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相关概念视频

Flame Photometry: Overview01:02

Flame Photometry: Overview

466
Flame photometry, also known as flame emission spectrometry, is a technique used for the qualitative and quantitative analysis of elements present in a sample using a flame as the source of excitation energy. The concept of flame photometry was realized in the early 1860s by Kirchhoff and Bunsen, who discovered that specific elements emit characteristic radiation when excited in flames. The first instrument developed for this purpose was used to measure sodium (Na) in plant ash using a Bunsen...
466
Molecular Weight of Step-Growth Polymers01:08

Molecular Weight of Step-Growth Polymers

2.1K
Step growth polymerization involves bi or multifunctional monomers. Bifunctional monomers react to form linear step growth polymers, whereas multifunctional monomers react to form non-linear or branched polymers.
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...
2.1K
Polymers: Molecular Weight Distribution01:10

Polymers: Molecular Weight Distribution

3.2K
For any given polymer, the weight average molecular weight (Mw) is higher than, if not equal to, the number average molecular weight (Mn). The only situation in which the weight average molecular weight and the number average molecular weight are equal is when a polymer consists only of chains with equal molecular weight. However, this never happens in a synthetic polymer, since it is difficult to control the polymerization process up to a molecular level with accuracy to a hundred percent.
3.2K
Flame Photometry: Lab01:16

Flame Photometry: Lab

213
In a flame photometer, when a solution like potassium chloride is aspirated into the flame, the solvent evaporates, leaving behind dehydrated salt. This salt dissociates into free gaseous atoms in their ground state. Some of these atoms absorb energy from the flame, leading to their excitation. The excited atoms return to the ground state, emitting photons at characteristic wavelengths. Because only electronic transitions are involved, the resulting emission lines are very narrow. The intensity...
213
Radical Chain-Growth Polymerization: Mechanism01:09

Radical Chain-Growth Polymerization: Mechanism

2.5K
The radical chain-growth polymerization mechanism consists of three steps: initiation, propagation, and termination of polymerization. The polymerization initiates when a free radical generated from the radical initiator adds to the unsaturated bond in the monomer. The unpaired electron of the free radical and one π electron in the unsaturated bond creates a σ bond between the free radical and the monomer. As a result, the other π electron in the unsaturated bond converts this...
2.5K
Free-Radical Chain Reaction and Polymerization of Alkenes02:35

Free-Radical Chain Reaction and Polymerization of Alkenes

7.7K
The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a repeating unit, while the terminal groups are considered insignificant. The average degree of polymerization represents the number of repeating units in the polymer molecule and is denoted by the subscript n.
7.7K

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相关实验视频

Updated: Jun 4, 2025

Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames
10:29

Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames

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一种混合物分数方法来预测聚合物燃烧.

Artem Shaklein1, Alexander Karpov1, Stanislav Trubachev2

  • 1Udmurt Federal Research Center, Russian Academy of Science, Ural Branch, T. Baramzinoi, 34, 426067 Izhevsk, Russia.

Polymers
|December 17, 2024
PubMed
概括

混合物分量方法对预测聚合物燃烧具有前景,但过于简单的热传递导致聚甲基甲酸 (PMMA) 的过度预测的火焰传播率. 未来的工作需要纳入多维热传输,以获得准确的结果.

关键词:
燃烧过程中的燃烧.运动机制的运动机制.混合物的分数部分.数字模拟的数字模拟.一个聚合物聚合物.

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Combustion Chemistry of Fuels: Quantitative Speciation Data Obtained from an Atmospheric High-temperature Flow Reactor with Coupled Molecular-beam Mass Spectrometer
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Combustion Chemistry of Fuels: Quantitative Speciation Data Obtained from an Atmospheric High-temperature Flow Reactor with Coupled Molecular-beam Mass Spectrometer

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Flame Experiments at the Advanced Light Source: New Insights into Soot Formation Processes
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相关实验视频

Last Updated: Jun 4, 2025

Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames
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Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames

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Combustion Chemistry of Fuels: Quantitative Speciation Data Obtained from an Atmospheric High-temperature Flow Reactor with Coupled Molecular-beam Mass Spectrometer
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科学领域:

  • 燃烧科学是一种科学.
  • 聚合物科学 聚合物科学
  • 计算流体动力学 计算流体动力学

背景情况:

  • 由于固体燃料的特性,预测聚合物燃烧是复杂的.
  • 精确的燃烧特性需要解决气体和固体相之间的热量和质量转移.
  • 在固体燃料上传播的火焰是燃烧中的关键现象.

研究的目的:

  • 应用混合物分数方法来预测聚合物材料的燃烧行为.
  • 为了模拟火焰在聚甲基甲酸 (PMMA) 上蔓延,作为一种代表性的聚合物.
  • 调查当前模型在捕获热量和质量转移动态方面的准确性.

主要方法:

  • 使用混合物分数方法与表化学相结合.
  • 模拟的逆流扩散火焰与燃料表面非常接近,以计算热量损失.
  • 采用了骨化学机制 (29种,33个反应) 进行气相燃烧.
  • 分析了以前关于PMMA火焰传播的研究的数值结果.

主要成果:

  • 混合物分量方法令人满意地解决了火焰尖的形状.
  • 在火焰区域观察到混合物分量的单调分布.
  • 该模型过度预测了固体燃料的热量流,导致火焰传播率高于实验数据.
  • 在火焰尖区域过度简化热传递被确定为不准确性的关键来源.

结论:

  • 混合物分数方法为描述聚合物燃烧提供了潜力.
  • 准确的预测需要将多维热传递纳入表化化学模型.
  • 需要进一步的研究来完善传热计算,以提高准确性.