Well-known Experts
Da Liu, Qiangang Fu, Yanhui Chu 2022-01-06
Abstract: Nanocrystalline HfB2 powders were successfully synthesized by molten salt synthesis technique at 1373 K using B and HfO2 as precursors within KCl/NaCl molten salts. The results showed that the as-synthesized powders exhibited an irregular polyhedral morphology with the average particle size of 155 nm and possessed a single-crystalline structure. From a fundamental aspect, we demonstrated the molten-salt assisted formation mechanism that the molten salts could accelerate the diffusion rate of the reactants and improve the chemical reaction rate of the reactants in the system to induce the synthesis of the high-purity nanocrystalline powders. Thermogravimetric analysis showed that the oxidation of the as-synthesized HfB2 powders at 773–1073 K in air was the weight gain process and the corresponding oxidation behavior followed parabolic kinetics governed by the diffusion of oxygen in the oxide layer.
Keywords: ultra-high temperature ceramics; powders; molten salt synthesis; oxidation behavior
As members of ultra-high temperature ceramics, transition-metal borides (TMB2) ceramics have attracted considerable attentions for potential applications in aircraft, atomic, and astronautic manufacturing industries, since they exhibit high melting point, high hardness, high thermal conductivity, and excellent chemical stability [1–3]. The synthesis of TMB2 powders is critical for implementing their extensive applications. Up to now, a variety of techniques have been developed to synthesize TMB2 powders, such as mechanochemically assisted method [4–7], carbo/borothermal reduction [8–10], sol–gel method [11–13], and so on. However, the reported techniques for synthesizing TMB2 powders have some shortcomings, such as the high synthesis temperatures and expensive reaction precursors. In addition, the as-obtained powders possess the large
particle size. Therefore, a low temperature technique for synthesizing TMB2 ultrafine powders is of vital importance for implementing the extensive applications of TMB2 ceramics. Recently, a low temperature molten salt synthesis technique has been proposed to synthesize TMB2 ultrafine powders including NbB2 [14], TiB2 [15], and CrB2 [16]. Nevertheless, the current understanding of the molten-salt assisted formation mechanism is yet limited, and the synthesis of much more TMB2 ultrafine powders by the molten salt synthesis technique has rarely been reported until now. In addition, there is seldom report so far on the oxidation behavior of TMB2 nanopowders, which is a critical property for high-temperature applications.
HfB2 ceramics, as a member of TMB2 ceramics, have recently attracted extensive attentions because they exhibit potential applications in high-temperature electrodes and thermal protection systems for hypersonic aerospace vehicles [17–20]. In this work, we successfully synthesized the nanocrystalline HfB2 powders by the molten salt synthesis technique at a relatively low temperature of 1373 K using the inexpensive HfO2 and B powders as reaction precursors within the inexpensive KCl/NaCl molten salts. The effect of synthesis temperatures and molten salts on the phase compositions, morphology, and microstructure of the as-synthesized powders was investigated in detail, as well as the molten-salt assisted formation mechanism. The oxidation behavior of the as-synthesized powders was also investigated at different temperatures.
2 Experimental
The synthesis of HfB2 powders was conducted by the molten-salt assisted borothermal reduction based on the reaction between HfO2 powders (99.9% purity, average particle size: 1–3 μm, Shanghai Chaowei Nanotechnology Co., Ltd., Shanghai, China) and amorphous B powders (purity: 99.9%, average particle size < 3 μm, Shanghai Chaowei Nanotechnology Co., Ltd., Shanghai, China) with the presence of NaCl/KCl molten salts (molar ratio: 1:1, eutectic point: 931 K). The molar ratio was 3:10 for HfO2/B and 1:1 for NaCl/KCl, respectively. The weight ratio was 10:1 for NaCl/KCl and HfO2/B. Details of the synthesis of HfB2 powders were described as follows: The starting materials of HfO2, B, and NaCl/KCl were first mixed by hand for 30 min in an agate mortal using an agate pastel, and then the mixture of raw materials was put into an alumina crucible and placed into the horizontal alumina tube furnace. After evacuating the furnace for three times, argon carrier gas (purity: 99.99%) was introduced into the system with a flow rate of 300 sccm (standard-state cubic centimeter per minute). The system was heated from room temperature to 1273–1373 K at a rate of 10 K/min and held for 1 h, followed by furnace cooling to room temperature. Afterwards the as-synthesized products were taken out and immersed in the deionized water at 353 K to dissolve the residual NaCl/KCl salts, and B2O3 production. Finally, they were filtered and washed by the deionized water and the absolute ethanol for several times, and dried at 333 K. The products were also prepared by the similar borothermal reduction method without NaCl/KCl molten salts for comparison.
Thermogravimetric analysis (TGA) of the as-synthesized powders was performed using a Metter Toledo Star TGA/SDTA 851 thermal analyzer to investigate their isothermal oxidation behaviors at different temperatures. Before the isothermal oxidation tests, the surface area of the as-synthesized HfB2 powders was first measured to be about 3.5 m²·g-1 by Brunauer–emmett–teller Test method. Afterwards the samples were heated to the desired temperatures (773, 873, 973, and 1073 K) for the isothermal oxidation tests in air. The fast heating stage with a heating rate of 50 K/min prior to the isothermal period was applied to minimize oxidation effects before reaching the target temperatures in flowing nitrogen (purity: 99.99%) with a flow rate of 50 sccm. Finally, they were cooled naturally to room temperature in flowing nitrogen with a flow rate of 50 sccm. Weight changes of the as-synthesized powders related to the oxidation time were recorded with thermogravimetric mode.
The samples were analyzed by X-ray diffraction (XRD, X'pert PRO; PANalytical, Almelo, the Netherlands), scanning electron microscopy (SEM, Supra-55; Zeiss, Oberkochen, Germany), and transmission electron microscopy (TEM, Tecnai F30G2; FEI, Eindhoven, the Netherlands) equipped with energy dispersive spectroscopy (EDS).
