Search results for: varying temperature

Authors: Muhammad Asif ShakoorI, Maogang He, Aamir Shahzad

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Dusty (complex) plasmas contained micro-sized charged dust particles in addition to ions, electrons, and neutrals. It is typically low-temperature plasma and exists in a wide variety of physical systems. In this work, the effects of an external electric field on the diffusion coefficient and share viscosity are investigated through equilibrium molecular dynamics (EMD) simulations in three-dimensional (3D) strongly coupled (SC) dusty plasmas (DPs). The effects of constant and varying normalized electric field strength (E*) have been computed along with different combinations of plasma states on the diffusion of dust particles using EMD simulations. Diffusion coefficient (D) and share viscosity (η) along with varied system sizes, in the limit of varying E* values, is accounted for an appropriate range of plasma coupling (Γ) and screening strength (κ) parameters. At varying E* values, it is revealed that the 3D diffusion coefficient increases with increasing E* and κ; however, it decreases with an increase of Γ but within statistical limits. The share viscosity increases with increasing E*and Γ and decreases with increasing κ. New simulation results are outstanding that the combined effects of electric field and screening strengths give well-matched values of Dandη at low-intermediate to large Γ with varying small-intermediate to large N. The current EMD simulation outcomes under varying electric field strengths are in satisfactory well-matched with previous known simulation data of EMD simulations of the SC-DPs. It has been shown that the present EMD simulation data enlarged the range of E* strength up to 0.1 ≤ E*≤ 1.0 in order to find the linear range of the DPs system and to demonstrate the fundamental nature of electric field linearity of 3D SC-DPs.

Keywords: strongly coupled dusty plasma, diffusion coefficient, share viscosity, molecular dynamics simulation, electric field strength

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Authors: Nursah Kutuk, Sevil Cetinkaya

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Geopolymers are becoming new concrete materials to use alongside cement, which are formed due to reaction between alumino-silicates and oxides with alkaline media. Silicates obtained from natural minerals or industrial wastes are used for geopolymer synthesis. Geopolymers have recently received wide attention because of their advantages over other cementitious material like Portland cement. Some of the advantages are high compressive strength, low environmental impact, chemical and fire resistance and thermal stability. In this study, geopolymers were prepared by using inorganic materials such as kaolinite and calcite. The experiments were carried out by varying the concentration of NaOH as 5, 10, 15 and 20 M, and at cure temperature of 22, 45 and 65 °C. Compressive strengths for each mixes at each cure temperature were measured. Results of the analyses indicated that the compressive strength of geopolymers did not increase steadily with increasing concentration of NaOH, but did increase steadily with increasing cure temperature. We examined the effect Na2SiO3/NaOH weight ratio on the properties of the geopolymers, too. It was seen that Na2SiO3/NaOH weight ratio was also important to prepare geopolymers that can be applied to construction industry.

Keywords: geopolymers, compressive strength, kaolinite, calcite

Procedia PDF Downloads 274

Authors: Manjit Singha, Sandeep Singh Sandhu, A. S. Shahi

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Stellite 6 is cobalt based superalloy used for protective coatings. It is used to improve the wear performance of stainless steel engineering components subjected to harsh environmental conditions. This paper reports the high temperature wear analysis of satellite 6 cladded on AISI 304 L substrate using SMAW process. Bead on plate experiment was carried out by varying current and electrode manipulation techniques to optimize the dilution and hardness. 80 Amp current and weaving technique was found to be the optimum set of parameters for overlaying which were further used for multipass multilayer cladding on two plates of AISI 304 L substrate. On the first plate, seven layers seven passes of stellite 6 was overlaid which was used in as cladded form and the second plate was overlaid with five layers five passes of satellite 6 with further TIG remelting. The wear performance was examined for normal temperature environmental condition and harsh temperature environmental condition. The satellite 6 coating with TIG remelting was found to be better in both the conditions even with lesser metal deposition due to its finer grain structure.

