Stepwise Heating Research Articles

Feldspar 40Ar/39Ar dating of ICDP PALEOVAN cores

Volcaniclastic fall deposits in ICDP drilling cores from Lake Van, Turkey, contain sodium-rich sanidine and calcium-rich anorthoclase, which both comprise a variety of textural zoning and inclusions. An age model records the lake’s history and is based on climate-stratigraphic correlations, tephrostratigraphy, paleomagnetics, and earlier 40Ar/39Ar analyses (Stockhecke et al., 2014b). Results from total fusion and stepwise heating 40Ar/39Ar analyses presented in this study allow for the comparison of radiometric constraints from texturally diversified feldspar and the multi-proxy lacustrine age model and vice versa. This study has investigated several grain-size fractions of feldspar from 13 volcaniclastic units. The feldspars show textural features that are visible in cathodoluminescence (CL) or back-scattered electron (BSE) images and can be subdivided into three dominant zoning-types: (1) compositional zoning, (2) round pseudo-oscillatory zoning and (3) resorbed and patchy zoning (Ginibre et al., 2004). Round pseudo-oscillatory zoning records a sensitive alternation of Fe and Ca that also reflects resorption processes. This is only visible in CL images. Compositional zoning reflects anticorrelated anorthite and orthoclase contents and is visible in BSE.Eleven inverse isochron ages from total fusion and three from stepwise heating analyses fit the age model. Four experiments resulted in older inverse isochron ages that do not concur with the model within 2σ uncertainties and that deviate from 1ka to 17ka minimum. C- and R-type zoning are interpreted as representing growth in magma chamber cupolas, as wall mushes, or in narrow conduits. Persistent compositions of PO-type crystals and abundant surfaces recording dissolution features correspond to formation within a magma chamber. C-type zoning and R-type zoning have revealed an irregular incorporation of melt and fluid inclusions. These two types of zoning in feldspar are interpreted as preferentially contributing either heterogeneously distributed excess 40Ar or inherited 40Ar to the deviating 40Ar/39Ar ages that are discussed in this study.

Proton conductive cross-linked benzoxazine-benzimidazole copolymers as novel porous substrates for reinforced pore-filling membranes in fuel cells operating at high temperatures

Proton conductive porous substrates consisting of cross-linked benzoxazine-benzimidazole copolymers are developed for practical application of reinforced pore-filling membranes in polymer electrolyte membrane fuel cells operating at high-temperatures (>100°C) and low relative humidity (<50% RH) conditions. The porous proton conductive substrates are prepared by casting solution mixtures of sodium 3-(4-sulfonatophenyl-3,4-dihydro-2H-1,3 benzoxazine-6-sulfonate (pS) and poly[2,2′-(m-phenylene-5,5′-bibenzimidazole] (PBI) with dibutyl phthalate (DBP) as a porogen, followed by subsequent stepwise heating to 220°C and extraction of DBP from the P(pS-co-BI) films. The resulting porous substrates are found to have mechanically robust cross-linked structures, tunable hydrophilicity, and proton conductivity. A pore-filling membrane is prepared by impregnating the porous substrate with sulfonated poly(arylene ether sulfone) having the degree of sulfonation of 70mol%. The pore-filling membrane exhibits much improved dimensional stability and mechanical strength compared to the linear sulfonated poly(arylene ether sulfone) membrane and its proton conductivity and cell performance are found to be superior to the pore-filling membrane prepared using the porous substrate based on cross-linked benzoxazine-benzimidazole copolymers without any proton conductive acid groups.

