The Experts below are selected from a list of 599922 Experts worldwide ranked by ideXlab platform
Karel Heremans - One of the best experts on this subject based on the ideXlab platform.
-
ftir spectroscopy study of the pressure dependent behaviour of 1 2 dioleoyl sn glycero 3 phosphocholine dopc and 1 palmitoyl 2 oleolyl sn glycero 3 phosphocholine popc at low degrees of Hydration
Chemistry and Physics of Lipids, 2013Co-Authors: Helge Pfeiffer, G Klose, Karel HeremansAbstract:High-pressure investigations of phospholipids at low degrees of Hydration are highly important due to the continuous interest in Hydration related phenomena. This is for instance the case when discussing differences between the molecular behaviour under hydrostatic or Hydration pressure, e.g. to characterise the structural and thermodynamic conditions that hold for the different theoretical approaches proposed in the literature. The stability of phospholipid aggregates in aqueous solutions is determined by a balance of attractive end repulsive forces as well as entropic and energetic interactions. The pressure-dependent variation of the frequency of molecular vibrations determined by FTIR spectroscopy might be an appropriate tool to study the nature of these interactions as well as of conformational changes for various degrees of Hydrations. The paper reports preliminary results for the stretching and bending vibration of the CH2 groups that are mainly situated in the hydrocarbon chains. In a Hydration range of about 2 water molecules per lipid in the case of DOPC and 6 water molecules for POPC, the pressure-dependent vibrations in the liquid crystalline phase change between red shift and blue shift. A further interesting parameter is the onset pressure for the correlation field splitting. It increases with deHydration, and it is assumed that the correlation field splitting does not only depend on the disorder related to the gauche conformer population in the hydrocarbon chains but also on the chain tilt in the gel phase.
Zhenghong Yang - One of the best experts on this subject based on the ideXlab platform.
-
Comparison of the Hydration Characteristics of Ultra-High-Performance and Normal Cementitious Materials
Materials (Basel Switzerland), 2020Co-Authors: Haiyun Zhou, Zhu Hongbo, Hongxiang Gou, Zhenghong YangAbstract:The Hydration mechanism of ultra-high-performance cementitious materials (UHPC) departs considerably from that of normal cementitious materials (NC). In this study, the strength, isothermal calorimetry, chemical shrinkage, X-ray diffraction (XRD), and thermogravimetry (TG) methods are used to determine the Hydration characteristics of UHPC and NC that contain silica fume (SF). A simple device was modified to test the chemical shrinkage for long-term growth, and the ultimate chemical shrinkage is obtained by semi-empirical formula fitting. It is found that the degree of Hydration of UHPC is significantly lower than that of NC. The Hydration kinetics analyzed using the Krstulovic-Dabic model shows that the Hydration process of NC is type NG-I-D, which is characterized by gentle and prolonged Hydration. However, the Hydration of UHPC is type NG-D with the distinguishing features of early sufficiency and later stagnation. The growth of the strength, exothermic evolution, and phase development of UHPC is decelerated as the Hydration process proceeds, which confirms the weak development tendency of Hydration at the later stage. In addition, the effect of SF on the Hydration of UHPC is minor, and the higher content of SF is beneficial to the Hydration at the later stage.
-
Hydration kinetics of tricalcium silicate with the presence of portlandite and calcium silicate hydrate
Thermochimica Acta, 2019Co-Authors: Liming Huang, Zhenghong YangAbstract:Abstract This work was designed to investigate the Hydration kinetics of C3S with portlandite and calcium silicate hydrate (C-S-H). The Hydration heat, T2 relaxation time and XRD of Hydration products were determined to evaluate the Hydration performance. C-S-H and CH present distinct influence on the early Hydration of C3S. C-S-H facilitates early Hydration of C3S, reduces the induction period and increases the Hydration rate at 10 or 20 °C, but CH prolongs the induction period. Up to 30 and 40 °C, the induction period is not affected by C-S-H or CH. The catalytic effect was evaluated by activation energy. C-S-H has the catalytic effect on nucleation of Hydration products but CH exploits the opposite effect. CH presents a positive effect on the structure development of Hydration products to gain a denser skeleton before 10 h. Moreover, the Ca/Si ratio of Hydration products is altered for the presents of CH and C-S-H.
Xuefeng Song - One of the best experts on this subject based on the ideXlab platform.
