Multiphase Formation Research Articles

Evaluation of the atmospheric significance of multiphase reactions in atmospheric secondary organic aerosol formation

Abstract. In a simple conceptual cloud-aerosol model the mass of secondary organic aerosol (SOA) that may be formed in multiphase reaction in an idealized scenario involving two cloud cycles separated with a cloud-free period is evaluated. The conditions are set to those typical of continental clouds, and each parameter used in the model calculations is selected as a mean of available observational data of individual species for which the multiphase SOA formation route has been established. In the idealized setting gas and aqueous-phase reactions are both considered, but only the latter is expected to yield products of sufficiently low volatility to be retained by aerosol particles after the cloud dissipates. The key variable of the model is the Henry-constant which primarily determines how important multiphase reactions are relative to gas-phase photooxidation processes. The precursor considered in the model is assumed to already have some affinity to water, i.e. it is a compound having oxygen-containing functional group(s). As a principal model output an aerosol yield parameter is calculated for the multiphase SOA formation route as a function of the Henry-constant, and has been found to be significant already above H~103 M atm-1. Among the potential precursors that may be eligible for this mechanism based on their Henry constants, there are a suite of oxygenated compounds such as primary oxidation products of biogenic and anthropogenic hydrocarbons, including, for example, pinonaldehyde. Finally, the analogy of multiphase SOA formation to in-cloud sulfate production is exploited.

Relationship between multi-phase formation and molecular structure for liquid crystal system

A mechanical model of liquid crystals (LCs) was used to explain the phase formation and thermal properties. The LC phases in the model are micro-machine systems consisting of an ensemble of molecular rotors, and some dynamic parameters in a semi-experiment molecular orbit method. A novel explanation on the multi-phase formation of LC system is obtained. It is found that the value of the critical rotational velocity is a key parameter for the characterization of each homologous series. The dipole moment of the molecules was also discussed.

Processing and properties of C–Mn steel with dual-phase microstructure

Effect of applied thermomechanical rolling and heat treatment on dual-phase and multi-phase microstructure formation in steel 15 (formerly 15GA) and achieved mechanical properties was studied. Thermomechanical rolling was made in full austenitic range. After rolling steel was held in the air for 145–250 s in α + γ temperature range then quenched in water. In that way dual-phase microstructure was created in rolled plate of the thickness 12 mm. The heat treatment of steel was based on annealing in α + γ range at temperature 1063 K for 3600 s, quenching in water and tempering at temperature 913 K for 5400 s. Microstructures after these treatments were composed of ferrite matrix and bainite–martensite–austenite islands (BMA). Volume fraction of islands was in the range 19–37% for steel after thermomechanical treatment and 22–29% after heat treatment. The effect of volume fraction of BMA islands and residual austenite within those islands on mechanical properties of steel was observed. High tensile properties were achieved: after thermomechanical rolling: TS = 910 MPa, YS = 760 MPa, El = 14.4% and after water quenching from α + γ temperature range and tempering: TS = 510 MPa, YS = 328 MPa, El = 37.27%.

Multi-phase galaxy formation and quasar absorption systems

The central problem of galaxy formation is understanding the cooling and condensation of gas in dark matter halos. It is now clear that to match observations this requires further physics than the simple assumptions of single phase gas cooling. A model of multi-phase cooling (Maller & Bullock 2004) can successfully account for the upper cutoff in the masses of galaxies and provides a natural explanation of many types of absorption systems (Mo & Miralda-Escude 1996). Absorption systems are our best probes of the gaseous content of galaxy halos and therefore provide important constraints on models for gas cooling into galaxies. All physical processes that effect gas cooling redistribute gas and therefore are detectable in absorption systems. Detailed studies of the nature of gas in galaxy halos using absorption systems are crucial for building a correct theory of galaxy formation.

