Nanocrystalline Tin Research Articles

Characterization of nitride coatings on high density graphite deposited by magnetron sputtering

Cathode deposit consolidation operation after electrorefining of spent metallic fuels of fast breeder reactors involves melting of U and Pu at 1300 °C after distillation of occluded chloride salt and Cd, in graphite crucibles. Nitride coatings possessing high hardness, melting point and thermodynamic stability against reactive materials and molten LiCl–KCl salts have greater potential for coating the graphite crucibles. In the present study nanocrystalline TiN, ZrN and Ti–Si–N coatings were deposited on high density graphite disc and crucible samples by DC/RF magnetron sputtering. The coated samples were characterized by SEM, GIXRD and AFM. The results indicated that coatings with uniform thickness of 3 to 6 µm were deposited on high density graphite which adheres well to the substrate. The surface morphology of TiN, ZrN and Ti–Si–N coatings examined by SEM and AFM showed the presence of spherical nanoparticles of nitrides getting agglomerated into clusters. Characterisation of nitride coated crucibles was carried out before and after uranium melting by induction heating to simulate cathode processor crucible conditions. TiN and Ti–Si–N coating appears to offer better stability, ease of ingot release and coating adhesion. The paper highlights the results of the present investigation.

Effect of alumina incorporation on restricting grain growth of nanocrystalline tin(IV) oxide

Abstract In this project, nanocrystalline SnO2 powders were successfully prepared by (a) citrate sol-gel and (b) direct precipitation methods. Powders were characterized using thermal analysis techniques (DTA-TG-DSC), X-ray powder Diffraction (XRD), surface area (BET) and electrical conductivity measurements. XRD patterns showed the presence of the cassiterite structure. SnO2 particles, prepared through sol-gel method exhibit crystallite sizes in the range from 3.1 to 22.3 nm when the gel is heat treated at different temperatures up to 900°C. SnO2 nanocrystallites prepared by the precipitation method are comparatively larger in size. The higher specific surface area was obtained for the powder prepared using sol-gel method and the obtained average grain size (d) is relatively large compared with that of the average crystallite size. The powders show a semiconducting behavior with increasing temperature. The higher conductivity obtained for SnO2 prepared by sol-gel method can be attributed to their smaller average crystallite size. XRD of alumina doped powder exhibits finer particles than pure SnO2. TEM images showed that the particles are spherical in shape and consist of a core of SnO2 surrounded by a coating of alumina. The calculated surface area was found to decrease with temperature increases. Due to the effective role of Al2O3 additive as a grain growth inhibitor for the matrix grains, the observed surface area for the coated materials are predominantly higher than for the uncoated materials.

Effect of Au and NiO catalysts on the NO2 sensing properties of nanocrystalline SnO2

Nanocrystalline tin dioxide has been synthesized, and its surface has been modified with Au and NiO. Their distributions in the nanocrystalline tin dioxide have been examined by X-ray diffraction and transmission electron microscopy. The NO2 sensing properties of the materials have been studied in the range 100–1000 ppb. Both gold and nickel enhance the NO2 response of SnO2. Codoping with Au and NiO markedly enhances its sensing response and, in addition, lowers the peak response temperature. The observed effect of NO2 concentration in dry air on the sensing response of the SnO2〈Au, NiO〉 nanocomposite can be understood in terms of the sequence of processes that take place on the SnO2 surface upon nitrogen dioxide adsorption in the presence of chemisorbed oxygen.

Crystallite growth kinetics of highly pure nanocrystalline tin dioxide: The effect of palladium doping

TXRD study together with BET, HRTEM and TEM techniques were performed to investigate the effect of Pd doping on crystallite growth kinetics of highly pure nanocrystalline SnO 2 during isothermal annealing at 873, 973 and 1073 K. Apparent activation energy for crystallite growth of blank as well as surface and bulk doped SnO 2 was estimated applying grain growth model with size-dependent impediment. Low activation energy for blank material (∼23 kJ mol −1) suggests that Sn self-diffusion on the reduced crystallite's surface is the most probable mechanism contributing to the growth process. Together with very low crystallite growth rate blank material demonstrates the highest agglomeration degree after annealing. Doping with Pd does not result in drag effect on crystallite boundary mobility. In contrary, it results in remarkable increase of crystallite growth rate together with an increase in the activation energy. In the case of bulk doped SnO 2 the phenomenon of crystallite coalescence was observed.

