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In this study, cordierite ceramic samples with very low thermal expansion are prepared by the pressureless sintering technique. The effects of sintering temperature and holding time on their sintering density and elastic modulus are investigated, while their optimal values are assessed as 1420°C and 1 h, respectively. These parameters ensure the elastic modulus of 121GPa, the relative sintering density corresponding to 95% of the theoretical value, and the coefficient of thermal expansion of |4.4|ϗ 10−7 °C.

Strain (intrinsic and thermo) and dead layer are inevitable at the substrate–ferroelectric film interface. They significantly affects the properties of nanoscale devices. The effect of strain and dead layer on the nonlinear electric-mechanical behavior of ferroelectric thin films is investigated based on micromechanical domain-switching model. Strain enhances the Gibbs free energy of a domain, making the domains more unstable and domain switching more continuous. Due to the existence of the dead layer between the ferroelectric thin film and substrate, the dielectric constant values and the effective electric field decrease through the film, thus leading to the decrease of the remnant polarization and increase of the coercive field. Our model, in which strain and dead layer are taken into consideration, shows improved displacement and strain versus electric field loops that agree reasonably well with the experimental data. In addition, both the electric displacement hysteresis and strain butterfly loops under various stress load have also been investigated by our model.

The reliability performance of InxGa1-xAs n-type metal-oxide-semiconductor field-effect transistors with Al2O3 gate dielectric under positive-bias temperature instability stress is investigated systematically. A model of stress-induced border traps was proposed to interpret all charge pumping and I-V experimental results excellently. The stress-induced border traps include recoverable donor traps and permanent acceptor traps with respective energy densities ΔDSOXDonor(E) and ΔDSOXAcceptor(E) . The shapes of ΔDSOXDonor(E) and ΔDSOXAcceptor(E) have been extracted from experimental data. ΔDSOXAcceptor(E) mainly distributes in the conduction band of InGaAs with a tail extending to the mid-gap, whereas ΔDSOXDonor(E) has a large distribution inside the energy gap and extends to the conduction band. The high density of ΔDSOXDonor(E) in the energy gap induces large degradation in the off-current, which is particularly serious when the In composition x is raised to 0.65.

There is an increasing interest in the preparation of magnetic composite coatings for application in microelectromechanical systems (MEMS) actuators. In this paper, the CoNiMnP–BaFe12O19 nanocomposite coatings have been electrodeposited from an aqueous bath containing BaFe12O19 nanoparticles. The influence of BaFe12O19 nanoparticles concentration in the bath on the incorporated nanoparticles fraction, element content fraction, surface morphology, preferred orientation, coercivity, retentivity, and the maximum energy density of the nanocomposite coatings has been investigated. The results indicate that the incorporation of BaFe12O19 nanoparticles favours the electrodeposition of Co and Mn while depressing the deposition of Ni and P. The maximum embedded BaFe12O19 nanoparticles fraction of ∼21·8 wt-% is achieved. The incorporation of BaFe12O19 nanoparticles may refine the grain size and change the preferred orientation within the nanocomposite coatings structure. CoNiMnP–BaFe12O19 nanocomposite coatings wit...

Three Mg–Al–Zn alloys (AZ31, AZ61 and AZ91) were subjected to plane-strain compression at different temperatures (200 and 400 °C) and strain rates (10−2 and 10−4 s−1). The effect of second-phase precipitates on the texture evolution was investigated. It was found that a high level of Mg17Al12 precipitates impeded extension twinning and enhanced dynamic recrystallization, resulting in weak deformation textures.

One of the major problems of p-i-n tunneling field-effect transistor (TFET) is the reliability due to the strong electric field near the tunneling junction. In this paper, using technology computer-aided design simulation, we show that the insertion of a thin n-layer into the tunneling junction of the p-i-n TFET (p-n-i-n TFET) not only enhances its drive current, as has been previously reported, but also improves its reliability. As compared with the conventional p-i-n TFET, we demonstrate the following properties of the p-n-i-n TFET: 1) The normal component of the electric field near the tunneling junction is reduced, and therefore, the field-driven interface-trap generation can be reduced. This can be further reduced by properly aligning the gate electrode with respect to the tunneling junction. 2) The threshold-voltage shift due to the dielectric charge generated near the tunneling junction is significantly reduced. 3) The variation of the threshold voltage to the oxide and bulk thickness variations is also reduced.

