Sintering of Cu-Al2O3 nano-composite powders produced by a thermochemical route

Abstract

This paper presents the synthesis of nano-composite Cu-Al2O3 powder by a thermochemical method and sintering, with a comparative analysis of the mechanical and electrical properties of the obtained solid samples. Nano-crystalline Cu-Al2O3 powders were produced by a thermochemical method through the following stages: spray-drying, oxidation of the precursor powder, reduction by hydrogen and homogenization. Characterization of powders included analytical electron microscopy (AEM) coupled with energy dispersive spectroscopy (EDS), differential thermal and thermogravimetric (DTA-TGA) analysis and X-ray diffraction (XRD) analysis. The size of the produced powders was 20-50 nm, with a noticeable presence of agglomerates. The composite powders were characterized by a homogenous distribution of Al2O3 in a copper matrix. The powders were cold pressed at a pressure of 500 MPa and sintered in a hydrogen atmosphere under isothermal conditions in the temperature range from 800 to 900 °C for up to 120 min. Characterization of the Cu-Al2O3 sintered system included determination of the density, relative volume change, electrical and mechanical properties, examination of the microstructure by SEM and focused ion beam (FIB) analysis, as well as by EDS. The obtained nano-composite, the structure of which was, with certain changes, preserved in the final structure, provided a sintered material with a homogeneous distribution of dispersoid in a copper matrix, with exceptional effects of reinforcement and an excellent combination of mechanical and electrical properties.

U ovom radu predstavljena je sinteza nano-kompozitnog praha Cu-Al2O3 termohemijskom metodom i sinterovanjem, uz uporednu analizu mehaničkih i električnih svojstava dobijenih čvrstih uzoraka. Nano-kristalni Cu-Al2O3 prahovi dobijeni su termohemijskom metodom u sledećim koracima: sušenje raspršivanjem, oksidacija polaznih prahova, redukcija vodonikom i homogenizacija. Prahovi su okarakterisani analitičkom elektronskom mikroskopijom (AEM) spregnutom sa spektroskopijom energije rasejanja (EDS), diferencijalnom termijskom i termogravimetrijskom analizom (DTA-TGA) i difrakcijom X-zraka (XRD). Veličina čestica dobijenih prahova iznosila je 20-50 nm, uz znatno prisustvo aglomerata. Kompozitni prahovi karakterišu se homogenom raspodelom Al2O3 u bakarnoj matrici. Prahovi su presovani na hladno pritiskom od 500 MPa i sinterovani u atmosferi vodonika pod izotermskim uslovima u temperaturnom opsegu od 800 do 900 °C u trajanju do 120 min. Karakterizacija Cu-Al2O3 sinterovanog sistema uključivala je određivanje gustine, relativne promene zapremine, električnih i mehaničkih svojstava, ispitivanje mikrostrukture tehnikom SEM, analizom pomoću usmerenog jonskog snopa (FIB) i tehnikom EDS. Dobijeni nano-kompozit, čija je struktura, uz izvesne promene, prisutna i u konačnoj strukturi sinterovanog materijala, omogućava homogenu raspodelu disperzoida u bakarnoj matrici sinterovanog materijala, sa izraženim efektima ojačanja, i odličnu kombinaciju mehaničkih i električnih svojstava.