scholarly journals Pressure Field Assisted Polycondensation Nonaqueous Precipitation Synthesis of Mullite Whiskers and Their Application as Epoxy Resin Reinforcement

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2007 ◽  
Author(s):  
Guo Feng ◽  
Feng Jiang ◽  
Zi Hu ◽  
Weihui Jiang ◽  
Jianmin Liu ◽  
...  
Keyword(s):  
Epoxy Resin ◽  
Pressure Field ◽  
Precipitation Method ◽  
High Yield ◽  
Heating Process ◽  
Aluminum Fluoride ◽  
Different Temperatures ◽  
Mullite Whiskers ◽  
Vs Mechanism ◽  
Theoretical Amount

Mullite whiskers were novelty prepared via pressure field assisted polycondensation nonaqueous precipitation method. The precipitate phase transition in heating process, phase compositions and microstructure of samples calcined at different temperatures, effect of pressure field on precursors polycondensation and AlF3 amount on sample morphology, the structure and the growth mechanism of whiskers were investigated. The results indicate that pressure field caused by kettle treatment promotes the polycondensation reaction between AlF3 and tetraethyl orthosilicate (TEOS), the excess aluminum fluoride coordinates with the precipitate skeleton of the =Al–O–Si≡, which brings about the low mullitization temperature (900 °C). The sample prepared with the optimal amount of aluminum fluoride (1.3 of the theoretical amount) calcined at 1100 °C presents high yield and aspect ratio (>15, 100 nm in diameter) of mullite whiskers. Growth of whiskers prepared via pressure field assisted polycondensation nonaqueous precipitation method is attributed to a vapor-solid (VS) mechanism with the inducement of screw. These mullite whiskers with the structure of multi-needle whiskers connected in the same center can be distributed evenly in epoxy resin, which greatly improves the mechanical properties of epoxy resin.

scholarly journals Surface Modification of Fly Ash for Active Catalysis

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Deepti Jain ◽  
Renu Hada ◽  
Ashu Rani
Keyword(s):  
Fly Ash ◽  
Heterogeneous Catalysts ◽  
Chemical Activation ◽  
Alumina Content ◽  
Precipitation Method ◽  
Solid Base ◽  
Thermally Activated ◽  
Flame Atomic Absorption ◽  
Flame Atomic Absorption Spectrophotometer ◽  
Different Temperatures

Fly ash based effective solid base catalyst (KF/Al2O3/fly ash473, KF/Al2O3/fly ash673, and KF/Al2O3/fly ash873) was synthesized by loading KF over chemically and thermally activated fly ash. The chemical activation was done by treating fly ash with aluminum nitrate via precipitation method followed by thermal activation at 650°C to increase the alumina content in fly ash. The increased alumina content was confirmed by SEM-EDX analysis. The alumina enriched fly ash was then loaded with KF (10 wt%) and calcined at three different temperatures 473 K, 673 K and 873 K. The amount of loaded KF was monitored by XRD, FTIR spectroscopy, SEM-EDX, TEM and Flame Atomic Absorption Spectrophotometer. The catalytic activities of the catalysts were tested in the Claisen-Schmidt condensation of benzaldehyde and 4-methoxybenzaldehyde with 2′-hydroxyacetophenone to produce 2′-hydroxychalcone and 4-methoxy-2′-hydroxychalcone respectively. Higher conversion (83%) of benzaldehyde and (89%) of 4-methoxybenzaldehyde reveals that among these heterogeneous catalysts KF/Al2O3/fly ash673 is very active.

Synthesis and Characterization of Different γ-Al2O3 Nanocatalysts for Methanol Dehydration to Dimethyl Ether

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Seyyed Ya'ghoob Hosseini ◽  
Mohammad Reza Khosravi Nikou
Keyword(s):  
Dimethyl Ether ◽  
Solid Acid Catalyst ◽  
Fixed Bed ◽  
Operating Parameter ◽  
Textural Properties ◽  
Ammonia Solution ◽  
Precipitation Method ◽  
High Yield ◽  
Methanol Dehydration ◽  
Adsorption Desorption

Abstract A simple co-precipitation method was utilized to synthesize γ-Al2O3 catalysts using aluminum nitrate nonahydrate as the source of aluminum cations for methanol dehydration to dimethyl ether (DME). Different precipitating agents comprising ammonium carbonate, ammonium bicarbonate and ammonia solutions were used for preparation of the samples. The catalysts were characterized by XRD, FTIR, SEM, NH3-TPD and N2 adsorption-desorption techniques. The sample prepared by ammonia solution had the highest acidity among the synthesized catalysts. Also, N2 adsorption-desorption results showed suitable textural properties for all of the synthesized samples. Vapor phase dehydration of methanol to DME was performed in the fixed bed micro reactor over the synthesized catalysts and commercial one for comparison purposes. The effects of different characteristics of catalysts such as surface area, acidity, sintering factor and temperature as an operating parameter on performance of catalysts were investigated. The catalyst prepared by ammonia solution showed best catalytic activity due to the suitable textural properties and high amount of acidic sites. Also, the results showed that only high acid strength can’t result high yield of DME for a solid acid catalyst.

