Atomic Weight Percentage Research Articles

Analysis of Contact Reaction Phenomenon between Aluminum–Silver and p+ Diffused Layer for n-Type c-Si Solar Cell Applications

In this study, the contact mechanism between Ag–Al and Si and the change in contact resistance (Rc) were analyzed by varying the firing profile. The front electrode of an n-type c-Si solar cell was formed through a screen-printing process using Ag–Al paste. Rc was measured by varying the belt speed and peak temperature of the fast-firing furnace. Rc value of 6.98 mΩ-cm−2 was obtained for an optimal fast-firing profile with 865 °C peak temperature and 110 inches per min belt speed. The contact phenomenon and the influence of impurities between the front-electrode–Si interface and firing conditions were analyzed through scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The EDS analysis revealed that the peak firing temperature at 865 °C exhibited a low atomic weight percentage of Al (0.72 and 0.36%) because Al was involved in the formation of alloy of Si with the front electrode. Based on the optimal results, a solar cell with a conversion efficiency of 19.46% was obtained.

Property representations and molecular fragmentation of chemical compounds in QSAR modeling

Basically, molar or weight scales are typical representations of the properties measured for molecular ensembles (substances). This was recently extended by the so called single molecule biology. Here we compare a large property datasets analyzing their relation to the aforementioned representations. The question of the maximal potency of ligands inspired the development and application of ligand efficiency (LE) estimators in drug design. LE could be interpreted as a property representation type. In particular, we compared, LE with boiling points (BP) vs. substance properties typically measured in the weight or molar scales, e.g. the potency, atomic weight percentage, its heavy atom count (HAC) equivalent or market prices of chemicals. As LE was deigned first of all as a measure of binding affinity of a single fragment it refers to a single molecule scale. In turn, BP clearly refers to substances. Despite this difference clear similarities between the trends of LE and BP/MW vs. HAC or MW can be indicated. We have recently showed that a trend of LE vs. heavy atom count (HAC) can be fully understood if we realize the connection of LE with the weight scale. A term 1/MW could be interpreted as an operator connecting the molar and weight scales. In turn 1/MW (1/HAC) fragments a single molecule into the Dalton or HAC fragments. A high correlation to MW or 1/MW was revealed for BOBackspace BP or LE, respectively. In turn, the prices (P) of chemicals charged in $/g are not correlated to 1/MW. A dual meaning of 1/MW (1/HAC) is an origin of uncertainty between molecular fragmentation and scales conversion.

Investigation of Organic Field-Effect Transistor (OFET) based NO2 Sensing Response using Low-Cost Green Synthesized Zinc Oxide Nanoparticles

A low-cost and green-synthesized zinc oxide nanostructured particles are extensively studied owing to their remarkable and ample characteristics with less toxicity and eco-friendly approach. The present work comprehends the green synthesis of ZnO nanostructured particles using bougainvillea leaf extract-arbitrated microwave-assisted synthesis and their use in field effect transistor for nitrogen dioxide sensing at room temperature. The as-synthesized nanoparticles were characterized using analytical techniques; XRD determined the pure crystallite structure with no impurities, SEM confirmed the spherical shape of nanoparticles with ~20 nm (average particle size) and the atomic weight percentage were analyzed using EDAX, notable photophysical properties were revealed from absorption and emission spectra performed using UV-visible spectroscopy. Poly(3-hexylthiophene) and ZnO nanoparticles were employed in the field effect transistor (p-type) for NO2 sensing at room temperature with the mobility (field-effect) of ~10-4 cm2 V-1 s-1. The sensitivity of the fabricated OFET device was extracted from the transistor characteristics (at Vgs = -30 V and Vds = -40 V) found to be ~4.8 × 10-3 nA/ppm. The device exhibited engrossing characteristics such as excellent recoverability (> 95%), with ultrafast response time (< 30 s) and greater sensitivity with high stability as can be assessed from the electrical characteristics.

