Transition from the exhibition to the nonexhibition of negative differential thermal resistance in the two-segment Frenkel-Kontorova model

An extensive study of the one-dimensional two-segment Frenkel-Kontorova FK model reveals a transition from the counterintuitive existence to the ordinary nonexistence of a negative-differential-thermal-resistance NDTR regime, when the system size or the intersegment coupling constant increases to a critical value. A “phase” diagram which depicts the relevant conditions for the exhibition of NDTR was obtained. In the existence of a NDTR regime, the link at the segment interface is weak and therefore the corresponding exhibition of NDTR can be explained in terms of effective phonon-band shifts. In the case where such a regime does not exist, the theory of phonon-band mismatch is not applicable due to sufficiently strong coupling between the FK segments. The findings suggest that the behavior of a thermal transistor will depend critically on the properties of the interface and the system size.

Thermochemical and thermal analysis on N-(p-methylphenyl)-N '-(2-pyridyl)urea

Low temperature heat capacities of N-(p-methylphenyl)-N'-(2-pyridyl)urea were determined by adiabatic calorimetry method in the temperature range from 80 to 370 K. It was found that there was not any heat anomaly in this temperature region. Based on the experimental data, some thermodynamic function results were obtained. Thermal stability and decomposition characteristics analysis of N-(p-methylphenyl)-N'-(2-pyridyl)urea were carried out by DSC and TG. The results indicated that N-(p-methylphenyl)-N'-(2-pyridyl)urea started to melt at ca. 426 K (153degreesC) and the melting peak located at 447.01 K (173.86degreesC). The melting enthalpy was 204.445 kJ mol(-1) (899.6 J g(-1)). The decomposition peak of N-(p-methylphenyl)-N'-(2-pyridyl)urea was found at 499.26 K (226.11degreesC) from DSC curve. This result was similar with that from TG and DTG experiment, in which the mass loss peak was determined as 500.4 K (227.2degreesC).

Calorimetric study and thermal analysis of crystalline nicotinic acid

As one primary component of Vitamin B-3, nicotinic acid [pyridine 3-carboxylic acid] was synthesized, and calorimetric study and thermal analysis for this compound were performed. The low-temperature heat capacity of nicotinic acid was measured with a precise automated adiabatic calorimeter over the temperature rang from 79 to 368 K. No thermal anomaly or phase transition was observed in this temperature range. A solid-to-solid transition at T-trs = 451.4 K, a solid-to-liquid transition at T-fus = 509.1 K and a thermal decomposition at T-d = 538.8 K were found through the DSC and TG-DTG techniques. The molar enthalpies of these transitions were determined to be Delta(trs)H(m =) 0.81 kJ mol(-1), Delta(fus)H(m) 27.57 kJ mol(-1) and Delta(d)H(m) = 62.38 kJ mol(-1), respectively, by the integrals of the peak areas of the DSC curves.

Calorimetric study and thermal analysis of berberine sulphate

The heat capacities of berberine sulphate [(C20H18NO4)(2)SO4.3H(2)O] were measured from 80 to 390 K by means of an automated adiabatic calorimeter. Smoothed heat capacities,{H-T-H-298.15} and {S-T-S-298.15} were calculated. The loss of crystalline water started at about 339.3+/-0.2 K, and its peak temperature was 365.8+/-0.6 K. The peak temperature of decomposition for berberine sulphate was at about 391.4+/-0.4 K by DSC curve. TG-DTG analysis of this material was carried out in temperature range from 310 to 970 K. TG and DSC curves show that there is no melting in the whole heating process.

Failure of the plasma-sprayed coating of lanthanum hexaluminate

Lanthanum magnesium hexaluminate (LaMgAl11O19, LMA) is an attractive material for thermal barrier coatings (TBCs), and the failure of its coating was studied in this work by thermal cycling, X-ray diffraction, dilatometric measurement and thermal gravimetric-differential thermal analysis. The dilatometric measurement indicates that even though the bulk material of LMA has a higher sintering-resistance than the typical TBC material, i.e. yttria-stabilized zirconia (YSZ), the plasma sprayed coating of LMA has two serious contractions due to the re-crystallization of LMA and phase transitions of alumina.

Application to polymer characterization by thermal analysis

The measured results of thermal analysis depend on experimental conditions. The international and national organizations have constituted a series of methods to characterize the physical and chemical properties for substances. The applications to physical transition, chemical reaction, and characteristic parameters of substances are given in the article as examples.