Photovoltaic Behavior of Nanocrystalline SnS/TiO2

Nanocrystalline tin sulfide (SnS) was prepared by chemical bath deposition, and the photovoltaic behavior of SnS/TiO2 was studied. The X-ray diffraction pattern and transmission electron microscopy revealed an ∼6 nm SnS polycrystalline orthorhombic structure. The SnS film exhibited a band gap of 1.3 eV, and its absorption coefficient was more than 1 × 104 cm−1 in the visible light range. The electrical conductivity activation energy of the SnS film was 0.22 eV, determined when the sample was heated in the temperature range of 111−144 °C. Although the sample was insulating at room temperature, photovoltaic behavior was found in a SnS/TiO2 structure, with an open-circuit voltage (Voc) of 471 mV, a short-circuit current density (Jsc) of 0.3 mA/cm2, and the conversion efficiency (η) of 0.1% under 1 sun illumination. The properties of SnS and the reasons behind the photovoltaic phenomenon of SnS/TiO2 are discussed.

Synthesis, characterization and photoluminescence properties of Dy 3+-doped nano-crystalline SnO 2

Nano-crystalline of tin oxide doped with varying wt% of Dy 3+ was prepared using chemical co-precipitation method and characterised by various advanced techniques such as BET-surface area, Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy and photoluminescence measurements. Analytical results demonstrated that the nanocrystalline tin oxide is in tetragonal crystalline phase and doping with Dy 3+ could inhibit the phase transformation, increases surface area and decreases the crystallite size. The experimental result on photoluminescence characteristics originating from Dy 3+-doping in nanocrystalline SnO 2 reveals the dependence of the luminescent intensity on dopant concentration.

Synthesis and chlorine sensing properties of nanocrystalline hierarchical porous SnO2 by a phenol formaldehyde resin-assisted process

Nanocrystalline tin dioxide (SnO2) materials with very interesting architectures (well-defined pores, hierarchical pores) were synthesized by a suitable heat treatment of SnO2/phenol formaldehyde resin (PFR) nanocomposite. The composite was obtained through a facile hydrothermal approach by using tin(IV) tetrachloride pentahydrate (SnCl4·5H2O) as a raw material, hexamethylenetetramine (HMT) as a pore-forming agent and monomer (HCHO) source for polymerization with phenol. Compared with the fine porous SnO2 sensor, the hierarchical porous SnO2 sensor showed a higher response. Owing to the hierarchical porous structure, the as-prepared materials exhibit satisfactory selectivity to chlorine along with high-sensitivity (249.3 at 10 ppm), fast response (7 s), very short recovery time (15 s), long-term stability as well as low power. The excellent sensing performance was discussed concerning the architectures of the materials.

Temperature dependent structural properties of nanocrystalline SnS structures

This letter explores the structural behavior of nanocrystalline tin mono sulfide (SnS) structures with respect to temperature (100–600 K). These studies emphasize that the structural properties of SnS nanocrystalline structures depend on the surrounding temperature. The lattice parameters of SnS nanocrystals slightly varied like their microstructures with the increase of temperature. These changes strongly influence the optical properties of SnS nanostructures. On the other hand, the structures exhibited higher strain (∼0.44%) than that of microstructured (0.3%) and bulk (0.12%) counterparts. The observed results are discussed under the light of existing concepts and reported.

Mechanosynthesis of nanocrystalline titanium nitride and its microstructure characterization

Nanocrystalline stoichiometric TiN powder has been prepared by ball-milling the α-Ti powder under N 2 gas at room temperature. The α-Ti phase is partially transformed to the transient β-Ti phase and TiN phase is noticed to form after 3 h of milling and nanocrystalline TiN phase is formed after 9 h of milling. Microstructure characterization of unmilled and ball-milled samples characterized primarily by X-ray diffraction employing the Rietveld structure refinement clearly reveals the presence of TiN phase and inclusion of nitrogen atoms in the α-Ti lattice in the way to formation of nitride phase. Transmission electron microscopy image confirms the presence of TiN phase and the size of TiN particles obtained from both XRD and TEM methods of characterization are very close in value (∼13 nm).

Evaluation of nanocrystalline TiN films prepared by arc ion plating

Monolayer and multilayer TiN films were synthesized on a SKD 11 steel sheet by an arc ion plating technique and the correlation between the microstructure and properties of the TiN films was comparatively investigated. The results indicated that the main phase was fcc-TiN, showing a (200) preferred orientation in the film under 2.0 × 10−1 torr N2 partial pressure, whereas a gradual transition to (111) preferred orientation was observed with decreasing N2 partial pressure to 1.4 × 10−1 torr. The (200) and (111) textures in the film under an arc current of 80 A were found to be competitive orientations, but the (200) texture became stronger as the arc current was increased. Compared to the optimal monolayer TiN films, the multilayer TiN film possessed high hardness of up to 20.3 ± 1.3 GPa and excellent wear resistance. These features are attributed to the presence of dense microstructures that are mainly composed of TiN phase and are around 1.7 μm to 1.8 μm in thickness.