Synergetic execute pressure, temperature on mixed Ac/Ag@CuO and its multi properties of solar light elucidation and antibacterial activity by hydrothermal technique

The synthesis of p-type semiconducting oxides of CuO, Ag@CuO and Ac/Ag@CuO has been effectively achieved by hydro thermal approach. These materials were characterized by X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM) with energy dispersive X-ray (EDX), elemental mapping analysis, FT-IR, Raman, HR-TEM, XPS, UV-DRS and PL analysis. The average crystalline size and SSA of Ac/Ag@CuO were found as 40.1 nm and 59.18 g/cm3 respectively by X-ray diffraction. EDAX analysis of atomic weight percentage (%) have confirmed that only C (22.9%), Ag (0.2%), O (47.1%), Cu (29.8%) and no other impurities were formed in Ac/Ag@CuO composite. FT-IR spectrum also indicate vibrational modes at 465 cm−1, 489 cm−1, 683 cm−1 and 1734 cm−1 were assigned for Cu-O, Ag-O, C=O stretching vibration. According to Raman spectrum three vibrational modes observed at 301 cm−1, 357 cm−1, 616 cm−1 due to one Ag, two Bg modes of CuO in Ac/Ag@CuO. The nanostructured materials are investigated with multi properties of photocatalytic degradation and antibacterial activity against (gram positive +ve and gram negative −ve) bacterial strain. The superior photo catalytic activity of Ac/Ag@CuO was established for the degradation of Rhodamine 6G dye in aqueous solution (pH = 9) under solar light irradiation. The control of catalytic parameters such as effect of pH, quantity of photo catalyst loading, dye absorption and photo mineralization of Rhodamine 6 G dye have been analysed. To establish the superior catalytic activity of Ac-Ag@CuO with CuO and Ag@CuO were compared. Since the co-dopant materials are having the absorbance close to the visible region (400–600 nm). The total mineralization of Rhodamine 6G dye have been analysed by COD measurements. The system of photo catalytic activity of AC/Ag @CuO nano material has been discussed. The production of reusable catalyst was achieved.

Structural and Magnetic properties of Cobalt Ferrite (CoFe2O4) Nanoparticles by Sol-Gel Technique using Yeast

The aim of the present work is to synthesize cobalt ferrite nanoparticles by sol-gel technique using yeast. The source culture is prepared using yeast, carbon and nitrogen. Three samples are prepared by mixing the source culture with ferric nitrate (0.2 M) and cobalt nitrate (0.15, 0.2, 0.25M) and stirred for suitable duration to get the gel. The final product is heated at 600°C to get the cobalt ferrite nanopowder. Structural analysis reveals the cubic phase of cobalt ferrite nanoparticles with the peaks corresponding to the plane (220), (311), (400), (511) and (440) matches with the PDF data. The peaks are sharp showing the crystalline nature of the prepared samples. From the microstructural parameters calculated for the prominent peak (311) shows the average crystallite size is 44 nm. The lattice constant is found to be around 8.350 Å which is close to the bulk value of cobalt ferrite nanoparticle (8.373Å). The calculated X-ray density is more than their bulk counterpart and is attributed to the formation of pores throughout the synthesis method. FTIR analysis shows the existence of functional groups within the prepared sample. EDAX analysis shows the rise in the atomic weight percentage of cobalt with increase in weight proportion of cobalt nitrate. SEM analysis shows the surface morphology of the prepared sample and the ferromagnetic behavior of the cobalt ferrite nanoparticle is observed by VSM studies.

Do Chlorhexidine and Probiotics Solutions Provoke Corrosion of Orthodontic Mini-implants? An In Vitro Study.

