Differential Scanning Calorimetry Traces Research Articles

Effects of rare-earth element Y content on the microstructure and properties of quinary Al–Ni–Zr–Co–Y high entropy metallic glasses

A series of quinary (Al1/4Ni1/4Zr1/4Co1/4)100-xYx (x = 16–28 at.%) high entropy metallic glass ribbons were successfully fabricated through the high-speed single roller melt-spinning method. The effects of rare-earth element yttrium content on the microstructure and performances of alloy ribbons were systematically investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), heat treatment, transmission electronic microscopy (TEM), atomic force microscopy (AFM) and electrochemical experiments. The microhardness of metallic ribbons was measured by Vickers hardness tester. Results show that the microstructure of the as-quenched alloy ribbons maintain the glassy state and the average microhardness value of each specimen can reach 488 HV0.1 or above. The surface morphologies of the as-spun ribbon samples exhibit the smooth surface with small roughness value of Ra = 0.115–0.150 nm. In the meantime, with the increase of Y content, the glass transition temperature can be detected in the DSC traces when Y content is over 22 at.%, and the crystallization onset temperature shifts to the lower temperature region, suggesting that the thermal stability of amorphous state in Al–Ni–Zr–Co–Y alloy ribbons has been weakened. The (Al1/4Ni1/4Zr1/4Co1/4)84Y16 alloy ribbons own the highest crystallization onset temperature (∼742 K). Adding appropriate yttrium element can enlarge the super-cooled liquid region and improve the glass-forming ability. In 3.5 wt% NaCl solution, the prepared alloy ribbons can maintain smaller corrosion current densities (∼10−8 A cm−2) than traditional Al-based amorphous alloys, 6061 Al alloy and other common structural steels. The X-ray photoelectron spectrometer results indicate that the passive film of equiatomic alloy ribbons is rich in oxides of Al, Zr, Co, and Y elements, which has excellent resistance to chloride ion attack. On the basis of all experimental results, (Al1/4Ni1/4Zr1/4Co1/4)84Y16 alloy ribbons can optimally combine outstanding corrosion resistance, superior thermal stability, and acceptable microhardness. The above research results lay a solid foundation for the composition development of high-performance high entropy metallic glasses.

Effect of anisotropic deformation on the differential scanning calorimetry response of polymer glasses

AbstractLarge anisotropic deformation affects the physical state of a polymer glass, where the changes in the state of material are revealed by performing a differential scanning calorimetry (DSC) experiment. Previously, the deformation was applied to polymers well below their glass transition temperatures, and it was found that uniaxial compressive loading–unloading resulted in a broad exothermic peak on the DSC trace. Here we report on the effect on the subsequent DSC response of a deformation experiment performed in uniaxial extension on a ductile 50:50 co‐polymer poly(BMA‐co‐MMA) (PBMA/MMA). The deformation of up to 80% strain was applied at Tg − 30°C and Tg − 40°C, that is, closer to Tg than in the previous work. Unlike in the well below Tg deformation case, the DSC trace contains an endothermic peak followed by an exothermic peak. The magnitude of the endothermic peak as well as the asymptotic glassy heat capacity increase with the amount of mechanical work performed during the deformation cycle.

Soft Magnetic Properties and Electromagnetic Shielding Performance of Fe40Ni40B20 Microfibers

AbstractFe40Ni40B20 metallic glass is a key material among the many amorphous systems investigated thus far, owing to its high strength and appealing soft magnetic properties that make it suitable for use as transformer cores. In this study, Fe40Ni40B20 microfibers are fabricated down to 5 µm diameter. Three different melt–spinning wheel velocities: ≈51 m s−1, ≈59 m s−1, and ≈63 m s−1 (MG1, MG2, MG3) are used. Their fully amorphous structure is confirmed using X–ray diffraction, and differential scanning calorimetry (DSC) traces reveal a larger relaxation profile for the higher–quenched microfiber. Vibrating sample magnetometer measurements showed a higher saturation magnetization of 136 emug−1 for annealed metallic glass microfibers with a wheel velocity of 59.66 ms−1. Cylindrical magnetic field shields are obtained by aligning and wrapping the fibers around a cast. The observed anisotropic static field shielding behavior is in accordance with the microfibers' anisotropic nature. Composite samples are also produced by embedding the microfibers in an epoxy matrix to investigate their electromagnetic properties at GHz frequencies. Inclusion of the microfibers increase the composite's attenuation constant by 20 to 25 times, making it an ideal candidate for applications in the communications frequency range.