Electrochemical performance of ball-milled Ti–V-based electrode alloy

The effect of ball-milling on the electrochemical performance of Ti–30V–15Cr–15Mn alloy has been investigated. It was found that the ball-milling is effective in improvement of the discharge capacity of this alloy, due to the reduction in the particle size. The discharge capacity increases from 30 mAh g −1 of the as-cast sample to 198 mAh g −1 of the 30 min ball-milled sample at room temperature. A maximum discharge capacity of 710 mAh g −1 is obtained for the 3 h ball-milled Ti–30V–15Cr–15Mn alloy at discharge current of 10 mA g −1 in 6 M KOH solution at 353 K . The appearance of the two discharge plateaus on the discharge curves of the alloy is related to its multi-phase hydride formation.

Types of Karst‐fractured and Porous Reservoirs in China's Carbonates and the Nature of the Tahe Oilfield in the Tarim Basin

Abstract Almost all the oil and gas reservoirs developed in marine sedimentary strata of China have undergone processes of multi‐phase reservoir formation and later modification. The irregular reservoirs are classified into three types as the Naxi, Tahe and Renqiu ones, increasing successively in the development degree of karstificated pores and fissures and the connection degree of independent reservoirs. In these reservoirs, the unity in the fluid feature, pressure and oil‐gas‐water interface also increases successively from the Naxi to the Renqiu type. The main body of Ordovician reservoirs of the Tahe Oilfield in the Tarim Basin is a network pool rather than a stratified, massive, stratigraphically‐unconformed or weathering‐crust one. The fluid nature of oil, gas and water, the interface positions and the pressures, as well as the dynamic conditions of fluids within the reservoirs during the production are all different from those in stratified or massive oil and gas reservoirs. Carbonates in the Akekule uplift and the Tahe Oilfield are assemblages of various types of reservoirs, which have an overall oil‐bearing potential and obvious uneven distribution. Testing and producing tests are the major means to evaluate this type of reservoirs and acid fracturing improvement is a key link in petroleum exploration and development.

Single-Pulse Echo and Its Secondary Signals in Two-Level Spin Systems

The dependences of the amplitudes of single- and two-pulse spin echoes and their secondary signals in NMR (protons of glycerin in an inhomogeneous magnetic field) in the exciting-pulse repetition period Tr have been compared. The difference in origin of the primary and secondary signals of a single-pulse echo in a two-level spin system has been confirmed. It is shown that only a primary single-pulse echo observed when Tr > T1 (T1 is the spin lattice relaxation time) results from single-pulse excitation. The secondary single-pulse echo signals are observed for Tr < T1 and are due to the multiphase formation mechanism. The results obtained for magnetically ordered substances are analyzed. Based on these data, it was inferred earlier that primary and secondary single-pulse echo signals were formed by one and the same multiphase mechanism.

Ultraviolet Line Emission from Metals in the Low‐Redshift Intergalactic Medium

We use a high-resolution cosmological simulation that includes hydrodynamics, multiphase star formation, and galactic winds to predict the distribution of metal line emission at z ~ 0 from the intergalactic medium (IGM). We focus on two ultraviolet doublet transitions, O VI λλ1032, 1038 and C IV λλ1548, 1551. Emission from filaments with moderate overdensities is orders of magnitude smaller than the background, but isolated emission from enriched dense regions with T ~ 105-105.5 K and characteristic size ~50-100 kpc can be detected above the background. We show that the emission from these regions is substantially greater when we use the metallicities predicted by the simulation (which includes enrichment through galactic winds) than when we assume a uniform IGM metallicity. Luminous regions correspond to volumes that have recently been influenced by galactic winds. We also show that the line emission is clustered on scales ~1 h-1 Mpc. We argue that although these transitions are not effective tracers of the warm-hot intergalactic medium, they do provide a route to study the chemical enrichment of the IGM and the physics of galactic winds.

