Single step thermal treatment synthesis and characterization of lithium tetraborate nanophosphor

This study includes the synthesis of nano-sized lithium tetraborate by an innovative single step thermal treatment method and characterization of the products. The heating temperature for the synthesis was varied between 200 and 850 °C with the retention time of 2 h. Polyvinyl pyrrolidone (PVP) with different concentrations was used as surfactant. Characterization of the samples was achieved by thermogravimetric analysis (TGA), derivative thermogravimetry analysis (DTG), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) techniques and UV–vis spectroscopy. Thermal analysis of initial solution allowed the optimization of the heat treatment program and showed that the thermal stability of samples is started at 460 °C. FT-IR, XRD and TEM results proved the formation of pure nano-crystalline lithium tetraborate at temperature between 460 and 750 °C. Furthermore, the band gap investigation was performed using UV–vis spectra in the presence of different concentrations of PVP and in variety of calcination temperatures. The estimated optical bandgap was found to be between 5.2 and 6.2 eV

Structural, optical and electrical properties of ZnS nanoparticles affecting by organic coating

In this study the influence of the organic polymeric coating and its concentration on the structural, optical and electrical properties of ZnS nanocrystals has been investigated. In this matter, PVP-capped ZnS nanocrystals were prepared by a simple, rapid and energy efficient microwave method. The XRD results confirmed the formation of single phase cubic nano crystalline structure. TEM images showed the formation of well isolated spherical nanoparticles with the average size of less than 5.5 nm. The presence of tensile strain in all samples was determined from Williamson-Hall analysis. The elemental compositions of Zn, S and O were quantitatively obtained from EDX analysis, where the FT-IR spectra confirmed coordination with O atoms of PVP. The band gap and absorption edge shift was determined using UV–visible spectroscopy. The PL spectra of the PVP-capped ZnS nanoparticles appeared broadened from 370 to 500 nm due to the presence of multiple emission bands attribute to the sulfur and zinc vacancies or compounded effect of PVP. The electrical property study of samples indicated the conductivity enhancement from 2.981×10-6 to 7.014 ×10-6 S/m by increasing PVP concentration. Increasing of dielectric constant and decrease in the peak value of tan δ by raising the PVP concentration were observed

Numerical study of side gate junction-less transistor in on state

Side gate p-type Junctionless Silicon transistor is fabricated by AFM nanolithography on low-doped (105 cm-3) SOI wafer. In this work, the simulation characteristic of the device using TCAD Sentaurus in on state will be studied. The results show that the device is the pinch off transistor, works in on state for zero gate voltage in depletion mode. Negative gate voltage drives the device into on state, but unable to make significant effect on drain current as accmulation mode. Simulation results for valence band energy, electric field and hole density are investigated along the active regions. The influence of the electric field due to the applied voltages of V DS and V G on charge distribution is much more when the device operates at the saturation region. The hole quasi-Fermi level has a positive slope showing the current flows from source to drain

Atomic force microscope base nanolithography for reproducible micro and nanofabrication

Atomic force microscopy nanolithography (AFM) is a strong fabrication method for micro and nano structure due to its high spatial resolution and positioning abilities. Mixing AFM nanolithography with advantage of silicon-on-insulator (SOI) technology provides the opportunity to achieve more reliable Si nanostructures. In this letter, we try to investigate the reproducibility of AFM base nanolithography for fabrication of the micro/nano structures. In this matter local anodic oxidation (LAO) procedure applied to pattern a silicon nanostructure on p-type (1015 cm-3) SOI using AFM base nanolithography. Then chemical etching is applied, as potassium hydroxide (saturated with isopropyl alcohol) and hydrofluoric etching for removing of Si and oxide layer, respectively. All parameters contributed in fabrication process were optimized and the final results revealed a good potential for using AFM base nanolithography in order to get a reproducible method of fabrication

Synthesis and evaluation of undoped and silver and copper doped lithium tetraborate nanoparticles as thermoluminescence dosimeter

Tissue equivalent thermoluminescence dosimeters (TLDs) are commonly used for monitoring dose of ionizing radiation as personal or medical radiation dosimeters. The commercially available macro-scale lithium tetra borates (LTB) have several drawbacks such as poor Thermoluminescent (TL) intensity, limited dose linearity, losses information with time (fading) and energy dependence,which might be improved by using nano-scale activated LTB, the main goal of this study. LTB is the most popular material for radiation dosimetry because of its effective atomic number (Zeff = 7.4) that close with the Zeff of human tissue (7.42). Furthermore, LTB is almost stable chemical compound and can be easily doped with TL sensitizers. In line with this development the objectives of this work were to synthesize and to investigate the structural characteristics and TL properties of undoped LTB and silver and copper doped LTB (LTB-Ag and LTB-Cu) nanoparticles for dosimetric applications. The LTB nanoparticles were synthesized by using innovative single step thermal treatment method. Subsequently, the samples were investigated for thermal stability and phase transition using thermal gravimetric analysis (TGA), derivative thermogravimetry analysis (DTG), and differential scanning calorimetry (DSC). The TGA, DTG, and DSC results showed the triple phases of mass loss were observed. Fourier transform infrared spectroscopy (FT-IR) was used to monitor the formation nanoparticles in the range of 200-4000 cm-1. The samples were subjected to different calcination temperatures and found 650, 700, and 750 oC were the principal calcination temperatures based on the X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images. To study the effect of PVP capping agent for regulating nanoparticles’ agglomeration,0.009, 0.018, and 0.027 mol of PVP concentrations were used. The narrowest particle size and size distributions were reached at 0.027 mol of PVP for LTB and LTB-Cu nanoparticles and at 0.018 mol of PVP for LTB-Ag nanoparticles. The average particle sizes determined from TEM size distributions were 3.34,4.61, and 4.56 nm for LTB, LTB-Cu and LTB-Ag nanoparticles, respectively at calcination temperature of 750 oC. The UV-visible spectroscopy (UV-Vis) was used to determine the optical bandgap of the synthesized nanoparticles. To investigate the TL property of the synthesized nanoparticles, dose response,energy storage ability, and energy dependence of nanophosphors were studied from glow curve of dose response at a variety of dose ranges of 0.005, 0.01, 0.1,0.5, 1, 10, 100, and 150 Gy. The current nano-scale doped and undoped LTB dosimeters have good physical properties and TL response that they can be produced easily by single step thermal treatment method at effective cost and without by-product effluents

