Wyniki wyszukiwania - BazTech

1

Plazmowe utlenianie elektrolityczne aluminium zarys technologii procesu

Gębarowski W., Pietrzyk S.

Rudy i Metale Nieżelazne

|

2012

|

R. 57, nr 4

237-242

PL

Plazmowe utlenianie elektrolityczne pozwala otrzymywać na stopach aluminium tlenkowe warstwy ochronne o wysokich parametrach mechanicznych, znacznie przewyższających powłoki otrzymywane na drodze tradycyjnego anodowania. Jest to spowodowane ich litą strukturą, zawierającą dużą ilość twardych faz krystalicznych Al2O3. Warstwy charakteryzują się bardzo dużą twardością, odpornością na ścieranie, posiadają znakomitą przyczepność do podłoża i dobrą odporność na korozję. Własności otrzymywanych powłok zależą głównie od warunków prądowych oraz składu i temperatury elektrolitu. Wysokie potencjały międzyelektrodowe w trakcie trwania procesu wywołują mikrowyładowania, powodujące przebijanie warstewki utlenionej i występowanie lokalnie bardzo wysokich temperatur, odpowiadających za specyficzną budowę i własności warstwy tlenkowej.

EN

Plasma electrolytic oxidation is the relatively new method of oxide layers formation on aluminium alloys. Plasma electrolytic oxide coatings have more advantageous mechanical properties than coatings obtained in traditional anodizing. It is due to dense structure with high content of hard, crystalline phases of Al2O3. Coatings offer very high hardness, wear resistance, great interfacial adhesion and good corrosion resistance. Thickness of alumina layers can reach up to 300 [mi]m. The final properties of coatings depend on the process parameters like: current conditions, composition and temperature of electrolyte. During the process high potentials occur, which result in electric breakdowns of oxide layer visible as a short duration micro-arcs on whole surface of electrode. These micro breakdowns locally heat up oxide to very high temperatures, which leads alumina fusing. This phenomenon is responsible for the specific morphology of oxide layer. Plasma electrolytic oxidation is environmentally friendly because of high diluted electrolytes are used. Coatings have many applications in industry, especially in areas with particularly high endurance requirements. Additionally this technique gives great possibilities to producing many different composites coatings.

2

Alumina-Ti(C,N) ceramics with TiB2 additives

Putyra P., Podsiadło M., Smuk B.

Archives of Materials Science and Engineering

|

2011

|

Vol. 47, nr 1

27-32

EN

Purpose: The aim of the study presented in this article is to determine the effect of TiB2 addition on the selected properties of ceramic tool materials. The effect of titanium diboride additives on the density, porosity, Young’s modulus and Vickers hardness of Al2O3-Ti(C,N) matrix ceramics was determined. Design/methodology/approach: Al2O3-Ti(C,N) ceramics with TiB2 addition were sintered by SPS method. Materials for SPS sintering were pressed in graphite die with pressure of 35 MPa. The max. pressure was obtained after 10 minutes. Sinter process was operated in nitrogen atmosphere. Density, Vickers hardness and Young’s modulus was determined for these materials. The materials were also subjected to tribological analysis. The results were compared with the properties of Al2O3-Ti(C,N) matrix material. Findings: The use of SPS-method in the production of ceramic materials is possible reduce sintering temperature and sintering time. Depending on the TiB2 additives used, the relative density values of individual materials were in the range of 94.4% to 97.7%. Young’s modulus values for these materials were in the range of 392 GPa to 414 GPa, and Vickers hardness in the range of 1966 to 2225 HV1. The results of tribological analysis showed a friction coefficient value for the matrix material of 0.51. For the other materials, the friction coefficient values were in the range 0.31 to 0.49. Practical implications: Ceramic materials with the addition of titanium diboride may be used in cutting tools. Study of the composition and production technology of such tools allows for the minimisation of the use of liquid cooling lubricants in the machining process and the achievement of higher cutting speeds. Originality/value: Titanium diboride additives were added to the structure, resulting in a reduced coefficient of friction, which was measured at between 61% and 96% of the base material coefficient.