The effect of substrate temperature on the microstructural properties of nanocrystalline tin oxide coatings produced by APCVD

Tin oxide thin films were grown by chemical vapor deposition on glass substrates at atmospheric pressure and temperatures of 400, 500, and 600°C over deposition times from 15 to 60 min with 15-min intervals to investigate the effect of deposition time. A homemade horizontal reactor was used for deposition from SnCl2 + 2H2O precursors with pure oxygen flowing at a rate of 5 ccpm. The structure was analyzed by X-ray diffraction (XRD), scanning electron microscopy, and atomic force microscopy techniques to reveal the deposition mechanisms and crystalline structures. XRD analysis showed that the predominant phase in all experimental conditions was SnO2. From the XRD analysis, it is understood that the preferred orientation of the SnO2 films is dependent on their thickness, which is affected by deposition time and substrate temperature.

Sensor properties of hybrid SnO2-polysilazane materials

New hybrid materials based on nanocrystalline tin dioxide and two types of surface-immobilized polymer organosilicon structures with hydrocarbon substitutes were synthesized for gas sensors application. The sensing responses of pure SnO2 and hybrid samples were determined in the presence of NO2 (ppb range), CO (ppm range) and different humidity (RH = 15 – 95 %). Also the influence of water presence on sensor signal towards NO2 and CO was analyzed. Strong influence of nature of hydrocarbon substitutes on sensor response value towards NO2 and H2O was discovered.

Implantation Induced Hardening of Nanocrystalline Titanium Thin Films

Formation of nanocrystalline TiN at low temperatures was demonstrated by combining Pulsed Laser Deposition (PLD) and ion implantation techniques. The Ti films of nominal thickness approximatly 250 nm were deposited at a substrate temperature of 200 degrees C by ablating a high pure titanium target in UHV conditions using a nanosecond pulsed Nd:YAG laser operating at 1064 nm. These films were implanted with 100 keV N+ ions with fluence ranging from 1.0 x 10(16) ions/cm2 to 1.0 x 10(17) ions/cm2 The structural, compositional and morphological evolutions were tracked using Transmission Electron Microscopy (TEM), Secondary Ion Mass Spectrometry (SIMS) and Atomic Force Microscopy (AFM), respectively. TEM analysis revealed that the as-deposited titanium film is an fcc phase. With increasing ion fluence, its structure becomes amorphous phase before precipitation of nanocrystalline fcc TIN phase. Compositional depth profiles obtained from SIMS have shown the extent of nitrogen concentration gradient in the implantation zone. Both as-deposited and ion implanted films showed much higher hardness as compared to the bulk titanium. AFM studies revealed a gradual increase in surface roughness leading to surface patterning with increase in ion fluence.

Template Infiltration Routes to Ordered Macroporous TiN and SiNx Films

Ordered macroporous films of nanocrystalline TiN and amorphous SiNx on silica substrates have been prepared. This involved infiltration of sacrificial templates of close-packed polystyrene microsphere arrays with precursor materials, followed by pyrolysis under ammonia to remove the template and form the ceramic materials. TiN was prepared from a sol?gel route, whereas SiNx was introduced using a Si(NHMe)4 precursor solution. Hexane was found to be the solvent most compatible with the divinylbenzene-cross-linked polystyrene template and was used for both materials

Structural, optical and electrical studies on nanocrystalline tin oxide (SnO2) thin films by electron beam evaporation technique

Nanocrystalline tin oxide (SnO2) thin films were coated using electron beam evaporation technique on glass substrates. To study the gleaming out look of the structure and surface morphological changes, the films were annealed in the temperature 350–550 °C for 1 h. The annealed films were subjected to X-ray diffraction (XRD) and atomic force microscopy (AFM) studies. The XRD patterns of SnO2 thin films as-deposited and annealed at 350 °C illustrate that the films were amorphous, and beyond 350 °C and thereafter they became polycrystalline with tetragonal structure. The crystallite size of the annealed films, obtained through the XRD analysis, increased with the increasing annealing temperature, and it was found to be from 3.6 to 12 nm. The photoluminescence (PL) studies on these films were also carried out. The origin of luminescence was assigned to the defects of the nanocrystalline SnO2 films. The Optical studies (UV-VIS) were performed and the optical band gab energy (Eg) calculations, the dependence of absorption coefficient on the photon energy at short wavelengths, were found to be increasing from 3.65 to 3.91 eV is also investigated.

