Water also has a glass transition? Tg and how much? Do not worry, listen to how bigwigs say
Water has gas, liquid, and solid states, it is probably that we grew to know scientific knowledge. However, in the universe, there is another major water is present in the form, i.e. a glass of water. It is a slow accumulation of water molecules from the vapor state to the formed matrix cold dust particles, and finally gathered to a larger class of a comet objects. A glass of water is heated to above the glass transition temperature, it undergoes a transition from the amorphous solid to a viscous liquid. Obtained in liquid form is thermodynamically different from the normal liquid water, and exhibit different temperature dependence of the viscosity. Laboratory obtained glassy water there are two methods, one is a glass of water by direct liquid aerosol droplets produced super quenching technique, referred to as ultra-quenching water glass (HQGW) ; other ice crystal by high pressure water collapse into an amorphous high density, and then annealing 100K obtained under atmospheric pressure, known as low density amorphous water (LDAW) . Both forms resulting viscous liquid having different kinetic stability. (Water, A and B) Since there is water glass, then the glass transition temperature (Tg) of natural scientists is the focus of attention. At this temperature, the molecular relaxation occurs on a time scale of minutes. The combined result calorimetry obtained with other methods, researchers have widely used water Tg = 136 K. However, nano-falling ball viscosity test and isotope exchange experiments the values of the above disputed. When the crystallization temperature was raised to a temperature of 155K, the two experiments was not observed with water a viscous liquid behavior. So, how much water the Tg in the end? First, the question: water Tg of at least the crystallization temperature, of Tg = 165 ± 5 K. In 2001, the US research group at Arizona State University Professor Angell entitled On Nature \”The Glass Transition of Water, Based on Hyperquenching Experiments\” the report pointed out: If the water is higher than the Tg crystallization temperature at a normal time scale, these observations are then slightly different, and two properties a and B accidental presence of liquid water is understandable. Researchers over the new measurement results of quenched molecules in the liquid, which analyzes the original and their exothermic effect similar to that observed associated with the silicate glass and metalProperties, proved that when Tg = 165 ± 5 K, the experimental results can be better explained. Figure 1: The Tg temperature axis scale, ultra compare quenched glass phase excess heat capacity (enthalpy relaxation exothermic) and quench water over the excess heat capacity of the body is formed. Wherein the range of the bulk glass body formed from the \”hard\” (silicate) to \”Fragile\” (OTP), are 106 to 107 K / min rate of hardening. Note that in the supercooled state can be observed, the behavior of all the liquid is water the most brittle. The researchers used temperature Tg axis scale various glass body formed excess heat capacity to collect the drawings, wherein the ultra-quenching a glass transition temperature of the cold water using generally accepted value of 136K. For other glass formers peak, excess heat capacity (heat or enthalpy relaxation) is much lower than Tg. In addition, before the temperature reaches 1.1Tg, onset, enthalpy has been completely restored. As shown, the glass has been completely released in other super quenched enthalpy 1 becomes trapped viscous liquid, glassy structure water still slowly relaxed. When crystallization occurs at 155 K, most of the excess heat capacity remains. Thus it can be concluded: water in the vicinity of the liquid is not fully, i.e. Tg 150K> 150K. However, if Tg = 165K (curve F.), Excess water is Cp may overlap with other curves of FIG. And, in the range of 165K ± 5K, (i) a hydrogel droplet glass nano inclusions of water measured transition temperature, and (ii) using the entropy – correlation viscosity from below the crystallization temperature water glass viscosity extrapolated outer transition temperature. The results of the above super-quenched glassy water Tg = 165K ± 5K provides favorable support. For previously observed in the DSC thermal effect is considered to be weakly silicate glass transition state, the authors believe that freeze Bjerrum defects similar to non-diffusion defect, is brought Bjerrum defects (crystal) ice dielectric relaxation Yu. These relaxation dielectric relaxation time than the glass transition fast. Second, make up a knife: glass transition of water can not be directly detected In 2004, Angell associate professor and professor of