The aim of this study was to explore the surface roughness and hardness of the implant head of orthodontic mini-implants made from different alloys before and after their in vitro exposure to agents for prevention of gingivitis, mucositis, and peri-implantitis: chlorhexidine and probiotics. Three types of commercially available mini-implants were tested: 316 stainless steel, titanium Grade 5, and titanium Grade 23 (both Ti-6Al-4V alloys with the same atomic weight percentage of Ti, Al, and V, with the difference being in maximal reduction of O2 in Grade 23 to 0.13% of atomic weight). They were immersed in three experimental solutions: artificial saliva, saliva with probiotic bacteria Lactobacillus reuteri, and saliva with oral antiseptic chlorhexidine (CHX). Samples were immersed for 28 days, thermocycled, then stored in an incubator at 37°C. Surface roughness and microhardness on five samples of each of the three implant types were measured by atomic force microscopy and the Vickers method, respectively. Exposure of titanium implant Grade 5 to probiotics significantly increased roughness compared with other media (P < .005). Exposure to CHX significantly increased the roughness of steel implants (P < .05). Neither saliva, probiotic, nor CHX altered microhardness of titanium implants significantly. In steel implants, the exposure to CHX and probiotics decreased microhardness compared with unexposed implants (P < .031), but not in comparison to saliva. Probiotics seem to increase roughness of titanium mini-implants, while CHX seems to increase roughness of steel mini-implants. Only stainless steel implants had an altered, decreased hardness after exposure to CHX, although the same was found after their exposure to saliva. For patients undergoing orthodontic treatment with temporary anchorage units, CHX could be recommended for titanium, and probiotics for stainless steel mini-implants in oral-hygiene maintenance.

Preparation and Characterisation of PVA+TiO2 Nanofiber by Electrospinning Technique

In the present work PVA+TiO2 nanofibers were prepared by electrospinning technique. Structural and Functional groups were carried out by X-Ray diffraction and FTIR technique. The optical analysis was analysed by UV-DRS and Photoluminscence studies. Morphology and compositional were characterized by FESEM and EDS analysis. From Structural analysis shows PVA+TiO2 anatase crystal structure and crystallite size are nanometers. The FTIR technique was used to find out the functional groups present in the prepared set of samples. The optical analysis shows above 70% transparency in the visible region. From the PL analysis titanium and oxygen vacancies are found to be 375 and 526 nm. FESEM analysis of the annealed samples shows the uniformity of nanofibers without any beads which is attributed to the interaction of TiO2 particles with the PVA matrix. From the compositional analysis, the atomic weight percentage of Ti and O increases with the TiO2 loading in PVA.

Dietary addition of zinc-methionine influenced eggshell quality by affecting calcium deposition in eggshell formation of laying hens.

The present study explored the mechanism of Zn-methionine (Zn-Met) influencing eggshell quality of laying hens and investigated whether the mechanism was related to Ca deposition. Hyline grey layers (n 384, 38 weeks old) were divided into four groups: 0 mg Zn/kg, 40, 80 mg Zn/kg as Zn-Met, and 80 mg Zn/kg as zinc sulphate (ZnSO4). Eggshell quality, Zn contents, Zn-containing enzyme activities and expressions of shell matrix proteins in eggshell gland (ESG) were analysed. Zn-Met treatment at 80 mg/kg increased (P < 0·05) egg weight and eggshell strength throughout the experiments. The 80 mg/kg Zn-Met group (P < 0·05) had decreased mammillary knob width and larger relative atomic weight percentage of Ca, stronger signal intensity of Ca in linear distribution and the Ca was more evenly distributed in the transversal surface of eggshell. Zn contents (P < 0·001) in yolk and serum, Ca, albumin (Alb) levels in ESG as well as carbonic anhydrase (CA) activity in serum (P < 0·05) and mRNA levels of CA and Ca-binding protein-d28k (CaBP-D28k) (P < 0·001) in the 80 mg/kg Zn-Met group were the highest among all treatments. In conclusion, shell strength as one of eggshell qualities was mostly related to mammillary cone width in ultrastructure caused by the pattern of Ca deposition in eggshell formation. Also, the increase in Zn-Met-induced Ca deposition may be due to the increased Zn contents in serum and tissues, which were attributable to the increased CA concentrations in serum, Ca, Alb levels and up-regulated CA and CaBP-D28k mRNA levels in ESG.

