scholarly journals Effects of Li2O on Structure and Viscosity of CaO-Al2O3-Based Mold Fluxes

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Lifeng Chen ◽  
Kun Liu ◽  
Peng Han ◽  
Bin Yang ◽  
Lianghua Feng
Keyword(s):  
Molecular Dynamics ◽  
Mold Flux ◽  
Molten Slag ◽  
Complex Structure ◽  
Degree Of Polymerization ◽  
Dynamics Simulation ◽  
Systematic Analysis ◽  
Structure Characteristics ◽  
Mold Fluxes ◽  
Stable Structures

Since CaO-Al2O3-based mold fluxes are one of the most important mold flux systems in metallurgic processes, it is important to explore their structure characteristics and viscosity. Molecular dynamics simulation is performed to study the effect of w(CaO)/w(Al2O3) ratio on both the structural and viscosity properties of CaO-Al2O3-based mold fluxes. A systematic analysis of the structure and thermodynamics on CaO-Al2O3-based mold fluxes is carried out, and it is well known that the viscosity of mold fluxes is related to the structure. The results show that the formation of stable structures of Si-O in the mold fluxes was beneficial to reduce the probability of structural interconnection, degree of polymerization, and viscosity of the molten slag. In the cationic structure, the contents of Ca-O-Al and Ca-O-Si are more stable, the interconnection of the Ca-O-Al and Ca-O-Si network weakens, and the viscosity decreases. The tetrahedra [AlO4] and [SiO4] have similar structures, but they exhibit different thermodynamic and physical properties. Viscosity test shows that CaO/Al2O3 = 0.88–2 continuously increased, when the cosolvent content Li2O = 1%–4%, CaO-Al2O3-based mold flux viscosity decreased, the degree of network structure polymerization decreased, and the complex structure depolymerized. Increasing the water content in the cosolvent is beneficial to reduce the viscosity of the crystallizer.

scholarly journals Role of B2O3 on structure and shear-thinning property in CaO–SiO2–Na2O-based mold fluxes

2019 ◽  
Vol 38 (2019) ◽  
pp. 750-759
Author(s):  
Li-Guang Zhu ◽  
Zhi-Peng Yuan ◽  
Ying Xu ◽  
Kai-Xuan Zhang ◽  
Yi-Hua Han
Keyword(s):  
Continuous Casting ◽  
Newtonian Fluid ◽  
High Speed ◽  
Structural Changes ◽  
Mold Flux ◽  
Shear Thinning ◽  
Degree Of Polymerization ◽  
Dynamics Simulation ◽  
Shear Rates ◽  
Mold Fluxes

AbstractMost traditional mold fluxes are Newtonian fluids, and their constant viscosity has certain limitations in continuous casting. A new non-Newtonian fluid mold flux with shear-thinning behavior, i.e., a mold flux with a relatively high viscosity at lower shear rates and a relatively low viscosity at higher shear rates, is required to satisfy the mold-flux performance requirements for high-speed continuous casting. The addition of a certain amount of B2O3 to a CaO–SiO2–Na2O-based mold flux can result in a shear-thinning property. To obtain an improved understanding of the mechanism of this characteristic, a molecular-dynamics simulation method was used to study the microstructural changes of the mold flux. Structural changes of mold-flux samples were analyzed and verified by Raman spectroscopy. The results of the two methods were almost the same, both resulted from the addition of B2O3 and changed the microstructure and degree of polymerization of the mold flux, which resulted in the shear-thinning property of the mold flux. This non-Newtonian fluid mold flux was used in square-billet casting tests, and the quality of the slab was improved effectively.

Study on Structure Characteristics of B2O3 and TiO2-bearing F-Free Mold Flux by Raman Spectroscopy

2013 ◽  
Vol 32 (3) ◽  
pp. 265-273 ◽  
Author(s):  
Zhen Wang ◽  
Qifeng Shu ◽  
Kuochih Chou
Keyword(s):  
Raman Spectroscopy ◽  
Mold Flux ◽  
Complex Structure ◽  
Slag System ◽  
Degree Of Polymerization ◽  
Structural Group ◽  
Destructive Effect ◽  
Structure Characteristics ◽  
Structure Unit ◽  
Sheet Structure

AbstractStructure characteristics of fluoride-Free mold flux containing simultaneously B2O3 and TiO2 have been investigated by Raman spectroscopy in this work. Raman spectra for glass samples with different basicities, different contents of TiO2 and B2O3 were recorded during the experiments. According to the experiments results, increase of TiO2 content leads to the appearance of [TiO4] and [TiO6] structure groups, and [TiO4] becomes the main structure unit in the system. TiO2 produces a certain destructive effect on Si-O-Si network structure as well as large borate group and conducive to the formation of some other complex structure groups, such as (Si,Ti) coupling in sheet unit. It can be concluded that, with the increase of B2O3, the ratio of mixing of the Q0 structure unit and [TiO4] structural group decrease and the ratio of sheet structure unit increase, and there forms large borate group. Existence of B2O3 increases polymerization degree of the slag system. In addition, increasing basicity causes to the decrease of Q2 and sheet structure unit and increase of mixing of the Q0 structure unit and [TiO4] structural group, and weakening the large borate group. It could be concluded that the increase of basicity reduces the degree of polymerization of the system.

