DS Process Research Articles

Fabrication of all-starch-based hydrogels as eco-friendly water-absorbent resin: Structure and swelling behaviors

Water-absorbent resin has gained wide applications due to the capability in absorbing and retaining substantial amounts of water, while it's a challenge to fabricate a full biobased water-absorbent resin with excellent biodegradability and eco-friendliness. In this study, starch was sulfonated (SS) and crosslinked with epichlorohydrin to fabricate all-starch-based hydrogels (SSH) as water-absorbent resin with advantages of intrinsic biodegradability and low cost. The results confirmed that the hydrogen atoms of -OH groups in starch chains were partially replaced by -SO3− and the substitution degree (DS) of SS reached 0.008–0.344. By controlling DS and gelation process of SS, the swelling ratio (Qe) of SSH was improved in distilled water, reaching 244.47 g/g for samples prepared using SS with medium DS (SSMDSH). SSMDSH showed relatively loose network structure with low cross-linking density and large pore size. Meanwhile, -SO3− groups on SSMDSH chains facilitated strong ion-dipole interactions with water molecules, resulting in an increase in content of non-freezing bound water within hydrogels and thus improvement in water absorption capacity. Besides, SSH showed desired fertilizer absorption performance and complete biodegradability in α-amylase solution, which made it to be a promising candidate in agricultural fields as eco-friendly water-absorbent resin.

Enhancing multi-crystalline silicon wafer performance through surface modification and AZO treatment

ABSTRACT In the current work, we studied the influence of surface modification on reflectivity and minority carrier lifetime of mc-Si wafer taken from ingot grown by DS process. Two etchants combination namely, KOH/IPA/DI water, and NaOCl/KOH/IPA/DI water are used for different time durations. Reflectance and minority carrier lifetime vary significantly for both etchants used in this work. Optimised micro pyramidal structure formation will aid in enhancing the total internal reflection thereby increasing light absorption. Increase in minority carrier lifetime will be helpful in increasing the efficiency of solar cell. In order to establish the effect of etching on reflectivity of wafers, Al-doped ZnO was sputtered on etched surface and reflectivity was found to decrease further as observed from the reflectivity spectrum. I-V measurements were carried out on Ag/Ti/AZO/mc-Si/Ag and effect of etching on contact behaviour was observed. AZO-coated Si surface with optimised surface micro pyramids served as a good antireflection layer.

Numerical Investigation on Effect of Side Heater Modification on the Stress Distribution and Dislocation Density of Multi-Crystalline Silicon Ingot Grown by DS Process

Numerical Investigation on Effect of Side Heater Modification on the Stress Distribution and Dislocation Density of Multi-Crystalline Silicon Ingot Grown by DS Process

Effect of Argon Flow Rate on mc-Silicon Ingot Grown by DS Process for PV Application: A Numerical Investigation of Non-Metallic Impurities

Effect of Argon Flow Rate on mc-Silicon Ingot Grown by DS Process for PV Application: A Numerical Investigation of Non-Metallic Impurities

Influence of helium gas flow under the retort bottom to control the impurities in grown mc-Si ingot by DS process for photovoltaic application: Numerical simulation

The quality improvement of the mc-Si ingot is achieved by numerical simulation using the finite volume method. We have done the numerical simulation on a 2D symmetric Directional solidification furnace with helium gas flow at the bottom of the retort. In this process, the first nucleation starts at the bottom centre of the crucible due to spot cooling. The spot cooling process achieves the convex melt crystal interface during the growth process. It will push the impurity from the centre to the peripheral region of the ingot. This spot cooling method results show the acceptable range of the dislocation density and stress of the grown ingot. The melt-crystal interface, thermal stress, dislocation density and impurity formation of spot cooling system grown mc-Si have been analysed and compared with the conventional DS system of the grown mc-Si ingot. It is seen from the results that the LID effect, SiC formation and dislocation density are reduced in the spot cooling system grown mc-Si ingot.