Keywords: surfacing, stellite 6, dilution, overlay, SMAW, high-temperature frictional wear, micro-structure, micro-hardness

Procedia PDF Downloads 261

Authors: Alaa Y. Ali, Natalie P. Holmes, John Holdsworth, Warwick Belcher, Paul Dastoor, Xiaojing Zhou

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Multi-layered graphene has been produced under low temperature chemical vapour deposition (CVD) growth conditions by utilizing an organic solvent and polymer film source. Poly(methylmethacrylate) (PMMA) was dissolved in chlorobenzene solvent and used as a drop-cast film carbon source on a quartz slide. A source temperature (T_source) of 180 °C provided sufficient carbon to grow graphene, as identified by Raman spectroscopy, on clean copper foil catalytic surfaces.  Systematic variation of hydrogen gas (H₂) flow rate from 25 standard cubic centimeters per minute (sccm) to 100 sccm and CVD temperature (T_growth) from 400 to 800 °C, yielded graphene films of varying quality as characterized by Raman spectroscopy. The optimal graphene growth parameters were found to occur with a hydrogen flow rate of 75 sccm sweeping the 180 °C source carbon past the Cu foil at 600 °C for 1 min. The deposition at 600 °C with a H₂ flow rate of 75 sccm yielded a 2D band peak with ~53.4 cm^-1 FWHM and a relative intensity ratio of the G to 2D bands (I_G/I_2D) of 0.21. This recipe fabricated a few layers of good quality graphene.

Keywords: graphene, chemical vapor deposition, carbon source, low temperature growth

Procedia PDF Downloads 136

Authors: Bharat Kumar, Deepak Kumar, Vijay Chaudhry

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Zirconium alloys are used as core components of nuclear reactors due to their high wear resistance, good corrosion properties, and good mechanical stability at high temperatures. Water flows inside the pressure tube through fuel claddings, which produces vibration of these core components and results in the wear of some components. Some components are subjected to the environment of coolant water containing LiOH which results in the corrosion of these components. The present work simulates some of these conditions to determine the failure mechanisms under these conditions and the effect of various parameters on them. Friction and wear experiments were performed varying the surrounding environment (room temperature, high temperature, and water submerged), duration, frequency, and displacement amplitude. Electrochemical corrosion experiments were performed by varying the concentration of LiOH in water. The worn and corroded surfaces were analyzed using scanning electron microscopy (SEM) to analyze the wear and corrosion mechanism and energy dispersive x-ray spectroscopy (EDS) and Raman spectroscopy to analyze the tribo-oxide layer formed during the wear and oxide layer formed during the corrosion. Wear increases with frequency and amplitude, and corrosion increases with LiOH concentration in water.

Keywords: zirconium alloys, wear, oxide layer, corrosion, EIS, linear polarization

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Authors: Csaba Tóth, Éva Lakatos, László Pethő, Seoyoung Cho

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The temperature effect on asphalt pavement structure is a crucial factor at the design stage. In this paper, by applying the German guidelines for temperature along the asphalt depth is estimated. The aim is to consider temperature profiles in different seasons in numerical modelling. The model is built with an elastic and isotropic solid element with 19 subdivisions of asphalt layers to reflect the temperature variation. Comparison with the simple three-layer pavement system (asphalt layers, base, and subgrade layers) will be followed to see the difference in result without temperature variation along with the depth. Finally, the fatigue life calculation was checked to prove the validity of the methodology of considering the temperature in the numerical modelling.

Keywords: temperature profile, flexible pavement modeling, finite element method, temperature modeling

Procedia PDF Downloads 239

Authors: Ahmet Y. Arabul, Ibrahim Senol, Fatma Keskin Arabul, Mustafa G. Aydeniz, Yasemin Oner, Gokhan Kalkan

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In the standards of IEC 60076-2 and IEC 60076-7, three different hot-spot temperature estimation methods are suggested. In this study, the algorithms which used in hot-spot temperature calculations are analyzed by comparing the algorithms with the results of an experimental set-up made by a Transformer Monitoring System (TMS) in use. In tested system, TMS uses only top oil temperature and load ratio for hot-spot temperature calculation. And also, it uses some constants from standards which are on agreed statements tables. During the tests, it came out that hot-spot temperature calculation method is just making a simple calculation and not uses significant all other variables that could affect the hot-spot temperature.

Keywords: Hot-spot temperature, monitoring system, power transformer, smart grid

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Authors: T. Bielewicz, S. Dogan, C. Klinke

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Two-dimensional, solution-processable semiconductor materials are interesting for low-cost electronic applications [1]. We demonstrate the synthesis of lead sulfide nanosheets and how their size, shape and height can be tuned by varying concentrations of pre-cursors, ligands and by varying the reaction temperature. Especially, the charge carrier confinement in the nanosheets’ height adjustable from 2 to 20 nm has a decisive impact on their electronic properties. This is demonstrated by their use as conduction channel in a field effect transistor [2]. Recently we also showed that especially thin nanosheets show a high carrier multiplication (CM) efficiency [3] which could make them, through the confinement induced band gap and high photoconductivity, very attractive for application in photovoltaic devices. We are already able to manufacture photovoltaic devices out of single nanosheets which show promising results.

