Effects Of Different Dopants Research Articles

Low Temperature de-NOx Technology-a Challenge for Vehicular Exhaust and its Remedation: An Overview

Over the past few decades, nitrogen oxides (NOx) from mobile and stationary sources have become a major environmental concern. Environmental regulations about NOx reduction are forced to become more stringent due to escalating global issues like respiratory diseases, photochemical smog, acid rain and stratospheric ozone depletion. Worldwide stringent legislations Euro 6/VI has been implemented recently in September 2014 to control the NOx emission from light and heavy duty vehicles respectively. Selective catalytic reduction (SCR) technology acquires its wide acceptance in mobile and stationary sources in catalytic NOx reduction with aqueous urea/ammonia. Most of the NOx abatement catalysts are able to reduce NOx under intermediate and high temperature ranges. At the low temperature (<523K), during the engine start-up, active NOx abatement catalysts are the challenging area in this regard due to the presence of excess H2O and SO2. A low temperature noble metal free SCR catalyst has the benefit of lesser energy expenditure and low cost advantage. The aim of the present paper is to compile the various parameters like choice of precursor, oxidation states of active components, effect of different dopants, and structural stability affects. The catalyst efficiency verified by various surface characterization studies in structure-activity relationship is also reviewed. A low temperature SCR catalyst with broad operating temperature range in engine exhausts are the viable solutions to the current situation.

The effect of different dopants on the performance of SnO2‐based dye‐sensitized solar cells

Tin oxide is a promising candidate for the replacement of titanium dioxide in dye‐sensitized solar cells (DSSCs), due to its excellent electron transport properties. The performance of TiO2‐based DSSCs can be improved either by modifying the morphology of SnO2 nanostructures, or by doping. Here, we investigate the influence of different dopants (Mg, Zn, and Ag) to SnO2 anode on the DSSC performance. We found that the addition of the dopant affects not only the electron lifetime, but also the dye adsorption as well. The best performance was obtained for zinc doped SnO2 anodes, with the power conversion efficiency of 3.4%.

Effect of Different Dopants in Films TEOS/MPTS Used to Protect the Carbon Steel

Schiff bases m-toluene N-Salicylideneaniline (m-TOL), (B) m-nitro-N- Salicylideneaniline (m-NTR) and (C) m-methoxy-N-salicylideneaniline (m-MTX) and cerium ions were studied added to 3.5 wt.% NaCl solution and added to the hybrid film based tetraethoxysilane (TEOS) e 3-methacryloxypropyltrimethoxysilane (MPTS). The polarization measurements showed lower current densities for the steel in NaCl with m-MTX, indicating that the m-MTX may be acting as an inhibitor. The hybrid films were doped with the m-MTX, Ce (III) or Ce (IV). Electrochemical measurements of open circuit potential (EOC), polarization curves and electrochemical impedance spectroscopy (EIS), were used to evaluate the corrosion behavior of the hybrid films. According Electrochemical Impedance measurements, all hybrid films, provided protection to the carbon steel. The films doped with Ce (IV), provided greater protection than the other, which indicates that this is the most suitable dopant for use in films.

Effects of different dopants on switching behavior of HfO2-based resistive random access memory

In this study the effects of doping atoms (Al, Cu, and N) with different electro-negativities and ionic radii on resistive switching of HfO2-based resistive random access memory (RRAM) are systematically investigated. The results show that forming voltages and set voltages of Al/Cu-doped devices are reduced. Among all devices, Cu-doped device shows the narrowest device-to-device distributions of set voltage and low resistance. The effects of different dopants on switching behavior are explained with deferent types of CFs formed in HfO2 depending on dopants: oxygen vacancy (Vo) filaments for Al-doped HfO2 devices, hybrid filaments composed of oxygen vacancies and Cu atoms for Cu-doped HfO2 devices, and nitrogen/oxygen vacancy filaments for N-doped HfO2 devices. The results suggest that a metal dopant with a larger electro-negativity than host metal atom offers the best comprehensive performance.

