How to Assess the Relative Volume Change of Reversible Metal Hydrides Easily, Speedily and Concisely (Enough) with a Surprising Relevance for Clarifying Thermodynamic Tailoring Effects

2019 ◽  
Author(s):  
Roland Hermann Pawelke
Keyword(s):  
Hydrogen Storage ◽  
Volume Change ◽  
Reaction Pathway ◽  
Metal Hydrides ◽  
Relative Volume ◽  
Reaction Parameters ◽  
Relative Volume Change ◽  
Open Issue ◽  
Chemical Hydrogen Storage ◽  
Co Doped

<p>A practical way for assessing the relative volume change of reversible metal hydrides upon hydrogenation, based on the van’t Hoff reaction parameters, is outlined. Hitherto computational methods can provide that information only at a much higher level of complexity. By that method, the open issue of assessing the minimum pressure for complete [AlH<sub>4</sub>]-formation in Ti-doped NaAlH<sub>4</sub> is resolved and the nature of the additional reaction pathway in KH/Ti-co-doped NaAlH<sub>4</sub> elucidated. This work summarizes the essentials for the thermodynamic tailoring of metal hydrides in nine points and adds thus a central missing piece to the puzzle of understanding reversible chemical hydrogen storage in metal hydrides.</p>

scholarly journals How to Assess the Relative Volume Change of Reversible Metal Hydrides Easily, Speedily and Concisely (Enough) with a Surprising Relevance for Clarifying Thermodynamic Tailoring Effects

2019 ◽  
Author(s):  
Roland Hermann Pawelke
Keyword(s):  
Hydrogen Storage ◽  
Volume Change ◽  
Reaction Pathway ◽  
Metal Hydrides ◽  
Relative Volume ◽  
Reaction Parameters ◽  
Relative Volume Change ◽  
Open Issue ◽  
Chemical Hydrogen Storage ◽  
Co Doped

<p>A practical way for assessing the relative volume change of reversible metal hydrides upon hydrogenation, based on the van’t Hoff reaction parameters, is outlined. Hitherto computational methods can provide that information only at a much higher level of complexity. By that method, the open issue of assessing the minimum pressure for complete [AlH<sub>4</sub>]-formation in Ti-doped NaAlH<sub>4</sub> is resolved and the nature of the additional reaction pathway in KH/Ti-co-doped NaAlH<sub>4</sub> elucidated. This work summarizes the essentials for the thermodynamic tailoring of metal hydrides in nine points and adds thus a central missing piece to the puzzle of understanding reversible chemical hydrogen storage in metal hydrides.</p>

The Thermodynamic Way of Assessing Reversible Metal Hydride Volume Expansion: Getting a Grip on Metal Hydride Formation Overpotential

2021 ◽  
Author(s):  
Roland Hermann Pawelke
Keyword(s):  
Volume Change ◽  
Metal Hydride ◽  
Volume Expansion ◽  
Storage Systems ◽  
Metal Hydrides ◽  
Ideal Gas ◽  
Relative Volume ◽  
Hydride Formation ◽  
Chemical Hydrogen Storage ◽  
Insight Into

<p>The relative volume change of reversible metal hydrides upon hydrogenation is determined by means of the van’t Hoff reaction entropy and STP ideal gas parameters. This method allows insight into the requirements to metal hydride formation, outlined by example of Ti-NaAlH<sub>4</sub>. This work presents a timeless perspective on the sorbent phase thermodynamics of reversible chemical hydrogen storage systems.</p>

scholarly journals The Thermodynamic Way of Assessing Reversible Metal Hydride Volume Expansion: Getting a Grip on Metal Hydride Formation Overpotential

2021 ◽  
Author(s):  
Roland Hermann Pawelke
Keyword(s):  
Volume Change ◽  
Metal Hydride ◽  
Volume Expansion ◽  
Storage Systems ◽  
Metal Hydrides ◽  
Ideal Gas ◽  
Relative Volume ◽  
Hydride Formation ◽  
Chemical Hydrogen Storage ◽  
Insight Into

<p>The relative volume change of reversible metal hydrides upon hydrogenation is determined by means of the van’t Hoff reaction entropy and STP ideal gas parameters. This method allows insight into the requirements to metal hydride formation, outlined by example of Ti-NaAlH<sub>4</sub>. This work presents a timeless perspective on the sorbent phase thermodynamics of reversible chemical hydrogen storage systems.</p>

scholarly journals A Study of K/Ti-co-doped NaAlH4 on Thermodynamic Tailoring, Surplus Hydrogen Amount and Metal Hydride Molar Volume