the University of Aalborg, Denmark expedition to a mountain, then entitled on Nature \”Clarifying the glass-transition behaviour of water bycomparison with hyperquenched inorganic glasses \”expresso. In this article, the author observed after 136 K ultra-quenching annealing glassy water absorbing conducted intensive studies detailed characteristics calorimetry super quenched inorganic glass display, in . no crystals before heating to reach the glass transition temperature of the glassy behavior results with water were compared and found small endothermic effect – such as glass transition due to the endothermic effect of the water – just more real glass transition \”shadow\” occurs at high temperatures, thus confirming the glass transition of water can not be directly detected Conclusion Figure 2: comparison of aging, a DSC heating scan super quenching mineral glass with respect HQGW and the broken line equivalent water ASW DSC heating scan .b we propose is based on partial crystallization from water samples cut in the scan starts at a temperature Tc labeled or slightly higher Tg of mineral glass, and onset Tg the ratio was 0.80. the same applies to water ratio of Tg, shadow, get a \”real but hidden\” Tg 169 K, however, this ratio will depend on the fragility of the system, so the water is not hidden Tg estimate , can better estimate determined by other methods. HQGW investigated the sample similarly treated with ultra-quenching glass (HQG) thermal behavior, i.e. after, at various annealing temperatures far below Tg 90 min, to standard speed heating scan. the results show that, when the annealing temperature (Ta) is high enough, it produces a scanning line heating heat absorbing portion, which appears to be starting temperature fixed, but depends on the annealing temperature of the peak under the specified annealing time. 2, the authors selected one scan, and in the literature showing a scanning endotherm attributed to the glass transition of water are compared to obtain a striking similarity, indicating that water obtained the glass transition having the same shape (the same small and ACp) scanning line is possible, the water here is merely by properly annealed HQGW obtained. authors named \”shadow\” glass transition, transition temperature Tg, shadow. for the past misunderstanding, the authors point out, for mineral-resistant crystallized glass, a Tg of Ta may be arbitrarily close to the standard, but in the water, when the time ta = 90 min, Ta tries to rise far above 130 KWill cause crystallization. This feature explains why the shadow of the glass transition will be as real change. Further, the micro-drops of water deposited at different substrate temperatures and vitrified. Calorimetry showed deposited at 130 K without absorbing water, and deposited at 140 K samples endotherm occurs, resulting Tg of 141K. This results HQG of Tg, similar shadow behavior. Studies have shown that peak onset temperature Tg alkylene same annealing temperature. This correlation seems to apply to a glass of water and the deposition annealed at higher temperatures. Two kinds of behavior allows HQG experiments closely reproduce the behavior HQGW annealing, however, is only the endothermic experimental glass glass transition is a true \”shadow.\” These findings strongly suggest that water absorbs heat 136 K is only true of the glass transition of a \”shadow\”, he confirmed earlier assertion that the real Tg of water can not be directly, except through some kind of scale method. The glassy water endothermic effect due to the controversial long-term annealing effect rather than Tg, can solve several inconsistencies found in the glassy phase behavior of water: Water is considered to be close to Tg brittle liquid, but the measured does not meet the activation energy; Tg at a very weak change in Cp, 14 times smaller than expected; abrupt change in Tg and aqueous LiCl glycol; and the like. Third, the reverse: the water can be measured Tg = 136K, not \”shadow\” Tg Angell professor to present the water was 165 ± 5 K, will be interpreted as a recognized 136K Tg, shadow, it seems to be from both sides overturned glassy water Tg = 136K of recognized value. However, in 2005, University of Innsbruck, Austria, etc. Ingrid Kohl published in Nature entitled \”Glass transition in hyperquenched water?