Development of a novel electrolytic process for producing high-purity magnesium metal from magnesium oxide using a liquid tin cathode

Te-Hyuk Lee,Toru H.Oke,Jin-Young Lee,c,Young Min Kim,Jungshin Kng,c,*

a Korea Institute of Geoscience and Mineral Resources,124 Gwahak-ro Yuseong-gu,Daejeon 34132,Republic of Korea

b Institute of Industrial Science,The University of Tokyo,4-6-1 Komaba,Meguro-ku,Tokyo 153-8505,Japan

c University of Science and Technology,217 Gajeong-ro Yuseong-gu,Daejeon 34113,Republic of Korea

d Korea Institute of Materials Science,797 Changwondae-ro,Seongsan-gu,Changwon,Gyeongnam,51508,Republic of Korea

Abstract The current electrolytic processes for magnesium(Mg)metal have several disadvantages,such as anhydrous magnesium chloride(MgCl2)preparation and generation of harmful chlorine(Cl2)gas.To overcome these drawbacks,a novel Mg production process to produce high-purity Mg metal directly from magnesium oxide(MgO)was investigated in this study.The electrolysis of MgO was conducted using a liquid tin(Sn)cathode and a carbon(C)anode in the eutectic composition of a magnesium fluorid(MgF2)-lithium fluorid(LiF)molten salt under an applied voltage of 2.5V at 1053-1113K.Under certain conditions,the Mg-Sn alloys with Mg2Sn and Mg(Sn)phases were obtained with a current efficien y of 86.6 % at 1053K.To produce high-purity Mg metal from the Mg-Sn alloy,vacuum distillation was conducted at 1200-1300K for a duration of 5-10h.Following the vacuum distillation,the concentration of Mg in the Mg-Sn alloy feed decreased from 34.1 to 0.17 mass%,and Mg metal with a purity of 99.999 % was obtained at 1200K.Therefore,the electrolytic process developed here is feasible for the production of high-purity Mg metal from MgO using an efficien method.? 2021 Chongqing University.Publishing services provided by Elsevier B.V.on behalf of KeAi Communications Co.Ltd.This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/)Peer review under responsibility of Chongqing University

Keywords:Magnesium;Magnesium oxide;Electrolytic process;Liquid tin cathode;Vacuum distillation.

1.Introduction

Magnesium(Mg)is well known for its superior physical properties,such as its lightweight,high specifi strength,high stiffness,and good damping capacity.These attractive properties make it very useful in diverse field such as transportation,electronics,and other industrial field[1,2].In particular,the demand for Mg will increase in the automobile industry to improve fuel efficien y and reduce carbon dioxide(CO2)gas emissions[3].

Fig.1 shows an outline of the materials fl w for the commercial processes to produce primary Mg metal[4-6].As shown in Fig.1,Mg is produced commercially either through the thermal reduction or electrolytic method.Approximately 81 % of global primary Mg metal is produced by smelters in China using the thermal reduction process,known as the Pidgeon process.The Pidgeon process is based on the thermal reduction of calcined dolomite(MgO·CaO)at 1373-1473K under vacuum,with ferrosilicon(Fe·Si)as a reducing agent.The reduced Mg vapor is collected as a Mg crown(metal deposit)in a condenser[6-8].However,the Fe·Si is produced through the carbothermic reaction at 1823K[8],which is an energy-intensive process.In addition,the use of coal as a heat source generates a large amount of sulfur oxide(SOx)gas.Furthermore,there are disadvantages such as high labor requirements and lower productivity[6,9,10].

The electrolytic process is based on the molten salt electrolysis of anhydrous magnesium chloride(MgCl2)or carnallite(MgCl2·KCl)at 928-993K,derived from brines,as shown in Fig.1[6].As a result,liquid Mg metal and chlorine(Cl2)gas are produced at the cathode and anode,respectively.The Magcorp[11],DSM[12],and VAMI processes[13]are the commercial Mg production processes.However,the electrolytic process also has several disadvantages such as the high capital cost,generation of Cl2gas,and high energyintensity for the preparation of MgCl2[4,6].Thus,thermal reduction and electrolytic processes used to commercially produce Mg metal are energy-intensive and cause several environmental risks such as SOxand Cl2gas generation.

