Effect of different alumina sources on phase formation and densification of single-phase mullite ceramic – Reference clay alumina system

2020 ◽  
pp. 101818
Author(s):  
Pallavi Suhasinee Behera ◽  
Sunipa Bhattacharyya
Keyword(s):  
Phase Formation ◽  
Single Phase ◽  
Mullite Ceramic

A review on phase prediction in high entropy alloys

2021 ◽  
pp. 095440622110089
Author(s):  
Vinay Kumar Soni ◽  
S Sanyal ◽  
K Raja Rao ◽  
Sudip K Sinha
Keyword(s):  
Solid Solution ◽  
Phase Formation ◽  
Single Phase ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
Modeling Tools ◽  
High Entropy ◽  
Recent Developments ◽  
Phase Prediction ◽  
The Stability

The formation of single phase solid solution in High Entropy Alloys (HEAs) is essential for the properties of the alloys therefore, numerous approach were proposed by many researchers to predict the stability of single phase solid solution in High Entropy Alloy. The present review examines some of the recent developments while using computational intelligence techniques such as parametric approach, CALPHAD, Machine Learning etc. for prediction of various phase formation in multicomponent high entropy alloys. A detail study of this data-driven approaches pertaining to the understanding of structural and phase formation behaviour of a new class of compositionally complex alloys is done in the present investigation. The advantages and drawbacks of the various computational are also discussed. Finally, this review aims at understanding several computational modeling tools complying the thermodynamic criteria for phase formation of novel HEAs which could possibly deliver superior mechanical properties keeping an aim at advanced engineering applications.

Transparent mullite ceramic from single-phase gel by Spark Plasma Sintering

2009 ◽  
Vol 29 (13) ◽  
pp. 2705-2711 ◽  
Author(s):  
Guimin Zhang ◽  
Yucheng Wang ◽  
Zhengyi Fu ◽  
Hao Wang ◽  
Weiming Wang ◽  
...  
Keyword(s):  
Spark Plasma Sintering ◽  
Single Phase ◽  
Mullite Ceramic ◽  
Plasma Sintering ◽  
Spark Plasma

Role of size, alio-/multi-valency and non-stoichiometry in the synthesis of phase-pure high entropy oxide (Co,Cu,Mg,Na,Ni,Zn)O

2020 ◽  
Vol 49 (21) ◽  
pp. 7123-7132 ◽  
Author(s):  
Nandhini J. Usharani ◽  
Rajat Shringi ◽  
Harshil Sanghavi ◽  
S. Subramanian ◽  
S. S. Bhattacharya
Keyword(s):  
Phase Formation ◽  
Single Phase ◽  
High Entropy ◽  
Phase Pure ◽  
Single Phase Formation

Presence of multivalency/non-stoichiometry to accommodate a different-sized cation and maintaining electroneutrality were identified as the critical criteria for single-phase formation in multicomponent/high entropy systems.

Characterization of NiTi Shape Memory Alloy Sintered at Different Temperatures in Reducing Environment

2020 ◽  
Vol 1010 ◽  
pp. 632-637
Author(s):  
Hafizah Hanim Mohd Zaki ◽  
Nur Azemuzahir Mohd Sobri ◽  
Jamaluddin Abdullah ◽  
Norshahida Sariffudin ◽  
Farah Diana Mohd Daud
Keyword(s):  
Solid State ◽  
Shape Memory ◽  
Phase Formation ◽  
Single Phase ◽  
Reducing Agent ◽  
Niti Shape Memory Alloy ◽  
Transformation Behavior ◽  
Formidable Challenge ◽  
Different Temperatures ◽  
Reducing Environment

NiTi has received significant interest as medical implant materials due to its shape memory effect behavior apart from its good biocompatibility and mechanical properties. The formidable challenge of obtaining single phase NiTi from elemental powders via solid state is due to oxidation problem of elemental powders and the oxygen atoms dissolve in NiTi matrix as interstitial impurities forming stable oxygen-rich TiNiOx. This may deterioriate the shape memory behavior of NiTi. This research investigates the use of MgH2 in combination with CaH2 as in-situ reducing agent to eliminate oxidation of the specimen during sintering both at lower and higher sintering temperatures. Here, the effect of sintering temperature on phase formation and transformation behavior of NiTi in reducing environment was studied. The phase formation was characterized by using x-ray diffraction (XRD) where the morphology and elemental analysis were characterized by using the scanning electron microscope (SEM) equipped with EDS. The martensitic transformation behavior was analyzed using differential scanning calorimeter (DSC). The use of MgH2 and CaH2 as reducing agent has a significant influence on the phase formation of NiTi synthesized via solid state especially at 930 °C, where almost single phase NiTi was formed with good transformation behavior. This reducing agent creates a conducive environment for the production of single phase NiTi.