Assessment of DPPC Liposome Disruption by Embedded Tocopheryl Malonate

In this study, the effect of α-tocopheryl malonate (TM) on physical and structural properties of DPPC liposomes was investigated using ANS fluorescence, DPH, and TMA–DPH anisotropy fluorescence and differential scanning calorimetry (DSC) methods. The presence of embedded TM in DPPC liposomes caused alteration in its phase transition temperatures, structural order, dynamics, and hydration of head groups increasingly with growing TM concentration. The ANS fluorescence results demonstrated that increasing TM presence in the DPPC gel phase due to interrupted membrane structure caused the formation of new binding sites. Temperature investigations in the range of 20 °C to 60 °C showed that increasing temperature rises ANS fluorescence which reaches local and global maxima at 36 °C and 42 °C, respectively. The rising TM concentration at the phase transition temperature of DPPC led to the lowering of ANS fluorescence, indicating a decreased binding of ANS. Simultaneously, during heating, a roughly 10-nm shift of ANS emission maximum was observed. The results indicated that in the fluid phase, the observed quenching appears as a result of increasing accessibility of water molecules into ANS in this region. The DPH results indicated that in the gel phase presence of TM introduced disorder in the hydrophobic acyl chain region led to its fluidization. The TMA–DPH results indicated an increasing disorder in the interface region and an increasing hydration of head group atoms at the surface of the membrane. The increasing concentration of TM results in the formation of multicomponent DSC traces, suggesting the formation of another structural phase. The applied methods proved that the incorporation of TM into DPPC membrane results in the interaction of malonate moiety with DPPC head group atoms in the interphase layer and induces the interruption in the membrane packing order, leading to its structural changes. The presented results show that TM presence could regulate the membrane properties, thus it may indicate one of the possible mechanisms responsible for the effective disruption of cell membranes by TM. The knowledge of molecular mechanism how TM interacts with the membrane will help to elucidate its possible pharmacological activity.

Crystallization kinetics of Hf28Be18Ti17Zr17Cu7.5Ni12.5 high-entropy bulk metallic glass

Crystallization kinetics of Hf28Be18Ti17Zr17Cu7.5Ni12.5 high-entropy bulk metallic glass (HE-BMG) in the non-isothermal and isothermal conditions were investigated by differential scanning calorimetry (DSC). In non-isothermal crystallization condition, DSC traces exhibited three crystallization processes. The apparent activation energies of peak crystallization temperatures were calculated by Kissinger methods and found to be Ep1 > Ep2 > Ep3. The dependence of local activation energy on crystallized volume fraction was summarized by the Kissinger-Akahira-Sunose (KAS) method. The non-isothermal crystallization reaction was described mathematically using the Šesták-Berggren model. In the isothermal crystallization condition, with the increase of annealing temperature, the incubation time and crystallization time become shorter and the crystallization peak becomes higher. All Avrami indices were less than 2.5, indicating that crystallization of glassy alloy is dominated by a diffusion-controlled three-dimensional growth with a decreasing nucleation rate.