Fig.1.Flowchart of the commercial processes for the production of primary Mg metal:(a)DSM/VAMI,(b)Magcorp,(c)Pidgeon,and(d)Bolzano processes.

Several studies have been conducted to resolve the drawbacks of the commercial Mg production processes.Most of them focused on the aspects of an eco-friendly and efficien Mg production.Wada et al.[14]investigated the Pidgeon process using a microwave instead of coal.In addition,Aviezer et al.[15]suggested a silicothermic reduction of magnesium oxide(MgO)obtained from seawater using the ion-exchange method.However,these processes still used Fe·Si as a reducing agent.Several researchers have suggested the use of solar thermal energy to reduce energy consumption.However,Mg metal production using solar thermal energy does not make economic effects[16,17].

Among the several processes,the solid oxide membrane(SOM)process is promising owing to its environmentalfriendly Mg production.The SOM process was developed to produce Mg metal from MgO using a yttria-stabilized zirconia(YSZ)membrane.In the SOM process,MgO dissociates into Mg metal and oxygen(O2)gas during the electrolysis.Oxygen anions migrated through the YSZ membrane and are oxidized at the silver(Ag)anode.Therefore,the preparation of MgCl2is not necessary,and O2gas evolves at the anode.However,the current efficien y decreased from 90 to 40-50 % when the electrolysis continues without argon(Ar)gas bubbling.In addition,the degradation of the YSZ membrane occurs during the electrolysis without the decrease of the partial pressure of Mg in flu[18-20].

Proof-of-concept of the molten salt electrolysis of MgO using liquid metal cathode was investigated by the authors[21].In this study,for the production of high-purity Mg metal directly from MgO feed without the use of MgCl2feed,the efficien molten salt electrolysis of MgO using a liquid tin(Sn)cathode in a simple electrolytic cell and the vacuum distillation of Mg alloys were investigated.Fig.2 shows the fl wchart and schematic diagram of the novel Mg production process investigated in this study.Because MgO is used as a feedstock,the production of anhydrous MgCl2via an energyintensive method is not necessary,and the generation of Cl2gas during electrolysis can be prevented.The use of liquid Sn cathode can hinder the reaction between Mg metal and generated gas such as O2at the anode because Mg-Sn alloy with high-density is produced on the bottom of the electrolytic cell.Owing to the use of the liquid Sn cathode,a simple electrolytic cell,similar in structure to that used in the Hall-Heroult process,was employed in this study.Finally,highpurity Mg metal containing a low concentration of iron(Fe)can be obtained owing to the vacuum distillation.

2.Experimental

2.1.Cyclic voltammetry

The materials used in this study are listed in Table 1,and a schematic diagram and photographs of the experimental apparatus used for cyclic voltammetry(CV)measurements is shown in Fig.3.The eutectic composition of magnesium flu oride(MgF2)and lithium fluorid(LiF)was used as the electrolyte and MgO was added as the Mg feedstock.Prior to their use,MgF2and LiF were dried for more than 72h at 453K in a vacuum oven(Model no.:VOS-601SD,EYELA)and MgO was dried for more than 72h at 343K using an air oven.To prepare the experiment,the mixture of MgF2-LiF or MgF2-LiF-MgO was placed in a carbon(C)crucible.In addition,50g of Ag shot was placed at the bottom of the crucible to absorb the metals generated during the preelectrolysis.The crucible was placed inside a stainless-steel reactor,and the electrodes that were assembled with the top flang were set up with the reactor,as shown in Fig.3(b)and(c).Then,the reactor was installed in the electric furnace.A molybdenum(Mo)wire and C rod were used as the working and counter electrodes,respectively during a cathodic sweep.Meanwhile,C rod and Mo wire were used as the working and counter electrodes,respectively during an anodic sweep[22].A platinum(Pt)wire was used as the quasi-reference electrode.

Table 1Materials used in this study.

Table 2Experimental conditions for electrolysis of MgO using a liquid Sn cathode in a MgF2-LiF molten salt.

Fig.2.A novel Mg metal production process investigated:(a)fl wchart and(b)schematic diagram.

