Hội nghị khoa học lần thứ 20 = Proceedings of the 20th scientific conference Hanoi University of technology. Phân ban. Công nghệ hoá vô cơ = Section. Chemical technology. Hanoi, 2006

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A new method of surface treatment for aluminium-magnesium alloy to improve the durability of the bonding joint: This contribution considers the influence of different surface pre-treatments including self assembly of phosphoric acid mono alkyl ester as adhesion promoter (AP) for adhesive bonding of aluminium alloy AlMg3. The investigations were performed using a cold hardening two components epoxy-adhesive. The pre-treated surfaces, the interphase structures and the joints were characterized by: scanning electron microscopy (SEM/EDX), surface tension, X-ray Photoelectron Spectroscopy (XPS), electrochemical impedance spectroscopy (EIS); (dynamic mechanical analysis DMA) and the determination of mechanical parameters. The results interestingly show that the test sample with three step surface treatment (degreasing in aceton, then anodic oxidation in phosphoric acid and adsorption of AP) has the highest adhesive strength and durability. This surface treatment method could be proposed as alternatives to chromium based pretreatments for aluminium.
A study of recovery of nickel from slag of blast furnace manufacturing fused calcium phosphate fertilizer: The blast furnace slag mainly contains Fe3P.Fe2P, metallic nickel and several different elements such as aluminum, phosphor, oxygen, and sulfur. The weight increase after calcining the slag at 1000oC is 38%. The separation of nickel from the slag includes the following the steps: (1) grinding and heating the slag, at 800oC, (2) dissolving in hydrochloric acid and heating the solution to dryness in order to decompose iron chloride and (3) dissolving the residue in water and selective precipitating of nickel from the obtained solution which mainly contains nickel and a small amount iron undecomposed at the above step.
A study of synthesis of the ZnS phosphor activated by manganese: The synthesized ZnS phosphor activated by manganese has a high luminescent intensity with a red light at the 598nm wavelength. The phosphaor of ZnS with a hecxagonal structure and manganese zinc sulfide with a cubic structure and the composition of Mn0,08Zn0,92S. There is a transformation from manganese zinc sulfide with the above composition into Mn0,08Zn0,92S when annealing the synthesized sample in the nitrogen atmosphere at the temperature of 500oC in 60 minutes, and this decreases the luminesece.
A study of the ability of non-rotating screen patterns in the reproduction of color images in offset printing: This paper presents the results of the ability of non-rotating screen patterns in the reproduction of color images in offset printing, in comparison with conventional rotating. The study indicates a continue development to resolve this matter.
A study of the preparation of pigment particles covered by film-forming polymers that are applied for water based inks: The pigments covered by film-forming polymers have opened a prospect to improve the quality of water-based printing inks. In this study such pigments were prepared by the initiated polymerization of styrene and methacrylate derivative monomers in the aqueous pigment dispersions. The formation of polymer films covering pigment cores depends on the polymerization time. At the time of 4 hours almost pigment particles are coated by the polymer. The formed polymer covers of pigments have the average thickness of 5. 95 nm. This result is appropriate to improve dispersion stability of pigments along with a guarantee for the optical colour.
A study on cerium salt for inhibition of mild steel in water environment: This paper deals with the study of Ce3 compound (CeCl3) as a non-toxic alternative to chromate for inhibition of mild steel in neutral water environment. Corrosion rates of mild steel in water with various concentrations of Ce3 were determined. Electrochemical and non-electrochemical techniques have been used, such as linear polarization, potentialdynamic, EIS, weight-loss-test,... The optimal concentration of the inhibitor are 500 ppm.
A study on the chemical kinetics of the acid hydrolysis of the chitosans: The chemical kinetics of the hydrolysis of the 1,4-glycosidic linkages (depolymerization) and the N-acetyllinkage (de-N-acetylation) chitosans in diluted HCl were investigated. The obtained preparation were character by IR The rate of hydrolysis of the glycosidic linkages was found to be equal to the rate of de-N-acetylation in dilute acid. This can be explained by assuming that the hydrolysis of the N-acetyllinkage is a S2n reaction, while the hydrolysis of the glycosidic linkages is a SN1 reaction. The present study allow us to control the desire prepared chitosan to reach standard applied in pharmaceutical products.