Mixed Si/Ge Apatite-Type Phase Produced by Mechanical Alloying

2008 ◽  
Vol 587-588 ◽  
pp. 128-132 ◽  
Author(s):  
Milena M. Vieira ◽  
Joao C. de Oliveira ◽  
Albano Cavaleiro ◽  
Bruno Trindade
Keyword(s):  
Mechanical Alloying ◽  
Phase Formation ◽  
Single Phase ◽  
Rotation Speed ◽  
Raw Material ◽  
Partial Substitution ◽  
Apatite Phase ◽  
High Rotation Speed ◽  
Time Required ◽  
Apatite Type

The aim of the present work is to study the influence of the partial substitution of Si by Ge on the formation of the apatite-type La9.33Si2Ge4O26 phase by mechanical alloying and subsequent annealing. Powders of La2O3, GeO2 and SiO2 were dry milled in a planetary ball milling at increasing rotation speeds of 150, 250 and 350 rpm and milling times up to 50 h. The resulting mixtures were subsequently annealed at increasing temperatures up to 1100 °C. Single phase apatite-like La9.33Si2Ge4O26 was obtained during mechanical alloying at high rotation speed. The higher the rotation speed the lower was the time required for the lanthanum germanosilicate phase formation. For the samples in which complete reaction between initial phases did not occur during milling, La9.33Si2Ge4O26 was always obtained during the annealing process. The more severe was the mechanical alloying process the lower was the annealing temperature required for the apatite phase formation. The formation of apatite phase during mechanical alloying did not provoke significant changes in densification behavior of the milled samples. The addition of GeO2 as raw material promotes a faster formation of the apatite phase as compared to the results obtained using only La2O3 and SiO2.

ALLOY PHASE FORMATION BY MECHANICAL ALLOYING: CONSTRAINTS AND MECHANISMS

1992 ◽  
Vol 06 (03) ◽  
pp. 127-138 ◽  
Author(s):  
E. MA ◽  
M. ATZMON
Keyword(s):  
Mechanical Alloying ◽  
Phase Formation ◽  
Single Phase ◽  
Metastable Phase ◽  
Interfacial Free Energy ◽  
Metastable Equilibrium ◽  
Heat Of Mixing ◽  
Layered Composites ◽  
Two Phase ◽  
Equilibrium Phases

Alloy phase formation in binary metallic systems by mechanical alloying (MA) of elemental powders is briefly reviewed. Our recent results indicate the inadequacy of the current understanding of the MA process, which has been depicted as an isothermal solid-state interdiffusion reaction under interfacial, metastable, equilibrium in layered composites. A structural and thermodynamic analysis of the supersaturation followed by amorphization in the Zr-Al system demonstrates that a system can be constrained to be a single phase without reaching two-phase (metastable) equilibrium during MA. Alloying, resulting in a single metastable phase, has also been achieved in immiscible systems with positive heat of mixing, such as Fe-Cu. In both cases, the interfacial free energy associated with a repeatedly deformed, fine-structured, two-phase alloy appears to pose polymorphous constraints. In addition, equilibrium phases can be formed during MA in an exothermic, self-sustained fashion, as observed for the formation of AlNi. Al-Ni phases formed under different milling conditions suggest that self-sustained reactions may occur, undetected, on a grain-by-grain basis.

Study on the Phase Formation of Corundum-Type Mg4Nb2O9 Powders by the Solid-State Process

2012 ◽  
Vol 499 ◽  
pp. 174-177
Author(s):  
Yi Shan Jiang ◽  
Ying Zi Wang ◽  
Ya Ming Chen ◽  
Yun Long Yue ◽  
Hai Tao Wu
Keyword(s):  
Phase Composition ◽  
Solid State ◽  
Phase Formation ◽  
Single Phase ◽  
Magnesium Niobate ◽  
Calcination Temperatures ◽  
Air Atmosphere ◽  
State Process

The corundum-type magnesium niobate, Mg4Nb2O9, powders were synthesized by the conventional solid-state process. The mixtures of MgO and Nb2O5were calcined in the temperature ranging from 500°C to 1200°C for crystallization in air atmosphere. The formation of the Mg4Nb2O9phase was investigated as a function of calcination temperatures by DTA and XRD. The morphology and phase composition were determined via a combination of SEM and EDX techniques. The results showed that the single-phase Mg4Nb2O9could be obtained at 1050°C for 2h with the size of less than 5μm.

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