Alexander Aman

Microwave emission from lead zirconate titanate induced by impulsive mechanical load

This paper focuses on microwave emission from Lead zirconate titanate Pb [ZrxTi1−x] O3 (PZT) induced by mechanical stressing. The mechanical stress was initiated by impact of a sharp tungsten indenter on the upper surface of PZT ceramic. The sequences of microwave and current impulses, which flew from indenter to electric ground, were detected simultaneously. The voltage between the upper and lower surface of ceramic was measured to obtain the behavior of mechanical force acting on ceramic during the impact. It was found that the amplitude, form, and frequency of measured microwave impulses were different by compression and restitution phase of impact. Two different mechanisms of electron emission, responsible for microwave impulse generation, were proposed based on the dissimilar impulse behavior. The field emission from tungsten indenter is dominant during compression, whereas ferroemission dominates during restitution phase. Indeed, it was observed that the direction of the current flow, i.e., sign of ...

Microwave based method of monitoring crack formation

The formation of cracks in glass particles was monitored by application of linearly polarized microwaves. The breakage behavior of glass spheres coated with a thin gold layer of about 50?nm, i.e. a thickness that is lower than the microwave penetration depth, was tested. In this way the investigation of fracture behavior of electronic circuits was simulated. A shielding current was induced in the gold layer by the application of microwaves. During the crack formation the distribution of this current changed abruptly and a scattered microwave signal appeared at the frequency of the incident microwaves. The time behavior of the scattered signal reflects the microscopic processes occurring during the fracture of the specimen. The duration of the increasing signal corresponds to the crack formation time in the tested specimen. This time was estimated as particle size divided by crack development speed in glass. An intense emission of electrons occurs during the formation of cracks. Due to this, coherent Thomson scattering of microwaves by emitted electrons becomes significant with a delay of a few microseconds after the initial phase of crack formation. In this time the intensity of the microwave signal increases.

Micro- and nanostructure of a titanium surface electric-spark-doped with tantalum and modified by high-frequency currents

We have studied the characteristics of the porous microstructure of tantalum coatings obtained by means of electric spark spraying on the surface of commercial grade titanium. It is established that, at an electric spark current within 0.8–2.2 A, a mechanically strong tantalum coating microstructure is formed with an average protrusion size of 5.1–5.4 µm and pore sizes from 3.5 to 9.2 µm. On the nanoscale, a structurally heterogeneous state of coatings has been achieved by subsequent thermal modification at 800–830°C with the aid of high-frequency currents. A metal oxide nanostructure with grain sizes from 40 to 120 nm is formed by short-time (~30 s) thermal modification. The coating hardness reaches 9.5–10.5 GPa at an elastic modulus of 400–550 GPa.

Structure of metal-oxide Ti-Ta-(Ti,Ta)xOy coatings during spark alloying and induction-thermal oxidation

The study focuses on combined spark alloying of titanium and titanium alloy surface and porous matrix structure oxidation. The metal-oxide coatings morphology is the result of melt drop transfer, heat treatment, and oxidation. The study establishes the influence of technological regimes of alloying and oxidation on morphological heterogeneity of metal- oxide system Ti-Ta-(Ti,Ta)xOy.

Peculiarities of structure formation of layered metal-oxide system Ti-Ta-(Ti,Ta)xOy during electro-spark alloying and thermally stimulated modification

The study focuses on high-performance combined electro-spark alloying of titanium and titanium alloy (VT1-0, VT16) surface and porous matrix structure oxidation. The metal-oxide coatings morphology is the result of melt drop transfer, heat treatment, and oxidation. The study establishes the influence of technological regimes of alloying and oxidation on morphological heterogeneity of biocompatible layered metal-oxide system Ti-Ta-(Ti,Ta)xOy. It was found that during electro-spark alloying the concentration of tantalum on the titanium surface ranges from 0.1 to 3.2 at.%. Morphology of the deposited splats is represented by uniformly grown crystals of titanium and tantalum oxides, which increase from nano- to submicron size.

Characterization of Ultrasonic Wire Bonding for LDS MID Prototyping

Functional prototyping during development of new molded interconnect device (MID) products offers benefits such as evaluation of design specifications, validation of manufacturing technologies, and functional testing of the entire product. Introduction of ProtoPaint laser direct structuring (LDS) by LPKF Laser and Electronics AG has opened new possibilities to develop MID prototypes using LDS of additive manufactured plastic parts. In this experimental work, selective laser sintered (SLS) substrates of three different plastic materials-polyether ether ketone, PA12, and Duraform HST-are used to manufacture MID prototypes. These SLS substrates are functionalized by coating with ProtoPaint LDS lacquer, to produce laser-activable surface, followed by subsequent laser activation and electroless chemical plating processes to metallize conductive patterns. The compatibility of this LDS metallization on the MID prototypes toward aluminum wire bonding as a common contacting technology is evaluated. Pretreatment procedures-namely, ultrasonic cleaning in isopropanol solution, ultrasonic cleaning in ethanol solution, plasma treatment using H2 and N2, and coating with 1k plastic primer, 1k plastic filler, and 2k primer filler-are adopted for the blank SLS plastic substrates to further study and improve the coating of ProtoPaint functional layer, which attributes to better metallization of substrates.

Microwave Emission of Carbon Fibres during Electrical Breakdown

A new method of reliability monitoring of electrical devices based on carbon fibres is presented. Due to the thermo-mechanical stress on electronic circuits a loss of fibre network integrity can take place and potential difference may appear between the edges of broken carbon fibres. This potential difference causes an intensive field-emission from surfaces of these broken carbon fibres and an acceleration of emitted electrons. Due to the acceleration of electrons a microwave emission is generated. A CFRP was used to simulate the behaviour of a carbon based electronic device. The sequence of microwave impulses was detected in a frequency bandwidth from 8 to 12 GHz. The rise time of detected microwave impulses is about of few nanoseconds. This time is in agreement with crack formation time in carbon fibre. The correlation between the change of electrical resistance of composites and microwave impulses by fibres fracture is observed. Thus, the breakdown of current that flows through carbon fibres induces detectable microwave emission. That means that defects in electrical circuits can be wireless detected online.