Papers by Keyword: Lanthanum

Abstract: Lanthanum (La) and Nickel (Ni)-codoped Strontium Titanate (SrTiO₃) with the formula of Sr_1-xLa_xTi_1-yNi_yO₃ has been synthesized using the coprecipitation method. This research aimed to determine the effect of nickel and lanthanum co-doping on the photocatalytic activity of SrTiO₃. Here, the Ni concentration (y) was constant at 4%, while La concentrations (x) were varied at 1% and 2%. The synthesized samples were tested via X-ray diffraction (XRD) instrument to determine the crystal structure. It exhibited that the crystallite size reduced along with increased lanthanum concentration. The photocatalytic activity of Sr_1-xLa_xTi_1-yNi_yO₃ was observed under UV and Visible light irradiation against methylene blue (MB) pollutant dyes, and the absorption was measured via a UV-Vis spectrophotometer. It revealed that all samples succeeded in degrading MB solution under the two light sources with exposure times of 1, 2, 3, and 4 hours. Further, it was found that photocatalytic activity with UV lamp irradiation resulted in a better degradation percentage than visible light irradiation. The highest degradation about 60% was achieved by Sr_0.99La_0.01Ti_0.96Ni_0.04O₃ under UV light exposure for 4 hours.

Abstract: A chemical bath deposition technique was used to create the transparent, finely adherent ZnS and Lanthanum doped ZnS thin films on a glass substrate. The films were obtained in a water bath with reaction solutions containing Zinc, Lanthanum precursors, and trisodium citrate as a complexing agent. The amorphous nature of the films was confirmed by an X-ray diffractometer and the porosity of the films was checked by field emission scanning electron microscope. The presence of Lanthanum in ZnS films was confirmed by EDS. To find the band gap UV-Visible spectroscopy analysis was carried out. The impurity phase and the Raman modes were recognized by Raman spectroscopy. Further studies on the water splitting and photocatalytic degradation of organic dyes using La-ZnS nanomaterials are underway in our laboratory.

Abstract: The effect of annealing temperature on the structural and magnetic properties of a rare earth (La³⁺) doped cobalt ferrite with fine sediment from the Bengawan Solo River as the source of Fe³⁺ has been studied. Co-presipitation method is use for preparation nanoparticles whole this experiment. In order to modified the physical properties, the annealing treatment of 2000C, 3000C, and 4000C are performed. The obtained nanoparticles are characterized their structural properties by using X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. Then, magnetic properties evaluated by using Vibrating Sample Magnetometer (VSM). XRD results have shown that there is an increase in crystallite size with an increase in the given annealing temperature from 24.56 nm to 27.83 nm. The increase in crystallite size can be attributed to the increase in the internal energy of the crystal structure which promotes atomic diffusion. Meanwhile, there is a decrease in the value of the lattice parameter with an increase in the given annealing temperature. The decrease in lattice parameters with increasing crystallite size is generally due to the lattice parameters reaching a minimum energy with increasing crystallite size. The formation of La³⁺-O^2- for the incorporation of rare earth ions into the lattice requires high energy. The FTIR results show an absorption that appears at the peak around ~580 cm^-1. This indicates that the La³⁺ cation has successfully replaced the original structure of cobalt ferrite. The VSM results show that there is an increase in the value of Hc with an increase in the annealing temperature given from 100 Oe to 160 Oe. This is supported by the increase of anisotropy constant and increasing temperature annealing.

Abstract: The present study was focused on the high-energy ball milling preparation of the oxide dispersed Mo-10 vol.%La₂O₃ composite powder by using two high-energy ball milling systems, including an attritor mill with a horizontally operating rotor and a planetary mill. Microstructural investigations using scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) found out that composite powders with a refined laminated microstructure can be obtained using both milling systems. Under selected milling conditions, Mo-La₂O₃ powder with better particle size homogeneity and more uniform and dispersed ceramic phase distribution was received in the planetary mill that can be connected with the more balanced contribution of breaking and cold welding processes during high energy milling.

Abstract: Malaysia has many potential mineral resources including some rare earth elements (REE) minerals such as monazite. REE play critical roles in the applications of advanced materials. Alkaline fusion was introduce to monazite to break the bonding between Light Rare Earth Elements (LREE) and phosphate. In this study, critical parameter such as fusion temperature (100 °C to 250 °C) and duration (1 to 4 hours) were studied. The results shows that it is possible to recover nearly 100% of Neodymium after 2 hours fusion at 150 °C. In the other hand, more than 99% of Cerium and Lanthanum were recovered after 3 hours fusion at similar temperature. By recover most of the element, expectantly high yield of single LREE can be achieved in the forthcoming.

Abstract: The structure of basic lanthanum orotate (LaOr) were characterized by elemental analysis and infrared spectroscopy. The thermal stability of polyvinyl chloride (PVC) was further studied by Congo red method, oven discoloration method and thermogravimetric analysis. The results showed that LaOr could prolong the oven discoloration time of PVC, and the color was not completely blackened until 120 min. It has a good synergetic effect with dibenzoyl methane (DBM), and the best effect is achieved when LaOr/DBM ratio is 1.8/1.2. The thermal decomposition kinetics experiment showed that adding DBM can effectively improve the activation energy of PVC/LaOr. The stabilization mechanism of PVC was studied by absorbing HCl method and infrared spectroscopy. The results showed that LaOr could not only replace the unstable chlorine atoms on PVC, but also promote the long-term thermal stability of PVC by absorbing HCl.