3

The analysis of strength properties of ceramic preforms for infiltration process

Putyra P., Kurtyka P., Jaworska L., Podsiadło M., Smuk B.

Archives of Materials Science and Engineering

|

2008

|

Vol. 33, nr 2

97-100

EN

Purpose: The goal of this work is the optimization of sintering process of the ceramic preforms based on Si3N4 and Al2O3-Ti(C,N) materials. The influence of pore forming additives on porosity, microstructures and compressive strength are investigated. The aim of this study is to obtain the nitrides and carbides base preforms material for the infiltration process of molten aluminium alloys. Design/methodology/approach: The method of obtaining the silicon nitride and oxide-carbonitride porous preform for the infitration process is the free sintering process. The preforms were produced by the mixing of ceramic powders with organic binders, drying and sintering. Porosity, density were measured for the materials. Microstructure observation was carried out using scanning microscope. The compressive strength of Si3N4 and Al2O3-Ti(C,N) porous preforms were investigated. Findings: For sintered porous Si3N4 preforms, influence of the porous forming additives on material porosity is observed. Compressive strengths of Si3N4 were in the range of 2.9-4.8 MPa. The highest value of the compressive strength was obtained for Al2O3-Ti(C,N) preform with 8 wt.% of tylose and 25 wt.% of glykol. For these materials compressive strength were in the range of 13.2 up to 14.3 MPa. In spite of lower value of the compressive strength for Si3N4 preforms, this material exhibits high shock thermal resistance. Practical implications: Pressureless infiltration of molten metals into ceramics is the most cost-effective approach to liquid-metal processing of MMCs. Metal matrix composites are applied widely in aircraft production technologies and defence technology. Originality/value: Infiltration of molten metals into porous ceramic preforms is the only technique suitable for the fabrication of high volume fraction of ceramic materials in MMCs. Infiltration process generates thermal stresses in the ceramics preforms. The thermal shock resistance of Al2O3 is lower than Si3N4 or Al2O3-Ti(C,N) materials. New kinds of porous materials were obtained.

4

Chemometric characterization of the RF values of alkaloids for thin layer chromatographic systems of the type polar adsorbent -- multicomponent eluent

Waksmundzka-Hajnos M., Gadzikowska M.

Chemia Analityczna

|

2001

|

Vol. 46, No. 6

839-848

EN

Chemometric characteristic of several alkaloids of various groups was performed by the relationships of their retention coefficients Re against mpdifier concentration in eluent. Retention of alkaloids was investigated on silica layers using nonaqueous eluents containing different amounts of methanol in dichloromethane or using aqueous eluents (in pseudo-reversed phases) using methanol or acetonitrile as modifiers and 2% of glacial acetic acid. For poorly separated compounds in such systems alumina or magnesium silicate (Florisil) and dichloromethane — methanol mixtures as eluents were used. Selectivity of separation was analyzed by correlation diagramsRM Al vs RMSi and RM (Florisil for data obtained in nonaqueous systems. Presented results as RF vs C % plots or RM(12) diagrams permit to choose selective systems for the separation of particular groups of substances and enable identification and chemometric characterization of investigated alkaloids.

PL

Charakterystyka chemometryczna wielu alkaloidów z różnych grup była przeprowadzona poprzez zależności ich współczynników retencji RF od stężenia modyfikatora w eluencie. Badano retencje, alkaloidów na cienkich warstwach żelu krzemionkowego stosując eluenty niewodne zawierające różne ilości metanolu w dichlorometanie lub przy użyciu eluentów wodnych (układy pseudoodwrócone) przy użyciu metanolu lub acetonitrylu jako modyfikatorów z dodatkiem 2% lodowatego kwasu octowego. Dla słabo rozdzielonych związków w powyższych układach zastosowano układy z tlenkiem glinu lub krzemianem magnezu (Florisil) i mieszaniny dichlorometanu z metanolem jako eluenty. Selektywność rozdzielenia była analizowana grupowo poprzez diagramy korelacyjne RM1 vs RMSI oraz RM si vs RM(Florisil) dla danych uzyskanych w układach bezwodnych. Przedstawione wyniki jako krzywe zależności Rf vs C% lub diagramy korelacyjne RM1 vs RM12 dają możliwość znalezienia selektywnego układu dla rozdziału poszczególnych grup substancji i umożliwiają identyfikacje, i chemometryczną charakterystykę badanych alkaloidów.

