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関連する概念動画

Entropy02:39

Entropy

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Salt particles that have dissolved in water never spontaneously come back together in solution to reform solid particles. Moreover, a gas that has expanded in a vacuum remains dispersed and never spontaneously reassembles. The unidirectional nature of these phenomena is the result of a thermodynamic state function called entropy (S). Entropy is the measure of the extent to which the energy is dispersed throughout a system, or in other words, it is proportional to the degree of disorder of a...
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Entropy01:18

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The first law of thermodynamics is quantitatively formulated via an equation relating the internal energy of a system, the heat exchanged by it, and the work done on it. A quantitative formulation of the second law of thermodynamics leads to defining a state function, the entropy.
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...
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Standard Entropy Change for a Reaction03:00

Standard Entropy Change for a Reaction

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Entropy is a state function, so the standard entropy change for a chemical reaction (ΔS°rxn) can be calculated from the difference in standard entropy between the products and the reactants.
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Phase-lead and Phase-lag Controllers01:22

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Understanding the working function of different types of controllers can be illustrated with practical analogies, such as adjusting a stereo's volume equalizer. Cranking up the bass involves a phase-lead controller, which functions as a high-pass filter, while increasing the treble uses a phase-lag controller, which acts as a low-pass filter. PD controllers, similar to high-pass filters, enhance the system's response to high-frequency components. PI controllers, akin to low-pass...
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Entropy and Solvation02:05

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The process of surrounding a solute with solvent is called solvation. It involves evenly distributing the solute within the solvent. The rule of thumb for determining a solvent for a given compound is that like dissolves like. A good solvent has molecular characteristics similar to those of the compound to be dissolved. For example, polar solutions dissolve polar solutes, and apolar solvents dissolve apolar solutes. A polar solvent is a solvent that has a high dielectric constant (ϵ...
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A living cell's primary tasks of obtaining, transforming, and using energy to do work may seem simple. However, the second law of thermodynamics explains why these tasks are harder than they appear. None of the energy transfers in the universe are completely efficient. In every energy transfer, some amount of energy is lost in a form that is unusable. In most cases, this form is heat energy. Thermodynamically, heat energy is defined as the energy transferred from one system to another that...
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関連する実験動画

Updated: Jan 24, 2026

Bulk and Thin Film Synthesis of Compositionally Variant Entropy-stabilized Oxides
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Bulk and Thin Film Synthesis of Compositionally Variant Entropy-stabilized Oxides

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高エントロピー合金電触媒の組成相制御

Sangmin Jeong1, Anthony J Branco1, Porvajja Nagarajan1

  • 1Department of Chemistry, University of Massachusetts Lowell, Lowell, Massachusetts 01854, United States.

Journal of the American Chemical Society
|January 22, 2026
PubMed
まとめ
この要約は機械生成です。

制御された相と形態を持つ高エントロピー合金 (HEAs) は,特殊な水素進化反応 (HER) 触媒を示す. これらの高度な材料は プラチナよりも高い耐久性と活性性を備えており 持続可能な電気触媒の道を開いています

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Last Updated: Jan 24, 2026

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科学分野:

  • 材料科学
  • 電気化学
  • ナノテクノロジー

背景:

  • 高エントロピー合金 (HEA) は,電触媒の調節可能な性質を提供します.
  • HEAの結晶相と形状を制御することは,反応部位を最適化するために不可欠です.

研究 の 目的:

  • AuPdFeCoNi HEAナノ粒子における混合fcc/bccとfcc相の好ましい安定化を,Au含有量を制御することによって実証する.
  • 特殊な水素進化反応 (HER) 触媒に起因する重要な構造的モチーフを特定する.

主な方法:

  • 異なるAu含有量のキナリウムAuPdFeCoNi HEAナノ粒子の合成
  • 電子,X線シンクロトロン,および表面技術を用いた調査.
  • 水素進化反応 (HER) の電気触媒試験

主要な成果:

  • fcc/bccとfccの相を優先して安定させた混合のAu含有量の体系的な制御.
  • HERにとって重要な特定の短距離 (数 Å) と中距離 (6-10 Å) の構造モチーフの特定
  • 優れた耐久性 (240時間) と高質量活性 (50A/mgPGM) を達成し,商用Pt/Cを上回っている.

結論:

  • HEAの形状に対する構造的制御は,金属の酸化状態と原子対の特徴に直接影響する.
  • 非貴金属含有量の高い頑丈で持続可能な電気触媒の設計のための新しい戦略を提供します.
  • HEAはHERの貴金属触媒の有望な代替品であることを示しています.