Abstract: Mechanical properties of Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HA, still need to be modified to improve its function as dental filler or bone implant. HA is usually substituted with other metals to increase its mechanical strength. In this study, HA from chicken eggshells was substituted with La with a concentration variation of 1-3 wt % with a solid chemical reaction at a temperature of 1100 °C for 2 hours. The structure, morphology and mechanical strength of HA/La were characterized by XRD, SEM and Vicker Hardness, respectively. All HA samples adopt the P 63/m space group. Likewise, the IR spectra are similar to each other, which shows the formation of the HA structure, indicated by the presence of the -OH and PO₄^3- groups. HA/La with the highest hardness value of 1.85 GPa is obtained from the 3 wt % La doping. The higher the La content added, the higher the hardness of the hydroxyapatite. The doping of 3% La increased the hardness of HA 17%.

Abstract: Methods for the quantitative determination of lanthanum that have been developed are generally spectroscopic methods such as inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectrometry (ICP-AES), and X-ray fluorescence spectrometry, which has relatively high operational costs. The feasibility of the potentiometric method using ion selective electrode (ISE) as an alternative method for lanthanum (III) determination needs to be studied because it is simple, easy to use, and has high sensitivity and selectivity. In this study, we developed ion selective electrode using PTFE membrane impregnated with tributyl phosphate (TBP) as ionophore. TBP is commonly used as a complexing agent for rare-earth ions in supported liquid membrane (SLM) separation process. We found that the compound can be used as an ionophore for ISE. This study aims to make a lanthanum ion selective electrode (III) (La-ISE) which has a Nernstian response. The parameters studied in the construction of this electrode were the effects of PTFE membrane immersion ionophore solution, ionic strength adjuster (ISA), and the inner solution composition. The performance parameters studied for the La-ISE were linear range, response time, detection limit, selectivity, and the lifetime of the electrode. Construction of the electrode begins with the preparation of the PTFE membrane as the main component. PTFE membrane was impregnated for 12 hours in the TBP solution having a concentration of 0.25 M or 0.50 M in kerosene. After it was dried, the membrane was attached to the end of the electrode tube with adhesive. Then, the electrode was filled with an internal solution containing a mixture of KCl 10^-3 M with La (III) 10^-3 M. The internal reference electrode was Ag/AgCl electrode. Before it was used, the electrode was soaked in a solution of La (III) 10^-3 M for 12 hours.The effect of TBP concentration on the electrode performance was studied using two concentrations of TBP: 0.25 M and 0.50 M. The calibration curves obtained using both electrodes have good linearity. Nernst factor obtained from both electrodes is similar, although the Nernst factor obtained with an electrode having 0.50 M TBP closer to the theoretical value.ISA used in the measurement was KNO₃. The effect of ISA on the performance of the electrode was studied using electrodes containing TBP with the concentration of 0.25 M or 0.50 M. The concentration of KNO₃ used in this study was 0.01 M and 0.10 M. The Nernst factors obtained with electrodes containing 0.25 M TBP, in general, higher than those obtained with electrodes containing 0.50 M TBP in the same ISA. Electrode containing 0.50 M TBP resulted in the Nernst factor close to theoretical value when a measurement was conducted in 0.10 M KNO₃.

Abstract: Comparison of the crystalline structure and magnetic properties in CoFe₂O₄ and CoLa_0.1Fe_1.9O₄ nanoparticles have been studied. The obtained samples are characterized by using X-Ray Diffractometer (XRD), Fourier Transform InfraRed (FTIR) and Vibrating Sample Magnetometer (VSM). The XRD results show that the crystallite size of the samples are 24.539 nm and 28.772 nm for the CoFe₂O₄ and CoLa_0.1Fe_1.9O₄ nano particles, respectively. Furthermore, the crystalline strain is 0.00460 and lightly decreases to 0.00392 with the presence of lanthanum. The different of the atomic radius for both Fe³⁺ (1.26 Å) and La³⁺ (1.87 Å) should attribute to the change of the crystalline strain. FTIR results show that the absorption peak of the CoFe₂O₄ occur at k = 591.21/cm and the CoLa_0.1Fe_1.9O₄ is 594.10/cm. This indicate that the lanthanum cation successfully substitutes to the original bonding-structure of the CoFe₂O₄. VSM results show that the H_C are 1.02 kOe and 0.705 kOe for the samples without and with La³⁺ cations. Moreover, the M_S is equal 69.625 emu/g and decrease of 55.70 emu/g with the present of the La³⁺ cations. Finally, the strains-induce-magnetism should contribute to the changes of the M_S that associated with changes in crystalline strains at the previous discussion.

Abstract: In this research, CoFe_2-xLa_xO₄-based smart magnetic material has been developed which will be applied as a microwave absorbing material. This smart magnetic material is an artificial advanced material which has properties such as electromagnetic waves so that it is able to respond to the presence of microwaves through the mechanism of spin electron resonance and wall resonance domain. This smart magnetic material consists of a combination of rare earth metal elements (spin magnetic in the f orbital configuration) and transition metal elements (spin magnetic in the d orbital configuration) with a semi-hard magnetic structure. This semi-hard is a characteristic of magnetic properties which is between hard magnetic and soft magnetic properties. This characteristic of the semi-hard magnetic properties is needed so that this material has the ability to absorb microwaves. Substitution of lanthanum into cobalt ferrite CoFe_2-xLa_xO₄ for La³⁺ (x = 0 - 0.8) has been synthesized using the solid reaction method through mechanical deformation techniques. The refinement result of X-ray diffraction shows that the sample contains 2 phases with increasing of x compositions. Particle morphology and elementary analysis were observed respectively by using a scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). It was concluded that the effect of La substitution on CoFe_2-xLa_xO₄ resulted in changes in the crystal structure parameters and phase transformation as a function of composition.