Thermal and acoustic properties of chrysotile asbestos

The thermal conductivity, specific heat, and sound velocity of crystalline chrysotile asbestos made up of hollow tubular fibrils of composition Mg₃Si₂O₅(OH)₄ have been measured at temperatures of 5–300, 3–65, and 77 K, respectively. An analysis is made of the experimental data obtained.     

Capacity and thermal conductivity of a nanocomposite chrysolite asbestos-KDP (KH2PO4)

A nanocomposite chrysotile-KDP (KH₂PO₄) was prepared. KDP was introduced into empty nanochannels of chrysotile asbestos with diameters of ～5 nm. Thermal conductivity κ and heat capacity at a constant pressure C _p of the samples of chrysotile asbestos and nanocomposite chrysotile asbestos-KDP were measured in a temperature range of 80–300 K. Based on the analysis of the behavior of temperature dependences κ(T) and C _p (T) of the composite, temperatures of the ferroelectric transition T _F for KDP in nanochannels of chrysotile asbestos were determined. It turned out to be equal to ～250 K at T _F ～ 122 K for massive KDP samples.     

Thermal conductivity of ultrathin InSb semiconductor nanowires with properties of the Luttinger liquid

The thermal conductivity of ultrathin (～5 nm in diameter) and long (10 mm) InSb semiconductor quantum nanowires embedded in nanochannels of a dielectric chrysotile asbestos matrix is measured in the temperature range 5–300 K. The possible manifestation of the spin-charge separation of current carriers in these nanowires is discussed, which would provide an additional argument for the InSb nanowires possessing properties of the Luttinger liquid.     

Comparative in vitro cytotoxicity assessment of some manufacturednanoparticulate materials characterized by transmissionelectron microscopy

A range of manufactured nanoparticulate materials, including Ag, TiO₂, Fe₂O₃, Al₂O₃, ZrO₂, Si₃N₄, and a range of carbonaceous nanoparticulate materials: single-wall and multi-wall carbon nanotube aggregates and aggregated nanoparticles of black carbon, as well as commercial (mineral grade) chrysotile asbestos nanotube aggregates, have been rigorously characterized by transmission electron microscopy. These nanoparticulate materials ranged in primary particle sizes from roughly 3 to 150 nm (except for the nanotube materials with lengths in excess of 15 μm). Aggregate sizes ranged from 25 nm to 20 μm. Comparative cytotoxicological assessment of these nanomaterials was performed utilizing a murine (lung) macrophage cell line. Considering the chrysotile asbestos to be a positive control, and assigning it a relative cytotoxicity index of unity (1.0), relative cytotoxicity indexes were observed as follows at concentrations of 5 μg/ml: 1.6 and ∼ 0.4 for Ag and TiO₂, respectively; 0.7–0.9 for the Fe₂O₃, Al₂O₃ and ZrO₂, 0.4 for the Si₃N₄, 0.8 for the black carbon, and 0.9 to 1.1 for the carbon nanotube aggregate samples. Observations of a cytotoxic response, nearly identical to that for chrysotile asbestos, for multi-wall carbon nanotube aggregates which very closely resemble anthropogenic multi-wall carbon nanotubes in the environment, raise some concern for potential health effects, especially for long-term exposure.     

Comparative <Emphasis Type="Italic">in vitro</Emphasis> cytotoxicity assessment of some manufacturednanoparticulate materials characterized by transmissionelectron microscopy

A range of manufactured nanoparticulate materials, including Ag, TiO₂, Fe₂O₃, Al₂O₃, ZrO₂, Si₃N₄, and a range of carbonaceous nanoparticulate materials: single-wall and multi-wall carbon nanotube aggregates and aggregated nanoparticles of black carbon, as well as commercial (mineral grade) chrysotile asbestos nanotube aggregates, have been rigorously characterized by transmission electron microscopy. These nanoparticulate materials ranged in primary particle sizes from roughly 3 to 150 nm (except for the nanotube materials with lengths in excess of 15 μm). Aggregate sizes ranged from 25 nm to 20 μm. Comparative cytotoxicological assessment of these nanomaterials was performed utilizing a murine (lung) macrophage cell line. Considering the chrysotile asbestos to be a positive control, and assigning it a relative cytotoxicity index of unity (1.0), relative cytotoxicity indexes were observed as follows at concentrations of 5 μg/ml: 1.6 and ∼ 0.4 for Ag and TiO₂, respectively; 0.7–0.9 for the Fe₂O₃, Al₂O₃ and ZrO₂, 0.4 for the Si₃N₄, 0.8 for the black carbon, and 0.9 to 1.1 for the carbon nanotube aggregate samples. Observations of a cytotoxic response, nearly identical to that for chrysotile asbestos, for multi-wall carbon nanotube aggregates which very closely resemble anthropogenic multi-wall carbon nanotubes in the environment, raise some concern for potential health effects, especially for long-term exposure.This revised version was published online in August 2005 with a corrected issue number.     

