电弧加热产生的等离子体射流，因具有较高的温度和热流密度，被广泛应用于高工艺速率要求的材料加工和处理领域以及难熔材料的增材制造。为了提高能量利用效率，通常采用Ar/H₂混合气体作为工作气体。然而着眼未来的地外太空先进制造可能需要更好地利用原位资源，例如二氧化碳（CO₂）是火星大气的主要组成部分。深入认知并发挥CO₂的潜在价值具有重要意义。同时，CO₂也是导致全球气候变暖的关键温室气体。将CO₂作为电弧放电的工质应用到材料工艺中，可能是一种有效利用CO₂资源、技术可行且经济合理的方法。因此，本学位论文采用实验研究和理论模拟相结合的方法，对以Ar/CO₂作为工作气体的直流电弧等离子体射流特性进行了系统研究和分析。主要研究内容和结论如下：

1）基于质量作用定律计算了Ar/CO₂等离子体组分及质量密度、比焓、内能、定压比热等热力学参数。分析了CO₂对等离子体热力学参数的影响规律，结果表明：CO₂的加入提高了Ar等离子体的比焓、内能和定压比热。利用COMSOL对转移式直流电弧放电进行模拟，获取了直流电弧发生器腔室内的等离子体放电状态。发现CO₂相较于Ar等离子体而言，其热收缩效应更为显著。这一现象导致了电弧的明显收缩，并且引发了电弧轴线上等离子体温度、速度以及电导率的显著升高。

2）搭建直流Ar/CO₂等离子体实验平台，对等离子体放电特性展开研究。分析了等离子体发生器的伏安特性以及影响等离子体射流状态的弧电压波动现象。结果表明：弧电压随弧电流增大而增大；弧电压波动模式随CO₂加入呈现出再击穿特征，并且随着CO₂在混合气体中比例的增加，弧电压波动的频率下降，波动幅值有所提高。

3）采用发射光谱诊断为主的方法系统研究及分析Ar/CO₂等离子体射流。相较于纯氩等离子体，随着CO₂在混合气体中比例的增加，射流长度逐渐变长，等离子体射流的电子激发温度升高、电子数密度减小。等离子体发生器的比焓和热效率也有显著提高。该结果表明，采用Ar/CO₂混合气体工质，可提高材料加工的范围，也验证了未来外太空的先进制造利用原位资源的可行性。

Plasma jets produced by arc heating are widely used in material processing and treatment fields requiring high process rate and additive manufacturing of refractory materials due to their high temperature and heat flux characteristics. In order to improve the efficiency of energy utilization, Ar/H₂ gas mixture is usually used as the working gas. However, advanced manufacturing in outer space with an eye to the future may require better use of in-situ resources, such as carbon dioxide (CO₂), which is a major component of the Martian atmosphere. It is of great significance to deeply understand and play the potential value of CO₂. At the same time, CO₂ is also a key greenhouse gas that causes global warming. Using CO₂ as the working medium of arc discharge in the material process may be an effective, technically feasible and economical method to utilize CO₂ resources. Therefore, this thesis adopts the method of combining experimental research and theoretical simulation to systematically study and analyze the characteristics of DC arc plasma jet using Ar/CO₂ as working gas. The main research contents and conclusions are as follows:

1) Based on the law of mass action, the Ar/CO₂ plasma components and thermodynamic parameters such as mass density, specific enthalpy, internal energy, and constant pressure specific heat were calculated. The influence law of CO₂ on the thermodynamic parameters of the plasma was analyzed, and the results showed that the addition of CO₂ increased the specific enthalpy, internal energy, and constant-pressure specific heat of the Ar plasma. The plasma discharge state in the chamber of the DC arc generator was obtained by simulating the transferred DC arc discharge using COMSOL. The thermal contraction effect of CO₂ was found to be more significant compared to Ar plasma. This phenomenon leads to a significant contraction of the arc and triggers a significant increase in the plasma temperature, velocity, and conductivity along the arc axis.

2) The DC Ar/CO₂ plasma experiment platform was established to study the plasma discharge characteristics. The volt-ampere characteristics of the plasma generator and the arc voltage fluctuation affecting the plasma jet state are analyzed. The results show that the arc voltage increases with the increase of arc current. With the addition of CO₂, the arc voltage fluctuation pattern presents a re-breakdown characteristic, and with the increase of the proportion of CO₂ in the gas mixture, the arc voltage fluctuation frequency decreases and the fluctuation amplitude increases.

3) The Ar/CO₂ plasma jets are systematically studied and analyzed by means of emission spectrum diagnosis. Compared with pure argon plasma, with the increase of CO₂ in the mixed gas, the jet length gradually becomes longer, the electron excitation temperature increases, and the electron number density decreases. The specific enthalpy and thermal efficiency of the plasma generator are also significantly improved. The results show that the use of Ar/CO₂ mixed gas working medium can improve the scope of material processing, and also verify the feasibility of using in-situ resources for advanced manufacturing in outer space in the future.