可调基准频率源的便携式石英晶体微天平分析仪

Portable Quartz Crystal Microbalance Analyzer with Adjustable Reference Frequency Source

基于差频方法开发了一款石英晶体微天平(Quartz crystal microbalance,QCM)仪器。测试结果表明,参考标准晶体与检测晶体的差频值在±10~±30kHz范围内,精确度小于0.0028%(差频数据的相对误差),准确度小于0.2825%(差频理论值与测量值误差)。本研究利用DDS数字发生器产生可调的基准频率源,使差频值在最优范围内,设计制作了基于Arduino单片机作为核心控制源的便携式石英晶体微天平分析仪。仪器拥有3.5寸液晶屏显示动态曲线,SD卡同步存储数据,可根据实验条件调节基准频率。气相与纯水中的平均频率漂移值小于0.13Hz/min与0.23Hz/min,表明仪器有较好稳定性。仪器差频响应与NaCl溶液浓度呈良好线性关系,相关系数为0.9891。不同粘度丙三醇的响应实验表明,Δf与(ηlρl)^1/2呈线性关系,说明仪器响应性良好。同时,本仪器还可与电化学工作站联用,用于Cu沉积过程在线检测,1ng的Cu引起0.61Hz频率的变化,为理论值的82.4%。

A quartz crystal microbalance (QCM) instrument was developed on the basis of difference frequency technique. The experimental data showed that the difference frequency between the reference crystal and the detection crystal was in the range of ±10 to ±30 kHz, the accuracy was less than 0.0028%(relative error of the difference frequency data) and the precision was less than 0.2825%(the difference frequency theoretical value and measurement value error). In this work, the direct digital synthesizer (DDS) digital generator was used to generate an adjustable reference frequency source, and the difference frequency value was within the optimal range. A portable quartz crystal microbalance analyzer was based on Arduino microcomputer. The instrument had a 3.5-inch LCD screen to display the dynamic curve, and the SD card synchronously stored the data. The reference frequency could be adjusted according to the experimental conditions. The average frequency drift values of gas phase and pure water were less than 0.13 Hz/min and 0.23 Hz/min , which indicated that the instrument had good stability. The linear relationship of the instrument to different density of sodium chloride was 0.9891. The response experiment with different viscosity glycerol showed that Δ f and (η lρ l)^1/2 had a linear relationship, which meant that the instrument had good responsiveness. At the same time, the instrument was used in combination with electrochemical workstations for on-line detection of Cu deposition process. The mass response value was 0.61 ng/Hz, which was 82.4% of the theoretical value.