Absorption and mechanism of CO oxidation vapour over nanocomposited catalyst Au/CeO2: Nanostructured Au-Ceria has been known as a promising catalyst of the low-temperature water-gas shift reaction. The catalyst prepared by coprecipitation method from Ce(NO3)3 1M (Merck) and HauCl4 0,5M (Merck) solutions by pH=6,5-7 at 60oC with the gold loading various between 0,75 and 12,58 atomic percent has been used to study absorption of CO and H2O mechanism of CO oxidation on the catalyst during reaction.
Accelerated weathering tests from steel with organic coating used in Vietnam: The choice of test regime is based on standard test conditions similar to the real ones is a decisive factor in approximate prediction of service life time of product. This research was performed to choose the suitable accelerated weathering testing regime in order to predict more exactly the real durability of the organic coating material on the steel for hot and humid climate of Vietnam. By the combination of the many yeas climatic data treatment and the accelerated testing results on three kinds of paint, the suitable accelerated testing cycle was proposed. Every each 24 hour testing cycle consists of 4 hours of salt spray, 8 hours of ultraviolet irradiation, 4 hours of exposure in the high humid environment and 8 hours of natural drying condition.
Building an equation to determine phase equilibrium constant: A experimental method of building equations is introduced to correlate K on pressure P and temperature T based on phase equilibrium datum that frequently present in form of table or diagrams.
Characterization, magnetic property of nanocrystalline BaFe12O19 prepared by hydrothermal method: Nanocrystalline BaFe12O19 with average grain size of 7.8-15.3 nm has been successfully synthesized by hydrothermal method. X-ray diffraction and energy depressive X-ray spectroscopy measurements show that the obtained materials are formed of single-phase particles with a perfect chemical purity and a correct stoichiometric ratio. The average particle size of nanocrystals depends on the preparation temperature and preparation time. From the transmission electron microscope images, we observed that the materials are composed by both stick-like and plate-like particles, which can be separated by using a centrifugation with appropriate rotations number and solvent. The preliminary results from VSM technique showed that the magnetic properties depend on the size of particles.
Comparative study of electrodeposited iron (Fe) and permalloy (80Ni20Fe) thin films with Giant Magnetoimpedance (GMI) effect: The structure and giant magnetoimpedance effect (GMI) of electrodeposited onto quartz substrate iron (Fe) and permalloy (Ni80Fe20) films were investigated by use of electro scanning microscope (SEM), X-ray diffraction (XRD) and magnetic measurement. The giant magnetoimpedance ratio MIR in the Fe-Ni deposited film is larger than those of Fe film. Heat treatment at 450oC during 60 minutes causes increasing MIR of Fe-Ni film from 7% to 20%.
Corrosion resistance of alminum-silicon alloys in a coolant system of heavy-truck engines: Corrosive resistance of aluminum alloys of a coolant system of heavy truck engines was investigated in solutions containing ethylene glycol and carboxylates serving as inhibitors. Due to the presence of these additives, the structure of the passive film on the aluminum-silicon alloy (7% by weight) is more compact as increasing pH values. The corrosion potential of a working electrode is shifted in an anodic direction also, from-0,591 V up to -0,435 V. It was found that the passive film is most durable at the pH value ranging from 9 to 11, with corrosion rate of about 10-6 mpy (metre per year).
Dependence between the structure and temperature resistance of the alumino-phosphate materials: Inorganic polymers based on alumina and phosphorus have been known as the surface coating with high temperature resistance and many other excellent chemical and physical properties. By modifying composition of elements in the framwork structure can be obtained alumino-phosphate materials with different characterizations. This study focus on the dependence between the structure and temperature resistance of this material.
Describing the gasification of rice husk in the with immovable grains fluidbed by the physical model: The prosess for gasification of rice husk in the with immovable grains ftuidbed is dependent on many factors, for instance: mass of the rice husk, mass of the immovable grains, velocity of gas, temperature of the gasification,... A physical modeljor describing this process is established. The parameters of this model are determined by experiments.
