203 research outputs found
Negative and zero thermal expansion in alpha-(Cu2-xZnx)V2O7 solid solutions
No full textNegative or zero thermal expansion (NTE or ZTE) of materials is intriguing for controllable thermal expansion. We report a series of orthorhombic alpha-Cu2-xZnxV2O7 (x = 0, 0.1, 0.2), in which the volumetric coefficients of thermal expansion are successfully tuned from -10.19 * 10-6 K-1 to -1.58 * 10-6 K-1 in the temperature range of 100-475 K by increasing the content of Zn2+. It has been revealed that the transverse vibrations of oxygen bonded with vanadium are dominant in the contraction of the bc plane, leading to the overall volume NTE in alpha-Cu2V2O7. The introduction of Zn2+ densifies the crystal structure, which is presumed to suppress the space of transverse vibrations and results in the ZTE in alpha-Cu1.8Zn0.2V2O7. This work presents an effective method to realize ZTE in anisotropic framework systems
Electric-field-induced structure and domain texture evolution in PbZrO3-based antiferroelectric by in-situ high-energy synchrotron X-ray diffraction
No full textAntiferroelectrics (AFEs) have a great potential for modern electronic devices by virtue of the large strain during the antiferroelectric-to-ferroelectric (AFE-FE) phase transition under external electric fields. Although the fascinating macroscopic properties of AFE materials have been extensively studied, it is still unclear how the underlying structure evolution engenders their defining properties. Here we employ an electric biasing in-situ high-energy synchrotron X-ray diffraction technique to reveal the phase, domain texture, and lattice evolution in a high performance PbZrO3-based AFE material. During the reversible AFE-FE transition triggered by electric fields, the evolution of the superstructure for AFE pseudo-tetragonal and FE rhombohedral phase is found to display strong dependence on the angle with respect to the field direction. In contrast to previous prediction, it is found that there is no obvious domain reorientation in the AFE phase, when the system is far away from the AFE-FE transitions. The electric-field-induced FE rhombohedral phase exhibits an unusual microscopic behavior, distinguished from the normal one, presenting small changes in domain texture and lattice strain with electric field, and leading to a small piezoelectric response. The longitudinal, transverse, and volume strains estimated from the XRD peak profiles are well consistent with the macroscopic strain measurements. It is demonstrated that the large strain arises from the structural change associated with anisotropic lattice strain and highly preferential domain reorientation during the AFE-FE transitions. The AFE-FE switching sequence is constructed based on the present study, which provides a further understating of AFE materials.This is a manuscript of an article published as Liu, Hui, Longlong Fan, Shengdong Sun, Kun Lin, Yang Ren, Xiaoli Tan, Xianran Xing, and Jun Chen. "Electric-field-induced structure and domain texture evolution in PbZrO3-based antiferroelectric by in-situ high-energy synchrotron X-ray diffraction." Acta Materialia (2019). DOI: 10.1016/j.actamat.2019.11.050. Posted with permission.</p
High-Curie-Temperature Ferromagnetism in (Sc,Fe)F3 Fluorides and its Dependence on Chemical Valence
No full textA magnetic metal–fluoride system is shown for the first time to have a high Curie temperature (≈545 K). The magnetism correlates intimately with the Fe2+/Fe3+ ratio. As the ratio increases, the weak magnetism displayed by unordered magnetic moments intensifies, and these magnetic moments align in parallel. Simultaneously, a magneto-volume effect is also shown to increase the lattice volume
New Insights into the Negative Thermal Expansion: Direct Experimental Evidence for the "Guitar-String" Effect in Cubic ScF3
No full textThe understanding of the negative thermal
expansion (NTE) mechanism remains challenging but
critical for the development of NTE materials. This study
sheds light on NTE of ScF3, one of the most outstanding
materials with NTE. The local dynamics of ScF3 has been
investigated by a combined analysis of synchrotron-based
X-ray total scattering, extended X-ray absorption fine
structure, and neutron powder diffraction. Very interestingly,
we observe that (i) the Sc−F nearest-neighbor
distance strongly expands with increasing temperature,
while the Sc−Sc next-nearest-neighbor distance contracts,
(ii) the thermal ellipsoids of relative vibrations between
Sc−F nearest-neighbors are highly elongated in the
direction perpendicular to the Sc−F bond, indicating
that the Sc−F bond is much softer to bend than to stretch,
and (iii) there is mainly dynamically transverse motion of