3 Results and discussion
XRD patterns of the as-synthesized products at various conditions are shown in Fig. 1. Clearly, after incorporating molten salts, it can be seen that the products synthesized at 1273 K consist of a dominant HfB2 phase and a minor HfO2 impurity phase, as displayed in Fig. 1(a). However, when the synthesis temperature rises to 1373 K, the diffraction peaks of HfO2 impurity phase disappear and only the diffraction peaks of HfB2 phase can be detected in the as-synthesized products, as shown in Fig. 1(b). This indicates that HfB2 products can be successfully synthesized at 1373 K with molten salts. Before incorporating molten salts, the products synthesized at 1373 K are composed of HfB2 phase and HfO2 impurity phase, as presented in Fig. 1(c). Obviously, a high content of HfO2 impurity phase is present in the as-synthesized products. This suggests that HfB2 products cannot be synthesized at 1373 K without molten salts, which clearly demonstrates that the presence of molten salts induces the synthesis of HfB2 products.
Fig. 1 XRD patterns of the as-synthesized products at different conditions: (a) 1273 K with molten salts, (b) 1373 K with molten salts, and (c) 1373 K without molten salts.
SEM images of HfB2 products synthesized at 1373 K with molten salts are displayed in Fig. 2. From Fig. 2(a),it is evident that the as-synthesized products consist of a large amount of small particles. The high magnification SEM image shows that these small particles possess an irregular polyhedral morphology with the relatively uniform particle sizes, as shown in Fig. 2(b). In addition, SEM image can be examined to determine their particle sizes. A total of 100 individual particles were measured to get the average value of particle sizes and a Gaussian fitting to these data yields an average particle size of 155 nm (Fig. 2(c)). Therefore, the nanocrystalline HfB2 powders can be successfully synthesized at 1373 K with molten salts.
Fig. 2 SEM characterizations of HfB2 products synthesized at 1373 K with molten salts: (a) low magnification SEM image and (b) high magnification SEM image. (c) Histogram of each measured data for the particle sizes with a Gaussian fitting to the data. The Gaussian peak is centered at 155 nm.
Figure 3(a) shows a typical TEM image of HfB2 powders synthesized at 1373 K with molten salts, from which it can be clearly observed that the as-synthesized powders involve a large number of individual nanocrystalline particles. Clearly, their particle sizes can also be determined based on TEM images. A total of 50 individual particles were measured to get the average value of particle sizes. A Gaussian fitting to these data yields an average particle size of 155 nm, as shown in the inserted histogram in Fig. 3(a), which is in good agreement with the measured results from SEM images (Fig. 2(c)). Figure 3(b) shows a representative selected area electron diffraction (SAED) pattern along zone axis [111] of the as-synthesized powders. It clearly exhibits that the as-synthesized powders are the single crystal and hexagonal structure of HfB2 due to the well-arranged diffraction spots with the symmetry. The high-resolution transmission electron microscopy (HRTEM) image of the as-synthesized powders in Fig. 3(c) shows a periodic lattice structure and a set of fringes with the d-spaces of 0.272 nm, corresponding to the (110) plane of HfB2 (JCPSD Card No. 12-0234), which further confirms that the as-synthesized powders are single-crystalline hexagonal HfB2. In addition, an obvious amorphous B2O3 layer of ~4 nm can be seen on each particle surface (marked by dotted red lines in Fig. 3(c)), which could account for the presence of O element in EDS spectrum, as displayed in Fig. 4(d). The scanning transmission electron microscopy (STEM)–EDS analysis was further performed at an acceleration voltage of 200 kV and a collection time of 230 s. Besides O element, EDS spectrum also reveals that the as-synthesized powders contain Hf, B, and Cu elements. The presence of Hf and B elements verifies that the as-synthesized powders are composed of HfB2 phases. The detected Cu element should be attributed to the copper grids used to support TEM samples.
Fig. 3 TEM analysis of HfB2 products synthesized at 1373 K with molten salts: (a) TEM image, (b) SAED pattern, (c) HRTEM image, and (d) EDS spectrum.
On the basis of the aforementioned experiment results, it can be concluded that the presence of molten salts is crucial for the synthesis of the nanocrystalline HfB2 powders in our work. Similar conclusions have also been reported previously in other TMB2 ultrafine powders synthesized by the molten-salt assisted method, such as NbB2 [14], TiB2 [15], and CrB2 [16]. However, the molten-salt assisted formation mechanismis not well understood. To better understand this mechanism, we establish two simple schematic diagrams of formation mechanisms associated to the as-synthesized HfB2 powders without molten salts and with molten salts, as shown in Fig. 4.
Fig. 4 Schematic diagrams of formation mechanisms associated to the as-synthesized HfB2 powders: (a) without molten salts and (b) with molten salts.
In our case, the reaction precursors of the system involve HfO2 powders and amorphous B powders. NaCl/KCl is only used as molten salts. As a result, before incorporating molten salts, the synthesis of HfB2 powders is a traditional solid–solid reaction process, in which B reactant will first diffuse to the surface of HfO2 reactant and then it reacts with HfO2 to generate HfB2 product at synthesis temperatures, as displayed in Fig. 4(a). The reaction as well as the correlation between the standard Gibbs free energy (∆GθR,T ) of this reaction and the oxidation temperature (T) can be described as follows [21]:
where R is the gas constant. It is evident that the standard Gibbs free energy of Reaction (1) is so negative that this reaction can occur spontaneously at synthesis temperatures. After incorporating molten salts, the synthesis of HfB2 powders is a new molten-salt assisted liquid–solid reaction process, as presented in Fig. 4(b). In this process, the molten salts will be first melted into isotropic liquid at elevated temperatures, and then the B and HfO2 reactants are rapidly dissolved into the molten salts. This finally leads to the uniformly distributions of B and HfO2 in the molten salts. Afterwards HfB2 product is generated by Reaction (1) between the B and HfO2 reactants at synthesis temperatures by Eq. (1). With the reaction continuing, the dissolved reactants are constantly consumed, but at the same time the undissolved reactants are continuously dissolved into molten salts to participate in the reaction until the end. In general, the total reaction rate (V) of the system depends on the diffusion rate (VD) of the reactants and the chemical reaction rate (VR) of the reactants, which can be calculated by the following equations [22]:
where Q is the diffusion activation energy, D0 is the constant of coefficient of diffusion, C0 is the reactant concentration at the beginning of diffusion, C is the reactant concentration at the end of diffusion, δ is the diffusion distance, K is the chemical reaction constant, CHfO2 and CB are the HfO2 and B concentrations, respectively. From Eq. (3), it can be found that the diffusion rate of the reactants is closely related to the diffusion distance and the diffusion activation energy. Before incorporating molten salts, there is a long diffusion distance in the reactants due to their agglomerations, as shown in Fig. 4(a). After incorporating molten salts, the B and HfO2 reactants are uniformly dispersed into the molten salts, and thereby a short diffusion distance is presented in the reactants, as displayed in Fig. 4(b). In addition, as a rule, the diffusion activation energy of the reactants in the liquid phase is much less than that in the solid phase. As a consequence, both the short diffusion distance and the reduced diffusion activation
energy result in the presence of a large diffusion rate in the molten-salt assisted synthesis process. From Eq. (4), we can see that the chemical reaction rate of the reactants is mainly determined by the HfO2 and B concentrations. In general, B reactant is very easy to be volatilized at elevated temperatures. However, the degree of B evaporation in liquid phase is less than that in solid phase. Consequently, B reactant possesses a high concentration in the molten-salt assisted synthesis process, which could significantly enhance the chemical reaction rate of the reactants. In brief, the presence of molten salts not only accelerates the diffusion rate of the reactants by shortening their diffusion distances and decreasing their diffusion activation energies, but also enhances the chemical reaction rate by reducing the evaporation of B. Owing to the high diffusion rate
and chemical reaction rate, according to Eq. (2), it can be clearly observed that the total reaction rate of the system will be high in the molten-salt assisted synthesis process, which finally results in the synthesis of the nanocrystalline HfB2 powders.