Gammaların ve (n, p) reaksiyonunun nem ve kükürt analizinde kullanılması

Bu tezin, veri tabanı üzerinden yayınlanma izni bulunmamaktadır. Yayınlanma izni olmayan tezlerin basılı kopyalarına Üniversite kütüphaneniz aracılığıyla (TÜBESS üzerinden) erişebilirsiniz.SUMMARY Impurity analysis in matter now a days has been carried out by the chemical methods but the time of analysis is not very economical and the sensitivity is not as good as the sensitivity of the nuclear methods. In this method matter determination has been done by investigation of the vapour resulting from the burrning raw material. On the other hand nuclear methods are more reliable and perforable since the determination could be performed without destroying the raw material. The results of the interaction of y 's with matter when compared with the results of the other methods are simpler, straight forward and correct In this study, double y - source method, the spectra containing the characteristics of the elements in the material concerned which are observed in the multi - channel analyzer as the result of the interaction of the t"s with matter have been used in the determination of the material analysis. The net peak area measured by the gamma spectrometer from the spectra obtained as the result of the reaction of the gammas emitted from the Cs - 137 and Am - 241 sources with the samples, have been substituted in the relations concerned and moisture determination have been performed. In this study, energy interval has been selected as 60 KeV and 662 KeV in accordance with our objective. For this purpose 6 standard y - sources have been used. Soma Lignites after drying in the oven at 105 °C has been located in front of the y- source with different thicknesses and irradiated for a period of 10800 sees, and the spectra given have been analyzed with the help of multi - channel analyzer. As a result, an amount of 10,1 1 % moisture has been calculated. 68Using the surface barrier detector wich is a type of semi - conductor detectors, sulphur analysis has also been done in the coal from Muğla Yatağan Eskihisar. In this method a certain amount of coal has been irradiated for a long period of time with the Cf - 252 neutrons and then sulphur is determined with the P - spectrometer. 69ÖZET Günümüzde madde içinde eser element analizi kimyasal yöntemlerle de yapılmaktadır, ancak tayin süresi pek ekonomik değil, hassaslığıda nükleer metodlar kadar iyi değildir. Burada madde tayini, ana maddenin yanması sonucu meydana gelen buharların incelenmesi ile yapılmaktadır, oysa nükleer yöntemlerde ana maddeyi yok etmeden tayin yapıldığından çok daha güvenilir ve tercih edilir olmaktadır. Y - ların madde ile etkileşmesi sonucu elde edilen sonuçlar diğer metotlarla elde edilenlerle karşılaştırıldığında daha kısa, kesin ve doğru sonuçlar vermektedir. Bu çalışmada çift y - kaynağı metodu, gammaların madde ile etkileşmesi sonucu çok kanallı analizörde gözlenen ilgili maddedeki elementlerin karakteristiğini içeren spektrumlar, madde analizinin tayininde kullanılır. Cs - 137 ve Am - 241 kaynaklarından yayınlanan gammaların numunelerle reaksiyonu sonucu elde edilen spektrumlardan gamma spektrometresiyle ölçülen net pik alanları ilgili bağıntılarda yerine konularak nem tayini yapılmıştır. Bu çalışmada, enerji aralığı amacımıza uygun olarak 60 KeV ve 662 KeV seçilmiştir. Bu amaçla 6 standart y- kaynağı kullanılmıştır. Soma Linyit kömürü 105 °C etüvde kurutulduktan sonra ve önce y- kaynaklarının önüne çeşitli kalınlıklarda yerleştirilerek 10800 s süreyle ışınlanmış ve çok kanallı analizör yardımıyla verdikleri spektrumlann analizi yapılmıştır. Sonuç olarak kömürdeki nem miktarı % 10. 1 1 olarak hesaplanmıştır. Yan iletken detektör tiplerinden sayılan yüzey engelli detektör kullanılarak, ayrıca Muğla Yatağan Eskihisar bölgesinden alınan kömürdekükürt analizi yapılmıştır. Bu metetta belli oranda kömür Cf - 252 nötronlanyla çok uzun süre ışınlanmıştır, sonra P spetrumetresiyle kükürt tayini yapılmıştır. 6