The rate controlling step of hafnium hydride formation governing the overall reaction using powder-type hafnium specimens was investigated from the relation between pressure and reaction rate under the pressure of 200~770 torr. For a constant reacted fraction, dependence on pressure of the absorption rate tend to be proportional to the second-power of pressure at the early stage of reaction and gradually to the first-power of pressure at the later stage of reaction. These results indicate the mass transfer of hydrogen molecule to arrive at the surface of hafnium powder specimen is the rate controlling step at the early stage of reaction, and the rate controlling step changed to is chemisorption at the surface of hafnium powder specimen at the later stage of reaction.
The mechanism of hydrogen evolution from the hafnium - hydrogen solid solution was studied by the thermal analysis method using a gas chromatograph. The diffusion coefficient of hydrogen in disc - type hafnium specimen was determined from the slope of the plot of $Ln(1-Q_t/Q_\infty)$ as the function of time t for a fixed thickness 1. The activation energy for diffusion of hydrogen in hafnium was determined from the relation between its diffusion coefficient and temperature. The activation energy for hydrogen trapping at grain boundaries was obtained from the dependence on heating rate of peak temperature T for maximum hydrogen evolution rate. The typical curve of hydrogen evolution with heating rate consist of two evolution peaks. It was inferred that the first peak of hydrogen evolution is attributed to diffusion of hydrogen through grain boundaries and the second peak to bulk diffusion of hydrogen.
Dependence on temperature and pressure of permeation rate of hydrogen through type 304 stainless steel and effects of its oxide film on permeation rate were investigated. Hydrogen permeation through type 304 stainless steel showed a half-power pressure dependence under a pressure range of 0.26~1atm and at a temperature of 350~500℃. The diffusivity, permeability, and solubility were obtained by use of the time-lag method and by measurement of stedy-state examining permeation rate. Oxide film on 304 stainless steel surface acting as a very good barrier reduced hydrogen premation rate.
분말 형태의 하프늄 시편에서 하프늄 수소화합물 형성시, 전체반응을 지배하는 율속단계(rate controlling step)를 200~770 torr의 압력조건과 반응률의 함수관계로 부터 조사하였다. 일정한 반응비(reacted fraction)를 가지는 조건하에서, 압력에 따른 반응률의 변화는 반응초기에는 압력의 자승에 비례하는 경향을 나타내다가, 반응이 후기로 진행될수록 압력에 정비례하는 경향을 보여주었다. 이와 같은 경향은, 전체반응을 지배하는 율속단계가 반응초기에는 하프늄 시편표면까지 도달하는 수소 분자들의 mass transfer이고, 반응후기에는 시편표면에서의 화학적흡착(chemisorption)인 것을 알수있다.
α-상을 가지는 하프늄 수소고용체의 수소방출 기구를 조사하기 위하여 가스 크로마토그래프(gas chromatograph)를 이용한 열분석 방법이 사용되었다. 판상형태의 시편의 두께가 일정할때, 수소 확산계수는 시간과 $Ln(1-Q_t/Q_\infty)$의 함수관계로부터 얻을 수 있었고, 수소의 격자내 확산에 필요한 활성화 에너지는 온도와 수소 확산계수의 함수관계를 이용하여 구하였다. 그리고, 트랩(trap)활성화 에너지는 정상온도(peak temperature)의 가열속도(heating rate)에 대한 의존성으로 부터 구하였다. 이 조사에서는 일정한 가열속도에서 2개의 수소 방출 피이크가 나타났으며, 하프늄 수소고용체의 2개의 방출 피이크는 입계를 통한 수소확산에 의존하는 방출 피이크(peak)가 먼저 나타나고, 격자내에서 수소확산에 의존하는 피이크는 나중에 나타나는 것으로 추론된다.
