Title of Invention	PREPARATION OF TITANIUM CARBONITRIDE IN EXTENDED ARC THERMAL PLASMA
Abstract	The present invention provides a process for the preparation of titanium carbonitride in extended arc thermal plasma. The methods comprises the steps of preparing a homogenous mixture of oxide of titanium and carbonaceous material and introducing the mixture to plasma hearth; striking the plasma arc between the first electrode, preferably the cathode and the second electrode, preferably the anode; introducing the plasma forming gas containing nitrogen such as ammonia or nitrogen through the axial hole of the first electrode, the cathode into the space between the first and second electrode, preferably the anode; extending/expanding the plasma arc by the movement of electrodes; reacting the charge mixture over a period of time in extended/expanded arc plasma.

Title of Invention

PREPARATION OF TITANIUM CARBONITRIDE IN EXTENDED ARC THERMAL PLASMA

Abstract

The present invention provides a process for the preparation of titanium carbonitride in extended arc thermal plasma. The methods comprises the steps of preparing a homogenous mixture of oxide of titanium and carbonaceous material and introducing the mixture to plasma hearth; striking the plasma arc between the first electrode, preferably the cathode and the second electrode, preferably the anode; introducing the plasma forming gas containing nitrogen such as ammonia or nitrogen through the axial hole of the first electrode, the cathode into the space between the first and second electrode, preferably the anode; extending/expanding the plasma arc by the movement of electrodes; reacting the charge mixture over a period of time in extended/expanded arc plasma.

Full Text	Field of invention The present invention relates to a method for preparation of titanium carbonitride (TiCN) in thermal plasma. More particularly, the present invention relates to a process for preparation of titanium carbonitride in extended/expanded arc plasma. Background and prior art of the invention The carbide and nitride of titanium are of practical interest because of their high hardness and excellent wear properties. The solid solution of these i.e. titanium carbonitride has been used in cutting tools, wear resistant materials, electrical resistors and abrasive for polishing. Titanium carbonitride based cermets have been successfully introduced in metal cutting industries compared to conventional hard metals at high cutting speeds, particularly in finishing and milling operations [A. Bellosi, R. Calzavarini, M.G. Faga, F. Monteverde, C. Zancol6, G.E. D'Errico, Journal of Materials Processing Technology 143-144 (2003) 527-532; P. Ettmayer, H. Kolaska.'f W. Lengauer & K. Dreyert, Int. J. of Refractory metals & Hard Materials 13 (1995) 343-35 1; A. Jha and S. J. Yoon; Journal of Materials Science 34 (1999) 307- 322]. Furthermore, titanium carbonitride exhibits enhanced thermal resistance and toughness and consequently, the use thereof is expanding steadily in the fields of, for example, sintered hard metals and heat resisting alloys. Conventional ways of preparation of titanium carbonitride (TiCN) are by reaction of the elemental/oxides/halides of titanium with carbon and nitrogen containing materials at high temperatures [C.F. Davidson et at. US patent No. 4,812,301, Mar. 14, 1989; S. D. Dunmead et al. US patent No. 5,756,410 May 26,1998; B. Kim et al. US patent No. 2004/0161379 Aug. 19, 2004; C.L. Yeh and Y.D. Chen, Ceramic International (2005) (article in press)]. The carbonitride can also be produced by reacting a mixture of TiC and TiN. The solid state diffusion of C, N or both into elemental or oxide powders at high temperatures where the reaction takes place over several hours to produce the desired product. The reactions are usually carried out in electrical resistance heated furnace [H. Zeiringer, US Patent No. 5,147,831 Sept. 15, 1992; A. Jha and S. J. Yoon; Journal of Materials Science 34 (1999) 307-322]. The titanium based halides when treated with carbon and nitrogen containing gases generate corrosive gases. The elemental powders and halides are expensive raw materials compared to the oxides of titanium. Thermal plasma has been used successfully for preparation of TiCN [P.C. Kong and E. Pfender, Plasma Processes, in Carbide, Nitride and Boride Materials synthesis and Processing (Ed. A.W. Weimer) Chapman and Hall, London, 1997, pp. 359-387]. Thermal plasma with high temperature and ionic species can reduce the reaction time considerably. However, DC and RF torch type plasma reactors used for this purpose are very expensive. Objects of the invention The present invention provides a process for the preparation of titanium carbonitride (TiCN), which obviates the drawbacks of the hitherto known prior art as detailed above. Another objective of the invention is to provide a process for the preparation of titanium carbonitride (TiCN) in a relatively inexpensive extended/expanded arc thermal plasma reactor. Summary of the invention Accordingly the present invention provide a process for the preparation of titanium carbonitride (TiCN) in thermal plasma; comprising the steps of: a) preparing a mixture of oxide of titanium and carbonaceous material, and introducing it to a hearth of reactor having two electrodes, the first electrode, preferably a cathode and the second one preferably an anode, b) injecting the plasma forming gas to the above said reactants in step (a) through the axial hole of the first electrode into the space between the first and second electrode, c) striking the plasma arc in between the above said two electrodes followed by extending or expanding the plasma arc in the hearth by the movement of the two electrodes, d) carrying out the above said reaction, at a temperature of 1500- 1800°C, at a current of 30-40A, at a load voltage of 45-65V, for a time period of 10-25 minutes to obtain the desired product. In an embodiment of the present invention the reactor used is graphite crucible. In an embodiment of the present invention the nitrogen-containing plasma forming gas used is selected from a mixture of argon and ammonia, and argon and nitrogen. In yet another embodiment the ratio of argon to nitrogen containing gas is in the range of 1:6 to 1:8 In yet another embodiment the ratio of oxide of titanium to active carbon used is in the range of 2:1 to 2:1.5. In yet another embodiment the current used is in the range of 300-350A. In yet another embodiment the loaded voltage used is in the range of 50-60V. In yet another embodiment the time period used is in the range of 15-20 minutes. Detailed description of the invention The present invention provides a process for producing titanium carbonitride (TiCN) which comprises reacting a mixture of oxide of titanium and a carbonaceous material in nitrogen or ammonia plasma in extended/expanded arc plasma reactor. The present invention is illustrated in figure 1 of the drawing. Figure 1 represents a schematic of the plasma hearth, in accordance with the present invention for preparation of titanium carbonitride (TiCN). Two graphite electrodes [1, 7] are arranged in the vertical configuration in the pot type extended/expanded arc plasma reactor. The graphite crucible [5] is used as the hearth of the reactor and is connected to the bottom graphite electrode [7]. The crucible assembly constitutes the anode. The top graphite electrode [1], the cathode is having an axial hole to pass the plasma forming gas. The bottom electrode [1] and the crucible [5] is kept fixed and the formation and stabilization of the extended arc plasma is done by the movement of the top electrode [1], which is actuated by a rack and pinion mechanism. Initially both the electrodes were kept in contact with each other, and then the crucible was partially filled with the charge [3]. The charge is essentially an intimate mixture of oxide of titanium and a carbonaceous material. A graphite lid [2] with a central hole is kept as a cover on the graphite crucible. The plasma forming gas, a mixture of argon and a nitrogen containing gas such as nitrogen and ammonia, was injected to the reactants present in the graphite crucible[5] through the axial hole of the top electrode. Plasma forming gas and water for cooling of the electrodes were regulated. As soon as the power to the reactor was switched on, the top electrode was slowly pulled up after striking the arc to form extended/expanded arc plasma in the hearth. The arc current and voltage were regulated during the course of the experiment. Experiments were carried out in the temperature range of 1500 °C - 1800 °C. The plasma forming gas and the graphite lid [2] on the top of the graphite hearth [5] helps in maintaining desired atmosphere inside the hearth for preparation of titanium carbonitride (TiCN). The following examples are given by the way of illustration of the working of the invention in actual practice and therefore should not be read or construed to limit the scope of the invention. EXAMPLE -1 TiO2 powder (minimum assay 99.0%) and activated charcoal was mixed thoroughly with 5 % PVA solution, peletised and oven dried. The dried pellets were then charged in the plasma. Initially both the electrodes were kept in contact with each other, and then the hearth was partially filled with the pellets. A graphite lid with a central hole was kept as a cover on the graphite crucible. The Plasma forming gas, a mixture of argon and