Raman spectroscopy of the nickel silicate mineral pecoraite—an analogue of chrysotile (asbestos)

The molecular structure of the mineral pecoraite, the nickel analogue of chrysotile of formula Ni₃Si₂O₅(OH)₄, was analysed by a combination of Raman and infrared spectroscopies. A comparison is made with the spectra of the minerals nepouite and chrysotile and a synthetic pecoraite. Pecoraite is characterised by OH stretching vibrations at 3645 and 3683 cm⁻¹ attributed to the inner and inner surface hydroxyl stretching vibrations. Intense infrared bands at around 3288 and 3425 cm⁻¹ are assigned to the stretching vibrations of water strongly hydrogen‐bonded to the surface of the pecoraite. The asbestos‐like mineral is characterised by SiO stretching vibrations at 979, 1075, 1128 and 1384 cm⁻¹, OSiO chain vibrations at 616 and 761 cm⁻¹ and Ni O(H) vibrations at 397 and 451 cm⁻¹. Copyright © 2008 John Wiley & Sons, Ltd.     

Light emission from three-dimensional ensembles of CdTe nanocrystal wires templated in nanotubes of chrysotile asbestos

Nanowires have been formed by the infiltration of CdTe nanocrystals (NCs) into nanotubes of chrysotile asbestos (Mg₃Si₂O₅(OH)₄). Photoluminescence of a regular array of these templated nanowires was studied under the excitation of the light from a xenon lamp at different wavelengths. Strong interactions of nanocrystals with structural defects of the template were observed. No dependence of the photoluminescence spectra upon polarisation of the laser beam was observed and no shift of the photoluminescence band was detected in the light polarised along and across nanowires, thus indicating the weakness of the interaction between nanocrystals in the nanotubes.     

Temperature dependence of thermal properties of Ag<Subscript>8</Subscript>In<Subscript>14</Subscript>Sb<Subscript>55</Subscript>Te<Subscript>23</Subscript> phase-change memory materials

The dependence of thermal properties of Ag₈In₁₄Sb₅₅Te₂₃ phase-change memory materials in crystalline and amorphous states on temperature was measured and analyzed. The results show that in the crystalline state, the thermal properties monotonically decrease with the temperature and present obvious crystalline semiconductor characteristics. The heat capacity, thermal diffusivity, and thermal conductivity decrease from 0.35 J/g K, 1.85 mm²/s, and 4.0 W/m K at 300 K to 0.025 J/g K, 1.475 mm²/s, and 0.25 W/m K at 600 K, respectively. In the amorphous state, while the dependence of thermal properties on temperature does not present significant changes, the materials retain the glass-like thermal characteristics. Within the temperature range from 320 K to 440 K, the heat capacity fluctuates between 0.27 J/g K and 0.075 J/g K, the thermal diffusivity basically maintains at 0.525 mm²/s, and the thermal conductivity decreases from 1.02 W/m K at 320 K to 0.2 W/m K at 440 K. Whether in the crystalline or amorphous state, Ag₈In₁₄Sb₅₅Te₂₃ are more thermally active than Ge₂Sb₂Te₅, that is, the Ag₈In₁₄Sb₅₅Te₂₃ composites bear stronger thermal conduction and diffusion than the Ge₂Sb₂Te₅ phase-change memory materials.     

Optical properties of polymethine molecules incorporated into a macroscopic set of parallel nanotubes

The structural properties of polymethine molecules incorporated into nanofibers of chrysotile asbestos have been studied by absorption-spectroscopy methods. These experiments have shown that, in chrysotile nanotubes, monomeric, all-trans- and cis-isomers, dimers and J aggregates can be observed. Upon incorporation of a dye from weakly concentrated solutions, monomeric forms of polymethine molecules, extended chromophores of which are oriented along parallel asbestos nanotubes, are predominantly observed. The hybrid material under investigation may be of interest for applied problems.     

