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Chen, Sow-Hsin

Publications and source records attributed to Chen, Sow-Hsin.

17 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Water dynamics in C–S–H and M-S-H cement pastes: A revised jump-diffusion and rotation-diffusion model

The Quasi-Elastic Neutron Scattering (QENS) spectra from four cement pastes are re-analyzed by a new revised jump-diffusion and rotation-diffusion model (rJRM). From the QENS fit, it can be seen that the rJRM is an improved model to fit QENS spectra within the whole detected neutron energy transfer and scattering vector. By the rJRM fitting, the structure parameters extracted from QENS spectra show that both the additives aluminum-silicate nanotubes (ASN) and carboxyl group functionalized ASN (ASN-COOH) can improve magnesium-silicate-hydrate (M-S-H) toward calcium-silicate-hydrate (C–S–H) direction in mechanical properties, but the improvement is weakened with decreasing temperatures. The extracted dynamical parameters show that there is a dynamic anomaly near 230 K in not only translational but also rotational diffusion of water confined in all the investigated samples. In conclusion, the anomaly in rotational diffusion is new compared with those results obtained by the QENS fit using other models.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Some Aspects of the Liquid Water Thermodynamic Behavior: From The Stable to the Deep Supercooled Regime

Liquid water is considered to be a peculiar example of glass forming materials because of the possibility of giving rise to amorphous phases with different densities and of the thermodynamic anomalies that characterize its supercooled liquid phase. In the present work, literature data on the density of bulk liquid water are analyzed in a wide temperature-pressure range, also including the glass phases. A careful data analysis, which was performed on different density isobars, made in terms of thermodynamic response functions, like the thermal expansion αP and the specific heat differences C P -C V , proves, exclusively from the experimental data, the thermodynamic consistence of the liquid-liquid transition hypothesis. The study confirms that supercooled bulk water is a mixture of two liquid “phases”, namely the high density (HDL) and the low density (LDL) liquids that characterize different regions of the water phase diagram. Furthermore, the C P -C V isobars behaviors clearly support the existence of both a liquid–liquid transition and of a liquid–liquid critical point.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

The Proton Density of States in Confined Water (H2O)

The hydrogen density of states (DOS) in confined water has been probed by inelastic neutron scattering spectra in a wide range of its P–T phase diagram. The liquid–liquid transition and the dynamical crossover from the fragile (super-Arrhenius) to strong (Arrhenius) glass forming behavior have been studied, by taking into account the system polymorphism in both the liquid and amorphous solid phases. The interest is focused in the low energy region of the DOS ( E < 10 meV) and the data are discussed in terms of the energy landscape (local minima of the potential energy) approach. In this latest research, we consider a unit scale energy (EC) linked to the water local order governed by the hydrogen bonding (HB). All the measured spectra, scaled according to such energy, evidence a universal power law behavior with different exponents ( γ ) in the strong and fragile glass forming regions, respectively. In the first case, the DOS data obey the Debye squared-frequency law, whereas, in the second one, we obtain a value predicted in terms of the mode-coupling theory (MCT) ( γ ≃ 1.6 ).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Some considerations on the water polymorphism and the liquid-liquid transition by the density behavior in the liquid phase

The bulk liquid water density data (ρ) are studied in a very large temperature pressure range including also the glass phases. A thorough analysis of their isobars, together with the suggestions of recent thermodynamical studies, gives evidence of two crossovers at T* and P* above which the hydrogen bond interaction is unable to arrange the tetrahedral network that is at the basis of the liquid polymorphism giving rise to the low density liquid (LDL). The curvatures of these isobars, as a function of T, are completely different: concave below P* (where maxima are) and convex above. In both the cases, a continuity between liquid and glass is observed with P* as the border of the density evolution toward the two different polymorphic glasses (low and high density amorphous). The experimental data of the densities of these two glasses also show a markedly different pressure dependence. Here, on the basis of these observations in bulk water and by considering a recent study on the growth of the LDL phase, by decreasing temperature, we discuss the water liquid-liquid transition and evaluate the isothermal compressibility inside the deep supercooled regime. Such a quantity shows an additional maximum that is pressure dependent that under ambient conditions agrees with a recent X-ray experiment. In particular, the present analysis suggests the presence of a liquid-liquid critical point located at about 180 MPa and 197 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Nanoscale dynamics of water confined in ordered mesoporous carbon

The single particle dynamics of water confined in ordered mesoporous carbon matrix was investigated in the temperature range from 290 K to 170 K by quasielastic neutron scattering using three high resolution neutron spectrometers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Neutron and X-Ray Scattering Studies of New Green Cement, and Nanoconfined Water