Effect of doping on microstructure and technical usage property of tantalum wire

Effect of different dopants and various dopants quantity at different annealing temperatures on microstructure of tantalum wire, bending of tantalum wire after sintering and bending after pressing into tantalum powder and sintering were investigated through observation of microstructure and testing of bending of tantalum wire after sintering and bending after pressing into tantalum powder and sintering. The results show that the recrystallization temperature of tantalum wire increases and the grain of microstructure can be reduced with the increase of dopants quantity. At the same time, the effect of dopant Ce on reduction of the grain is more obvious than that of dopant Ge. The bending time of tantalum wire after sintering increases with the increase of dopant Ge or Ce quantity. Under the same condition, the bending time of tantalum wire after pressing into tantalum powder and sintering worsens with the increase of oxygen content in tantalum powder. The bending time of tantalum wire doped with Ge and Ce after pressing into tantalum powder and sintering is better than that of tantalum wire doped with Ge, while that of tantalum wire doped with Ge is better than that of pure one when oxygen content in tantalum powder is not too high.

Novel SiC detector based on optical signal instead of electrical signal

ABSTRACTA novel SiC optical detector that produces optical signal in contrast to the electric signal generated by conventional electrical detectors. The optical detector is a remote sensor providing response to incident photons from a distant object. The incident photons modify the refractive index and, consequently, the reflectance of the doped SiC by altering the electron densities in the valence band and the acceptor energy levels. This variation in the refractive index or reflectance represents the optical signal as the sensor response, which can be determined with a probe laser such as a He-Ne laser or a light-emitting diode. The sensor can be applied to numerous remote sensing applications including high-temperature or harsh environments due to the optical read-out of the detector response with a probe laser. The effects of different dopants on the detector response for sensing different chemical species, or equivalently imaging in different MWIR wavelengths, have been studied and the dopant concentration has been found to affect the optical signal. These results indicate that a new class of SiC detectorsclassified as optical detectors can be produced for a variety of wavelengths using different dopants for numerous applications.

Effects of different dopants on the band gap and electrical conductivity of the poly(phenylene-thiazolo[5,4-d]thiazole) copolymer

Band gap energy and electrical conductivity of poly(phenylene-thiazolo[5,4-d]thiazole) were compared for different dopants.

Conducting carbon/polymer composites as a catalyst support for proton exchange membrane fuel cells

SUMMARY Carbon/poly(3,4-ethylene dioxythiophene) (C/PEDOT) composites are synthesized by in situ chemical oxidative polymerization of EDOT monomer on carbon black in order to decrease carbon corrosion that occurred in carbon-supported catalysts used in proton exchange membrane fuel cell. The effects of different dopants including polystyrene sulfonic acid, p-toluenesulfonic acid and camphorsulfonic acid with the addition of ethylene glycol or dimethyl sulfoxide on the properties of the composites are investigated. The synthesized composites are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, surface area analysis and scanning electron microscope. Electrical conductivity is determined by using the four-point probe technique. Electrochemical oxidation characteristics of the synthesized C/PEDOT composites are investigated by cyclic voltammetry by applying 1.2 V for 24 h. The composite prepared at 25 °C with p-toluenesulfonic acid and ethylene glycol shows the best carbon corrosion resistance. Platinum-supported catalyst by using this composite was prepared using microwave irradiation technique, and it was seen that the prepared catalyst did not significantly lose its hydrogen oxidation and oxygen reduction reaction activities after electrochemical oxidation. Copyright © 2013 John Wiley & Sons, Ltd.

Neurosteroid analysis by gas chromatography–atmospheric pressure photoionization–tandem mass spectrometry

A new and simple APPI interface employing commercially available hardware is used to combine GC to MS. The feasibility of the method is demonstrated in the analysis of urine samples for neurosteroids as their trimethylsilyl (TMS) derivatives. The effect of different dopants (chlorobenzene, toluene, anisole) on the ionization of the TMS derivatives was investigated. With chlorobenzene, the TMS derivatives produced intense molecular ions with minimal fragmentation, and chlorobenzene was selected as best dopant. Protonated molecules in addition to intense molecular ions were produced with toluene and anisole. The performance of the method was verified in the analysis of human urine samples. Chromatographic performance was good with peak half-widths of 3.6–4.3s, linearity (r2>0.990) was acceptable, limits of detection (LODs) were in the range of 0.01–10ngmL−1, and repeatability was good with relative standard deviations (rsd%) below 22%. The results show that the method is well suited for the determination of neurosteroids in biological samples.

