Porous sample were fabricated by sintering of bronze ( Cu Sn10) with different particle size range. The paper investigates the influence of the particle size distribution, temperature and sintering time on the structural characteristics (porosity, pore size, dimensional changes) of the porous parts studied. A porous structure with small-sized pores and a uniform distribution of the pore sizes is obtained in conditions of a narrow range of particle size distribution, small size of the powder particles and optimal sintering parameters

G. BATIN

I. VIDA-SIMITI

N. JUMATE

T. BOLOG

The Annals of “Dunarea de Jos” University of Galati Fascicle IX Metallurgy and Materials Science

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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
FASCICLE IX METALLURGY AND MATERIALS SCIENCE, ISSN 1453 – 083X. NR 2 – 2005 
 
 
  
 
EXPERIMENTAL RESEARCH OF SINTERED POROUS  
MATERIALS OF BRONZE POWDERS 
 
I.VIDA-SIMITI, N. JUMATE, T. BOLOG, G. BATIN 
 
Technical University of Cluj-Napoca, 
e-mail: ivida@personal.ro
 
ABSTRACT 
 
Porous sample were fabricated by sintering of bronze ( Cu Sn10) with 
different particle size range. The paper investigates the influence of the particle size 
distribution, temperature and sintering time on the structural characteristics 
(porosity, pore size, dimensional changes) of the porous parts studied. A porous 
structure with small-sized pores and a uniform distribution of the pore sizes is 
obtained in conditions of a narrow range of particle size distribution, small size of 
the powder particles and optimal sintering parameters. 
 
       KEYWORDS: porous materials, sintering materials, bronze powders. 
 
 
1.Introduction 
 
 Porous elements obtained by Powder 
Metallurgy methods are used with excellent results as 
filters, flame arresters, noise suppressors, distributors 
of gases in fluids, electrochemical catalyzers etc.  
 A uniform porous structure with small sized 
pores ensures the main conditions required for these 
applications. 
 Structural parameters (porosity and size of 
pores) are influenced by the following technological 
processing parameters: the powder size range, 
compacting pressure, sintering temperature, sintering 
time [1,2,3,5,6,7]. A previous paper [8] studied the 
influence of the compacting pressure on the porous 
structure parameters of permeable sintered materials 
from 316 L stainless steel powder.  
 This study provides new comparative results 
regarding the influence of powder size ranges of free 
bronze sintered powder on the permeable porous 
structure in conditions of changing the sintering time . 
 
2.Experimental  method 
 
 Porous samples in the shape of disc tablets, 25 
mm diameter and approximately 2 mm thickness, 
were made by sintering from free bronze powder 
poured into a matrix. The powder size ranges and 
thesintering time  were the technological parameters 
that were changed in order to study their influence on 
the main structural characteristics. 
Sintering was performed in a vacuum oven 
(5*10-5 torr) at a relatively low temperature of 7500C 
in order to ensure the intercommunicating 
characteristic of the pores and to avoid their closure 
in case of intensive sintering conditions. 
 The powder size ranges obtained by sifting and 
selected for the samples were: -40 µm; (+40 - 63) µm; 
(+63 - 80) µm; (+80 - 100) µm; (+100 - 125) µm; 
(+125 -160) µm. 
 During sintering the samples were maintained 
for 30, 45 and 60 minutes. 
 The porous structure was examined by a 
scanning electron microscpe (JEOL 5600 LV) and 
microphotos were obtained. The porosity of the 
samples with regular geometric shape was determined 
by calculation, based on their weight and calculated 
volume. 
 
3.Results and discussion 
 
 Experimental sintering tests were performed at 
8500C, according to prescriptions found in literature   
[6]. It was found that the powder samples of high 
powder size ranges were melted and underwent 
marked contractions (fig.1). 
 Using the temperature of 7500C, sintering was 
performed for 30, 45 and 60 minutes. It was found 
that at sintering time s of more than 45 min. the 
powder size ranges (100 - 125 µm; 125 -160 µm) 
were highly contracted (fig.2). 
 This may be explained by the fact that with 
vacuum sintering the heat transfer is mainly by 
thermic radiation. Due to the high porosity of the free 
powder having a powder size  between 100 - 125 µm 
and 125 -160 µm, the “absorbant black body” 
phenomenon occurs. 
 A certain part of the thermic radiation is 
absorbed by the sample material, a part is reflected by 
the sample surface and another part penetrates into 
the pore cavity where heat accumulates, leading to the 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
FASCICLE IX METALLURGY AND MATERIALS SCIENCE, ISSN 1453 – 083X. NR 2 – 2005 
 
 
  
local temperature increase. The diffusion process at 
the level of the sintered bridges is enhanced. The 
increase of the temperature by 200C practically 
doubles the diffusion coefficient and triggers the 
transfer of material around the bridges between 
particles. Consequently, the effect of local 
temperature increase following the heat transmission 
by radiation leads to intensified sintering, reduction 
of porosity and increase of contractions. 
 