After the assembly was finished the reactor was evacuated for 10min,and the reactor was fille with Ar gas(purity:99.9999 %)until the internal pressure reached 1 atm.After the fina fillin with Ar gas,Ar gas fl wed at a controlled rate using a mass fl w controller(MFC)while the internal pressure of the reactor was maintained at 1 atm.Then,the temperature was increased and kept at 773K for 24h to remove all residual moisture in the mixture of MgF2-LiF or MgF2-LiF-MgO.Subsequently,the temperature was increased and kept at 1083K,and the CV measurements were performed using the potentiostat(Model no.:VMP3,booster:VMP3B,2 A-20V,Biologic Science Instruments).

2.2.Electrolysis of MgO using liquid tin cathode

After the decomposition voltage of MgO was measured using CV measurements,the electrolysis of MgO was carried out.The MgO was weighed and added in the MgF2-LiF mixture,equivalent to 5 mass% of the electrolyte.Prior to all electrolysis experiments,pre-electrolysis was conducted to eliminate residual impurities in the molten salt at 1083K.A constant current of 0.5 A was applied for 4h between the C anode and nickel(Ni)cathode using the potentiostat.After the pre-electrolysis was finished the electrodes were removed from the molten salt and the reactor was allowed to cool to room temperature.

Fig.3.Experimental apparatus for cyclic voltammetry:(a)schematic diagram,(b)photographs of electrodes assembled with the top flange and(c)stainlesssteel reactor.

After pre-electrolysis,the electrolysis of MgO was conducted at 1053-1113K using the liquid Sn cathode and C anode.Fig.4 shows the schematic of the experimental apparatus used for the electrolysis of MgO,and the experimental conditions are listed in Table 2.The liquid Sn cathode was prepared by holding Sn metal in an alumina(Al2O3)crucible,which was assembled with a C rod shielded by Al2O3tube.The gap between the C rod and the Al2O3tube was fille using an Al2O3-based paste.Afterward,the Al2O3crucible was placed at the bottom of the C crucible,as shown in Fig.4(a)and(c).For the electrolysis of MgO at 1053-1113K,2.5V was applied for 7.7-28.2 ks using the potentiostat.After the electrolysis,the reactor was gradually cooled down to room temperature in the electric furnace,and the Mg-Sn alloys produced were separated from the Al2O3crucible.The salt on the surface of the Mg-Sn alloys was completely removed using abrasive paper.

2.3.Vacuum distillation

In order to demonstrate the separation of Mg metal from the Mg-Sn alloy obtained through the electrolysis of MgO,vacuum distillation of the Mg-Sn alloy prepared from the melting of Mg and Sn was conducted.To prepare the Mg-Sn alloy,a mixture of 34 mass% of Mg and 66 mass% of Sn was charged in a C crucible,and it was melted under vacuum at 1013K for 15h,using an electric furnace.The melting was conducted to use the sufficien amount of Mg-Sn alloy feed for the vacuum distillation.

Fig.5 shows the schematic and photographs of the vertical type of vacuum distillation reactor used.The Mg-Sn alloy was placed at the bottom of the reactor and the open end of the reactor was plugged using a silicone stopper and evacuated during the experiments using a rotary pump(Model no.:GLD-201B,ULVAC KIKO,Inc.).The steel reactor was positioned in the electric furnace preheated to 1200-1300K for a duration of 5-10h.After the completion of the distillation,the reactor was immediately removed from the furnace and allowed to cool down to room temperature.The reactor was cut,and the samples were collected.

Fig.4.(a)Schematic of the experimental apparatus for electrolysis of MgO,(b)appearance of the Sn metal used for cathode,and(c)Sn metal cathode.

2.4.Characterization

The microstructure and elements distribution of the Mg-Sn alloys were characterized using a fiel emission scanning electron microscope(FE-SEM:JSM-7000F,JEOL)coupled with an energy dispersive X-ray analyzer(EDS:INCA,Oxford Instruments)after the samples were mechanically polished.The crystalline phases of the Mg-Sn alloys were analyzed using X-ray diffraction(XRD:SmartLab,Rigaku,Cu-Kαradiation).Additionally,the concentration of elements in the samples was determined using an inductively coupled plasma optical emission spectroscopy(ICP-OES:Optima 5300DV,Perkin Elmer)or glow discharge mass spectroscopy(GD-MS:GD90RF,MSI).The crystal orientation and structure of the produced Mg obtained after vacuum distillation process were distinguished by using electron backscatter diffraction(EBSD:OIM analysis,EDAX)and transmission electron microscopy(TEM:Talos F200X,FEI)with EDS(Super-X EDS,Bruker).