Keywords: physical sciences, chemistry, materials, chemistry, colloids, physics, condensed-matter physics, semiconductors, two-dimensional materials

Procedia PDF Downloads 275

Authors: W. Widhiada, D. N. K. P. Negara, P. A. Suryawan

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The technological advances in the field of health to be very important, especially on the safety of the baby. In this case a lot of premature infants death caused by poorly managed health facilities. Mostly the death of premature baby caused by bacteria since the temperature around the baby is not normal. Related to this, the incubator equipment needs to be important, especially in how to control the temperature in incubator. On/Off controls is used to regulate the temperature distribution in the incubator so that the desired temperature is 36 °C to stay awake and stable. The authors have been observed and analyzed the data to determine the temperature distribution in the incubator using program of MATLAB/Simulink. The output temperature distribution is obtained at 36 °C in 400 seconds using an Arduino AT 2560. This incubator is able to maintain an ambient temperature and maintain the baby's body temperature within normal limits and keep the moisture in the air in accordance with the limit values required in infant incubator.

Keywords: on/off control, distribution temperature, Arduino AT 2560, baby incubator

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Authors: Chanjuan Sun, Shijie Hong, Jialing Zhang, Yuchao Guo, Zhijun Zou, Chen Huang

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Background: Studies on associations between air temperature and childhood respiratory diseases are lack in China. Objectives: We aim to analyze the relationship between air temperature and childhood respiratory diseases. Methods: We conducted the on-site inspection into 454 residences and questionnaires survey. Indoor air temperature were from field inspection and outdoor air temperature were from website. Multiple logistic regression analyses were used to investigate the associations. Results: Indoor extreme hot air temperature was positively correlated with duration of a common cold (>=2 weeks), and outdoor extreme hot air temperature was also positively related with pneumonia among children. Indoor and outdoor extreme cold air temperature was a risk factor for rhinitis among children. The biggest indoor air temperature difference (indoor maximum air temperature minus indoor minimum air temperature) (Imax minus Imin) (the 4th quartile, >4 oC) and outdoor air temperature difference (outdoor maximum air temperature minus outdoor minimum air temperature) (Omax minus Omin) (the 4th quartile, >8oC) were positively related to pneumonia among children. Meanwhile, indoor air temperature difference (Imax minus Imin) (the 4th quartile, >4 oC) was positively correlated with diagnosed asthma among children. Air temperature difference between indoor and outdoor was negatively related with the most childhood respiratory diseases. This may be partly related to the avoidance behavior. Conclusions: Improper air temperature may affect the respiratory diseases among children.

Keywords: air temperature, extreme air temperature, air temperature difference, respiratory diseases, children

Procedia PDF Downloads 139

Authors: Ahmad Javid Zia, Abdulkerim Ilgun, Suleyman Kamil Akin, Mustafa Altin

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Curing conditions that help concrete, which is one of the most widely used building materials in construction sector, gain strength today is one the important issues. In this study the varying concrete strength depending on water temperature at curing stage is investigated through tests at laboratory. At laboratory the curing conditions has been determined according to both TS EN 12390-2 and regular construction site while performing the experiments on specimens. Five samples have been taken from concrete and cured under five different curing conditions and the compressive strength results of concrete specimens have been compared. One of these five curing conditions has been prepared accordance with TS EN 12390-2, the sample cured at 20 ± 2 ˚C and accepted as reference samples. Two of the remaining sample groups have been cured in 5 ± 2 ˚C and 15 ± 2 ˚C and the other two have been cured outside of the laboratory. One group of the samples which have been cured outside has been watered twice a day and the other group has not been watered at all. The experiments have been carried out on 150x150x150 mm cube samples of C20 (200 kg/cm2) and C25 (250 kg/cm2). 7 and 28 days compressive strength of specimens have been measured and compared.

Keywords: concrete curing, curing conditions, water temperature, concrete compressive strength

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Authors: Ali Reza Tahavvor, Saeed Hosseini, Afshin Karimzadeh Fard

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In this paper the effect of wall waviness of side walls in a two-dimensional wavy enclosure is numerically investigated. Two vertical wavy walls and straight top wall are kept isothermal and the bottom wall temperature is higher and spatially varying with cosinusoidal temperature distribution. A computational code based on Finite-volume approach is used to solve governing equations and SIMPLE method is used for pressure velocity coupling. Test is performed for several different numbers of undulations. The Prandtl number was kept constant and the Ra number denotes that the flow is laminar. Temperature and velocity fields are determined. Therefore, according to the obtained results a correlation is proposed for average Nusselt number as a function of number of side wall waves. The results indicate that the Nusselt number is highly affected by number of waves and increasing it decreases the wavy walls Nusselt number; although the Nusselt number is not highly affected by surface waviness when the number of undulations is below one.