To investigate the isothermal oxidation behavior of the as-synthesized HfB2 powders at different temperatures, the TGA test was conducted and the results are shown in Fig. 5.
Fig. 5 Oxidation analysis of the as-synthesized HfB2 powders by TGA tests at different temperatures: (a) weight change per unit area (∆w/A, ∆w is the weight change and A is the surface area of samples) as a function of oxidation time (t) at 773 and 873 K; (b) square of the weight change per unit surface area as a function of oxidation time at 773 and 873 K; (c) weight change per unit area as a function of oxidation time at 973 and 1073 K; (d) square of the weight change per unit surface area as a function of oxidation time at 973 K; (e) weight change per unit area as a function of oxidation time at 1073 K after 30 min; (f) weight change per unit area as a function of oxidation time at 1073 K before 30 min with fitted parabolic and line curves; (g) square of the weight change per unit surface area corresponding to the fitted parabolic curve in (f); (h) plot of logarithm parabolic rate kp (parabolic rate constant) versus reciprocal of the temperatures.
From Fig. 5(a), it can be seen that the oxidation of the samples at 773 and 873 K exhibits the weight gain process. However, the oxidation rate of the samples at 873 K is much higher than that of the samples at 773 K. After isothermal oxidation for 120 min in air, the weight gain of the samples at 773 K is only 0.034 mg/cm², while the weight gain of the samples at 873 K is up to 0.116 mg/cm². Figure 5(b) depicts the plots of the square of the specific weight change as a function of oxidation time for the samples at 773 and 873 K. Clearly, there is a good linear relationship (R² > 0.99) between the square of the specific weight change and oxidation time, which indicates that the oxidation behavior of the samples at 773 and 873 K follows the parabolic kinetics. That is to say, the oxidation of the samples at 773 and 873 K is governed by a diffusion process that oxygen diffused into the oxide layer generated in the reaction between HfB2 and O2 by the following equation [23,24]:
As the oxidation temperature rises to 973 K, the oxidation of the samples is still a weight gain process and their oxidation behavior also follows a parabolic kinetics (Figs. 5(c) and 5(d)). However, the weight gain of the samples is up to 0.8 mg/cm2 after isothermal oxidation for 120 min in air, much larger than that of the samples at 873 K, suggesting that the oxidation rate of the samples at 973 K is quite high. When the oxidation temperature increases to 1073 K, the oxidation of the samples is a complicated weight gain process, as displayed in Fig. 5(c), which can be divided into two stages, marked as A and B, respectively. During the stage A (0–30 min), the oxidation of the samples exhibits a rapid weight gain and the final weight gain is up to 0.82 mg/cm2 after isothermal oxidation for 30 min in air. As the oxidation time is over 30 min (stage B), the oxidation of the samples is still a weight gain process, but the weight gain rate is negative. Hence, the final weight gain decreases to 0.6 mg/cm² after isothermal oxidation for 120 min in air. In addition, From Eq. (5), it can be found that the oxidation of the samples is a weight gain process. Therefore, it can be concluded that the samples have been completely oxidized after isothermal oxidation for 30 min at 1073 K in air. After isothermal oxidation for 30 min, the weight gain of the samples is a linear decrease process (Fig. 5(f)), which should be associated to the evaporation of B2O3. On the basis of this linear relationship, a constant evaporation rate of B2O3 can be calculated to be ~0.026 mg/(cm²∙min-1). Before isothermal oxidation for 30 min, it should be noted that the oxidation behavior of the samples deviates from the parabolic kinetics, as shown in Fig. 5(e). Therefore, a simple parabolic law is unable to describe the oxidation kinetic behavior. However, the TGA curve can be fitted into a linear term and a parabolic term based on a multiple-law model, according to the following equation [25]:
where kl is the linear rate constant. The results are depicted in Fig. 5(e). Obviously, the dominating term is still a parabolic curve (green dotted line), which suggests that the oxidation behavior of the samples is still a parabolic kinetics before isothermal oxidation for 30 min at 1073 K in air. This can be further confirmed by the presence of a good linear relationship between the square of the specific weight change and oxidation time, as depicted in Fig. 5(g). The rest term is a linear curve (blue dotted line) and it is negative, which is associated with the evaporation of B2O3. This is because that the slop of the line can be calculated to be ~0.025 mg/(cm²∙min-1), which is consistent with the vaporization rate of B2O3 (0.026 mg/(cm²∙min-1)) after isothermal oxidation for 30 min. In sum, the oxidation behavior of the samples follows the parabolic kinetics at 773–1073 K, which is governed by the diffusion of oxygen in the oxide layer. As a result, kp at various oxidation temperatures can be calculated by the following equation [26]:
The calculated results are listed in Table 1. On the basis of these results, for the oxygen diffusion mode, the oxidation activation energy (∆E) of the samples can be also calculated by the following equation [27]:
where A0 is the constant of preexponential factor. Figure 5(h) plots the In(kp) as a function of reciprocal temperatures, and thereby the oxidation activation energy can be calculated to be ~190.8 kJ/mol.
