Change In Preferred Orientation Research Articles

Morphological, cathodoluminescence and thermoluminescence studies of defects in diamond films grown by HF CVD technique

A set of diamond layers was synthesized by Hot Filament Chemical Vapor deposition (HF CVD) from methanol-hydrogen (CH3OH–H2) gas mixture. By changing feed gas composition the obtained diamond films show different morphologies and microcrystal sizes as indicate the Scanning Electron Microscopy (SEM) pictures.The obtained diamond films were analysed by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), cathodoluminescence (CL) and thermoluminescence (TL) spectroscopy.The diamond's microcrystallities preferred orientation in diamond layers was assessed from X-ray diffraction measurements and described by texture coefficient TC(hkl). The cathodoluminescence study clearly shows that relative intensities of the band at 430 nm and at 605 nm changes as the preferred orientation changes from <400> to <220>. It was also shown that the morphology and the microcrystallities preferred orientation has an essential influence on the thermoluminescence properties of polycrystalline diamond layers.

Investigation on nebulizer spray deposited Gd-doped PbS thin films for photo sensing applications

Nebulizer assisted spray technique has been implemented for the deposition of pure and gadolinium (Gd) doped PbS thin films at a substrate temperature of 210 °C onto glass substrate using lead nitrate and gadolinium (III) acetate as precursors. Doping percentage of Gd was varied from 0 to 5 wt% for the preparation of Gd doped films and to analyze the film property. A variety of techniques like X-ray diffraction, Raman spectrum, scanning electron microscopy, atomic force microscopy, energy dispersive X- ray, UV–Visible spectrometer, and keithley source meter were used to study the influence of Gd doping in PbS thin films X-ray diffraction revealed no change in preferential orientation of the crystal planes without any secondary phases formed for all the Gd-doped films. And also it confirmed that the nature of the films were polycrystalline with simple cubic structure. It also further confirmed polycrystalline simple cubic structure with decrease of crystallite size from 21 nm to 16 nm for the increase of gadolinium doping concentration from 0 to 5 wt%. Noticeable change in the grain size was observed for the 5 wt% of gadolinium doping with uniformly distributed spherical shaped nanosize grains fully covering the entire surface. The compositional analysis confirmed the presence of Pb, S and Gd in the films. The optical parameters of Gd doped PbS thin films such as band gap energy, refractive index; extinction co-efficient, and real and imaginary parts of dielectric constant were determined using transmission, absorption and reflectance spectra in the range of 300–2400 nm. A maximum value of photo current was observed for 5 wt% gadolinium doped film.

Au-induced improvements in the grain stability and mechanical properties of Ag-based alloy wires under electrical current stressing

The evolutions of the surface morphologies, cross-sectional microstructures, and mechanical properties of two types of Ag-based alloy wires with different Au contents under a 105 A/cm2 electrical current density across various times were compared in this study. Ag-based alloy wires that contain 8 wt% Au and 15 wt% Au with 3 wt% Pd were produced via rapid drawing and multiple annealing processes to replace commercial Au-bonded wires in the electronic packaging industry. The surface morphologies of these wires were revealed by scanning electron microscopy (SEM), and cross-sectional microstructures were analyzed by electron back scattering diffraction (EBSD). The SEM observations showed grain- and step-like structures in the Ag–8Au–3Pd and Ag–15Au–3Pd wires after a 5-h treatment, respectively. EBSD results revealed a change in the main preferred orientation from slender grains to equiaxed grains because the high-angle grain boundaries (HAGB) were reduced, and the twin boundaries (TB) were multiplied along the drawing direction. In terms of mechanical properties, Ag–15Au–3Pd wire showed better breaking loads and elongations than Ag–8Au–3Pd wire. The Au effect in Ag-based alloy wires reduced the atomic diffusion to stabilize grain structures and induce a dislocation accumulation, which subsequently improved the mechanical properties by retaining and forming HAGBs, LAGBs, and TBs under high current stressing.