Double-ceramic-layer thermal barrier coatings of La2Zr2O7/YSZ deposited by electron beam-physical vapor deposition

Double-ceramic-layer(DCL) thermal barrier coatings (TBCs) of La2Zr2O7 (LZ) and yttria stabilized zirconia (YSZ) were deposited by electron beam-physical vapor deposition (EB-PVD). The composition, crystal structure, surface and cross-sectional morphologies and cyclic oxidation behavior of the DCL coating were studied. Both the X-ray diffraction (XRD) and thermogravimetric-differential thermal analysis (TG-DTA) prove that LZ and YSZ have good chemical applicability to form a DCL coating. The thermal cycling test at 1373 K in an air furnace indicates the DCL coating has a much longer lifetime than the single layer LZ coating. and even longer than that of the single layer YSZ coating. The failure of the DCL coating is a result of both the bond coat oxidation and the thermal strain between bond coat and ceramic layer generated by the thermal expansion mismatch.

Coordination-Induced Formation of One-Dimensional Nanostructures of Europium Benzene-1,3,5-tricarboxylate and Its Solid-State Thermal Transformation

Novel one-dimensional europium benzene-1,3,5-tricarboxylate compressed nanorods have been synthesized oil it large scale through direct precipitation in solution phase under moderate conditions without the assistance of any surfactant, catalyst, or template. The obtained nanorods have widths of about 50-100 not, thicknesses of 10-20 nm, and lengths ranging from a few hundred nanometers to several micrometers. X-ray powder diffraction. elemental analysis, Fourier transform infrared Studies, and thermogravimetric and differential thermal analysis show that the nanorods have the structural formula of Eu(1,3,5-BTC)center dot 6H(2)O. Upon UV excitation, these nanorods exhibit a highly efficient luminescence. which comes from the Eu3+ ions. Moreover, Eu2O3 nanorods Could also be obtained via a thermal decomposition method using the corresponding complex as a precursor. This synthetic route is promising for the preparation of other one-dimensional crystalline nanomaterials because of its simplicity and the low cost of the starting reagents.

Rapid synthesis of Mn0.65Zn0.35Fe2O4/SiO2 homogeneous nanocomposites by modified sol-gel auto-combustion method

MnZn-ferrite/SiO2 nanocomposites with different silica content were successfully fabricated by a novel modified sol-gel auto-combustion method using citric acid as a chelating agent and tetraethyl orthosilicate (TEOS) as the source of silica matrix. The auto-combustion nature of the dried gel was studied by X-ray diffraction (XRD), Infrared spectra (IR), thermogravimetry (TG) and differential thermal analysis (DTA). Transmission electron microscope (TEM) observation shows that the MnZn-ferrite particles are homogeneously dispersed in silica matrix after auto-combustion of the dried gels. The magnetic properties vary with the silica content. The transition from the ferromagnetic to paramagnetic state is observed by Mossbauer spectra measurement with the increasing silica content. Vibrating sample magnetometer (VSM) shows that the magnetic properties of Mn0.65Zn0.35Fe2O4/SiO2 nanocomposites strongly depend on the silica content.

A new oxide ion conductor: La3GaMo2O12

A new oxide ion conductor, La3GaMo2O12, with a bulk conductivity of 2.7 X 10(-2) S.cm(-1) at 800 degrees C in air atmosphere was prepared by the traditional solid-state reaction. The room temperature X-ray diffraction data could be indexed on a monoclinic cell with lattice parameters of a=0.5602(2) nm, b=0.3224(1) nm, c= 1.5741(1) nm, beta= 102.555(0)degrees, V=0.2775(2) nm(3) and space group Pc(7). Ac impedance measurements in various atmospheres further support that it is an oxide ion conductor. This material was stable in various atmospheres with oxygen partial pressure P(O-2) ranging from 1.0 X 10(5) to 1.0 X 10(-7) Pa at 800 degrees C. A reversible polymorphic phase transition occurred at elevated temperatures as confirmed by the differential thermal analysis and dilatometric measurement.

Differential proteomic analysis of neonatal cardiomyocytes in response to beta-adrenergic receptor stimulation

beta-Adrenoceptors(beta-ARs) play a critical role in regulating cardiac functions under both physiological and pathological conditions. To further explore the mechanisms through which beta-ARs perform its actions, proteomic approaches were adopted to study the global protein patterns in cultured neonatal rat cardiomyocytes exposed to isoproterenol (ISO). A modified method, "Mirror Images in One Gel", was used to improve the reproducibility and resolution power of two-dimensional electrophoresis. A 2-DE map with a good reproducibility was obtained in which 1281 70 spots were detected and about 1191 +/- 54 spots were matched, with an average matching rate of 92.9%. Nine proteins with significant changes were identified by using peptide mass fingerprinting(PMF) data obtained via MALDI-MS.