Table 1 Calculated kp with corresponding R² (fit goodness) for various oxidation temperatures
Figure 6 shows that XRD patterns of the as-synthesized HfB2 powders after isothermal oxidation tests at various temperatures. After isothermal oxidation tests at 773 and 873 K, the as-synthesized HfB2 powders are mainly composed of a dominant HfB2 phase and a minor HfO2 phase, as displayed in Fig. 6(a), which suggests that only a small number of HfB2 powders are oxidized at 773 and 873 K. As the oxidation temperature rises to 973 K, the as-synthesized HfB2 powders mainly consist of a dominant HfO2 phase and a minor HfB2 phase, indicating that most of HfB2 powders have been oxidized at 973 K. When the oxidation temperature increases to 1073 K, the diffraction peaks of HfB2 phase have completely disappeared in the XRD pattern and all the relatively sharp diffraction peaks in the XRD pattern can be indexed to HfO2 phase. These imply that HfB2 powders have been completely oxidized at 1073 K. What's more, the amorphous B2O3 can also be detected by XRD, as depicted in Fig. 6(b). A weak diffraction peak near a 2θ value of 28° from the {310} lattice plane of the amorphous B2O3 product can be observed at 773 and 873 K, while its intensity becomes very remarkable when the oxidation temperatures rise to 973 and 1073 K. This further confirms that only a small number of HfB2 powders are oxidized at 773 and 873 K, while most or all of HfB2 powders have been oxidized at 973 and 1073 K.
Fig. 6 XRD analysis of the as-synthesized HfB2 powders after oxidation tests: (a) XRD patterns of the as-synthesized HfB2 powders after oxidation tests at various temperatures;(b) high magnification of XRD patterns with 2θ from 10° to 40°.
Figure 7 shows that the SEM images of the as-synthesized HfB2 powders after isothermal oxidation tests at various temperatures. After isothermal oxidation tests at 773 and 873 K, the powders mainly consist of the irregularly HfB2 particles, on which some amorphous B2O3 glass and HfO2 nanoparticles can be found, as shown in Figs. 7(a) and 7(b). This suggests that the powders are only oxidized slightly at 773 and 873 K. As the oxidation temperature rises to 973 K, the powders are mainly composed of numerous HfO2 nanoparticles and amorphous B2O3 glass, and only a few irregularly HfB2 particles can be observed, indicating that most of HfB2 powders have been oxidized at 973 K. When the oxidation temperature increases to 1073 K, the powders involve numerous HfO2 nanoparticles, nanorods, and amorphous B2O3 glass phase can be found, which implies that all of HfB2 powders have been completely oxidized at 973 K.
Fig. 7 SEM images of the as-synthesized HfB2 powders after oxidation tests at various temperatures in air: (a) 773, (b) 873, (c) 973, and (d) 1073 K.
In summary, the nanocrystalline HfB2 powders had been successfully synthesized via a simple molten salt synthesis technique. The as-synthesized HfB2 powders possessed an irregular polyhedral morphology with the average particle sizes of ~155 nm. In addition, they also exhibited a single-crystalline structural feature. More importantly, from a fundamental aspect, we demonstrated why the presence of molten salts could induce the synthesis of nanocrystalline HfB2 powders. The oxidation results show that the oxidation of as-synthesized HfB2 powders at 773–1073 K in air is the weight gain process and the corresponding oxidation behavior follows parabolic kinetics that is governed by the diffusion of oxygen in the oxide layer. This work not only may provide a new method for the synthesis of HfB2 powders and a theoretical guidance for the molten salt synthesis method, but also reveal the oxidation behaviors of the nanocrystalline HfB2 powders at low temperatures in air.
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Consciousness and Psychology in Philosophy of Cognitive Science
Description and Experience: How Experimental Investors Learn About Booms and Busts Affects Their Financial Risk Taking.Tomás Lejarraga, Jan K. Woike & Ralph Hertwig - 2016 - Cognition 157:365-383.details
Cognition and Emotion, Volume 24, 2010, List of Contents.Dirk Hermans, Jan De Houwer, Jenny Yiend, Nilly Mor, Leah D. Doane, Emma K. Adam, Susan Mineka, Richard E. Zinbarg, James W. Griffith & Michelle G. Craske - 2010 - Cognition and Emotion 24 (8).details
Emotion and Consciousness in Psychology in Philosophy of Cognitive Science
Jan Patočka: od filosofie přirozeného světa k filosofii dějin.Paul Ricoeur - 1997 - Filosoficky Casopis 45:742-749.details
[Jan Patočka: From a Philosophy of the Natural World to a Philosophy of History.].