ammonia was introduced through the axial hole of the top electrode. As soon as the power to the reactor was switched on, the top electrode was slowly pulled up after striking the arc to form extended/expanded arc plasma in the hearth. The arc current and voltage were regulated during the course of the experiment. The experimental conditions are as follows: Titanium dioxide - 80 g Active carbon - 40 g Argon -1 Ipm Ammonia - 6 Ipm Arc Current - 300 A Load voltage - 50 V Time - 20 min The product was found to be titanium carbonitride (TiCN) from the XRD analysis. No peak for titanium dioxide or sub-oxides was observed, suggesting complete conversion of TiO2 to TiCN. EXAMPLE -2 A homogenous mixture of TiO2 and activated carbon was taken as charge and the experiment was carried out as described in Example - 1. Charge composition was same as Example - 1, but the power condition was varied by changing arc current from 300 A to 350 A. Duration of the experiment was changed from 20 minutes to 15 minutes. The experimental conditions are as follows Titanium dioxide - 80 g Active carbon - 40 g Argon -1 Ipm Ammonia - 6 Ipm Arc Current - 350 A Load voltage - 50 V Time -15min The XRD analysis confirmed the product to be carbonitride (TiCN). The presence of f titanium dioxide or sub-oxides was not observed. EXAMPLE -3 A homogenous mixture of TiO2 and activated carbon was taken as charge and the experiment was carried out as described in Example-1. Quantity of charge was varied from 80 g of TiOa to 100 g TiO2 and active carbon from 40 g to 50 g. The experimental conditions are as follows Titanium dioxide -100 g Active carbon - 50 g Argon -1 Ipm Ammonia - 8 Ipm Arc Current - 300 A Load voltage - 60 V Time - 20 min The product was found to be titanium carbide (TiCN) from the XRD analysis. Here again, TiO2 and tiatanium sub-oxides peaks were not observed in the XRD pattern. EXAMPLE -4 A homogenous mixture of TiO2 and activated carbon was taken as charge and the experiment was carried out as described in Example-1. However, a mixture argon and nitrogen was taken as plasma forming gas and nitriding gas. The experimental conditions are as follows Titanium dioxide - 80 g Active carbon - 45 g Argon -1 Ipm Nitrogen - 6 Ipm Arc Current - 300 A Load voltage - 55 V Time -15min The XRD analysis reveals the product to be titanium nitride (TiCN) without any peak of TiO2 and tiatanium sub-oxides. Advantages: The main advantages of the present inventions are 1. The process uses relatively low cost extended/expanded arc thermal plasma formed by arcing between graphite electrodes compared to the expensive DC torches and RF thermal plasma. 2. The reaction time is greatly reduced (several hours in case of conventional resistance heated furnace to few minutes in the present case) when a mixture of oxide of titanium and a carbon containing material is treated in plasma. We claim 1) A process for the preparation of titanium carbonitride (TiCN) in thermal plasma; the said process comprising the steps of: a) preparing a mixture of oxide of titanium and carbonaceous material, and introducing it to a hearth of reactor having two electrodes, the first electrode, preferably a cathode and the second one preferably an anode, b) injecting the plasma forming gas to the above said reactants in step (a) through the axial hole of the first electrode into the space between the first and second electrode, c) striking the plasma arc in between the above said two electrodes followed by extending or expanding the plasma arc in the hearth by the movement of the two electrodes, d) carrying out the above said reaction, at a temperature of 1500- 1800°C, at a current of 30-40A, at a load voltage of 45-65V, for a time period of 10-25 minutes to obtain the desired product. 2) A process as claimed in claim 1, wherein the reactor used is a graphite crucible. 3) A process as claimed in claim 1, wherein the nitrogen-containing plasma forming gas used is selected from a mixture of argon and ammonia, and argon and nitrogen. 4) A process as claimed in claim 3, wherein the ratio of argon to nitrogen containing gas is in the range of 1:6 to 1:8 5) A process as claimed in claim 1, wherein the ratio of titanium dioxide to active carbon used is in the range of 2:1 to 2:1.5. 6) A process as claimed in claim 1, wherein the current used is in the range of 300-350A. 7) A process as claimed in claim 1, wherein the loaded voltage used is in the range of 50-60V. 8) A process as claimed in claim 1, wherein the time period used is in the range of 15-20 minutes. 9) A process for the preparation of titanium carbonitride (TCN) in thermal plasma, substantially as herein described with reference to examples and drawings accompanying this specification.

