Increase In Transformation Rate Research Articles

Effect of Microstructure on the Onset Strain and Rate per Strain of Deformation-Induced Martensite Transformation in Q&P Steel by Modeling.

The effect of microstructure on the onset strain and rate of deformation-induced martensitic transformation (DIMT) in Q&P steel is studied by a mean-field micromechanics model, in which the residual austenite (RA) and primary martensite (M) phases are treated as elastoplastic particles embedded into the ferrite (F) matrix. The results show that when the volume fraction of the RA increases with a constant fraction of the M, the onset strain of DIMT increases and transformation rate decreases, in contrast to the case of the RA fraction effect with a fixed F fraction. Increasing the volume fraction of the M postpones the DIMT, regardless of the corresponding change from the RA or F fraction, which is similar to the effect of the RA fraction with the constant M but to a higher degree. Conversely, when increasing the fraction of the matrix F, the onset strain of DIMT increases and the rate decreases, and the effect is greater when the corresponding fraction change comes from the M rather than from the RA. Moreover, when the aspect ratio of the RA increases, the onset strain of DIMT decreases with a gradual increase in transformation rate, in agreement with the experimental observation that the equiaxial austenite is more stable in Q&P steels. However, the aspect ratio effect of the M is opposite to that of the RA, indicating that the lath-shaped primary martensite could protect the austenite from DIMT.

Каталитическая трансформация диметилового эфира в углеводороды на железо модифицированном цеолите H-ZSM-5

Decrease of traditional hydrocarbon feed stock stimulates a widespread interest in the development hydrocarbons synthesis from renewable or low-value sources. The catalytic transformation of methanol into hydrocarbons, along with the Fischer–Tropsch process, can be considered as a possible way to obtain synthetic hydrocarbons. At the same time, the activity and stability of the catalysts have a decisive influence on the efficiency of the whole process. Zeolites and zeotypes of various structures traditionally used as catalysts are characterized by low rates of hydrocarbon accumulation and a short period of functioning, which requires a change in their structural characteristics or the synthesis of new systems. The aim of this work is to obtain iron-modified H-ZSM-5 type zeolites in order to increase the rate of liquid hydrocarbons accumulation and increase the lifetime of the catalyst. To achieve this goal zeolite was modified with iron, the main physicochemical characteristics of the obtained catalysts were determined and the catalytic properties were screened. Modification of zeolites by iron was carried out by the ion exchange method, as a result samples with an iron content of 0.004 wt.% to 0.240 wt.% were synthesized. In this case the decrease in the micropores surface from 280 m2/g to 190 m2/g and decrease in the number of acid sites from 1.08 mmol/g to 0.72 mmol/g was noticed. Modification of zeolite with iron of concentration up to 0.008 wt. % contributed to an increase in transformation rate of dimethyl ether from 0.04 to 0.06 kg (DME)/(kg (Cat)h) and decreace to 0.03 kg (DME)/(kg (Cat) h) during further increasing of iron content, however process selectivity to liquid hydrocarbons increase from 30% to 54%. Modification of zeolite with iron contributes to a significant change in hydrocarbon composition. With an increase in the iron concentration from 0.004 wt.% to 0.017 wt.%, the increase in the concentration of propane, butane and aliphatic hydrocarbons with the number of carbon atoms of six or more was noticed along with a decrease in the concentration of aromatic compounds.

Column transport studies of 3-nitro-1,2,4-triazol-5-one (NTO) in soils

Development of the new, insensitive, energetic compound, NTO (3-nitro-1,2,4-triazol-5-one), creates need for the data on NTO's fate and transport to predict its behavior in the environment and potential for groundwater contamination. To measure the transport of NTO in soils, we conducted miscible-displacement experiments under steady state and interrupted flow conditions using eight soils having varying physical and geochemical properties. The breakthrough curve (BTC) data were analyzed using temporal moment analysis and simulated using HYDRUS-1D to determine transport parameters and better understand the mechanisms of sorption and transformation. Parameters determined from the miscible-displacement study were compared to results obtained from batch experiments conducted for the same soils, and examined in relation to soil properties. Column NTO linear adsorption coefficients (Kd) were low and correlated well (P = 0.000049) with measurements from the batch studies. NTO transformation rate constants increased and NTO recovery decreased with increase in soil organic carbon (OC) content. Autoclaved soils had slower transformation rates and greater NTO recoveries indicating that microorganisms play a role in NTO transformation. In addition, the transformation rate increased with time in soils with higher OC. Monod-type kinetics was implemented in HYDRUS-1D to simulate the observed increase in transformation rate with time. We think this phenomenon is due to bacterial growth. Results indicate very low adsorption of NTO in a range of soils, but natural attenuation through transformation that, depending on soil OC content and hydraulic residence time, could result in complete removal of NTO.