Incorporating Measurement Error in N = 1 Psychological Autoregressive Modeling.Noémi K. Schuurman, Jan H. Houtveen & Ellen L. Hamaker - 2015 - Frontiers in Psychology 6.details
Ma-K o-Ssu Po Shih Lun Wen Te-Mo-K o-Li-T E Ti Tzu Jan Che Hsüeh Yü I-Pi-Chiu-Lu Ti Tzu Jan Che Hsüeh Ti Ch a Pieh.Karl Marx, Georg Mende & Ernst Günther Schmidt - 1961 - Jen Min Ch U Pan She Hsin Hua Shu Tien Fa Hsing.details
Review: Jan Sykora, The Concept of Power in Mathematics. [REVIEW]K. Reach - 1939 - Journal of Symbolic Logic 4 (4):166-166.details
Intuitionistic Logic in Logic and Philosophy of Logic
Sýkora Jan. Pojem Potence V Matematice . Filosofická Revue, Vol. 10 , Pp. 19–23.K. Reach - 1939 - Journal of Symbolic Logic 4 (4):166-166.details
Les "Siao-Hal-Yu" de Pékin; Un Essai Sur la Poésie Populaire En ChineLes "Siao-Hal-Yu" de Pekin; Un Essai Sur la Poesie Populaire En Chine.J. K. Shryock, Witold Jabloński & Witold Jablonski - 1936 - Journal of the American Oriental Society 56 (3):375.details
Jan Paweł II jako autorytet wychowawczy. Autorytet i jego miejsce we współczesnej kulturze,".K. Olbrycht - 1997 - Ethos: Journal of the Society for Psychological Anthropology 37:101-110.details
Review: Jan Lukasiewicz, Comment on K. J. Cohen's Remark. [REVIEW]Gene F. Rose - 1954 - Journal of Symbolic Logic 19 (3):217-217.details
Logic and Philosophy of Logic, Miscellaneous in Logic and Philosophy of Logic
Logics in Logic and Philosophy of Logic
Nonclassical Logics in Logic and Philosophy of Logic
Łukasiewicz Jan. Comment on K. J. Cohen's Remark. Koninklijke Nederlandse Akademie van Wetenschappen, Proceedings, Series A, Vol. 56 , P. 113; Also Indagationes Mathematicae, P. 113. [REVIEW]Gene F. Rose - 1954 - Journal of Symbolic Logic 19 (3):217-217.details
Jan Bransen, Word zelf filosoof, Veen Magazines, 2010 [Book Review].K. Schaubroeck - forthcoming - Algemeen Nederlands Tijdschrift voor Wijsbegeerte.details
Jan M. Ziolkowski and Bridget K. Balint, Eds., with, Justin Lake, Laura Light, and Prydwyn Piper, A Garland of Satire, Wisdom, and History: Latin Verse From Twelfth-Century France . Cambridge, Mass.: Houghton Library of the Harvard College Library, 2007. Paper. Pp. X, 232; 1 Black-and-White Figure, Many Color Facsimiles, and 1 Map. Distributed by Harvard University Press. [REVIEW]Martha Bayless - 2010 - Speculum 85 (2):486-487.details
Mcgarigal, K., S. Cusham and S. Stafford (2000). Multivariate Statistics for Wildlife and Ecology Research.Jan Bogaert - 2001 - Acta Biotheoretica 49 (2):141-143.details
Ecology and Conservation Biology, Misc in Philosophy of Biology
K Problematike Výskumu Vedy O Vede V Ndr.Jan Letaši - 1979 - Filozofia 34 (1):63.details
Jan Öberg : Two Millennia of Poetry in Latin: An Anthology of Works of Cultural and Historic Interest, Vol. 1: The Late Classical Period and the Early Middle Ages. Pp. 284; 23 Illustrations, 15 in Colour. London: Carmina U.K. Ltd., 1987. £28.50. [REVIEW]A. B. E. Hood - 1990 - The Classical Review 40 (1):160-160.details
Poetry in Aesthetics
Jan Öberg (Ed.): Two Millennia of Poetry in Latin: An Anthology of Works of Cultural and Historic Interest, Vol. 1: The Late Classical Period and the Early Middle Ages. Pp. 284; 23 Illustrations, 15 in Colour. London: Carmina U.K. Ltd., 1987. £28.50. [REVIEW]A. B. E. Hood - 1990 - The Classical Review 40 (01):160-.details
Studie k pojmu světa.Jan Patocka - 2011 - Reflexe: Filosoficky Casopis 40:75-97.details
Vom Erscheinen als solchem.Jan Patočka, Helga Blaschek-Hahn & K. Novotný - 2001 - Tijdschrift Voor Filosofie 63 (3):632-632.details
K Humově filosofii náboženství.Ján Pavlík - 2011 - E-Logos 18 (1):1-38.details
Jan Čížek, Komenský a Bacon: Dvě Raně Novověké Cesty K Obnově Vědění, Pavel Mervart, Červený Kostelec, 2017, 214 S.Daniel Špelda - 2018 - Pro-Fil 19 (1):62.details
Grammatica speculativa. Sprachtheorie und Logik des Mittelalters. Band I: Sophismata. Band II: Tractatus de suppositionibus. [REVIEW]Jan Pinborg, Helmut Kohlenberg, Johannes Buridanus, T. K. Scott, Vincent Ferrer & John A. Trentman - 1979 - Tijdschrift Voor Filosofie 41 (1):141-142.details
Aerobic Exercise Induces Functional and Structural Reorganization of CNS Networks in Multiple Sclerosis: A Randomized Controlled Trial.Jan-Patrick Stellmann, Adil Maarouf, Karl-Heinz Schulz, Lisa Baquet, Jana Pöttgen, Stefan Patra, Iris-Katharina Penner, Susanne Gellißen, Gesche Ketels, Pierre Besson, Jean-Philippe Ranjeva, Maxime Guye, Guido Nolte, Andreas K. Engel, Bertrand Audoin, Christoph Heesen & Stefan M. Gold - 2020 - Frontiers in Human Neuroscience 14.details
Philosophy of Neuroscience in Philosophy of Cognitive Science
Bernstein Sets and K -Coverings.Jan Kraszewski, Robert Rałowski, Przemysław Szczepaniak & Szymon Żeberski - 2010 - Mathematical Logic Quarterly 56 (2):216-224.details
In this paper we study a notion of a κ -covering set in connection with Bernstein sets and other types of non-measurability. Our results correspond to those obtained by Muthuvel in [7] and Nowik in [8]. We consider also other types of coverings.