 
 
Fig. 1. Bronze powder samples sintered at 8500C 
 
 
 
Fig. 2. Bronze powder samples sintered  
at 7500C 
  
 This accounts for the high contraction in the 
powder samples with powder size s between 100 – 
160 µm. 
 Figure 3 graphically presents the influence of 
the sintering time  on the total contraction of samples 
for all the powder size rangees studied at a constant 
sintering temperature (7500C). High contractions may 
be noted with powder size rangees (+100 - 125) µm; 
(+125 -160) µm.  
30 35 40 45 50 55 60
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Tsint=750
0C
(vacuum)
 -40[µm]
 +40-63[µm]
 +63-80[µm]
 +80-100[µm]
 +100-125[µm]
 +125-160[µm]
 
 
C
on
tr
ac
tio
n 
[%
]
Sintering time [min]
Fig. 3. The influence of sintering time  and 
powder size  on the contraction 
0 10 20 30 40 50 60
10
20
30
40
50
60
70
Tsint=750
0C
(vacuum)
 -40[µm]
 +40-63[µm]
 +63-80[µm]
 +80-100[µm]
 +100-125[µm]
 +125-160[µm]
Sintering time [min]
 
 
Po
ro
si
ty
 [%
]
Fig. 4. The influence of sintering time 
 and powder size  on the porosity 
30 35 40 45 50 55 60
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
Tsint=750
0C
(vacuum)
 -40[µm]
 +40-63[µm]
 +63-80[µm]
 +80-100[µm]
 
 
M
ax
  p
or
e 
 s
iz
e 
[μ
m
]
Sintering time [%]
Fig. 5. The influence of sintering time 
 and powder size  on the maximal pore size 
  
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
FASCICLE IX METALLURGY AND MATERIALS SCIENCE, ISSN 1453 – 083X. NR 2 – 2005 
 
 
  
 A more marked reduction of the porosity in the 
-40 µm powder size range (fig. 4) may be accounted 
for by the initially higher degree of packing of the 
small particles. The same findings are expressed by 
figs. 5 and 6, which show the variation of the size of 
the largest pore and the average pore size respectively 
in relation to the sintering time . The pore size 
undergoes small, even insignificant changes when 
sintering time  increases. The mechanism of material 
transfer around the inter-particle bridges during 
sintering is not very intense. Consequently the pore 
size does not decrease too much with sintering time. 
30 35 40 45 50 55 60
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
Tsint=750
0C
(vacuum)
 -40[µm]
 +40-63[µm]
 +63-80[µm]
 +80-100[µm]
 
 
M
ax
 p
or
e 
si
ze
 [μ
m
]
Sintering time [%]
 
Fig. 6. The influence of the sintering times and 
powder powder size  on the average pore size 
  
 
 
 
 
Fig. 7. SEM image (x 500) of the bronze porous 
structure (45 mon.) 
 The SEM images (fig.7) of the porous structures 
evidence the fact that the pore size and the inter-
particle bridges reduction are not significantly 
changed. However, it may be noticed that the particle 
surface is smooth, following the material transport 
into the superficial layer by sintering. The surface 
defects and the roughness disappear following the 
sintering mechanisms. 
 Fig. 7 shows the image of the porous structure 
of the sample made of +63 – 80 µm granulometric 
powder sintered for 45 minutes. 
 The images evidence the inter-particle bridges 
formed after sintering only in the small areas of initial 
contacts between the free powder particles. 
 The narrow powder size ranges, formation by 
free spreading into the mold as well as the relatively 
low sintering temperature (7500C) ensures a uniform 
porous structure with intercommunicating pores, 
favourable to fluid flow and filtration. 
 
Conclusions 
 
 The sintering time  has a marked influence on 
the porous structure parameters (porosity, pore size) 
in the case of the samples sintered from free bronze 
powder with (-100 – +160) μm.powder size . 
 Thesintering time  does not influence the porous 
structure parameters (porosity, pore size) significantly 
in the samples obtained from free powder with (-40 – 
100) μm powder size . 
 By sintering the powder particle surface 
becomes smooth, due to the transport of substance 
into the superficial layer of the material. 
 
References 
 
[1]. Albano-Müller, Filter Elements of Highly Porous Sintered 
Metals, Powder Metallurgy International, 1982, 14, 2, 73-79. 
[2]. M. Bram, H. P. Buchkremer, D. Stöker, Development of 
Porous Composites Membranes for Microfiltration Devices, 
Conference Proceedings, Euro P M 2004, 183-188. 
[3]. I. N. Podrezov, Structural Engineering of High-Porous PM 
Materials, Conference Proceedings, EuroPM 2004, 125 – 130. 
[4]. P. Neuman, Porous Metal Structures Made by Sintering 
Processes and Applications, Mat. Wiss. u. Werkstofftechn, 2000 
(31), 422. 
[5]. O. I. Getman, L. I. Chernysher, The Porous Structure of a 
Permeable Nickel Material with a Bimodal Pore – Size 
Distribution, Powder Metallurgy and Metal Ceramics, 2003, 
(42),11-12, 630-637. 
[6]. I. Vida-Simiti, Sintered Permeable Materials (in roumanian), 
Ed. Casa Cărţii de Ştiinţă, Cluj-Napoca, 1998. 
[7]. A. Palfalvi, I. Vida-Simiti, I. Chicinaş, Influence of Porosity 
on the Mechanical Characteristics of Sintered Porous Stainless 
Sheets, Powder Metallurgy International, 1998, 4, 16-19. 
[8]. I. Vida-Simiti, Researches on Some Characteristics of The 
Permeable Porous Structures from Sintered Powders (in 
roumanian), Construcţia de Maşini, Bucureşti, 1997, 11, 1-4. 
 
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Experimental Research of Sintered Porous Materials of Bronze Powders

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Experimental Research of Sintered Porous Materials of Bronze Powders

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