Direct nickel electroplating on plastic: Characterization of the process and the deposited layer: Direct Nickel electrode plating process and properties of the electrodeposited Ni layer on plastic were characterized using Cyclic Voltametry (CV), potentiostatic (PS), Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) methods. Electrochemical investigations show that the deposition of Ni occurs at E<-0.3 V and the reduction of activation substance CoS(beta) takes place during electrode position process. The deposition rate increases with increasing cathodic potential. SEM results indicated that as cathodic potential increases, the accumulation of Ni decreases and the obtained layer has finer structure. XRD analyses show that (111) and (121) textures of the deposited layer increases with increasing cathodic potential. The increase of corrosion resistivity with increasing potential is due to both increases of Ni thickness and amount of ( 111) texture.
Effect of printing materials on fastness properties of ink-jet prints: In this study, the fastness properties of images printed on different papers with different inks are investigated in the typical weather of Vietnam. The obtained results indicate that the images on coated papers exhibit a higher light fading stability. The average time, needed for decreasing the colour density by 30% of prints on the coated papers, is approximately 2 times longer than on plain papers. The pigment-based inks also prove much excellent in colour stability in comparison to the dye-based inks. The combination of the pigment inks and the coated papers improve significantly the fastness of ink-jet prints.
Establishing mechanism of th oxidation reaction between indigocarmine and H2O2 catalyzed by Fe(II)-acrylamide complex: In our previous work the complex formation of Fe(II) with acrylamide (Acry or L) indigocarmine (Ind) and H2O2 catalyzed by the obtained complex [Fe2 L] in the system: H2O-Fe(II)-Acry-Ind-H2O2 (1) have been inverstigated. In this report, by using inhibitors such as hydroquinone (Hq), ascorbic acid (Ac) interacting specifically with OH radicals in these systems: Fe(II)-Acry-Ind-Hq(Ac)-H2O2-H2O (2) it has been proved that the catalytic reaction of ind oxidation takes place according to the radical chain mechanism. The generated OH calculated by using the method of concurrent acceptors and the Pascal programming language.
Establishment for kinetic function of percolation leaching process of non-weathred uranium ore on the column: A kinetic study of the percolation leaching process of non-weathered uranium ore contained 0.14%U on the column by acid sunfuric has been investigated. The effect of acid concentration ranging from 30-50 g/l on uranium dissolution are reported. The dissolution rate is significantly influenced by concentration of the acid solution. The experimental data for the dissolution rate of uranium have been analyzed with the shrinking core model for reaction control. The rate equation expressed in terms of fraction reacted (R) is given by 49,981.C.t = 1- (l-R)1/3 + 7,866.[1- 2R/3 - (1-R)2/3].
Establishment for model of percolation leaching process of low-grade non-weathered uranium ore: Sandstone in Nong Son basin belongs to group of low-grade uranium ore, then the method of heap leaching seems to be the most appropriate technology to treat economically such kind of ore in a large scale. A model of leaching based on the principle of "reverse capillary" using time unit of ore leaching as time of treatment. Each time of treatment is considered consiting of many cycles of rinsing acid through layers of the ore and then drain the whole solution from layers of ore and solutions in capillaries have enough time to flow upward to the surface of ore particles. A semi-empirical mathematical model is developed to describe the percolation leaching process for non-weathered uranium ore. the robust and reliable parameters needed to scale up leaching data from columns to heap are described such as: acid concentration, ore -bed height and distribution of particles size.
Examination of PANi additive effect on the electrochemical process of the hydrogenation dehydrogenation LaNi5 based electrodes: Using electrochemical empedance and sacning electronic microscopy (SEM), effects of PANi additive charfing-discharhing process of the hydrogenation/dehydrogenation electrodes prepared from LaNi5 based material have been examine. The revealed results show that PANi reduces charges transfer resistance, and especialy contributes to remaining LaNi5 based material grain preventing cracking due to the press and number of charges/discharge cycles.
Fe(II) and Fe(III) were determined simultaneously by H-point standard addition method (HPSAM) with chromogenic mixed reagents: Simultaneous determination of Fe(II) and Fe(III) in the mixed sample by H-point standard addition method (HPSAM) is described. Mixed reagents of orthophenanthroline and salicylic acid were used as a selective chromogenic system of Fe(II) and Fe(III). It was showed that with appopriate selection of wavelength pairs, both Fe(II) and Fe(III) can be detemined simultaneously with the concentration ratios of Fe(II) and Fe(III) varying from 10: 1 to 1:20 Fe(II) and Fe(III) were determined simultaneously in underground water samples in Gia Lam, Hanoi.