Cu2+substituted NiFe2O4 thin films via spray pyrolysis technique and their high-frequency devices application

In the present work, Ni1-xCuxFe2O4 thin films were fabricated with compositions of a wide range (0.0 ≤ x ≤ 1.0 in the steps of 0.2) using the spray pyrolysis technique. The prepared thin films were analyzed by using X-ray diffraction (XRD), Raman spectroscopy, field emission-scanning electronic microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), contact angle, UV–visible photo spectrometer (UV) and vibrating sample magnetometer (VSM). XRD analysis show, that all thin films possess cubic spinel structure with Fd3¯m space group. The lattice parameter increased from 8.334 to 8.416 Å with increase in Cu2+ content obeying Vegard's law. The average crystallite size was found in the range of 10–21 nm. The formation of spinel ferrite phase is confirmed through active Raman mode of A1g+Eg+3T2g bands in all thin films using Raman spectroscopy. The grain size obtained from FE-SEM analysis was in the range of 16–26 nm. Using AFM images the average roughness; root mean square roughness skewness and kurtosis were calculated. The stoichiometric chemical composition were confirmed by EDAX analysis and it revealed the presence of O −2, Cu2+, Ni2+, and Fe3+ elements with desired atomic weight percentage of the films. The energy band gap (Eg) obtained from UV spectrum varies from 2.24 eV to 2.03 eV as a function of Cu2+. The M-H curves showed that, the saturation magnetization (Ms) linearly decreased and coercivity increases with increase in Cu2+ content which related can be to the large residual strain, which may induce an additional magnetic anisotropy. The specific electrical resistivity confirmed a good insulating character of the thin films. The dielectric constant decreased with increase in frequency. The present ferrite films can be well suitable for MLCIs operable in the radio frequency range and high frequency device application.

Erbium-doped nanoparticles/films for enhancing percentage photodegradation of direct red-31 dye

Nowadays, the demand for synthetic dyes has grown manifold as there are being widely used in leather, textile, food industries. This paper reports Erbium doped ZnO nanostructured films were deposited on to the glass substrate by a sol–gel spin coating technique. Atomic weight percentage of Erbium was varied from 2.0, 2.5, 3.0, and 3.5 at.wt% namely EZ-1, EZ-2, EZ-3 and EZ-4 and the film characterization were carried out by means of X-Ray diffraction, FESEM, UV–Vis spectrophotometer, Raman spectroscopy, LCR and photoluminescence measurements. XRD result revealed the existence of Er2O3 and ZnO phases for varied Er concentration. FESEM reveals rod-shaped morphology of the film of the order of the size of 40–75 nm. Absorbance and optical band gap was obtained from UV–Vis spectrophotometer. This revealed optical band gap widening with a molar ratio in the range of 3.26–3.32 eV. Raman spectroscopy indicates the tensile stress in Er-doped ZnO films. Photoluminescence intensity near 594 nm indicates more oxygen vacancies which led to high photocatalytic performance. The prepared films were used for photodegradation of DR-31 dye. From the photocatalytic experiment, the degradation percentage was increased with increase in Er concentration up to a molar ratio of 3.0 at.wt%. Thus the optimum molar ratio of the prepared films (3.0 at.wt%) exhibits almost complete degradation of DR-31 dye only in 48 min under UV illumination. The kinetic study reveals the rate constant of nanospheres like particles is 0.07428 min−1. The Er-doped films with different molar ratio result in almost same photocatalytic performance after regular interval of the time. The comparative study of nanoparticles with the film will make for photodegradation of DR-31 dye under same experimental conditions. Despite kinetic study of prepared films were better as compared to bulk form (powder) but the percentage degradation of nanoparticles was found to be better than films.