The characteristics of nickel film produced by supercritical carbon dioxide electroplating with ultrasonic agitation

This study uses a novel fabrication method of thin metal coatings by Ni electroplating combining ultrasonic agitation with supercritical CO2 (US-SC-CO2) mixed into conventional electrolyte. Coatings were also produced by the conventional and regular SC-CO2 electroplating methods for comparison. The characteristics obtained from the three fabrication methods such as surface morphology, hardness, roughness; crystallographic orientation, grain size; wear and corrosion resistance were all individually analyzed. Results show that plating quality achieved by US-SC-CO2 method is superior to that of regular SC-CO2 and conventional methods. With US-SC-CO2 process we achieved smoother and more compact surface morphologies, smaller grain size, lower surface roughness and higher microhardness, which also suggests good wear resistance. From XRD analysis we observed changes in preferred orientation due to application of the various methods. From the results of US-SC-CO2 electroplating and the operating mechanism of ultrasonic agitation we can confirm that this new type of ultrasonic agitation can indeed replace the role of surfactants to enhance coating aspect and properties, reducing their influence over the deposited metal coating, associated costs, and waste. In H2SO4 solution, the nickel coating fabricated by US-SC-CO2 method displayed the best polarization resistance among the three processes. More detailed experimental results and in depth discussion are presented in this paper.

Effect of Tensile Strength on the Microstructure of Graphite Impregnated with Salt Revealed by In Situ Synchrotron-Based Two-Dimensional X-ray Diffraction

Owing to the inhomogeneous distribution of FLiNaK salt impregnated into graphite which is observed by scanning electron microscopy and an element probe micro-analyzer, a map scan of in situ real-time tensile synchrotron-based two-dimensional X-ray diffraction (2D-XRD) at several fixed external forces was implemented to reveal the local microstructure evolution of graphite and FLiNaK salt. Notably, a stress concentration area (SCA), that is, the main interaction area between graphite and salt, was found and then transformed from one region to another region because of the unbalanced squeeze interaction between graphite and FLiNaK salt with the increase of external force. During the external stress load process, a smaller grain size, poorer crystallinity of graphite and a larger grain size, better crystallinity of FLiNaK salt appear in the SCA; meanwhile, the changes of crystallographic preferred orientation of FLiNaK salt domains in SCA imply that the external load force makes better the ordered stacking of the larger crystal grains of the FLiNaK salt impregnated into graphite. Most importantly, we have found for the first time that the fracture position of graphite impregnated with FLiNaK salt always occurs near the SCA rather than at a fixed region under the external stress load. Thus, the present study not only helps to reveal the interaction mechanism between graphite and FLiNaK salt under the external stress load but also contributes to accurately predict and analyze the stress state of components, which would have an effective impact on the design of a molten salt reactor and the reliability of the component safety assessment.

Characteristics of (002) Oriented Hydroxyapatite Coatings Deposited by Atmospheric Plasma Spraying

Hydroxyapatite (HA) coatings with strong (002) preferred orientation were successfully prepared on Ti-6Al-4V substrates with conventional atmospheric plasma spraying (APS). The intensity changes of (002) preferred orientation along the coating depth were investigated and the mechanical properties of these coatings were analyzed. Results indicated that the intensity of (002) preferred orientation at a distance of longer than ~90 mm from the interface showed a high value, where uniformly distributed columnar grains in a direction perpendicular to the coating surface were observed. The results obtained from experiments on the mechanical properties revealed that the (002) oriented coatings prepared by conventional APS technique exhibited excellent mechanical properties. Meanwhile, this study provided a simple and rapid method for the preparation of HA coatings with (002) preferred orientation.

Micro-stucture and Mechanical Properties of (NbAlSi)N Coatings by Arc Ion Plating with Different Negative Bias

Metastable (NbAlSi)N hard coatings were deposited on 1Cr11Ni2W2MoV steel sheetsby arc ion plating system at different negative pulse bias. The surface morphologies, fractured cross-sections, phase structure, hardness, friction coefficient were characterized using scanning electron microscopy,X-ray diffraction, microindentation and friction tester. All (NbAlSi)N coatings were mainly composed of δ-NbN with minorδ’-NbN. The applicating of negative bias gave rise to the change of preferred orientation, crystal refinement, decreased droplet number and improved structure density. With the increase of negative bias voltage, the hardness increased obviously and the friction coefficient decreased.

Microstructural characterization of electrodeposited and heat-treated Ni-B coatings

Ni-B coatings were electrodeposited in a modified Watts bath containing trimethylamine borane (TMAB). Chemical composition, phase constituent, texture and morphological characteristics of the as-deposited and isothermally annealed (300 °C) coatings were investigated as a function of the boron content (CB) using inductively coupled plasma spectroscopy (ICP), X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The nanostructural features of selected coatings were investigated using high resolution transmission electron microscopy (HRTEM). The results indicated that the CB of the deposits increases with increasing the TMAB concentration (CTMAB) in the deposition bath, and the maximum boron content of 4.2 wt% is obtained at CTMAB = 7 g/L. By increasing the boron content of the as-deposited coatings; (i) XRD peaks widen and lose their intensities, (ii) preferred orientation changes from (200) to (111), (iii) grain size of crystalline phase reduces from 13 nm for pure Ni to 2.3 nm for Ni-4.2 wt% B coating, and (iv) spherical surface morphology becomes finer. The HRTEM analysis of the Ni-2.5 wt% B coating revealed the formation of a two-phase structure consisting of equiaxed nanocrystalline domains (nanograins) with average size of 4.3 nm embedded in a thin layer of amorphous phase. Isothermal annealing at 300 °C for 1 h enhances crystallinity of all the studied coatings and increases grain size and changes preferred orientation of the pure Ni coatings from (200) to (111) while grain size and preferred orientation of alloy coating remains nearly unchanged.

Effect of synchronized bias in the deposition of TiB2 thin films using high power impulse magnetron sputtering

Titanium diboride thin films have been deposited from a compound TiB2 target on Si(001) substrates at a temperature of 500 °C using high power impulse magnetron sputtering (HiPIMS) at a frequency of 1000 Hz and pulse lengths of 20 and 40 μs. A −60 V bias pulse of different pulse length was applied at different time delay relative to the HiPIMS pulse. The average energy per deposited species, ⟨ED⟩ = Ei(Ji/Jt), where Ei is the average ion energy and Ji/Jt is the ratio of the ion bombarding flux to the total flux of deposited species, is strongly dependent on bias mode. A change in preferred orientation from (101) to (001) is observed when ⟨ED⟩ increase above 50 eV. The limited adatom mobility at ⟨ED⟩ below 50 eV promote growth of fast growing planes resulting in a (101) texture, while ⟨ED⟩ above 50 eV supply sufficient energy for development of the thermodynamically more favorable (001) texture. A linear increase in compressive residual stress with the increase in ⟨ED⟩ is also found, due to more intensive Ar+ ion bombardment. Analysis of charge-state-resolved plasma chemistry and ion energy shows that the total flux of bombarding ions contains a higher fraction of B+ when the bias is applied in synchronous with the HiPIMS pulse instead of after, resulting in a lower residual stress at similar values of ⟨ED⟩ (cf. −2.0 ± 0.2 and −2.6 ± 0.1 GPa). This study shows that use of a bias synchronized in different modes relative to the HiPIMS pulse, can be used as a tool to control ⟨ED⟩ and to some extent the type of bombarding species, and hence the microstructure of TiB2 thin films.

Controllable formation of MoS2 via preferred crystallographic orientation modulation of DC-sputtered Mo thin film

In this letter, we report the effects of preferred crystallographic orientation of Mo films on the formation of MoS2 layer through elemental sulphurization process. Vacuum thermal annealing of as-sputtered Mo films results in noticeable change in preferred crystallographic orientation from (1 1 0) to (2 1 1) plane. Correlation between structural and Raman spectroscopy study indicates that Mo film with predominantly (2 1 1) orientation results in pronounced formation of MoS2 compared to the film with the higher degree of (1 1 0) orientation. Planar packing factor, which depends on crystallographic orientation is proposed to play a crucial role in determining the degree of MoS2 formation.