Thermal Decomposition Kinetics of Wood and Bark and Their Torrefied Products

The pyrolysis kinetics of Norway spruce, its bark, and their torrefied products was studied. Thermogravimetry (TGA) was employed with linear and stepwise heating programs. Altogether 36 TGA experiments were evaluated simultaneously by the method of least-squares. Part of the kinetic parameters could be assumed common for the studied samples without a considerable worsening of the fit quality. This process results in better defined parameters and emphasizes the similarities between the studied materials. Three pseudocomponents were assumed. Two of them were described by distributed activation energy models (DAEM), while a simpler kinetics was assumed for the pyrolysis of the cellulose content of the samples. The pyrolysis kinetics of the wood and the torrefied wood showed remarkable similarities to the bark and torrefied bark, though essential differences were also observed.

Hydrate Dissociation Equilibrium Conditions for Carbon Dioxide + Tetrahydrofuran

Hydrate equilibrium conditions (vapor + hydrate + liquid water + liquid tetrahydrofuran, THF) formed from carbon dioxide in aqueous solutions of THF is determined using a stepwise heating method under isochoric conditions in this work. THF is reported to form an SII hydrate. Hydrate phase equilibrium conditions are measured under the conditions of the THF mass concentration range of 0.0726–0.2503 and pressure range of 0.10–1.87 MPa. The experimental results present that the equilibrium pressures of the experimental systems of carbon dioxide + THF + H2O are obviously lower than that of the carbon dioxide + H2O system under test conditions. Furthermore, the experimental results also indicate that the carbon dioxide hydrate formation pressure decreased more apparently with more additives of THF.

Spin-Trapping Analysis of Thermal Degradation Reaction of Poly(butylene terephthalate)

Poly(butylene terephthalate) (PBT), and its oligomer, were doped with the spin-trapping reagent, 2-methyl-2-nitrosopropane (MNP), by a solution-casting method in order to detect the short-lived radical intermediates during thermal degradation. In the case of PBT, two types of spin adduct were observed by electron spin resonance (ESR) spectroscopy upon stepwise heating from room temperature to 200 °C and during annealing at 130 °C; the ESR spectrum exhibited an isotropic three-line signal, with a hyperfine coupling constant (hfcc) aN ≈ 0.8 mT, as well as an anisotropic component. These adducts were present on the order of 10–5 mol/L. The isotropic component was assigned to arise uniquely from the benzoyl radical, •CO-ϕ. The anisotropic component was carefully investigated by ESR spectroscopy and high-performance liquid chromatography–electrospray ionization–mass spectrometry (HPLC-ESI-MS), using low-molecular-weight model compounds such as n-butyl benzoate (BB), di-n-butyl terephthalate (DBT), and deuterat...

Hydrous species in eclogitic omphacite: Implication for metamorphic dehydration during exhumation

Water contents were analyzed by infrared spectroscopy for structural hydroxyl in randomly oriented cuboids and doubly polished wafers of single crystal omphacite from an ultrahigh-pressure eclogite in the Dabie orogen. The results are quantitatively compared with bulk water contents measured by the TC/EA-MS continuous flow technique. This enables recognition of various hydrous species in omphacite and their bearings on metamorphic dehydration during continental subduction. The two cuboids yield constant maximal structural water contents of ∼378ppm (H2O wt.) using the omphacite-specific infrared absorption coefficient, which are much lower than the bulk water contents of ∼1496ppm. The excessive water is contributed by the presence of other hydrous species in the form of hydrous mineral inclusions, hydrous symplectite and submicron fluid inclusions. Since the hydrous mineral and/or fluid inclusions may be captured at different metamorphic stages during subduction and exhumation of continental crust and the hydrous symplectite is the secondary rather than the primary, it is suggested that the bulk water contents represent a mixing of various hydrous species with distinct origins. In this regard, it is critical to examine whether water in these secondary hydrous species is of internal origin; if not, it has nothing to do with the transport capacity of water in deeply subducted crustal rocks. Upon stepwise heating up to 700°C, omphacite exhibits a gradual decrease in bulk water contents but an increase in δD values, indicating the preferential loss of D-depleted hydrous species as a whole due to the decompressional dehydration of UHP metamorphic rocks during exhumation. Therefore, the D-depleted hydrous species may be dominated in the hydrous symplectite and inclusion water.

