A Study of Thermal Stability of Hydroxyapatite

High-temperature powder sintering is an integral part of the dense ceramic manufacturing process. In order to find the optimal conditions for producing a ceramic product, the information about its behavior at high temperatures is required. However, the data available in the literature are very contradictory. In this work, the thermal stability of hydroxyapatite prepared by a solid-state mechanochemical method and structural changes occurring during sintering were studied. Stoichiometric hydroxyapatite was found to remain as a single-phase apatite structure with the space group P63/m up to 1300 °C inclusively. A further increase in the sintering temperature leads to its partial decomposition, a decrease in the crystallite size of the apatite phase, and the appearance of significant structural strains. It was shown that small deviations from stoichiometry in the Ca/P ratio upward or downward during the hydroxyapatite synthesis lead to a significant decrease in the thermal stability of hydroxyapatite. An apatite containing almost no hydroxyl groups, which is close to the composition of oxyapatite, was prepared. It was shown that the congruent melting of stoichiometric hydroxyapatite upon slow heating in a high-temperature furnace does not occur. At the same time, the fast heating of hydroxyapatite by laser radiation allows, under certain conditions, its congruent melting with the formation of a recrystallized monolayer of oxyhydroxyapatite. The data obtained in this study can be used when choosing sintering conditions to produce hydroxyapatite-based ceramics.

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Role of Ionic Headgroups on the Thermal, Rheological, and Foaming Properties of Novel Betaine-Based Polyoxyethylene Zwitterionic Surfactants for Enhanced Oil Recovery

Processes ◽

10.3390/pr7120908 ◽

2019 ◽

Vol 7 (12) ◽

pp. 908 ◽

Cited By ~ 3

Author(s):

Muhammad Shahzad Kamal ◽

Syed Muhammad Shakil Hussain ◽

Lionel Talley Fogang

Keyword(s):

Thermal Stability ◽

High Temperature ◽

Oil Recovery ◽

Structural Changes ◽

Foam Stability ◽

Foaming Properties ◽

Zwitterionic Surfactants ◽

Reservoir Conditions ◽

Thermal Stability Of

Long-term thermal stability of surfactants under harsh reservoir conditions is one of the main challenges for surfactant injection. Most of the commercially available surfactants thermally degrade or precipitate when exposed to high-temperature and high-salinity conditions. In this work, we designed and synthesized three novel betaine-based polyoxyethylene zwitterionic surfactants containing different head groups (carboxybetaine, sulfobetaine, and hydroxysulfobetaine) and bearing an unsaturated tail. The impact of the surfactant head group on the long-term thermal stability, foam stability, and surfactant–polymer interactions were examined. The thermal stability of the surfactants was assessed by monitoring the structural changes when exposed at high temperature (90 °C) for three months using 1H-NMR, 13C-NMR, and FTIR analysis. All surfactants were found thermally stable regardless of the headgroup and no structural changes were evidenced. The surfactant–polymer interactions were dominant in deionized water. However, in seawater, the surfactant addition had no effect on the rheological properties. Similarly, changing the headgroup of polyoxyethylene zwitterionic surfactants had no major effect on the foamability and foam stability. The findings of the present study reveal that the betaine-based polyoxyethylene zwitterionic surfactant can be a good choice for enhanced oil recovery application and the nature of the headgroup has no major impact on the thermal, rheological, and foaming properties of the surfactant in typical harsh reservoir conditions (high salinity, high temperature).

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The Ordered Phase Formation in Ti-Al-Ga Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069193 ◽

1970 ◽

Vol 28 ◽

pp. 440-441

Author(s):

Shiro Fujishiro ◽

Harold L. Gegel

Keyword(s):