Creep characteristics of directionally solidified turbine blades based on the difference in original casting characteristics

Due to the difference between original material and the processed material for use in turbine blades, research that solely focuses on the original materials may not fully explain the performance of operational turbine blades. In order to ensure the maximum utilization rate of turbine blades, the study examines the creep properties and differences of different parts of the directional solidification of original casting turbine blades. In this article, a set of sampling fixtures from different parts of a turbine blade were proposed to quantitatively measure the difference in creep properties caused by the complex geometric factors created during the DS process. The special fixtures would cut the blades into five different parts, which were to be further processed into small samples. Creep tests under two different conditions (980 °C/245 MPa, 980 °C/267 MPa) were carried out. Round rod specimens (standard parts) were used for creep tests under the same conditions for comparison. By employing scanning electron microscopic (SEM) and creep tests on different parts of original casting turbine blades, the mechanism of microstructure evolution and the creep fracture behavior were proposed in this condition. In addition, the original microstructure of different parts of a blade was observed by scanning electron microscopy (SEM), and the characteristics of the different parts were simulated based on an improved two-parameter creep constitutive model. The results suggest that the creep life of the different parts of the original casting blade is different, which caused by the differences in microstructure and morphology of the different parts of the original casting blade. The creep property of standard parts is better than that of original casting blades. The creep life of original casting blades from small to large is as follows: CVS, DP, LE, CCS, TT. An improved two-parameter creep constitutive model was adopted to simulate the difference in creep properties (including creep life) resulted from different parts in a turbine blade. This difference needs to be considered in designing the structure and service life of turbine blades formed by directional solidification. The research results are of great significance for improving the design of directionally solidified turbine blades and for improving the directional solidification forming process.

Transient Simulation on the Growth of Mono-like Silicon Ingot in DS Process Using Crucible with Plano-Concave Bottom for PV Applications

Two-dimensional numerical simulation on axisymmetric directional solidification furnace has been carried out to investigate the growth of mono-like silicon ingot. The silicon ingots were grown in conventional crucible and modified crucibles with Plano-Concave bottom. Four different crucibles with the thickness variation of 5 mm, 10 mm, 15 mm and 20 mm at the bottom center of the crucible were used for the simulation. The thermal field of the grown ingots were analysed during the growth process. The effect of the modification at the crucible bottom on the outward heat flux has been investigated and the melt-crystal interface was analysed during the growth process. The distribution of thermal stress and shear stress in the grown ingots was investigated. The results show that the modified crucible with Plano-Concave bottom gives better melt-crystal interface by enhancing the spot cooling and lead to lower shear stress and lower thermal stress in the grown ingot which can be used for photovoltaic applications.

Impact of viscosity on photo-induced bimodal emission, decay profile and energy transfer in lanthanide based hybrid nanostructure

The effect of viscous media on fluorescence intensity and lifetime of hybrid nanoparticles (HNPs) have been investigated in order to design viscosity sensor. HNPs are developed by using of Eu(TTA)3Phen (ETP) coordination compound and NaGd0.78Er0.02Yb0.20F4 fluoride nanoparticles. Here ETP gives strong emission in orange-red region at 611 nm wavelength by absorbing ultraviolet (UV) {240–450 nm) photons (known as downshifting process, DS) and NaGd0.78Er0.02Yb0.20F4 nanoparticles give strong emission in green region at about 540 nm wavelength by absorbing near-infrared (980 nm) photons (known as Upconversion process, UC). Small amount of HNPs are dispersed in glycerol-water medium (concentratioñ 10−6 M) and its fluorescence intensity and lifetime are monitored. The viscosity of the system is varied by taking different ratios of glycerol (C3H8O3) and distilled water (H2O). The fluorescence intensity of the colloidal solution is measured by exciting it with UV as well as 980 nm diode laser and found enhancement in emission intensity as a function of increase in relative viscosity. Similarly lifetime also increases with the increase in the relative viscosity of the solvent in both DS and UC processes. The viscosity vs emission intensity/lifetime show exponential increment upon increasing glycerol concentrations. Therefore, the HNPs can serves as fluorescent probe for quantitative measurements of the micro viscosity of environment and thus, it could be extremely useful for the study of biological systems.