A comparative study of transport properties of copper doped cadmium selenide thin films at two dopant concentrations

We have explored the effect of Cu dopant concentration on the electrical transport properties of Cu doped CdSe thin films at two concentrations of Cu (at 1 and 5 at.%). Structural, morphological and elemental analysis has been carried out by using X-ray Diffraction (XRD), Scanning electron microscopy (SEM) and Energy Dispersive X-ray analysis (EDX). XRD analysis reveals the hexagonal (wurtzite) structure of nc-CdSe:Cu 1% and nc-CdSe:Cu 5% thin films. EDX analysis determines the atomic weight percentage of Cu in these thin films. SEM studies reveal that the grains are uniformly distributed all over the surface of the substrates for nc-CdSe:Cu 1% and nc-CdSe:Cu 5% thin films. Dark conductivity measurements are made on nc-CdSe:Cu 1% and nc-CdSe:Cu 5% thin films in the temperature range 110–370 K in order to determine the effect of Cu concentration. The obtained results reveal that dark conductivity increases as the Cu dopant concentration increases as compared to undoped nc-CdSe thin films. Dark conductivity graphs show two distinct regions at high and low temperatures with decreasing activation energies. Low temperature data is analyzed using Mott’s variable-range hopping model which indicates hopping in localized states near the Fermi level. Various Mott parameters such as the density of localized states N(EF), characteristic temperature (To), hopping distance (R) and hopping energy (W) near the Fermi level are calculated. The concentration of charge carriers and carrier mobility are calculated for nc-CdSe:Cu 1% and nc-CdSe:Cu 5% thin films by using Hall measurements. Constant photocurrent measurement is also performed on Cu 1% and Cu 5% doped CdSe thin films to determine occupied density of states, Urbach parameter and density of defect states. Obtained results show that occupied density of states increases for nc-CdSe:Cu 5% as compared to nc-CdSe:Cu 1% thin films.

Synthesis and characterization of CuS nanostructures: Structural, optical, electrochemical and photocatalytic activity by the hydro/solvothermal process

The structural, compositional, electronic and luminescent properties of covelite (CuS) have been studied using copper acetate with the thiourea, in the presence of water-butanol and water-cyclohexanol as mixed solvents. The Hexagonal structure of the CuS samples was observed in the X-ray diffraction (XRD) pattern, which is due to different mixed solvents. The CuS bond and atomic weight percentage were identified by the Fourier Transform Infrared (FT-IR) and Energy Dispersive X-ray (EDX) studies. The Scanning Electron Microscope (SEM) of CuS particles revealed the rod and flake shaped morphologies for water-butanol, and water-cyclohexanol, respectively. The bandgap energies of CuS nanostructures were calculated from the UV–Visible (UV–Vis) absorption spectra, and optical band energy curve. The UV and visible emission bands were observed from the PL spectra; this was due to the sulfur vacancy defects. From the CV study, it was found that the water-cyclohexanol assisted CuS sample has enhanced electrochemical properties than water-butanol assisted CuS sample. From the efficiency of the catalysts, the percentage degradation of the cango red (CR) dye was estimated from the mixed solvents assisted CuS samples.

Growth of Cu2ZnSnS4 absorber layer on flexible metallic substrates for thin film solar cell applications

In this work, Cu2ZnSnS4 (CZTS) absorber layers were fabricated using a two-stage process. Sequentially deposited Cu–Zn–Sn thin film layers on metallic foils were annealed in an Ar+S2(g) atmosphere. We aimed to investigate the role of flexible titanium and molybdenum foil substrates in the growth mechanism of CZTS thin films. The Raman spectra and X-ray photoelectron spectroscopy analyses of the sulfurized thin films revealed that, except for the presence of Sn-based secondary phases, nearly pure CZTS thin films were obtained. Additionally, the intense and sharp X-ray diffraction peak from the (112) plane provided evidence of good crystallinity. Electron dispersive spectroscopy analysis indicated sufficient sulfur content but poor Zn atomic weight percentage in the films. Absorption and band-gap energy analyses were carried out to confirm the suitability of CZTS thin films as the absorber layer in solar cell applications. Hall effect measurements showed the p-type semiconductor behavior of the CZTS samples. Moreover, the back contact behavior of these metallic flexible substrates was investigated and compared. We detected formation of cracks in the CZTS layer on the molybdenum foils, which indicates the incompatibility of molybdenum's thermal expansion coefficient with the CZTS structure. We demonstrated the application of the magnetron sputtering technique for the fabrication of CZTS thin films on titanium foils having lightweight, flexible properties and suitable for roll-to-roll manufacturing for high throughput fabrication. Titanium foils are also cost competitive compared to molybdenum foils.