Sensitive temperature-dependent phase resolution of polyethylene-clay nanocomposites

With the help of spectroscopic and differential scanning calorimetry (DSC) techniques, we have studied conformational and phase reorganizations as function of temperature in intercalated polymer-clay nanocomposites based on low-, middle-, and high-density polyethylene (PE) matrices. We show that Raman spectroscopy is sensitive to structural changes appearing during heating at much lower temperatures (about 47 °C) in comparison to DSC measurements. In fact, in the melting region where DSC traces show endotherms, Raman spectra reveal dramatic changes in the phase and conformational compositions of PE and PE-matrices within PE-clay nanocomposites. Noteworthy, the structural reorganization pathway, through which the semicrystalline nanocomposites transform into a melt state, depends primarily on the PE density and weakly on the filler (nanoclay). Moreover, the temperature-dependent crystallinity degree and the total amount of trans-conformers of the PE system are determined, and the evidence for the formation of intermediate crystal-like phase during heating is shown.

Mn\(_{55-x}\)Co\(_x\)Bi\(_{45}\) Melt Spun Ribbons: Microstructures and Magnetic Properties

In this paper, we present the effect of Cobalt (Co) addition on the crystallization, microstructures and magnetic properties of Mn55-xCoxBi45 (x = 0, 5, 10, 20) melt – spun ribbons. The ribbons were prepared by the melt-spinning techique and subsequent anneal at 280 oC for 5 h. The investigations by using X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC) traces as well the Vibration Sample Magnetometer (VSM) measurements result in the optimal content of Co added to the MnBi system is arounf 5 %at. The larger Co content causes the eutectic Mn-Co formation which restricts the reaction between Mn and Bi to form MnBi ferromagnetic phase responsible for ribbons’ performance the saturation magnetization Ms. The maximum saturation magnetization Ms of 65emu/g and the coercivity iHc of 4.7 kOe was achived for the ribbon of Mn50Co5Bi45. The effect of Co content on the microstructures and magnetic properties of Mn55-xCoxBi45 melt – spun ribbons will be discussed in detail.

Green Stereoregular Polymerization of Poly(methyl methacrylate)s Through Vesicular Catalysis

Green Stereoregular Polymerization of Poly(methyl methacrylate)s Through Vesicular Catalysis

Probing boron thermite energy release at rapid heating rates

Boron (B) is a promising fuel for energetic materials due to its high gravimetric and volumetric energy density. The enhanced ignition and combustion of B in a thermite with CuO and Bi2O3 and their mixtures compared to single metal oxides was recently demonstrated. In this study, we compared the early-time reaction B-thermite mixtures using the laser-induced air shock from energetic materials (LASEM) technique, bomb calorimetry, and differential scanning calorimetry (DSC). The application of LASEM to B/metal oxide samples has enabled the quantification of their microsecond-timescale energy release and excitation temperatures under extremely high heating rates, and the elucidation of their chemistry differences on both the microsecond and millisecond timescales. The time to peak combustion determined by LASEM follows the trend B/CuO/Bi2O3 < B/Bi2O3 < B/CuO. The energy release measured by LASEM on both the microsecond- (laser-induced shock velocities) and millisecond- (combustion reactions) timescales was the highest for B/CuO/Bi2O3. These relative measurements are in agreement with the heat of reaction as measured by the bomb calorimetry and onset of DSC traces, which follow similar ordering and suggests that enhanced ignition of these composites is contributing to the early-time energy release. Finally, our morphology characterization revealed that CuO has a strong affinity for both B and Bi2O3; we suggest the CuO pulls the Bi2O3 into closer contact with the B particles in the binary metal oxide mixture, resulting in a synergetic enhancement effect compared to the single metal oxide.