In this paper, the two kinds of precursor powders of BiPb2212 and CaCuO2 were prepared by double powder method and an improved coprecipitation method, and then the BiPb2212 powders were fabricated by mechanical grinding and hand grinding. The BiPb2212 powders and CaCuO2 powders were prepared by two kinds of grinding methods mixed with a certain proportion of grinding, the Bi2223 superconducting tape with 37 filaments were prepared by removing the carbon, filling tube and annealing. The XRD analysis, SEM observation, laser particle size analysis and the tap density test of the precursor BiPb2212 powders were carried out respectively by mechanical grinding and hand-grinding. The results showed that the phase composition, microstructure, particle size distribution and tube density detection were all significant differences by using two kinds of grinding methods. Finally, the superconductivity test of the treated strip results show that the critical current from the field for the Bi2223 multi-core strip at 77K is improved from 86A (hand-grinding method) to 127A( mechanical grinding method). Therefore, the Bi2223 precursor powder by using mechanical grinding method is more conducive to obtain high-performance.

Variable temperature neutron diffraction was carried out on mesoporous α-Fe2O3 (hematite) with a mean pore diameter of 38.5 A. Data were directly compared to measurements carried out on bulk hematite. Unlike bulk hematite, the mesoporous material does not undergo a spin−flop transition from a weak ferromagnet to a pure antiferromagnet (Morin transition, TM = 259.1(2)). Instead, the material remains a weak ferromagnet down to 2 K with the magnetic moments staying perpendicular to the R3c [111] ([003] in the hexagonal cell) direction rather than realigning (to) almost parallel to this direction. The angle of the magnetic Fe3+ moments to the [111] direction in the antiferromagnetic state also accurately was obtained for bulk hematite. Using magnetic hysteresis measurements, the canting angle responsible for weak ferromagnetism within the ab planes (hexagonal setting) was deduced for the mesoporous material at 12 K and compared to the angle made in bulk hematite above TM.

In this paper, turning experiments on the machining of composites SiCp/Al with a polycrystal diamond (PCD) tool have been carried out. The cutting force characteristics in ultrasonic vibration turning compared with those in common turning were studied. Through single factor experiments and multiple factor orthogonal experiments, the influences of three cutting parameters, namely cutting velocity, amount of feed and cutting depth, on the cutting force were analyzed in detail. At the same time, according to the experimental data, an empirical equation for the main cutting force in ultrasonic vibration turning was deduced. The research results indicate that: (1) ultrasonic vibration turning possesses a much lower main cutting force than that in common turning when adopting smaller cutting parameters, but if using larger cutting parameters, the difference will become inconspicuous; (2) there are remarkable differences of cutting force–cutting velocity characteristics in ultrasonic vibration turning and those in common turning, mainly because a built-up edge does not emerge in ultrasonic turning, unlike common turning in the corresponding velocity range; (3) in ultrasonic vibration cutting, the influence of the cutting velocity on the cutting force is most obvious among three cutting parameters explored the influence of the feed being the smallest, thus adopting lower cutting velocity and larger cutting depth not only can reduce the cutting force effectively but also can ensure cutting efficiency; (4) the conclusions are useful in the precision and super-precision manufacturing of thin-wall pieces.

In many fields of high-tech industry ultra-thin wall parts are employed. In this paper are reported experiments carried out to explore the surface microstructure of a camera’s guided draw-tube when applying an ultrasonic vibration cutting device to the traditional lathe. The influence rule of the cutting conditions on the surface roughness was put forward, which was drawn by comparing ultrasonic cutting with common cutting by use of a cemented carbide tool and a polycrystalline diamond (PCD) tool. The test results showed that the ultrasonic cutting performs better than the common cutting for the same conditions. According to the analysis of the test results, the surface characterization is influenced clearly by the rigidity of the acoustic system and the machine tool. Also it is dependent on the proper setting height of the tool tip, otherwise, dense regular low-frequency vibration ripples will be scraped on the ultrasonic machined surface, i.e., when the tool tip is set higher than the rotating center of the workpiece by three times the amplitude of ultrasonic vibration, the vibration ripples behave alight; on the other hand, they turn light and shade alternately when the tool tip is lower than the rotating center of the workpiece by three times the amplitude of ultrasonic vibration.