High-Temperature Oxidation Behavior of Elemental Powder Metallurgy Processed TiAl-Mn-Mo-C Alloys with Yttrium Addition

Effects of yttrium addition on the formation of oxide scales and the oxidation resistance of elemental powder metallurgy (EPM) processed TiAl-Mn-Mo-C alloys were studied. The Y-containing TiAl-based alloys (0:1� 0:6 at%Y) showed better oxidation resistance than Y-free alloy oxidized in air at 800 � C for 350 h. The Y-containing alloys showed a significantly reduced weight gain, especially for 0.6 at%Y-added alloy. In the Y-free alloy, the scale formed during extended air-exposure at 800 � C consisted of TiO2 and � -Al2O3. For 0.6 at%Y-added alloy, however, the oxide scale was composed of a complex mixture of TiO2, � -Al2O3 ,Y 2O3 and Al5Y3O12. The formation of multi-phase (Y, Al)O-type oxides layer in a transitional Y-rich subscale close to the substrate and an increase of the amount of � -Al2O3 in the mixture oxide layer in the Y-added alloys were the main contributor to improving the oxidation resistance of the alloys. The reduction of oxygen content in the substrate also had a beneficial effect on the oxidation resistance of the Y-containing TiAl-based alloys.

Sol–gel synthesis, structural and ion transport studies of lithium borosilicate glasses

Lithium borosilicate (LBS) glasses of different modifier to formers ( m/ f) ratios were synthesized through sol–gel process. Structural characterisation of LBS glasses were made using XRD, FTIR and DSC techniques. XRD pattern of LBS samples showed amorphous phase for gels heat treated between 573 and 698 K and further heat treatment above 698 K showed the formation of crystalline multiphases. FTIR spectra for dried LBS gels between 338 and 443 K showed the presence of hydroxyl group on the surface of silicate and borates matrix and on heat treatment, the FTIR spectra revealed the formation of silicate and borate linkages in LBS glassy matrix. DSC curve confirmed the presence of adsorbed water molecules in LBS glassy matrix. Impedance measurements were carried out on LBS samples of different m/ f ratios as a function of temperature and data were analyzed using Boukamp equivalent circuit software. The conductivity of LBS glasses at different temperatures was calculated from analyzed impedance data. Activation energy ( E a) is obtained from Arrhenius plots of the dc conductivity and it is found to be 0.64 (±0.02) eV for high conducting sample. ac conductivity is calculated from impedance data and analyzed using Jonscher's power law (JPL) exponent (s) for m/ f ratios of LBS samples at different temperatures. The power law exponent s of LBS glasses exhibited a non-linear behavior with temperature. The electric modulus data were fitted with Kohlraush–William–Watts (KWW) stretched exponential function and the modulus formalism is used to study the ionic relaxation behavior in LBS samples.

A Systematic Method to Predict Cloud Point Temperature and Solid Precipitation

Solid precipitations (or depositions) in crude oil operations are undesirable because they may eventually plug the process equipment and/or pipelines; as such, accurate prediction of cloud point temperature is essential in the design and operation of many oil production facilities. Determining the cloud point temperature of a mixture requires a robust solution of a multiphase, multicomponent phase equilibrium problem. Solution of the phase equilibrium problem rests on the relations set by the Gibbs criterion for stable equilibrium and the principle of mass conservation. Mathematically, two solution methods are used to characterize the equilibrium properties of a mixture at given temperature and pressure: the equal-fugacity (iteration-function formulation) and the Gibbs free energy minimization approach. In addition, an accurate solution model capable of predicting multiphase formation is required. In this study, we implement the iteration function method enhanced with a solid–liquid–vapor phase-check procedure to calculate cloud point temperatures and the amount of solid precipitations. The Peng-Robinson equation of state with a modified α function, as suggested by Gasem et al. ([2001]), was utilized to model vapor–liquid equilibria while regular solution theory was used to describe solid-liquid equilibria. We also present a systematic method to characterize the heavy components of oil. The results of this study are in excellent agreement with experimental cloud point temperature and solid precipitation data for four North Sea oils reported by Pedersen et al. ([1991]).