Thermal Stability ◽

High Temperature ◽

Titanium Alloys ◽

Growth Kinetics ◽

Stoichiometric Composition ◽

Good Potential ◽

Alpha Titanium ◽

Cold Rolled ◽

Kinetics Of ◽

Thermal Stability Of

Ordered-alpha titanium alloys having a DO19 type structure have good potential for high temperature (600°C) applications, due to the thermal stability of the ordered phase and the inherent resistance to recrystallization of these alloys. Five different Ti-Al-Ga alloys consisting of equal atomic percents of aluminum and gallium solute additions up to the stoichiometric composition, Ti3(Al, Ga), were used to study the growth kinetics of the ordered phase and the nature of its interface.The alloys were homogenized in the beta region in a vacuum of about 5×10-7 torr, furnace cooled; reheated in air to 50°C below the alpha transus for hot working. The alloys were subsequently acid cleaned, annealed in vacuo, and cold rolled to about. 050 inch prior to additional homogenization

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High-Temperature Oxidation Resistance and Thermal Stability of Higher Manganese Silicide Powder Synthesized by Pack Cementation

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2021.159842 ◽

2021 ◽

pp. 159842

Author(s):

Aikaterini Teknetzi ◽

Evangelia Tarani ◽

Dimitrios Stathokostopoulos ◽

Dimitrios Karfaridis ◽

Konstantinos Chrissafis ◽

...

Keyword(s):

Thermal Stability ◽

High Temperature ◽

Oxidation Resistance ◽

High Temperature Oxidation ◽

Pack Cementation ◽

Higher Manganese Silicide ◽

Temperature Oxidation ◽

Manganese Silicide ◽

Thermal Stability Of

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Enhanced high-temperature performance and thermal stability of lithium-rich cathode via combining full concentration gradient design with surface spinel modification

Chemical Engineering Journal ◽

10.1016/j.cej.2021.129042 ◽

2021 ◽

Vol 415 ◽

pp. 129042

Author(s):

Naifang Hu ◽

Chi Zhang ◽

Kaifang Song ◽

Hui Wu ◽

Puheng Yang ◽

...

Keyword(s):

Thermal Stability ◽

High Temperature ◽

Concentration Gradient ◽

Temperature Performance ◽

Thermal Stability Of

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Improved Hydrophobicity of Macroalgae Biopolymer Film Incorporated with Kenaf Derived CNF Using Silane Coupling Agent

Molecules ◽

10.3390/molecules26082254 ◽

2021 ◽

Vol 26 (8) ◽

pp. 2254

Author(s):

Adeleke A. Oyekanmi ◽

N. I. Saharudin ◽

Che Mohamad Hazwan ◽

Abdul Khalil H. P. S. ◽

Niyi G. Olaiya ◽

...

Keyword(s):

Thermal Stability ◽

Coupling Agent ◽

Silane Coupling Agent ◽

Cellulose Nanofibrils ◽

Hydroxyl Groups ◽

Water Contact ◽

Silane Coupling ◽

Cnf Films ◽

Kenaf Bast ◽

Thermal Stability Of

Hydrophilic behaviour of carrageenan macroalgae biopolymer, due to hydroxyl groups, has limited its applications, especially for packaging. In this study, macroalgae were reinforced with cellulose nanofibrils (CNFs) isolated from kenaf bast fibres. The macroalgae CNF film was after that treated with silane for hydrophobicity enhancement. The wettability and functional properties of unmodified macroalgae CNF films were compared with silane-modified macroalgae CNF films. Characterisation of the unmodified and modified biopolymers films was investigated. The atomic force microscope (AFM), SEM morphology, tensile properties, water contact angle, and thermal behaviour of the biofilms showed that the incorporation of Kenaf bast CNF remarkably increased the strength, moisture resistance, and thermal stability of the macroalgae biopolymer films. Moreover, the films’ modification using a silane coupling agent further enhanced the strength and thermal stability of the films apart from improved water-resistance of the biopolymer films compared to unmodified films. The morphology and AFM showed good interfacial interaction of the components of the biopolymer films. The modified biopolymer films exhibited significantly improved hydrophobic properties compared to the unmodified films due to the enhanced dispersion resulting from the silane treatment. The improved biopolymer films can potentially be utilised as packaging materials.

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Increased Thermal Stability of Co-silicide Using Co-Ta Alloy Films

MRS Proceedings ◽

10.1557/proc-670-k6.5 ◽

2001 ◽

Vol 670 ◽

Author(s):

Min-Joo Kim ◽

Hyo-Jick Choi ◽

Dae-Hong Ko ◽

Ja-Hum Ku ◽

Siyoung Choi ◽

...

