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Zn and Cu Co-Doped Li4Ti5O12 Anode Material for Lithium Ion Batteries
No full textThis thesis is submitted to the Department of Chemistry, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Chemistry, June 2019.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 61-70).Lithium-ion batteries have been advanced the battery technology because of their
prevalent power sources for electric vehicles and portable electronics devices. Spinel
structure of lithium titanium oxide Li4Ti5O12 (LTO) has commended significant interest
as an anode material for lithium-ion batteries because of several advantages such as high
energy density, high safety, good chemical stability, long-life time, a flat operating
voltage about 1.55 V and low cost. Modification of the surface structure of LTO based
anode material by Cu and Zn has been significantly enhanced the conductivity of the
electrode material by suppressing the decomposition of the electrode material and
influencing their phase structure in some cases. Advanced spectroscopic techniques, such
as Fourier-Transform Infrared Spectroscopy (FTIR), scanning electron microscopy
(SEM), (EDX) and X-ray diffraction (XRD) are applied for the characterization of
morphology, particle size and crystal structure of the prepared LTO based anode
materials.
In the finger print region sharp low frequency characteristic IR bands observed below
800 cm-1 which can be attributed to the symmetric stretching vibrations of Ti-O bonds of
TiO6 octahedron in pure Li4Ti5O12, Li4Ti4.9Cu0.05Zn0.05O12, Li3.9Ti5Cu0.05Zn0.05O12 and
Li3.9Ti4.9Cu0.1Zn0.1O12. At the same time strong stretching bands at around 2360.87,
2341.58 and 2331.94 cm-1 can be assigned to the Ti-O-Ti bonds in the prepared LTO and
LTO based anode materials and corresponds to the published results.
Li4Ti5O12 possess a face-centered cubic spinel structure grounded on space group
symmetry of Fd3m. In the Li4Ti5O12 spinel structure, tetrahedral 8a sites are completely
taken up by Li and the octahedral 16d sites are arbitrarily occupied by Li and Ti with an
atomic ratio of 1:5 in a cubic close-packed oxygen array. The characteristic X-ray
diffraction peaks of the prepared samples are found at 2θ of 18.3, 35.58, 43.2449, 43.1,
57.2065, 62.8447, and 66.1006 which correspond to the planes (111). (311), (400), (333),
(440) and (531), respectively. The lattice parameter values were calculated for Li4Ti5O12,
Li4Ti4.9Cu0.05Zn0.05O12, Li3.9Ti5Cu0.05Zn0.05O12 and Li3.9Ti4.9Cu0.1Zn0.1O12 and the values
are 8.3692 Å, 8.3742 Å, 8.3834 Å and 8.3709 Å, respectively. XRD spectra that both
pure Li4Ti5O12 and Cu & Zn co-doped LTOs showed peaks representing single phase of
spinel lithium titanium oxide (cubic phase, space group Fd-3m) which are in good agreement with Joint Committee on Powder Diffraction Standards, JCPDS (No. 26-
1198) data.
SEM photographs of prepared pure LTO (Li4Ti5O12), Li4Ti4.9Cu0.05Zn0.05O12,
Li3.9Ti5Cu0.05Zn0.05O12 and Li3.9Ti4.9Cu0.1Zn0.1O12 possess chips like shape. No significant
change happened in the morphologies due to the co-doping of different ratio of Cu & Zn
into Li4Ti5O12. The morphologies of all prepared LTOs are almost same that correspond
the X-ray diffraction result.Md. Mehedi HasanMaster of Science in Chemistr
Development of Low Volume Substrate Based Particulate Matter Sampler
No full textThis thesis is submitted to the Department of Civil Engineering, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Civil Engineering, January 2019.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 59-62).Air pollution has arisen as a major concern in the present era due to its adverse impact on human health and surrounding environment. Among the six criteria pollutants, the atmospheric particulate matters have been considered as a challenge to ensure air quality in Bangladesh because the Air Quality Index (AQI) value for particulate matter (PM) is mostly ranges from caution to extremely unhealthy. However, air quality sampling and monitoring program in Bangladesh is very insignificant due to expensive PM sampler dealing with nano to micro scale parameters. This study focuses on the development of a low cost PM sampler which is low volume, multi-nozzle and substrate based. The design parameters such as nozzle number, nozzle diameter and nozzle to plate distance were determined from the dimensionless factor named stokes number ( ) introducing the Reynolds number (Re). The optimal nozzle configuration array was selected to avoid the effect of cross flow parameter upon the collection characteristics.
The PM sampler operates at a flow rate of 5 L/min and consists of two different sets of circular nozzles designed for cut-off PM10 (Diameter of particle less than 10μm) and PM2.5 (Diameter of particle less than 2.5μm). The designed PM sampler was fabricated from the Fab-Lab of Khulna University of Engineering and Technology (KUET) using the silver metallic PLA filament which is light weight and corrosion resistant. Microscopic analysis of the substrate was performed to investigate cut-off performance. Gravimetric analysis was conducted to evaluate the field performance of the developed PM with a sensor based (light-scattering) reference sampler within the KUET campus. The loss of particle on this study was determined by counting the particle inside the sampler’s wall as well as the stagnant corner point of the inside of the PM sampler.