Effect of nitrogen doping on the thermal conductivity of GeTe thin films

The 3ω method was employed to determine the effect of nitrogen doping (5 at.%) on the thermal conductivity of sputtered thin films of stoichiometric GeTe (a material of interest for phase change memories). It was found that nitrogen doping has a detrimental effect on the thermal conductivity of GeTe in both phases, but less markedly in the amorphous (–25%) than in the crystalline one (–40%). On the opposite, no effect could be detected on the measured thermal boundary resistance between these films and SiO₂, within the experimental error. Our results agree with those obtained by molecular dynamic simulation of amorphous GeTe. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Quick preparation and thermal transport properties of nanostructured β-FeSi2 bulk material

This paper reports that the nanostructured β-FeSi2 bulk materials are prepared by a new synthesis process by combining melt spinning(MS) and subsequent spark plasma sintering(SPS).It investigates the influence of linear speed of the rolling copper wheel,injection pressure and SPS regime on microstructure and phase composition of the rapidly solidified ribbons after MS and bulk production respectively,and discusses the effects of the microstructure on thermal transport properties.There are two crystalline phases(α-Fe2Si5 and ε-FeSi) in the rapidly solidified ribbons;the crystal grains become smaller when the cooling rate increases(the 20 nm minimum crystal of ε-FeSi is obtained).Having been sintered for 1 min above 1123 K and annealed for 5 min at 923 K,the single-phase nanostructured βFeSi2 bulk materials with 200-500 nm grain size and 98% relative density are obtained.The microstructure of β-FeSi2 has great effect on thermal transport properties.With decreasing sintering temperature,the grain size decreases,the thermal conductivity of β-FeSi2 is reduced remarkably.The thermal conductivity of β-FeSi2 decreases notably(reduced 72% at room temperature) in comparison with the β-FeSi2 prepared by traditional casting method.     

The transport and thermal properties of glassy LiPO<Subscript>3</Subscript>/crystalline Al<Subscript>2</Subscript>O<Subscript>3</Subscript> (ZrO<Subscript>2</Subscript>) composite electrolytes

Glassy LiPO₃/crystalline Al₂O₃ and glassy LiPO₃/crystalline ZrO₂ (0–12.5 vol.% of oxide fillers) composite solid electrolytes have been prepared by glass matrix softening. Their thermal and transport properties have been investigated by differential scanning calorimetry (DSC) and impedance spectroscopy methods. The addition of ZrO₂ leads to a decrease in the crystallization temperature of LiPO₃ glass. It was found that the conductivity behavior depends on the nature of the dispersed addition. In the case of the Al₂O₃ addition, the increase in the electrical conductivity is observed. The ionic conductivity of the LiPO₃/10% Al₂O₃ composite reaches 5.8 × 10^?8 S/cm at room temperature. In contrast, the conductivity in the LiPO₃/ZrO₂ composite system decreases.     

Structural properties and current transport in a nanocomposite formed on a silicon surface by oxidation of the porous layer

The possibility of obtaining a Si-SiO₂ nanocomposite layer by oxidation of porous silicon is demonstrated. The nanocomposite thus prepared consists of silicon oxide with inclusions of crystalline silicon in the form of rounded particles 5 to 30 nm in diameter and a filamentary cellular structure with filaments a few nanometers thick. The I-V characteristics of these structures were measured under different sample excitation conditions (photo-and thermal stimulation). The trap concentration and effective carrier mobility are estimated. Carriers are found to be captured intensely by traps created in the large-area interface in the composite structure.     

Electrical and Magnetic Properties of Pb and In Nanofilaments in Asbestos near the Superconducting Transition

