Properties of zirconium and hafnium

Zir­co­ni­um is known for its excep­tion­al cor­ro­sion resis­tance, heat resis­tance and chem­i­cal inert­ness, due to which it is wide­ly used in the nuclear, chem­i­cal, aero­space, and ceram­ic indus­tries. Hafni­um, in turn, has the abil­i­ty to effec­tive­ly absorb neu­trons, which makes it an indis­pens­able mate­r­i­al in nuclear reac­tor struc­tures, in the pro­duc­tion of elec­tron­ics, as well as in the cre­ation of heat-resis­tant alloys for high-tem­per­a­ture sys­tems.

Research into the prop­er­ties, extrac­tion tech­nolo­gies, sep­a­ra­tion and prac­ti­cal appli­ca­tion of these met­als is extreme­ly impor­tant for the devel­op­ment of mod­ern sci­ence and indus­try. This is espe­cial­ly rel­e­vant to the ener­gy sec­tor, avi­a­tion, the space indus­try, and high-pre­ci­sion engi­neer­ing, where hafni­um and zir­co­ni­um ensure the sta­bil­i­ty and reli­a­bil­i­ty of struc­tures under the most extreme oper­at­ing con­di­tions.

Due to their high heat resis­tance, low coef­fi­cient of ther­mal expan­sion, and resis­tance to chem­i­cal reagents, zir­co­ni­um con­cen­trates are wide­ly used in foundry pro­duc­tion as mold­ing mate­ri­als. Zir­co­ni­um refrac­to­ries have found suc­cess­ful appli­ca­tion in fer­rous met­al­lur­gy, where they ensure a con­tin­u­ous steel cast­ing process. In the glass indus­try, such mate­ri­als make it pos­si­ble to increase the ser­vice life of fur­naces sev­er­al times and raise the melt­ing tem­per­a­ture to 1600 °C. In the ceram­ic indus­try, zir­co­ni­um con­cen­trates are used for the pro­duc­tion of fac­ing and façade tiles, while zir­co­ni­um-con­tain­ing abra­sives sur­pass corun­dum ones in tech­no­log­i­cal char­ac­ter­is­tics, pro­vid­ing more effec­tive grind­ing.

In met­al­lur­gy, zir­co­ni­um and its alloys are used as alloy­ing addi­tives to stain­less and heat-resis­tant steels, which sig­nif­i­cant­ly increas­es their strength and endurance. Zir­co­ni­um is also an excel­lent deox­i­diz­er, more effec­tive than man­ganese and tita­ni­um. Due to its abil­i­ty to absorb gas­es at high tem­per­a­tures, pow­dered zir­co­ni­um is used to main­tain a high vac­u­um in instru­ments. High-strength ceram­ic mate­ri­als are cre­at­ed on the basis of this met­al, from which com­po­nents for high-effi­cien­cy diesel engines are man­u­fac­tured. Zir­co­ni­um diox­ide is active­ly used in the pro­duc­tion of piezo­elec­tric ele­ments, fil­ters, and ceram­ic capac­i­tors.

The main share of the pro­duced metal­lic zir­co­ni­um is con­sumed in nuclear ener­gy, because it has a small ther­mal neu­tron cap­ture cross-sec­tion, a high melt­ing point and excel­lent anti-cor­ro­sion prop­er­ties. This makes zir­co­ni­um an ide­al mate­r­i­al for mak­ing nuclear reac­tor fuel cell shells.

Genesis

Zir­co­ni­um and hafni­um have a com­mon geo­chem­i­cal nature, belong to lithophile ele­ments, and usu­al­ly accom­pa­ny each oth­er in most geo­log­i­cal process­es. They are con­cen­trat­ed main­ly in the late dif­fer­en­ti­ates of mag­mat­ic sys­tems, where the dis­tri­b­u­tion of ele­ments with high charge and small ion­ic radii occurs. The for­ma­tion of zir­co­ni­um and hafni­um is close­ly asso­ci­at­ed with the crys­tal­liza­tion of gran­i­toids, nepheline syen­ites, peg­matites, and oth­er acidic or alka­line mag­mas. In resid­ual melts enriched in flu­o­rine, chlo­rine, and rare ele­ments, the min­er­al zir­con forms, in whose crys­tal lat­tice hafni­um, with its sim­i­lar ion­ic size, eas­i­ly sub­sti­tutes for zir­co­ni­um through iso­mor­phic replace­ment.

The fur­ther evo­lu­tion of these min­er­als occurs under meta­mor­phic and hydrother­mal con­di­tions, where zir­con may recrys­tal­lize or under­go dis­so­lu­tion and sub­se­quent pre­cip­i­ta­tion. Dur­ing the weath­er­ing of rocks, resis­tant min­er­als con­tain­ing zir­co­ni­um and hafni­um are not destroyed but accu­mu­late in sec­ondary plac­ers. Such sed­i­men­ta­ry deposits are the main sources of indus­tri­al zir­co­ni­um extrac­tion in the world.