A stage wise sharp cut-off was found for PM10 and PM2.5 of developed PM sampler. The average mass concentration of PM10 and PM2.5 was found as 108μg/m3 and 49μg/m3, respectively. The average mass concentration of PM10 and PM2.5 was found very close to the reference sampler. The average particle loss for the impactor nozzle and sampler body was found 12.0% which shows good agreement with previous studies. The obtained cross-flow parameter for the stage PM10 (0.20) and PM2.5 (0.29) were also satisfying the critical value (< 1.2). Overall, the PM sampler was developed as light-weight, easy to use, portable, low maintenance required, and low cost which can be implemented for PM monitoring in Bangladesh.Md. Shah AlamMaster of Science in Civil Engineerin
Studies on Volumetric and Viscometric Properties on N-Acetylcysteine in Acetic Acid-Water Binary and Ternary Mixtures
No full textThis thesis is submitted to the Department of Chemistry, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Chemistry, June 2019.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 68-72).The density and viscosity of NAC (0.10 to 1.00) mol.L−1 in H2O, CH3COOH and
H2O–CH3COOH mixed solutions were measured and analyzed over the whole
concentration range at (298.15, 303.15, 308.15, 313.15 and 318.15) K temperatures. The
apparent molar volumes were obtained from the experimental density data. In the NAC–
H2O and NAC in [9:1] [H2O–CH3COOH] solvent systems the apparent molar volume of
NAC increases, whereas in the NAC–CH3COOH and NAC in [4:1], [7:3] and [3:2]
[H2O–CH3COOH] solvent systems it decreases. With the help of experimental density
data apparent molar volume at infinite dilution, and Sv values were also calculated. The
apparent molar volume at infinite dilution gives an idea about the presence of
solutesolvent interactions while Sv is the experimental slopes which give an idea about
the prevailing solutesolute interactions in the mixtures. The calculated data indicate that
there may be solute-solute and solute-solvent interactions present in the binary and
ternary solutions. Binary and ternary systems showed rapid increase of viscosity values
with the increase in NAC concentration but the values of viscosity decreased with the
increase of temperature for all the experimented system. The viscosity data were
employed to find out the viscosity (A, B) coefficients, change of free energy, G*,
change of enthalpy, H* as well as change of entropy, S*. From these thermodynamic
parameters state of the spontaneity of the investigated systems were identified.
Moreover, negative A and positive B co-efficient values suggesting that weak solutesolute
but strong solute-solvent interaction present in the binary and ternary solution. On
the basis of this data, the predominant molecular interactions occurring between NAC–
H2O and NAC in [9:1] [H2O–CH3COOH] solvent systems were found to be solute-solute
interaction, whereas in NAC–CH3COOH and NAC in [4:1], [7:3] and [3:2] [H2O–
CH3COOH] solvent systems solute-solvent interaction were predominant.Banamali VattyaMaster of Science in Chemistr
Classification Accuracy Enhancement of fNIR based Imagery Movement by Modified Common Spatial Pattern
No full textThis thesis is submitted to the Department of Biomedical Engineering, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Engineering in Biomedical Engineering, January 2019.Cataloged from PDF Version of Thesis.Includes bibliographical references in each chapter.Motor imagery event classification from functional near-infrared spectroscopy (fNIRS) is one of the most interesting problems of current brain-computer interfaces (BCIs) challenges because it needs no additional data guiding visual or listening protocol. A vital step of the fNIRS signal classification by machine learning approach is feature extraction. The feature extraction from multiple channel fNIRS signal is always challenging due to its high dimensionality. There exist several conventional feature extraction procedures like principal component analysis, nonlinear principal component analysis, independent component analysis, norm analysis, spectral norm analysis, etc. This research work studies such existing feature extraction method to classify the hand movement events of fNIRS signals. The accuracies of these methods have been found less than the expectation. Therefore, some more accurate method is needed. In this regard, usually common spatial pattern (CSP) is used to reduce the dimensional reduction and improving the classification accuracy. The conventional CSP method can be proven also ineffective for the motor imagery fNIRS signal due to its high level of trial to trial variations. The present research work proposes an algorithm named by standardized common spatial pattern (SCSP) based feature extraction method for fNIRS based motor imagery classification which can perform well in the context of the trial to trial significant variation. The classification results corresponding to the proposed feature extraction method reveal that the proposed SCSP algorithm outperformed the conventional CSP method and channel-wise method for classifying the two motor imagery event classifications. For classification accuracy measurement, four well-known classifiers: artificial neural network (ANN), k-nearest neighbor (kNN), support vector machine (SVM), and linear discriminant analysis (LDA) have been used. We have utilized both the fNIRS data of oxidized hemoglobin (HbO) and deoxidized hemoglobin (HbR) for classifying the motor imagery fNIRS data with the conventional and proposed methods. From the comparisons, we have found that in both cases, the proposed method outperforms the conventional methods in the context of the classification accuracies. To validate the classification accuracies, the sensitivities and specificities of the classifier are also calculated in this work. We believe that the proposed SCSP method will contribute in the field of feature extraction method for other types of fNIRS based BCI system, effectively. In addition, this method may be applied for the feature extraction to the other multidimensional signals so far.Md. Faisal KabirMaster of Science in Engineering in Biomedical Engineerin