Keywords: cavity, natural convection, Nusselt number, wavy wall

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Authors: Gyeong-Suk Jo, Soo-Hyun Ji, You-Seok Lee, Jeong-Hwa Kang

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To develop an flavor oil using Sarcodon aspratus (Sarcodon aspratus Berk. S. Ito), infiltration extraction method was used to add dried mushroom flavor of Sarcodon aspratus to base olive oil. Edible base oil used during infiltration extraction was pressed olive oil, and infiltration extraction was done while varying extraction temperature to 20, 30, 40 and 50(℃) extraction time to 24 hours, 48 hours and 72 hours. Amount of Sarcodon aspratus added to base oil was 20% compared to 100% of base oil. Production yield of Sarcodon aspratus flavor oil decreased with increasing extraction frequency. Aroma intensity was 2195~2447 (A.U./1㎖), and it increased with increasing extraction temperature and extraction time. Chromaticity of Sarcodon aspratus flavor oil was bright pale yellow with pH of 4.5, sugar content of 71~72 (°Brix), and highest average turbidity of 16.74 (Haze %) shown by the 40℃ group. In the aromatic evaluation, increasing extraction temperature and extraction time resulted in increase of cheese aroma, savory sweet aroma and beef jerky aroma, as well as spicy taste comprised of slight bitter taste, savory taste and slight acrid taste, to make aromatic oil with unique flavor.

Keywords: Flavor Characteristics, Flavor Oil, Infiltration extraction method, mushroom, Sarcodon aspratus (Sarcodon aspratus Berk. S. Ito)

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Authors: Morteza Shayan Arani, Mohammadamin Esmailzadehazimi, Mohammadreza Moeini, Mohammad Toorani, Aouni A. Lakis

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This paper investigates the nonlinear response of thin, incompressible, hyperelastic cylindrical shells in the presence of a time-varying temperature field while considering initial geometric imperfections. The governing equations of motion are derived using an improved Donnell's shallow shell theory. The hyperelastic material is modeled using the Mooney-Rivlin model with two parameters, incorporating temperature-dependent terms. The Lagrangian method is applied to obtain the equation of motion. The resulting governing equation is addressed through the Lindstedt-Poincaré and Multiple Scale methods. The linear and nonlinear models presented in this study are verified against existing open literature, demonstrating the accuracy and reliability of the presented model. The study focuses on understanding the influence of temperature variations and geometrical imperfections on the natural frequency and amplitude-frequency response of the systems. Notably, the investigation reveals the coexistence of hardening and softening peaks in the amplitude-frequency response, which vary in magnitude depending on these parameters. Additionally, resonance peaks exhibit changes as a result of temperature and geometric imperfections.

Keywords: hyperelastic material, cylindrical shell, geometrical nonlinearity, material naolinearity, initial geometric imperfection, temperature gradient, hardening and softening

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Authors: Sameh Frikha, Mohamed Salah Abid

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We investigate the performance of an integrated cascade (IC) refrigeration system which uses environment friendly zeotropic mixtures. Computational calculation has been carried out by varying pressure level at the evaporator and the condenser of the system. Effects of mass flow rate of the refrigerant on the coefficient of performance (COP) are presented. We show that the integrated cascade system produces ultra-low temperatures in the evaporator by using environment friendly zeotropic mixture.

Keywords: coefficient of performance, environment friendly zeotropic mixture, integrated cascade, ultra low temperature, vapor compression refrigeration cycles

Procedia PDF Downloads 235

Authors: Gajanan Bhat, Vincent Kandagor, Daniel Prather, Ramesh Bhave

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Polyetherimide (PEI), an engineering plastic with very high glass transition temperature and excellent chemical and thermal stability, has been processed into a controlled porosity filter media of varying pore size, performance, and surface characteristics. A special grade of the PEI was processed by melt blowing to produce microfiber nonwovens suitable as filter media. The resulting microfiber webs were characterized to evaluate their structure and properties. The fiber webs were further modified by hot pressing, a post processing technique, which reduces the pore size in order to improve the barrier properties of the resulting membranes. This ongoing research has shown that PEI can be a good candidate for filter media requiring high temperature and chemical resistance with good mechanical properties. Also, by selecting the appropriate processing conditions, it is possible to achieve desired filtration performance from this engineering plastic.

