Optimization of process parameters by Taguchi method in the recovery of lactose from whey using sonocrystallization

Anti‐solvent crystallization of lactose in the presence of ultrasound will reduce crystal size and the level of agglomeration as compared to the commercial cooling crystallization. It offers a potential route to enhance the physical properties as well as the rapid recovery of lactose. Since lactose recovery itself can reduce biological oxygen demand of whey by more then 80%, recovery of lactose from dairy waste stream (whey) solves the problems of dairy industries by improving economics of whey utilization and pollution reduction. In the present study, recovery of lactose from partially deproteinated whey using an anti‐solvent (acetone) by sonocrystallization was optimized for finding the most influencing operating parameters; such as sonication time, anti‐solvent concentration, initial lactose concentration in the whey and initial pH of sample mixture at three levels using L₉‐orthogonal method. The responses were analyzed for recovery of lactose from whey. The anti‐solvent concentration and the sonication time were found to be most influencing parameters for the recovery of lactose and the recovery of lactose was found to be 89.03% at the identified optimized level. The crystal size distribution of recovered lactose was found to be narrower (2.5 – 6.5 μm) as compared to the commercial lactose crystals (3.5 – 9.5 μm). (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystallographic,optical and magnetic properties of Co‐doped ZnO thin films synthesized by sol gel route

ZnO thin films with various Co doping levels (0%, 1%, 3%, 5%, 8%, respectively) have been synthesized by sol gel spin coating method on glass substrates. XRD and XPS studies of the films reveal that cobalt ions are successfully doped into ZnO crystal lattice without changing the hexagonal wurtzite structure. The morphologies are studied by SEM and AFM and show wrinkle network structures with uniform size distribution. With Co doping concentration increasing, the wrinkle network width decreases gradually. The transmittance spectra indicate that Co doping can effectively reduce the optical bandgap of ZnO thin films. Photoluminescence show that all samples have ultraviolet, violet and green emission. When Co doping concentration increases up to 5%, the intensity of violet emission is greatly increased and a strong deep blue emission centered at 439 nm appears. The ferromagnetism of all samples was observed at room temperature. The emission mechanisms and ferromagnetism origination are discussed in detail. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation of undoped and indium doped ZnO thin films by pulsed laser deposition method

An original modification of the standard Pulse Laser Deposition (PLD) method for preparing both undoped and indium doped zinc oxide (ZnO:In) thin films at low substrate temperature is proposed. This preparation method does not demand any further post‐deposition annealing treatment of the grown films. The developed method allows to grow thin films at low substrate temperature that prevents them from the considerable loss of their intrinsic electrical and optical properties. The influence of deposition parameters on the electrical and optical parameters of the undoped and the indium doped ZnO thin films is also analysed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Properties of Co‐doped ZnO films prepared by electrochemical deposition

We prepared Co‐doped ZnO films by the electrochemical deposition. X‐ray diffraction (XRD), high resolution transmission microscopy (HRTEM), x‐ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), x‐ray absorption near‐edge structure (XANES), vibrating sample magnetometer (VSM), optical absorption, and photoluminescence (PL) measurements were carried out on the samples. The results showed Co atoms substituted Zn atoms in the ZnO lattice without the formation of the impurity phase. VSM measurements showed the ferromagnetic properties for the Co‐doped ZnO samples. When the Co doping concentration increased, the band gaps were widened and the PL peak positions shifted towards the short wavelength direction. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical studies on ZnO films prepared by sol‐gel method

A standard sol‐gel method was used to deposit ZnO thin films of suitable thickness on glass substrate.The optical characteristics of the visible to infrared range on thermal stress were critically observed. Morphological signature of the films was detected by X‐ray diffraction (XRD) and the crystallite size determined by Scherrer method from XRD data were consistent with grain size estimated from spectroscopic data through Meulenkamp equation. The optical band gap value from the transmission spectrum was found to corroborate with the existing works. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Properties of InAs co‐doped ZnO thin films prepared by pulsed laser deposition

InAs co‐doped ZnO films were grown on sapphire substrates by pulsed laser deposition. The grown films have been characterized using X‐ray diffraction (XRD), Hall effect measurements, Atomic force microscope (AFM) and Field emission scanning electron microscope (FESEM) in order to investigate the structural, electrical, morphological and elemental properties of the films respectively. XRD analysis showed that all the films were highly orientated along the c‐axis. It was observed from Hall effect measurements that InAs co‐doped ZnO films were of n‐type conductivity. In addition, the presence of In and As has been confirmed by Energy dispersive X‐ray analysis. AFM images revealed that the surface roughness of the films was decreased upon the co‐doping. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

In掺杂量对ZnO薄膜微结构和光学性质的影响

采用溶胶-凝胶法分别制备未掺杂和In掺杂ZnO薄膜,用X射线衍射仪、扫描电镜和紫外可见分光光度计测试分析薄膜的微结构、表面形貌和光学性质.结果表明:In掺杂ZnO薄膜仍为六角纤锌矿结构,但In的掺入抑制ZnO薄膜的结晶,使得薄膜的结晶度降低.In掺杂ZnO薄膜表面呈网络状结构,随着In掺杂量的增加,表面起伏程度减小,空隙减少,表面平整,致密度提高.In掺杂ZnO薄膜的光学带宽Eg值均小于未掺杂ZnO薄膜,且随In掺杂量的增加先增大后减小,并用Burstein-Moss效应和缺陷浓度变化对光学带宽变化进行了解释.     