Bulk nanocomposites based on superconducting metals Pb and In embedded into matrices of natural chrysotile asbestos with the nanotube internal diameter d ~ 6 nm have been fabricated and studied. The low-temperature electrical and magnetic properties of the nanocomposites demonstrate the superconducting transition with the transition critical temperature T_c ≈ (7.18 ± 0.02) K for the Pb–asbestos nanocomposite (this temperature is close to T_{c bulk} = 7.196 K for bulk Pb). The electrical measurements show that In nanofilaments in asbestos have T_c ~ 3.5–3.6 K that is higher than T_{c bulk} = 3.41 K for bulk In. It is shown that the temperature smearing of the superconducting transition in the temperature dependences of the resistance R(T) ΔT ≈ 0.06 K for the Pb–asbestos and ΔT ≈ 1.8 K for the In–asbestos are adequately described by the fluctuation Aslamazov–Larkin and Langer–Ambegaokar theories. The resistive measurements show that the critical magnetic fields of the nanofilaments extrapolated to T = 0 K are H_c(0) ~ 47 kOe for Pb in asbestos and H_c(0) ~ 1.5 kOe for In in asbestos; these values are significantly higher than the values for the bulk materials (H\(H_{\rm{c}}^{\rm{bulk}}\) = 803 Oe for Pb and \(H_{\rm{c}}^{\rm{bulk}}\) = 285 Oe for In). The results of the electrical measurements for Pb?asbestos and In–asbestos agree with the data for the magnetic-field dependences of the magnetic moment in these nanocomposites.     

Specific heat and thermal conductivity of superionic conductors in the superionic phase

The temperature dependences of the specific heat and the thermal conductivity of crystalline superionic conductors LnF₃ (Ln = La, Ce, Pr), Li₂B₄O₇ and α-LiIO₃ in the superionic phase have been investigated experimentally. The specific heat C _p and the thermal conductivity K are observed to increase monotonically over a wide range of temperatures above the Debye temperature Θ_D. This increase is attributed to the relaxational interaction of high-frequency phonons with two-level systems. Fiz. Tverd. Tela (St. Petersburg) 39, 1548–1553 (September 1997)     

非晶态离子导体Li2B2O4晶化前期的离子导电性

本文研究了非晶态离子导体Li₂B₂O₄的离子电导率与温度的关系,特别着重于晶化前期的离子迁移特性。当温度低于T_K(≈310℃)时,离子电导率遵从Arrhenius关系。当高于晶化温度(≈411℃)时,以晶态中的离子迁移为主。在T_kc时,电导率偏离热激活机制呈反常增高。我们把这一过程称为晶化前期过程。可以用自由体积模型进行描述。晶化前期又可分为两部分:当温度低于、T_p(≈380℃)时,由于自由体积的重新分布,导致了电导率的增高;当T>T_p时,出现了少量微晶,但晶化量小于5%,由于非晶母体与微晶之间的界面效应使得离子导电性显著增强。可以通过室温淬火,把晶化前期非晶态的状态保持到室温,从而有可能制备出离子电导率高于纯非晶态的材料。 关键词：     

Influence of crystal-field on the thermal conductivity of PrNi5

The thermal conductivity of PrNi₅ in the temperature range 0·5 to 20 K is investigated. The analysis of crystalline electric field effect on the experimentally obtained temperature dependence of the thermal conductivity indicates that beside the main electronic component also other contributions (phonons, magnetic excitons) can take place in the heat transport in this intermetallic compound.The authors would like to thank Dr. G. Eska for lending the sample and Dr. . Jáno for his interest in the work and stimulating discussions.     

Anomalous thermal conductivity of single crystal Cu2Te2O5Cl2

A strong increase of the thermal conductivity is observed at the phase transition (T _c=18.2 K) in Cu₂Te₂O₅Cl₂ single crystal. This behavior is compared with that of the spin-Peierls system NaV₂O₅, where a similar experimental observation has been made, and the conventional spin-Peierls system CuGeO₃, where a modest kink in the thermal conductivity curve has been observed. The strong increase of the thermal conductivity atT _c in Cu₂Te₂O₅Cl₂ could be partially attributed to the opening of the energy gap in the magnetic excitation spectrum evident from the magnetic susceptibility measurements. However, the main reason for the anomaly of the thermal conductivity could be explained by a strong spin-lattice coupling in this system, which what is in agreement with the preliminary X-band electron spin resonance measurement.     

Characterization of CuAlO2 thin film prepared by rapid thermal annealing of an Al2O3/Cu2O/sapphire structure

CuAlO₂ thin film was successfully prepared by rapid thermal annealing of an Al₂O₃/Cu₂O/sapphire structure in air above 1000 °C. The film was mostly with single crystalline structure as verified by X-ray diffraction methods. We found that crystal quality and electrical conductivity of the films were affected by the cooling rate after annealing. The highest conductivity obtained in this work was 0.57 S/cm. Optical gap of this film was determined to be 3.75 eV.