Applications of thermoanalytical methods to the study of thin films

Studies of the formation and properties of thin films is a growing area in both science and technology. Characterization of these films and the processes by which they are prepared is a major factor in understanding, controlling, and optimizing their synthesis and usefulness.Thermal methods can play an important role in such studies, provided that they can overcome the difficulties imposed by the massive amount of associated substrate. Unless one is studying the film — substrate interaction, the substrate's presence only serves to decrease the sensitivity by diluting or reducing the thermal effect being measured.The three basic strategies that have evolved are discussed and examples described. One approach is to remove the film from the substrate, when this is appropriate and feasible, and then study the film separately. A second method is to use larger samples and careful measurements in an effort to overcome the reduced sensitivity. The final means is to develop very sensitive and/or selective techniques to investigate the film and its potential interactions with the substrate.

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Zusammenfassung Sowohl in Wissenschaft als auch in Technologie gewinnt die Untersuchung von Bildung und Eigenschaften dünner Schichten immer mehr an Bedeutung. Die Beschreibung dieser Schichten und ihres Herstellungsverfahrens ist ein wichtiger Gesichtspunkt zum Verständnis, zur Kontrolle und Optimierung ihrer Herstellung und Nutzbarkeit.In derartigen Untersuchungen können thermische Methoden eine wichtige Rolle spielen, vorausgesetzt es gelingt diejenigen Schwierigkeiten zu überwinden, die durch die beträchtliche Menge assoziierten Substrates verursacht werden. Untersucht man nicht gerade die Wechselwirkung Schicht-Substrat, dann verursacht die Gegenwart des Substrates durch Abschwächung oder Verringerung des gemessenen thermischen Effektes lediglich eine geringere Empfindlichkeit.Es werden die drei bestehenden Grundstrategien diskutiert und Beispiele beschrieben. Eine Lösung ist es, die Schicht, wenn es geeignet erscheint und möglich ist, vom Substrat zu entfernen und dann gesondert zu untersuchen. Eine zweite Methode ist die Verwendung grö\erer Proben und sorgfältiger Messungen, um die verringerte Empfindlichkeit zu überwinden. Die letzte Möglichkeit besteht in der Entwicklung empfindlicher und/oder selektiver Verfahren, um die Schicht und ihre potentiellen Wechselwirkungen mit dem Substrat zu untersuchen.

     

Application of thermoanalytical methods to the study of limestone sulphation

The role that can be played in the elucidation of the limestone sulphation mechanism by thermal analysis methods with some specific procedures is discussed. Contrasting examples of applications of thermoanalytical techniques using the variable conditions are provided. These examples deal with the programmed thermal analysis using different gas sequences, the influence the calcination and sulphation conditions on the capture of SO₂, the effect of catalysts on limestone sulphation and the thermal stability of CaSO₃. Two proposed mechanisms were supported by the phase identification of the solid products.     

Stability and compatibility study on enalapril maleate using thermoanalytical techniques

This paper demonstrates the application of thermal analysis in compatibility and stability studies between an ACE inhibitor (enalapril maleate) and excipients. The results have helped to elucidate the reason of a stability problem observed during the storage of enalapril maleate tablets. Incompatibility between enalapril maleate and colloidal silicon dioxide was detected. Besides, it was confirmed that the reaction between enalapril maleate and NaHCO₃ increases the thermal stability of the drug. This study supports the importance of using thermoanalytical methods in the development of pharmaceuticals.     

Crystal structure and thermoanalytical study of a manganese(II) complex with 1-allylimidazole

The crystal structure of a manganese(II) 1-allylimidazole complex ([Mn(1-AIm)₃(NO₃)₂], where 1-Aim=1-allylimidazole), was characterized by X-ray diffraction (XRD) using SHELX-97. The thermal behaviour of the complex was investigated by thermogravimetry (TG) coupled with an FTIR unit. The complex showed a multi-step decomposition related to the release of the ligand molecules, followed by oxidation. The final residue at 1073 K was found to be manganese(II) oxide. Evolved gas analysis allowed to prove the oxidative decomposition pattern of the examined complex, initially proposed by the percentage mass loss data. Finally, a kinetic analysis of the oxidative decomposition steps was made using the Kissinger equation, while the complex nature of the decomposition kinetics was revealed by the isoconversional Ozawa-Flynn-Wall method.     