Nanoscale Fe(0) particles for pentachlorophenol removal from aqueous solution: temperature effect and particles transformation.

Pentachlorophenol (PCP), as an important contaminant which was toxic and intractable, has received extensive attention. In this paper, the temperature effect during the transformation of PCP using nanoscale Fe(0) particles was studied, and the transformation processes of PCP and iron particles was explained. The results revealed that the removal processes of PCP followed pseudo first-order kinetics. The scale of dechlorination to the transformation of PCP increased with the increase of temperature, though the transformation rate decreased after reacting for 2 h under the experimental condition. However, the initial apparent transformation rate constants were calculated to be 0.312-0.536 h(-1) at the temperature of 20-50 degrees C, which showed an increase of transformation rate along with the increase of temperature. And the surface-area-normalized rate constants were calculated to be 9.50 x 10-3-1.63 x 10-2 L . h-1 . m-2. The experimental activation energy was calculated to be 15.0 kJ x mol(-1) from these rate constants using Arrhenius equation. A phenomenon observed at 50 degrees C indicated that more than one chlorine atom was removed from PCP and suggested β-elimination might be the major pathway for transformation. Sorption experiments showed that the sorption process on the surface of particles could be ignored in the kinetics and thermodynamics models. The changes of morphologies of nanoparticles before and after reaction indicated the transformation process of iron particles, and could be used to explain the changes of activity of nanoparticles. Magnetite (Fe3O4) and/or maghemite (Fe2O3) and lepidocrocite (γ-FeOOH) were corrosion products of iron. And along with the increase of temperature, the increased intensity of XRD peaks revealed the related a better crystallizing.

Transient down‐regulation of the RNA silencing machinery increases efficiency of Agrobacterium‐mediated transformation of Arabidopsis

Agrobacterium tumefaciens is a plant pathogen that is widely used in plant transformation. As the process of transgenesis includes the delivery of single-stranded T-DNA molecule, we hypothesized that transformation rate may negatively correlate with the efficiency of the RNA-silencing machinery. Using mutants compromised in either the transcriptional or post-transcriptional gene-silencing pathways, two inhibitors of stable transformation were revealed-AGO2 and NRPD1a. Furthermore, an immunoprecipitation experiment has shown that NRPD1, a subunit of Pol IV, directly interacts with Agrobacterium T-DNA in planta. Using the Tobacco rattle virus (TRV)--based virus-induced gene silencing (VIGS) technique, we demonstrated that the transient down-regulation of the expression of either AGO2 or NRPD1a genes in reproductive organs of Arabidopsis, leads to an increase in transformation rate. We observed a 6.0- and 3.5-fold increase in transformation rate upon transient downregulation of either AGO2 or NRPD1a genes, respectively. This is the first report demonstrating the increase in the plant transformation rate via VIGS-mediated transient down-regulation of the components of epigenetic machinery in reproductive tissue.

Particle size effects on transformation kinetics and phase stability in nanocrystalline TiO2

