scholarly journals KINETICS OF SOLID-STATE MULLITE SYNTHESIS FROM ACTIVATED PRECURSORS

2018 ◽  
Vol 59 (1) ◽  
pp. 36
Author(s):  
N.F. Kosenko ◽  
N.V. Filatova ◽  
Yu.V. Pimkov
Keyword(s):  
Solid State ◽  
Active Form ◽  
Effective Rate ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
First Order ◽  
Co Precipitation ◽  
Kinetics Of ◽  
Product Accumulation ◽  
Energy Activation

The solid-state synthesis kinetics of the mullite 3Al2O3∙2SiO2 from aluminium hydroxide and metasilicic acid was studied. Hydrated oxides obtained in an active form as a result of a mechanical activation or co-precipitation (precursors) were subjected to a high-temperature treatment. The reaction rate was described by the kinetic first-order equation. Effective rate constants and energy activation were determined. The positive action of mullite seed crystals on the product accumulation was confirmed.

Fabrication and Characterization of Yttrium Lanthanum Oxide Transparent Ceramics Using Powders Prepared by Different Methods

2011 ◽  
Vol 299-300 ◽  
pp. 588-591
Author(s):  
Yun Han Li ◽  
Qiu Hong Yang ◽  
Shen Zhou Lu
Keyword(s):  
Solid State ◽  
Solid State Reaction ◽  
Lanthanum Oxide ◽  
Chemical Properties ◽  
Particle Growth ◽  
Solid State Reaction Method ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Transparent Ceramics ◽  
Composite Powders

Yttrium Lanthanum Oxide transparent ceramics were fabricated with (Y0.9La0.1)2O3 powders prepared by different methods. The growth characteristics, physical and chemical properties of the powders were investigated. The wet-chemical composite powders’ particle size was inhibited by La2O3 at high temperature treatment, therefore smaller than that of powders by solid-state reaction method. During the solid-state reaction between La2O3 and Y2O3 at temperature of 700~1100°C, La2O3 may have not effectively hindered the particle growth of Y2O3. (Y0.90La0.10)2O3 ceramic fabricated by both powders own smaller grain size and lower porosity than Y2O3 ceramics. The transmittance and sintering performance of Y2O3 ceramics were also improved after adding of La2O3. The powders prepared by both methods could be used to make high transparency ceramics.

Kinetics and mechanisms of oxidations by metal ions. Part IV. Oxidation of phenylphosphinic acid by aquavanadium(V) ions

1985 ◽  
Vol 63 (3) ◽  
pp. 663-666 ◽  
Author(s):  
Raj Narain Mehrotra
Keyword(s):  
Acidic Solution ◽  
Active Form ◽  
Equilibrium Mixture ◽  
Order Rate Constant ◽  
First Order ◽  
Inactive Form ◽  
Pseudo First Order ◽  
Independent Path ◽  
Kinetics Of ◽  
Vanadium Ion

The kinetics of the oxidation of phenylphosphinic acid by quinquevalent vanadium ion have been investigated in aqueous perchlorate media under pseudo-first order conditions (phenylphosphinic acid in excess). The reaction has a first order dependence in [V(V)] and [phenylphosphinic acid] and the observed pseudo-first order rate constant kobs is given by kobs = a + b[H+].The acid-independent path is considered to be due to the reaction between VO2+ (aq.) and C6H5P:(OH)2, the active form of phenylphosphinic acid, while the reaction between V(OH)32+ (aq.) and C6H5P(O)(OH)H, the inactive form of phenylphosphinic acid, is considered to explain the acid-dependent path. Phenylphosphinic acid in aqueous acidic solution is known to exist as an equilibrium mixture of the active and inactive forms. The composite activation and thermodynamic parameters associated with the constants a and b are reported.

Interfacial transfer kinetics of NO2 into pulmonary epithelial lining fluid

1991 ◽  
Vol 71 (4) ◽  
pp. 1502-1510 ◽  
Author(s):  
E. M. Postlethwait ◽  
S. D. Langford ◽  
A. Bidani
Keyword(s):  
Effective Rate ◽  
Dependent Manner ◽  
Epithelial Lining ◽  
Interfacial Resistance ◽  
Epithelial Lining Fluid ◽  
First Order ◽  
Interfacial Mass Transfer ◽  
Biological Substrates ◽  
Phenomenological Coefficients ◽  
Kinetics Of

Previous studies, both in intact lungs and epithelial lining fluid (ELF) (J. Appl. Physiol. 68: 594–603, 1990 and J. Appl: Physiol. 69: 523–531, 1990), have suggested that the steady-state absorption of inhaled NO2 is mediated by chemical reaction(s) between NO2 and ELF solute reactants. To characterize the kinetics of NO2 absorption into aqueous biological substrates across a gas-liquid interface, we utilized a closed system of known geometry and initial gas phase [NO2] [([NO2]g)0] to expose ELF (as bronchoalveolar lavage; BAL) and a biochemical model system (glutathione, GSH). Assessments of NO2 reactive uptake, into both GSH and ELF, indicated first-order NO2 kinetics [([NO2]g)0 less than or equal to 10.5 ppm] with effective rate constants of (kNO2)GSH = 4.8 and (kNO2)BAL = 2.9 ml.min-1.cm-2 (stirred). Above 10.5 ppm (1 mM GSH), zero-order kinetics were observed. Both (kNO2)GSH and (kNO2)BAL showed aqueous reactant dependence. The reaction order with respect to GSH and BAL was 0.47 and 0.64, respectively. We found no effect of interfacial surface area or bulk phase volume on kNO2. In unstirred systems, significant interfacial resistance was observed and was related to reactant concentration. These results indicate that NO2 reactive uptake follows first-order kinetics with respect to NO2 ([NO2]g less than or equal to 10.5 ppm) and displays aqueous substrate dependence. Furthermore the site of reactive absorption appears to be limited to near the aqueous surface interface. Unstirred conditions confine interfacial mass transfer kinetics in a dose-dependent manner. These phenomenological coefficients may provide the basis for direct extrapolation to environmentally relevant exposure concentrations.

Ring-Opening Polymerization of ε-Caprolactone Using Novel Tin(II) Alkoxide Initiators

2008 ◽  
Vol 55-57 ◽  
pp. 757-760 ◽  
Author(s):  
A. Kleawkla ◽  
Robert Molloy ◽  
W. Naksata ◽  
Winita Punyodom
Keyword(s):  
Solid State ◽  
Rate Constants ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Zero Order ◽  
Molecular Aggregation ◽  
First Order ◽  
First Order Kinetics ◽  
Zero Order Kinetics ◽  
Kinetics Of

Two novel tin(II) alkoxides, namely: tin(II) hexoxide, Sn(OC6H13)2, and tin(II) octoxide, Sn(OC8H17)2, have been synthesized for use as coordination-insertion initiators in the bulk ring-opening polymerization of ε-caprolactone. The kinetics of the polymerization reactions were studied at 140 °C by dilatometry. It was found that both alkoxides were slow to dissolve in the ε-caprolactone monomer due to their molecular aggregation in the solid state. As a result, the slow solubilization of the initiators gave rise to deviations from the expected first-order kinetics. Instead, the kinetic results adhered more closely to zero-order kinetics with apparent zero-order rate constants k0 of 6.58 x 10-2 and 4.63 x 10-2 mol l-1 min-1 for the hexoxide and octoxide respectively

scholarly journals Ultra High Temperature Treatment, but Not Pasteurization, Affects the Postprandial Kinetics of Milk Proteins in Humans

2008 ◽  
Vol 138 (12) ◽  
pp. 2342-2347 ◽  
Author(s):  
Magali Lacroix ◽  
Cyriaque Bon ◽  
Cécile Bos ◽  
Joëlle Léonil ◽  
Robert Benamouzig ◽  
...  
Keyword(s):  
High Temperature ◽  
Milk Proteins ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Kinetics Of ◽  
Ultra High Temperature

scholarly journals KINETICS OF STRUCTURAL TRANSFORMATIONS AT PORES FORMATION DURING HIGH-TEMPERATURE TREATMENT OF FOAM GLASS

2018 ◽  
Vol 14 (2) ◽  
pp. 158-168 ◽  
Author(s):  
Sergey V. Fedosov ◽  
Maksim O. Bakanov ◽  
Sergey N. Nikishov
Keyword(s):  
Foam Glass ◽  
Outer Boundary ◽  
Glass Structure ◽  
Three Dimensional ◽  
Spherical Shape ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Glass Charge ◽  
Growth Center ◽  
Kinetics Of

The work shows the key points used in the simulation of pores formation and growth in the foam glass structure. Pore is represented as a separate radius growth center with the outer boundary of a spherical shape and with a specified value of the initial radius surrounded by a finite volume of molten glass that is a part of foam glass charge stock. Solution of three-dimensional problem is reduced to one-dimensional setting in spherical coordinates. The presented model takes into consideration kinetics of pores radius growth, taking into account the influence of glass viscosity and surface tension, as well as the effect of moving (stretching) glass cladding when pores radius increases.

