Sulphide based anode material for lithium rechargeable battery

In this study, lead sulphide (PbS) was prepared by the chemical bath deposition technique. The sample was characterized by X-ray diffraction (XRD), Energy Dispersive Analysis of X-rays (EDAX) and cyclic voltammetry. EDAX spectrum shows peaks attributable to lead and sulphur. The EDAX analysis also shows that the prepared sample is stoichiometric. Cyclic voltammetry experiments were recorded at 100 mV·s⁻¹ and 400 mV·s⁻¹ scan rates. Results show that the rate controlling electrochemical reaction is electron transfer. The presence of redox waves shows that the lithium intercalation and deintercalation can occur as a result of lattice expansion in PbS. There were no differences in the PbS XRD data before and after the cyclic voltammetry experiments indicating that the PbS structure is not modified upon lithium ion intercalation and deintercalation in PbS. The discharge characteristics for 35 cycles of the cell using the LiCoO₂/PbS couple is presented indicating the possible development of such materials as anode in lithium ion cells.     

Dielectric and conduction mechanism studies of PVA-orthophosphoric acid polymer electrolyte

Polyvinyl alcohol (PVA)-based proton conducting polymer electrolytes have been prepared by the solution cast technique. The conductivity is observed to increase from 10⁻⁹ to 10⁻⁴ S cm⁻¹ as a result of orthophosphoric acid (H₃PO₄) addition. The plot of conductivity vs temperature shows that a phase transition occurred at 343 K in the sample PVA-33 wt% H₃PO₄. The β-relaxation peak is observed at 313 K. The glass transition temperature of PVA-33 wt% H₃PO₄ is 343 K. Orthophosphoric acid seems to play a dual role, i.e., as a proton source and as a plasticizer. The ac conductivity σ _ac = Aω ^s was also calculated in the temperature range from 303 to 353 K. The conduction mechanism was inferred by plotting the graph of s vs T from which the conduction mechanism for sample PVA-17 wt% H₃PO₄ was inferred to occur by way of the overlapping large polaron tunneling (OLPT) model and the conduction mechanism for the sample PVA-33 wt% H₃PO₄ by way of the correlated barrier height (CBH) model.     

XRD, conductivity and FTIR studies on LiI-Li2WO4-Li3PO4 prepared by low temperature sintering

Different amounts of Li₃PO₄ were mixed to a fixed ratio of LiI:Li₂WO₄, ground and pelletised before subjected to sintering at 70°C for 7 days. XRD shows that the product formed after sintering process is most likely Li₆P₄W₈O₃₂ due to peaks present at 10.6°, 22.4°, 24.0°, 24.4, 26.2°, 32.4° and 34.0°. Conductivity studies show that the sample with 25 wt.% Li₃PO₄ exhibits the highest room temperature conductivity of 3.42×10⁻³ Scm⁻¹. Conductivity is expected to occur through channel-like structures which could have formed due to corner or edge sharing of polyhedra. FTIR studies have shown the existence of WO₄ tetrahedra and WO₆ octahedral at 850 cm⁻¹ and 952 cm⁻¹, and phosphate tetrahedral at 564 cm⁻¹, 700 cm⁻¹, 890 cm⁻¹ and 1030 cm⁻¹.     

Switchable Q-switched and laser operating mode-locked erbium-doped fiber in the L-band region

We demonstrate a switchable Q-switched and mode-locked erbium-doped fiber laser （EDFL） operating in the L-band region using the nonlinear polarization rotation effect. The switching operation is achieved by controlling intensity-dependent loss using a polarization controller. In Q-switching mode, the EDFL produces a pulse train with a repetition rate of 21.1 kHz, pulse width of 7.7 #s, and pulse energy of 13.6 nJ. The EDFL also generates a multi-wavelength comb with a very narrow and constant wavelength spacing of 0.045 nm and optical signal-to-noise ratio of at least l0 dB. During mode locking, the EDFL produces stretched pulses with 3-dB bandwidth of 26.2 nm, pulse width of 350 fs, repetition rate of 2.38 MHz, and pulse energy of 48.56 pJ.     

Determination of total arsenic in soil and arsenic-resistant bacteria from selected ground water in Kandal Province, Cambodia

Cambodia has geological environments conducive to generation of high-arsenic groundwater and people are at high risk of chronic arsenic exposure. The aims of this study are to investigate the concentration of total arsenic and to isolate and identify arsenic-resistant bacteria from selected locations in Kandal Province, Cambodia. The INAA technique was used to measure the concentration of total arsenic in soils. The arsenic concentrations in soils were above permissible 5 mg/kg, ranging from 5.34 to 27.81 mg/kg. Bacteria resistant to arsenic from two arsenic-contaminated wells in Preak Russey were isolated by enrichment method in nutrient broth (NB). Colonies isolated from NB was then grown on minimal salt media (MSM) added with arsenic at increasing concentrations of 10, 20, 30, 50, 100 and 250 ppm. Two isolates that can tolerate 750 ppm of arsenic were identified as Enterobacter agglomerans and Acinetobacter lwoffii based on a series of biochemical, physiological and morphological analysis. Optimum growth of both isolates ranged from pH 6.6 to 7.0 and 30–35 °C. E. agglomerans and A. lwoffii were able to remove 66.4 and 64.1 % of arsenic, respectively at the initial concentration of 750 ppm, within 72 h of incubation. Using energy dispersive X-ray technique, the percentage of arsenic absorbed by E. agglomerans and A. lwoffii was 0.09 and 0.15 %, respectively. This study suggested that arsenic-resistant E. agglomerans and A. lwoffii removed arsenic from media due to their ability to absorb arsenic.     