\” Article, he has questioned. Analysis by DSC heating displayed deposited at 140 K showed super quench water over a viscous liquid, it depends on the cooling rate limiting structure, as for the liquid – as predicted by the theoretical analysis of the glass transition. Results and glass – liquid transition onset temperature (Tg) within the same range of 136K, indicates that the measured properties of the liquid may be clarified anomalous properties of cold water. FIG. 3: 140K 140K or less super-quenchedLiquids relaxation water. The top curve: 140 K after deposition of 16 minutes, unannealed influence over the cooling rate of the cold water quench sample of DSC measurement record then warmed to 30 K min-1; a cooling rate from 0.2 K min-1 increased 2.0 K min-1 and then to 5.0 K min-1, corresponding scan line, respectively by a solid, dotted and dashed lines represent. Noting the endothermic step height increases the cooling rate decreases. Bottom curve: the same samples were tested under the same conditions after annealing at 130 K 90min. It noted that the cooling rate influence disappeared. The size of the droplets of micron been quenched on a substrate of 140 K, and immediately 0.2,2.0 min-1 rate of 5.0 K and cooled to 77 K. Then DSC scans recorded show highly endothermic peak (ACp) increases as the cooling rate decreases. This effect disappears prepared in the same manner and the sample was cooled at 130K, but are annealed in the DSC scan. ACp annealed samples increased (FIG. 3) comprising contributions to the overshoot, the water in the lower Tg \”real\” ACp will increase, approaching obtained at 5.0 K min-1 is cooled from about 0.7 J K-1 mol- value of 1. ΔCp consistent low value seems too cold and getting \”hard\” behavior. This finding supports the liquid water cooling from ambient temperature to a supercooled state assumptions and brittle glass – transition hard. Finally, the authors pointed out that the experimental results and Yue and Angell hypothetical \”shadow\” peaks inconsistent because their criterion is the starting temperature peak annealing temperature the same. However, this was not observed in FIG. 3, because the Tg does not vary with annealing temperature. Fourth, the response: the new data does not prove that Tg = 136K face of challenge, Angell, Professor and Associate Professor Yue expedition published in the same journal entitled \”Glass transition in hyperquenched water (reply)?\” Response. The authors note that the experimental results Kohl, who is also consistent with their conclusions.
Kohl et al., New data suggest that, if the report is extremely weak endothermic step (or peak) is a (glass type) relaxation, then even weaker than previously assumed – the background only than the vibration 3% higher, only SiO2 (known \”hardest\” liquid) in quarter-strength exhibited by the phenomenon. If the glass transition, then it is a one-component system is recorded in the broadest, ΔTg / Tg = 0.11. Enhanced endothermic peak Kohl and other slow cooling from 140K to support the main relaxation is envisaged, however, the authors point out, this is the expected behavior of the peak pre-annealing, that is the interpretation of weak endothermic. After all, the easiest way to understand the pre-annealing peak (or \”shadow\” glass transition) is to present it as a short relaxation time component non-exponential relaxation of macro glass annealing ( \”micro-glass\”) of reinforced glass transition. Similar scan shown in FIG. If it is interrupted by crystallization at a temperature of 830 K, as ultra-quenching water glass as an interrupt by crystallization at 155 K, it will have the appearance of FIG. 4 in FIG. 3. Scanning of quench water over the maximum ΔCp (0.6 J K-1 mol-1) is close to curve 1 of 5 K Kohl et cooling min-1 ΔCp (0.7 J K-1 mol-1). Illustration Figure 1 shows these peaks relative to pre-operative glass transition weak degree. For \”shadow\” Kohl and other assertions peak starting temperature should be the same as the annealing temperature, the authors believe that this is not a core standard, as shown in Figure 4 and other documents. Pre peak onset temperature is significantly can appear anywhere, depending on the quench portion of the energy is not relaxed after annealing. When the glassy substance was not no enthalpy relaxation, slow cooling or annealing should result in increased Tg. However, in FIG. 3, the super-cooled quench slowly 140K glassy water collected without increasing Tg. In summary, the authors believe, after Kohl and other new measurement does not solve the water problem in the 136K annealing endothermic steps (peak). Summary: \”The good is like water which benefits all things without struggle, atOf all evil, and so few on the road. \”Water is one of the most abundant substances on Earth, is the basis for the existence of life on Earth. The water in the world is mysterious, nature and status of many scientists now face the water, still poorly understood, even as progress of science and technology and in-depth study of the mysteries about water but more and more. up to now, for the glass transition temperature Tg of water range, scientists are still debating. and that perhaps is the science of fun. [123 ] reference source: