氦单质在极低温度下由气态氦转变为液态氦。由于氦原子间的相互作用(范德华力)和原子质量都很小,很难液化,更难凝固。富同位素4He的气液相变曲线的临界温度和临界压强分别为5.20K和2.26大气压,一个标准大气压下的温度为4.215K.在常压下,温度从临界温度下降至绝对零度时,氦始终保持为液态,不会凝固,只有在大于25大气压时才出现固态。 在2.18K时会有明显的性质改变,如获得超流性,被称作He II,来与普通的液氦(He I)区别开。
确实不是液氮助阵的~是液氦(liquid helium) 液氦的沸点是4.2k(零下269摄氏度)~而液氮的沸点只有77.36K(-195.6 ℃)转为固态63.2K(熔点:-209.8℃)
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...(例如10 K与50 K之间)的温度水平上,从而使其 在高场强情况下具有较高的载流能力。这种温度水平明显高于4.2K, 4.2 K 为液氦(LHe)的沸点温度,临界温度Te相对较低的已知金属超导材料(即 所谓的低温材料或LTS材料)就是用液氦冷却的。
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液氦容器 [低温] liquid helium vessel
液氦存储器 liquid ehelium storage vessel
液氦温度 liquid helium temperature
液氦冷却 liquid helium cooling
液氦循环系统 liquid helium circulatory ; Circulatory system of liquid helium
液氦罐 liquid helium pot
外挂式液氦自循环杜瓦 Reliquefier
液氦恒温槽 [低温] liquid helium thermostatic bath
朗道液氦理论 [低温] Landau liquid helium theory
The Neutral Beam Injection (NBI) system requires a clean high vacuum environment. The liquid helium cryocondensation pump with high pumping speed is an ideal vacuum obtain device.
中性束注入系统要求有洁净的动态高真空环境,大抽速液氦冷凝泵是满足此要求的理想真空获得设备。
参考来源 - 中性束注入系统液氦输送管真空多层绝热研究·2,447,543篇论文数据,部分数据来源于NoteExpress
除了轻过空气外,在科学上液氦的作用简直令人难以置信。
In addition to being lighter than air, Helium is incredibly useful, scientifically, in its liquid form!
对于海外运输,液氦IS O罐可以从拖车底座上移动下来。
Liquid helium ISO tanks may be removed from the trailer chassis for overseas shipments.
实验利用了一种单层离子势阱,并将其浸在液氦浴中冷却到零下269摄氏度。
The experiments were made possible by a novel, one-layer ion trap cooled to minus 269 C (minus 452 F) with a liquid helium bath.
We use a liquid helium. And so in order to make a liquid helium, you can't take helium at room temperature and do this, because if you did, you would just heat it up, because the room temperature is above the inversion temperature, so Joule-Thomson would heat up the helium.
为了得到液氦,不能再常温,做这个实验,否则就是加热氦气,因为室温高于它的转变温度,所以焦耳-汤姆孙,实验会加热氦气。
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