American Pragmatism in Philosophy of the Americas
Promoting Coherent Minimum Reporting Guidelines for Biological and Biomedical Investigations: The MIBBI Project.Chris F. Taylor, Dawn Field, Susanna-Assunta Sansone, Jan Aerts, Rolf Apweiler, Michael Ashburner, Catherine A. Ball, Pierre-Alain Binz, Molly Bogue, Tim Booth, Alvis Brazma, Ryan R. Brinkman, Adam Michael Clark, Eric W. Deutsch, Oliver Fiehn, Jennifer Fostel, Peter Ghazal, Frank Gibson, Tanya Gray, Graeme Grimes, John M. Hancock, Nigel W. Hardy, Henning Hermjakob, Randall K. Julian, Matthew Kane, Carsten Kettner, Christopher Kinsinger, Eugene Kolker, Martin Kuiper, Nicolas Le Novere, Jim Leebens-Mack, Suzanna E. Lewis, Phillip Lord, Ann-Marie Mallon, Nishanth Marthandan, Hiroshi Masuya, Ruth McNally, Alexander Mehrle, Norman Morrison, Sandra Orchard, John Quackenbush, James M. Reecy, Donald G. Robertson, Philippe Rocca-Serra, Henry Rodriguez, Heiko Rosenfelder, Javier Santoyo-Lopez, Richard H. Scheuermann, Daniel Schober, Barry Smith & Jason Snape - 2008 - Nature Biotechnology 26 (8):889-896.details
Throughout the biological and biomedical sciences there is a growing need for, prescriptive 'minimum information' (MI) checklists specifying the key information to include when reporting experimental results are beginning to find favor with experimentalists, analysts, publishers and funders alike. Such checklists aim to ensure that methods, data, analyses and results are described to a level sufficient to support the unambiguous interpretation, sophisticated search, reanalysis and experimental corroboration and reuse of data sets, facilitating the extraction of maximum value from data sets (...) them. However, such 'minimum information' MI checklists are usually developed independently by groups working within representatives of particular biologically- or technologically-delineated domains. Consequently, an overview of the full range of checklists can be difficult to establish without intensive searching, and even tracking thetheir individual evolution of single checklists may be a non-trivial exercise. Checklists are also inevitably partially redundant when measured one against another, and where they overlap is far from straightforward. Furthermore, conflicts in scope and arbitrary decisions on wording and sub-structuring make integration difficult. This presents inhibit their use in combination. Overall, these issues present significant difficulties for the users of checklists, especially those in areas such as systems biology, who routinely combine information from multiple biological domains and technology platforms. To address all of the above, we present MIBBI (Minimum Information for Biological and Biomedical Investigations); a web-based communal resource for such checklists, designed to act as a 'one-stop shop' for those exploring the range of extant checklist projects, and to foster collaborative, integrative development and ultimately promote gradual integration of checklists. (shrink)
Biological Information in Philosophy of Biology
Databases in Philosophy of Computing and Information
Experimentation in Science in General Philosophy of Science
Ontology in Metaphysics
Philosophy of Biology, Misc in Philosophy of Biology
Scientific Method, Miscellaneous in General Philosophy of Science
Putting Your Money Where Your Self Is: Connecting Dimensions of Closeness and Theories of Personal Identity.Jan K. Woike, Philip Collard & Bruce Hood - 2020 - PLoS ONE 15 (2):1-44.details
Studying personal identity, the continuity and sameness of persons across lifetimes, is notoriously difficult and competing conceptualizations exist within philosophy and psychology. Personal reidentification, linking persons between points in time is a fundamental step in allocating merit and blame and assigning rights and privileges. Based on Nozick's closest continuer theory we develop a theoretical framework that explicitly invites a meaningful empirical approach and offers a constructive, integrative solution to current disputes about appropriate experiments. Following Nozick, reidentification involves judging continuers on (...) a metric of continuity and choosing the continuer with the highest acceptable value on this metric. We explore both the metric and its implications for personal identity. Since James, academic theories have variously attributed personal identity to the continuity of memories, psychology, bodies, social networks, and possessions. In our experiments, we measure how participants weighted the relative contributions of these five dimensions in hypothetical fission accidents, in which a person was split into two continuers. Participants allocated compensation money or adjudicated inheritance claims and reidentified the original person. Most decided based on the continuity of memory, personality, and psychology, with some consideration given to the body and social relations. Importantly, many participants identified the original with both continuers simultaneously, violating the transitivity of identity relations. We discuss the findings and their relevance for philosophy and psychology and place our approach within the current theoretical and empirical landscape. (shrink)
Experimental Philosophy: Persons in Metaphilosophy
Upon Repeated Reflection: Consequences of Frequent Exposure to the Cognitive Reflection Test for Mechanical Turk Participants.Jan K. Woike - 2019 - Frontiers in Psychology 10.details
Editorial: Olympische Spiele – (k)ein Schwerpunkt?Jan Haut - 2021 - Sport Und Gesellschaft 18 (1):1-8.details
Filozofický Pristúp K Vedeckému Riadeniu Spoločnosti.Ján Dubnická - 1985 - Filozofia 40 (1):115.details
Jan Mukařovský's Concept of the Work of Art as Sign.David K. Danow - 1986 - Semiotics:140-148.details
REVIEWS-K. Godel Collected Works IV-V.S. Feferman & Jan von Plato - 2004 - Bulletin of Symbolic Logic 10 (4):558-562.details
British Philosophy in European Philosophy
Religious Attitudes Towards Living Kidney Donation Among Dutch Renal Patients.Sohal Y. Ismail, Emma K. Massey, Annemarie E. Luchtenburg, Lily Claassens, Willij C. Zuidema, Jan J. V. Busschbach & Willem Weimar - 2012 - Medicine, Health Care and Philosophy 15 (2):221-227.details
Terminal kidney patients are faced with lower quality of life, restricted diets and higher morbidity and mortality rates while waiting for deceased donor kidney transplantation. Fortunately, living kidney donation has proven to be a better treatment alternative (e.g. in terms of waiting time and graft survival rates). We observed an inequality in the number of living kidney transplantations performed between the non-European and the European patients in our center. Such inequality has been also observed elsewhere in this field and it (...) has been suggested that this inequality relates to, among other things, attitude differences towards donation based on religious beliefs. In this qualitative research we investigated whether religion might indeed (partly) be the explanation of the inequalities in living donor kidney transplants (LDKT) among non-European patients. Fifty patients participated in focus group discussions and in-depth interviews. The interviews were conducted following the focus group method and analyzed in line with Grounded Theory. The qualitative data analyses were performed in Atlas.ti. We found that religion is not perceived as an obstacle to living donation and that religion actually promotes helping and saving the life of a person. Issues such as integrity of the body were not seen as barriers to LDKT. We observed also that there are still uncertainties and a lack of awareness about the position of religion regarding living organ donation within communities, confusion due to varying interpretations of Holy Scriptures and misconceptions regarding the process of donation. Faith leaders play an important educational role and their opinion is influential. This study has identified modifiable factors which may contribute to the ethnic disparity in our living donation program. We argue that we need to strive for more clarity and awareness regarding the stance of religion on the issue of living donation in the local community. Faith leaders could be key figures in increasing awareness and alleviating uncertainty regarding living donation and transplantation. (shrink)