Effects of Different Dopants and Doping Procedures on the Reactivity of CaO-based Sorbents for CO2 Capture

Calcium-looping is a promising CO2-capture technology. The economics and environmental impact of the process are affected by the rapid decay in reactivity of the limestone sorbent, which necessitates a high purge rate from the system to maintain sorbent reactivity. This work investigates techniques to improve long-term reactivity in such a system by doping the limestone with a variety of different dopants. It also demonstrates that the main reason for improvement is that the doping increases the volume of pores around 100 nm in diameter in the calcined material after a significant number of cycles, in comparison to the calcine from an undoped sorbent. Improved reactivity means a lower required purge-rate and fewer potential disposal issues, and less fresh limestone to be used. Doped samples were subject to repeated cycles of carbonation and calcination in a fluidized bed reactor (FBR). The work includes the use of inorganic salts MgCl2, CaCl2, Mg(NO3)2, and the Grignard reagent-isopropylmagnesium chloride. Three types of doping procedures were explored: wet impregnation, solid mixing, and quantitative wet impregnation. Experimental results showed that MgCl2, CaCl2, and Grignard reagents as dopants improved the carrying capacity of Havelock limestone. X-ray fluorescence (XRF) analysis of the doped samples after 13 cycles revealed that the number of dopant ions does not increase further with an increase in the doping concentrations above a critical value. Gas adsorption analyses showed that sorbents have a very small surface area, below 4 m2/g, post cycling. The pore size distribution appears to change significantly upon doping, and it is likely that optimizing the pore size distribution upon cycling is one reason for the enhanced reactivity observed.

Effects of dopants and copolymerization on Schottky barriers of polypyrrole and polyindole/metal interfaces

Schottky-barrier diode devices were fabricated in a sandwich configuration with poly(pyrrole-co-indole) copolymer semiconducting films prepared by electropolymerization. Effect of different dopants of ClO4 −, BF4 −, C7H7SO3 − and [Fe(CN)6]3− on the electronic properties of the fabricated devices was followed using Ag, In, Al and Cu metal junctions. Current–voltage and capacitance–voltage characteristics were recorded for making a comparative evaluation of the electronic and junction properties of the devices. The electrical characteristics of the junctions were analyzed based on the standard thermionic emission theory. Polymer doped by ClO4 − showed lower reverse saturation currents and ideality factor but higher potential barriers and rectification ratios. Effect of dopant ions and copolymerization on the optical band gaps (E g) of the films were investigated and the optical transmissions of the doped copolymer films were measured in the wavelength range of 250–900 nm. It was shown that the energy gap of copolymers laid between those of corresponding homopolymers and polyindole (PIN) doped by [Fe(CN6)]−3 had E g less than that of polymer doped by other anions whereas E g of polypyrrole was independent of dopant ions. Also, the morphology of the polymeric films revealed the surface of the PIN doped with ClO4 − was very smooth which created a good contact with indium metal.

Hole transport in pure and doped hematite

Hematite (α-Fe2O3) is a promising candidate for use in photovoltaic (PV) and photoelectrochemical devices. Its poor conductivity is one major drawback. Doping hematite either p-type or n-type greatly enhances its measured conductivity and is required for potential p-n junctions in PVs. Here, we study hole transport in pure and doped hematite using an electrostatically embedded cluster model with ab initio quantum mechanics (unrestricted Hartree-Fock theory). Consistent with previous work, the model suggests that hole hopping is via oxygen anions for pure hematite. The activation energy for hole mobility is predicted to be at least 0.1 eV higher than the activation energy for electron mobility, consistent with the trend observed in experiments. We examine four dopants—magnesium(II), nickel(II), copper(II), and manganese(II/III) in direct cation substitution sites—to gain insight into the mechanism by which conductivity is improved. The activation energies are used to assess qualitative effects of different dopants. The hole carriers are predicted to be attracted to O anions near the dopants. The magnitude of the trapping effect is similar among the four dopants in their +2 oxidation states. The multivalent character of Mn doping facilitates local hole transport around Mn centers via a low-barrier O-Mn-O pathway, which suggests that higher hole mobility can be achieved with increasing Mn doping concentration, especially when a network of these low-barrier pathways is produced. Our results suggest that the experimentally observed conductivity increase in Mg-, Ni-, and Cu-doped p-type hematite is mostly due to an increase in hole carriers rather than improved mobility, and that Mg-, Ni-, and Cu-doping perform similarly, while the conductivity of Mn-doped hematite might be significantly improved in the high doping concentration limit.