Critical role of the coupling between the octahedral rotation andA-site ionic displacements inPbZrO3-based antiferroelectric materials investigated byin situneutron diffraction

This in situ neutron-diffraction study on antiferroelectric (AFE) $\mathrm{P}{\mathrm{b}}_{0.99}(\mathrm{N}{\mathrm{b}}_{0.02}\mathrm{Z}{\mathrm{r}}_{0.65}\mathrm{S}{\mathrm{n}}_{0.28}\mathrm{T}{\mathrm{i}}_{0.05}){\mathrm{O}}_{3}$ polycrystalline materials describes systematic structural and associated preferred orientation changes as a function of applied electric field and temperature. It is found that the pristine AFE phase can be poled into the metastable ferroelectric (FE) phase at room temperature. At this stage, both AFE and FE phases consist of modes associated with octahedral rotation and $A$-site ionic displacements. The temperature-induced phase transition indicates that the octahedral rotation and ionic displacements are weakly coupled in the room-temperature FE phase and decoupled in the high-temperature FE phase. However, both temperature and $E$-field-induced phase transitions between the AFE and high-temperature FE phase demonstrate the critical role of coupling between octahedral rotation and $A$-site ionic displacements in stabilizing the AFE structure, which provides not only experimental evidence to support previous theoretical calculations, but also an insight into the design and development of AFE materials. Moreover, the associated preferred orientation evolution in both AFE and FE phases is studied during the phase transitions. It is found that the formation of the preferred orientation can be controlled to tune the samples' FE and AFE properties.

Controlling intercalations of PBDTTT-EFT side chain to initiate suitable network for charge extraction in PBDTTT-EFT:PC71BM blended bulk heterojunction solar cell

Electrical, optical and structural properties, based on blend of PBDTTT-EFT:PC71BM bulk heterojunction solar cell is investigated. We have shown the presence of PC71BM in the blend facilitates interfaces for charge transfer mechanisms leading to PCEs of ~ 9.38%. GIXRD line profile obtained reveals that quantitative presence of PC71BM initiates a change in preferred orientation. It is proposed that PC71BM facilitates polymer alkyl side chain intercalations causing reduced d100 spacing, leading to larger π-π stacking of the back bone. The data obtained from d200 plane associated with PC71BM, reveals correlation between increased vertical stacking and PC71BM loading, suggesting a bicontinuous network for electron transport. Raman spectroscopy results provides evidence of PC71BM impact on frequency shift associated with C = C stretching mode of side chain thiophene rings responsible for of π-π spacing. Correlations between AFM surface roughness and blend ratio reveals migration of PC71BM to the film surface.

Effects of nitrogen vacancies on phase stability and mechanical properties of arc deposited (Ti0.52Al0.48)Ny (y < 1) coatings

Nitrogen sub-stoichiometric (Ti0.52Al0.48)Ny (0.92≥y≥0.46) coatings were grown in a mixed Ar/N2 atmosphere by cathodic arc deposition on cemented carbide (WC/Co-based) substrates. The coatings present a columnar structure with decreasing column widths from 250 to 60nm, due to a corresponding reduced N content, accompanied by changes in preferred orientation from 200 to 111 to 220. Among these, coatings prepared with 0.92≥y≥0.75 exhibit spinodal decomposition and consequently age hardening at elevated temperatures. A reduced N content upshifts the hardness maximum by >300°C. For these samples, the high temperature treatment resulted in interdiffusion of substrate elements, Co and C, mainly along column boundaries. Nevertheless, no detrimental effect in the hardness could be correlated. Conversely, a low N content sample (y=0.46) presents significant lattice diffusion of substrate elements Co, C, W, and Ta in the coating. In this case, the substrate elements are present throughout the coating, forming additional phases such as c-Ti(C,N), c-Co(Al,Ti,W), and c-(Ti,W,Ta)(C,N), with an observed increased hardness from 16 to 25GPa. We suggest that the substitution of nitrogen by carbon and the solution of W and Ta in c-TiN are responsible for the observed hardening. Our investigation shows the potential of sub-stoichiometric (Ti1−xAlx)Ny coatings for high temperature applications such as cutting tools and puts forth corresponding criteria for N content selection.

