IVa — Metalle

Becker, H. A.; Zwicker, Ulrich; Paetz, P.; Sperner, F.

doi:10.1007/978-3-642-80943-9_12

Cited by 5 publications

(2 citation statements)

References 131 publications

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“…All the obtained quantities were compared with reported values estimated by using other techniques. [17][18][19][20][21][22][23][24][25][26][27][28][29] Experimental Apparatus and chemicals.-Figure 2 shows a schematic drawing of the experimental apparatus for electrochemical measurements. Reagent-grade LiCl and KCl (Wako Pure Chemical Co., Ltd.) were dried under vacuum for more than 72 h at 473 K in order to remove water.…”

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confidence: 99%

Thermodynamic Investigation of Ti-H System by Molten Salt Electrochemical Technique

Nishikiori¹,

Ito²

2001

J. Electrochem. Soc.

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There exist numerous investigations on thermodynamic properties of metal-hydrogen, MH, systems both from scientific and industrial interests. Thermodynamic data on MH systems can be derived from pressure-composition-temperature (PCT) measurement, electrode potential-composition-temperature (ECT) measurement, or calorimetry. Among them, ECT measurement is the most direct for determination of thermodynamic data because the relative partial molar Gibbs energy is directly measured. Therefore, this approach has been utilized to estimate thermodynamic properties of MH systems (M ϭ Pd, 1-3 Pd-based alloys, 4-7 and Ni-based alloys 8,9 ). In addition, it only needs very simple apparatus and it is possible to change the hydrogen pressure, even if it is extremely low, instantaneously by controlling the electrode potential. However, the electrochemical approach has a critical disadvantage by its limited temperature range as long as aqueous solutions are used for the electrolyte, so the methods utilizing PCT measurement have been widely employed at high temperatures until now.Concerning the hydrogen source for the electrochemical investigations at high temperatures, H Ϫ ion is produced by dissolution of a saline hydride like LiH in molten salts, such as LiCl-KCl, 10 LiFNaF-KF, 11 and LiI-KI 12 eutectic melts. It is stable in the molten salts and its half-cell reaction, represented by Eq. 1, has been investigated by several research groups 10-14In 1991, Takenaka and Ito 13 found that a small amount of hydrogen was absorbed in an iron electrode by electrochemical anodic oxidation of H Ϫ ion in LiCl-KCl-LiH melts at 673-737 K. By utilizing similar electrochemical hydrogen absorbing reactions in molten salts, it is possible to investigate MH systems at high temperatures. In addition, the use of H Ϫ ion never deprives the advantages of the electrochemical approach. For instance, Ito and Nohira 14 reported that the Ni |H 2 |H Ϫ electrode potential was 0.50 V (vs. Li ϩ /Li) in a molten LiCl-KCl-LiH (2.0 mol % LiH added) system at 673 K. When the Nernst equations applies for this system, hydrogen pressure is equivalent to 3.2 ϫ 10 Ϫ8 atm at an electrode potential of 0 V (vs. Li ϩ /Li), which is the cathodic limit of this melt. It is very difficult for conventional vacuum equipment to achieve such low pressure values.In the present study, the authors have measured detailed ECT relationships of the Ti-H system (TiH x ; 0 < x < 1.8) at 673-773 K. In these experimental conditions, there exist three single phases (␣, ␤, and ␦) and two coexisting phases (␣ ϩ ␤ and ␤ ϩ ␦) according to the phase diagram 15 shown in Fig. 1. The Ti-H system is one of the systems whose thermodynamic properties have been extensively investigated. Nevertheless, few thermodynamic investigations in the high-hydrogen-concentration region were conducted than in the low-hydrogen-concentration region. In this temperature range, Liaw et al. 16 also measured thermodynamic quantities in ␣, ␣ ϩ ␤, and ␤ phases of the Ti-H system by electrochemical methods using LiClKCl-LiH...

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confidence: 99%

Thermodynamic Investigation of Ti-H System by Molten Salt Electrochemical Technique

Nishikiori¹,

Ito²

2001

J. Electrochem. Soc.

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“…The top surface of the test piece after the run E3 appeared to be identifiable as carbo-nitride with comparatively high N content with reference to Table 2 in which the calculated values for the XRD diffraction angle 2θ hkl corresponding to the maximum and the minimum of the lattice parameters, a max and a min , of the non-stoichiometric carbide TiC x and nitride TiN x are listed. The value of a(TiC x ) was reported to rise from 4.294 Å to 4.331 Å on increasing x from 0.55 to 0.85 and then, with further increase of x from 0.85 to 1, a(TiC x ) tended to drop down to 4.327 Å [1,5]. This trend was experimentally proved to be valid for solar-synthesized TiC x carbide phases [6].…”

Section: Resultsmentioning

confidence: 69%

Synthesising Carbo-Nitrides of some D-Group Transition Metals Using a Solar Furnace at PSA

Shohoji

Oliveira

Rosa³

et al. 2012

MSF

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Carbo-nitride synthesis was undertaken using a solar furnace at PSA in flowing N2/Ar gas mixture under total pressure 1 atm and processing temperatureT= 1600°C for some d-group transition elements (Ti; Zr, V, Nb, Mo, W) starting from 1.5G/M (graphite/metal powder mixture with mole ratio 1.5:1) compact to ensure co-presence of free carbon with the reaction product. Clear X-ray diffraction (XRD) evidence of formation of carbo-nitride was detected for Ti (IVa group metal) showing higher N content in the carbo-nitride synthesised in N2gas environment at partial pressurep(N2) = 1 atm than that atp(N2) = 0.5 atm. For M = V and Nb (Va group metals), formation of mono-carbide MC single-phase was detected in the N2environment showing no evidence of formation of carbo-nitride in spite of presence of N2in the environment. For M = Mo and W (VIa group metals), formation of higher carbide, among several options of carbide phases, appeared to be promoted in the N2gas environment although, like in cases with the Va group metals, no evidence of dissolution of N into the reaction product was detected. As such, atT= 1600°C in N2gas environment up top(N2) = 1 atm under concentrated solar beam, carbo-nitride formed from the 1.5G/M mixture only for IVa group metal (Ti) but not for Va and VIa group metals. Anyway, it seemed certain that N2gas affected somehow the reaction path between G and M to yield the carbide phase for M = V, Nb, Mo and W.

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X-ray diffraction characterisation of carbide and carbonitride of Ti and Zr prepared through reaction between metal powders and carbon powders (graphitic or amorphous) in a solar furnace

Fernandes¹,

Amaral²,

Rosa³

et al. 1999

International Journal of Refractory Metals and Hard Materials

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IVa — Metalle

Cited by 5 publications

References 131 publications

Thermodynamic Investigation of Ti-H System by Molten Salt Electrochemical Technique

Thermodynamic Investigation of Ti-H System by Molten Salt Electrochemical Technique

Synthesising Carbo-Nitrides of some D-Group Transition Metals Using a Solar Furnace at PSA

X-ray diffraction characterisation of carbide and carbonitride of Ti and Zr prepared through reaction between metal powders and carbon powders (graphitic or amorphous) in a solar furnace

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