Structural and optical properties of Mg‐doped ZnO thin films prepared by a modified Pechini method

ZnO thin films with different Mg doping contents (0%, 3%, 5%, 8%, 10%, respectively) were prepared on quartz glass substrates by a modified Pechini method. XRD patterns reveal that all the thin films possess a polycrystalline hexagonal wurtzite structure. The peak position of (002) plane for Mg‐doped ZnO thin films shifts toward higher angle due to the Mg doping. The crystallite size calculated by Debey‐Scherrer formula is in the range of 32.95–48.92 nm. The SEM images show that Mg‐doped ZnO thin films are composed of dense nanoparticles, and the thickness of Mg‐doped ZnO thin films with Mg doped at 8% is around 140 nm. The transmittance spectra indicate that Mg doping can increase the optical bandgap of ZnO thin films. The band gap is tailored from 3.36 eV to 3.66 eV by changing Mg doping concentration between 3% and 10%. The photoluminescence spectra show that the ultraviolet emission peak of Mg‐doped ZnO thin films shifts toward lower wavelength as Mg doping content increases from 3% to 8%. The green emission peak of Mg‐doped ZnO thin films with Mg doping contents were 3%, 8%, and 10% is attributed to the oxygen vacancies or donor‐acceptor pair. These results prove that Mg‐doped ZnO thin films based on a modified Pechini method have the potential applications in the optoelectronic devices.     

Effect of heat treatment on corrosion properties of mixed sol gel silica-titania (7-3) coating

In this paper, the sol-gel method has been used for preparing silica-titania coats with a molar ratio of 7:3 on TiNi that were heat treated at 300 °C and 500 °C. For studying and investigating the property of corrosion and microstructure of coats; SEM (scanning electron microscopy), EIS (electrochemical impedance spectroscopy), polarization dynamic and roughness measurement have been used and XRD (X-ray diffraction) has been also used for characterizing the coats. Heat treatment at 500 °C caused the increase of porosity and coating cracking that finally caused the decrease of corrosion resistance. The best corrosion resistance was achieved for the sample that was heat treated at 300 °C. The structure of the heat treated sample at 300 °C was amorphous and the increase of temperature of heat treatment from 300 °C to 500 °C caused crystallization and decrease of the corrosion resistance. Crystallization affected both corrosion resistance and surface roughness.     

Structural and optical properties of TiO2:SnO2 thin films prepared by sol gel method

ABSTRACT

TiO₂:SnO₂ thin films were deposited on glass substrates, by using sol gel spin coating method with different ratio (3%, 5% and 7%) at 3200 rpm, to study their effect on different properties of TiO₂: SnO₂ thin films. The structural and optical properties of films have studied for different ratio. These deposited films have been characterized by various methods such as X-Ray Diffraction (XRD), Ultra Visible spectroscopy. The (XRD) can be used to identify crystal structure of as deposited films. The Transmission spectra have shown the transparent and opaque parts in the visible and UV wavelengths.     

助熔剂法生长ZnO晶体

采用Bi4B2O9、CdB2O4和BaB2O4为助熔剂,获得了毫米级的氧化锌单晶.Muiliken的电负性理论和Viting的平均轨道电负性提供了一个选择晶体生长所采用的助熔剂的有效方法.实验结果表明ZnO晶体的生长温度比文献报道的均低,从而有效地减少了ZnO以及助熔剂的挥发.本文给出了几种有望获得大尺寸ZnO单晶的助熔剂.     

Structure and optical properties of Mg‐doped ZnO nanoparticles by polyacrylamide method

Mg‐doped ZnO (Mg_xZn_1‐xO) nanoparticles with precise stoichiometry are synthesized through polyacrylamide polymer method. Calcination of the polymer precursor at 650 °C gives particles of the homogeneous solid solution of the (Mg_xZn_1‐xO) system in the composition range (x < 0.15). ZnO doping with Mg causes shrinkage of lattice parameter c. The synthesized Mg_xZn_1‐xO nanoparticles are typically with the diameter of 70–85 nm. Blue shift of band gap with the Mg‐content is demonstrated, and photoluminescence (PL) from ZnO has been found to be tunable in a wide range from green to blue through Mg doping. The blue‐related PL therefore appeared to be caused by energetic shifts of the valence band and/or the conduction band of ZnO. Mg_xZn_1‐xO nanoparticles synthesized by polyacrylamide‐gel method after modified by polyethylene glycol surfactant have a remarkable improvement of stability in the ethanol solvent, indicating that these MZO nanoparticles could be considered as the candidate for the application of solution–processed technologies for optoelectronics at ambient temperature conditions.     