The analysis of the two discharge plateaus for Ti–Ni-based metal hydride electrode alloys

In some conditions, the multi-phase composition of the hydrogen storage electrode alloy can be reflected on its discharge curve. In this paper, the discharge curves of the Ti–Ni-based hydrogen storage alloys have be analyzed using electrochemical techniques and XRD. We concluded that the appearance of the two discharge plateaus on the discharge curves of the Ti 0.5Al 0.25Ni 0.25 alloy and Ti 3Ni 1.7M 0.3 (M=Ni, Al, Co, Cr) alloys is related to their multi-phase composition and multi-phase hydride formation. The appearance of the first fastigiated plateau is the result of together releasing hydrogen of TiNi and Ti 2Ni phases. The secondary flat plateau represents releasing hydrogen process of only the Ti 2Ni phase.

Multiphase formation of superimposed ice during a mass-balance year at a maritime high-Arctic glacier

AbstractMeteorological and snow-temperature data from midtre Lovénbreen, Spitsbergen, Svalbard, indicate two distinct annual phases of rapid snowpack warming and superimposed-ice formation in 1998/99. Short periods of positive air temperatures in early winter, lasting up to 36 hours and often coinciding with rainfall, caused rapid glacier-wide melting. Percolating water froze to form superimposed ice on the lower half of the glacier, and wetted–refrozen snow and ice lenses at higher altitudes. The second period of superimposed-ice formation commenced in May/June 1999 and continued for 5 weeks at low altitudes and throughout the summer at high altitudes. These observations at midtre Lovénbreen are typical of Spitsbergen glaciers and reflect the unique climatology of the region. They contrast with those from glaciers in more continental climatic settings where superimposed-ice formation is confined to a single period during summer. There are significant implications for glacier mass balance, with superimposed ice locally comprising up to 20% of winter balances and accounting for ∼16–25% of the annual accumulation. Since projected climatic warming is greatest during the winter months in Arctic regions, superimposed ice may become an increasingly important component of the winter, and potentially the net, balance of Spitsbergen glaciers.

X-ray diffraction and microstructural studies in 2 : 17 type Sm–Co magnetic alloys containing Fe, Cu, and Zr

X-ray diffraction and microstructural studies were carried out on 2 : 17 type Sm–Co alloys containing Fe, Cu, and Zr (13–14 at.% Sm, 57–60 at.% Co, 20–22 at.% Fe, 4 at.% Cu, and 3 at.% Zr) in as-cast and heat-treated conditions. Microstructural studies revealed that the as-cast alloys contain three phases. It was observed that the samples subjected to sintering at 1463 K for 45 min followed by a solution treatment at 1448 K for 1 h resulted in nearly a single-phase, rhombohedral crystal structure (Th2Zn17-type). Subsequent isothermal aging at 1123 K and ramp-cooling to 673 K resulted in a mixture of Sm2Co17- and SmCo5-type phases with the former as major phase. It was also found that samples (Sm &gt; 13 at.%) sintered at temperatures &gt;1463 K showed incipient melting and multiphase formation.

Influence of pores on high temperature oxidation of titanium and Ti–3Cu alloy

The results of investigations on corrosion products formed on titanium and on Ti–3Cu alloy during oxidation in air at temperatures in the range 650–1200°C are reported. Lattice diffusion dominates the oxidation process, but the formation of multiphase and multilayer scale, which is also porous, influences the kinetics. It has been found that, at temperatures of 950°C and above, growing pores facilitate mass transport to and from the underlying material and increase the oxidation rate.