The Nature of Linguistic Processes Determining the Applicability of Nominalizations Applied to Strings NP-Cop-AP

The article aims at analyzing the principle which determines the acceptability and correctness of nominalizations performed upon sentences of the type: NP-Cop-AP. The discourse was initiated by Chomsky (1972), who demonstrated the fact that the correctness of T NOM is established by processes taking place in SS, thus suggesting that the analysis of SS might shed light on the nature of the underlying DS processes. This view was lated supported by evidence coming from the analysis of the lexical features of NP and AP, carried out by Postal (1974). Thus discussion was initiated as to the role of 'the lexicalist hypothesis' and 'lexicalism' in sentence derivation. The author of the article discusses the validity of 'the lexicalist hypothesis', which maintains that lexical features alone can suffice for the explanation of the acceptability Of T NOM applied to strings NP-Cop-AP. She claims that the resort to the lexical features needs to be made with respect to, as she calls them, elliptic structures, i. e. structures with shifted designations. In the search for the rule determining the correctness of T NOM , the author considers such principles as: Chomskean observation of its dependence upon the 'rough similarity' between SS and DS (Chomsky 1972), Postal's analysis of agentivity (Postal 1974), the role of the antecedent of the implied subject of the infinitive phrase (whenever it is contained in such structures) and, as she calls it, T NOM -over-T NOM principle. The analysis leads to the conclusion that the acceptability of T NOM can be assumed to be determined by the syntactic process. The author names it T NOM -over-T NOM constraint and analyzes it on the selected corpus of English and Polish sentences.

Modelling on Modified Heater Design of DS System for Improving the Quality of Mc-Silicon Ingot

Numerical simulation is an important tool for analyzing and optimizing the multi-crystalline silicon ingot growth process for Photovoltaic (PV) applications. Heat transfer plays an important role in the DS process in which thermal stress, maximum principal stress and maximum shear stress are controlled by temperature gradient in the DS furnace. In this work, the von Mises stress, maximum principal stress, maximum shear stress and dislocation density were simulated for modified shape of side and top heaters. It is observed that the von Mises stress, maximum principal stress, maximum shear stress and dislocation density were reduced in mc- silicon ingot grown by modifying the heater of DS furnace.

Numerical analysis on effect of annealing mc-Si ingot grown by DS process for PV application

Silicon solar cells play a crucial role in Photo voltaic (PV) application. We have numerically investigated thermal stress and normal stress components (Sigma 11, Sigma 22, Sigma 33 and sigma 12) by using finite volume method. The maximum thermal stress has low value at the centre region for 900K and 700K annealing temperatures comparing all the cases. The maximum thermal stress at peripheral region is low for 700K annealing compared to 900K annealing. The annealing effect of mc-Si ingot normal stress components is discussed. At 700K annealing temperature the normal stress in 11 and 33 direction has lower maximum and at the 900K annealing temperature the normal stress in 22 and 12 direction has lower maximum.

Crystal orientation control in TiAl–Nb alloys through a double directional solidification process

Intermetallic Ti–46Al–5Nb (at.%) alloys were directionally solidified by single directional solidification (SDS) process and double directional solidification (DDS) process using a Bridgman directional solidification furnace. Microstructure and crystal orientation neighboring the initial growth interface as well as the quenched mushy zone before starting directional solidification were investigated in the SDS and DDS processes, respectively. The results show that the dendrite morphology changes from equiaxial to columnar, but the directional dendrite segregation is almost keep the continuity across the initial growth interface after SDS and DDS processes, respectively. Crystal orientations in the regions neighboring the initial growth interface have preferential modifications along the growth direction. Compared with that in the first DS of DDS, the length of the initial mushy zone significantly decreases, but the β dendrite is well-orientated in the mushy zone in the second DS. Crystal orientation can be well-controlled in DDS by modifying the β growth morphology as well as the orientation in initial mushy zone of the two DS processes. The directional dendrite parallel to the growth direction and the preferred β orientation are considered as the main reasons to β seed crystallization. The process of the β seed crystallization is also discussed. Based on the β seeding, the DDS process can align the β dendrite orientation and promote the peritectic transformation undergoing completely, thus control the lamellar colony boundaries as well as the lamellar microstructures inside of the colonies.