Comparing the interaction of the antibiotic levofloxacin with zwitterionic and anionic membranes: Calorimetry, fluorescence, and spin label studies

The present work compares the interaction of the antibiotic levofloxacin (LVX) with zwitterionic and anionic liposomes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (DPPG), respectively. By using differential scanning calorimetry (DSC), and with spin labels incorporated into liposomes at two different depths of the bilayers, we investigated the changes induced on the membrane by increasing concentrations of LVX. Further information was obtained using intrinsic LVX fluorescence. Under the conditions used here, all techniques evinced that LVX has little affinity for DPPC zwitterionic membrane. Opposite to that, LVX exhibits a considerable affinity for anionic bilayers, with membrane partition constants Kp = (3.3 ± 0.5) × 102 and (4.5 ± 0.3) × 102, for gel and fluid DPPG membranes, respectively. On binding to DPPG, LVX seems to give rise to the coexistence of LVX -rich and -poor domains on DPPG membranes, as detected by DSC. At the highest LVX concentration used (20 mol%), DSC trace shows an increase in the cooperativity of DPPG gel-fluid transition, also detected by spin labels as an increase in the bilayer packing. Moreover, LVX does not induce pore formation in either DPPG or POPG vesicles. Considering the possible relevance of LVX-membrane interaction for the biological and toxicological action of the antibiotic, the findings discussed here certainly contribute to a better understanding of its action, and the planning of new drugs.

Theoretical and Experimental Parameters of the Structure and Crystallization Kinetics of Melt-Quenched As30Te64Ga6 Glassy Alloy

The present framework reports the structural, fundamental parameters, and crystallization kinetics of the melt-quenched As30Te64Ga6 chalcogenide glass. The energy dispersive X-ray analysis of the As30Te64Ga6 glassy system reveals that the constituent element ratio of the investigated bulk sample agrees with the nominal composition. Also, X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC) were used to characterize structural properties, and crystallization kinetics; respectively. Four characteristic temperatures related to various phenomena are observed in the investigated DSC traces. The first one is $$T_{g}$$ that corresponds to the glass transition temperature. The second one is ( $$T_{c1}$$ , and $$T_{c2}$$ ) that corresponds to the onset of the double crystallization temperatures. The third one ( $$T_{P1}$$ , and $$T_{P2}$$ ) identifies the double peak crystallization temperatures. The last characteristic temperature ( $$T_{m}$$ ) is the melting point. The XRD analysis indicates the amorphous structure of the as-prepared glassy alloy, while the annealed samples are polycrystalline. The crystallization kinetics of the As30Te64Ga6 bulk are studied under non-isothermal conditions. In addition, the values of various kinetic parameters such as the glass transition activation energy, weight stability standard, and Avrami exponent were determined. The activation energy of the crystallization process for As30Te64Ga6 glass alloy was calculated using classical methods. The results indicated that the rate of crystallization is related to thermal stability and the ability to form glass. Kinetic parameters have been estimated with some conventional methods and found to be dependent on heating rates (β).

Effect of bis(naphthyl-imide) and polyoxyethylene units on thermal stability and Tg values of binarily cured epoxy resins

Diglycidyl ethers of N,N'-bis(5-hydroxy-1-naphthyl)pyromellitimide (BNIDE) and polyethylene glycol (PEGDE) were binarily cured by N,N'-bis(5-amino-1-naphthyl)pyromellitimide (BNIDA) curing agent. Three homogenized mixtures of BNIDE and PEGDE resins with different mole ratios (75/25, 50/50 and 25/75) were isothermally reacted with the stoichiometric amounts of the curing agent. For comparison purposes, each diglycidyl ether was also cured separately with the same condition. The exothermic phase transitions associated with the curing processes were specified in the dynamic differential scanning calorimetry (DSC) traces of BNIDEBNIDA, BNIDE:PEGDEBNIDA, and PEGDEBNIDA mixtures. The completion of the curing processes was confirmed using Fourier transform-infra red (FT-IR) spectra and DSC traces of the isothermally cured resins. Effect of bis(naphthyl-imide) and polyoxyethylene units on thermal stability and Tg value of binarily cured epoxy resins was investigated by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Both thermal stability and Tg value of the imide-epoxy thermoset films significantly increases with BNIDE resin. Instead, when PEGDE resin was cured by BNIDA, the prepared films showed more flexibility and pliability. These important characteristics were appropriately balanced by employing three binary mixtures of BNIDE and PEGDE resins.

