Optical characterization of thermal transport in multifunctional materials

Understanding thermal transport properties of materials is essential for both device applications and materials physics. Thermal conductivity and interface thermal conductance are fundamental materials properties and important engineering parameters for small-scale device applications. In addition, the effect of isotopic mass disorder on the vibrational properties of ultrahigh thermal conductivity material becomes important with significantly reduced anharmonicity and the improvements in the quality of crystal growth. In this thesis, I use ultrafast pump-probe laser based optical characterization technique to experimentally investigate anisotropic thermal transport properties of layered InSe that is recently prepared in two-dimensional (2D) structures and have distinct in-plane anisotropies. InSe is a promising candidate for next-generation electronics and optoelectronics, owing to its high electron mobility and direct optical bandgap in the few-layer limit. The knowledge of thermal transport properties is needed for engineering heat dissipation in devices. I report the room-temperature thermal conductivity of exfoliated crystals of InSe along the through-plane and in-plane directions using conventional and beam offset time domain thermoreflectance (TDTR), respectively. InSe crystals with varying thicknesses were prepared by mechanical exfoliation onto Si(100) wafers followed by immediate encapsulation with a 3-nm-thick AlOx passivation layer to prevent ambient degradation prior to coating with metal films for TDTR measurements. The measured thermal conductivity in the in-plane direction, Λin ≈ 8.5 ± 2 W/m-K, is an order of magnitude higher than that in the through-plane direction, Λthrough ≈ 0.76 ± 0.15 W/m-K, which implies a high thermal anisotropy ≈ 11 ± 3. This relatively high anisotropy and low thermal conductivity compared to other layered semiconductors imply that InSe will require unique thermal management considerations when implemented in electronic, optoelectronic, and thermoelectric applications. The second topic I investigate is the effect of isotopic disorder on the vibrational properties of cubic boron arsenide (c-BAs) at room temperature using Raman spectroscopy. Boron arsenide is at the forefront of research on ultrahigh thermal conductivity materials. I report a Raman scattering study of isotopically tailored cubic boron arsenide single crystals for 11 isotopic compositions spanning the range from nearly pure c-10BAs to nearly pure c-11BAs. The results provide insights on the effects of strong mass disorder on optical phonons and the appearance of two-mode behavior in the Raman spectra of mixed crystals, not seen before in isotopically disordered materials. Strong isotope disorder also relaxes the one-phonon Raman selection rules, resulting in disorder activated Raman scattering by acoustic and optical phonons

Investigation on the Effect of Cable Length on Pulse Shape of High Voltage High Pulse Power Supply

In the present scenario of pulse power applications, transmission of high voltage pulses varies as per load condition. In the early days of its application, High Voltage High Pulse Power Supply (HVHPPS) design saw short distance between load and source, where the effect of cable length was not taken into account for design. This paper presents the effect of cable length on pulse shape of High Voltage High Pulse Power Supply. The load under observation is Klystron based high energy particle accelerator system. The performance of pulse power systems were observed continuously on a daily basis throughout the year and detailed analysis was carried out. This paper generates the model of pulse forming system and provides details of pattern distortion of the pulse shape due to various dynamic parameter changes i.e. impedance, Load Voltage, Load Current, Cavity Dimensional Changes (Microwave components) due to temperature variations and performance of the power supply. The results were analysed and validated with hardware results across a range of actual industrial loads

An observational cross-sectional study to assess knowledge, attitude and practice of resident doctors and nursing professionals regarding pharmacovigilance in a tertiary care teaching hospital in Central India