scholarly journals A Novel Inulin-Mediated Ethanol Precipitation Method for Separating Endo-Inulinase From Inulinases for Inulooligosaccharides Production From Inulin

2021 ◽  
Vol 9 ◽  
Author(s):  
Xin Li ◽  
Qiannan Zhang ◽  
Wei Wang ◽  
Shang-Tian Yang
Keyword(s):  
Enzymatic Hydrolysis ◽  
Aspergillus Niger ◽  
Functional Food ◽  
Degree Of Polymerization ◽  
Precipitation Method ◽  
High Yield ◽  
Process Conditions ◽  
Food Ingredients ◽  
Ethanol Precipitation ◽  
Novel Method

Inulin is a kind of polysaccharide that can be obtained various biomass. Inulooligosaccharides (IOS), a kind of oligosaccharides that can be obtained from inulin by enzymatic hydrolysis using inulinases, have been regarded as the functional food ingredients. Commercially available inulinases produced by natural Aspergillus niger contained both endo- and exo-inulinase activities. For IOS production from inulin, it is desirable to use only endo-inulinase as exo-inulinase would produce mainly the monosacchairde fructose from inulin. In the present study, a simple inulin-mediated ethanol precipitation method was developed to separate endo- and exo-inulinases present in natural inulinases. IOS production from inulin using the enriched endo-inulinase was then optimized in process conditions including pH and temperature, achieving a high yield of ∼94%. The resultant IOS products had a degree of polymerization ranging from 2 to 7. The study demonstrated a novel method for obtaining partially purified or enriched endo-inulinase for IOS production from inulin in an efficient process.

Transient Thermal Analysis of an Anisotropic Conductive Film Package Assembly Process

2000 ◽  
Author(s):  
Victor Adrian Chiriac ◽  
Tien-Yu Tom Lee
Keyword(s):  
Temperature Drop ◽  
Thermal Response ◽  
Heating Process ◽  
Assembly Process ◽  
Anisotropic Conductive Film ◽  
Conductive Film ◽  
Different Temperatures ◽  
Computational Fluid Dynamics Cfd ◽  
Nozzle Head ◽  
Transient Thermal

Abstract Transient thermal simulation was performed to analyze thermal response of the assembly process for a package using Anisotropic Conductive Film (ACF). Two assembly processes were modeled: a simplified process where the package was fixed at two different temperatures during assembly, and a detailed process where the package experienced a ramping heating process, followed by a constant temperature curing process. A 3D conjugate Computational Fluid Dynamics (CFD) study was first conducted, followed by a 3D conduction-only analysis due to the minimal effect of convection and radiation. Results from the detailed process modeling indicated that during the initial ramping, within 0.02 second, the die and nozzle head experienced a small temperature drop due to the cooling effect of the ACF material and substrate. The ACF material also displayed a steep increase in temperature after contacting the die, followed by a short decay, then ramped up again. At the end of the 10-second ramping process, the ACF reached a temperature of almost 203°C, while the die was at 206°C. During the 5 seconds of curing, all parts reached steady state in less than 2 seconds.

scholarly journals Characterisation of Ex Vivo Liver Thermal Properties for Electromagnetic-Based Hyperthermic Therapies

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 3004 ◽  
Author(s):  
Nuno P. Silva ◽  
Anna Bottiglieri ◽  
Raquel C. Conceição ◽  
Martin O’Halloran ◽  
Laura Farina
Keyword(s):  
Thermal Properties ◽  
Ex Vivo ◽  
Tissue Perfusion ◽  
Heating Process ◽  
Volumetric Heat Capacity ◽  
Accurate Knowledge ◽  
Different Temperatures ◽  
Treatment Plans ◽  
Specific Tissue ◽  
Tissue Target

Electromagnetic-based hyperthermic therapies induce a controlled increase of temperature in a specific tissue target in order to increase the tissue perfusion or metabolism, or even to induce cell necrosis. These therapies require accurate knowledge of dielectric and thermal properties to optimise treatment plans. While dielectric properties have been well investigated, only a few studies have been conducted with the aim of understanding the changes of thermal properties as a function of temperature; i.e., thermal conductivity, volumetric heat capacity and thermal diffusivity. In this study, we experimentally investigate the thermal properties of ex vivo ovine liver in the hyperthermic temperature range, from 25 °C to 97 °C. A significant increase in thermal properties is observed only above 90 °C. An analytical model is developed to model the thermal properties as a function of temperature. Thermal properties are also investigated during the natural cooling of the heated tissue. A reversible phenomenon of the thermal properties is observed; during the cooling, thermal properties followed the same behaviour observed in the heating process. Additionally, tissue density and water content are evaluated at different temperatures. Density does not change with temperature; mass and volume losses change proportionally due to water vaporisation. A 30% water loss was observed above 90 °C.

scholarly journals Effect of Annealing on the ZnS Nanocrystals Prepared by Chemical Precipitation Method

