=Paper=
{{Paper
|id=Vol-1638/Paper12
|storemode=property
|title=Determination of conditions for nanoporous structure formation in a metallic material by pulse-periodic laser action
|pdfUrl=https://ceur-ws.org/Vol-1638/Paper12.pdf
|volume=Vol-1638
|authors=Serguei P. Murzin,Artur I. Safin,Artrem A. Shimanov,Maxim V. Blokhin,Sergey A. Afanasiev
}}
==Determination of conditions for nanoporous structure formation in a metallic material by pulse-periodic laser action ==
https://ceur-ws.org/Vol-1638/Paper12.pdf
Computer Optics and Nanophotonics
DETERMINATION OF CONDITIONS FOR
NANOPOROUS STRUCTURE FORMATION IN A
METALLIC MATERIAL BY PULSE-PERIODIC
LASER ACTION
S.P. Murzin, A.I. Safin, A.A. Shimanov, M.V. Blokhin, S.A. Afanasiev
Samara National Research University, Samara, Russia
Abstract. Determination of spectrums of samples responses on external vibro-
excitation via pulse-periodic laser action by CO2 laser ROFIN DC 010 and reg-
istration of their wave forms have been performed. While analysing the sam-
ples’ responses using pulse-periodical laser action, it has been found that vibra-
tion rate increases in the case of frequencies, which are divisible by the fre-
quency of initial oscillation, during the amplitude decrease and the frequency
increase. The dependence of heat rate on the nanoporous structure formation in
the absence of the metallic material melting has been researched. While heating
the sample, its temperature was highest at its centre. An increase of the laser ac-
tion time led to a rise in the temperature of the sample’s centre, causing the rate
of pore formation has increased. Since the diffusion coefficient is related to the
temperature through an exponential law, the temperature rise is an effective
way to increase rate of the process. However, non-permanent elastic defor-
mation, which is caused by high-powered external action, is a necessary condi-
tion for developing a generic thermodynamic moving force, which increases the
rate of nanoporous structure formation in metallic material.
Keywords: formation, nanoporous structure, laser action, metallic material,
frequency, vibration rate, temperature.
Citation: Murzin SP, Safin AI, Shimanov AA, Blokhin MV, Afanasiev SA.
Determination of conditions for nanoporous structure formation in a metallic
material by pulse-periodic laser action. CEUR Workshop Proceedings, 2016;
1638: 89-94. DOI: 10.18287/1613-0073-2016-1638-89-94
Introduction
The use of pulse-periodic laser action is a progressive way of forming nanoporous
layers on the surface of metallic materials. Conditions for formation of such layers in
two-component Cu-Zn alloy brass L62 with a 60.5–63.5% coppercontent have been
defined in printed works [1-3]. It is stated that as a result of the laser action, single
nanopores, as well as ones that form branched channels, appear in the near-surface
Information Technology and Nanotechnology (ITNT-2016) 89
Computer Optics and Nanophotonics Murzin SP, Safin AI, Shimanov AA, et al…
layer and on the surface. Both are uniformly distributed on the area [4, 5]. Such struc-
tures develop via appearance of vacant sites and their coagulation is a result of Zn
sublimation from the material surface, inducing a concentration gradient and diffusion
of this component with higher vapour tension at the surface [6-8]. Non-permanent
local deformation, caused by high-powered external action, is a condition for intensi-
fication of mass transfer in the solid phase of metallic materials [9-11]. At that, laser
action with pulse-periodic radiation allows a persistent stress condition to develop on
the surface of the samples [12, 13]. In order to redistribute the power density in the
cross-sectional area of the laser beam, the use of a diffractive optical element – fo-
cusator of laser radiation, is expedient [14–17]. The aim of this work is to define the
conditions for formation of nanoporous structure in metallic materials via pulse-
periodic laser action.
Pulse-periodic laser action on the metallic material
Samples of Cu-Zn alloy brass L62 with dimensions of 30x20x0.05 mm have been
researched. Spectra of the samples’ responses to external vibroexcitation via pulse-
periodic laser action have been measured and their wave forms have been defined.
Power action has been performed by a ROFIN DC 010 CO2 laser with adjustable
output power range of 100-1000 W. A three-component scanning laser vibration-
measuring instrument Polytec® PSV-400-3D was used to measure the vibration rate.