3.Results and discussion

3.1.Cyclic voltammetry

Fig.6 shows the result of the CV measurement of the MgF2-LiF molten salt before pre-electrolysis and MgF2-LiF molten salt after pre-electrolysis,and the addition of MgO in MgF2-LiF molten salt at 1083K.The potential in the results of the CV measurement was not corrected for the ohmic drop.Before pre-electrolysis,a large cathodic current was observed at-1.68V(vsPt quasi-reference electrode),which corresponds to the reduction of Mg2+to Mg in the molten salt in Eq.(1).In addition,the large anodic current was observed at 3.0V(vsPt quasi-reference electrode),which corresponds to the generation of fluorin(F2)gas from the oxidation of F?,in Eq.(2).Then,small cathodic and anodic currents were observed at-1.08V and 0.21V(vsPt quasireference electrode),respectively.These results indicated that cations and anions of the impurities contained in the MgF2-LiF molten salt were reduced and oxidized,respectively.

Fig.5.Experimental apparatus for vacuum distillation;(a)schematic diagram and(b)photograph of reactor.

Fig.6(b)shows the result of the CV measurement of the MgF2-LiF molten salt after pre-electrolysis.There is no additional current except the reduction of Mg2+to Mg at-1.67V(vs.Pt quasi-reference electrode)and oxidation of F?to F2gas at 3.04V(vs.Pt quasi-reference electrode).These results indicated that the estimated decomposition voltage of MgF2is 4.71V at 1083K.

After the addition of MgO,the large cathodic current at-1.67V(vs.Pt quasi-reference electrode)was observed and two anodic currents were observed at 0.12V and 2.99V(vs.Pt quasi-reference electrode),as shown in Fig.6(c).The large anodic current corresponds to the oxidation of F?to F2gas at 2.99V(vs.Pt quasi-reference electrode).In addition,a small anodic current was observed at 0.12V(vs.Pt quasi-reference electrode),which corresponds to the generation of CO2gas through the reaction of O2gas from the oxidation of O2?with the C electrode,in Eq.(3).Therefore,the estimated decomposition voltages of MgO under C and MgF2were 1.79V and 4.66V,respectively,at 1083K.However,the decomposition voltage of MgO under C was larger than its theoretical decomposition voltage of approximately 0.3V,as shown in Table 3[23].It is expected that a large overvoltage for the decomposition of MgO existed owing to the low concentration of O2?which was caused by the low solubility of MgO in the MgF2-LiF molten salt at 1083K[24,25].

Table 4The results of electrolysis of MgO and analytical results of the Mg-Sn alloys obtained after electrolysis.

Fig.6.The results of CV measurement of the(a)MgF2-LiF molten salt before the pre-electrolysis,(b)MgF2-LiF molten salt after the pre-electrolysis,and(c)the addition of MgO in MgF2-LiF molten salt at 1083K.

Table 3Theoretical decomposition voltages of several fluoride and MgO at 1083K[23].

Fig.7.Binary phase diagram of Mg-Sn system and isobaric vapor pressure of Mg as a function of temperature and concentration of Mg.

3.2.Electrolysis of MgO using liquid tin cathode

Table 4 shows the results of the electrolysis of MgO using a liquid Sn cathode and the analytical results of Mg-Sn alloys obtained.When the electrolysis of MgO was conducted at 1053K,the current efficien y was maintained at 82.1-86.6 % while the Mg concentration in the Mg-Sn alloy increased to 18.1 mass%.Meanwhile,although the electrolysis temperature increased to 1083 and 1113K,the current effi ciency remained 82.9-84.8 % until the concentration of Mg in the Mg-Sn alloy reached 12.6 and 13.0 mass%.However,when the Mg concentration in the Mg-Sn alloy reached 15.8 and 15.2 mass%,the current efficien y decreased to 74.7 and 71.3 %,respectively,as shown in Table 4.