2021 ◽  
Author(s):  
Roland Hermann Pawelke
Keyword(s):  
Hydrogen Storage ◽  
Molar Volume ◽  
Metal Hydride ◽  
Chemical Potential ◽  
Reaction Pathway ◽  
Ideal Gas ◽  
Point Of View ◽  
Phase Point ◽  
Desorption Enthalpy ◽  
Co Doped

A remarkable finding of metal hydride hydrogen storage is that substituting 4 mol % sodium by potassium in 4 mol % Ti-doped NaAlH<sub>4</sub> raises the reversible hydrogen storage capacity from 3.3 % w/w H to 4.7 % w/w H. This increase by 42% is concomitant with a slightly lower desorption enthalpy: intriguingly enough, it is substantially more hydrogen capacity at slightly less desorption enthalpy. The general solution to that puzzle has been already derived from a gas phase point of view, taking advantage of the equilibrium nature of the matter, which thus comes in terms of an ideal gas chemical potential. However, it is also interesting to investigate for the flipside effect in the sorbent phase, affecting molar volume. This paper elucidates by the example of K/Ti-co-doped NaAlH<sub>4</sub> the relation of doping modifications to surplus hydrogen amount and hydride molar volume, defining the term “reaction pathway” in this context, yielding the according figures.<br>

A large barocaloric effect and its reversible behavior with an enhanced relative volume change for Ni42.3Co7.9Mn38.8Sn11 Heusler alloy

2018 ◽  
Vol 741 ◽  
pp. 821-825 ◽  
Author(s):  
Xijia He ◽  
Yanru Kang ◽  
Shengxian Wei ◽  
Yuanlei Zhang ◽  
Yiming Cao ◽  
...  
Keyword(s):  
Volume Change ◽  
Heusler Alloy ◽  
Relative Volume ◽  
Relative Volume Change

scholarly journals The Master Key to the Problem of Reversible Chemical Hydrogen Storage is 12 kJ (mol H2)-1

2019 ◽  
Author(s):  
Roland Hermann Pawelke
Keyword(s):  
Energy Storage ◽  
Hydrogen Storage ◽  
Predictive Power ◽  
Storage Capacity ◽  
Reaction Pathway ◽  
Ideal Gas ◽  
Equilibrium Thermodynamics ◽  
Ideal Gas Law ◽  
Chemical Hydrogen Storage ◽  
The Ideal

<p>This article outlines a potent theoretical formalism illuminating the boundaries to reversible solid hydrogen storage based on the ideal gas law and classic equilibrium thermodynamics. A global picture of chemical reversible hydrogen sorption is unveiled including a thermodynamic explanation of partial reversibility. This is utilized to elucidate a multitude of issues from metal hydride chemistry: Highlights are why the substitution of a mere 4 mol % Na by K in Ti-doped NaAlH<sub>4</sub> raises the reversible storage capacity by 42 % and elaboration of the reaction pathway in (Rb/K)H-doped Mg(NH<sub>2</sub>)<sub>2</sub>/2LiH. The findings of this work allow for a change of paradigm towards the understanding of reversible chemical energy storage and provide a hitherto missing tool of ample analytic and predictive power, complementary to experiment.</p>

Non-invasive ultrasonic measurement of the relative volume change of the arterial wall - first in vivo trial

2008 ◽  
Author(s):  
Hannes Mogensen ◽  
Tomas Jansson ◽  
Kjell Lindstrom ◽  
Hans W. Persson ◽  
Magnus Cinthio ◽  
...  
Keyword(s):  
Volume Change ◽  
Arterial Wall ◽  
Relative Volume ◽  
Ultrasonic Measurement ◽  
Non Invasive ◽  
Relative Volume Change

scholarly journals Surveillance of small, solid pulmonary nodules at digital chest tomosynthesis: data from a cohort of the pilot Swedish CArdioPulmonary bioImage Study (SCAPIS)

2020 ◽  
pp. 028418512092310
Author(s):  
Carin Meltzer ◽  
Erika Fagman ◽  
Jenny Vikgren ◽  
David Molnar ◽  
Eivind Borna ◽  
...  
Keyword(s):  
Volume Change ◽  
Pulmonary Nodules ◽  
Average Diameter ◽  
Relative Volume ◽  
Digital Tomosynthesis ◽  
Operating Characteristics ◽  
Size Change ◽  
Measurement Variability ◽  
Nodule Size ◽  
Relative Volume Change