Characterization of Zr-doped TiO2 prepared by homogenous co-precipitation without high-temperature treatment

2007 ◽  
Vol 42 (22) ◽  
pp. 9421-9428 ◽  
Author(s):  
Jozef Lukáč ◽  
Mariana Klementová ◽  
Petr Bezdička ◽  
Snejana Bakardjieva ◽  
Jan Šubrt ◽  
...  
Keyword(s):  
High Temperature ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Doped Tio2 ◽  
Co Precipitation

Synthesis, Characterization and Photocatalytic Activities of Bismuth Vanadate by Facile Co-Precipitation Method

2010 ◽  
Vol 148-149 ◽  
pp. 1469-1472
Author(s):  
Chao Jun Liu ◽  
Yue Hua Xu
Keyword(s):  
Diffuse Reflectance Spectroscopy ◽  
Average Crystallite Size ◽  
Temperature Treatment ◽  
Precipitation Method ◽  
High Temperature Treatment ◽  
Synthesis Conditions ◽  
High Efficient ◽  
Photocatalytic Activities ◽  
Co Precipitation ◽  
Monoclinic Bivo4

Monoclinic BiVO4 photocatalysts were synthesized via facile and straightforward co-precipitation method at room temperature without high temperature treatment and characterized with X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), flourier transfer infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), and transmission electron microscopy (TEM). The results indicate that through proper selection of synthesis conditions, it is possible to obtain high efficient BiVO4 nanoparticles. The as-prepared monoclinic BiVO4 photocatalysts have an average crystallite size of about 20 nm with the particle size of about 20 to 50 nm. Their photocatalytic activities were evaluated by decolorization of rhodamine B in aqueous solution under visible light irradiation, and the relationship between the photocatalytic activity of BiVO4 and their physicochemical properties were investigated.

scholarly journals The influence of conformational defects on the development of structural phase transition in tetracosane C24H50

2021 ◽  
Vol 2103 (1) ◽  
pp. 012091
Author(s):  
S A Gureva ◽  
V A Marikhin ◽  
L P Myasnikova ◽  
B Z Volchek ◽  
D A Medvedeva
Keyword(s):  
Phase Transition ◽  
Solid State ◽  
Ftir Spectroscopy ◽  
Melting Temperature ◽  
Structural Phase Transition ◽  
Structural Transition ◽  
Structural Phase ◽  
First Order ◽  
Solid Phases ◽  
Kinetics Of

Abstract The kinetics of the first-order solid-state structural transition in monodisperse n-alkanes samples of even tetracosane C24H50 was studied by FTIR spectroscopy. The existence of many irregular conformers in solid phases of tetracosane, the concentration of which reaches a maximum when approaching the melting temperature, has been demonstrated. The existence of these defective molecules promotes transitions between different rotator phases in the solid state.

scholarly journals Kinetika Perubahan Sifat Fisik dan Kadar Tanin Biji Sorgum (Sorghum Bicolor L.) Selama Perendaman

2019 ◽  
Vol 39 (3) ◽  
pp. 222
Author(s):  
Asropi Asropi ◽  
Nursigit Bintoro ◽  
Joko Nugroho Wahyu Karyadi ◽  
Sri Rahayoe ◽  
Arifin Dwi Saputro
Keyword(s):  
Temperature Treatment ◽  
Distilled Water ◽  
Tannin Content ◽  
Change Rate ◽  
Constant Rate ◽  
Higher Temperature ◽  
Kinetics Of Reaction ◽  
Increasing Temperature ◽  
Kinetics Of ◽  
Energy Activation

Some studies have been done to examine that the soaking process of sorghum seeds decrease the tannin level, but have not yet examined the kinetics of reaction changes during soaking. The aim of this experiment was to study the kinetics of changes on physical characteristics and tannin level of sorghum seeds during soaking. This experiment used milled and not milled red sorghum seeds which were soaked for 24 hours in distilled and alkaline solution at 30, 45, and 60 ºC. Observed parameters included water content, tannin content, and hardness, which were analyzed using statistical data and the kinetics of parameter change rate. Temperature treatment had a significant effect on the changes in all parameters of sorghum seeds during soaking. The increase in temperature accelerated the diffusion coefficient (Deff) in a range between 6.6345x10-12 m2/second to 13.5519x10-12 m2/second and energy activation of 8.054 kJ/mol; 3.274 kJ/mol; 3.183 kJ/mol; and 7.29 kJ/mol on the distilled water soaking treatment of not milled sorghum seeds, alkaline soaking treatment of not milled seeds, the distilled water soaking treatment of milled sorghum seeds, and alkaline soaking treatment of milled seeds.  The highest decrease in tannin content was 77.9%, that was obtained in the treatment of alkaline soaking treatment of milled seeds at 60 ºC. The highest increase in volume occurred in the treatment of alkaline soaking treatment of milled seeds (76.0%).  The value of the constant rate tended to increase with the increasing temperature of the soaking process. This means that the changes in the parameter were faster at a higher temperature, so the energy activation used is lower.

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