Determination of neutron flux parameters in PUSPATI TRIGA Mark II Research Reactor, Malaysia

In standardization NAA, it is necessary to characterize the neutron spectrum parameters such as epithermal neutron flux shape factor (α), thermal to epithermal neutron flux ratio (f), thermal neutron flux (φ _th) and epithermal neutron flux (φ _epi) in the irradiation facility to determine the concentration of an element in the sample using absolute and k ₀ standardization methods. The α and f were determined using Cd-ratio multi monitor method using experimental data obtained in PUSPATI TRIGA Mark II research reactor at four irradiation positions (10, 20, 30 and 40) of the rotary rack. The calculated values of α and f ranged from 0.006 to 0.0281 and 18.56 to 19.12 respectively. The average values of φ _th and φ _epi were found as 2.33 × 10¹² and 1.23 × 10¹¹ n cm^?2 s^?1 respectively. Moreover, a comparison of the neutron flux parameters in the present study shows an acceptable level of consistency with those of previous studies.     

Investigate the capability of INAA absolute method to determine the concentrations of 238U and 232Th in rock samples

This work aimed to study the capability of INAA absolute method in determining the elemental concentration of ²³⁸U and ²³²Th in the rock samples. The INAA absolute method was implemented in PUSPATI TRIGA Mark II research reactor, Malaysian Nuclear Agency (NM). The accuracy of INAA absolute method was performed by analyzing the IAEA certified reference material (CRM) Soil-7. The analytical results showed the deviations between experimental and certified values were mostly less than 10 % with Z-score in most cases less than 1. In general, the results of analysed CRM Soil-7 show a good agreement between certified and experimental results which mean that the INAA absolute method can be used accurately for elemental analysis of uranium and thorium in various types of samples. The concentration of ²³⁸U and ²³²Th ranged from 1.77 to 24.25 and 0.88 to 95.50 ppm respectively. The highest value of ²³⁸U and ²³²Th was recorded for granite rock sample G17 of ²³⁸U and sample G9 of ²³²Th, whereas the lower value was 1.77 ppm of ²³⁸U recorded in sandstone rock and 0.88 ppm of ²³²Th for gabbro. Moreover, a comparison of the ²³⁸U and ²³²Th results obtained by the INAA absolute method shows an acceptable level of consistency with those obtained by the INAA relative method.     

Hybrid flat gain C-band optical amplifier with Zr-based erbium-doped fiber and semiconductor optical amplifier

An efficient gain-flattened C-band optical amplifier is demonstrated using a hybrid configuration with a Zirconia-based Erbium-doped fibre (Zr-EDF) and a semiconductor optical amplifier (SOA). The amplifier utilizes a two-stage structure with a midway isolator to improve flat gain characteristic and reduce noise figure. At input signal power of −30 dBm, a flat gain of 28 dB is obtained from wavelength region of 1530 to 1560 nm with gain variation of less than 4 dB. The noise figure is maintained below 11 dB at the flat-gain region. This amplifier has the potential to be used in the high channel count dense wavelength division multiplexing system due to its simplicity and compact design.     

Dielectric behaviour and AC conductivity of LiCF3SO3 doped H-chitosan polymer films

H-chitosan that exhibited solubility in THF was prepared by acyl modification of chitosan. Films of H-chitosan containing LiCF₃SO₃ were prepared by the solution cast technique. The effect of salt concentration on the frequency-dependent dielectric properties of H-chitosan: LiCF₃SO₃ complexes were investigated by impedance spectroscopy, in the temperature range from 243 to 373 K. The dielectric properties and ac conductivity of the samples prepared have been analyzed. The dielectric constant increases sharply with temperature in the low frequency region. At higher frequencies, the effect of temperature on the dielectric constant is negligible. The values of dielectric constant were also found to increase with increasing conductivity of the samples. The imaginary part, M_i of electrical modulus shows the formation of dispersion peak. Relaxation times for the ionic charge carriers were extracted from the loss tangent maximum peak at various temperatures. The plot of relaxation times as a function of temperature shows Arrhenius type behaviour. The ac conductivity was found to obey the universal power law and as the temperature increases, the feature of σ(θ) α θⁿ is more predominant. The temperature dependence of the power law exponent n is reasonably interpreted by the overlapping large polaron tunneling (OLPT) model.