Sublimation Of Naphthalene Research Articles

Influence of solid-surface vibrations on mass transfer

The results of an experimental study of mass transfer from a vibrating flat disk to a gas medium have been given. It has been shown that a substantial increase in the rate of sublimation of solid naphthalene in a laminar air flow is observed in the frequency range of 20–200 Hz and at amplitudes of 0.08–7.02 mm. An empirical dependence that connects the Sh number with the vibrational Re number has been obtained.

Estimating vapor enthalpies of sublimation by rising-temperature absorbance spectroscopy

Determining the enthalpies of sublimation of low volatile materials in the vapor phase is favored. Although benzoic acid, ferrocene, and naphthalene are used as reference materials in instrumentation calibration for indirect determination of vapor pressure of low volatile materials, the discrepancy of the values of their enthalpies of sublimation is considerably large (∼10–15 kJ mol−1). Time is a crucial factor in determining thermodynamic parameters for hazardous materials. In this article, we illustrate the use of UV–Vis absorbance spectroscopy in determining the enthalpies of sublimation of these materials in the vapor phase non-isothermally. The enthalpies of sublimation of benzoic acid, ferrocene, and naphthalene are found to be 86.11 ± 0.6, 72.40 ± 0.8, and 69.13 ± 0.3 kJ mol−1, respectively. The determined values of enthalpies of sublimation are in good agreement with the mean value of those reported in the literature and those recommended by the kinetic committee of ICTAC. The results suggest that UV absorbance spectroscopy is a reliable tool in non-isothermally measuring the thermodynamic properties of materials in the vapor phase.

Carbon coating for Si nanomaterials as high-capacity lithium battery electrodes

We report a new method to generate a thin carbon layer on active materials for electrochemical energy storage. A solid precursor can be simply placed on the target material in a tailored vertical quartz tube and sublimated at a slightly high temperature. The carbon source gas remains around the target material during the heat treatment because of the vapor density difference and subsequent decomposition of the gas phase leads to a uniform carbon coating. For demonstration of the concept, carbon coating on Si nanoparticles, which are a high-capacity anode material for lithium-ion batteries, was realized by sublimation and decomposition of naphthalene. A conformal carbon layer was confirmed by various analyses and improved electrochemical performance of the Si nanoparticle electrode was clearly exhibited.

Pressureless Sintering of Silicon Nitride Porous Ceramics with High Porosity and Bimodal Pore Structure

In this paper, silicon nitride porous ceramics with high porosity and bimodal pore structure were prepared using pressureless sintering at 900~1100°C. In these porous ceramics, zirconium phosphate (ZrP2O7) was used as a binder and starch and naphthalene powders were used as pore forming agents. The obtained results showed that the porosity could be controlled in the range of 34 % to 70 % by changing the content of pore forming agents. The pores were formed by the continuous reaction of ZrP2O7 at ~250 °C and burnout of starch at ~550 °C (when starch was used as a pore forming agent), or sublimation of naphthalene at 80°C (when naphthalene was used as a pore forming agent). The bimodal pore structure was produced with pore size of less than 0.5m and ~10 m when using starch as a pore forming agent and the pore size of less than 0.5m and ~30μm when using naphthalene as a pore forming agent.

Mechanical Properties of Silicon Nitride Porous Ceramics with Bimodal Porosity

In this Paper, Silicon Nitride Porous Ceramics with Hierarchical Porosity Were Prepared Using Pressureless Sintering and their Mechanical Properties as a Function of Porosity and Pore Size Were Analyzed. In these Porous Ceramics, Macro-Pores with the Pore Size of 0.1 µm Were Formed by the Continuous Reaction of ZrP2O7 at ~250 °C and Macro-Cellular Pores with the Pore Size of 10~30μm Were Formed by the Burnout of Starch at ~550 °C or the Sublimation of Naphthalene at 80 °C. The Flexural Strength Decreased from 105 MPa to 6 MPa with the Porosity Increased from 35% to 65%. The Obtained Results Showed that the Flexural Strength Was Fit for the Equation of σ=σ0exp(-bP), where σ0 Is the Bending Strength of Nonporous Body of the same Material, P Is the Porosity and b Is the Factor Determines by Pore Structure. The Difference of Pore Size Was Determined by the Different Value of b and the Value of b Increased with the Increasing of Pore Size. Macro-Pores with the Pore Size of 0.1 µm Referred to a b Value of 4.3 and Macro-Cellular Pores with the Pore Size of 10 μm and 30 μm Referred to a b Value of 5.1 and 6.0 Respectively.