Full Text

Field of invention
The present invention relates to a method for preparation of titanium
carbonitride (TiCN) in thermal plasma. More particularly, the present invention relates to a process for preparation of titanium carbonitride in extended/expanded arc plasma.
Background and prior art of the invention
The carbide and nitride of titanium are of practical interest because of their high hardness and excellent wear properties. The solid solution of these i.e. titanium carbonitride has been used in cutting tools, wear resistant materials, electrical resistors and abrasive for polishing. Titanium carbonitride based cermets have been successfully introduced in metal cutting industries compared to conventional hard metals at high cutting speeds, particularly in finishing and milling operations [A. Bellosi, R. Calzavarini, M.G. Faga, F. Monteverde, C. Zancol6, G.E. D'Errico, Journal of Materials Processing Technology 143-144 (2003) 527-532; P. Ettmayer, H. Kolaska.'f W. Lengauer & K. Dreyert, Int. J. of Refractory metals & Hard Materials 13 (1995) 343-35 1; A. Jha and S. J. Yoon; Journal of Materials Science 34 (1999) 307- 322]. Furthermore, titanium carbonitride exhibits enhanced thermal resistance and toughness and consequently, the use thereof is expanding steadily in the fields of, for example, sintered hard metals and heat resisting alloys.
Conventional ways of preparation of titanium carbonitride (TiCN) are by reaction of the elemental/oxides/halides of titanium with carbon and nitrogen containing materials at high temperatures [C.F. Davidson et at. US patent No. 4,812,301, Mar. 14, 1989; S. D. Dunmead et al. US patent No. 5,756,410 May 26,1998; B. Kim et al. US patent No. 2004/0161379 Aug. 19, 2004; C.L. Yeh and Y.D. Chen, Ceramic International (2005) (article in press)]. The carbonitride can also be produced by reacting a mixture of TiC and TiN. The solid state diffusion of C, N or both into elemental or oxide powders at high temperatures where the reaction takes place over several hours to produce the desired product. The reactions are usually carried out in electrical resistance heated furnace [H.
Zeiringer, US Patent No. 5,147,831 Sept. 15, 1992; A. Jha and S. J. Yoon; Journal of Materials Science 34 (1999) 307-322]. The titanium based halides when treated with carbon and nitrogen containing gases generate corrosive gases. The elemental powders and halides are expensive raw materials compared to the oxides of titanium. Thermal plasma has been used successfully for preparation of TiCN [P.C. Kong and E. Pfender, Plasma Processes, in Carbide, Nitride and Boride Materials synthesis and Processing (Ed. A.W. Weimer) Chapman and Hall, London, 1997, pp. 359-387]. Thermal plasma with high temperature and ionic species can reduce the reaction time considerably. However, DC and RF torch type plasma reactors used for this purpose are very expensive.
Objects of the invention
The present invention provides a process for the preparation of titanium carbonitride (TiCN), which obviates the drawbacks of the hitherto known prior art as detailed above.
Another objective of the invention is to provide a process for the preparation of titanium carbonitride (TiCN) in a relatively inexpensive extended/expanded arc thermal plasma reactor.
