In this paper, the effect of annealing temperature (T) on the ductility of 50 nm thick nanocrystalline (NC) Cu films adhered to flexible substrates was investigated by a uniaxial tension test. It was ...found that the ductility and the fracture toughness (Gc) can be significantly improved through an annealing treatment. The crack onset strain of the 300 °C annealed Cu film is 18.1%, which is about twice that of the as-deposited NC Cu film. In addition, Gc of the 300 °C annealed Cu film is 1833 J m−2, which is nearly three times that of the as-deposited NC Cu film. Focused ion beam results indicate that the as-deposited film fractures with delamination and strain localization coevolving, while the as-annealed film fractures by adhering well to the substrate. At a higher T, the tensile residual stress is lower, the microstructure is more stable, and a diffusion or compound interface is generated, resulting in a better bonding between the film and the substrate. In this case, the strain localization is suppressed more effectively, causing improved ductility and Gc. Whether the film is as-deposited or as-annealed, the saturated crack spacing is about 1.41 µm, which accords well with the theoretical analysis. Intergranular fracture is suggested to be the main fracture mechanism.
Nanoindentation creep tests were carried out at maximum indentation loads from 500 to 9000
μN to study the indentation size effects (ISEs) on the creep behavior of nanocrystalline tetragonal Ta ...films. The experimental results show that the hardness, creep strain rate and stress exponent are all indentation size-dependent. The ISE on the creep behavior is explained by grain boundary diffusion and sliding, and self-diffusion along the indenter/specimen interface and along the free surface of specimen.
Phase transformation and mechanical properties of two distinct Ni-rich Ni–Ti–Al thin films deposited at various temperatures were investigated in this paper. It is found that phase transformation ...temperatures and hardness of the films obviously increase with growth of Ni-rich precipitates, and their phase transformation hysteresis decreases. Especially, martensitic transformation start temperature of the Ni49.7Ti45.3Al5 films exceeds room temperature and increases by 20°C, and the Ni44Ti32Al24 Heusler alloy films show near-zero transformation hysteresis. Besides, hardness of the two films increases by 12.8% and 22%, respectively. The evolutions are caused by the growth of Ni-rich precipitates which strengthens the matrix. The precipitation would sharply consume Ni content of the matrix that changes phase transformation behavior from the Ni-rich to Ti-rich films.
This paper proposes a method to enhance the dielectric properties of polypropylene (PP) films for capacitors by ultraviolet (UV) irradiation modification. The effect of different photoinitiator ...contents on the crosslinking reaction is analyzed, and the intrinsic correlation between the crosslinking structure and the insulation properties is investigated. The results show that a moderate amount of benzophenone (BP) addition (1.0 wt%) can improve the degree of dielectric crosslinking, with a gel content of 22.3 % for PP10. However, excessive amounts of BP lead to the degradation of molecular chains, increasing small molecular groups within the matrix and causing damage to the polymer insulation. Experiments on direct current (DC) conductivity and breakdown at different temperatures show that the chemically crosslinked network enhances the extent of molecular chain entanglement in the amorphous region, improving the film's thermal stability at high temperatures. At 115 °C, the breakdown strength of PP10 was 590.5 kV/mm, an increase of 20.5 % compared to pure PP. This study provides a viable idea for the reliable application of PP films under electrothermal coupling fields.
Recently, as a new type of energy storage material, conducting polymer has attracted much attention due to its excellent electrochemical properties. We summarize research on polymer based composite ...electrode materials and supercapacitors. The conducting mechanism, advantages and disadvantages in supercapacitor electrodes were reasoned through extensive based on the extensive analysis of the literatures., and new trends based on conducting polymers material and capacitor development are reviewed.
The dielectric properties of polypropylene (PP) for metalized film capacitors deteriorate severely at high temperatures. This article proposes a method to improve the dielectric strength of PP by ...introducing crosslinked structure. Compared with the original PP, the study shows that the crosslinking reaction creates chemical bonding linkages between the molecular chains and reduces the interchain distance, thereby inhibiting the mobility of the chain segments at high temperatures and weakening the free volume change at high temperatures. The traps introduced by the crosslinking points enhance the capture of carriers and reduce the electrical conductivity. At 115 °C, the breakdown strength of the modified films is enhanced by 20.2%, and the conductivity is reduced by 97.5%. In addition, the effect of irradiation time on the UV crosslinking reaction was investigated. The results show that the film properties can be improved at an irradiation time of 90 s. This method guides improving the PP high-temperature insulation from the molecular chain structure regulation perspective.
► The atom diffusion is accelerated by the electric field. ► The acceleration is enhanced with an increment of annealing temperature. ► It is resulted from the increase of the mobility of vacancies ...and atoms.
In the present paper, the effects of electric field annealing on interface diffusion of Cu/Ta/Si stacks were studied by means of XRD, XPS and TEM. The barrier property of Ta films was evaluated based on the diffusion of Cu atoms. It was found that the external electric field accelerates the diffusion of Cu atoms through Cu/Ta/Si interfaces during annealing. With the increment of annealing temperature, the effect of the electric field upon the atomic diffusion becomes more significant. The mechanism of accelerated interface diffusion is suggested and the failure of Ta barrier layer is discussed based on the mobility of vacancies and Cu atoms inside Cu/Ta/Si stacks caused by the electric field.
The effect of individual thickness on the mechanical properties of Cu/Ru multilayer films deposited onto flexible substrate was investigated by uniaxial tension tests. It is found that both strength ...and ductility of the Cu/Ru multilayer films are remarkably dependent on the individual thickness. An optimized combination of strength and ductility is obtained when the individual thickness is 20nm. The strengthening mechanism changes from the confined layer slip of single dislocations to the load-bearing effect and the individual thickness dependent ductility is due to the competition between the stress intensity factor in Ru layers and the plasticity deformation in Cu layers.
•The strength and ductility of Cu/Ru multilayers depend on individual thickness (h).•An optimized combination of strength and ductility is obtained when h is 20nm.•This finding may play an important role in the working stability of MEMS.
The strain rate sensitivity of rolled nanocrystalline (NC) Ni was studied by nanoindentation. The grain continuously grows from 20 nm to 92 nm after rolling deformation. The stress driven grain ...boundary migration accompanied by dislocation emission leads to the grain growth. The strain sensitivity first increase and then decrease with the increased rolling strain, which has a similar variation of dislocation density in rolled NC Ni. The remarkable shift of rate sensitivity is attributed to the dislocation supported grain boundary mediated process.
This study aimed to develop a new experimental model of liver cirrhosis in swine by using carbon tetrachloride (CCl(4)) and ethanol. Liver cirrhosis was induced by intraperitoneal injection of CCl(4) ...twice a week for 9 weeks. Maize flour was the only food provided and the animals drunk a 5% alcohol-water mixture. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin, bilirubin and portal venous pressure (PVP) levels were determined throughout CCl(4) treatment. The animals were sacrificed under general anesthesia at week 9 and liver samples were collected for histological analysis. 83.3% of the swine had liver cirrhosis and 33.3% had died. There was no change of body weight during the course of the experiment (p > 0.05). The AST and ALT levels increased significantly in the early stage of the study but had a trend to decrease during the late phase. The level of bilirubin increased greatly and albumin decreased during the whole experiment (p < 0.05). PVP levels decreased in the early stage in CCl(4)-treated swine, but increased significantly at the late phase. In conclusion, this study was successful in producing liver cirrhosis and offers an ideal experimental model for observing surgical therapeutic efficacy.
PDF