Spontaneous Crystalline-to-Amorphous Phase Transformation of Organic or Medicinal Compounds in the Presence of Porous Media, Part 1: Thermodynamics of Spontaneous Amorphization

Spontaneous crystalline-to-amorphous phase transformation of organic or medicinal molecules in the presence of mesoporous materials has been observed, for which pathway was suggested to be via the vapor phase, that is, sublimation of the crystalline molecules followed by adsorption on the porous media. The objective of this paper is to rigorously evaluate this amorphization pathway and to study the thermodynamics of spontaneous amorphization. Mesoporous silicon dioxide (SiO(2)) was used as a model system. Physical mixtures of SiO(2) and crystalline compounds were prepared and stored at 0% relative humidity (RH) and 40 °C. Loss of crystallinity of the model compounds was confirmed using powder X-ray diffraction and polarized light microscopy. Adsorption chamber was set up, in which naphthalene and SiO(2) were stored, without physical contact, under reduced pressure at 0% RH and 40 °C. Data confirmed that the rate and extent of sublimation and adsorption of naphthalene were significant for amorphization to occur on a pharmaceutically relevant timescale. Furthermore, a thermodynamic model has been developed to explain spontaneous amorphization. This unique phase transformation phenomenon can be a simple and effective method to improve the aqueous solubility and bioavailability of poorly soluble drug molecules.

Syndiotactic Polystyrene / Fullerene Composites: Elucidation of Structural Aspect

AbstractSummary: Syndiotactic polystyrene (sPS), an attractive polymer due to its wide range of application, forms polymer‐solvent intercalates with a large variety of solvent molecules ranging from liquids to solids. Recently, it has been realized that sPS intercalate prepared from SPS/naphthalene gel is more promising of making mesoporous materials. Here, the composite of sPS/fullerene have been prepared by taking advantage of sublimation of naphthalene. The different techniques as like XRD, SEM, HRTEM, FT‐IR, DSC, TGA etc have been employed to characterized sPS/fullerene composite. XRD investigation shows the presence of δ form sPS in the composite. SEM and HRTEM reveal the fibrillar network with fringe like structure in presence of fullerene only and the average diameter of fibril has increased as compared to pure sPS fibrils. The conductivities of these fibrils have been increased with increasing amount of fullerene.

Anti-agglomerating effect in vertically aligned carbon nanotubes derived by antisolvent precipitation of naphthalene

We developed a novel anti-agglomeration method that enables preservation of the vertical alignment of carbon nanotubes (CNTs) during desiccation of wet CNTs by utilizing antisolvent precipitation and sublimation of naphthalene (Nap). Moreover, we succeeded in depositing Pt nanoparticles onto CNTs without collapse of the vertically aligned morphology by this method.

A multiscale mass transfer model for gas–solid riser flows: Part 1 — Sub-grid model and simple tests

The gas–solid mass transfer in circulating fluidized bed (CFB) riser flow is both structure-dependent and dynamic in nature. Recent progress in multiscale computational fluid dynamics (CFD) allows fresh insight into the dynamic flow structure, yet its influence on the mass transfer remains to be settled. To this end, a multiscale mass transfer model is established in this paper based on the extended framework of the energy-minimization multiscale (EMMS) model. The relevant algorithm named EMMS/mass is proposed for CFD-coupled mass transfer computation. Two testing cases accounting for sublimation of naphthalene and decomposition of ozone, respectively, are presented to demonstrate the characters of the model. It is shown that structural consideration can have significant effects on the model prediction. The normally used Reynolds number is not adequate to characterize these effects, while the combination of gas velocity and solids flux seems to capture the structural effects and allows to explain the variation of Sherwood number reported for CFB risers in the literature. Sub-grid coupling of this multiscale mass transfer model and CFD approach can be expected to provide a promising tool to probe the dynamic and structure-dependent nature of mass transfer in CFB risers.

Calling Behavior of the Cerambycid Beetle Neoclytus acuminatus acuminatus (F.)

Males of the cerambycid beetle Neoclytus acuminatus acuminatus (F.) assume a body posture, never displayed by females, that appears to be associated with release of an aggregation pheromone: they periodically stop walking and fully extend their front legs, elevating their head and thorax above the substrate. In this article, we demonstrate that this body posture, the “pushup stance,” coincides with release of pheromone and that it serves to elevate pheromone glands above the substrate. We also use a pheromone proxy system (sublimation of naphthalene) to demonstrate that the pushup stance increases rates of pheromone dissemination. The pushup stance provides a convenient indictor for studying the role of pheromones in reproductive behavior and facilitating collection of pheromone in the laboratory.