The effect of BaO on the crystallization behaviour of a cordierite-type glass

Crystallization kinetics of the cordierite-type (MgAl 1.83S 2.25O y ) glass with the BaO addition ( X molar ratio) in the powder form has been studied by non-isothermal DTA. Formation of multiphase corresponding to various BaO content was investigated by X-diffraction technique. Addition of small amount of BaO ( X ≤ 3%) to the cordierite-based glass could suppress the crystallization of the α-cordierite phase. Enstatite and hexacelsian phases were the predominant phase with the increase of BaO content in the range of 3% < X < 8% and X ≥ 8%, respectively

Correlation between electronic structure, mechanical properties and phase stability in intermetallic compounds

From the detailed electronic structure studies on intermetallic compounds, it has been found that these materials have low heat of formation and large glass-forming ability, if the Fermi level falls on the peak in the density of states (DOS) curve. On the other hand, if theE F falls on the pseudogap in the DOS curve, the ordering energy will be larger and the system prefers to form an ordered alloy. The first principles electronic structure calculations performed on Ni3Al show that it is possible to vary the filling of bonding, nonbonding and antibonding states in the DOS curve and this in turn shows gradual structural transformation as well as formation of multiphases by ternary alloying. Possibilities of tailoring the properties of materials by tuning the Fermi level is discussed in this paper.

Simultaneous occurrence of multiphases in the interfacial reactions of ultrahigh-vacuum-deposited V and Zr thin films on (111)Si

Simultaneous occurrence of multiphases was observed in the interfacial reactions of ultrahigh-vacuum (UHV) -deposited V and Zr thin films on (111) Si by high-resolution transmission electron microscopy in conjunction with fast Fourier transform diffraction analysis and image simulation. For the V/Si system, an amorphous interlayer (a-interlayer), V3Si and V5Si3, were found to form simultaneously in samples annealed at 500 °C for 60 min. For the Zr/Si system, an a-interlayer, Zr5Si3 as well as FeB and CrB types of ZrSi, were observed to form in samples annealed at 440 °C for 40 min. The formation of multiphases appeared to be quite general in the initial stages of interfacial reactions of UHV-deposited refractory metal and rare-earth–metal thin films on silicon. The observation of the prevalence of the formation of multiphases in the initial stages of thin film reactions called for a reexamination of generally accepted ‘‘difference’’ in reaction sequence between bulk and thin-film couples.

Evidence for the multi-stage formation of the south-western Valencia Trough

A basin evolution model for the south-western Valencia Trough is established using thermal and palaeo-thermal data. Bottomhole temperature and drillstem test data from oil wells have been used to determine the geothermal gradient in the study area. A combination of well log data and X-ray diffractometry analyses carried out on rock samples from the Ibiza Marino well has allowed an estimation of the bulk thermal conductivity and heat flow density. Integrating these data with previous seafloor heat flow measurements yields a regional surface heat flow density of about 90–100 mW m −2. Vitrinite reflectance data available from the Ibiza Marino well have been used as a palaeo-thermal constraint for the proposed tectonic models. Two different modelling approaches are tested: a single rift phase model and a multi-phase formation model. The single rifting phase, which considers different eroded thicknesses, is ruled out as it does not match the observed data. A multi-stage evolution coherent with the geological and geophysical data is proposed and consists of three Mesozoic rifting events, Palaeogene compression (to which erosion of about 5 km of Late Jurassic and Cretaceous sediments is related) and a Neogene rifting event that gave rise to the present day Valencia Trough. Surface heat flow, vitrinite data and eroded thickness are successfully integrated in the proposed model.

Simultaneous occurrence of multiphases in the interfacial reactions of ultrahigh vacuum deposited Hf and Cr thin films on (111)Si

Simultaneous occurrence of multiphases were observed in the interfacial reactions of ultrahigh vacuum deposited Hf and Cr thin films on (111)Si by high-resolution transmission electron microscopy in conjunction with fast Fourier transform diffraction analysis and image simulation. For Hf/Si system, an amorphous interlayer, Hf5Si3 as well as FeB and CrB types of HfSi were found to form simultaneously in samples annealed at 530 °C for 40–80 min. For Cr/Si system, an amorphous interlayer, Cr5Si3, CrSi, and CrSi2 were observed to form in samples annealed at 375 °C for 30 min. The formation of multiphases appeared to be quite general in the initial stages of interfacial reactions of ultrahigh vacuum deposited refractory thin films. The results called for a reexamination of generally accepted ‘‘difference’’ in reaction sequence between bulk and thin-film couples.