glasses are reported. The emission intensities were characterized using CIE chromaticity diagram and the observed CIE coordinates shows a shift towards reddish – orange region with the increase in Eu3+ concentration. The quantum efficiency of the prepared glasses was determined experimentally. The obtained results suggest that the ND1E glassy system can be considered as a potential candidate for visible and NIR luminescence applications.

Energy transfer and red fluorescence properties of (Ce3+/Eu3+):Fluorophosphate glasses for lighting applications

Intense bluish-red color de-excitation by combining Ce3+ and Eu3+ ions has been observed in fluorophosphate (P2O5+K2O+Al2O3+BaF2+NaF2 (PKABfNf)) glasses which were fabricated by adopting conventional melting and rapid quench technique. Photoluminescence spectra, lifetimes, and energy transfer (ET) process in the Ce3+/Eu3+:PKABfNf glasses were studied. The fluorescence spectra of co-doped glasses exhibit broad band emission at blue corresponding to Ce3+ ions which can enhance the intensity of the red emission of Eu3+ via an efficient ET mechanism. The ET from Ce3+to Eu3+ can be explained based on the Blasse's equation and Dexter's theory of resonant ET. Furthermore, critical ET separation of distance (Rc), luminous efficiency due to energy transfer (ηET), CIE chromaticity co-ordinates (x,y), correlated color temperature (CCT) and color purity (CP) were calculated. The results reveal that the optimized Ce3+/Eu3+:PKABfNf glass can be a potential candidate for w-LEDs in lighting applications.

Enhancement of Optical Emission and Dielectric Properties of Eu3+-Doped Na2O–ZnO–TeO2 Glass Material

Europium doped Na2O–ZnO–TeO2 glasses were prepared by conventional melt technique. The differential thermal analysis and thermal gravimetric analysis confirmed the formation of glass with glass transition temperature about 446°C for all the doped glasses. The X-ray diffraction spectra revealed that these glasses were amorphous in nature. The absorption and emission spectra of these prepared samples were characterized by the UV-VIS spectroscopy and photoluminescence studies. It was found that the band gap energy of these glasses decreases rapidly (2.86–1.43 eV) with the increase of doping concentration. Optical properties of the samples had shown the enhanced luminescence at 537 nm (5D0−7F0), at 591 nm (5D0−7F1) and at 614 nm (5D0−7F2) due to doping of europium (Eu3+). The emission cross-section for the transition 5D0–7F2 was also estimated. The dielectric constant of glass samples were studied for different frequencies. The conductivity of the samples was measured and suggested the Arrhenius mechanism of conduction.

The influence of MgO on the crystallization behaviour and properties of SrO-rich phosphosilicate glasses

A series of glass was produced to investigate the effect of MgO/SrO replacement on the crystallization characteristics and properties of phosphosilicate glasses containing high SrO content. The glass samples were synthesized by conventional melting technique based on 5CaO-(40-X)SrO-X MgO– 43SiO2–7P2O5–5CaF2 (where; X = 10, 20, 30 and 40 mol%). The influence of MgO/SrO replacement on phase assemblages, microcrystalline structures, thermal expansion, and mechanical properties was examined as a function of basic chemical compositions and crystallization parameters. Predominant strontium meta-silicates together with strontium fluoroapatite phases are crystallized from the base glass free of magnesium. The substitution of strontium by magnesium up to 50% led to formation strontium akermanite phase Sr2MgSi2O7 at the expense of SrSiO3 phase. Whereas the increase of the MgO/SrO of more than 50%, which led to the crystallization of the clino-enstatite MgSiO3 as a predominant phase. The results show that the α-values of the glass-ceramics are ranged in 94–125 × 10−6 K−1 over the temperature range (25–500 °C). On the other hand, MgO/SrO replacements led to enhancing the microhardness of the resultant crystalline materials from 4713 Mpa to 6744 Mpa. As a result of the designed glass compositions, promising crystalline phases were obtained as well as good thermal and mechanical properties for the resultant glass-ceramics. Therefore, the designed glass-ceramics can be strongly used as biomaterials especially for bone reconstruction applications.

Influence of different alkaline oxide modifiers on VO2+ ions doped zinc borate glasses

Glassy system of composition 20R2O-19ZnO-60B2O3-1V2O5(R is Li, Na and K) was prepared by conventional melting technique. The measured density ρ and calculated molar volume Vm were both found to increase linearly with the atomic number of the alkali element, reflecting the formation of non-bridging oxygen. Additional physical parameters such as vanadium ions concentration, inter-ionic distance of vanadium ions, polaron radius, field strength, refractive index and electrical susceptibility were calculated. Infrared spectra were recorded, vibrational modes were assigned, and the spectra were deconvoluted to calculate the N4 value. The absorption edge and optical band gap were estimated from UV–Vis absorption spectra, and were found to exhibit a clear R2O mol% dependence. The Spin Hamiltonian parameters were calculated from ESR spectra, and the V4+ ions were found to exist as VO2+ ions in octahedral coordination with tetragonal compression. Furthermore, the Δg||/Δg┴ values were decreased with R2O mol% indicating a reduced tetragonal distortion.

Magnetocaloric effect in ErNi2 melt-spun ribbons

ErNi2 ribbons were produced by rapid solidification using the melt spinning technique. Their structural, magnetic and magnetocaloric properties in the as-solidified state were studied by X-ray diffraction, scanning electron microscopy, magnetization and specific heat measurements. Samples are single phase with the MgCu2-type crystal structure, a Curie temperature TC of 6.8 K and a saturation magnetization at 2 K and 5 T of 124.0 A⋅m2/kg. For a magnetic field change μ0ΔH of 5 T (2 T) ribbons show a maximum magnetic entropy change |ΔSMpeak| of 24.1 (16.9) J/(kg⋅K), and an adiabatic temperature change ΔTadmax of 8.1 (4.4) K; this is similar to the previously reported literature for bulk alloys that were processed through conventional melting techniques followed by prolonged thermal annealing. In addition, the samples also show slightly wider ΔSM(T) curves with respect to bulk alloys leading to a larger refrigerant capacity.