Biomedical Ethics in Applied Ethics
Medical Ethics in Applied Ethics
Fear Expression and Return of Fear Following Threat Instruction with or Without Direct Contingency Experience.Gaëtan Mertens, Manuel Kuhn, An K. Raes, Raffael Kalisch, Jan De Houwer & Tina B. Lonsdorf - 2016 - Cognition and Emotion 30 (5).details
Sobociński Bolesław. In memoriam Jan Łukasiewicz. Englisch. Philosophical studies , Bd. 6 , S. 3–49.Scholz Heinrich. In memoriam Jan Łukasiewicz. Deutsch. Archiv für mathematische Logik und Grundlagenforschung, Bd. 3 Heft 1–2 , S. 1–18. [REVIEW]K. Dürr - 1957 - Journal of Symbolic Logic 22 (4):385-387.details
Emotional Language Processing in Autism Spectrum Disorders: A Systematic Review.Alina Lartseva, Ton Dijkstra & Jan K. Buitelaar - 2014 - Frontiers in Human Neuroscience 8.details
Neuroethics in Applied Ethics
Livestream Experiments: The Role of COVID-19, Agency, Presence, and Social Context in Facilitating Social Connectedness.Kelsey E. Onderdijk, Dana Swarbrick, Bavo Van Kerrebroeck, Maximillian Mantei, Jonna K. Vuoskoski, Pieter-Jan Maes & Marc Leman - 2021 - Frontiers in Psychology 12.details
Musical life became disrupted in 2020 due to the COVID-19 pandemic. Many musicians and venues turned to online alternatives, such as livestreaming. In this study, three livestreamed concerts were organized to examine separate, yet interconnected concepts—agency, presence, and social context—to ascertain which components of livestreamed concerts facilitate social connectedness. Hierarchical Bayesian modeling was conducted on 83 complete responses to examine the effects of the manipulations on feelings of social connectedness with the artist and the audience. Results showed that in concert (...) 1, where half of the participants were allowed to vote for the final song to be played, this option did not result in the experience of more agency. Instead, if their preferred song was played participants experienced greater connectedness to the artist. In concert 2, participants who attended the concert with virtual reality headsets experienced greater feelings of physical presence, as well as greater feelings of connectedness with the artist, than those that viewed a normal YouTube livestream. In concert 3, attendance through Zoom led to greater experience of social presence, but predicted less connectedness with the artist, compared to a normal YouTube livestream. Crucially, a greater negative impact of COVID-19 predicted feelings of connectedness with the artist, possibly because participants fulfilled their social needs with this parasocial interaction. Examining data from all concerts suggested that physical presence was a predictor of connectedness with both the artist and the audience, while social presence only predicted connectedness with the audience. Correlational analyses revealed that reductions in loneliness and isolation were associated with feelings of shared agency, physical and social presence, and connectedness to the audience. Overall, the findings suggest that in order to reduce feelings of loneliness and increase connectedness, concert organizers and musicians could tune elements of their livestreams to facilitate feelings of physical and social presence. (shrink)
In Memorian Jan Łukasiewicz.K. Dürr - 1957 - Journal of Symbolic Logic 22 (4):385-387.details
Dynamika ľudského prístupu K svetu V diele Jana patočku.Jan Patočka - 2012 - Filozofia 67 (5):398.details
Edmund Husserl in Continental Philosophy
K. Gödel Collected Works Iv—V. [REVIEW]Jan von Plato - 2004 - Bulletin of Symbolic Logic 10 (4):558-562.details
Zich O. V.. Příspěvek K Theorii Celých Čísel a Jednojednoznačného Zobrazení . Rozpravy II, Třídy České Akademie, Vol. 58 No. 11 , 12 Pp. [REVIEW]Jan Kalicki - 1951 - Journal of Symbolic Logic 16 (1):71-72.details
Symposium on Spirituality in Business.Judith K. Thompson, Martin Rutte, Maya Sutton, Tom E. Thomas & Jan Willem Bol - 1996 - Proceedings of the International Association for Business and Society 7:269-270.details
Business Ethics in Applied Ethics
Dispute Over Logistic Between Jan Łukasiewicz and Augustyn Jakubisiak. Why Was It Important?Bartłomiej K. Krzych - 2019 - Studia Humana 8 (2):16-24.details
Augustyn Jakubisiak, Polish priest, philosopher and theologian, undertook polemics with Jan Łukasiewicz, whom he knew personally. A dispute concerning the so-called logistics and its relationship with philosophy developed between the two. The most important arguments were laid out, primarily in the following works: in the case of Jakubisiak, in the book From Scope to Content and in the case of Łukasiewicz, in the texts Logistics and Philosophy and In the Defense of Logistics. Jakubisiak criticized logistics for its anti-metaphysical, anti-theological and (...) anti-religious attitude, which was based on neo-positivist philosophy, and led, in consequence to atheism. He also claimed that one should focus on what is concrete, avoiding idealization and abstraction. Łukasiewicz defended logistics claiming that it possesses its own methods based on intellect, and is also an area of independent knowledge from philosophy, due to the fact it can consider the most important philosophical problems such as finiteness and infinity. This dispute, as the researchers identified, basically concerned the reduction of philosophy to the study of language and initiated one of the most important discussions concerning the relationship between philosophy and logic. This debate was crucial because it also concerned questions related to fundamental metaphysical issues and epistemological issues. (shrink)


https://www.nationalgeographic.com/travel/destinations/north-america/united-states/tennessee/road-trip-drive-through-tennessee.html
The Ultimate Tennessee Road Trip
This 400-mile road trip will take you from the Great Smoky Mountains to the Mississippi River, and all that is in between.
By Maryellen Kennedy Duckett
Aerial footage of the Smoky Mountains in Tennessee.
Video by Smithsonian, Getty Images
Cruise east to west across the Volunteer State to experience some of Tennessee's top tastes, sights, sounds, and state parks. The roughly 420-mile route follows I-40 from the Great Smoky Mountains in the east to the mighty Mississippi River in the west. If you're planning a fly-and-drive vacation, arrive in Knoxville and depart from Memphis.
Whether you start the trip on I-40 or at the Knoxville airport, it's a short drive (about 30 miles) to Great Smoky Mountains National Park. From the interstate (exit 407, Sevierville), head to the Sugarlands Visitor Center in Gatlinburg for a free park map, trail recommendations, and a schedule of ranger-led programs.
Fog rolls across lush green meadows in Cades Cove.
Photograph by Bill Swindaman, Getty Images
From the airport, the closest park entrance is in Townsend, gateway to historic Cades Cove and its 11-mile, one-way scenic driving loop. For 360-degree views of the park, hike the paved half-mile trail to the summit observation tower atop 6,643-foot Clingmans Dome, the highest point in the park—and in the state.
Eat and Stay: Blue Mountain Mist Country Inn & Spa and Applewood Farmhouse Restaurant, Sevierville
The Sunsphere glistens alongside city lights in Knoxville.