Copper indium gallium diselenide (CIGS) becomes more significant for solar cell applications as an alternative to silicon. The quality of the layer has a critical impact on the final efficiency of the solar cell. An influence of the post-deposition millisecond range flash lamp annealing on the optical and microstructural properties of the GIGS films was investigated. Based on the Raman and photoluminescence spectroscopy, it is shown that flash lamp annealing reduces the defect concentration and leads to an increase of the photoluminescence intensity by a factor of six compared to the nonannealed sample. Moreover, after flash lamp annealing the degradation of the photoluminescence is significantly suppressed and the absolute absorption in the wavelength range of 200-1200 nm increases by 25%.

In this letter, we report for the first time the degradation mechanism of drain current in tunneling field-effect transistors (TFETs). Using positive-bias and hot-carrier (HC) stress experiments and TCAD simulation, we show that the drain current degradation is mainly induced by the interface traps and/or oxide charge located above the tunneling region, causing reduction of tunneling field and tunneling current. The interface traps mainly induce the degradation in transconductance, while the oxide charge essentially causes a threshold-voltage shift in TFETs. The results show that the interface-trap generation is dominant under a positive-bias stress, while the oxide-charge creation is important under an HC stress in n-TFETs.

We report, for the first time, the reliability issues of tunneling field-effect transistors (TFETs) by experiments. We observed that the overall reliability performance of n-TFETs is very different from those of the conventional n-MOSFET. The degradation of n-TFETs under positive bias temperature instability (PBTI) stress is very large compared with the negligible degradation for the conventional n-MOSFET. The degradation of n-TFETs under hot-carrier stress is also larger than that in the conventional n-MOSFET and has a different temperature dependence. The shifts of the I d- V g curves under PBTI stress are not parallel in the strong inversion region as in the case of the conventional n-MOSFET. The different degradation behaviors are explained by different degradation mechanisms due to some inherent properties of TFETs.

The reliability performance of InxGa1-xAs n-MOSFETs with Al2O3 gate dielectric under positive-bias temperature instability stress is investigated. The following new phenomena are demonstrated: 1) There are high densities of fast interface traps N-it and slow oxide border traps N-SOX near the interface between InGaAs and Al2O3. The border traps are more fragile under stress, and therefore, the stress mainly induces border traps. 2) The stress-induced border traps consist of permanent acceptor traps and recoverable donor traps. Acceptor trap energy density Delta D-SOX(Acceptor) (E) is mainly distributed above the conduction band edge E-c of InGaAs with a tail extending to the midgap, whereas donor trap energy density Delta D-SOX(Donor) (E) has a large distribution inside the InGaAs energy gap with a tail extending to the conduction band. 3) Flicker noise variation after stress and its correlation to the acceptor and donor trap generation and recovery are demonstrated. 4) The recoverable donor traps induce the subthreshold slope and off-current degradation in the stress phase and recover in the recovery phase and also induce continuous degradation of on-current in the recovery phase. The permanent acceptor traps induce the transconductance and on-current degradation. The long-term device lifetime is mainly determined by the generation rate of the acceptor traps. 5) Comprehensive comparison between the Si and InGaAs MOSFETs' degradation behaviors under bias temperature instability stress is presented. The physical recovery of donor oxide traps in dielectric in InGaAs/Al2O3 has never been observed in a Si MOS structure, deserving special attention and further investigation.