Facile fabrication of porous ZnO by a template free method

In this paper, a template free method has been employed to fabricate porous ZnO. Brick shaped precursor was first synthesized by a mild hydrothermal process. Accompanied with the decomposition of the precursor during the subsequent annealing treatment, porous ZnO with the inherited morphology of the precursor was obtained. The as‐prepared products were characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). It exhibited that the porous hierarchical frame consists of nano‐sheets with wurtzite‐type. The size of the pores as well as the size of the particles varied with the annealing temperature. Mechanism speculation showed that the crystal‐aggregation in the growth process of the precursor is the key to the establishment of pore structure. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical investigations on the existence of phase transition in ZnO:Li thin films prepared by DC sputtering method

We investigated the effect of temperature on the absorption spectra of Zn_0.8Li_0.2O thin films (ZnO:Li), deposited at 573 K, in the wavelength range 190‐800 nm. The films were deposited on sapphire, MgO or quartz substrates by DC sputtering method. The results show a shift of the optical energy gap (E_g), with direct allowed transition type near the fundamental edge, to lower wavelengths as the temperature increases. The temperature rate of E_g changes considerably showing an anomaly around 320 K depending on type of substrate. The founded results indicated that replacement of Zn ions with Li ions induces a ferroelectric phase in the ZnO wurtzite‐type semiconductor. The exponential dependence of the absorption coefficient on the incident photon energy suggests the validity of the Urbach rule. (© 2007 WILEY ‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structure and magnetism of ZnO/Co multilayers prepared by pulsed laser deposition

ZnO/Co multilayers were fabricated on silicate (100) substrate by a pulsed laser deposition method at room temperature. The x‐ray diffraction (XRD) results reveal that the as‐deposited multilayer film is composed of amorphous phase, which leads to high saturation magnetization and low coercivity. Higher coercivity is observed in the ZnO/Co films annealed at 390 °C due to the formation of crystalline metallic Co and semiconducting ZnO. But much higher annealing temperature leads to the oxidation of metallic Co and the reaction between Co and ZnO, which decreases the saturation magnetization and coercivity obviously.     

Optical and structural characterisation of zinc oxide thin films prepared by sol‐gel process

Zinc oxide thin films have been prepared on different substrates by the sol‐gel method using 2‐methoxyethanol solution of zinc acetate dihydrate stabilized by monoethanolamine. The photoluminescence spectra of the films show the band‐edge and sub‐band transitions. The intensity of the band edge emission peak increases, while the intensity of the deep level emission peak decreases in the films coated on sapphire substrate. Transmittance spectra show that the films are transparent beyond 400 nm. The structural property of the films has been evaluated using X‐ray diffraction. The X‐ray peak intensity of the film (002) grown on sapphire substrate is higher than the films grown on glass and quartz substrates. The AFM images show improvement in the surface of the annealed films as compared to the as‐grown ZnO films coated on sapphire substrates. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of nanosized TiO2 powder by sol gel method at low temperature

ABSTRACT

Nanotechnology is all about making products from very small constituents, components or subsystems to gain greatly enhanced material properties and functionality. Nanocrystalline anatase TiO₂ was prepared by a facile sol–gel route at a temperature of 50°C under mild conditions. Titanium tetraisopropoxide (TTIP) was used as a titanium precursor, and 2-propanol was used as a solvent. XRD, TEM, SEM, FT-IR and BET were applied to characterize the crystal phase. The Crystalline size of TiO₂ powder has been obtained with diameter < 30 nm for anatase at 500°C using an acid.     

Surface‐morphology evolution of ZnO nanostructures grown by hydrothermal method

Surface‐morphology evolution of ZnO nanocrystals has been observed by the hydrothermal process. The effects of stirring time and ammonia content on the morphology evolution have been discussed, respectively. Extension of stirring time of the precursor results in morphology transformation from star‐like to wire‐like ZnO nanocrystals. ZnO nuclei aggregation and uniform Zn(OH)₂ precipitation can readily explain these two morphologies, respectively. By increasing the ammonia content in the solution, the morphology of ZnO crystals is transformed from an irregular shape to hexagon sheets to nanorods, and the side length of ZnO crystals is decreased accordingly. Hollow structures are realized at the subsequent solution aging process. Variation of zinc ammonic complex and minimum surface energy can well explain the morphology evolution of ZnO nanostructures.     

Sintering behavior of ZnO:Al ceramics fabricated by sol‐gel derived nanocrystalline powders

ZnO:Al ceramics (Zn:Al, 0.95:0.05) were prepared by using sol‐gel derived nanocrystalline powders. XRD patterns of the doped ceramics revealed the existence of both zincite (JCPDS 36‐1451) and gahnite (JCPDS 5‐0669) phases. Gahnite phase (ZnAl₂O₄) was segregated along the ZnO grain boundaries. At the sintering temperature of 1200 °C, relative density of the undoped and Al doped ceramics were measured as 0.695 and 0.628, respectively. Both grain size and relative density of the ceramics decreased with Al doping. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)