Investigation the influences of B2O3and R2O on the structure and crystallization behaviors of CaO–Al2O3based F-free mold flux

2018 ◽  
Vol 115 (3) ◽  
pp. 304 ◽  
Author(s):  
Jiangling Li ◽  
Bowen Kong ◽  
Xiangyu Gao ◽  
Qingcai Liu ◽  
Qifeng Shu ◽  
...  
Keyword(s):  
Liquidus Temperature ◽  
Mold Flux ◽  
Crystallization Process ◽  
Degree Of Polymerization ◽  
Scanning Calorimetry ◽  
Structural Investigations ◽  
Crystallization Ability ◽  
Mold Fluxes ◽  
New Type ◽  
Positive Effect

The influences of B2O3and R2O on the structure and crystallization of CaO–Al2O3based F-free mold flux were investigated by Raman Spectroscopy and Differential Scanning Calorimetry Technique, respectively, for developing a new type of F-free mold flux. The results of structural investigations showed that B3+is mainly in the form of [BO3]. And [BO3] appears to form BIII–O–Al linkage which will produce a positive effect on forming [AlO4] network. The number of bridging oxygen and the degree of polymerization of [AlO4] network structure for CaO–Al2O3system were also increased with the increasing of B2O3. On the contrary, with the addition of R2O into CaO–Al2O3–B2O3system, the number of bridging oxygen and the degree of polymerization of [AlO4] network were decreased. DSC results showed that the crystallization process became more sluggish with the increase of B2O3, which indicated that the crystallization ability was weakened. While the quenched mold fluxes crystallized more rapidly when introducing R2O. In other word, the crystallization rates of CaO–Al2O3based slags were accelerated by the introduction of R2O. The liquidus temperature and crystallization temperature were decreased with the increasing amount of B2O3or by addition of R2O into CaO–Al2O3system. Only one kind of crystal was precipitated in 8% B2O3and %R2O-containing samples, which was CaAl2O4identified by SEM-EDS. When the content of B2O3increased from 8% to 16%, Ca3B2O6is clearly observed, demonstrating that the crystallization ability of Ca3B2O6is enhanced by the increasing concentration of B2O3in mold flux. The Ca/Al ratio of the generated calcium aluminate has been altered from 1:2 to 1:4 with the increasing of B2O3. The size of CaAl2O4crystal is gradually increased with the addition of R2O. The crystallization ability of CaAl2O4is promoted by R2O.

scholarly journals Molecular Dynamics Simulation reveals the mechanism by which the Influenza Cap-dependent Endonuclease acquires resistance against Baloxavir marboxil

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Ryunosuke Yoshino ◽  
Nobuaki Yasuo ◽  
Masakazu Sekijima
Keyword(s):  
Molecular Dynamics ◽  
Aromatic Ring ◽  
Influenza A ◽  
Md Simulation ◽  
Binding Free Energy ◽  
Complex Structure ◽  
Antiviral Drug ◽  
Rna Replication ◽  
Dynamics Simulation ◽  
Dependent Endonuclease

AbstractBaloxavir marboxil (BXM), an antiviral drug for influenza virus, inhibits RNA replication by binding to RNA replication cap-dependent endonuclease (CEN) of influenza A and B viruses. Although this drug was only approved by the FDA in October 2018, drug resistant viruses have already been detected from clinical trials owing to an I38 mutation of CEN. To investigate the reduction of drug sensitivity by the I38 mutant variants, we performed a molecular dynamics (MD) simulation on the CEN-BXM complex structure to analyze variations in the mode of interaction. Our simulation results suggest that the side chain methyl group of I38 in CEN engages in a CH-pi interaction with the aromatic ring of BXM. This interaction is abolished in various I38 mutant variants. Moreover, MD simulation on various mutation models and binding free energy prediction by MM/GBSA method suggest that the I38 mutation precludes any interaction with the aromatic ring of BXA and thereby reduces BXA sensitivity.

scholarly journals Calculation and Analysis of the Structure and Viscosity of B2O3-Regulated CaO-Al2O3-Based Mold Fluxes

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Lifeng Chen ◽  
Kun Liu ◽  
Peng Han ◽  
Bin Yang ◽  
Lianghua Feng
Keyword(s):  
Molten Slag ◽  
Chemical Properties ◽  
Casting Process ◽  
Degree Of Polymerization ◽  
Particle Migration ◽  
Mold Slag ◽  
Migration Resistance ◽  
O2 Concentration ◽  
Mold Fluxes ◽  
Physical And Chemical