From supernova to Solar System: Few years only; first Solar System components apatite and spinel determined

We show data for the very first years of our Solar System development after an interaction between undisturbed, cold interstellar dust and supernova type II explosion gases. All manual work was done in 1976–1982 as part of 3 theses works but fundamentally new data interpretation was reached within the last three years.From the CI1 meteorite Orgueil, we are able to separate 1.4 per mill of material containing supernova related noble gases He, Ne and Ar as well as P.We separate minerals using essentially density gradient centrifugation followed by stepwise heating noble gas analysis. Our procedure loses nearly no material and is in sharp contrast to the otherwise used dissolution of >99% of material to obtain single presolar grains (Anders and Zinner, 1993). Our method safeguards minerals considerably more fragile than SiC or TiC presolar grains, such as apatite, Mg-Al-spinel, graphite clusters and even apatite coated graphite clusters. We find graphite, apatite and Mg-Al-spinel containing highly anomalous noble gases. For the first time, apatite, containing anomalous Ar with an isotope ratio for 38Ar/36Ar of 0.35, twice the normal ratio, is reported. Such a ratio is produced by a 20 solar mass type II supernova in the C-O-Ne-burning shell. Unmatched pure Ne-E from 22Na measured in the same samples sets the timeframe for this interaction to a maximum of only a few years.

Influences of hybrid carbon nanofillers on structures and electrical properties of sulfonated poly(1,3,4‐oxadiazole)‐based composite films

ABSTRACTSulfonated poly(1,3,4‐oxadiazole) (sPOD)‐based composite films, including 10 wt % hybrid carbon nanofillers composed of different weight ratios of multiwalled carbon nanotube (MWCNT) and graphene sheets, were manufactured via an efficient ultrasonication‐assisted solution mixing and casting. Fourier transform infrared (FTIR) spectra of the composite films confirmed the existence of specific interactions between sPOD backbone and MWCNT or graphene sheet. Transmission electron microscopic (TEM) images of cross sections of the composite films showed that 2‐dimensional (2D) graphene sheets formed an anisotropically oriented structure in the sPOD matrix film, but they are randomly dispersed owing to the introduction of 1‐dimensional (1D) MWCNT. Accordingly, the electrical resistivity of the composite films decreased largely from ∼103 Ω cm to ∼101 Ω cm with the increment of the relative MWCNT content in hybrid carbon nanofillers due to the synergistic bridging effect. Thus, sPOD‐based composite films with 10 wt % hybrid carbon nanofillers exhibited high performance in electric heating by attaining rapid temperature responsiveness, high electric power efficiency, and stable maximum temperatures under given applied voltages. It was also revealed that the hybrid composite films were operationally stable over a long‐term stepwise electric heating experiment. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44499.

Molecular-dynamic analysis of fast heating of a mercury film on graphene

Stepwise heating of a mercury film on graphene with Stone–Wales defects and hydrogenated edges is studied by the molecular dynamics methods at 800 K. Transformation of the film into a drop and its detachment from graphene is observed at a temperature of ∼700 K. The phonon spectra determined by horizontal and vertical atomic vibrations, the mobility coefficients of Hg atoms separated in directions, the density profile and radial distribution function of mercury, the angular distribution of nearest geometrical neighbors, the stress tensor of graphene, and the roughness of a graphene sheet are calculated.

New data on the age of gold mineralization of the Lugokan ore cluster (Eastern Transbaikalia)

The Lugokan ore cluster is located in the southeastern part of Transbaikalia within the Aga–Borzya structural–formational zone of the Mongol–Okhotsk orogenic belt. The 40Ar/39Ar dating of K-bearing minerals of syngenetic to ore parageneses has been carried out applying stepwise heating technique: it has been demonstrated that the earliest gold-ore mineral associations are Au–pyrite–arsenopyrite (163 ±1.9 Ma) and Au–chalcopyrite (160 ±2 Ma). The later parageneses encompass the Au–polymetallic (156.3 ± 1.8 Ma) and Au–Bi (155.9 ± 4.5 Ma) one. By their ages and position in the general scheme of the Late Jurassic magmatism of Eastern Transbaikalia, the Lugokan’s ore cluster gold-bearing mineral associations corresponds to the time of intrusion of the Shakhtama pluton (161 Ma) and the Porphyry Complex (159–155 Ma).

