scholarly journals Preparation of Single-phase High Entropy Carbides by a Modified Citric Acid Complexing Method

2021 ◽  
Author(s):  
Hu-Lin Liu ◽  
Feng-Zhen DANG ◽  
De-Wei NI ◽  
Chang-Qing LIU ◽  
Yun-Long XUE ◽  
...  
Keyword(s):  
Citric Acid ◽  
Single Phase ◽  
Raw Materials ◽  
Low Cost ◽  
Transition Metal Carbide ◽  
Synthesis Process ◽  
Step Process ◽  
High Entropy ◽  
One Step ◽  
Sluggish Diffusion

Abstract We developed a new method to synthesize single-phase transition metal carbide powders by combining citric acid complexing method and ball-milling dispersion. High-entropy carbides (Zr0.25Ti0.25Ta0.25Nb0.25)C (4TmC), (Zr0.2Ti0.2Ta0.2Nb0.2Hf0.2)C (5TmC-H) and (Zr0.2Ti0.2Ta0.2Nb0.2Mo0.2)C (5TmC-M) were successfully fabricated by this method using low-cost raw materials. The element and phase composition and microstructures of the obtained carbide powders were investigated. The relationships of synthesis process and temperature with chemical composition were also discussed. (Zr0.25Ti0.25Ta0.25Nb0.25)C can be obtained by a one-step process at 1550 °C, while (Zr0.2Ti0.2Ta0.2Nb0.2Hf0.2)C and (Zr0.2Ti0.2Ta0.2Nb0.2Mo0.2)C are fabricated by a two-step process of carbothermal reduction followed by solid solution at the temperatures not lower than 1850 °C and 1650 °C. The higher synthesis temperatures of the five-component carbides are attributed to the obvious sluggish diffusion effect induced by the larger lattice distortions. The particle sizes of (Zr0.25Ti0.25Ta0.25Nb0.25)C, (Zr0.2Ti0.2Ta0.2Nb0.2Hf0.2)C and (Zr0.2Ti0.2Ta0.2Nb0.2Mo0.2)C powders are 118.2±26.1 nm (at 1550 °C), 284.8±73.7 nm (at 1850 °C) and 65.5±13.9 nm (at 1750 °C), respectively.

scholarly journals Al, Cu and Zr Addition to High Entropy Alloys: The Effect on Recrystallization Temperature

2018 ◽  
Vol 941 ◽  
pp. 1137-1142
Author(s):  
Elena Colombini ◽  
Andrea Garzoni ◽  
Roberto Giovanardi ◽  
Paolo Veronesi ◽  
Angelo Casagrande
Keyword(s):  
Solid Solution ◽  
Grain Size ◽  
Single Phase ◽  
Boundary Energy ◽  
Cold Deformation ◽  
Recrystallization Temperature ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Ni Alloy ◽  
Sluggish Diffusion

The equimolar Cr, Mn, Fe, Co and Ni alloy, first produced in 2004, was unexpectedly found to be single-phase. Consequently, a new concept of materials was developed: high entropy alloys (HEA) forming a single solid-solution with a near equiatomic composition of the constituting elements. In this study, an equimolar CoCrFeMnNi HEA was modified by the addition of 5 at% of either Al, Cu or Zr. The cold-rolled alloys were annealed for 30 minutes at high temperature to investigate the recrystallization kinetics. The evolution of the grain boundary and the grain size were investigated, from the as-cast to the recrystallized state. Results show that the recrystallized single phase FCC structures exhibits different twin grains density, grain size and recrystallization temperatures as a function of the at.% of modifier alloying elements added. In comparison to the equimolar CoCrFeMnNi, the addition of modifier elements increases significantly the recrystallization temperature after cold deformation. The sluggish diffusion (typical of HEA alloys), the presence of a solute in solid solution as well as the low twin boundary energy are responsible for the lower driving force for recrystallization.

The AA* + B*B2 approach A simple and convenient synthetic strategy towards hyperbranched polyurea-urethanes

e-Polymers ◽  
2003 ◽  
Vol 3 (1) ◽  
Author(s):  
Bernd Bruchmann ◽  
Wolfgang Schrepp
Keyword(s):  
Functional Groups ◽  
Raw Materials ◽  
Protecting Groups ◽  
Isophorone Diisocyanate ◽  
Step Process ◽  
Synthetic Strategy ◽  
One Step

Abstract Synthesizing hyperbranched polyurethanes in a one step process using commercially available raw materials: these were the primary conditions for this work. By taking advantage of intramolecular reactivity differences of isocyanate groups in diisocyanates in combination with reactivity differences of OH and NH groups in alkanolamines, it is possible to generate in situ AB2 molecules by controlling reactions of specific functional groups towards each other. This AA* + B*B2 approach works without protecting groups and opens up a simple and versatile strategy towards hyperbranched aromatic as well as aliphatic polyureaurethanes. Preferential diisocyanates for this synthesis were 2,4-toluylene diisocyanate and isophorone diisocyanate, whereas diethanolamine and diisopropanolamine were used as isocyanate-reactive counterparts.