Thus, the gen­e­sis of zir­co­ni­um and hafni­um encom­pass­es the full spec­trum of geo­log­i­cal process­es — from pri­ma­ry mag­mat­ic crys­tal­liza­tion to sec­ondary enrich­ment in coastal-marine or con­ti­nen­tal plac­er deposits. This sequence reflects the long-term his­to­ry of the redis­tri­b­u­tion of ele­ments in the lithos­phere, which deter­mines their present-day indus­tri­al sig­nif­i­cance.

Distribution in Ukraine

Ukraine has sig­nif­i­cant reserves of zir­co­ni­um and hafni­um, which makes it pos­si­ble to con­sid­er it one of the lead­ing coun­tries in the world in this field. The aver­age con­sump­tion of zir­co­ni­um and its com­pounds is about 90 tons per year and is ful­ly pro­vid­ed by own pro­duc­tion.

Reserves of these ele­ments are rep­re­sent­ed by both pri­ma­ry and plac­er deposits, con­cen­trat­ed main­ly in the cen­tral and north­east­ern parts of the Ukrain­ian crys­talline shield, as well as in the south­east­ern sec­tor of the Dnipro-Donet­sk depres­sion. The scale and vari­ety of deposits indi­cate that Ukraine is one of the lead­ing zir­co­ni­um-hafni­um provinces in the world. The Azov megablock is espe­cial­ly promis­ing, where alka­line igneous rocks, meta­so­matites, weath­er­ing crusts and plac­er deposits enriched with zir­con and badeleite are com­mon.

All deposits of Ukraine with indus­tri­al con­cen­tra­tions of zir­co­ni­um and hafni­um are com­plex in nature, so these ele­ments are often mined as asso­ci­at­ed min­er­als, and hafni­um is obtained from zir­co­ni­um con­cen­trate. There are cur­rent­ly 16 deposits on the state bal­ance sheet (3 indige­nous, 8 plac­er and 5 man-made).

Among the main min­ing objects are the Maly­shev and Vovchan­sk nat­ur­al deposits of the Dnipropetro­vsk region and the man-made Bal­ka Kru­ta deposit of the Zapor­izhia region, and the Berezivs­ka, Yurivsko-Kozi­ivs­ka and Azov areas are con­sid­ered promis­ing. The most com­mon geo­log­i­cal and indus­tri­al type in Ukraine are zir­con-con­tain­ing plac­er deposits, among which Malyshiv­ske today remains the main source of sup­ply of zir­co­ni­um and hafni­um con­cen­trates.

The Vovchanske deposit, locat­ed near­by, serves as a reserve for the Vil­no­hirsk Min­ing and Met­al­lur­gi­cal Com­bine and is char­ac­ter­ized by a high zir­con con­tent (up to 90% in the heavy frac­tion). It belongs to the most favor­able deposits in terms of zir­con con­tent, although it is rel­a­tive­ly small in terms of heavy min­er­al reserves. The thick­ness of ore lay­ers aver­ages 4.7–8 m. The min­er­al com­po­si­tion of the ore sands is sim­i­lar to that of the sands of the Maly­shevske deposit.

The Yas­tru­bet­sk deposit is con­fined to the sien­ite mas­sif of the same name of Meso­pro­tero­zoic age, locat­ed in the extreme north­west of the Ukrain­ian shield (Zhy­to­myr region). Ore min­er­al­iza­tion is local­ized in the endo­con­tact zone of the mas­sif, where it forms up to 10 ore bod­ies, the main ore min­er­al of which is zir­con, rare earth min­er­als are also present, in par­tic­u­lar bast­ne­site, which makes it pos­si­ble to clas­si­fy the deposit as com­plex.

Thus, hafni­um and zir­co­ni­um are strate­gi­cal­ly impor­tant met­als for mod­ern indus­try. Zir­co­ni­um is indis­pens­able in the pro­duc­tion of heat-resis­tant alloys, ceram­ics, and struc­tur­al mate­ri­als for nuclear ener­gy, while hafni­um is used in the cre­ation of con­trol ele­ments for reac­tors, ultra-strong alloys, and elec­tron­ic com­po­nents. Fur­ther devel­op­ment of tech­nolo­gies for the extrac­tion, purifi­ca­tion, and sep­a­ra­tion of these met­als will con­tribute to the ratio­nal use of nat­ur­al resources, increase indus­tri­al effi­cien­cy, and expand sci­en­tif­ic research in strate­gi­cal­ly impor­tant fields.