These results could be explained by the vapor pressure of Mg(pMg)in the Mg-Sn alloy.Fig.7 shows the binary phase diagram of the Mg-Sn system,with the isobaric line of thepMgas a function of the temperature and the concentration of Mg[26].As shown in Fig.7,thepMgincreased with increasing temperature or concentration of Mg in the Mg-Sn alloy.Generally,it is known that when thepMgis larger than 0.01 atm,the Mg metal will evaporate during the electrolysis[23,27].As a result,when thepMgis considered,the maximum concentrations of Mg in the Mg-Sn alloy are 29.8,26.7,and 22.6 mass%of the Mg-Sn alloy at 1053,1083,and 1113K,respectively.Therefore,when the concentration of Mg in the Mg-Sn alloy reached 15.2-15.8 mass% at 1083-1113K,Mg in the Mg-Sn alloy is expected to have evaporated while the evaporation of Mg at 1053K is limited until the concentration of Mg in Mg-Sn alloy is 18.1 mass%.For this reason,when the electrolysis was conducted at 1053K,current efficien y was maintained until 18.1 mass% Mg-Sn alloy was produced while the current efficien y was decreased 71.3-74.7 % when 15.2-15.8 mass% Mg-Sn alloys were produced at 1083-1113K.Consequently,when the results of the electrolysis of MgO andpMgwere taken into consideration,the electrolysis temperature of 1053K is preferred.

As shown in Table 4,when the electrolysis of MgO was conducted in MgF2-LiF molten salt at 1053-1113K,the current efficien y was 71.3-86.6 % and was not close to 100 %.The evaporation of Mg from the Mg-Sn alloy even though the experiments were conducted at 1053K,the electrode position of the impurities during the electrolysis of MgO,and reaction between the Mg-Sn alloy and Al2O3crucible could be the reasons.

Table 4 also shows the concentration of impurities in the Mg-Sn alloys obtained after electrolysis.Aluminum(Al)is the main impurity for Mg-Sn alloys.It is expected that the Al originated from the Al2O3crucible used for holding the liquid Sn cathode due to the reaction of the Mg in the Mg-Sn alloy with the Al2O3crucible.However,it should be noted that the concentration of Al in the Mg-Sn alloy is less than 0.51 mass%,as shown in Table 4.These results indicate that the effect of Mg in the Mg alloys on the reduction of Al2O3crucible was not large owing to the low activity of Mg.In addition,it was expected that the reduction of Al2O3was suppressed by the MgxAlOylayer formed from the reaction of Al2O3and Mg at the surface of the Al2O3crucible.

Fig.8 shows the results of the XRD analysis of the Mg-Sn alloys obtained after electrolysis of MgO using a liquid Sn cathode and C anode at 1053-1113K for 7.7-28.2 ks.The XRD patterns of all of the Mg-Sn alloys obtained reveal the presence of two sets of patterns.The major diffraction patterns can be well indexed to Mg2Sn,and the other set of patterns with lower intensities results from Sn(Mg),as expected from the Mg-Sn phase diagram when the concentration of Mg is 8.3-18.1 mass%,as shown in Fig.7[26].

Fig.9(a),(d),and(g)show the appearance of the Mg-Sn alloys obtained after electrolysis of MgO at 1053,1083,and 1113K using a Sn cathode,respectively.A lump of the Mg-Sn alloys was obtained after electrolysis of MgO.Fig.9(b),(e),and(h)show the microstructure of the cross-section of the Mg-Sn alloys obtained after electrolysis.The microstructure of the Mg-Sn alloy is a mixture of Sn-rich and Mg-rich phases,as shown in Fig.Fig.9(c),(f),(i),and(j).The concentrations of Mg in the Sn-rich phases are 0.8,1.6,and 2.1 mass% and the concentrations of Mg in the Mg-rich phases are 27.2,25.9,and 28.4 mass% at 1053,1083,and 1113K,respectively.This segregation is probably due to the slow cooling of the Mg-Sn alloy in the electric furnace to form Mg2Sn phases and the low concentration of Mg in Sn phases,as shown in Fig.7.

Fig.8.The result of XRD analysis of the Mg-Sn alloys obtained after electrolysis at(a)1053K for 8.8 ks;(b)1053K for 28.2 ks;(c)1083K for 8.7 ks;(d)1083K for 21.7 ks;(e)1113K for 7.7 ks;(f)1113K for 18.1 ks,respectively.

3.3.Vacuum distillation

In order to demonstrate the feasibility of the production of high-purity Mg metal from the Mg-Sn alloys,vacuum distillation of the Mg-Sn alloys was conducted.Table 5 shows the experimental conditions and analytical results of Mg metal obtained at the low-temperature part and the residues obtained at the bottom of the reactor after vacuum distillation.