fluorine atoms, rather than static shifts. These results are
direct experimental evidence for the NTE mechanism, in
which the rigid unit is not necessary for the occurrence of
NTE, and the key role is played by the transverse thermal
vibrations of fluorine atoms through the “guitar-string”
effect
A Novel Method for Early Warning and Quantitative Evaluation of Liquid Loading in Gas Wellbore Based on Dynamic Production Data: A Case Study of Linxing Tight Gas Field
No full textGas wells in Linxing Tight Gas Field are characterized by significant water production, and individual well water production measurement is missing, which pose challenges to predict liquid loading and conduct quantitative evaluations. Moreover, relying solely on flow temperature and pressure testing can be costly and time-consuming. To address these critical issues, we established the prewarning model and quantitative evaluation method for liquid loading. By utilizing those models, real-time judgment and evaluation of liquid loading can be achieved without individual well water production measurements. Our researches reveal that the pressure differential per unit gas production exhibits four patterns for different production stages. In contrast to maintaining a consistent pattern in the absence of liquid loading, the presence of fluid accumulation in production wells can be diagnosed through the increase in the specific production pressure difference within the liquid-loaded production section. Furthermore, the height of liquid loading in the wellbore can be calculated by using the quantitative evaluation model, which can match well with the field tests. The average error can be only 5.9%, and it will offer a novel solution for early warning and quantitative evaluation of wellbore liquid loading in water-producing tight gas fields. In addition, the limitation for strong stress sensitivity effect and high initial water yield-well needs to be broken through in future work
Sedimentology and mechanism of a lacustrine syn-rift fan delta system: A case study of the Paleogene Gaobei Slope Belt, Bohai Bay Basin, China
No full textFan delta systems have long been studied as a kind of good hydrocarbon reservoirs. Although many models have been raised according to their local conditions, there still exists some controversies regarding the formations of the ones developed in continental syn-rift settings. Taking Paleogene Es32+3 of Gaobei Slope Belt as an example, this paper conducted a comprehensive geological study and a forward depositional modeling. The results show that the sediment within the study area came mainly from the northeastern Baigezhuang uplift and the northwestern Xinanzhuang uplift over a short distance. The sedimentary system is characterized by subaerial debris flow, subaerial braided channels, subaqueous distributary channels, front sand bars and front sand sheets. Furthermore, the study area is a balance-filled basin that experienced a 3rd order normal regression followed by a transgression during the development of the study interval. The results also show that, a stable subsidence rate with small-magnitude climate changes would be a plausible explain for the entire sequence of the fan delta system in the study area. The tectonic subsidence was indeed the dominant driving force to a continental syn-rift fan delta system, although the climate, sediment supply or lake level might bring some lower order (e.g., 4th and 5th order) superimpositions. This paper proposed a likely model for fan deltas developed in continental syn-rift settings, which is expected to gain some insights into the forming mechanism and provide some supports for the reservoir characterization of similar and correlative sedimentary systems.Financial support was provided by the Fundamental Research Funds for the Central Universities and the QUST Initial Fund for Young Scholars.The authors acknowledge the editors and anonymous reviewers for their helpful and constructive editing and reviewing work. The authors also acknowledge Dr. Phil Moore from U. of S Carolina and Prof. Zhu Hongtao from China University of Geosciences for their supports on the Sedpak simulation software
Parallel Framework for Complex Reservoir Simulation with AdvancedDiscretization and Linearization Schemes