Video by Bryan and Wendy Mullennix, Getty Images
From Sevierville, hop on I-40 for the 30-minute ride west to downtown Knoxville (exit 388, Henley Street). The state's third-largest city draws outdoor enthusiasts to its Urban Wilderness and live music acts to intimate venues such as the Mill & Mine and the historic Tennessee Theatre. Visit the Outdoor Knoxville Adventure Center at Volunteer Landing for trail maps and seasonal bike, canoe, and stand-up paddleboard rentals. Nearby, tour the Women's Basketball Hall of Fame, topped by the world's largest (30 feet tall) basketball.
At noon daily (except Sunday), catch the free WDVX Blue Plate Special live performance radio show inside the Knoxville Visitor Center. On Wednesdays and Saturdays (May to November) visit the Market Square Farmers Market.
Eat and Stay: Sweet P's Downtown Dive and The Tennessean
Oak Ridge and Crossville
Detour off I-40 at exit 376A (Pellissippi Parkway) to discover the "Secret City" of Oak Ridge. Constructed in 1943 to house facilities and workers helping build the world's first atomic bomb, Oak Ridge (along with Los Alamos, New Mexico, and Hanford, Washington) hosts a section of the Manhattan Project National Historical Park. Park tours begin at the American Museum of Science & Energy.
From Oak Ridge, follow TN-95 South back to I-40 (exit 364). Continue west onto the Cumberland Plateau, crossing into the Central Time Zone at mile marker 340. Stop at the family-owned Stonehaus Winery (exit 320, Crossville) for a complimentary wine tasting.
Eat and Stay: Big Ed's Pizza, Oak Ridge, and Wyndham Resort at Fairfield Glade, Crossville
Cookeville and Buffalo Valley
Water rushes down Burgess Falls in its namesake's state park.
Photograph by Don Grall, Getty Images
The 35-mile drive from Crossville (elevation 1,854 feet) to Cookeville (elevation 1,140 feet) is one of the highest stretches of I-40 between Knoxville and Memphis. Take exit 290 (Cookeville) to learn about the region's railway history at the Cookeville Depot Museum (closed Sunday and Monday). Walk across the street for a cone or cup at Cream City Ice Cream & Coffee.
At Burgess Falls State Park (exit 286), peer down from the rim (trails to the base of the falls are closed) at the main waterfall plunging into the gorge. Buffalo Valley (exit 268) is the I-40 gateway to Edgar Evins State Park and Center Hill Lake. To play on the lake, rent a houseboat, Jet Ski, or pontoon boat at Edgar Evins Marina.
Eat and Stay: Father Tom's Pub, Cookeville, and Evins Mill, Smithville
The city lights of Nashville turn on as the sun sets behind the skyline.
Photograph by Malcolm MacGregor, Getty Images
Spend at least two full days and one music-filled night in Nashville (exit 209A, Broadway), Tennessee's capital and home of the Grand Ole Opry. Get steeped in Music City history at the world-class Country Music Hall of Fame and Museum. Nearby, stroll Lower Broadway to visit the city's famous honky-tonk bars and shop for cowboy boots (buy a pair, get two pairs free) at Boot Country Nashville.
In the Southern-hip 12South neighborhood, browse the curated collections at actor Reese Witherspoon's flagship Draper James store and songwriter Holly William's White's Mercantile. After shopping, indulge in a sweet treat from the Sprinkles Cupcakes ATM or at Five Daughters Bakery, home of the 100 Layer Donut. If the Nashville Sounds are in town, catch a Triple-A baseball game (and the game-long party at The Band Box in right field) in historic Germantown neighborhood.
Eat and Stay: Monell's Germantown and The Hermitage Hotel
Burns, Hurricane Mills, and Camden
Montgomery Bell State Park in bucolic Burns (exit 182, Fairview) is a 40-minute drive west—and a world away—from the bright lights of Nashville. Spend the morning in the park hiking; canoeing, kayaking, or boating (seasonal rentals available) on one of its three lakes; or golfing the par-71, 18-hole course.
Continue west to Hurricane Mills (exit 143, Linden/Waverly) and Loretta Lynn's Ranch, the former home-turned-museum of the country music icon. On a self-guided tour, visit Lynn's grand plantation-style home and the memorabilia-packed Coal Miner's Daughter Museum. In Camden (exit 133), see how freshwater pearls are cultured and harvested at the Tennessee River Freshwater Pearl Farm and Museum.
Eat and Stay: Log Cabin Restaurant, Hurricane Mills, and Birdsong Resort and Marina, Camden
Wildersville and Jackson
From Camden, it's only 26 miles southwest to Natchez Trace State Park (exit 116, Wildersville). Home to four lakes and an equestrian center, the 9,629-acre park boasts top-notch bass fishing and over 250 miles of public use trails open to horseback riders. Memorial Day to Labor Day, rent a flat-bottomed boat to fish (licenses are sold at the Inn on Pin Oak Lake) for bass, bluegill, and catfish. Walk through woodlands and along the waterways on more than 20 miles of hiking trails.
Continue west to Casey Jones Village (exit 80A, Jackson), a one-stop destination for shopping, Southern eats, and family attractions, including mini-golf and the Casey Jones Home & Railroad Museum.
Eat and Stay: The Old Country Store, Jackson, and Peaceful Oaks Bed Breakfast and Barn, Medina
Roll west 85 miles into Memphis and the Tennessee Delta for the grand finale of your mountains-to-the-Mississippi adventure. Memphis is legendary for Delta blues and barbecue, but there's so much more here to explore.
A red Ford Thunderbird is parked outside of the Sun Studio in Memphis, Tennessee.
Photograph by Andrew Woodley, Alamy Stock Photo
Start by touring the National Civil Rights Museum at the Lorraine Motel (closed Tuesdays), located on the site where Dr. Martin Luther King, Jr., was assassinated in 1968. Don't miss the museum's interactive Voices of the Civil Rights Movement kiosk, a compelling touchscreen exhibit featuring firsthand testimonials and historical video clips.
To see where Elvis Presley launched his career, visit historic Sun Studio. After the studio tour, ride the free shuttle to Presley's iconic Graceland mansion and on to the Memphis Rock 'n' Soul Museum. End the day—and the trip—on world-famous Beale Street, where you can hear live blues, rock, jazz, and other sweet Memphis sounds any night of the year.
Eat and Stay: Charlie Vergos Rendezvous (closed Mondays) and River Inn of Harbor Town
Maryellen Kennedy Duckett lives, writes, and drives the backroads in East Tennessee where she wakes up curious every day. You can follow her on Twitter @mekd.