Effect of dopants on the structural, optical and electrical properties of sol–gel derived ZnO semiconductor thin films

Undoped, Ga-, In-, Zr-, and Sn-doped ZnO transparent semiconductor thin films were deposited on alkali-free glasses by sol–gel method. 2-methoxyethanol (2-ME) and diethanolamine (DEA) were chosen as a solvent and a stabilizer, respectively. The doping concentration was maintained at 2 at.% in the impurity doping precursor solutions. The effects of different dopants on the structural, optical, and electrical properties of ZnO thin films were investigated. XRD results show that all annealed ZnO-based thin films had a hexagonal (wurtzite) structure. ZnO thin films doped with impurity elements obviously improved the surface flatness and enhanced the optical transmittance. All impurity doped ZnO thin films showed high transparency in the visible range (>91%). The Ga- and In- doped ZnO thin films exhibited higher Hall mobility and lower resistivity than did the undoped ZnO thin film.

Effect of different dopants on the long lasting phosphorescence behavior of CaTiO 3:Pr 3+

In order to improve the luminescence properties of CaTiO 3:Pr 3+, a series of CaTiO 3:Pr 3+, such as CaTi 0.97Nb 0.03O 3:Pr 3+, Ca 0.8Zn 0.2TiO 3: Pr 3+, Ca 0.8Zn 0.2Ti 0.97Nb 0.03O 3:Pr 3+ and B 3+-doped Ca 0.8Zn 0.2Ti 0.97Nb 0.03O 3: Pr 3+ were prepared through conventional solid state reaction method. The results of the photoluminescence excitation and emission spectra showed that all the samples emitted red phosphorescence at 612 nm originating from 1D 2 to 3H 4 emission of Pr 3+ under the 337 nm excitation. When examined by the X-ray diffraction (XRD), all the samples presented a predominant phase of CaTiO 3 (JCPDS# 42-423) except Zn 2+-doped samples which also revealed another phase of Zn 2Ti 3O 8 (JCPDS# 73-579). The results of the afterglow decay curves showed that co-doping Zn 2+ ions, Nb 5+ ions or adding a small amount of B 3+ into Ca 0.8Zn 0.2Ti 0.97Nb 0.03O 3:Pr 3+ were effective in improving the photoluminescence properties of CaTiO 3:Pr 3+ phosphor. Thermoluminescence results showed that the trap existing in all the samples was the same as in CaTiO 3:Pr 3+ and doping singly Nb 5+ or Zn 2+ hardly changed the trap depth but co-doping Nb 5+ and Zn 2+ could modify the trapping level from 0.63 to 1.26 eV distinctively. In addition, adding a certain amount of B 3+ into CTO-PZN could also deepen the trap depth.

Effects of Different Dopants on the Growth and Phase Transition of Ba&lt;SUB&gt;3&lt;/SUB&gt;Y(BO&lt;SUB&gt;3&lt;/SUB&gt;)&lt;SUB&gt;3&lt;/SUB&gt; Crystal

结合X射线粉末衍射和差示扫描量热法,系统研究了不同格位上的掺杂对Ba3Y（BO3）3晶体的生长和相变的影响.研究发现,相同掺杂浓度10at%时,掺Nd3＋的α-Ba3Y（BO3）3晶体的相变温度（1099.6℃）比掺Yb3＋的晶体的相变温度（1145.3℃）低;且随着掺Nd3＋浓度的降低,晶体的相变温度升高,晶体在降温过程中更容易发生相变.在晶体中掺入Sr2＋离子,可以有效提高Yb3＋∶α-Ba3Y（BO3）3晶体的稳定性.随着Sr2＋掺入浓度的增加,晶体的熔点升高,相变温度降低.当Sr2＋掺杂浓度为16at%时,晶体的相变峰消失;当Sr2＋掺杂浓度分别为5at%、10at%时,晶体仍然发生相变.