Background Digital tomosynthesis (DTS) might be a low-dose/low-cost alternative to computed tomography (CT). Purpose To investigate DTS relative to CT for surveillance of incidental, solid pulmonary nodules. Material and Methods Recruited from a population study, 106 participants with indeterminate solid pulmonary nodules on CT underwent surveillance with concurrently performed CT and DTS. Nodule size on DTS was assessed by manual diameter measurements and semi-automatic nodule segmentations were independently performed on CT. Measurement agreement was analyzed according to Bland–Altman with 95% limits of agreement (LoA). Detection of nodule volume change > 25% by DTS in comparison to CT was evaluated with receiver operating characteristics (ROC). Results A total of 81 nodules (76%) were assessed as measurable on DTS by two independent observers. Inter- and intra-observer LoA regarding change in average diameter were ± 2 mm. Calculation of relative volume change on DTS resulted in wide inter- and intra-observer LoA in the order of ± 100% and ± 50%. Comparing relative volume change between DTS and CT resulted in LoA of –58% to 67%. The area under the ROC curve regarding the ability of DTS to detect volumetric changes > 25% on CT was 0.58 (95% confidence interval [CI] = 0.40–0.76) and 0.50 (95% CI = 0.35–0.66) for the two observers. Conclusion The results of the present study show that measurement variability limits the agreement between DTS and CT regarding nodule size change for small solid nodules.

scholarly journals A review on imaging techniques and quantitative measurements for dynamic imaging of cerebral aneurysm pulsations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
L. B. Stam ◽  
R. Aquarius ◽  
G. A. de Jong ◽  
C. H. Slump ◽  
F. J. A. Meijer ◽  
...  
Keyword(s):  
Cerebral Aneurysm ◽  
Volume Change ◽  
Meta Analysis ◽  
Relative Volume ◽  
Dynamic Imaging ◽  
Accurate Estimation ◽  
Imaging Method ◽  
Rupture Risk ◽  
Relative Volume Change ◽  
Absolute Volume

AbstractMeasurement of intracranial aneurysm wall motion may refine the current rupture risk estimation. A golden standard for measuring aneurysm pulsation is lacking. The aim is to evaluate magnitudes of aneurysm pulsation as published in current literature. Embase and PubMed were searched for publications containing quantitative measures of cardiac-cycle related cerebral aneurysm pulsation (no date or language restrictions). Eleven studies were included, covering 197 unruptured and untreated cerebral aneurysms. Quantitative pulsation measurements were extracted from the studies. Characteristics of the study population and aneurysms were taken into account, as well as the imaging modality, scanning technique and data processing methods used. A meta-analysis was performed of studies with similar methodologies and individual IA measures and locations. The magnitude of the absolute volume pulsations varied between 14 ± 9 mm3 and 106 ± 123 mm3 and the mean relative volume change varied between 5 and 36%. The meta-analysis revealed a positive correlation between size and absolute volume change. The relative volume change in Basilar artery aneurysms seems smaller. No authors were contacted for original study data and articles only describing visual pulsations were excluded. The variation in methodologies impedes an accurate estimation of the magnitude of IA pulsations. Validation of aneurysm pulsation measurement is crucial prior to clinical studies evaluating IA pulsatility in relation to IA rupture risk. Prerequisite is a reliable and robust imaging method with high spatial and temporal resolution and standardization of the image analysis methods.

scholarly journals The Master Key to the Problem of Reversible Chemical Hydrogen Storage is 12 kJ (mol H2)-1

2021 ◽  
Author(s):  
Roland Hermann Pawelke
Keyword(s):  
Hydrogen Storage ◽  
Storage Capacity ◽  
Ideal Gas ◽  
Equilibrium Thermodynamics ◽  
Ideal Gas Law ◽  
Chemical Hydrogen Storage ◽  
Co Doped ◽  
Normative Role ◽  
The Ideal

<p>This article shows up the intrinsic thermodynamic boundaries to reversible mass transfer on basis of the ideal gas law and classic equilibrium thermodynamics in relation to chemical hydrogen storage. In the event, a global picture of reversible chemical hydrogen storage is unveiled, including an explanation of partial reversibility. The findings of this work help to clarify problems of metal hydride chemistry which otherwise are difficult if not impossible to solve in convergent manner, e.g. why the substitution of 4 mol % Na by K in Ti-doped NaAlH<sub>4</sub> raises the reversible storage capacity by 42 % or the way the dopants take effect in (Rb/K)-co-doped Mg(NH<sub>2</sub>)<sub>2</sub>/2LiH. This work's result is of a wider significance since based on two cornerstones of physical chemistry and particularly for the normative role of hydrogen electrodes to electrochemistry.</p>

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