Non-isothermal crystallization kinetics of an intermetallic CoSn phase

Herein, the crystallization kinetics of the intermetallic CoSn phase, nucleated and grown in the microstructure of a binary CoSn alloy, have been reported. Differential scanning calorimetry traces under non-isothermal conditions were obtained and used to extract the activation energy () for the crystallization of the CoSn phase at various heating rates. The obtained values of were validated by the application of several isoconversion methods. The minimum value of was 1000 kJ mol−1, which occurred at 853 K. The observed behavior of showed a strong temperature dependence, wherein it decreased with increasing temperature. This suggests that the rate constant for the crystallization of the CoSn phase is determined by the rates of two processes—nucleation and diffusion. The precise description of the crystallization process for the CoSn phase reveal that the reaction mechanism of this phase is following the first-order reaction.

Ultrathin Two Dimensional (2D) Supramolecular Assembly and Anisotropic Conductivity of an Amphiphilic Naphthalene-Diimide.

Two-dimensional (2D)-supramolecular assemblies of π-conjugated chromophores are relatively less common compared to a large number of recent examples on their low dimensional (0D or 1D) assemblies or 3D architectures. This article reports a rational design for the 2D supramolecular assembly of an amphiphilic core-substituted naphthalene-diimide derivative (cNDI-1). The building block contains a naphthalene-diimide (NDI) chromophore, symmetrically substituted with two dodecyl chains from the aromatic core while the imide positions are functionalized with two hydrophilic wedges containing oligo-oxyethylene chains. In water, it exhibits entropically favorable self-assembly with a critical aggregation concentration of 1.5 × 10-5 M and a lower critical solution temperature of 55 °C. The UV/vis absorption spectrum in water shows bathochromically shifted absorption bands compared to that of the monomeric dye in THF, indicating offset π-stacking among the NDI chromophores. C-H symmetric and asymmetric stretching frequencies in the FT-IR spectrum support the presence of organized hydrocarbon chains in trans conformation in the self-assembled state, similar to that in the crystalline n-alkanes, which is further supported by studying the general polarization (GP) values of a noncovalently entrapped Laurdan dye. The atomic force microscopy (AFM) image shows the formation of ultrathin (height < 2.0 nm) ribbons for the spontaneously assembled sample which eventually produces a large-area 2D nanosheet by the lateral organization. The powder X-ray diffraction pattern of the drop-casted film, prepared from the preformed aggregates, reveals sharp peaks that indicate a crystalline lamellar packing along the direction of the 2D growth. Differential scanning calorimetry trace shows the melting of the crystalline alkyl chain domain at T > 75 °C, which destroys the 2D assembly. Local-scale photoconductivity of the ordered 2D assembly, studied by the flash-photolysis time-resolved microwave conductivity (FP-TRMC) technique, reveals an anisotropic conductivity with ∼3 times larger conductivity along the parallel direction compared to that along the perpendicular one.

Thermal stability and dynamic mechanical thermal analysis of epoxy thermosets possessing N,N′-disubstituted pyromellitimide units

In this work, three epoxy resins including diglycidyl ethers of N,N′-bis(2-hydroxyethyl)pyromellitimide (DIDGE), bisphenol-A (BADGE), and polyethylene glycol (PEDGE) were isothermally cured by an amine curing agent possessing N,N′-disubstituted pyromellitimide units (denoted by DIDAM). DIDGE resin was synthesized from the reaction of N,N′-bis(2-hydroxyethyl)pyromellitimide with an excess of epichlorohydrin. Also, DIDAM curing agent was prepared from the reaction of pyromellitic dianhydride with an excess of ethylene diamine. Completion of the isothermal curing processes was approved by both Fourier transform-infrared spectroscopy and non-isothermal differential scanning calorimetry (DSC). The DSC traces showed only the phase transitions related to the thermal degradation of the resulting thermosets. According to the thermogravimetric analyses, the DIDGE/DIDAM thermoset showed higher thermal stability at temperatures above 425 °C than the other two thermosets. While BADGE/DIDAM and PEDGE/DIDAM thermosets showed about 70% weight loss in the thermal range of 400–850 °C, DIDGE/DIDAM thermoset was encountered with only about 40% weight loss. The glass transition temperatures (Tg ) of the resulting thermosets were determined using tan δ vs temperature plots obtained from dynamic mechanical thermal analysis. The Tg values of BADGE/DIDAM, DIDGE/DIDAM, and PEDGE/DIDAM thermosets were found to be 211 °C, 189 °C, and 81 °C, respectively.