Empirical atom-atom potential for a naphthalene crystal and transferability to other polyacene crystals

Intermolecular potentials for polyacenes are represented by an atom-atom potential approximation using a revised carbon-carbon interatomic potential. The potential has an attraction term with an r-n (n = 6, 8, or 10) dependence and a repulsion term of exp (-Cr) dependence with respect to the interatomic distance r; parameters were optimized for the crystal structure and the heat of sublimation of naphthalene by molecular dynamics simulations. The potential shape is deeper and steeper at short ranges than generally accepted former potentials. Crystal structures of polyacenes (benzene, naphthalene, anthracene, tetracene, pentacene, and hexacene) are calculated numerically by molecular dynamics at room temperature using the potentials. In accordance with experimental results, the calculated crystal systems and space groups are orthorhombic Pbca in benzene, monoclinic P21/a in naphthalene and anthracene, and triclinic P1 in tetracene, pentacene, and hexacene for all n, except benzene for n = 10. The agreement in the lattice constants and molecular orientations is fairly good and best for n = 8: the average deviations are 0·8% and 0·8° for the unit cell lengths and angles, respectively, and 2·0° for the molecular orientation.

Evaluation of the Stagnation Point Region Overshoot

Stagnation point region overshoot is the augmentation of total heat transfer owing to the presence of insulation at the stagnation point region of an otherwise isothermal body. Evidence summarized by the present work indicates that this paradoxical event can be made to occur. The overshoot is due to the singularly high temperature gradient that is impressed upon the boundary layer just as it arrives at the leading edge of the heated surface after passing over the insulated central portion. The evidence comprises experimental results based on the mass-heat analog using sublimation of naphthalene and on theoretical boundary layer calculations using a method of local similarity. In the experiments, the insulated surfaces were simulated with inert wax, and isothermal regions with active naphthalene. The surfaces were circular disks facing uniform airstreams. The finding was that the total rate of mass transfer would be as much as 10 percent greater than that of a fully active disk if the radius of the central inert region were half the radius of the disk. Put another way, if only the 30-percent annulus at the outer edge of the disk were active, it would transfer mass at the same rate as the completely active disk under the same circumstances of flow. Corresponding results are expected from analogically heated disks operating with Prandtl number near unity and disk Reynolds number ranging from 5000 to 250,000.

A new method for the measurement of enthalpies of sublimation using differential scanning calorimetry

The enthalpies of sublimation of naphthalene, benzoic acid and phenanthrene have been determined by isothermal operation of a DSC, coupled to a vacuum system. The results obtained by this method are in excellent agreement with those reported in the literature from established procedures. The precision obtained was found to be dependent on the rate of sublimation. This paper describes the experimental procedure, calibration, the corrections applied and comparison of the results, mainly with those obtained by dynamic experiments in DSC.

Effects of solid dispersion with heptakis-(2,6-di-O-methyl)-.BETA.-cyclodextrin on the dissolution and sublimation of naphthalene.

The solid dispersion of naphthalene with heptakis-(2, 6-di-O-methyl)-β-cyclodextrin (DMCD) has been studied by using X-ray diffraction and thermal methods. The influence of the solid dispersion on the dissolution and sublimation of naphthalene were studied. X-Ray diffraction and thermal data indicated the amorphous state of naphthalene and DMCD. Enhanced dissolution and reduced sublimation characteristics were observed in the ground mixture and the coprecipitate. The sublimation rate of naphthalene from the ground mixture and the coprecipitate increased during storage at high relative humidity due to crystallization.

An experimental investigation of burning rate and mass transfer in a turbulent fluidized bed

Burning rates of carbon spheres are measured in a 102 mm diameter bed fluidized in the turbulent regime. Results suggest carbon burns much faster than in a bubbling fluidized bed operating under otherwise similar conditions—excepting velocity. The enhanced burning rate is attributed to high mass transfer rates in a turbulent fluidized bed. This indirect observation of high mass transfer rate in turbulent fluidized beds is confirmed by a series of mass transfer (sublimation of naphthalene) experiments in the same bed. For the prediction of mass transfer in turbulent fluidized beds, a correlation of the Sherwood number is proposed. It shows a fair agreement with experimental data.

Full-coverage film cooling on the curved walls. 1st report Mass transfer coefficients on a convexly curved wall.