Electrophilic fluorination of α-Fe2O3 nanostructures and influence on magnetic properties

Dendritic nanostructures of fluorinated α-Fe2O3 are synthesized using Potassium Ferrocyanide along with Selectfluor™ (F-TEDA), HF, TBABF4, NaF and NH4F as Fe and F precursors respectively in an in-situ hydrothermal process. The choice of sources is based on the nature of fluorine; F-TEDA uniquely acts as a source for electrophilic fluorine while others are nucleophilic in nature. The effect of fluorination on α-Fe2O3 nanostructures is examined from the interplay between (110) and (104) growth direction and crystallite size by X-Ray diffraction analysis and the amount of fluorination is observed by elemental analysis. A significant change in the magnetic property of α-Fe2O3 is observed for different concentrations of F-TEDA. Pristine α-Fe2O3 undergoes an antiferromagnetic to ferromagnetic transition with saturation magnetization value of ~13emu/g and coercivity of 109.8Oe. However, α-Fe2O3 nanostructures prepared with HF, NH4F, TBABF4 and NaF in absence of fluorination remain antiferromagnetic despite of changes in preferred orientation and crystallite size. The interesting magnetic properties arising from F-TEDA is attributed to surface fluorination that results in uncompensated surface spins.

Influence of yttrium addition on reactive sputtered W–Y–N coatings

W–Y–N coatings with yttrium content ranging from 0 to 8.2 at.-% were deposited by reactive magnetron sputtering technique. The influence of yttrium content on the structure, oxidation resistance and mechanical properties was investigated. The results show that yttrium atoms substitute tungsten atoms forming the solid solution W–Y–N coatings. All the coatings exhibit a single-phase face-centered cubic structure and the preferred orientation changes from (200) to (111) with yttrium addition. The grain size of W–Y–N coatings decreases with the increase of yttrium content. The oxidation resistance temperature of W–Y–N coatings increases from 500°C at 0 at.-% Y to 730°C at 8.2 at.-% Y. All coatings are in compressive stress state. The hardness, elastic modulus and compressive stress of W–Y–N coatings increase gradually from 28.0, 320 and 1.1 GPa at 0 at.-% Y to 36.0, 385 and 2.1 GPa at 8.2 at.% Y, respectively. The improvement of hardness was attributed to the effect of solid solution strengthening and the grain refinement. In addition, the addition of yttrium content into WN coating also improves its resistance against elastic strain and plastic deformation to failure.

Influence of niobium addition on structure and mechanical properties of W-Nb-N coatings

W-Nb-N coatings with Nb content ranging from 0 to 13.2 at.% were deposited by reactive magnetron sputtering technique. The influence of Nb content on the structure and mechanical properties was investigated. The results show that Nb atoms substitute W atoms forming the solid solution W-Nb-N. All the coatings exhibit a single-phase face-centered cubic (fcc) structure and the preferred orientation changes from (200) to (111) with Nb addition. The grain size of W-Nb-N coatings decreases with the increase of Nb content. The hardness and elastic modulus of W-Nb-N coatings increase gradually from 28.0 GPa to 320 GPa at 0 at.% Nb to 36.0 GPa and 386 GP at 13.2 at.% Nb, respectively. The adhesion between coatings and Si substrate also could be improved by Nb addition.

Structure and oxidation resistance of W1–xAlxN composite films

A series of W1–xAlxN films (0<x<38.6%, mole fraction) were deposited by reactive magnetron sputtering. The composition, microstructure, mechanical properties and oxidation resistance of the films were characterized by EPMA, XRD, XPS, nano-indentation, SEM and HRTEM. The effect of Al content on the microstructure and oxidation resistance of W1–xAlxN films was investigated. The results show that WN film has a face-centered cubic structure. The preferred orientation changes from (111) to (200). The W1–xAlxN films consist of a mixture of face-centered cubic W(Al)N and hexagonal wurtzite structure AlN phases. The hardness of the W1–xAlxN films first increases and then decreases with the Al content increasing. The maximum hardness is 36 GPa, which is obtained at 32.4% Al (mole fraction). Compared with WN film, the W1-xAlxN composite films show much better oxidation resistance because of the formation of dense Al2O3 oxide layer on the surface.

Silencing "Top-Down" Cortical Signals Affects Spike-Responses of Neurons in Cat's "Intermediate" Visual Cortex.