The instrument has three scanning heads, each of them fitted with an interferometer
and video camera, as well as a PC and three data management controllers. Data man-
agement has been synchronized by PSV 3D software, the user interface is used for
visualization of dynamic processes in the form of animated 3D oscillation distribu-
tions in the investigated frequency range. Pulse-periodic laser action has been per-
formed with frequencies of 100, 500, and 5000 Hz. After the analysis of the samples’
responses on the described external vibroexcitation, it has been found that vibration
rate increases in case of frequencies, which are divisible by the frequency of initial
oscillation, during the amplitude decrease and the frequency increase. Fig. 1 shows
images of the sample, which have been re-established with the use of PSV Presenta-
tion software. The oscillation shape corresponds to a frequency of 500 Hz. It has been
defined that maximum vibration rate occurs on the periphery of the sample; however,
the intensity of the pore formation is much lower here than in centre.
A Mikron M7604F thermovision camera was used to research the heating of the sam-
ples via laser action. Fig. 2 shows the temperature field of the sample under pulse-
periodic laser action. The highest temperature of the sample was in its centre. An
increase of the laser action time led to a rise in temperature of the sample’s centre
area, du to this, an intensity of pore formation increased. The dependence of the heat-
ing on the nanopores structure formation in the absence of the metallic material melt-
ing has been researched. Inasmuch as the diffusion coefficient is related to the tem-
Information Technology and Nanotechnology (ITNT-2016) 90
Computer Optics and Nanophotonics Murzin SP, Safin AI, Shimanov AA, et al…
perature of an exponential law, the temperature rise is an effective way to increase the
atoms mobility. However, non-permanent elastic deformation, which is caused by
high-powered external action, is a necessary condition for development of generic
thermodynamical moving force, which provides an intensification of the nanoporous
structure formation in a metallic material.
Research of the material's fine structure
Fine structure of the material has been researched with the use of a scanning electron
microscope, VEGA \\ SB, Tescan. It was found that the laser action creates nanopo-
rous structures in near-surface layer. Channel type nanopores ~100 nm wide, which
organize nanoporous network, mainly appear. Dimensions and shapes of the na-
nopores, equally distributed on the surface of subgrains, are relatively stable.
Fig. 1. Images of the sample, which have been re-established with the use of PSV Presentation
software and which correspond to the frequency of 500 Hz; time step is 0.2 ms
Information Technology and Nanotechnology (ITNT-2016) 91
Computer Optics and Nanophotonics Murzin SP, Safin AI, Shimanov AA, et al…
Fig. 2. Temperature field of the sample during its pulse-periodic laser action
Fig. 3 shows image of characteristic nanopore up to 100 nm wide, which organize
into a nanoporous network in the metallic material during its pulse-periodic laser
action. The main mechanism of nanoporous structure formation is the sublimation of
the component with higher vapour tension; in this case it is Zn. A concentration gra-
dient is set up in the material and this component sublimates with the surface to the
extent to which diffusion of it to the surface from the inner layers is provided. In time,
the thickness of the Zn depleted layer increases and the diffusion becomes a limiting
factor of the sublimation process. Non-permanent local deformation, caused by high-
powered external action, is a condition for intensification of mass transfer inthesolid
phase of metallic materials. Inasmuch as the diffusion coefficient is related to the
temperature of an exponential law, the temperature rise is an effective way to increase
the intensity of the process.
Fig. 3. Image of a ~100 nm wide nanopore formed as a result of laser action on the sample’s
metallic surface
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Computer Optics and Nanophotonics Murzin SP, Safin AI, Shimanov AA, et al…
Conclusion
In analysing of the samples’ responses to pulse-periodical laser action, it has been
found that the vibration rate increases in case of frequencies, which are divisible by
the frequency of initial oscillation, during the amplitude decrease and the frequency
increase. While heating the sample, its temperature was highest at its centre. An in-
crease of the laser action time led to a rise in temperature of the sample’s centre area,
due to this, an intensity of pore formation increased. Non-permanent local defor-
mation, caused by high-powered external action, is a condition for intensification of
mass transfer in the solid phase of metallic materials. Inasmuch as the diffusion coef-
ficient is related to the temperature of an exponential law, the temperature rise is an
effective way to increase the intensity of the process. The further research will be
connected to the definition of self-resonant frequencies and shapes of the oscillations.
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