The effect of wall curvature on the full-coverage film cooling has been experimentally studied by using the concave, flat and convex walls. The preliminary consideration, based on the balance of the centrifugal force associated with the injected fluid element an the pressure gradient normal to the wall, leads to the fact that the secondary fluid tends to depart away from the concave wall and attach to the convex wall. In this report, the local Stanton number ( mass transfer coefficients) on the convexly curves wall have been measured by using the technique of sublimation of naphthalene. The characteristics of mass transfer were discussed by varying blowing ratios M and non-dimensional injection temperature θ. By comparing with the results of the flat FCFC wall, thee local Stanton numbers were considerably reduced by curvature effects. In addition to the above the spanwise averaged Stanton numbers on the recovery wall have been measured.

A wind tunnel model study of forced convective heat transfer from a horizontal grain storage shed

Dry sublimation of naphthalene was used to simulate the forced convective heat transfer from a model grain storage shed in a wind tunnel. The mass transfer of naphthalene vapour simulated heat transfer from a constant temperature boundary. Expressing the heat transfer in terms of the nondimensional Nusselt number Nu and the wind speed in terms of the Reynolds number Re, the relationship Nu = 0.227 Re 0.633 was derived. The change in heat transfer for different orientations of the shed to the wind direction was not statistically significant.

Vapour pressures and enthalpies of sublimation of naphthalene and benzoic acid

Vapour pressures of crystalline naphthalene and benzoic acid, at temperatures near ambient, have been determined using an improved Knudsen effusion technique. From the experimental results the following values have been derived for the enthalpies of sublimation: naphthalene(c): ΔH s(298.15 K) = (72.8 ± 0.3) kJ · mol −1; benzoic acid(c): ΔH s(298.15 K) = (90.6 ± 0.2) kJ · mol −1. Experimental results are compared with literature values.

Studies on Heat Transfer to Turbulent Jets with Adjacent Boundaries : 3rd Report, Mass Transfer to Plane Turbulent Jet Reattached on an Offset Parallel Plate

Heat transfer to plane turbulent jet reattached on an offset parallel flat plate for the nozzle has been studied by the law of analogy to mass transfer. For the experiment the technique of sublimation of naphthalene is used. The flow development on an offset plate depends on shapes of bubbles induced due to separation and reattachment. The change of bubble shape occurs generally when the ratio of offset distance to nozzle height is 6.5. Considering such flow field, empirical formulae have been introduced for the following items. (1) Maximum Sherwood number in reattached region. (2) Mean Sherwood number in separated bubble region. (3) Local Sherwood number over the region of reattached wall jet. (4) The effect of reattachment by the curved jet on distribution of the local Sherwood numbers.

Empirische gleichungen zur berechnung der stoff- und wärmeübertragung für den spezialfall der abgerissenen strömung

It was examined the convective mass-transfer (heat-transfer) out of three dimensional cavities, which were in the plane wall of a current-duct. The Reynolds-number was varied in the range 4.10 2–10 6. Average mass-transfer-coefficients on the side of the cavity were measured at sublimation of naphthalene and paradichlorbenzene respectively into air ( Sc = 2.5 Sc = 2.2). The heat-transfer in air was examined at Pr = 0.7. It was found out that the average Sherwood-number, related to the separating plain, is mainly dependent on the Reynolds-number for the separating plain. Against that depth and cavity-shape have only an unimportant influence. An extensive generally valid representation of the experimental data with the rules of the theory of similarity is possible for all cavity-shapes examined, if it is distinguished among three typical ranges. In these ranges the flow-phenomena on the separating plain can be explained by the aid of a fictive flow-model. The range I comprises the Reynolds-numbers for the separating plain ⩾ 10 4. The separating layer dissolves periodically and enters continuously into the cavity. The range II is formed by the Reynolds-numbers for the canal-flow ⩾ 2300 and the Reynolds-numbers for the separating plain ⩽10 4. The separating layer is unstable. It dissolves intermitting and enters with this rhythm into the cavity. The range III lies at Reynolds-numbers for the canal-flow ⩽2300. The separating layer remains stable and flows over the cavity. With the following empirical equations the experimental data can be well expressed: Range I: S ̂ h = 0,26 5 ̂ R ̂ e 0.7 Sc n(fr) f K 0.2 Range II: S ̂ h = 0,001 R ̂ e 1.33 Range III: S ̂ h = 0,001 R ̂ e 1.33 [1 + 0,75.10 3(Gr */ R ̂ e 5.33) 0.25