Tocopheryl Succinate-Induced Structural Changes in DPPC Liposomes: DSC and ANS Fluorescence Studies.

Recent studies show that alpha-tocopheryl succinate (TS) exhibits selective toxicity against cancer cells. In this study, we investigated the effect of TS’s presence on the physico-chemical and structural properties of DPPC liposomes using fluorescence parameters (intensity, lifetime, and position of emission maximum) of 1-anilino-8-naphtalene sulphonate (ANS), differential scanning calorimetry (DSC) and zeta potential methods. Increasing the TS presence in the DPPC gel phase produced ANS fluorescence enhancement with a hypsochromic shift of the maximum. The zeta potential measurements show an increase in the negative surface charge and confirmed that this process is connected with the hydrophobic properties of dye, which becomes located deeper into the interphase region with a progressing membrane disorder. Temperature dependence studies showed that an increase in temperature increases the ANS fluorescence and shifts the ANS maximum emission from 464 to 475 nm indicating a shift from hydrophobic to a more aqueous environment. In the liquid crystalline phase, the quenching of ANS fluorescence occurs due to the increased accessibility of water to the ANS located in the glycerol region. The DSC results revealed that increasing the presence of TS led to the formation of multicomponent DSC traces, indicating the formation of intermediate structures during melting. The present results confirmed that TS embedded into the DPPC membrane led to its disruption due to destabilisation of its structure, which confirmed the measured biophysical parameters of the membrane.

Effect of Surface Chemistry on the Glass-Transition Dynamics of Poly(phenyl methyl siloxane) Confined in Alumina Nanopores.

Broadband dielectric spectroscopy (BDS) and differential scanning calorimetry (DSC) are combined to study the effect of changes in the surface chemistry on the segmental dynamics of glass-forming polymer, poly(methylphenylsiloxane) (PMPS), confined in anodized aluminum oxide (AAO) nanopores. Measurements were carried for native and silanized nanopores of the same pore sizes. Nanopore surfaces are modified with the use of two silanizing agents, chlorotrimethylsilane (ClTMS) and (3-aminopropyl)trimethoxysilane (APTMOS), of much different properties. The results of the dielectric studies have demonstrated that for the studied polymer located in 55 nm pores, changes in the surface chemistry and thermal treatment allows the confinement effect seen in temperature evolution of the segmental relaxation time, τα(T) to be removed. The bulk-like evolution of the segmental relaxation time can also be restored upon long-time annealing. Interestingly, the time scale of such equilibration process was found to be independent of the surface conditions. The calorimetric measurements reveal the presence of two glass-transition events in DSC thermograms of all considered systems, implying that the changes in the interfacial interactions introduced by silanization are not strong enough to inhibit the formation of the interfacial layer. Although DSC traces confirmed the two-glass-transition scenario, there is no clear evidence that vitrification of the interfacial layer affects τα(T) for nanopore-confined polymer.