Background: Adequate knowledge, positive attitude and motivated practice of pharmacovigilance are the building pillars of ADR reporting. This study was conducted to evaluate the knowledge and attitude towards pharmacovigilance and adverse drug reaction reporting among the resident doctors and nursing staff in AIIMS Bhopal, Madhya Pradesh, India.Methods: This cross-sectional questionnaire based study was carried out in a tertiary care centre. The survey was carried out using a pre-validated questionnaire that included 20 questions to evaluate the participant’s knowledge, attitude and practice.Results: Answers to knowledge based questions were given correctly by around 82.6% (95% CI 0.7576 to 0.8794) of resident doctors and 74% (95% CI 0.6033 to 0.8424) nursing professionals. The difference of basic knowledge about pharmacovigilance between resident doctors and nursing professionals was insignificant (p-value is 0.7967). The most common reason for underreporting was unawareness, which was opted by 69% (95% CI 0.6153-0.7617) of resident doctors, while among the 58% (95% CI 0.4422-0.7064) nursing staff, the major factor was non-feasible ADR monitoring system in hospital. The suggestion of conducting training and awareness programme to promote ADR reporting given by resident doctors and nursing staff were 85% (95% CI 0.7872-0.0957) and 80% (95 % CI 0.6677-0.8895) respectively.Conclusions: The participants were well aware of pharmacovigilance and adverse drug reaction reporting. They had expressed the positive attitude towards pharmacovigilance and ADR reporting. But the routine practice of reporting ADRs is lacking. Hence there is need for increasing awareness and building positive attitude and practices among the health care professionals

MAXIMIZATION OF WEAR RATES THROUGH EFFECTIVE CONFIGURATION OF STANDOFF DISTANCE AND HYDRAULIC PARAMETERS IN ULTRASONIC PULSATING WATERJET

A pulsating waterjet is a technological modification of a conventional waterjet that utilizes ultrasonic vibrations to generate a modulated jet, resulting in repetitive fatigue loading of the material. The erosion efficiency of the ultrasonic pulsating waterjet is majorly determined by the hydraulic factors and its interaction with standoff distance. However, the dependency of the wear rates on different hydraulic factors and formulation of an implicit prediction model for determining effective standoff distance is still not present to date. Therefore, in this study, the combined dependency of the supply pressure (20-40 MPa), nozzle diameter (0.3-1.0 mm), and standoff distance (1-121 mm) on wear rates of AW-6060 aluminum alloy are studied. Statistical analysis is used to determine the statistically significant factors and formulate regression equations to determine output responses within the experimental domain. The surface topography and sub-surface microhardness of the eroded grooves were studied. The results show that both the disintegration depth and the material removal increase with an increase in the nozzle diameter and supply pressure. However, the dependency of the output responses on nozzle diameter is statistically more evident than supply pressure and two-way interactions. Cross-sectional images of the grooves showed typical hydrodynamic erosion characteristics in erosion cavities, subsurface voids, and material upheaving. The results of microhardness analysis showed an approximately 15-20% increase in hardness values compared to the untreated samples

Investigation of Hazardous Materials in Firecrackers using LIBS Coupled with a Chemometric Method and FTIR Spectroscopy

This article reports the detection and quantification of toxic constituents in firecrackers using LIBS coupled with PCA and FTIR. Spectral signatures of lethal elements along with other elements and electronic bands of Cyanide, AlO, BaO, and CaO are seen in their LIBS spectra which confirms the presence of inorganic and organic compound in the fireworks. The concentration of each constituent/element is determined using the CF-LIBS method and results are compared with ICP-OES results. The concentration of Al is in adequate amount except S4 (b). Li and Ba are present in all samples with maximum amount in S4 (b) and S3 respectively. Molecular stretching of SO4-, C4 H8 - , CuCl- , CO3 - , and NO3 - are observed in the FTIR spectra of the samples. The combined results of LIBS and FTIR recommends the presence of BaNO3 , LiCO3 , SrCO3 , Al-chip, and charcoal in the firecrackers. To discriminate various firecrackers, PCA of the LIBS data is performed. The results show that S3 and S4 (b) are more harmful as they contain higher concentration the compounds of Al, Ba, Li, Sr i.e BaNO3 , LiCO3 , SrCO3 , (Cu3 As2 O3 Cu(C2 H3 O2 )2 )

An investigation on microstructural features and bonding strength of magnesium-based multifunctional laminated composite developed by friction stir additive manufacturing