Melting behaviour and evolved gas analysis of xylose

Two enantiomeric forms of xylose were identified as α-D-xylopyranose and α-L-xylopyranose by powder diffraction. Their melting behaviour was studied with conventional DSC and StepScan DSC method, the decomposition was studied with TG and evolved gases were analyzed with combined TG-FTIR technique. The measurements were performed at different heating rates. The decomposition of xylose samples took place in four steps and the main evolved gases were H₂O, CO₂ and furans. The initial temperature of TG measurements and the onset and peak temperatures of DSC measurements were moved to higher temperatures as heating rates were increased. The decomposition of L-xylose started at slightly higher temperatures than that of D-xylose and L-xylose melted at higher temperatures than D-xylose. The differences were more obvious at low heating rates. There were also differences in the melting temperatures among different samples of the same sugar. The StepScan measurements showed that the kinetic part of melting was considerable. The melting of xylose was anomalous because, besides the melting, also partial thermal decomposition and mutarotation occurred. The melting points are affected by both the method of determination and the origin and quality of samples. Melting point analysis with a standardized method appears to be a good measure of the quality of crystalline xylose. However, the melting point alone cannot be used for the identification of xylose samples in all cases.     

Synthesis, thermal and structural characterization of nanocomposites for potential applications in construction

Several calcium silicate hydrate (C–S–H)-polymer nanocomposite (C–S–HPN) materials have been prepared by incorporating poly(acrylic acid) (PAA) into the inorganic layers of C–S–H during precipitation of quasicrystalline C-S-H from aqueous solution. The synthetic C–S–HPN materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS), thermogravimetry (TG), differential thermogravimetry (DTG) and differential scanning calorimetry (DSC). The XRD peaks of C–S–HPN materials suggest the intermediate organizations presenting both intercalation of PAA and exfoliation of C–S–H. The SEM images of C–S–H and C–S–HPN materials with different PAA contents exhibit the significant differences in their morphologies. Effects of the material compositions on the thermal stability of series of C–S–HPN materials along with PAA and C–S–H has been studied by TG, DTG and DSC. Three significant decomposition temperature ranges were observed on the TG curves of all C–S–HPN materials.     

Study by thermal methods on the materials obtained by dye removal from waste waters with beech flour

The study is devoted to the characterization by both TG-DTG analysis and FTIR spectroscopy of beech flour, dyes and the sorbent-dyes products obtained through retention of the dyes from aqueous solution on the beech flour, to the aim of obtaining information on the nature of dyes’ retention, thermal behavior of the sorbent-dye materials as well as on their possible upgrading as fuel. Thermal analysis led to the conclusion that the mechanism of thermo-oxidative degradation is specific and the retention of dyes occurs on cellulose from beech flour. The nature of the bonds involved in dyes’ retention is also investigated by FTIR analysis, which evidences that dyes retention on cellulose is realized through hydrogen bonding between the NH and, respectively, OH groups from dye molecule and the oxygen atoms from cellulose. Involvement of the non-participating electrons of the nitrogen and, respectively, oxygen atoms of these groups in the extended electronic conjugation with aromatic nuclei strongly influences the capacity of the amino and, respectively, hydroxyl groups of forming hydrogen bonds, thus achieving dyes fixation on the sorbent. DTA analysis led to the conclusion that an improvement in the quality of the sorbent-dye materials as fuels is possible, as compared to untreated beach flour, as a result of the modification of the cellulosic fibers in the process of dyes retention.     