Vacuum distillation of the Mg-Sn alloy was conducted at 1200-1300K for 5-10h.Fig.10 shows the temperature gradient of the reactor at 1200K and photographs of the Mg metal and residues obtained after vacuum distillation.The Mg metal obtained consists of a single crystal having some twin boundaries generated during the mechanical polishing due to the low stacking fault energy of pure Mg metal[28],as shown in Fig.11(a).In addition,the lattice parameter and the result of EDS analysis of the produced Mg metal obtained indicated that the Mg metal obtained is pure Mg metal,as shown in Fig.11(b),(c),and(d).As shown in Fig.11 and Table 5,Mg metal obtained at the low-temperature part of the reactor had a single crystal structure with a purity of 99.998-99.999%.In addition,the concentration of Mg in the Mg-Sn alloy feed decreased from 34.1 to 0.17 mass%.As mentioned,when thepMgis larger than 0.01 atm,the Mg metal produced will evaporate.However,when the pressure of the system is lower than 1 atm,the metal begins to evaporate at vapor pressures lower than 0.01 atm[23,27].Therefore,as shown in Fig.7,although thepMgis in the range of 0.001-0.0001 atm at 1200-1300K,almost all Mg in the Mg-Sn alloy evaporated during the vacuum distillation at 1200-1300K,as shown in Table 5.As a result,when the purity of Mg metal,energy-efficien y,and the concentration of Mg in residues obtained after the vacuum distillation were taken into consideration,the vacuum distillation conditions of 1200K for 10h is preferred.

Fig.9.The photograph and results of SEM and EDS analysis of the Mg-Sn alloys obtained after electrolysis at different temperatures(a,b,c)1053K for 28.2 ks,(d,e,f)1083K for 21.7 ks,(g,h,i)1113K for 18.1 ks,and(j)results of EDS analysis of points 1-6.

Table 5Experimental conditions and analytical results of Mg metal obtained at the low-temperature part and the residues obtained at the bottom of the reactor after vacuum distillation.

Fig.10.The temperature gradient of the reactor and photographs of Mg metals and the residues obtained after the vacuum distillation of Mg-Sn alloys at 1200K for 10h.

4.Conclusions

To develop an efficien and scalable Mg production process for producing high-purity Mg metal from MgO feedstock,a novel electrolytic method using a liquid Sn cathode and 5 mass% MgO in MgF2-LiF molten salt was investigated.The estimated decomposition voltage of MgO under C anode was 1.79V at 1083K by the results of CV measurements.The electrolysis of MgO was conducted using a Sn cathode and C anode by applying 2.5V at 1053-1113K.The electrolysis results showed that the current efficiencie were 82.1-86.6 % at 1053K and 81.6-84.8 % at 1083-1113K until the production of 9.0-18.1 mass% Mg-Sn and 8.3-13.0 mass% Mg-Sn alloys,respectively.However,the current efficien y decreased to 71.3-74.7 % at 1083-1113K when the concentration of Mg increased to 15.2-15.8 mass% owing to the evaporation of Mg by the increase ofpMg.After electrolysis at 1053-1113K,Mg-Sn alloys with Mg2Sn and Sn(Mg)phases were obtained.In addition,after vacuum distillation of the Mg-Sn alloy feed prepared in advance at 1200K for 10h,the concentration of Mg decreased from 34.1 to 1.57 mass% and Mg metal with a purity of 99.999 % was obtained.

Fig.11.(a)EBSD inverse pole figur map,(b)bright-fiel TEM image,(c)SAED patterns,and(d)results of EDS analysis of the produced Mg obtained after vacuum distillation.

Acknowledgments

The authors are grateful to Dr.DongEung Kim in Korea Institute of Industrial Technology for the discussions throughout this study.In addition,the authors thank Ms.Gyeonghye Moon,Dr.Jae-Yeol Yang,and Dr.Jae-Sik Yoon for their technical support.Furthermore,the authors are grateful to all the members of the Geoanalysis Department of KIGAM for their technical assistance.This research was supported by the National Research Council of Science and Technology(NST)grant by the Korea government(MSIT)(No.CRC-15-06-KIGAM).