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Nadana Shanmugam ◽  
Shanmugam Cholan ◽  
Natesan Kannadasan ◽  
Kannadasan Sathishkumar ◽  
G. Viruthagiri
Keyword(s):  
Chemical Precipitation ◽  
Chemical Precipitation Method ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Visible Absorption ◽  
Atomic Force ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Uv Visible ◽  
Dta Curves

Nanocrystals of ZnS have been synthesized through simple chemical precipitation method using thiourea as sulphur source. The synthesized products were annealed at different temperatures in the range of 200–800∘C. The as-synthesized and annealed samples were characterized by X-ray diffraction (XRD), UV-Visible absorption (UV-Vis), and room temperature photoluminescence (PL) measurements. The morphological features of ZnS annealed at 200 and 500∘C were studied by atomic force microscope (AFM) and transmission electron microscope (TEM) techniques. The phase transformation of ZnS and formation of ZnO were confirmed by thermogravimetric (TG) and differential thermal analysis (DTA) curves.

High Temperature Properties of CoFe/CoNi and Fe/CoNi Biphase Microwires

2015 ◽  
Vol 233-234 ◽  
pp. 265-268 ◽  
Author(s):  
Irene Iglesias ◽  
Rhimou El Kammouni ◽  
Kseniay Chichay ◽  
Manuel Vazquez ◽  
Valeria Rodionova
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Single Phase ◽  
Amorphous Structure ◽  
Magnetic Behaviour ◽  
Heating Process ◽  
Saturation Magnetostriction ◽  
Magnetostriction Constant ◽  
Different Temperatures ◽  
Drawing Technique

The objective of this work has been to analyze the high-temperature behavior of magnetically single-and biphase microwires because of its interest from fundamental and applications viewpoints. Two alloy compositions with amorphous structure covered by glass have been prepared as magnetically single phase microwires by quenching & drawing technique: CoFe-based with near zero saturation magnetostriction constant and Fe-based with positive saturation magnetostriction constant. The same wires were used as the core for magnetically biphase microwires. Second CoNi phase was deposited by electroplating. Magnitudes as saturation magnetization and hysteresis parameters are determined in the temperature range from room temperature up to 1200 K. We proceed to a comparative analysis of their magnetic behaviour at different temperatures as well as after cooling down to room temperature. Information on the Curie temperature of different phases and on the influence of heating process on the magnetic properties is thus derived.

scholarly journals Fluorescence investigation of epoxy resin LG 285 and mathematical description of the curing process

2019 ◽  
Vol 292 ◽  
pp. 01025
Author(s):  
Michaela Mikuličová ◽  
Vladimír Vašek ◽  
Vojtěch Křesálek
Keyword(s):  
Steady State ◽  
Fluorescence Spectroscopy ◽  
Epoxy Resin ◽  
Mathematical Description ◽  
Curing Process ◽  
Steady State Fluorescence ◽  
Two Component ◽  
Different Temperatures ◽  
Increasing Temperature ◽  
Steady State Fluorescence Spectroscopy

In this paper, steady-state fluorescence spectroscopy is used to investigate the curing of two-component epoxy resin LG 285. Moreover, the process of curing is mathematically described. The mixture of resin and hardener HG 287 is measured at five different temperatures (50 °C, 60 °C, 70 °C, 80 °C and 90 °C) for five and a half hours. The results indicate that the process of curing of epoxy resin decelerates with time and accelerates with increasing temperature. Furthermore, the energy of the barrier is calculated.

Europium-Doped Hydroxyapatite: Influence of Excitation Wavelength on the Eu3+ Luminescence in the Hydroxyapatite

2015 ◽  
Vol 820 ◽  
pp. 335-340 ◽  
Author(s):  
Flávia R.O. Silva ◽  
Nelson B. de Lima ◽  
Deiby S. Gouveia ◽  
Nildemar A.M. Ferreira ◽  
Valter Ussui ◽  
...  
Keyword(s):  
Precipitation Method ◽  
Excitation Wavelength ◽  
Careful Evaluation ◽  
Lanthanide Ion ◽  
Site Occupation ◽  
Different Temperatures ◽  
Co Precipitation ◽  
The Eu

Hydroxyapatite (HA) doped with europium (HAEu) offers the advantage of making the hydroxyapatite a fluorescent biomarker, allowing their imaging through emissionin vivoandin vitrotests. Several authors had been based their studies about europium site occupation (CaI and CaII) in hydroxyapatite by the lanthanide ion luminescence, verifying the influence of the method of synthesis and concentration of the dopant ion. In this study HA nanoparticles doped with 1.4 mol% of trivalent europium were synthesized by co-precipitation method and thermal treated at different temperatures (600°C and 1200°C). A careful evaluation of the influence of the excitation wavelength of europium luminescence in the HAEu was performed and it has been verified that both the characteristics transitions of europium, at CaI and CaII sites, and the luminescent intensity are dependent on the excitation wavelength. The non-observance of this fact can lead to erroneous conclusions about the site occupation of europium in hydroxyapatites.

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