Other| August 01, 1997 Particle size effects on transformation kinetics and phase stability in nanocrystalline TiO2 Amy A. Gribb; Amy A. Gribb University of Wisconsin-Madison, Department of Geology and Gephysics, Madison, WI, United States Search for other works by this author on: GSW Google Scholar Jillian F. Banfield Jillian F. Banfield Search for other works by this author on: GSW Google Scholar Author and Article Information Amy A. Gribb University of Wisconsin-Madison, Department of Geology and Gephysics, Madison, WI, United States Jillian F. Banfield Publisher: Mineralogical Society of America First Online: 02 Mar 2017 Online Issn: 1945-3027 Print Issn: 0003-004X Copyright © 1997 by the Mineralogical Society of America American Mineralogist (1997) 82 (7-8): 717–728. https://doi.org/10.2138/am-1997-7-809 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Amy A. Gribb, Jillian F. Banfield; Particle size effects on transformation kinetics and phase stability in nanocrystalline TiO2. American Mineralogist 1997;; 82 (7-8): 717–728. doi: https://doi.org/10.2138/am-1997-7-809 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Kinetic studies conducted primarily between 465 and 525 °C demonstrate that the rate of the polymorphic anatase to rutile transformation increases dramatically when the reacting anatase is very finely crystalline. Coarsening of the reactant anatase and product rutile crystallites occurs simultaneously with the transformation. Kinetic behavior and quantification of transformation rate as a function of average crystallite size indicate that the increase in favorable nucleation sites is a likely cause of increase in transformation rate at small crystallite sizes. Additionally, experimental evidence supports the reversal of stabilities of anatase and rutile at small crystallite sizes. It is proposed that the reversal of stabilities is the result of rutile having a higher surface energy than the anatase phase. Data for coarsening kinetics of anatase and rutile supports the prediction that the surface energy of rutile is significantly larger than that of anatase. Thermodynamic data and theoretical estimates are used to show that a 15% greater surface energy for rutile causes the total free energy of rutile to be greater (less negative) than anatase at crystallite diameters in the few nanometer range. Given the fact that anatase and rutile structures have no polymerized octahedral fragments in common, this may be significant in determining the nature of the nucleated phase. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

DNA repair and the evolution of transformation in Bacillus subtilis. II. Role of inducible repair.

In Bacillus subtilis, DNA repair and recombination are intimately associated with competence, the physiological state in which the bacterium can bind, take up and recombine exogenous DNA. Previously, we have shown that the homologous DNA transformation rate (ratio of transformants to total cells) increases with increasing UV dosage if cells are transformed after exposure to UV radiation (UV-DNA), whereas the transformation rate decreases if cells are transformed before exposure to UV (DNA-UV). In this report, by using different DNA repair-deficient mutants, we show that the greater increase in transformation rate in UV-DNA experiments than in DNA-UV experiments does not depend upon excision repair or inducible SOS-like repair, although certain quantitative aspects of the response do depend upon these repair systems. We also show that there is no increase in the transformation rate in a UV-DNA experiment when repair and recombination proficient cells are transformed with nonhomologous plasmid DNA, although the results in a DNA-UV experiment are essentially unchanged by using plasmid DNA. We have used din operon fusions as a sensitive means of assaying for the expression of genes under the control of the SOS-like regulon in both competent and noncompetent cell subpopulations as a consequence of competence development and our subsequent experimental treatments. Results indicate that the SOS-like system is induced in both competent and noncompetent subpopulations in our treatments and so should not be a major factor in the differential response in transformation rate observed in UV-DNA and DNA-UV treatments. These results provide further support to the hypothesis that the evolutionary function of competence is to bring DNA into the cell for use as template in the repair of DNA damage.

Kinetics of the martensite transformation in athermal Fe-C-Ni-Cr alloys

An investigation was conducted to study the martensite transformation kinetics of athermal Fe-C-Ni-Cr alloys. The transformation rate was found to be dependent on alloy composition and was a function of i) the rate of change of chemical free energy with temperature, and ii) the energy expended in deforming the austenite surrounding a growing martensite embryo in order to accommodate the transformational volume and shear strains. Increasing either of the two factors leads to an increase in transformation rate. Also, it was found that the magnitude of the contribution of the deformation energy to the overall nonchemical free energy associated with the transformation depends on the alloy system and specific composition.

Effect of Carbon on Some Properties of Ti-Mo Alloys

The influence of carbon on tensile strength, tensile ductility, transformation kinetics, and grain growth characteristics of selected Ti-Mo base alloys was studied. No systematic influence of carbon in tensile strength or significant deleterious effect on tensile ductility was observed. There was a marked increase in transformation rate due to carbon. Dispersed carbides exert a marked inhibiting effect on grain boundary migration, and thus effectively prevent grain coarsening during solution treatment in the s phase field.