Investigation of the effect of different dopants on the trap states of ZnO-based and SnO2-based varistors

The electrical properties of ZnO varistors and novel SnO2 varistors have been attributed to their grain boundary barriers. In this report, the techniques of capacitance-voltage (C-V) measurement and deep level transient spectroscopy (DLTS) were employed to investigate the effect of different dopants on the electronic states of ZnO-based and SnO2-based varistors. Two trap levels were determined in typical ZnO varistors: trap L1 at Ec-0.15±0.01eV and trap L2 at Ec-0.25±0.01eV. The different dopants affected the parameters of those traps significantly. Two deeper trap levels, trap S1 at Ec-0.30±0.03eV and trap S2 at Ec-0.69±0.03eV, were identified in both SnO2-CoO-Nb2O5 and SnO2-CoO-Nb2O5-Cr2O3 varistors. The variations in the donor density and trap density appear to be associated with the addition of trivalent Cr3+. The features of these trap levels and the defect theory related to the SnO2 varistors need to be further studied.

Titanium oxide based visible light photocatalysts: Materials design and applications

The current status of research and development on titanium oxide based visible and UV (ultraviolet) light photocatalysts is presented including a discussion of the physical–chemical effects of different dopants. Progress made in the past decade has triggered the development of several marketable applications. In particular, the state of the art of products for indoor and outdoor applications and challenges related to their introduction on the mass market are illustrated. Future trends in technology and market perspectives of photocatalysts are discussed in terms of performance improvement and materials process development.

Screening of doped MnOx–CeO2 catalysts for low-temperature NO-SCR

The effect of different dopants including niobium, iron, tungsten and zirconium oxide on the low-temperature activity of MnOx–CeO2 catalysts for the selective catalytic reduction (SCR) of NOx with ammonia has been studied with coated cordierite monoliths in model gas experiments. A clearly higher activity and particularly superior nitrogen selectivity was obtained with the niobium-doped catalyst in comparison with the MnOx–CeO2 reference system. At 200°C, the DeNOx was 80% while the N2 selectivity reached more than 96%. In contrast, a decrease of the SCR activity was observed when iron, zirconium or tungsten oxides were added to MnOx–CeO2. However, the addition of niobium oxide did not improve the resistance of the catalyst against SO2 poisoning. A strong and irreversible deactivation occurred after exposure to SO2.

DC 마그네트론 스터링법을 이용하여 증착한 Ga, Al, In 첨가 ZnO 박막의 특성

Trivalent ions(Ga, Al, In) doped ZnO films were deposited by DC magnetron sputtering on non-alkali glass substrate at substrate temperature of . We used the different three types of high density() ceramic sintered disks(doped with ; 6.65 wt%, ; 3.0 wt%, ; 9.54 wt%). This study examined the effect of different dopants(Ga, Al, In) on the electrical, structural, and optical properties of the films. The lowest resistivity of and the highest optical band gap of 3.74 eV were obtained by Ga doped ZnO(GZO) film. All the films had a preferred orientation along the(002) direction, indicating that the growth orientation has a c-axis perpendicular to the substrate surface. The average transmittance of the films was more than 85% in the visible range.

Effect of dopants on the low temperature microwave dielectric properties of Ba(Zn1/3Ta2/3)O3 ceramics

Ba(Zn1/3Ta2/3)O3 has been prepared with different dopants that gave best microwave dielectric properties at room temperature. Effects of different dopants on the low temperature microwave dielectric properties of BZT were investigated. With decrease in temperature, loss tangent was found to decrease marginally and then increase at temperatures lower than 100 K. Increase in loss factor at lower temperatures were found to be less for dopants with smaller ionic radii. Dielectric constant was found to be almost independent of temperature. Temperature coefficient of resonant frequency slowly decreased from a positive value to negative value when temperature was lowered. Temperature at which τf becomes zero was found to vary for different dopants. There is a temperature stable region for tanδ, ɛr and τf which varies for different dopants.