-
effects of superplasticizers on the carbonation resistance of c3s and c3a Hydration products
Construction and Building Materials, 2012Co-Authors: Chen Shi, Xuefeng SongAbstract:Abstract The effects of three superplasticizers, Polycarboxylic acid superplasticizer (PA), Naphthalene sulphonated superplasticizer (NS) and Aminosulfonic acid based superplasticizer (AS), on the carbonation and crystal morphology of tricalcium silicate (C3S) and tricalcium aluminate (C3A) Hydration products were investigated. These three superplasticizers can improve the carbonation resistance of C3S and C3A Hydrations. However, at the appropriate dosages, they have different performance in improving the anti-carbonation ability of C3S and C3A Hydrations. The mechanism behind this phenomenon was investigated by analyzing the quantity and crystal morphology of calcium carbonate (CaCO3), calcium hydroxide (CH) and ettringite using thermogravimetric analysis (TGA) and Stereoscan Electron Microscopic Photograph (SEM). The formations of calcium complex with superplasticizers are also estimated by means of X-ray photoelectron spectroscopy (XPS). These three superplasticizers can change the size, amount and orientation of Hydrations. Thus, the anti-carbonation ability of the Hydrations was improved.
Helge Pfeiffer - One of the best experts on this subject based on the ideXlab platform.
-
ftir spectroscopy study of the pressure dependent behaviour of 1 2 dioleoyl sn glycero 3 phosphocholine dopc and 1 palmitoyl 2 oleolyl sn glycero 3 phosphocholine popc at low degrees of Hydration
Chemistry and Physics of Lipids, 2013Co-Authors: Helge Pfeiffer, G Klose, Karel HeremansAbstract:High-pressure investigations of phospholipids at low degrees of Hydration are highly important due to the continuous interest in Hydration related phenomena. This is for instance the case when discussing differences between the molecular behaviour under hydrostatic or Hydration pressure, e.g. to characterise the structural and thermodynamic conditions that hold for the different theoretical approaches proposed in the literature. The stability of phospholipid aggregates in aqueous solutions is determined by a balance of attractive end repulsive forces as well as entropic and energetic interactions. The pressure-dependent variation of the frequency of molecular vibrations determined by FTIR spectroscopy might be an appropriate tool to study the nature of these interactions as well as of conformational changes for various degrees of Hydrations. The paper reports preliminary results for the stretching and bending vibration of the CH2 groups that are mainly situated in the hydrocarbon chains. In a Hydration range of about 2 water molecules per lipid in the case of DOPC and 6 water molecules for POPC, the pressure-dependent vibrations in the liquid crystalline phase change between red shift and blue shift. A further interesting parameter is the onset pressure for the correlation field splitting. It increases with deHydration, and it is assumed that the correlation field splitting does not only depend on the disorder related to the gauche conformer population in the hydrocarbon chains but also on the chain tilt in the gel phase.
G Klose - One of the best experts on this subject based on the ideXlab platform.
-
ftir spectroscopy study of the pressure dependent behaviour of 1 2 dioleoyl sn glycero 3 phosphocholine dopc and 1 palmitoyl 2 oleolyl sn glycero 3 phosphocholine popc at low degrees of Hydration
Chemistry and Physics of Lipids, 2013Co-Authors: Helge Pfeiffer, G Klose, Karel HeremansAbstract:High-pressure investigations of phospholipids at low degrees of Hydration are highly important due to the continuous interest in Hydration related phenomena. This is for instance the case when discussing differences between the molecular behaviour under hydrostatic or Hydration pressure, e.g. to characterise the structural and thermodynamic conditions that hold for the different theoretical approaches proposed in the literature. The stability of phospholipid aggregates in aqueous solutions is determined by a balance of attractive end repulsive forces as well as entropic and energetic interactions. The pressure-dependent variation of the frequency of molecular vibrations determined by FTIR spectroscopy might be an appropriate tool to study the nature of these interactions as well as of conformational changes for various degrees of Hydrations. The paper reports preliminary results for the stretching and bending vibration of the CH2 groups that are mainly situated in the hydrocarbon chains. In a Hydration range of about 2 water molecules per lipid in the case of DOPC and 6 water molecules for POPC, the pressure-dependent vibrations in the liquid crystalline phase change between red shift and blue shift. A further interesting parameter is the onset pressure for the correlation field splitting. It increases with deHydration, and it is assumed that the correlation field splitting does not only depend on the disorder related to the gauche conformer population in the hydrocarbon chains but also on the chain tilt in the gel phase.