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There is a major interest in replacing cobalt binder in hardmetals (cemented carbides) aiming for materials with similar or even improved properties at a lower price. Nickel is one of the materials most commonly used as a binder alternative to cobalt in these metal-ceramic composites. However, knowledge on mechanical properties and particularly on fatigue behavior of Ni-base cemented carbides is relatively scarce. In this study, the fatigue mechanics and mechanisms of a fine grained WC-Ni grade is assessed. In doing so, fatigue crack growth (FCG) behavior and fatigue limit are determined, and the attained results are compared to corresponding fracture toughness and flexural strength. An analysis of the results within a fatigue mechanics framework permits to validate FCG threshold as the effective fracture toughness under cyclic loading. Experimentally determined data are then used to analyze the fatigue susceptibility of the studied material. It is found that the fatigue sensitivity of the WC-Ni hardmetal investigated is close to that previously reported for Co-base cemented carbides with alike binder mean free path. Additionally, fracture modes under stable and unstable crack growth conditions are inspected. It is evidenced that stable crack growth under cyclic loading within the nickel binder exhibit faceted, crystallographic features. This microscopic failure mode is rationalized on the basis of the comparable sizes of the cyclic plastic zone ahead of the crack tip and the characteristic microstructure length scale where fatigue degradation phenomena take place in hardmetals, i.e. the binder mean free path. (C) 2014 Elsevier Ltd. All rights reserved.

3D integration technology opens the way of heterogeneous silicon platform, as for example, millimeter-wave functionalities could be integrated in future communication modules. Consequently, copper pillar technology realized at 1st level of interconnection between silicon top dies and silicon interposer must be evaluated in this new frequency range. In this paper, a test vehicle has been designed to assess radio frequency behavior of 3D stacking as insertion losses (IL) up to 40GHz induce by copper pillar interconnection and assembly parameters (pitch, underfilling,...). Copper pillar ground-signal-ground (GSG) vertical transition exhibits IL lower than 0.2dB at 40GHz on high resistive silicon substrate and seems to be the minor contributor of all 3D interconnections as TSV, and RDL. Capillary underfill and GSG transition pitch have been evaluated to have a weak impact. Cu ring designed to limit bleed-out and fillet assures PAD integrity and induces a strong signal reflection above 15GHz. Finally, process assembly robustness of high aspect ratio top die (10x3mm^2) has been assessed with DC measurements.

A reflectarray element with electronic phase control implemented by ohmic MEMS switches is characterized and validated in the X-band. The proposed element is based on two patches aperture-coupled to a microstrip network with a common delay line, forming a sub-array, in order to reduce both cost and manufacturing complexity in large reflectarrays. The electrical length of the line can be modified through the inclusion of a series switch between different segments of the microstrip line. The ohmic electrostatic switch has been designed for RF applications and manufactured on a coplanar line. The transition between the coplanar line of the MEMS and the microstrip delay line has been implemented using gold wires which have been bonded to the printed pads. This connection leads to a high impedance line. The MEMS switches have been characterized using reflection and transmission measurements on microstrip lines for deducing an equivalent circuit, which has been used in the validation of the gathered element with electronic phase control measured using waveguide simulator. The same approach has been applied to evaluate a 2-bit reflectarray element.

In most of the applications where hardmetals are implemented, mechanical contact plays an important role from a design viewpoint, either as direct key parameter (e.g. wear resistance) or as indirect relevant factor (e.g. residual strength associated with contact-induced damage). In this work, the contact response of three cemented carbides WC–Co with different microstructural features is evaluated. The study is performed using spherical indenters (Hertzian contact) and it is focused on: 1) determining the critical loading parameters affiliated to the emergence and evolution of damage; and 2) investigating the relevance of microstructure on the levels of residual strength attained. It is found that strength retention is improved as contact damage mode goes from brittle to quasi-plastic, a transition directly dependent on microstructure. Hence, microstructural design searching for higher damage tolerance (i.e. deformation prevailing over fracture as damage mode) is concluded to be an optimal approach for the development of hardmetals with improved reliability. In practical terms, this is achieved by enhancing toughness through either higher binder content and/or microstructural coarsening, as far as the field application requirements are satisfied.

24years-old nullipara was referred at 23 weeks of gestation because absent cavum septum pellucidum was noticed at a routine ultrasound scan. Ultrasonography showed complete absence of septum pellucidum resulting in box like frontal horns and a mild form of holoprocencephaly. No other abnormalties were detected. An MRI image at 25 weeks has confirmed absent septum pellucidum without fusion of frontal lobes ruling out the diagnosis of lobar holoprocencephaly. Bilateral atrophy of optic nerve with hypoplasia of optic chiasm was seen on coronal 3D image. A normal male karyotyping was found. The fetus was followed up on 4-weekly basis. At 41 weeks gestation, following the onset of spontaneous contractions, an emergency caesarean section was performed for fetal distress. A 3650-g male baby was delivered with Apgar scores of 9, 10 and 10 at 1, 5 and 10 min, respectively. No resuscitation or respiratory support was required. Neonatal dilation fundoscopy examination at 3 months of age has revealed slightly small right optic nerve head and normal left one. Neonatal MRI at 4 months of age has confirmed complete absence of the septum pellucidum, low lying fornices, hypoplasia of cerebral white matter and mild ventriculomegaly. The posterior fossa, anterior visual pathway and optic nerves were normal. A hydrocortisone day curve at 4 months of age revealed low endogenous cortison level, which was replaced. the neonate has normal milestone. He was followed up until age of 14 months when he required a growth hormone replacement and his vision was normal. In conclusion, prenatal diagnosis of septo-optic dysplasia should involve MRI examination in order to outline the diagnosis followed by neonatal MRI and ophthalmological examination to help define the extent of optic-nerve lesion and therefore the prognosis. Neonatal multidisciplinary care is crucial for satisfactory outcome