Dielectric properties of iron doped calcium copper titanate,CaCu<Subscript>3</Subscript>Ti<Subscript>3.9</Subscript>Fe<Subscript>0.1</Subscript>O<Subscript>12</Subscript> ceramic

Dielectric properties of iron doped CaCu₃Ti₄O₁₂ (CCTO), viz. CaCu₃Ti_3.9Fe_0.1O₁₂ (CCTFO) prepared by a novel semi-wet route have been investigated. X-ray diffraction of powder sintered at 900 °C show formation of single phase solid solution. Energy dispersive X-ray spectroscopy (EDX) confirmed the presence of CuO rich phase at grain boundaries of CCTFO. Nature of dielectric relaxation observed above room temperature is studied using complex plane impedance analysis and modulus spectroscopy. It has been found that out of the two relaxations reported earlier above room temperature, one occurring at lower temperature is due to grainboundaries interfacial polarization.     

Innovative methodologies of circuit edit by focused ion beam (FIB) on wafer-level chip-scale-package (WLCSP) devices

As packaging technology advances to wafer level chip scale packaging (WLCSP) to enable reduced chip size and manufacturing cost, circuit edit has become a critical issue for the fully packaged integrated circuits (ICs). These advanced package types cannot be rebuilt on a single chip; therefore, function testing after circuit edit of WLCSP faces challenges. Furthermore, there are routings at the redistribution layer of WLCSP ICs. Circuit edit was applied on both the chip and the package level. In this paper the focused ion beam was applied to mill the organic material of the package structure to expose underlying ICs, instead of chemically destroying the packaging. Metal line cutting and conductive path deposition were also developed by a beam-based technique. These new approaches make the direct edit of electrical circuitry possible not only in ICs but also at package level. Therefore, for the debug process and for failure analysis, the WLCSP ICs have negligible damage and negligible signal integrity loss by retaining the original packaging structure.     

LA ICP-MS in microelectronics failure analysis

To keep up with the trend of integrating more functionality within lighter and smaller consumer electronics devices, the dimensions of components keep shrinking. Technologies such as high density interconnection, 3-D interconnection, system in package (SIP), and flexible circuit are becoming more commonly used. The smaller dimensions of the conductors and insulators (spacing) used in these technologies make them more sensitive to chemical contamination. Trace amounts of chemical contamination introduced during the manufacturing process or in the field can cause device failures. The failure mechanisms include inversion-induced leakage current, corrosion, and electro-chemical migration, to name a few. The complexity of materials used in a highly integrated system also poses new challenges for fault isolation and chemical characterization in failure analysis. This paper calls attention to the selection of appropriate analytical techniques in terms of spatial resolution and sensitivity, sample preparation complexity, throughput, and detection limitations. We present two failure analysis cases in which LA-ICP MS, in conjunction with other analytical techniques, was successfully used to identify the source of chemical contamination and the root cause.     

Degenerate problems of optimal control. II

The paper is the second part of the review of the results obtained by the special theory of the degenerate problems of optimal control and its applications, including the newest ones. Consideration was given to the methods based on the rearrangement of the degenerate problems in the smaller-order regular derivative problems, the main types of solutions of the derivative problems, and the issues of their realization as the generalized solutions of the original problems. The generalized conditions for their optimality were derived. Examples, both methodological and applied, were presented to demonstrate the efficiency of these methods.     

Multiscale simulation of the dislocation emissions of single Ni crystal in nanoindentation

The simulation of nanoindentation into single nickel crystal is performed by using quasi continuum method. The strain energy-displacement and load-displacement curves are presented to study the mechanical behavior of the dislocation nucleation. The characteristics of the stacking fault and dislocation nucleation are determined by calculating the centro-symmetry parameters and analyzing the displacement field of the atoms beneath the indenter. The structure of the stacking fault and the characteristics of dislocation obtained in the simulation by quasicontinuum method are reproduced in the simulation by molecular dynamics.     

Electromagnetic and neutron emissions from brittle rocks failure: Experimental evidence and geological implications

It has been observed energy emission in the form of electromagnetic radiation, clearly indicating charge redistribution, and neutron bursts, necessarily involving nuclear reactions, during the failure process of quasi-brittle materials such as rocks, when subjected to compression tests. The material used is Luserna stone, which presents a very brittle behaviour during compression failure. The observed phenomenon of high-energy particle emission, i.e., electrons and neutrons, can be explained in the framework of the superradiance applied to the solid state, where individual atoms lose their identity and become part of different plasmas, electronic and nuclear. Since the analysed material contains iron, it can be conjectured that piezonuclear reactions involving fission of iron into aluminum, or into magnesium and silicon, should have occurred during compression damage and failure. These complex phenomenologies are confirmed by Energy Dispersive X-ray Spectroscopy (EDS) tests conducted on Luserna stone specimens, and found additional evidences at the Earth’s Crust scale, where electromagnetic and neutron emissions are observed just in correspondence with major earthquakes. In this context, the effects of piezonuclear reactions can be also considered from a geophysical and geological point of view.     

Elastic field and effective moduli of periodic composites with arbitrary inhomogeneity distribution

This paper develops a semi-analytic model for periodically structured composites, of which each period contains an arbitrary distribution of particles/fibers or inhomogeneities in a three-dimensional space. The inhomogeneities can be of arbitrary shape and have multiple phases. The model is developed using the Equivalent Inclusion Method in conjunction with a fast Fourier Transform algorithm and the Conjugate Gradient Method. The interactions among inhomogeneities within one computational period are fully taken into account. An accurate knowledge of the stress field of the composite is obtained by setting the computational period to contain one or more structural periods of the composite. The effective moduli of the composite are calculated from average stresses and elastic strains. The model is used to analyze the stress field and effective moduli of anisotropic composites that have cubic symmetry. It shows that the bulk and shear moduli predicted by the present model are well located within the Hashin-Shtrikman bounds. The study also shows that the stress field of the composite can be significantly affected by the distribution of inhomogeneities even though the effective moduli are not affected much.     

Position and size effects on voids growth in nonlinear elasticity

Numerical studies of multiple voids growth are carried out on a nonlinear hyper-elastic 2D cylinder subjected to an expansionary boundary condition. For certain compressible hyper-elastic material, our numerical experiments on the case of two voids revealed that both the positions and initial sizes of the pre-existing voids can have significant effects on the final grown configuration. We found that, for the initial voids of macroscopic scale both factors affect the final result in a continuous manner and two grown voids of comparable size are commonly observed, and for the initial voids of mesoscopic scale the size effect is no longer continuous and one of the grown voids is always found significantly greater than the other, while for the initial voids of microscopic scale the position effect is essentially decisive on the voids growth and the center positioned void always grows much more rapidly. We also found that the size and position effects are stronger if the material is less compressible, or the load, with the smaller principle stress in alignment with the two voids, is less symmetric.     

Aluminum industry and climate change—Assessment and responses

It is now possible to assess the impact of the production processes of aluminum on the environment and to describe some of the ongoing responses and opportunities for improvement. This is compared with the benefits of aluminum in transportation, where the growing usage in various forms of transport due to its low density, high strength, and ability to be recycled enables reduced mass, increased fuel efficiency, reduced emissions and increased safety. It is the purpose of this paper to compare and contrast the emissions generated in the production of aluminum with the benefits accruing from its increased use in transportation.