دانلود کتاب Small-Angle Scattering from Confined and Interfacial Fluids

The phase behavior of bulk fluids is now well understood and their properties can bepredicted accurately using equations of state over a wide range of pressures andtemperatures. The behavior of bulk fluids changes dramatically when they areinjected into small pores, due to increasing importance of the boundary conditionsand molecule-surface interactions. Thus, confinement leads to the emergence of anew set of variables that impact the phase behavior in tight pores but may beneglected in the thermodynamic limit. Examples of such variables are the pore size,shape, and interconnectivity as well as the chemical composition of the pore wallsand fluid-surface interaction potential. Due to involvement of numerous systemspecificparameters, a comprehensive understanding of the influence of confinementon the fluid behavior is only beginning to emerge.In addition to their fundamental interest, the ability to understand and predict thephase behavior and dynamics of fluids in natural and engineered porous solids iscrucial for a variety of the environment- and energy storage-related technologies.These include the capture and sequestration of anthropogenic greenhouse gases,hydrogen storage, membrane separation of gases, environmental remediation, andcatalysis. Until recently, the adsorption of fluids and structure of pores in variousporous materials have been routinely explored using volumetric and gravimetricmethods, mercury porosimetry, and sorption isotherms. These traditional tools,however, have their limitations. First, they provide data averaged over the entiresample volume and thus fail to elucidate how pores of different sizes contribute tothe integral parameters as a function of pressure and temperature. Second, they areinvasive, which eliminates contribution from the closed-off regions of the porespace and may affect the integrity of the solid matrix. In contrast, noninvasivesmall-angle scattering (SAS) techniques offer the unique opportunity to “look butnot touch” inside pores and monitor changes in the adsorption behavior of fluidmolecules confined in pores of different sizes and topology, as well as to detect thepores inaccessible to the invading fluid. For this reason, a few years ago researchersbegan to develop and refine scattering techniques and their interpretations as areliable tool for probing properties of confined and interfacial fluids in natural andengineered porous materials with different structural properties. These effortsresulted in evolving new methods of the SAS data analysis and interpretation aswell as developing the new generation of the state-of-the-art high pressure cells thatare being used by researchers interested in studying structural and adsorptionproperties of confined supercritical fluids and gases under pressure.This book examines the macro-, meso- and microscopic aspects of the fluidbehavior in porous solids using noninvasive methods of small-angle neutron andx-ray scattering (SANS and SAXS) as well as ultra small-angle neutron and x-rayscattering (USANS and USAXS). There is a great deal of similarity between thex-ray and neutron scattering and therefore both methods are presented anddiscussed together so that readers may become familiar with both and appreciatethe advantages and disadvantages of each type of radiation for the specific systemor type of experiment. Both neutrons and x-rays penetrate porous solids and arescattered on the solid/void interface. At ambient conditions, the resulting scatteringpatterns are governed by the geometry and topology of the pore space on the scalefrom about 1 nm to about 10 μm and provide quantitative data about the totalporosity, pore size distribution, and the specific area of the scattering interface. SASexperiments performed on fluid saturated samples maintained in cells with controlledpressure and temperature conditions, combined with isotopic substitution ofinvading fluids, facilitate contrast variation experiments. The simplest application—direct contrast matching between the solid matrix and the invading fluid—discriminates between the open (accessible) and closed (inaccessible) porosity.Both SANS/USANS and SAXS/USAXS enable the observation of pore-size-specificinvasion of the pore space by fluids and help to access important informationon the volume fraction of the adsorbed phase and its average physical density. Forgeological samples, this can be done in situ at a subsurface-like temperature andpressure conditions.The book is meant as a reference for active researchers in the field, but also mayserve as a comprehensive guide for university faculty members and students, whomay be insufficiently aware of the range of opportunities provided by the smallanglescattering techniques. The book commences with introductory chapters,which describe major principles of SAS techniques and are sufficiently comprehensiveto be useful to researchers interested in structural characterization ofvarious types of materials in different fields of science. Chapters 1–4 introducethe basic properties of neutrons and x-rays, provide brief description of the availableneutron and x-ray sources, and give illustrative examples of SAS instrumentationand sample environment. This is followed by discussion of the practicalaspects of SAS experiments, sample preparation methods, optimal instrumentconfigurations, and basic principles of the data reduction and analysis presentedin Chaps. 5 and 6. Chapter 7 deals with the SAS structural characterization ofvarious porous solids, and Chap. 8 describes studies of confined vapors belowsaturating pressure with the emphasis on vapor adsorption and capillary condensation.Chapter 9 is concerned with studies of confined and interfacial liquids.Experimental SAS investigations of high-pressure adsorption of supercritical fluidsand gases in various engineered and natural porous materials are discussed inChap. 10.The author has enjoyed and benefitted from longstanding collaboration withT.P. Blach, N.C. Gallego, C.I. Contescu, M. Mastalerz, J.R. Morris, A.P. Radlinski,J.A. Rupp, L.F. Ruppert, R. Sakurovs, and G.D. Wignall. Special thanks are due tomy younger colleagues J. Bahadur, S.M. Chathoth, G. Cheng, and L. He whocontributed their enthusiasm and talent in many studies of confined fluids describedin this book. It is a great pleasure to acknowledge M.M. Agamalian, J.M. Carpenter,A.P. Radlinski, and G.D. Wignall for reading select chapters of the manuscript andoffering valuable comments. The assistance of Renee´ Manning and GenevieveMartin in preparing high quality artwork is greatly appreciated.