Fully reversed low cycle fatigue tests were conducted on 〈001〉 oriented single crystals of the nickel base superalloy SC16 at a constant total strain range of 2.0%. The strain rates were varied from 10−2 to 10−5 s−1 at 750°C and the temperatures were changed from 650 to 950°C under the strain rate 10−3 s−1. During cycling under the high strain rates 10−2 and 10−3 s−1 at 750°C or under the strain rate 10−3 s−1 at 650°C, the SC16 single crystals show that the tensile stress (T) is higher than the compressive stress (C). During cycling under the low strain rates 10−4 and 10−5 s−1 at 750°C or under the strain rate 10−3 s−1 at 850°C, the cyclic tension—compression asymmetry of C > T was observed. At 950°C under the strain rate 10−3 s−1, no tension—compression asymmetry (T = C) was present during fatigue testing. The deformation mechanism corresponding to T > C determined by transmission electron microscopy (TEM) is that the γ' precipitates are sheared by pairs of a/2〈110〉 matrix dislocations coupled by antiphase boundaries (APB) within γ' phase. The reversed asymmetry behaviour (C > T) was found to be associated with the (111)〈112〉 viscous slip producing superlattice intrinsic/extrinsic stacking faults (SISF/SESF) in γ' precipitates. At 950°C (T = C) dislocation climbing over the γ' precipitates becomes the dominant deformation mechanism. Models which can explain the tension—compression asymmetry behaviour were discussed.

Low-cycle fatigue experiments under combined axial-torsional loading have been carried out on alloy 800 H tubular specimens at room temperature. In comparison with proportional loading, an extra cyclic hardening effect produced by nonproportional loading was observed. The microstructure study highlights the fact that the dislocation arrangement under proportional loading is significantly different from that under nonproportional loading. Mechanical twinning was found in specimens cycled under axial loading and nonproportional loading. It is suggested that mechanical twinning depends not only on shear stress but also on normal stress on the plane of maximum shearing. The extra hardening can be interpreted in terms of the deformation microstructure. Fatigue cracking was initiated generally at the specimen surfaces along the plane of maximum shearing, but under nonproportional loading cracks were found also in the bulk of the specimens. Transcrystalline crack propagation was observed in the specimens after proportional and nonproportional LCF tests.

Reliability of InGaAs inversion channel n-MOSFET is investigated by systematic PBTI (positive bias temperature instability) stresses. The very complicated degradation phenomena are totally different from Si based MOSFETs. The degradation is mainly contributed by the generation of border traps under stress with recoverable donor trap of energy density ΔD SOX DONOR in the InGaAs energy gap with a tail extending to the conduction band energy, and with permanent acceptor trap of energy density ΔD SOX ACCEPTOR in the conduction band energy with a tail extending to the energy gap. The border trap model can explain all the experimental details of the PBTI degradation phenomena.

CP measurements show that PBTI stress induced interface trap area density ΔN it in InGaAs/Al 2 O 3 n-MOSFET is very small and has power law time evolution At0.22 in the stress phase, and is partially recovered in the recovery phase. However the DC I s -V g measurements show large degradations of negative ΔV g and sub-threshold swing S in the sub-threshold region and are recovered in the recovery phase, also show degradation of positive ΔV g in the on-current region and continuing degradation in the recovery phase until reaching a stable state. The I s -V g degradation is mainly contributed by generation of near interface slow oxide traps under stress with recoverable donor trap energy density ΔD SOX DONOR in the InGaAs energy gap with a tail extended to the conduction band energy, and permanent acceptor trap energy density ΔD SOX ACCEPTOR in the conduction band energy with a tail extended to the energy gap. This trap model explains all experimental details perfectly.

This paper summarizes our recent investigations of nano-wire n type tunneling field effect transistor (n-TFET) reliability by experimental measurements and physical analysis [1–3]. Large PBTI and HC degradations which are very different from those in conventional n-MOSFETs were observed. The results are interpreted by different degradation mechanism in TFET.

Tunneling n-FET reliability performance is studied for the first time by physical analysis and experimental measurements. (1) A new degradation mechanism by interface trap induced change of tunneling field and current I d is demonstrated. (2) Under PBTI or HC stress, there is a strong peak of vertical electric field E x at the gate/source overlapping region due to the P+ doping of the source, inducing high interface trap degradation. These explain the large PBTI and HC degradation, very different from those observed in conventional n-MOSFETs.