Keyword(s):

Thermal Stability ◽

High Temperature ◽

Grain Boundary ◽

Reaction Rate ◽

Boundary Migration ◽

Grain Boundary Migration ◽

Alloy Films ◽

Post Annealing ◽

Alloy Process ◽

Thermal Stability Of

ABSTRACTThe silicidation reactions and thermal stability of Co silicide formed from Co-Ta/Si systems have been investigated. In case of Co-Ta alloy process, the formation of low resistive CoSi2phase is delayed to about 660°C, as compared to conventional Co/Si system. Moreover, the presence of Ta in Co-Ta alloy films reduces the silicidation reaction rate, resulting in the strong preferential orientation in CoSi2 films. Upon high temperature post annealing in the furnace, the sheet resistance of Co-silicide formed from Co/Si systems increases significantly, while that of Co-Ta/Si systems maintains low. This is due to the formation of TaSi2 at the grain boundaries and surface of Co-silicide films, which prevents the grain boundary migration thereby slowing the agglomeration. Therefore, from our research, increased thermal stability of Co-silicide films was successfully obtained from Co-Ta alloy process.

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Thermal stability of nickel-cobalt multilayer silicide

MRS Proceedings ◽

10.1557/proc-0891-ee07-29 ◽

2005 ◽

Vol 891 ◽

Author(s):

Kil Jin Han ◽

Yu Jung Cho ◽

Soon Young Oh ◽

Yong Jin Kim ◽

Won Jae Lee ◽

...

Keyword(s):

Thermal Stability ◽

High Temperature ◽

Depth Profile ◽

Ternary Phase ◽

Nickel Silicide ◽

Composition Gradient ◽

Cobalt Silicide ◽

Nickel Cobalt ◽

Thermal Stability Of ◽

Xps Depth Profile

ABSTRACTIn this study, we have investigated the structure of nickel-cobalt silicide to understand its behavior at high temperature. Nickel-cobalt silicide was formed after two-step RTP at 500°C and 700°C respectively. We could observe by TEM that nickel-cobalt silicide consists of a structure which seems to be a Ni-Co-Si ternary phase. No nickel silicide phases and cobalt silicide phases were detected in nickel-cobalt silicide by XRD. From XPS depth profile, we could confirm that there is a cobalt composition gradient along the silicide.

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Enhanced Thermal Stability of Esterified Lignin in Different Solvent Mediums

Polymers from Renewable Resources ◽

10.1177/204124791800900103 ◽

2018 ◽

Vol 9 (1) ◽

pp. 39-49 ◽

Cited By ~ 1

Author(s):

Sharifah Nurul Ain Syed Hashim ◽

Sarani Zakaria ◽

Chin Hua Chia ◽

Sharifah Nabihah Syed Jaafar

Keyword(s):

Thermal Stability ◽

Alkaline Solution ◽

Room Temperature ◽

Hydroxyl Groups ◽

Aqueous Alkaline Solution ◽

Alkali Lignin ◽

Weight Percentage ◽

H Nmr ◽

Ft Ir ◽

Thermal Stability Of

In this study, soda alkali lignin from oil palm empty fruit bunch (EFB-AL) and kenaf core (KC-AL) are esterified with maleic anhydride under two different conditions, namely i) pyridine at temperature of 120°C for 3h and ii) aqueous alkaline solution at room temperature for 4h. As a result, the weight percentage gain (WPG) of the esterified EFB-AL (EFB-EL) and esterified KC-AL (KC-EL) in pyridine demonstrated a higher compared to aqueous alkaline solution. The FT-IR results of EFB-EL and KC-EL in both solvents exhibited some changes at the carbonyl and hydroxyl groups. Furthermore, the esterification process induced the carboxylic peak to appear in both alkali lignin samples. The outcome is confirmed by conducting H-NMR analysis, which demonstrated ester and carboxylic acid peaks within the spectral analysis. Finally, the TGA results showed both EFB-EL and KC-EL that are exposed to aqueous alkaline actually possessed better thermal stability and higher activation energy (Ea) compared to the esterified samples in pyridine.

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