Preparation of Delafossite CuYO2 by Metal-citric Acid Complex Decomposition Method

2009 ◽  
Vol 1166 ◽  
Author(s):  
Keishi Nishio ◽  
Tomomi Okada ◽  
Naoto Kikuchi ◽  
Satoshi Mikusu ◽  
Tsutomu Iida ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Citric Acid ◽  
Single Phase ◽  
Raw Materials ◽  
Chelating Agent ◽  
Amorphous Powder ◽  
Heat Treating ◽  
Acid Complex ◽  
Synthesis Conditions ◽  
Starting Solution

AbstractDelafossite CuYO2 and Ca doped CuYO2 were prepared by thermal decomposition of a metal-citric acid complex. The starting solution consisted of Cu acetate, Y acetate and Ca acetate as the raw materials. Citric acid was used as the chelating agent, and acetic acid and distilled water were mixed as a solvent. The starting solutions were heated at 723 K for 5 h after drying at 353 K. The obtained powders were amorphous and single phase of orthorhombic Cu2Y2O5 was obtained by heat-treated the amorphous powder at a temperature range between 1073 and 1373 K for 3 h in air. Furthermore, Heat-treating the obtained orthorhombic Cu2Y2O5 at above 1373 K in air caused it to decompose into Y2O3, CuO and Cu2O. On the other hand, the sample powder prepared from a starting solution without citric acid, i.e., single phase of orthorhombic Cu2Y2O5 could not be obtained under the same synthesis conditions as that for a solution with citric acid. We were able to obtain delafossite CuYO2 and Ca doped CuYO2 from orthorhombic Cu2Y2O5 under a low O2 pressure atmosphere at above 1223 K. The obtained delafossite CuYO2 composed hexagonal and rhombohedral phases. The color of the CuYO2 powder was light brown and that of Ca-doped CuYO2 was light green. Diffraction peaks in the XRD pattern were slightly shifted by doping Ca for CuYO2, and these peaks shifted toward to a high diffraction angle with an increasing amount of doped Ca. From these results, we concluded that Ca doped delafossite CuYO2 could be obtained by thermal decomposition of a metal-citric acid complex.

scholarly journals Development of a TiNbTaMoZr-Based High Entropy Alloy with Low Young´s Modulus by Mechanical Alloying Route

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1463 ◽  
Author(s):  
Juliette Normand ◽  
Rocío Moriche ◽  
Cristina García-Garrido ◽  
Ranier Enrique Sepúlveda Ferrer ◽  
Ernesto Chicardi
Keyword(s):  
Milling Time ◽  
Raw Materials ◽  
Stress Shielding ◽  
High Hardness ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Heating And Cooling ◽  
Commercially Pure ◽  
One Step ◽  
Cp Ti

In this work, an equiatomic TiNbTaMoZr-based high-entropy alloy (HEA) has been developed by a powder metallurgy route, which consists of a process of combined one-step low-temperature mechanical milling starting from the transition metals as raw materials and a subsequent pressureless sintering. In this way, the optimized synthesized specimen, after 10 h of milling time, showed two different body-centered cubic (bcc) TiNbTaMoZr alloys, which, after sintering at 1450 °C, 1 h of dwell time and a heating and cooling rate of 5 °C min−1, it remained formed as two bcc TiNbTaMoZr-based HEAs. This material, with micrometric and equiaxed particles, and with homogeneously distributed phases, presented a Young’s modulus that was significantly higher (5.8 GPa) and lower (62.1 GPa) than that of the usual commercially pure (cp) Ti and Ti6Al4V alloy used for bone-replacement implants. It also presented similar values to those of the HEAs developed for the same purpose. These interesting properties would enable this TiNbTaMoZr-based HEA to be used as a potential biomaterial for bulk or porous bone implants with high hardness and low Young´s modulus, thereby preventing the appearance of stress-shielding phenomena.

scholarly journals Photocatalytic activity of exfoliated graphite–TiO2 nanoparticle composites

Nanoscale ◽  
2019 ◽  
Vol 11 (41) ◽  
pp. 19301-19314 ◽  
Author(s):  
Gloria Guidetti ◽  
Eva A. A. Pogna ◽  
Lucia Lombardi ◽  
Flavia Tomarchio ◽  
Iryna Polishchuk ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Liquid Phase ◽  
Atmospheric Pressure ◽  
Photocatalytic Performance ◽  
Low Cost ◽  
Exfoliated Graphite ◽  
Step Process ◽  
One Step ◽  
Liquid Phase Exfoliation ◽  
Nanoparticle Composites

We report the photocatalytic performance of composites prepared in a one-step process by liquid phase exfoliation of graphite and TiO2 at atmospheric pressure and in water, without heat or surfactants, starting from low-cost commercial reagents.