Study on synthesis and the reaction mechanism of polybenzoxazine-silica nanocomposites provided from perhydropolysilazane

Abstract Polybenzoxazine/silica nanocomposites were synthesized with perhydropolysilazane (PHPS) and benzoxazines via thermal polymerization in one step. The reaction of benzoxazine's hydroxy group and PHPS was investigated via 1H nuclear magnetic resonance and Fourier transform infrared spectrometry. At low heating temperatures, benzoxazine was converted to a polymer with a N,O-acetal structure, whereas at high heating temperatures, it was converted to a polymer with a Mannich structure because high temperatures allow the polymer to react with the Si H groups of PHPS. Measurements of synthesized poly[6,6′-(1-methylethylidene)bis(3,4-dihydro-3-2H-1,3-benzoxazine)](PB-a)/silica nanocomposites showed that no reaction between PB-a hydroxy groups and PHPS Si H groups occurred because of a stepwise heating process. Measurements of synthesized poly[6,6′-(1methylethylidene)bis(3,4-dihydro-3-2H-1,3-hexylbenzoxazine)] (PB-hda)/silica nanocomposites showed that no competitive reaction between PB-hda and PHPS occurred when materials were heated at 160 °C for 1 h because PB-hda formed no hydroxy group. Conversely, at 240 °C, a competitive reaction between PB-hda and PHPS occurred, which led to the formation of Si O C linkages.

40Ar/39Ar thermochronological constraints on the retrogression and exhumation of ultra-high pressure (UHP) metamorphic rocks from Xitieshan terrane, North Qaidam, China

Paleozoic ultra-high pressure (UHP) eclogite-bearing mafic boudins are exposed in gneiss in the Xitieshan terrane, North Qaidam. Petrological and thermobarometric studies show that garnet-amphibolite and amphibolite rocks record upper amphibolite-facies and lower amphibolite-facies retrograde metamorphic conditions of 8.1–9.1kbar, 630–670°C and 5.0–7.2kbar, 530–630°C, respectively. To better constrain the timing of retrogression and exhumation, 40Ar/39Ar stepwise heating analyses have been performed on minerals that were extracted from these UHP mafic rocks and their country rocks. Amphibole yields disturbed release spectra marked by anomalously old apparent ages in low temperature steps, suggesting the presence of extraneous 40Ar. Isochron ages of ~425Ma and ~419Ma are obtained for amphibole from the garnet-amphibolite and amphibolite, respectively, which are interpreted as the best estimate for the age of amphibolite-facies retrogression during exhumation. Muscovite from the gneiss yields consistent plateau and isochron ages of ~409Ma. K-feldspar from the same gneiss yields rising staircase-shaped age spectra, which are characterized by younger apparent ages in the first steps (263–281Ma) and higher plateau ages in the last segment (294–321Ma), indicating partial diffusive loss of argon from the K-feldspar samples. Biotite from schist yields flat age spectra with a plateau age of ~397Ma that is interpreted as a cooling age. Our new 40Ar/39Ar data, together with published LA-ICPMS ages of zircon from a coesite-bearing amphibolite indicate that the Xitieshan UHP metamorphic rocks may have experienced two stages of exhumation. During the first stage, from ~95–31km depth, the UHP metamorphic rocks were exhumed with a relatively rapid velocity of ~4.0km/Myr, resulting from buoyancy forces. Subsequently, the rate of exhumation decreased gradually from ~1.1 to 0.1km/Myr between ~31–7km depth. This later gentle exhumation was probably governed by extension and/or erosion.