Improve mechanical and anticorrosion properties of nickel coating by using SiC particles in electroplating: The study on creating of Ni-SiC composite coating, the investigation of its anti-corrosion and anti-erosion behaviors have been carried out. The research of coating by SEM, EDX, metallography, hardness, abrasion, anode polarization shows that the concentration of inert particles in coating have influenced to anti-corrosion and anti-erosion characteristic of coating. Then, under optimal electroplating regime, Ni-SiC composite coatings with high anti-corrosion and anti-erosion characteristics have been created.
Inert anode material of high silic composite to protect pipeline in the underground: Although the use of impressed current system has been used for long time, the material for anode application is still a interesting question for engineers. Composite Anode Material has been investigated in the laboratory at Hanoi University of Technology and then it was manufactured and installed to protect pipeline of the Petrolimex Company. Fied investigation of the material showed that: Anode material of FeSi13T has special characters. it has been activated during 14 years, but dissolution of the anode is small in the electrolytic medium. The composite material would given a high efficiency for cathodic protection of underground structure.
Influence of synthesis conditions on structural properties of mesoporous nickel aluminate spinel: In order to prepare mesoporous nickel aluminate spinel with high surface area two factors: calcination temperature, thermal treatment were inverstigated in this study. The prepared spinels were characterized by a variety of techniques such as XRD, TPR-H2,TEM and nitrogen adsorption. The obtained results showed that, not depending on the synthesis conditions the main phase as NiAl2O4 spinel was formed over all of the samples, however, their BET surface areas were considerably effected by changing the synthesis conditions.
Method for determination of droplet distribution: Particle size distribution (PSD) is an important parameter when dealing with solid processing as well as other processes in chemical engineering. When the PSD function of a certain particle set is known, other structural parameters of a set of particle can be determined easily, especially, mean diameter dpm, porosity e, specific surface area Am, etc. These factors are very necessary to deal with processes as filtration, drying, adsorption, flotation, dissolution, crystallization, ect. By means of analysis of particles dispersed system. This is a high accurate and time-saved method.
Preparation of the alginic acid fractions enriched in polymannuronic acid and polyguluronic acid by pH-adjust method: The alginic acids with rich polymannuronic (MM) and rich polyguluronic (GG) composition have been prepared from TT-Hue brown seaweeds by pH adjust method. The alginates were hydrolyzed by hydrochloride acid under hydrothermal treatment. The alginic acid fractions enriched in polymannuronic acid and polyguluronic acid were obtained by adjusting pH from 7 to 2. The obtained alginic acids were characterized by 1H-NMR and XRD. The obtained alginic acid with controllable structure has been expected feasible applications in medicine and agriculture.
Process of determining some basic chemical components with zeolite samples out by chemical analyzing and physical chemical methods: Natural and synthetic zeolite have chemical component mainly including SiO2; Al2O3: FeO; Fe2O3; CaO; MgO; TiO2; Na2O; K2O...[2]. Zeolite is used widely in petrochemical, aquiculture and protecting environment as well as in other fields of science and technology. In the research work. we bring the process of determining some basic chemical components with zeolite samples out by chemical analyzing method and physical chemical method. which can be applied conveniently. fast with high fidelity. The Gravimetric method determine SiO2; Complex titration methods determine Al3, Ca2, Mg2 [1, 3, 4] and Fe3+ by spectrophotometer method [3, 4] to find out Al2O3, CaO, MgO, Fe2O3 component in zeolite samples.
Production of ultrafine nickel oxide powder by pulsing pyrolysis process: This paper deals with the production of nickel oxide in ultrafine powder form by pulsing pyrolysis process. Certain factors influencing to the formation of intermediate as nickel oxalate dihydrate such as crystallising temperature, pH of solution and the presence of admixtures in the system have been investigated. The results show that, by the pulsing pyrolysis process, nickel oxide is produced in ultrafine powder form.
Research and evaluation on the exposure time affecting to the quality of flexo photopolymer plates: The purpose of this study is to investigate and evaluate two factors influencing to the quality of photopolymer plates in the Flexo plate making process: the back exposure and post exposure time. The experiments were performed on MacDermid Photopolymer plate at the Banking Printing House No1.