5

Activity of molybdena-alumina catalysts in propene metathesis: effect of the catalyst pretreatment and activation

Handzlik J., Ogonowski J.

Polish Journal of Applied Chemistry

|

1999

|

Vol. 43, nr 1-2

47-56

EN

Propene metathesis reaction in the presence of MoOJ/Al2OJ catalytic systems was investigated. The catalysts studied were highly selective and moderately active in propene metathesis at low temperature (303 K). The effect of preliminary thermal treatment and in situ activation on the catalyst activity was studied. Replacement of the standard calcination of the catalyst precursor with heating the precursor under vacuum improved the rate of the metathesis of diluted propene. The influence of the catalyst reduction and subsequent reoxidation on its activity was investigated too. The catalysts studied were characterised by XRD.

6

Mikrowarstwowe kompozyty ceramiczne.

Tomaszewski H., Węglarz H., Boniecki M., Rećko W.M.

Inżynieria Materiałowa

|

1998

|

R. XIX, nr 5

1288-1296

PL

Kompozyty warstwowe o matrycy Y-ZrO2 lub Ce-ZrO2 z warstwami zbudowanymi z tlenku glinu lub mieszaniny tlenku glinu i dwutlenku cyrkonu grubości 10 do 70 mikrometrów wytwarzano metodą przemiennego odwirowania wodnych zawiesin proszków. W obu przypadkach (Y-ZrO2 i CeZrO2) zaobserwowano znaczny wzrost odporności na pękanie i wytrzymałości na zginanie, ale tylko dla warstw barierowych zbudowanych z tlenku glinu. W przeciwieństwie do wyników uzyskanych przez D.B. Marshalla, mechanizm odchylania spękania wydaje się być odpowiedzialny za obserwowane przyrosty własności. Jak się okazało, wielkość kąta odchylenia jest zależna od grubości warstwy tlenku glinu. Wyższe kąty odchylenia pęknięcia, oznaczające dłuższą drogę pęknięcia zaobserwowano dla grubszych warstw. Wielkości kąta odchylenia skorelowano z gradientem naprężeń wewnętrznych obecnych w warstwach tlenku glinu. Źródłem naprężeń wewnętrznych w badanych kompozytach jest różnica we współczynnikach rozszerzalności cieplnej ZrO2 i Al2O3 oraz krystalograficzna anizotropia rozszerzalności cieplnej Al2O3. Trzecim składnikiem naprężeń okazała się być różnica skurczliwości wypalania obu materiałów. Naprężenia wewnętrzne mierzono metodą piezospektroskopową wykorzystującą zjawisko fluorescencji jonu Cr do potęgi +3 będącego naturalnym zanieczyszczeniem tlenku glinu.

EN

Composites of yttria or ceria partially-stabilised zirconia with layers of either alumina or a mixture of 50% by the volume of the alumina or zirconia were produced using a colloidal technique. The method involved sequential centrifuging of solutions containing suspended solutions allowed to form layers with thickness of 10 to 70 mm. In both cases (Y-ZrO2 and Ce-ZrO2), the significant increase in the fracture toughness, work of fracture and bending strength was observed only in the case of the barrier layers made of pure alumina, not made of the mixture. On the contrary to D.B. Marshall's results, the crack deflection in the alumina layers seems to be the main mechanism responsible for the observed improvement of mechanical properties. As it was found a crack deflection angle depends on the alumina layer thickness. Higher deflection angles, what means longer way of a crack through the alumina layer, were observed for the thicker alumina layers. The crack deflection angle was correlated with the gradient of compressive residual stresses present in the alumina layers. The stresses are the result of both the thermal expansion mismatch between alumina and zirconia and the crystallographically anisotropic thermal expansion of the alumina. The shrinkage mismatch was found as the third component of stresses. The residual stress distribution has been measured by piezospectroscopy based on the optical fluorescence from Cr to the +3rd power dopants in the alumina.