Nanocrystalline titanium nitride films prepared by electrophoretic deposition

Homogeneous and adhesive nanocrystalline TiN thin films are fabricated on Ti substrates by electrophoretic deposition in an aqueous suspension containing TiN powders at room temperature. X-ray diffraction confirms the formation of TiN films and the film color varies with deposition time. The current–time curves are recorded during deposition and the surface morphology and cross-sectional images are investigated by scanning electron microscopy (SEM). The film thickness is around 6.1 μm after 10 min deposition and increases with deposition time. The adhesion strength is characterized by the ultrasonic vibration method and peel-off test. Our results suggest that electrophoretic deposition is a practical and facile technique to prepare nanocrystalline TiN films that are particularly suitable for the decorative coating industry.

Effect of fluorine doping on highly transparent conductive spray deposited nanocrystalline tin oxide thin films

The undoped and fluorine doped thin films are synthesized by using cost-effective spray pyrolysis technique. The dependence of optical, structural and electrical properties of SnO 2 films, on the concentration of fluorine is reported. Optical absorption, X-ray diffraction, scanning electron microscope (SEM) and Hall effect studies have been performed on SnO 2:F (FTO) films coated on glass substrates. The film thickness varies from 800 to 1572 nm. X-ray diffraction pattern reveals the presence of cassiterite structure with (2 0 0) preferential orientation for FTO films. The crystallite size varies from 35 to 66 nm. SEM and AFM study reveals the surface of FTO to be made of nanocrystalline particles. The electrical study reveals that the films are degenerate and exhibit n-type electrical conductivity. The 20 wt% F doped film has a minimum resistivity of 3.8 × 10 −4 Ω cm, carrier density of 24.9 × 10 20 cm −3 and mobility of 6.59 cm 2 V −1 s −1. The sprayed FTO film having minimum resistance of 3.42 Ω/cm 2, highest figure of merit of 6.18 × 10 −2 Ω −1 at 550 nm and 96% IR reflectivity suggest, these films are useful as conducting layers in electrochromic and photovoltaic devices and also as the passive counter electrode.

Influence of γ-irradiation on the optical properties of nanocrystalline tin phthalocyanine thin films

SnPc in powder and thin film forms were found to be polycrystalline with monoclinic lattice. The morphological and structural properties of the obtained SnPc films were characterized from electron scanning micrographs and X-ray diffraction patterns. In the γ-irradiated film the formed agglomeration increased the crystallite size. The refractive index, n, and the absorption index, k, were obtained from spectrophotometric measurements of the transmittance and reflectance at normal incidence of light in the wavelength range 200–2500 nm. γ-Irradiation films shifted the transmission edge toward lower wavelength and increase the optical energy gap value. According to the analysis of dispersion curves, the dielectric constants and dispersion parameters were obtained. The absorption analysis performed indicated indirect allowed electronic transitions and the optical energy band gap 2.84 and 2.63 eV for the as-deposited and the γ-irradiated films, respectively.

Nanoindentation and corrosion studies of TiN/NiTi thin films for biomedical applications

The present study explored the in situ deposition of hard and adherent nanocrystalline TiN protective coating on NiTi thin films prepared by dc magnetron sputtering to improve the surface, mechanical and corrosion properties of NiTi thin films without sacrificing the phase transformation effect. The structural, electrical, and mechanical studies were performed on both pure NiTi and TiN/NiTi films and the results were compared. Nanoindentation studies were performed at temperatures of 297 K, 323 K, and 380 K to determine the hardness and reduced modulus. TiN/NiTi films were found to exhibit high hardness, high elastic modulus and thereby better wear resistance as compared to pure NiTi films. Further the application of TiN/NiTi films in the electrochemical sensing of dopamine, which has a critical physiological importance in Parkinson's disease has also been demonstrated.

Microstructural characteristics and mechanical properties of magnetron sputtered nanocrystalline TiN films on glass substrate

Nanocrystalline TiN thin films were deposited on glass substrate by d.c. magnetron sputtering. The microstructural characteristics of the thin films were characterized by XRD, FE-SEM and AFM. XRD analysis of the thin films, with increasing thickness, showed the (200) preferred orientation up to 1·26 μm thickness and then it transformed into (220) and (200) peaks with further increase in thickness up to 2·83 μm. The variation in preferred orientation was due to the competition between surface energy and strain energy during film growth. The deposited films were found to be very dense nanocrystalline film with less porosity as evident from their FE-SEM and AFM images. The surface roughness of the TiN films has increased slightly with the film thickness as observed from its AFM images. The mechanical properties of TiN films such as hardness and modulus of elasticity (E) were investigated by nanoindentation technique. The hardness of TiN thin film was found to be thickness dependent. The highest hardness value (24 GPa) was observed for the TiN thin films with less positive micro strain.