Supar Rohani

Chemical durability of Yb doped lead tellurite glass: Effect of solution pH

Series of glass based on (80-x)TeO2-10PbO-10PbCl2-xYb2O3 where 0.0 ≤ x ≤ 3.0 has been successfully prepared by melt quenching technique. The amorphous nature of glass has been determined by X-ray diffraction method. Their corrosion behavior was investigated using the FTIR spectroscopy technique on the sample that has been immersed in distilled water and in aqueous solution of pH 4 and pH 9 for 10 days. There were three major absorption peaks around 3600 cm-1, 889 cm-1 and 470 cm-1 has been observed. The intensity of each peak was found to vary with the Yb3+ content.

Elastic constant determination of hardwoods using ultrasonic insertion technique.

HighlightsInsertion technique is used to determine elastic constant of hardwoods.Elastic constants are determined in longitudinal, tangential and radial directions.Twelve Malaysian hardwoods are used to validate the use of insertion technique.Results from insertion technique are compared with through‐transmission technique. ABSTRACT Ultrasonic insertion technique (IT) is an ultrasonic technique which involves sample immersion in a solution to determine its acoustic properties. IT is normally used to determine the acoustic properties of a medical phantom. We proposed the use of IT as an alternative technique to the common contact ultrasonic technique: through‐transmission technique (TT) for determining the elastic constant of hardwoods in longitudinal, tangential and radial directions. The elastic constant of twelve rectangular‐shaped Malaysian hardwoods from three different categories; heavy, medium and light with the density ranging from 602 to 992 kg m−3 were determined using IT and TT. Both techniques were carried out at 24.0 °C surrounding temperature and utilized 2.25 MHz ultrasonic transducers. Data from both techniques were compared to validate the use of the proposed technique. Findings indicated that IT offers consistent and accurate results for, tangential and radial elastic constants (TEC and REC) within 8.89% and 5.86% differences, respectively compared to TT for all tested hardwoods. IT offers an alternative technique for TEC and REC determinations of precious wood samples.

Ultrasonic B-Scan of Adhesive Bonded Thin Aluminum Sheet

Ultrasonic inspection using b-scan (brightness scan) and its application for discontinuity and flaws detection were investigated. Brightness scan is one of the ultrasonic technique’s branches, it provides thorough image of the material which undergone inspection via density of the material where then depicted in different colour in conjunction with the acoustic impedance of the phase gone through by the sound wave. The sound wave generated with a piezoelectric transducer was propagated through aluminum wafer samples and were identified by the b-scan system. Its ability to detect flaw at certain depth which was introduced manually been examined. Experimental results show different brightness characteristic, depending on the adhesive treatments, type of material and medium when the waves pass through in each sample. Brightness scan system was proven to be reliable non-destructive testing method in ultrasonic for inspection of structural bonded materials.

The effect of Nd3+ composition on judd-ofelt analysis of lithium niobate tellurite glasses codoped with Er3+

The modification of absorption characteristics in rare-earth doped tellurite glasses is important in photonics application. The Er3+/Nd3+ doped glasses of the form (69-x)TeO2–15Li2CO3–15Nb2O5–1Er2O3 -(x)Nd2O3 with x =0.2 and 0.6 mol% are successfully made by using conventional melt-quenching technique. The Judd-Ofelt analysis is to determine the local structure and bonding in the vicinity of rare-earth ions. The oscillator strengths are calculated from the absorption spectra and used to evaluate Judd-Ofelt intensity parameters (Ωλ, λ=2, 4 and 6). The values of Ω4 and Ω6 change with the increase of Nd3+ concentration is ascribed to the change in glass network structures. The values of Ω2 are increased from 1.53 to 37.13 (10-22) cm2 with the increase of Nd3+ concentration which indicate an increase in the covalent nature of Nd-O bond and less centrosymmetrical the ion sites. The decrease in τrad for each level with the increase of Nd3+ concentration signifies on how fast a particular level gets depopulated. The values of β for the transitions 4G5/2, 2G7/2 → 4I9/2, 2H11/2 → 4I9/2 and 4F9/2 → 4I9/2 are found to lie in between 99.6 to 100.0%.

Ultrasonic Bulk Waves Measurements for Defect Detection of Composite Materials

The defect detection in composite material is important for its quality control where the hidden defect such as crack, corrosion, notch, holes, void and porosity can develop. In this paper, the ultrasonic bulk wave measurements of longitudinal and shear waves are used to identify defect in the multilayered composite material. This study employs pulse echo technique and utilized angle beam transducer. The composite material model investigated in this contribution are made of 24 mm and 12 mm thick Aluminium plates with a width of 100 mm and a length of 203 mm which are separated with an approximately 1 mm thick oil layer. A simulated defect is created in the composite test material by drilling a hole with 2.5 mm diameter and 3 mm depth on the bottom surface of the third layer material. Finding indicates that the defect is located at 53.39 mm from transducer and the percentage difference of the defect location compared to the calculation method is 7%. It indicates that the proposed method can be use to detect defect in multilayered composite material within 10% accuracy compared to the calculation method.