Keywords: nonwovens, melt blowing, polyehterimide, filter media, microfibers

Procedia PDF Downloads 288

Authors: Byung hyun Bae

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In power transformer, leakage magnetic flux generate temperature rise of inner steel plate. Sometimes, this temperature rise can be serious problem. If temperature of steel plate is over critical point, harmful gas will be generated in the tank. And this gas can be a reason of fire, explosion and life decrease. So, temperature rise forecasting of steel plate is very important at the design stage of power transformer. To improve accuracy of forecasting of temperature rise, comparison between simulation and experiment achieved in this paper.

Keywords: power transformer, steel plate, temperature rise, experiment, simulation

Procedia PDF Downloads 464

Authors: Mohamed Hafid, Marcel Lacroix

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This study presents a simple inverse heat transfer procedure for predicting the wall erosion and the time-varying thickness of the protective bank that covers the inside surface of the refractory brick wall of a melting furnace. The direct problem is solved by using the Finite-Volume model. The melting/solidification process is modeled using the enthalpy method. The inverse procedure rests on the Levenberg-Marquardt method combined with the Broyden method. The effect of the location of the temperature sensors and of the measurement noise on the inverse predictions is investigated. Recommendations are made concerning the location of the temperature sensor.

Keywords: melting furnace, inverse heat transfer, enthalpy method, levenberg–marquardt method

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Authors: Parveen Kumar, J. K. Juneja, Chandra Prakash, K. K. Raina

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A series of polycrystalline ferroelectric ceramics with compositional formula Ba0.80-xSmxPb0.20Ti0.90Zr0.10O3 with x varying from 0 to 0.01 in the steps of 0.0025 has been prepared by solid state reaction method. The dielectric constant and tangent loss was measured as a function of frequency from 100Hz to 1MHz at different temperatures (200-500oC). The electrical behavior was then investigated using complex impedance spectroscopy (CIS) technique. From the CIS study, it has been found that there is a contribution of both grain and grain boundary in the electrical behavior of such ceramics. Grain and grain boundary resistivity and capacitance were calculated at different temperature using CIS technique. The present paper is about the discussion of grain and grain boundary contribution towards the electrical properties of Sm modified BaTiO3 based ceramics at high temperature.

Keywords: grain, grain boundary, impedance, dielectric

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Authors: Akhtar Rasool, Tasneem Zahra Rizvi

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In this study, a series of the cadmium sulphide quantum dots/polyaniline nanocomposites with varying compositions were prepared by in-situ polymerization technique and were characterized using X-ray diffraction and Fourier transform infrared spectroscopy. The surface morphology was studied by scanning electron microscopy. UV-Visible spectroscopy was used to find out the energy band gap of the nanoparticles and the nanocomposites. Temperature dependence of DC electrical conductivity and temperature and frequency dependence of AC conductivity were investigated to study the charge transport mechanism in the nanocomposites. DC conductivity was found to be a typical for a semiconducting behavior following Mott’s 1D variable range hoping model. The frequency dependent AC conductivity followed the universal power law.

Keywords: conducting polymers, nanocomposites, polyaniline composites, quantum dots

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Authors: Reza Eslami-Farsani, Mohammad Alipour

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The effect of deformation on the semisolid microstructure and degree of globularity of Al–15%Mg₂Si composite produced by the strain induced melt activation (SIMA) process was studied. Deformation of 25% was used. After deformation, the samples were heated to a temperature above the solidus and below the liquidus point and maintained in the isothermal conditions at three different temperatures (560, 580 and 595 °C) for varying time (5, 10, 20 and 40 min). The microstructural study was carried out on the alloy by the use of optical microscopy. It was observed that strain induced deformation and subsequently melt activation has caused the globular morphology of Mg₂Si particles. The results showed that for the desired microstructures of the alloy during SIMA process, the optimum temperature and time are 595 °C and 40 min respectively.

Keywords: deformation, semisolid, SIMA, Mg₂Si phase, modification

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Authors: H. Yousefnia, A. Golabi Dezfuli, S. Zolghadri, M. Hosntalab

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Peptide receptor radionuclide therapy is nowadays used for the treatment of various abnormalities with somatostatin receptors. In this study, 166Ho-DOTATOC was prepared and the best conditions for its radiolabeling was obtained. For this purpose, a certain of DOTATOC was added to a vial containing 166Ho. various experiments by varying ligand concentration, pH, temperature and time were performed to determine the best conditions. Radiochemical purity of the complex was assessed by instant thin layer chromatography method utilizing 0.9% NaCl as the mobile phase. 166Ho-DOTATOC was prepared with radiochemical purity of higher than 95% at the optimized condition (pH=4, temperature: 95° C, time:30 min). In 0.9% NaCl, free Ho cation was developed at Rf of 0.8 while the complex was remained at the front of the paper.

