Different oxidation treatments on CNTs using diluted 4.0 M H2SO4 solution at room temperature and or at 90℃ reflux conditions were investigated to elucidate the physical and chemical changes occurring on the treated CNTs, which might have significant effects on their performance as catalyst supports in PEM fuel cells. Raman spectroscopy, X-ray diffraction and transmission electron microscope analyses were made for the acid treated CNTs to determine the particle size and distribution of the CNT-supported Pt-Ru nanoparticles. These CNT-supported Pt-based nanoparticles were then employed as anode catalysts in PEMFC to investigate their catalytic activity and single-cell performance towards H2 oxidation. Based on PEMFC performance results, refluxed Pt-Ru/CNT catalysts prepared using CNTs treated at 90℃ for 0.5 h as anode have shown better catalytic activity and PEMFC polarization performance than those of the commercially available Pt-Ru/C catalyst from ETEK and other Pt-Ru/CNT catalysts developed using raw CNT, thus demonstrating the importance of acid treatment in improving and optimizing the surface properties of catalyst support.

Purpose - Many studies show that dissatisfied customers are silent rather than expressing complaints directly to firms. Although silent voices are pervasive in service failure, they have received little attention from researchers. Silence implies a multidimensional nature, not just the opposite of voice. This study focuses on two types of silent students in higher education: acquiescent silence and defensive silence. This study also proposes cognitive trust and affective trust as variables affecting student silence. The objective of this study is to analyse the effects of trust types on student silence and exit intention. Research design, data, and methodology - To test the proposed model, this study conducted a survey with undergraduate students who selected silence in a dissatisfied relationship with a professor. Respondents were asked to respond to the questionnaire, recalling the dissatisfaction at that time. A total of 300 students was surveyed from whom 275 completed questionnaires was obtained. The structural equation model analysis was used for the hypothesis test. Results - First, cognitive trust was negatively related to acquiescent and defensive silence. Second, affective trust was negatively related to acquiescent and defensive silence. Third, cognitive trust was negatively exit intention, but affective trust didn’t significantly reduce exit intention. Forth, acquiescent silence was positively related to exit intention, but defensive silence didn’t have a significant positive impact on exit intention. Thus, a key result of this analysis was that acquiescent silence enhances exit intention. Conclusions - The findings of the study provide a better understanding of the types of silence, and the role of trust, thus furthering the implication of student reactions to dissatisfaction. In particular, this study is meaningful in that it confirms the value of student silence in the context of complaint management. Acquiescent silence should be more importantly managed because it has stronger negative motive than defensive silence. Acquiescent silence is reduced through various channels(mail, telephone, counseling) that can express complaints. Cognitive trust and affective trust are a essential factors in reducing silence. Also, in explaining exit intention, cognitive trust plays a more important role than affective trust.