Recently, the demand for lightweight multilayered parts in electronics and biomedical felds has been accelerated and shown great interest in understanding the combined efect of multilayered materials. However, these industries are still facing the challenge of developing dissimilar multilayered materials that can be suitable for biomedical applications. In this context, magnesium emerges as a promising biocompatible material used for several biomedical applications. However, the issues related to joining magnesium alloys with other similar materials still need to be solved. Moreover, friction stir additive manufacturing (FSAM) occupies a niche domain for developing or joining biocompatible materials such as magnesium alloys with low weight and high strength. Therefore, the present work highlights the development of a multipurpose three-layered multifunctional laminated composite plate of magnesium-based AZ31B–Zn–Al 1100 through the FSAM route. Micro structural and morphological examinations were carried out by light microscopy and FESEM equipped with EDS analysis and line mapping. Moreover, the grain refnement at the interfaces during the FSAM was also addressed using the electron backscattered difraction (EBSD) study. Further, investigation on mechanical properties such as tensile test with fractography analysis and microhardness variation at the cross-section of the built-up section has been investigated. Furthermore, the cor rosion and tribological analysis was also performed, and a 3D proflometer was used to visualize the corroded and worn-out surfaces. The microstructural results revealed that the average grain size of 6.29 μm at interface AZ31B–Zn and 1.21 μm at interface Zn–Al 1100 occurred, improving the bonding strength and overall properties. The tensile strength has occurred as 171.5 MPa at 15.5% elongation, whereas maximum microhardness is reported as 105 HV at the interface of AZ31B–Zn and 84.6 HV at the interface of Zn–Al 1100. The corrosion rate was calculated as 0.00244 mm/day, and the average coefcients of friction (COF) for both the interfaces, such as AZ31B–Zn and Zn–Al 1100, are 0.309 and 0.212, respectively.Web of Science1281-254653

Study of surface integrity and effect of process parameters in wire electrical discharge turning of Ti-6Al-4V

Wire electrical discharge turning set-up has been developed by modifying the conventional five axes CNC WEDM machine. The main objective of this setup is to achieve cylindrical forms on hard to cut materials. This work focuses on the study of effect of input process parameters like pulse on-time, pulse off time, gap voltage, spindle rotational speed on output responses like surface roughness, material removal rate and wire wear ratio. A mathematical model of responses has been developed using response surface methodology and the optimal value of process parameters has been obtained by desirability function. Surface morphology studies of the machined surface and the worn-out wire has also been elaborated by FE-SEM images. The results show that with an increase in machining parameters value except pulse-on time, all the desired machining outcome decreases. Surface roughness, material removal rate and wire wear ratio have been found in the range of 1.99 μm – 1.37 μm, 7.55 – 13.66 mm3/min and 0.05–0.08, respectively. The formation of thick recast layer over the machined surface has also been discussed. The reduction in wire dimension has been calculated by optical microscopy and its morphology has been discussed by FE-SEM images

Study of surface integrity and effect of process parameters in wire electrical discharge turning of Ti-6Al-4V

267-276Wire electrical discharge turning set-up has been developed by modifying the conventional five axes CNC WEDM machine. The main objective of this setup is to achieve cylindrical forms on hard to cut materials. This work focuses on the study of effect of input process parameters like pulse on-time, pulse off time, gap voltage, spindle rotational speed on output responses like surface roughness, material removal rate and wire wear ratio. A mathematical model of responses has been developed using response surface methodology and the optimal value of process parameters has been obtained by desirability function. Surface morphology studies of the machined surface and the worn-out wire has also been elaborated by FE-SEM images. The results show that with an increase in machining parameters value except pulse-on time, all the desired machining outcome decreases. Surface roughness, material removal rate and wire wear ratio have been found in the range of 1.99 µm – 1.37 µm, 7.55 – 13.66 mm3/min and 0.05–0.08, respectively. The formation of thick recast layer over the machined surface has also been discussed. The reduction in wire dimension has been calculated by optical microscopy and its morphology has been discussed by FE-SEM images