No full textThe continuous progress of reservoir monitoring technology provides encouraging capacities to reduceuncertainties in the subsurface characterization and to mitigate risks in field development applying thereservoir simulation approach. However, it is always challenging to take full advantage of the observationdata, since an accurate representation of strong heterogeneities requires a high-resolution grid. Most ofthe discretization methods cannot handle full tensor permeability, and high nonlinearity introduced bycomplex physical process drastically reduces simulation efficiency. In this work, we develop an advancedparallel framework for reservoir simulation with the implementation of state of the art discretizationand linearization methods. We apply the multipoint flux approximation (MPFA) method to handle thefull tensor permeability in unstructured grids. To keep the fidelity of the geological model and improvecomputational efficiency, we use massively parallel computations via Message Passing Interface (MPI).Complex subsurface physics is described by mass-based formulations making the framework flexible forgeneral-purpose reservoir simulation. However, the representation of phase behavior introduces additionalworkload when compared with the phase-based formulations in the traditional approach. Here, we apply theOperator-Based Linearization (OBL) approach which not only overcomes this drawback but also turns it toan advantage. In this method, the conservation equations are described in an operator form. By constructinga library of tabulated operators, the repeated work spent on complex phase behavior and property evaluationcan be significantly reduced. We benchmark the parallel framework with analytical solutions under single-phase flow and multiphase flow. The results demonstrate that the parallel framework provides accuratesimulation results for structured and unstructured grids. We validate that MPFA implemented in our parallelframework converges to real solutions when the permeability is a full tensor. Besides, several realisticcases have been rigorously tested confirming high computational capacity, efficiency, and accuracy of theadvanced massively parallel framework for general-purpose reservoir simulation. With the implementationof MPFA and OBL approaches, the parallel framework is fully equipped for the simulation of problemswith full tensor permeability, high-heterogeneities, and complex physical processes.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Reservoir Engineerin
Direct Observation of Polarization Rotation in the Monoclinic MB Phase under Electrical Loading
No full textThe monoclinic phase has received
a lot of research because of
its importance in explaining the origin of high piezoelectric and
ferroelectric performances around the morphotropic phase boundary.
In the present study, we have investigated the detailed structural
evolution in monoclinic PbZr0.535Ti0.465O3 ferroelectric ceramics induced by an electric field with
in situ high-energy synchrotron diffraction combined with two-dimensional
(2D) geometry scattering technology. It has been discovered that an
electric-field-induced single monoclinic MB phase persists indefinitely. The lattice, unit cell volume, and
spontaneous polarization of the monoclinic MB structure exhibit significant and flexible responses to the
external electric field, i.e., the spontaneous polarization rotates
continuously and the lattice and unit cell volume present a butterfly
form under the influence of the bipolar electric field. Particularly,
direct experimental evidence demonstrates that the macropolarization
of PbZr0.535Ti0.465O3 is derived
from the spontaneous polarization rotation rather than domain switching,
and its volume expansion plays a vital role in the piezoelectric response
Modeling and Experimental Validation of the Atomization Efficiency of a Rotary Atomizer for Aerial Spraying
No full textRotary atomizers are mainly used in agricultural manned aircrafts. Atomization characteristics at high speeds have been studied, but methods to measure the atomization efficiency have not been elucidated. The atomization efficiency of rotary atomizers under high-speed airflow was investigated using an IEA-I high-speed wind tunnel experimental installation, AU5000 rotary atomizer, and a laser diffraction particle size analyzer. Accordingly, a model equation for atomization efficiency measurements was innovatively obtained. When the flow rate, fan blade angle of the atomizer, and wind speed were used as variables, the experimental results showed that the atomization efficiency mainly depended on the fan blade angle. When the fan blade angle was 35°, the atomization efficiency was optimal, regardless of wind speed. In contrast, when the fan blade angle of the atomizer was 65°, it exhibited the worst atomization efficiency, regardless of the wind speed. The experimental data from this study can provide guidance for aerial application in fixed-wing manned aircraft, such as the flow rate, and operating speed
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