Primary Study on the Improvement and Application of Formulation Optimization of 2116# Rosin Modified Phenolic Resin

2020 ◽  
Vol 837 ◽  
pp. 168-173
Author(s):  
Qing Zhang ◽  
Li Li Huang ◽  
Mei Ye Wu ◽  
Xiao Zhang Yu
Keyword(s):  
Bisphenol A ◽  
Performance Indicators ◽  
Phenolic Resin ◽  
Raw Materials ◽  
Primary Study ◽  
Step Process ◽  
Technical Performance ◽  
Coating Industry ◽  
One Step ◽  
Printing Ink

2116# Rosin Modified Phenolic Resin is synthesized by means of one-step process taking calcium hydroxide as catalyst and Rosin, Bisphenol A, solid formaldehyde and glycerol as main raw materials. The formulation and process are improved and characterized. The result shows that it satisfies technical performance indicators. And, it is preliminarily applied to ink. This resin is expected to be applied to printing ink and coating industry.

Application of Response Surface Methodology for Improving the Yield of 1,5-bis(ptoluenesulfonyl)- 3,7-Dihydroxyoctahydro-1,5-Diazocine

2019 ◽  
Vol 16 (3) ◽  
pp. 398-404 ◽  
Author(s):  
Yang Zou ◽  
Jingyi Fei ◽  
Liangzhe Chen ◽  
Qingfeng Dong ◽  
Houbin Li
Keyword(s):  
Response Surface Methodology ◽  
Response Surface ◽  
Raw Materials ◽  
Low Cost ◽  
Product Yield ◽  
Synthesis Process ◽  
Optimal Conditions ◽  
Experimental Conditions ◽  
Simple Method ◽  
Ft Ir

Background: 3,3,7,7-tetrakis (difluoramino) octahydro-1,5-dinitro-1,5-diazocine (HNFX), as an important oxidizer in propellants, has received much attention due to its high density and energy. However, there are many difficulties that need to be solved, such as complex synthetic processes, low product yield, high cost of raw materials and complicated purification. In the synthesis of HNFX, the intermediate named 1,5-bis (p-toluenesulfonyl)-3,7-dihydroxyoctahydro-1, 5-diazocine (gem-diol), is difficult to synthesize. Methods: A simple method was used to synthesize the gem-diol. This prepared gem-diol was characterized by FT-IR, 1H NMR, melting point and mass spectrometry. In order to increase the yield of gem-diol, response surface methodology (RSM) was introduced to optimize experimental conditions. Results: After the establishment of the model, the optimal conditions of synthesis were found to be 9.33h for reaction time, 6.13wt. % for the concentration of NaOH and 1.38:1 for ratio of ECH (p-toluenesulfonamide): TCA (epichlorohydrin). Under the optimal conditions, the experimental value and the predicted value of yield were 22.18% and 22.92%, respectively. Conclusion: 1,5-bis (p-toluenesulfonyl)-3,7-dihydroxyoctahydro-1,5-diazocine (gem-diol) can be synthesized using the low cost of chemical materials, including p-toluenesulfonamide, epichlorohydrin, sodium hydroxide and ethanol. Response surface methodology (RSM) is an effective method to optimize the synthesis process, thereby improving the yield of gem-diol.