Study by thermal methods on some new cyclic ylides and derivatives

The study is devoted to the characterization by TG, DTG, DTA, both in air and N₂ atmosphere, of three cyclic ylides as well as two spirane derivatives, to the purpose of elucidating the correlation between structure, thermostability and thermal degradation mechanism. Thermal analysis data indicated that the degradation mechanism is characteristic for every sample, and the consequences of structural peculiarities are discussed. The thermostability series of the samples is correlated to their structure. The quantitative TG-DTG-DTA analysis allowed some considerations on the thermal degradation mechanism, subsequently confirmed by mass spectrometry. The melting points obtained by DTA and Boetius measurements along with the initial degradation temperatures from TG-DTG-DTA curves indicates the temperature range for the use and storage of these compounds, considering that some derivatives of cyclic ylides show biological activity and potential medical applications.     

Discovery of bound and unbound waters in crystalline amino acids revealed by thermal analysis

The thermal analytical study of most hydrophobic and hydrophilic D/L amino acids reveals significant hydropathy index correlation between the presence of water and crystalline amino acids. The TG derivative mass profiles for arginine and lysine (hydrophilic acids) at various time intervals of atmospheric exposure, show two distinct peaks, one between 50 and 60°C (unbound water), and one close to 100°C (bound-like water). The DSC heat-cool profiles for lysine and arginine confirmed the presence of these multiple waters with two heats of vaporization. The absence of these patterns from the TG and DSC for cysteine and phenylalanine (hydrophobic acids) further supports the conclusions.     

Synthesis of new linear polymers containing phosphorus atom in the main chain by the radical polyaddition: Addition polymers of phenylphosphine with 1,4-divinylbenzene or 1,4-diisopropenylbenzene and their properties

A polyaddition of phenylphosphine (PH) to 1,4-divinylbenzene (DVB) or 1,4-diisopropenylbenzene (DIPB) was carried out by radical initiations or UV irradiation at 60–80°C in toluene under a nitrogen atmosphere. The soluble polymer with higher molecular weight () was obtained in a high yield with AIBN initiator for 95 h in the presence of 5% excess of PH to DVB (monomer feed ratio [DVB]₀/[PH]₀ = 1/1.05). On the other hand, a polyaddition of PH to DIPB proceeded much slower than the case of DVB, but the high polymer was obtained in a high yield by choosing polyaddition conditions such as polyaddition temperature and initiator concentration. From ¹H-NMR, IR analyses, and phosphorus content of the polymers, it was characterized that both polymers have the alternating structure consisting of PH and DVB or DIPB units in 1 : 1 ratio. The glass transition and decomposition temperatures of both polymers under a nitrogen atmosphere were almost similar: 15–30°C and 380–385°C, respectively; but, the polymers were oxidized by heating under an atmosphere of air. The polymers had a self-extinguishing property and the polymer blend of the flammable polymers such as polystyrene and polyethylene with the phosphorus-containing polymers exhibited an excellent flame resistance. © 1994 John Wiley & Sons, Inc.     

Fully charged: Maximizing the potential of cationic polyelectrolytes in applications ranging from membranes to gene delivery through rational design

Polyelectrolytes have found utility across various applications in materials science, from electrochemical devices to biotechnology, due to their facile processing and tunable properties. Through chemistry, rational manipulation of molecular structure enables individual families of polyelectrolytes to be used in emerging advanced applications. In this perspective, we focus on cationic systems, and we describe how various structural motifs influence macromolecular properties for anion exchange membranes and gene delivery vectors. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3167–3174     

Thermally activated delayed fluorescence molecules and their new applications aside from OLEDs

Thermally activated delayed fluorescence (TADF) organic molecules feature with long-lived delayed fluorescence, because they can undergo not only efficient intersystem crossing (ISC), but also efficient reverse intersystem crossing (RISC) at room temperature. As a new type of luminescent molecules, they have exhibited successful applications in organic light emitting diodes (OLEDs). Aside from OLEDs, they are also found to have potential applications in time-resolved luminescence imaging based on long-lived fluorescence property. Meanwhile, due to their excited triplet characteristic originated from efficient ISC, they were found to be applied in triplet-triplet annihilation upconversion (TTA-UC), photodynamic therapy (PDT) and organic photocatalytic synthesis. This review briefly summarizes the characteristics and excellent photophysical properties of TADF organic compounds, then covers their applications to date aside from OLEDs based on their highly efficient ISC ability and RISC ability at room temperature.     

