液体温度对声致发光强度的影响

【作者】 朱秀丽；

【导师】 牛勇； 张明铎；

【作者基本信息】 陕西师范大学 ， 声学， 2008， 硕士

【摘要】 超声波是一种机械波,具有振动和传递能量的性质,其最显著的特征之一就是传播的方向性好,穿透力强,在固体和液体中传播时能量的衰减小。目前,超声技术已经被广泛地应用于清洗、焊接、加工、提取、检测、医学等各个领域。超声空化是超声技术被应用的基础,其中由超声空化引起了一种将声能转化为光能的现象一声致发光。目前,这种现象倍受科学界的关注。声致发光是指在超声场中,液体中的空化气泡随着声场变化而膨胀和收缩,将声能高度集中,产生发光现象。声致发光中气泡的运动将低能量密度的声能转化为高能量密度的光能。声致发光现象按照气泡的数目分为多泡声致发光和单泡声致发光两种类型。由于声致发光特殊的物理、化学效应,其在物理、化学、生物、医学等领域中有着广泛的应用前景。大量的研究表明,空化气泡在崩溃的瞬间产生的高温、高压是声致发光产生的主要原因,气泡内产生的高温、高压与超声压强、频率、液体的温度、气泡内气体的含量及气体的性质等条件有关,当这些条件改变时,声致发光强度就会发生显著的变化。目前,关于声致发光方面的报道大多数是关于其应用方面。对于超声压强、频率、液体的温度等对声致发光强度的影响报道较少,尤其是温度对声致发光的影响,而且大部分是国外的报道。本文从理论和实验两个方面对声致发光的温度效应进行研究,主要包括以下几部分内容:1.对声致发光理论进行了探讨,研究表明,超声空化是声致发光的基础。2.研究了增强声致发光的两种化学试剂—光泽精和鲁米诺。实验表明,光泽精比鲁米诺在增强声致发光方面有更好的效果。3.研究了各个频率下超声功率密度与声致发光强度的关系,从而找到了各个频率下声致发光强度最大时所对应的功率密度。4.研究了在一定的频率和超声功率条件下,声致发光强度随温度的变化关系。研究表明温度对声致发光有很大的影响。对本实验的光泽精溶液而言,当温度低于30℃～35℃左右时,光强随着温度的升高而升高,但变化比较缓慢:当温度超过30℃～35℃左右时,光强随着温度的升高而降低,开始时变化也是比较缓慢,但当温度超过50℃时,随着温度的升高,液体的发光强度急剧下降,当温度达到60℃左右时发光已经变的非常困难,当温度达到65℃时,已经几乎看不见光了。多泡声致发光的这种明显的温度效应主要是由超声空化的温度效应引起的,液体的温度对空化有着重要的影响,液体的温度升高,一方面将使液体表面张力系数及粘滞系数下降,使空化容易发生:但是由于温度升高,蒸汽压将增大,从而会使空化强度减弱。另一方面,当溶液温度升高后,其中溶解的气体量下降,当超声波辐射溶液时,将导致空化核数目下降,造成声化学产率下降。对于具体的声致发光强度与温度之间的变化关系原因还需进一步的探讨。更多还原

【Abstract】 Ultrasonic is a Mechanical Wave, which can transfer power and has good directivity, better penetrating power and little attenuation. At Present, Ultrasonic has been extensively applied in many fields. Such as ultrasonic cleaning, ultrasonic welding, ultrasonic machining, ultrasonic extraction, ultrasonic testing and ultrasonic medical, etc. Acoustic cavitation is the origin of sonoluminescence. Ultrasonic cavitation induces all kinds of physical, chemical and biologic effects during these applications. Ultrasonic cavitation induces sonoluminescence, which becomes the focus of the scientific community.In ultrasound field, highly energy concentrated in cavitation bubbles will induce luminescence with changing of acoustic field, which phenomenon is called sonoluminescence. In the sonoluminescence, the movement of the bubbles converts low-energy of sound to high-energy of luminous. Sonoluminescence has two types, which is single-bubble and multiple-bubble sonoluminescence according to the amount of bubble.Sonoluminescence has wide application prospects in the areas of physics, chemistry, biology, medicine, etc. As it has special origin of physics and chemistry. The study showed that high temperature and high pressure produced by instant collapse of cavitation bubbles is the main causes of sonoluminescence. The high temperature and high pressure is related to ultrasonic pressure, frequency, liquid temperature and the content of gas. The light intensity will change when theses changed. At present, the report of sonoluminescence is mainly about its application. About the relation between the light intensity and ultrasonic pressure, frequency, liquid temperature and the content of gas is little, temperature is especially less, and some about report is only in foreign.The temperature effect of sonoluminescence has been studied by this paper at theory and experiment. The main contents have follows.1. The theory of sonoluminescence has been studied .The study showed that acoustic cavitation is the origin of sonoluminescence.2. The two kinds chemical reagent (Luminol and Lucigenin) that can enhance sonoluminescence have been studied .Experiments showed that Lucigenin is better than Luminol.3. The relation of acoustic pressure and luminous intensity has been studied. Ultrasonic pressure of maximum intensity at every ultrasonic frequency has been found.4. The relation of luminous intensity and temperature at the same acoustic pressure and frequency has been studied. The study showed that temperature has great influences to the luminous intensity. This experiment showed that luminous intensity increases with increasing of temperature about 30～35℃, but this changes is very slowly. Luminous intensity decreases as temperature increase at about 30～35℃. This change is very quick at about 50℃. The production of light is very difficult at about 60℃. There nearly has no luminous when liquid temperature above about 65℃.About the reason of sonoluminescence, temperature effect is mainly ultrasonic cavitation. Temperature has more Influence on ultrasonic cavitation. Liquid’s temperature increasing, one side, liquid surface tension and viscosity coefficient will decreasing, these are more liable to cavitation. But the vapor compression will increase, which are not liable to ultrasonic cavitation. On the other side, the increasing of temperature, the dissolved gas content will decrease. The number of cavitation nuclear will decline, sonochemistry yield will decrease. The cause of relation of luminous intensity and temperature will need further study.更多还原