Keywords: Ho-166, neuroendocrine, octreotide, quality control

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Authors: Yemane Hailu Fissuh, Zhongzhan Zhang

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An estimating equation technique is an alternative method of the widely used maximum likelihood methods, which enables us to ease some complexity due to the complex characteristics of time-varying covariates. In the situations, when both the time-varying covariates and left-truncation are considered in the model, the maximum likelihood estimation procedures become much more burdensome and complex. To ease the complexity, in this study, the modified estimating equations those have been given high attention and considerations in many researchers under semiparametric transformation model was proposed. The purpose of this article was to develop the modified estimating equation under flexible and general class of semiparametric transformation models for left-truncated and right censored survival data with time-varying covariates. Besides the commonly applied Cox proportional hazards model, such kind of problems can be also analyzed with a general class of semiparametric transformation models to estimate the effect of treatment given possibly time-varying covariates on the survival time. The consistency and asymptotic properties of the estimators were intuitively derived via the expectation-maximization (EM) algorithm. The characteristics of the estimators in the finite sample performance for the proposed model were illustrated via simulation studies and Stanford heart transplant real data examples. To sum up the study, the bias for covariates has been adjusted by estimating density function for the truncation time variable. Then the effect of possibly time-varying covariates was evaluated in some special semiparametric transformation models.

Keywords: EM algorithm, estimating equation, semiparametric transformation models, time-to-event outcomes, time varying covariate

Procedia PDF Downloads 125

Authors: Young-Min Kang

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M-type Sr-hexaferrites (SrFe12O19) is one of the most utilized materials in permanent magnets due to their low price, outstanding chemical stability, and appropriate hard magnetic properties. For a M-type Sr-hexaferrite with a saturation magnetization (MS) of ~74.0 emu/g the practical limits of remanent flux density (Br) and maximum energy product (BH) max are ~4.6 kG and ~5.3 MGOe. Meanwhile, W-type hexaferrite (SrFe18O27) with higher MS ~81emu/g can be a good candidate for the development of enhanced ferrite magnet. However the W-type hexaferrite is stable at the temperature over 1350 ºC in air, and thus it is hard to control grain size and the coercivity. We report here high-MS M-W composite hexaferrites synthesized at 1250 ºC in air by doping Ca, Co, Mn, and Zn into the hexaferrite structures. The hexaferrites samples of stoichiometric SrFe12O19 (SrM) and Ca-Co-Mn-Zn doped hexaferrite (Sr0.7Ca0.3Fen-0.6Co0.2Mn0.2Zn0.2Oa) were prepared by conventional solid state reaction process with varying Fe content (10 ≤ n ≤ 17). Analysis by x-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were performed for phase identification and microstructural observation respectively. Magnetic hysteresis curves were measured using vibrating sample magnetometer (VSM) at room temperature (300 K). Single M-type phase could be obtained in the non-doped SrM sample after calcinations at the range of 1200 ºC ~ 1300 ºC, showing MS in the range of 72 ~ 72.6 emu/g. The Ca-Co-Mn-Zn doped SrM with Fe content, 10 ≤ n ≤ 13, showed both M and W-phases peaks in the XRD after respective calcinations at 1250 ºC. The sample with n=13 showed the MS of 70.7, 75.3, 78.0 emu/g, respectively, after calcination at 1200, 1250, 1300 ºC. The high MS over that of non-doped SrM (~72 emu/g) is attributed to the volume portion of W-phase. It is also revealed that the high MS W-phase could not formed if only one of the Ca, Co, Zn is missed in the substitution. These elements are critical to form the W-phase at the calcinations temperature of 1250 ºC, which is 100 ºC lower than the calcinations temperature for non-doped Sr-hexaferrites.