Kinetics of self-diffusion of water molecules in natrolite

Solid-state 1H NMR is applied to investigate the kinetics of diffusion of H2O molecules in the fibrous zeolite natrolite [Na2Al2Si3O10]∙2H2O. It is found that the stepwise heating of the zeolite in air leads to the following pattern of molecular diffusion jumps: at first they increase in number and then decrease exponentially with time. Conducting such an experiment in an aqueous medium leads to the opposite effect. The results obtained confirm our previous suggestion about the importance of interstitial defects, or overhydrated local states, in molecular diffusion.

Effect of graphite nanoparticles on CO2 hydrate phase equilibrium

Stepwise heating method was used to determine the hydrate phase equilibrium in the water containing graphite nanoparticles. The results show that, compared with deionized water at a given temperature, a significant upward shift of the formation pressure of the CO2 hydrate formed in graphite nanoparticles suspensions was observed, but the phase equilibrium curves of CO2 hydrate formation in the different graphite nanoparticles concentrations were basically consistent. In this regard, graphite nanoparticles have a negative effect on the gas hydrate formation. In addition, an improved hydrate thermodynamic model was proposed to predict the hydrate equilibrium conditions under the system of graphite nanoparticles suspensions. The results show that the maximum average deviation of pressure predicted by model is 3.39, but the minimum average deviation is 2.21. It indicates that the data of the model prediction was good agreements with the data obtained from experiments.

Silver Sintering Paste Rendering Low Porosity Joint for High Power Die Attach Application

Abstract Silver joints with ~10% porosity for die-attach have been achieved with specially engineered Ag sintering pastes, through combined pressureless sintering process plus thermal aging. The pastes developed in this work have the following advantages: 1) they can be used under pressure-less processing condition; 2) they are compatible with conventional reflow oven, resulting in a higher through-put as compared to that of stepwise heating oven; 3) they can be used under air reflow condition; 4) a highly reliable joint has been obtained as judged from the shear strength results from thermal aging and temperature cycling tests. The silver sintering pastes are versatile in bonding different metallization surface including Au, Ag and Cu. It can also be used in bonding large area (10mm × 10mm) dies. Shear test results under varied temperatures implied that the maximum service temperature of Ag sintered joints can be as high as 470 – 530 °C, depending on the shear strength pass criteria, and this is more than 250°C higher than that of high-Pb joints. Thermal aging test at 250°C for the joints generated on Ag-die/Au-DBC combination revealed that Ag continuously consolidates in the bulk phase resulting in the formation of larger pores with reduced numbers as compared to that of untreated samples. At the same time, it diffuses to sintered Ag/Au-DBC interface to form a dense Ag layer induced by alloying with Ni(Au) and Cu, which strengthened the bonding. A large bondline thickness is critical for obtaining highly reliable joints. The total porosity of the joint is found slightly decreased during the course of 3200h aging test. Temperature cycling at −55 °C to 200°C shows that the silver joints are stable for at least 1000 cycles.

Stepwise cure and properties of silicone resin for high‐ultraviolet‐transmission optical elements

ABSTRACTA new high‐ultraviolet (UV)‐transmission silicone‐resin polymeric material was prepared via curing during hydrosilylation of tetramethyltetravinylcyclotetrasiloxane with tetramethylcyclotetrasiloxane by a liquid‐surface supernatant method, using a stepwise heating program to avoid spontaneous combustion of the reaction mixture. The relationships were investigated in detail between reactive groups, cross‐linking density, mechanical and UV‐transmission properties. For this purpose, UV transmittance and dynamic mechanical properties, respectively, of the silicone resin were measured with UV–visible spectrophotometry and dynamic mechanical thermal analysis. In addition, surface roughness was evaluated with an atomic force microscope as well as an interferometer. The curing process was monitored by Fourier transform infrared spectroscopy and rotational rheometry. The cyclic silicone oils were compared with linear ones in structure and product properties. The results indicated that stepwise temperature control during curing process was particularly indispensible due to the presence of active SiH bonds, and that the silicone resin of high modulus, high UV transmittance (92.7%) and low surface‐roughness was largely homogeneous in cross‐linking points distribution. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43308.