Experimental and Theoretical Investigation of Ferromagnetism in Mn-Doped SnO

In this paper, Mn doped SnO nanomaterial is studied both experimentally and theoretically. Hexagonal-shaped Mn-doped SnO nanostructures are successfully synthesized by the simple template-free hydrothermal method. All theoretical results are calculated using ADF-BAND 2012.01. The experimental and the theoretical results prove the ferromagnetism of Mn doped SnO. The morphology, crystalline phase, particle sizes and atomic weight percentage of atoms are investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDS), respectively. FESEM results show that the sheets-like SnO structure are in the range of 10 mu m and the average size of nano-hexagonal plates is about 100 nm. The average crystalline size of the tetragonal phase SnO particles is calculated to be about 25 nm from XRD results. Two Raman active modes A(1g) = 205 cm(-1) and B-1g = 106 cm(-1) and about 7 cm(-1) redshift are observed by the Raman spectroscopy. The experimental results are consistent with theoretical results.

Deployment of aligned ZnO nanorod with distinctive porous morphology: Potential scaffold for the detection of p-nitrophenylamine

The low temperature solution method was employed to synthesize aligned nanoporous zinc oxide (ZnO) nanorods (NRs) on fluorine doped tin oxide (FTO) glass and applied as an electron mediator for the fabrication of high-sensitive chemical sensor towards the detection of p-nitrophenylamine (p-NPA) in an aqueous medium. Well-crystalline ZnO nanorods with nanoporous morphology were arranged vertically on the FTO substrate. The aligned nanoporous ZnO NRs thin film presented the good aspect ratio of Zn and O elements in terms of atomic weight percentage. The cyclovoltametry and amperometry analysis deduced the rapid electrocatalytic activity of aligned nanoporous ZnO NRs electrode towards p-NPA chemical. The aligned nanoporous ZnO NRs electrode was used to fabricate p-NPA chemical sensor which showed significantly high and reproducible sensitivity of ∼184.26μAmM−1cm−2 with a short response time ≥8s. The fabricated p-NPA chemical sensor exhibited reasonable detection limit of ∼53.7μM and good linearity in the range of 5–20μM with the correlation efficient of R=∼0.97569.

Effect of Deposition Parameters &amp; Molybdenum Percentage on Nickel-Molybdenum Alloy Coatings

The use of Potassium-phosphate baths for the alloy deposition of Nickel–Molybdenum is recently proved equally good as Sodium-citrate baths. The coatings so obtained from Potassium-phosphate baths were examined for atomic weight percentage of Molybdenum. The variation in weight percentage of Molybdenum was obtained by varying different plating parameters like - molar ratio, current density range, and potential range. The observed co-deposited Molybdenum Atomic percentage variation in alloy was investigated for grain size, porosity in structure and surface roughness. The results revel that Molybdenum Atomic percentage in the Nickel–Molybdenum alloy has effect on porosity and surface roughness. It was also found that root mean square value of surface roughness was not only affected by the Molybdenum Atomic percentage but also by potential at relaxation time (TOFF) potential.