Current progresses in two-dimensional MXene-based framework: prospects from superficial synthesis to energy conversion and storage applications

MXenes are regarded as a type of two-dimensional (2D) inorganic material, mainly comprising a number of transition metal carbides, nitrides, or carbonitrides atomic planes. Nevertheless, the scientific community is continuously interested in exploring and structuring the engineered-based multifunctional material for numerous applications. The MXenes-based materials in this context, have emerged as highly active compounds owing to their superior surface area, substantial interlayer spacing, highly reactive surface-active sites and surface functional group, even though, recent studies have shown significant scientific and theoretical progress related to enormous prospects in MXenes, chemical nature, robust electrochemistry and high hydrophilicity of MXenes. The role of MXenes in all kinds of strategies is still in an upgrading phase for their further improvement, and is not sufficiently summarized in the literature now. To begin with this, herein, present review article is intended to critically discuss the diversity of MXenes with respect to different composition, formulation, plasmonic, complexation, and numerous geometric and morphological aspects, along with novel construction strategies to improve their surface characteristics in all aforesaid multidimensional applications. Following that, in terms of broadening the application, this review article is envisaged to endorse the use of MXenes and their hybrid configuration in a series of emerging environmental decontamination via adsorption, photodegradation, photocatalytic fuel production via hydrogen evolution, CO₂ reduction, electrocatalytic sensing, along with membrane distillation and energy storage. In addition, comprehensive information about existing obstacles and future perspectives have been addressed. Finally, an overview is succinctly summarized and discussed regarding the emerging prospects of MXenes for their potential uses in numerous research fields. At the end, it is anticipated that this review article will pave the way for the effective use of MXenes in different fields of environmental remediation, energy conversion, storage and biomedical applications as an innovative, reliable, and multifunctional material.     

Hole-phonon Scattering and Thermal Conductivity of p-type InSb from 2 to 100 K

The hole-phonon interaction contributing to the thermal conductivity of three p-type samples of InSb is analyzed between temperatures of 2 and 100 K. In addition to the phonon scattering by bound and free holes, other phonon scattering such as boundary, point defect and phonons are considered. Both relaxation rates for q≤2k _F and for q>2k _F are used for free hole-phonon scattering. The role of screening due to plasma on hole-phonon scattering is also included. The Callaway model for thermal conductivity is utilized from which an excellent fit to the experimental data is obtained over the whole temperature range. This revised version was published online in August 2006 with corrections to the Cover Date.     

Soft Phonon Modes Leading to Ultralow Thermal Conductivity and High Thermoelectric Performance in AgCuTe

Crystalline solids with intrinsically low lattice thermal conductivity (κ_L) are crucial to realizing high‐performance thermoelectric (TE) materials. Herein, we show an ultralow κ_L of 0.35 Wm^?1 K^?1 in AgCuTe, which has a remarkable TE figure‐of‐merit, zT of 1.6 at 670 K when alloyed with 10 mol % Se. First‐principles DFT calculation reveals several soft phonon modes in its room‐temperature hexagonal phase, which are also evident from low‐temperature heat‐capacity measurement. These phonon modes, dominated by Ag vibrations, soften further with temperature giving a dynamic cation disorder and driving the superionic transition. Intrinsic factors cause an ultralow κ_L in the room‐temperature hexagonal phase, while the dynamic disorder of Ag/Cu cations leads to reduced phonon frequencies and mean free paths in the high‐temperature rocksalt phase. Despite the cation disorder at elevated temperatures, the crystalline conduits of the rigid anion sublattice give a high power factor.     

Thermal expansivities ofn-hexane,n-hexanol and their mixtures over the temperature range from 303 K to 503 K at pressures up to 400 MPa

The isobaric thermal expansivities ofn-hexanol and of its binary mixtures withn-hexane have been measured in a pressure-controlled scanning calorimeter at 303 K, 353 K, 403 K, 453 K and 503 K under pressures up to 400 MPa. In both then-hexanol and its mixtures withn-hexane a regular crossing point of isotherms of thermal expansivities was observed. The value of pressure at which the crossing appeared increased with the increasing amount ofn-hexane.