We examined the effects of reversible inactivation of a higher-order, pattern/form-processing, postero-temporal visual (PTV) cortex on the background activities and spike-responses of single neurons in the ipsilateral cytoarchitectonic area 19 (putative area V3) of anesthetized domestic cats. Very occasionally (2/28), silencing recurrent “feedback” signals from PTV, resulted in significant and reversible reduction in background activity of area 19 neurons. By contrast, in large proportions of area 19 neurons, PTV inactivation resulted in: (i) significant reversible changes in the peak magnitude of their responses to visual stimuli (35.5%; 10/28); (ii) substantial reversible changes in direction selectivity indices (DSIs; 43%; 12/28); and (iii) reversible, upward shifts in preferred stimulus velocities (37%; 7/19). Substantial (≥20°) shifts in preferred orientation and/or substantial (≥20°) changes in width of orientation-tuning curves of area 19 neurons were however less common (26.5%; 4/15). In a series of experiments conducted earlier, inactivation of PTV also induced upward shifts in the preferred velocities of the ipsilateral cytoarchitectonic area 17 (V1) neurons responding optimally at low velocities. These upward shifts in preferred velocities of areas 19 and 17 neurons were often accompanied by substantial increases in DSIs. Thus, in both the primary visual cortex and the “intermediate” visual cortex (area 19), feedback from PTV plays a modulatory role in relation to stimulus velocity preferences and/or direction selectivity, that is, the properties which are usually believed to be determined by the inputs from the dorsal thalamus and/or feedforward inputs from the primary visual cortices. The apparent specialization of area 19 for processing information about stationary/slowly moving visual stimuli is at least partially determined, by the feedback from the higher-order pattern-processing visual area. Overall, the recurrent signals from the higher-order, pattern/form-processing visual cortex appear to play an important role in determining the magnitude of spike-responses and some “motion-related” receptive field properties of a substantial proportion of neurons in the intermediate form-processing visual area—area 19.

Pengembangan Teknik Analisis Pola Difraksi Multifasa dengan Metode Rietveld Refinement: Studi Kasus Lapis Tipis PZT

In this research has been developed multifasa diffraction pattern analysis technique with rietveld refinement method with case study of application of the technique on thin layer of PZT (PbZrxTi (1-x) O3) which has been synthesized with variation of 1, 2, and 3 hour annealing time. This interpretation technique begins with the determination of the background, then performed refinement parameter determinant of pattern change, peak shape, and intensity of diffraction. The parameters are, respectively, scaling factor, 2θzero, lattice parameter, gaussian peak shape constant, and gaussian-lorentzian, atomic position coordinates, and preferred orientation. The refinement results show that changes in peak shape constant give significant changes in residual values, whereas atomic and preferred orientation changes do not provide significant change in residual values.

Effects of Cu Content on Microstructure and High-Temperature Oxidation Behavior of Ti-Al-Si-Cu-N Nanocomposite Films

Ti-Al-Si-Cu-N nanocomposite films with different Cu contents were deposited on AISI-304 stainless steel by DC reactive magnetron sputtering. Both Ti-Al-Si-N and Ti-Al-Si-Cu-N nanocomposite films were oxidized at 800 °C to investigate the influence of Cu content on the microstructure and high temperature oxidation resistance by scanning electron microscope (SEM), energy disperse spectroscopy (EDS), X-ray diffraction (XRD), nanoindentation tester and a home-made indentation system. The results indicate that with the increasing copper content in the films, the micropores disappear on the surface of Ti-Al-Si-N nanocomposite film and compact films are obtained. A reduction of the grain size and a change of the (111) preferred orientation to (110) are observed. The microhardness of films increases from 14.76 GPa to 19.42 GPa. The elasticity modulus of Ti-Al-Si-Cu-N films with 1.72 at% Cu content is the minimum of 104.5 GPa. The incorporation of copper at high temperature influences the oxidation resistance of the Ti-Al-Si-N films in the two aspects, one is advancing the diffusion rate of Al element, and the other is inducing cracks of oxide layer and micropores. Ti-Al-Si-N films have a better oxidation resistance than that of the films added Cu element.