Keywords: M-type hexaferrite, W-type hexaferrite, saturation magnetization, low-temperature synthesis

Procedia PDF Downloads 143

Authors: Vinit Srivastava, Abhay Singh Thakur, Shivam Dubey, Rahul Vaish, Bharat Singh Rajpurohit

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This study examines the problem of students' poor comprehension of the thermal dependence of resistance by investigating this idea using an evidence-based inquiry approach. It suggests a practical exercise to improve secondary school students' comprehension of how materials' resistance to temperature changes. The suggested exercise uses an Arduino and Peltier device to test the resistance of aluminum and graphite at various temperatures. The study attempts to close the knowledge gap between the theoretical and practical facets of the subject, which students frequently find difficult to grasp. With the help of a variety of resistors made of various materials and pencils of varying grades, the Arduino experiment investigates the resistance of a metallic conductor (aluminum) and a semiconductor (graphite) at various temperatures. The purpose of the research is to clarify for students the relationship between temperature and resistance and to emphasize the importance of resistor material choice and measurement methods in obtaining precise and stable resistance values over dynamic temperature variations. The findings show that while the resistance of graphite decreases with temperature, the resistance of metallic conductors rises with temperature. The results also show that as softer lead pencils or pencils of a lower quality are used, the resistance values of the resistors drop. In addition, resistors showed greater stability at lower temperatures when their temperature coefficients of resistance (TCR) were smaller. Overall, the results of this article show that the suggested experiment is a useful and practical method for teaching students about resistance's relationship to temperature. It emphasizes how crucial it is to take into account the resistor material selection and the resistance measurement technique when designing and picking out resistors for various uses. The results of the study are anticipated to guide the creation of more efficient teaching methods to close the gap between science education's theoretical and practical components.

Keywords: electrical resistance, temperature dependence, science education, inquiry-based activity, resistor stability

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Authors: Selam M. Tefera

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Soil constitutes a crucial component of rural and urban environments. This fact is making role of heavy and trace elements in the soil system an issue of global concern. Heavy metals constitute an ill-defined group of inorganic chemical hazards, whose main source is anthropogenic activities mainly related to fabrications. This accumulation of heavy metals soils can prove toxic to the environment. The application of biochar to soil is one way of immobilizing these contaminants through sorption by exploiting the high surface area of this material among its other essential properties. This research examined the ability of sugar cane straw, an organic waste material from sugar farm, derived biochar and ash to remediate soil contaminated with heavy metals mainly Chromium and Zinc from the effluent of electroplating industry. Biochar was produced by varying the temperature from 300 °C to 500 °C and ash at 700 °C. The highest yield (50%) was obtained at the lowest temperature (300 °C). The proximate analysis showed ash content of 42.8%, ultimate analysis with carbon content of 67.18%, the Hydrogen to Carbon ratio of 0.54 and the results from FTIR analysis disclosed the organic nature of biochar. Methylene blue absorption indicated its fine surface area and pore structure, which increases with severity of temperature. Biochar was mixed with soil with at a ration varying from 4% w/w to 10% w/w of soil, and the response variables were determined at a time interval of 150 days, 180 days, and 210 days. As for ash (10% w/w), the characterization was performed at incubation time of 210 days. The results of pH indicated that biochar (9.24) had a notable liming capacity of acidic soil (4.8) by increasing it to 6.89 whereas ash increased it to 7.5. The immobilization capacity of biochar was found to effected mostly by the highest production temperature (500 °C), which was 75.5% for chromium and 80.5% for nickel. In addition, ash was shown to possess an outstanding immobilization capacity of 95.5% and 90.5% for Chromium and Nickel, respectively. All in all, the results from these methods showed that biochar produced from this specific biomass possesses the typical functional groups that enable it to store carbon, the appropriate pH that could remediate acidic soil, a fine amount of macro and micro nutrients that would aid plant growth.

Keywords: biochar, biomass, heavy metal immobalization, soil remediation

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Authors: I. Grigoraviciute-Puroniene, K. Tsuru, E. Garskaite, Z. Stankeviciute, A. Beganskiene, K. Ishikawa, A. Kareiva

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Tricalcium phosphate (β-Ca₃(PO₄)₂, β-TCP) powders were synthesized using wet polymeric precipitation method for the first time to our best knowledge. The results of X-ray diffraction analysis showed the formation of almost single a Ca-deficient hydroxyapatite (CDHA) phase of a poor crystallinity already at room temperature. With continuously increasing the calcination temperature up to 800 °C, the crystalline β-TCP was obtained as the main phase. It was demonstrated that infrared spectroscopy is very effective method to characterize the formation of β-TCP. The SEM results showed that β-TCP solids were homogeneous having a small particle size distribution. The β-TCP powders consisted of spherical particles varying in size from 100 to 300 nm. Fabricated β-TCP specimens were placed to the bones of the rats and maintained for 1-2 months.