Preparation of Forsterite by Solid State Synthesis Process and its Dielectric Properties

2012 ◽  
Vol 534 ◽  
pp. 110-113 ◽  
Author(s):  
Fei Shi ◽  
Peng Cheng Du ◽  
Jing Xiao Liu ◽  
Ji Wei Wu ◽  
Chun Yuan Luo
Keyword(s):  
Dielectric Properties ◽  
Solid State ◽  
Single Phase ◽  
Raw Materials ◽  
Magnesium Carbonate ◽  
Solid State Synthesis ◽  
Molar Ratio ◽  
Synthesis Process ◽  
X Ray Diffraction ◽  
X Ray

Using basic magnesium carbonate (Mg(OH)2•4MgCO3•6H2O) and SiO2 as raw materials, forsterite (Mg2SiO4) was prepared by solid state synthesis process. The optimal process for synthesizing Mg2SiO4 was obtained by adjusting Mg/Si molar ratio and sintering temperature. The crystal phase of the obtained Mg2SiO4 powder was determined by X-ray diffraction (XRD). The results indicate that the single-phase Mg2SiO4 powder can be obtained when the mixtures with Mg/Si molar ratio of 2.05～2.01 were sintered at 1350°C for 3h in the air. The as-prepared Mg2SiO4 ceramic samples which were sintered at 1300～1360°C showed better dielectric properties with εr=7.4 and tanδ =7.5×10-4.

Preparation and Properties of Srn+1TinO3n+1 Ruddlesden-Popper Homologous Series by Metal-Citric Acid Complex Decomposition Method

2007 ◽  
Vol 1044 ◽  
Author(s):  
Keishi Nishio ◽  
Kazuhiko Fukuda ◽  
Tomohiro Imai ◽  
Hirohumi Takenouchi ◽  
Hideo Mae ◽  
...  
Keyword(s):  
Citric Acid ◽  
Homologous Series ◽  
Single Phase ◽  
Raw Materials ◽  
Chelating Agent ◽  
Uniaxial Pressure ◽  
Acid Complex ◽  
Starting Solution ◽  
Wide Range ◽  
High Dielectric

AbstractWe investigated the Srn+1TinO3n+1 Ruddlesden-Popper homologous series. This material exhibits a wide range of electric behaviors, from a high-dielectric-constant tunable-paraelectric in its undoped form to a metallic superconductor when it is doped with a variety of elements.The Srn+1TinO3n+1 and the yttrium-doped Srn+1TinO3n+1 Ruddlesden-Popper homologous series were prepared through the thermal decomposition of a metal citric acid complex. The starting solution consisted of the raw materials strontium acetate and titanium alkoxide. Citric acid was used as the chelating agent, and ethanol and distilled water were mixed and used as a solvent. Single phase Sr2TiO4 and Sr3Ti2O7 were produced without creation of SrCO3 by heat-treatment at 1073 and 1473 K, respectively, for three hours. We were unable to produce single phase Sr4Ti3O10. The samples consisted of Sr4Ti3O10 and SrTiO3 phases. Scanning electron microscopy showed that the grain shape of the Sr2TiO4 was plate-like, while those of the Sr3Ti2O7 and Sr4Ti3O10 were not and the grains had large numbers of pores. High-density Sr2-xYxTiO4 (x= 0 to 0.06) ceramic samples were produced under hot-press conditions (1823 K for one hour at a uniaxial pressure of 31.2 MPa). Although the undoped samples were insulators, the yttrium-doped samples showed high electrical conductivity (i.e. that of Sr1.98Y0.02TiO4 was ρ= 8.5×10−5 Ωcm). The Seebeck coefficient of Sr1.98Y0.02TiO4 was –160.7 μV/K, and the thermal conductivity was 3.38 W/mK.

Performance of LiFePO4 Cathode Material Synthesized by a Low-Cost and Safe Method

2012 ◽  
Vol 538-541 ◽  
pp. 3003-3007
Author(s):  
Zhi Hua Li ◽  
Shan Chen ◽  
Bin Bin Xu
Keyword(s):  
Raw Materials ◽  
Low Cost ◽  
Specific Capacity ◽  
Synthesis Process ◽  
Protective Atmosphere ◽  
Excellent Performance ◽  
Solid State Method ◽  
Carbon Coated ◽  
Synthesis Approach ◽  
Initial Capacity

In order to decrease the synthesis costs and resolve safety care in synthesis process of LiFePO4, a novel synthesis approach was put forward. Instead of traditional reduction atmosphere Ar/H2(95%/5%), the reducing flow produced by the breakdown of sucrose independently is used as protective atmosphere. Then, carbon-coated LiFePO4 samples were synthesized by solid-state method using Li3PO4, FePO4, Fe powder as the raw materials, and sucrose as the carbon source. The results show that the LiFePO4/C sample in this flow exhibits excellent performance after 7 hours’ sintering at 650°C. It had an initial capacity of 141.8mAh/g at 16mA/g discharge current and the coulomb efficiency reached 98.95%. Furthermore, the specific capacity was almost not fade after 20 cycles. Our experiment results prove that our approach can replace the traditional atmosphere Ar/H2, and it helps reducing the energy consumption and cost, and is expected to be commercially feasible in the future.

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