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Zusammenfassung In einem druckkontrollierten Scanning-Kalorimeter wurden bei Drücken bis zu 400 MPa bei 303 K, 353 K, 403 K, 453 K und 503 K die isobare Wärmeausdehnung vonn-Hexanol und seiner binären Gemische mitn-Hexan gemessen. Sowohl bein-Hexanol als auch bei seinen Gemischen mitn-Hexan wurde ein regulärer Schnittpunkt der Isothermen der Wärmeausdehnung gefunden. Der Druck, bei dem der Schnittpunkt auftritt, steigt mit zunehmenden Gehalt ann-Hexanol.

     

Backscattered electrons from gold surface films deposited on silicon substrates: a joint experimental and computational investigation to add new potentiality to electron microscopy

This paper addresses the problem of the thickness determination of thin gold overlayers deposited on silicon bulk substrates by looking at the electron backscattering coefficient involved in scanning electron microscopy (SEM). A Monte Carlo code, used to calculate the backscattering coefficient, together with a simple experimental setup, which uses a conventional SEM, allow to determine thin film thickness (in the range 25–200 nm) with an estimated accuracy of 20%. This adds obviously new potentiality to SEM. Copyright © 2012 John Wiley & Sons, Ltd.     

Generation of alkyl radicals from alkylsilyl peroxides and their applications to C-N or C-O bond formations

This article describes a novel method for the generation of alkyl radicals from alkylsilyl peroxides and their applications to the Cu-catalyzed mono-N-alkylation of amides or arylamines, and to the O-alkylation of carboxylic acids. The use of alkylsilyl peroxides as alkyl radical sources includes the following synthetic advantages: i) various alkylsilyl peroxides can be readily synthesized from the corresponding alcohols and be stored at bench, and ii) a variety of alkyl radicals can be generated efficiently under mild conditions.     

Comparative evolved gas analytical and structural study on trans-diammine-bis(nitrito)-palladium(II) and platinum(II) by TG/DTA–MS, TG–FTIR, and single crystal X-ray diffraction

Detailed study on identification and thermal decomposition of solid title compounds 1 and 2 crystallized from the used aqueous ammonia solutions of Pd(NH₃)₂(NO₂)₂ and Pt(NH₃)₂(NO₂)₂, has been carried out. Beyond the composition of complexes 1 and 2, their trans square planar configuration have already been recognized by reference IR spectra and powder XRD patterns, nevertheless their exact molecular and crystal structure as of trans-Pd(NH₃)₂(NO₂)₂ (1, Pd-NN) and trans-Pt(NH₃)₂(NO₂)₂ (2, Pt-NN) has been determined by single crystal X-ray diffraction (R = 0.0515 and 0.0341), respectively. Despite their compositional and configuration analogy, they crystallize in different crystal systems and space groups. The crystals of 1 (Pd-NN) are triclinic (space group No. 2, P-1, a = 5.003(1) Å, b = 5.419(1) Å, c = 6.317(1) Å, α = 91.34(2)°, β = 111.890(10)°, γ = 100.380(10)°), while those of 2 (Pt-NN) are monoclinic (space group No. 5, C2, a = 7.4235(16) Å, b = 9.130(2) Å, c = 4.4847(10) Å, β = 99.405(7)°).The pyrolytic processes of 1 and 2 (which might be sensitive to shock and heat) have been followed by simultaneous thermogravimetric and differential thermal analysis (TG/DTA), while the evolved gaseous species have been traced in situ by online coupled TG/DTA–EGA–MS and TG–EGA–FTIR instruments in He and air. Pd and Pt powders, forming as final solid products in single step, are captured and checked by TG and XRD. Whilst the unified evolved gas analyses report evolution of N₂, H₂O, NH₃, N₂O, NO, and NO₂ gases as gaseous product components in the exothermic decomposition of both trans-Pd(NH₃)₂(NO₂)₂ (1) and trans-Pt(NH₃)₂(NO₂)₂ (2) starting from ca. 230 and 220 °C, in sealed crucibles with a pinhole on the top, respectively.