Acoustic Characterisation of Konjac Glucomannan Gel as a Medical Phantom

Acoustic properties are the main criteria to evaluate the compatibility of tested materials as a medical phantom. We determined the acoustic properties of konjac glucomannan (KGM) gel to verify its compatibility as a medical phantom. The acoustic properties measurement employed ultrasonic insertion technique and utilized two identical transducers of 5 MHz center frequencies. One KGM gel block with 5.62 mm thickness was used as sample to determine its longitudinal speed, acoustic impedance and attenuation coefficient at three different water temperatures; (21.5 ± 0.1), (22.5 ± 0.1) and (23.5 ± 0.1) °C. Findings indicated that its longitudinal speed and acoustic impedance increased from (1495 ± 1) to (1499 ± 1) m s-1 and (1.555 ± 0.001) to (1.559 ± 0.001) × 106 kg m-2 s-1 as the water temperature increased from (21.5 ± 0.1) to (23.5 ± 0.1) °C. It also indicated that its attenuation coefficient varied around (0.1303 ± 0.0107) to (0.1373 ± 0.0103) dB cm-1 with increasing water temperature. KGM gel is compatible to be a medical phantom since its acoustic properties are comparable to the acoustic properties of human soft tissue.

Growth and Characterization of Titanium Doped Lithium Niobate Single Crystal Using Czochralski Technique

A successful growth of the titanium-doped lithium niobate (Ti: LiNbO3) single crystal by Czochralski method is reported. By preserving an effective control of growth parameters such as maintaining accurate temperature gradient by controlling its output power and growth rate as well as wisely choosing the right pulling rate and speed rotation, the Ti:LiNbO3 single crystal successfully produced using Automatic Diameter Control-Crystal Growth System (ADC-CGS). The structural and optical analyses have been done by using X-ray Diffractometer (XRD), Differential Thermal Analyzer (DTA) and Ultraviolet-Visible (UV-Vis) spectroscopy. The crystallinity of the sample has been confirmed using XRD and DTA has been used to determine the crystal nature of the sample. The position of fundamental absorption edge was recorded via transmission spectra in UV and visible region.

Effect of Nd3+ on the properties of lithium niobium borate crystal and glass

1 mol% of neodymium-doped lithium niobium borate (NdLNB) glass and crystal have been produced by using melt-quenching and Czochralski technique, respectively. The synthesis, growth and characterizations of the samples were reported. X-ray diffraction (XRD), Differential thermal analyzer (DTA), Ultraviolet-Visible-Near-Infrared (UV-Vis-NIR) and Photoluminescence (PL) spectroscopic characterizations were made to examine the influence of Nd3+ on the physical, structural and optical properties of the samples. Various physical properties such as density, molar volume, ion concentration, polaron radius, inter-nuclear distance and field strength were calculated. The as-quenched glass was amorphous whereas crystal was crystalline as established via XRD studies. UV-Vis-NIR spectra exhibited eight prominent bands centered at 353, 475, 524, 583, 681, 745, 803, 875 nm corresponding to the transitions from the ground state to 4D3/2, 2G9/2, 4G7/2, 4G5/2, 4F9/2, 4F7/2, 4F5/2, 4F3/2 excited states, respectively. Moreover, the emission spectra at 355 nm excitation displayed several peaks that contributed to the transition of(4F3/2→4I9/2) and (4F3/2→4I11/2), respectively. Fluorescence lifetime was recorded at 53.69 µs for the glass whereas the crystal was recorded at 43.62 µs. It was found that Nd3+ ions affected the physical, structural and optical properties of the glass and crystal samples.

The Ligand Fields Characterizations within Erbium-Tellurite Glass Network via Gold Nanoparticles Concentration Variation

Glass samples of composition 79TeO2 – 15PbO – 5PbCl2 – 1Er2O3 – (x)AuCl3 with (0.0 ≤ x ≤ 0.1 mol%) were successfully synthesized by using melt-quenching technique. The impacts of gold nanoparticles (GNPs) concentration in stimulating the ligand field interaction inside the erbium-tellurite glass network were inspected. Amorphous nature of the sample was confirmed through XRD pattern. TEM images display the existence of GNPs with average diameter ~1.24 nm. Optical absorption spectra were recorded in the UV-Visible range. The absorption displays several prominent peaks corresponding to the transitions from the ground state to the excited states of Er3+ ion. The compositional dependence of the ligand parameters in terms of crystal field strength and Racah parameter were determined.