Formation of TiO/Al2O3/C composite in thermal co-decomposition of aluminium(III) acetylacetonate and titanium(IV) oxyacetylacetonate

Thermal co-decomposition of Al(III) acetylacetonate-Ti(IV) oxyacetylacetonate mixture has been examined by using thermal gravimetry, differential scanning calorimetry and complementary analyses of evaporated products and solid residues by Fourier Transform Infrared, Raman and X-ray photoelectron spectroscopy, X-ray diffraction and scanning and transmission electron microscopy. The process is shown to differ from thermal decompositions of single acetylacetonates. Linear heating of the mixture allows predominant sublimation and minor degradation of Al(III) acetylacetonate along with extensive degradation of Ti(IV) oxyacetylacetonate to TiO2. Stepwise heating results in sublimation of one half of Al(III) acetylacetonate and co-decomposition of the residual chelates. The co-decomposition is judged to occur via an intermediary complex between both monomeric chelates. It primarily leads to an amorphous Ti, Al, C and O-containing phase which develops crystalline alumina and titanium monoxide upon annealing to high temperatures. The carbonaceous component of the amorphous phase assists in carbothermal formation and stabilization of titanium monoxide.

Microwave sample preparation for detection of Si, P, V, Cr, Mn, Ni, Cu, and W using inductively coupled plasma atomic emission spectrometry in engineering steels

The article describes the procedure of microwave decomposition of engineering alloy steel during stepwise microwave heating and detection of Si, P, V, Cr, Mn, Ni, Cu, and W using ICP-AES. The composition of the mixture of acids and the parameters of sample microwave decomposition in an autoclave are optimized, thus facilitating threefold reduction of analysis time. The accuracy of detection of Si, P, V, Cr, Mn, Ni, Cu, and W is verified by analysis of reference specimens and comparison with the data acquired by conventional methods.

Optical Studies of Poly(hydroxy imide) to Polybenzoxazole Thermal Rearrangement

Studies of the optical properties of poly(hydroxy imide) (HPI) exposed to stepwise heating from room temperature up to 400 °C are reported in this work. It is demonstrated that this new method can be used to monitor thermal rearrangement (TR) of HPI to polybenzoxazole (PBO). Temperature dependences of the absorption edge parameters (Urbach energy and energy gap) are obtained and used to estimate the changes in the defects states and conjugation within the polymer chain associated with its TR to PBO. It is shown that the conversion temperatures determined based on the optical studies correspond to those received from the thermogravimetric analysis (TGA) investigations. Moreover, it is demonstrated that transition to PBO is accompanied by an 11‐fold increase in nitrogen permeability associated with only a slight decrease in O2/N2 selectivity from 8.8 to 7.2. image

Thermodynamic properties of intermetallic PtTe determined by means of a solid electrolyte EMF method

In this experimental work, the oxygen concentration electrochemical galvanic cell of the type (−)Pt|Pt(s), PtTe(s), TeO2(s,l)|YSZ|O2(g)|Pt(+) was applied to determine the thermodynamic properties of intermetallic platinum monotelluride PtTe. Yttria-stabilized zirconia solid electrolyte was utilized as a fast oxygen ion conductor. The repeatability of the experimental results was ensured by conducting three identical runs in stepwise heating and cooling cycles. The standard Gibbs energy of formation of PtTe was determined for the first time in the temperature range from (890 to 998)K to be:ΔfG°/(kJ·mol-1)±0.49=-73.54+28.57·10-3·T/K.The enthalpy of fusion and melting temperature of tellurium dioxide TeO2 were redetermined.