EFFECT OF Se ADDITIVE ON THE STRUCTURE, PRE-CRYSTALLIZATION CRITERIA AND CRYSTALLIZATION KINETIC PARAMETERS IN GLASSY MELT-QUENCHED As-S ALLOY

The present framework is consecrated to studying structural parameters, pre-crystallization criteria and crystallization kinetics by non-isothermal and iso-conversional methods for melt-quenched As40S60-xSex glassy alloys, with (x=0, 15, 30, 45 and 60 at. %). Energy dispersive x-ray analysis of the As40S60-xSex glassy system appears that the constituent element ratio of the studied samples have been agreed with the nominal compositions. Likewise, Differential Scanning Calorimetry (DSC) and x-ray diffraction (XRD) has been utilized to depict the thermal and structural properties, respectively. Four characteristic temperatures linked to several phenomena are obviously noticed in the studied DSC traces. The first one is Tg that harmonizes with the glass transition temperature. The second one is Tc that harmonizes with the onset of the crystallization temperature. The third one, T p corresponds to the peak crystallization temperature. The last characteristic temperature, T p is the melting point. The XRD analysis signalizes to the amorphous structure of the as-prepared glassy alloys. The crystallization kinetics of the powdered of As40S60-xSex, have been investigated under non-isothermal and iso-conversional conditions. Besides, the values of diverse kinetic parameters such as the activation energy of glass transition, the weight stability criterion, and Avrami exponent, have been computed. The activation energies of the crystallization process of the As40S60-xSex glassy alloys were determined by means of classical and also by the iso-conversional methods. The results referred that the rate of crystallization is linked to the thermal stability and glass-forming ability. The kinetic parameters that computed via some classical and isoconversional methods, were found to be dependent on the change of Se content.

Inclusion of the Phytoalexin trans-Resveratrol in Native Cyclodextrins: A Thermal, Spectroscopic, and X-Ray Structural Study.

The aim of the study was to determine the feasibility of complexation between the antioxidant trans-resveratrol (RSV) and underivatized cyclodextrins (CDs) using a variety of preparative methods, including physical mixing, kneading, microwave irradiation, co-evaporation, and co-precipitation techniques. Products were characterized using differential scanning calorimetry (DSC), simultaneous thermogravimetric/DSC analysis (TGA/DSC), Fourier transform infrared (FT-IR) spectroscopy, and powder X-ray diffraction (PXRD). With α-CD and RSV, sample amorphization was revealed by PXRD and FT-IR, but no definitive inclusion complexation was evident. Similar results were obtained in attempts to complex RSV with β-CD. However, complex formation between γ-CD and RSV was evident from observation of an endo-/exothermic effect appearing in the DSC trace of the product from kneading and was further corroborated by FT-IR and PXRD methods. The latter technique indicated complexation unequivocally as the diffraction peak profile for the product matched that for known isostructural γ-CD complexes. Single crystal X-ray analysis followed, confirming the predicted complex between γ-CD and RSV. A combination of 1H NMR and TGA data yielded the complex formula (γ-CD)3·(RSV)4·(H2O)62. However, severe disorder of the RSV molecules prevented their modeling. In contrast, our previous studies of the inclusion of RSV in methylated CDs yielded crystals with only minor guest disorder.

Nanometer Ammonium Perchlorate and Ammonium Nitrate Prepared with 2D Network Structure via Rapid Freezing Technology.

Nanometer (nano) ammonium perchlorate (AP) and ammonium nitrate (AN) were prepared with 2D network structures by the ultra-low temperature spray method. Scanning electron microscopy (SEM), X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis/infrared spectrometry (TG-IR) were employed to probe the micron structure, crystal phase, and thermal decomposition of nano AP and nano AN. SEM images revealed that the sizes of nano AP and AN were in the nanometer scale (<100 nm) in one dimension. XRD patterns showed that the crystal phases of nano AP and AN were in accordance with those of raw AP and raw AN, respectively. DSC traces indicated that the thermal decomposition process of AP depended on its particle size, while the thermolysis of AN was independent of the particle size of AN. TG-IR analyses illustrated that the decomposition products of nano AP were NO2, N2O, HCl and H2O, with a small amount of NOCl, and the main decomposition products of nano AN were N2O and H2O, with a small amount of NH3. The results of mechanical sensitivity tests indicated that nano AP was more sensitive than raw AP and both nano AN and raw AN were very insensitive to impact and friction stimuli.