Keywords: Tricalcium phosphate (β-Ca3(PO4)2, bone regeneration, wet chemical processing, polymeric precipitation

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Authors: Karima Bourenane, Aissa Keffous

Abstract:

In this paper, we present an experimental method on the etching reaction of p-type 6H-SiC, etching that was carried out in HF/K₂Cr₂O₇ solutions. The morphology of the etched surface was examined with varying K₂Cr₂O₇ concentrations, etching time and temperature solution. The surfaces of the etched samples were analyzed using Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and Photoluminescence. The surface morphology of samples etched in HF/K₂Cr₂O₇ is shown to depend on the solution composition and bath temperature. The investigation of the HF/K₂Cr₂O₇ solutions on 6H-SiC surface shows that as K₂Cr₂O₇ concentration increases, the etch rate increases to reach a maximum value at about 0.75 M and then decreases. Similar behavior has been observed when the temperature of the solution is increased. The maximum etch rate is found for 80 °C. Taking into account the result, a polishing etching solution of 6H-SiC has been developed. In addition, the result is very interesting when, to date, no chemical polishing solution has been developed on silicon carbide (SiC). Finally, we have proposed a dissolution mechanism of the silicon carbide in HF/K₂Cr₂O₇ solutions.

Keywords: silicon carbide, dissolution, Chemical etching, mechanism

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Authors: Jayashree Das, V. V. Srinivasu , D. K. Mishra, A. Maity

Abstract:

Owing to the important potential applications over decades, transition metal (TM: Mn, Fe, Ni, Cu, Cr, V etc.) doped ZnO-based diluted magnetic semiconductors (DMS) always attract research attention for more and newer investigations. One of the interesting aspects of these materials is to study and understand the magnetic property at room temperature properly, which is very crucial to select a material for any related application. In this regard, Electron spin resonance (ESR) study has been proven to be a powerful technique to investigate the spin dynamics of electrons inside the system, which are responsible for the magnetic behaviour of any system. ESR as well as the Raman and Photoluminescence spectroscopy studies are also helpful to study the defects present or created inside the system in the form of oxygen vacancy or cluster instrumental in determining the room temperature ferromagnetic property of transition metal doped ZnO system, which can be controlled through varying dopant concentration, appropriate synthesis technique and sintering of the samples. For our investigation, we synthesised Cu-doped ZnO nanocrystalline samples with composition Zn1-xCux ( 0.005< x < 0.05) by pyrophoric method and sintered at a low temperature of 650 0C. The microwave absorption is studied by the Electron Spin Resonance (ESR) of X-band (9.46 GHz) at room temperature. Systematic analysis of the obtained ESR spectra reveals that all the compositions of Cu-doped ZnO samples exhibit resonance signals of appreciable line widths and g value ~ 2.2, typical characteristic of ferromagnetism in the sample. Raman scattering and the photoluminescence study performed on the samples clearly indicated the presence of pronounced defect related peaks in the respective spectra. Cu doping in ZnO with varying concentration also observed to affect the optical band gap and the respective absorption edges in the UV-Vis spectra. FTIR spectroscopy reveals the Cu doping effect on the stretching bonds of ZnO. To probe into the structural and morphological changes incurred by Cu doping, we have performed XRD, SEM and EDX study, which confirms adequate Cu substitution without any significant impurity phase formation or lattice disorder. With proper explanation, we attempt to correlate the results observed for the structural optical and magnetic behaviour of the Cu-doped ZnO samples. We also claim that our result can be instrumental for appropriate applications of transition metal doped ZnO based DMS in the field of optoelectronics and Spintronics.

Keywords: diluted magnetic semiconductors, electron spin resonance, raman scattering, spintronics.

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Authors: Masoumeh Moghbel

Abstract:

Nowadays, carbon dioxide which is produced by human activities is considered as the main effective factor in the global warming occurrence. Regarding to the role of CO2 and its ability in trapping the heat, the main objective of this research is study the effect of atmospheric CO2 (which is recorded in Manaloa) on variations of temperature parameters (daily mean temperature, minimum temperature and maximum temperature) in 5 meteorological stations in Iran which were selected according to the latitude and altitude in 40 years statistical period. Firstly, the trend of temperature parameters was studied by Regression and none-graphical Man-Kendal methods. Then, relation between temperature variations and CO2 were studied by Correlation technique. Also, the impact of CO2 amount on temperature in different atmospheric levels (850 and 500 hpa) was analyzed. The results illustrated that correlation coefficient between temperature variations and CO2 in low latitudes and high altitudes is more significant rather than other regions. it is important to note that altitude as the one of the main geographic factor has limitation in affecting the temperature variations, so that correlation coefficient between these two parameters in 850 hpa (r=0.86) is more significant than 500 hpa (r = 0.62).

Keywords: altitude, atmospheric carbon dioxide, latitude, temperature variations

Procedia PDF Downloads 377