This is the Final report on DE-FG02-90ER45429 for the time period from September 1, 1990 to May 31, 2017. The Principal Investigator is Sow-Hsin Chen, Department of Nuclear Science and Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139 (email: sowhsin@mit.edu). The Administrative Point of Contact at MIT is Sarah Svenson, Senior Contract Administrator, Office of Sponsored Programs, Tel: 617-253-2495, ssvenson@mit.edu. The DOE Program is the Office of Basic Energy Sciences (BES); Program manager is Dr. P. Thiyagarajan, Neutron Scattering SC-22.2/, Germantown Bldg., Germantown, MD 20874 . During these 27 years, the scientific activities has had a number developing emphases, as reflected from the change of Project Title in 1990 as “Construction of a Small Angle Neutron Scattering Spectrometer for Investigation of Microemulsions and Micellar Solutions in Bulk, in Porous Materials...” to “Neutron and X-Ray Scattering Studies of New Green Cement, and Nanoconfined Water” in the last renewal period, 2015-2017, with many title changes in between. Progress Report for each sub-project period was reported to DOE with detailed activity and budgetary reports. It is fair to summary that the chief activity has been in the use neutron, x-ray and laser spectroscopy to investigate materials properties of complex fluids and soft condensed matter. It started with conducting neutron and X-ray scattering experiments to study the structure and dynamics of glass-forming liquids in general first, then more specifically in the case of supercooled water in confined geometry, and culminating in the final study of new green cement. Experiments were conducted at various DOE supported national neutron facilities including ORNL, ANL, BNL and Los Alamos, as well as at NIST/NCNR. Whenever possible, experiments were also performed at numerous world-class facilities, such as those at Saclay and the Institut Laue Langevin (ILL) in Grenoble, France, and at National Synchrotron Radiation Research Center (NSRRC) in recent years in Taiwan, etc. Leveraging on the large number of international collaborate activities, a substantial percentage of activities were supported with collaborators’ own funding sources. These have help to carry out DOE’s mission and produce impressive research products far beyond what was possible with only DOE funding supports. The chief product during this period, 1990-2017, includes (1) Three hundred and eight scientific articles published in peer-reviewed and high-impacted scientific journals during 1990-2017, and a dozen monographs including four books for scientists and graduate students, (2) Twenty-four scientific conferences organized and 209 papers presented at many national and international conferences, (3) educate and train 9 post-doctoral fellows and 28 students including 22 Ph.D. students, 3 M.S. students, and 3 in other categories by providing a research experience in neutron and X-Ray scattering techniques, most of them were supported wholly or in part in the scientific topic of this award during the funding period and (4) numerous high-visibility awards and honors. This final report summarizes and details these research activities and products. At the close of this funding period, the fund from DOE has been totally spent.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2016

Dynamical behaviors of structural, constrained and free water in calcium- and magnesium-silicate-hydrate gels

We present the hypothesis that the mechanical properties of cement pastes depend strongly on their porosities. In a saturated paste, the porosity links to the free water volume after hydration. Structural water, constrained water, and free water have different dynamical behavior. Hence, it should be possible to extract information on pore system by exploiting the water dynamics. With our experiments we investigated the slow dynamics of hydration water confined in calcium- and magnesium-silicate-hydrate (C-S-H and M-S-H) gels using high-resolution quasi-elastic neutron scattering (QENS) technique. C-S-H and M-S-H are the chemical binders present in calcium rich and magnesium rich cements. We measured three M-S-H samples: pure M-S-H, M-S-H with aluminum-silicate nanotubes (ASN), and M-S-H with carboxyl group functionalized ASN (ASN-COOH). A C-S-H sample with the same water content (i.e. 0.3) is also studied for comparison. We found that structural water in the gels contributes to the elastic component of the QENS spectrum, while constrained water and free water contribute the quasi-elastic component. The quantitative analysis suggests that the three components vary for different samples and indicate the variance in the system porosity, which controls the mechanical properties of cement pastes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

The Boson peak in confined water: An experimental investigation of the liquid-liquid phase transition hypothesis

The Boson peak (BP) of deeply cooled confined water is studied by using inelastic neutron scattering (INS) in a large interval of the (P, T) phase plane. By taking into account the different behavior of such a collective vibrational mode in both strong and fragile glasses as well as in glass-forming materials, we were able to determine the Widom line that characterizes supercooled bulk water within the frame of the liquid-liquid phase transition (LLPT) hypothesis. The peak frequency and width of the BP correlated with the water polymorphism of the LLPT scenario, allowing us to distinguish the “low-density liquid” (LDL) and “high-density liquid” (HDL) phases in deeply cooled bulk water.Moreover, the BP properties afford a further confirmation of theWidom line temperature T W as the (P, T) locus in which the local structure of water transforms from a predominately LDL form to a predominately HDL form.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Pressure Effect on the Boson Peak in Deeply Cooled Confined Water: Evidence of a Liquid-Liquid Transition

We studied the boson peak in deeply cooled water confined in nanopores in order to examine the liquid-liquid transition (LLT). Below ~180 K, the boson peaks at pressures P higher than ~3.5 kbar are evidently distinct from those at low pressures by higher mean frequencies and lower heights. Moreover, the higher-P boson peaks can be rescaled to a master curve while the lower-P boson peaks can be rescaled to a different one. Moreover, these phenomena agree with the existence of two liquid phases with different densities and local structures and the associated LLT in the measured (P, T) region. Additionally, the P dependence of the librational band also agrees with the above conclusion.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Dynamic crossover in deeply cooled water confined in MCM-41 at 4 kbar and its relation to the liquid-liquid transition hypothesis

With quasi-elastic neutron scattering, we study the single-particle dynamics of the water confined in a hydrophilic silica material, MCM-41, at 4 kbar. A dynamic crossover phenomenon is observed at 219 K. We compare this dynamic crossover with the one observed at ambient pressure and find that (a) above the crossover temperature, the temperature dependence of the characteristic relaxation time at ambient pressure exhibits a more evident super-Arrhenius behavior than that at 4 kbar. Especially, at temperatures below about 230 K, the relaxation time at 4 kbar is even smaller than that at ambient pressure. This feature is different from many other liquids. (b) Below the crossover temperature, the Arrhenius behavior found at ambient pressure has a larger activation energy compared to the one found at 4 kbar. We ascribe the former to the difference between the local structure of the low-density liquid (LDL) phase and that of the high-density liquid (HDL) phase, and the latter to the difference between the strength of the hydrogen bond of the LDL and that of the HDL. Therefore, we conclude that the phenomena observed in this paper are consistent with the LDL-to-HDL liquid-liquid transition hypothesis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