Effect of Cu incorporation on structural and optical properties of nanocrystalline CdSe (nc-CdSe:Cu) thin films

nc-CdSe:Cu 1% and nc-CdSe:Cu 5% thin films have been deposited on glass substrates by thermal vacuum evaporation using the Inert Gas Condensation (IGC) method. Transmission Electron Microscopy (TEM) analysis reveals that the particles are spherical in shape and average particle size increases as the Cu concentration increases. The atomic weight percentage of Cu is determined by the Energy Dispersive X-ray analysis (EDX). X-ray Diffraction (XRD) measurements indicate that the films exhibit hexagonal structure. The grain size calculated from XRD increases as the Cu concentration is increased to 5%. The optical band gap Egopt has been determined from the absorption coefficient values using the Tauc’s procedure. A decrease in the band gap is observed with increase of the Cu concentration. The refractive index (n) is determined from transmittance using the Swanepoel’s method. The refractive index is found to depend on Cu concentration. The Photoluminescence (PL) spectral variation at different concentrations of Cu is studied.

Temperature and Composition Dependence of Electrical Conductivity of Ge10Se90-xBix (x=0, 2, 4, 6, 8, 10) Chalcogenide Glasses

Electrical conductivity of Ge10Se90-xBix(x=0,2,4,6,8,10) glassy systems prepared by melt quenching technique has been studied at different temperature in bulk form through I-V characteristic curves. It has been observed that the electrical conductivity increases as the Bi concentration increases up to 4 atomic weight percentages and on further addition of Bi it reduces. The variation in electrical conductivity with Bi concentration is attributed to the Se-Bi bond concentration. Using the Arrhenius equation of conductivity, the activation energy of conduction is evaluated. The effect of Bi concentration on activation energy has also been studied. It is quite evident from results that Poole-Frankel and Rechardson-Schottky conduction mechanism hold good for conduction in these glasses.

Crystal plasticity and multiscale modelling of superalloy creep

A crystal plasticity approach for superalloy creep has been presented which employs a finite element-based representative volume element (RVE) methodology. The γ channels are assumed to undergo crystal slip and the γ′ particles to deform elastically. A range of superalloys has been studied. Thermocalc computations provide the γ′ volume fraction and an automated scheme for generating the resulting RVE has been developed. It has been shown that primary creep response in a wide range of superalloys over high stress, low temperature regimes is represented excellently by the model, by determination of just an activation energy and an alloying element density. It has been hypothesised that the transition from primary to secondary creep results from the development of geometrically necessary dislocations within the γ channels at the γ′ interfaces. Without the need of further material parameters, it has been shown that secondary creep rates over a broad range of stress and temperature can be accurately predicted, hence supporting the hypothesis. An empirical relationship has been established between the alloying element density and the atomic weight percentages of the alloying elements, using a range of superalloy data. It is hypothesised that a role of the alloying elements within the γ channels is to act as inhibitors of ribbon dislocation motion, hence leading to the large range of macro-level primary and secondary creep responses observed in the alloys with variations in constituent alloys. The empirical relationship established, when combined with the crystal RVE methodology, then allows the prediction of superalloy creep rates from knowledge of alloying constituents.

Preparation and Characterization of Hybrid Materials of Epoxy Resin Type Bisphenol A With Silicon and Titanium Oxides by Sol Gel Process

Hybrid materials were synthesized from epoxy resins as a result bisphenol type A-silicon oxide and epoxy resin bisphenol type A-titanium oxide were obtained. The synthesis was done by sol-gel process using tetraethyl orthosilicate (TEOS) and titanium isopropox- ide (ITi) as inorganic precursors. The molar ratio of bisphenol A to the inorganic precursors was the studied variable. The materials were char- acterized by thermal analysis, infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDAX). The hybrid nature of the materials was demonstrated through thermal analysis and infrared spectroscopy. In both systems, as the amount of alkoxide increased, the bands described above were more defined. This behavior indicates the interactions between the resin and the alkoxides. Hybrids with TEOS showed a smoother and ho- mogeneus surface in its entirety, without irregularities. Hybrids with titanium isopropoxide had low roughness. Both TEOS and ITi hybrids showed a decrease on the atomic weight percentage of carbon due to a slight reduction of the organic part on the surface.