Corrosion behavior of duplex coatings

The titanium alloys are used in defense, aerospace, automobile, chemical plants and biomedical applications due to their very high strength and lightweight properties. However, corrosion is a life-limiting factor when Ti alloys are exposed to different chemical environments at high temperatures. In the present paper, duplex NiCrAlY/WC–Co coating is coated onto Ti6Al4V substrate to investigate the corrosion behavior of both coated samples and the substrate. The duplex coating was performed with NiCrAlY as the intermediate coat of 200μm thickness deposited by HVOF process and WC–Co ceramic top coat with varying thicknesses of 250μm, 350μm and 450μm deposited by DS process. Potentiodynamic polarization tests were employed to investigate the corrosion performance of duplex coated samples and substrate in Ringer’s solution at 37°C and pH value was set to 5.7. Finally the results reveal that 350μm thick coated samples showed highest corrosion resistance compared to 250μm thick samples as well as bare substrate. However, the 450μm thick coated sample showed poor corrosion resistance compared to the substrate. The scale formed on the samples upon corrosion was characterized by using SEM analysis to understand the degree of corrosion behavior.

Advanced chemical model for analysis of Cz and DS Si-crystal growth

In growing bulk crystals from the melt, impurities contained in silicon feedstock, generated due to the melt-to-crucible contact and transported by the gas flow from graphite elements strongly affect the efficiency of mono and multicrystalline silicon solar cells. The present paper is aimed at developing an advanced coupled chemical model accounting for such phenomena as oxygen and nitrogen solution at crucible wall, oxygen and carbon transport through the melt free surface, formation of Si3N4-, Si2N2O- and SiC-particles in the melt, mass transport of SiO-, CO- and Si-species in argon carrier gas and, finally, formation of parasitic deposits on the furnace units. The model is verified by simulation of DS and Cz Si-crystal growth. It is shown that the computational results agree well with available experimental data, and the model can be used for optimization of Cz and DS processes.

DAMAGE SPREADING ON THE HOMO- AND HETERO-CELL LATTICES WITH COMPETING GLAUBER AND KAWASAKI DYNAMICS

The damage spreading of the Ising model on the homo- and hetero-cell lattices (here the topological hexagonal lattice and the 4–8 lattice) with competing Glauber (G-) and Kawasaki (K-) dynamics is studied and the results are compared. For the homo-cell lattice, we pay attention to the pure K-dynamics or the cases in which the K-dynamics is dominant. We get four main conclusions related to the K-dynamics through our calculations: (1) the damage always spreads as long as Kawasaki dynamics is dominant during the competition of two dynamics; (2) the relation for the saturation damage, 〈s〉∞ = 0.5, holds for K-dynamics whatever the updating rules are; (3) 〈s〉∞ = 0.5 is independent of the structures of the system; (4) the DS process under pure K-dynamics converges very slowly, especially for T = 0 K-dynamics. For the hetero-cell lattice, we are interested in the long-range interaction between spins and the different interaction strength for the spins in the hetero-cells. To include the long-range spin interaction, we consider the spin interactions up to next-nearest neighbors. It is shown that the inclusion of the next-nearest-neighbor interaction enhances the transition temperature greatly. The explanation and discussion for the results are presented.

Peculiarities of ds realignment processes in Cu-and Cr-doped TGS crystals

Abstract A study of the polarization reversal processes in TGS crystals doped by both Cu and Cr ions is presented. It is shown that Cr ions manifest themselves as active additives and their effect on polarization reversal processes is stronger as compared with Cu ions. At the same time Cu ions improve the polarization reversal characteristics of TGS.