Deformation behaviour of IN738LC in two γ′ morphologies under monotonic loading at elevated temperatures has been studied. Mechanisms of dislocation-γ′ precipitate interaction have been identified. Dislocation reactions leading to stacking fault formation within γ′ have been characterized.

Creep behaviour of a nickel base alloy IN738LC during dwell period within creep-fatigue loading at 1223 K has been studied and compared to that of static creep. In the first few cycles a softening with regard to increase in creep rate with increasing number of cycles was observed. The possible mechanisms for this acceleration of creep are discussed.

Deformation behaviour of IN738LC in two γ′ morphologies under monotonic loading at elevated temperatures has been studied. The specimens containing 80 nm γ′ precipitates (corresponding to small particle in commercial alloy with bimodal distribution of ′ phase) shows a higher strength and lower ductility than those with 450 nm γ′ precipitates (corresponding to large particle in commercial alloy). Work hardening can be found only in the specimens containing 450 nm γ′ precipitates. TEM investigation shows, over a wide range of test conditions used, stacking fault contrast in γ′ precipitates indicating a cutting mechanism operative. Based on this observation and a model of dislocation-γ′ precipitate interaction the mechanical behaviour can be qualitatively explained.

The low cycle fatigue (LCF) behaviour of a nickel base superalloy IN 738LC was studied as a function of test conditions. The alloy was heat treated to produce γ′ cuboids of 450 nm in edge length. Fully reversed total axial strain controlled LCF tests were conducted at different total strain ranges in laboratory atmosphere at a temperature of 1223 K. Two strain rates were employed. The microstructure of the deformed specimens was examined with the help of Transmission Electron Microscopy (TEM) and the fractured surface was studied by Scanning Electron Microscopy (SEM).

Fully reversed strain control low cycle fatigue (LCF) tests were conducted on the nickel-base superalloy IN738LC at 10-35-1 and 10-5s-1 strain rates at 950°C. Two unimodal γ′ distributions in the material with an average size of 80 nm and 450 nm, respectively, were used in this work. An initial cyclic hardening and a work hardening was observed in the material containing large γ′ particles, while a continuous softening was present in the material containing small particles. Strain rate and strain range were found to play a significant role in cyclic deformation. At the high strain range and high strain rate, observation of stacking faults in γ′ precipitates indicates shearing of the γ′ precipitates by dislocations. At the low strain range and low strain rate, a homogeneous dislocation distribution in γ matrix suggests dislocation climbimg over the precipitates. The implications for mechanical properties and dislocation struscture are discussed.

Fully reversed (R=-l), total axial strain controlled LCF tests were performed on button head type specimens at 850°C. Tests were conducted at a constant strain rate of 102-3 s-1 using different total strain amplitudes from 0.4% to 1.0%. The Transmission Electron Microscopic (TEM) observations of the deformed specimens show that the γ’ precipitates are sheared by dislocations producing superlattice stacking faults in the precipitates at the lower strain amplitudes and at the higher strain amplitudes they are overcome by Orowan process. The results of the cyclic plasticity are discussed in the light of microscopic mechanisms.

A low resistance nonalloyed ohmic contact to n‐GaAs is formed which utilizes the solid‐phase epitaxy of Ge through PdGe. Discussion focuses on the conditions necessary to attain low specific contact resistivity (∼10−6 Ω cm2 on 1018 cm−3 n‐GaAs) and on the interfacial morphology between the contact metallization and the GaAs substrate. MeV Rutherford backscattering spectrometry and channeling show the predominant reaction to be that of Pd with amorphous Ge to form PdGe followed by the solid‐phase transport and epitaxial growth of Ge on 〈100〉 GaAs. Cross‐sectional transmission electron microscopy and lattice imaging show a very limited initial Pd‐GaAs reaction and a final interface which is planar and structurally abrupt to within atomic dimensions. The presence of excess Ge over that necessary for PdGe formation and the placement of Pd initially in contact with GaAs are required to result in the lowest contact resistivity. The experimental data suggest a replacement mechanism in which an n+‐GaAs surface region is formed when Ge occupies excess Ga vacancies.