The high content of aluminum in the steel reacts with the CaO-Si2O-based mold fluxes, resulting in deterioration of the mold slag physical and chemical properties, which cannot be applied to the continuous casting molten slag casting process of high-Mn high-Al steel Herein, the thermodynamic and structural properties of low-reactivity CaO-Al2O3-based mold fluxes were investigated. The thermodynamic properties were studied based on the first principles of quantum mechanics. The results show that the formation of stable structures of B-O and O-B-O in the mold fluxes was beneficial to reduce the probability of structural interconnection, degree of polymerization, and viscosity of the molten slag. The increase in the ratio of CaO/Al2O3 = 0.88–2 led to an increase in the O2− concentration. O2− entered the [AlO4] structure to form a stable structure of [AlO6] and [AlO5], wherein [AlO6] was more stable than [AlO5], reducing the degree of polymerization of the network structure. When cosolvent content B2O3 = 2%–10%, a simple layered structure of [BO3] was formed, and the particle migration resistance, break temperature, and viscous activation energy of the mold fluxes were reduced, while the corrected optical basicity of mold fluxes was gradually increased.

Molecular Dynamics Simulation of the Rapid Solidification of Liquid Zinc

2011 ◽  
Vol 383-390 ◽  
pp. 7385-7389 ◽  
Author(s):  
Rui Na Ma ◽  
Hong Chen Qiu ◽  
Jian Jun Wu
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Cooling Rate ◽  
Rapid Solidification ◽  
Energy Analysis ◽  
Complex Structure ◽  
Solidification Process ◽  
Amorphous Structure ◽  
Dynamics Simulation ◽  
Simulation Based

Molecular dynamics simulation based on the Morse potential is carried out to investigate the rapid solidification of Zn. Radial distribution function, the energy analysis, Voronoi polyhedral structure analysis are used to analyze the microstructure evolution of solidification process. The results showed that amorphous structure formed when the cooling rate exceeded 2.5×1012K/s; crystal formed when the cooling rate less than 7.0×1011K/s; complex structure formed when the cooling rate was between7.0×1011K/s and 2.5×1012K/s.

scholarly journals A Study of the Adsorption and Diffusion Behavior of a Single Polydimethylsiloxane Chain on a Silicon Surface by Molecular Dynamics Simulation

2011 ◽  
Vol 391-392 ◽  
pp. 998-1002
Author(s):  
Jian Quan Li ◽  
Dan Mu
Keyword(s):  
Molecular Dynamics ◽  
Adsorption Energy ◽  
Dynamic Properties ◽  
Relative Dielectric Constant ◽  
Degree Of Polymerization ◽  
Dynamics Simulation ◽  
Dynamics Simulations ◽  
Chain Lengths ◽  
The Relationship ◽  
And Diffusion

The adsorption and diffusion of polydimethylsiloxane (PDMS) with different chain lengths on a silicon (111) surface were studied by molecular dynamics simulations. The relative dielectric constant was selected to be 1 to mimic a vacuum. The chains were all present as two dimensional (2D) adsorption conformation on the surface but different conformations and dynamic properties were found in the two absolutely different environments. The relationship between the adsorption energy of the different chain lengths and the degree of polymerization follows a linear function and the average adsorption energy per segment is -0.42 kcal/mol. In addition, the diffusion coefficient (D) of these chains scales with the degree of polymerization (N) as N-3/2.

ADSORPTION AND DIFFUSION PROCESSES OF POLYETHYLENE ON SILICON (111) SURFACE STUDIED BY MOLECULAR DYNAMICS SIMULATION

2011 ◽  
Vol 10 (04) ◽  
pp. 411-421 ◽  
Author(s):  
DAN MU ◽  
YI-HAN ZHOU
Keyword(s):  
Molecular Dynamics ◽  
Adsorption Energy ◽  
Diffusion Processes ◽  
Dynamic Properties ◽  
Relative Dielectric Constant ◽  
Hydrophobic Surface ◽  
Degree Of Polymerization ◽  
Dynamics Simulation ◽  
Chain Lengths ◽  
And Diffusion

The adsorption of polyethylene with different chain lengths on a silicon (111) surface is studied via molecular dynamics simulations. The relative dielectric constant is selected to be 1 and 78.0 to mimic in vacuum and in solution environment, respectively. Different configurations and dynamic properties are found in the two absolutely different environments, showing that the solvent condition plays an obvious role in the process of chain adsorption and diffusion on the hydrophobic surface. The chain all present as two-dimensional (2D) adsorption configuration on the surface. The adsorption energy of different chain lengths follows a linear function, and the average adsorption energy per segment is -1.58 kcal/mol. In addition, the diffusion coefficient (D) of such chains scales with the degree of polymerization (N) as N-3/2.

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