Summary of the invention
Accordingly the present invention provide a process for the preparation of titanium carbonitride (TiCN) in thermal plasma; comprising the steps of:
a) preparing a mixture of oxide of titanium and carbonaceous material,
and introducing it to a hearth of reactor having two electrodes, the
first electrode, preferably a cathode and the second one preferably
an anode,
b) injecting the plasma forming gas to the above said reactants in step
(a) through the axial hole of the first electrode into the space
between the first and second electrode,
c) striking the plasma arc in between the above said two electrodes
followed by extending or expanding the plasma arc in the hearth by
the movement of the two electrodes,
d) carrying out the above said reaction, at a temperature of 1500-
1800°C, at a current of 30-40A, at a load voltage of 45-65V, for a
time period of 10-25 minutes to obtain the desired product.
In an embodiment of the present invention the reactor used is graphite crucible.
In an embodiment of the present invention the nitrogen-containing plasma forming gas used is selected from a mixture of argon and ammonia, and argon and nitrogen.
In yet another embodiment the ratio of argon to nitrogen containing gas is in the range of 1:6 to 1:8
In yet another embodiment the ratio of oxide of titanium to active carbon used is in the range of 2:1 to 2:1.5.
In yet another embodiment the current used is in the range of 300-350A.
In yet another embodiment the loaded voltage used is in the range of 50-60V.
In yet another embodiment the time period used is in the range of 15-20 minutes.
Detailed description of the invention
The present invention provides a process for producing titanium carbonitride (TiCN) which comprises reacting a mixture of oxide of titanium and a carbonaceous material in nitrogen or ammonia plasma in extended/expanded arc plasma reactor.
The present invention is illustrated in figure 1 of the drawing.
Figure 1 represents a schematic of the plasma hearth, in accordance with the present invention for preparation of titanium carbonitride (TiCN).
Two graphite electrodes [1, 7] are arranged in the vertical configuration in the pot type extended/expanded arc plasma reactor. The graphite crucible [5] is
used as the hearth of the reactor and is connected to the bottom graphite electrode [7]. The crucible assembly constitutes the anode. The top graphite electrode [1], the cathode is having an axial hole to pass the plasma forming gas. The bottom electrode [1] and the crucible [5] is kept fixed and the formation and stabilization of the extended arc plasma is done by the movement of the top electrode [1], which is actuated by a rack and pinion mechanism.
Initially both the electrodes were kept in contact with each other, and then the crucible was partially filled with the charge [3]. The charge is essentially an intimate mixture of oxide of titanium and a carbonaceous material. A graphite lid [2] with a central hole is kept as a cover on the graphite crucible. The plasma forming gas, a mixture of argon and a nitrogen containing gas such as nitrogen and ammonia, was injected to the reactants present in the graphite crucible[5] through the axial hole of the top electrode. Plasma forming gas and water for cooling of the electrodes were regulated. As soon as the power to the reactor was switched on, the top electrode was slowly pulled up after striking the arc to form extended/expanded arc plasma in the hearth. The arc current and voltage were regulated during the course of the experiment. Experiments were carried out in the temperature range of 1500 °C - 1800 °C. The plasma forming gas and the graphite lid [2] on the top of the graphite hearth [5] helps in maintaining desired atmosphere inside the hearth for preparation of titanium carbonitride (TiCN).
The following examples are given by the way of illustration of the working of the invention in actual practice and therefore should not be read or construed to limit the scope of the invention.
EXAMPLE -1
TiO2 powder (minimum assay 99.0%) and activated charcoal was mixed thoroughly with 5 % PVA solution, peletised and oven dried. The dried pellets were then charged in the plasma. Initially both the electrodes were kept in contact with each other, and then the hearth was partially filled with the pellets. A
graphite lid with a central hole was kept as a cover on the graphite crucible. The Plasma forming gas, a mixture of argon and ammonia was introduced through the axial hole of the top electrode. As soon as the power to the reactor was switched on, the top electrode was slowly pulled up after striking the arc to form extended/expanded arc plasma in the hearth. The arc current and voltage were regulated during the course of the experiment. The experimental conditions are as follows:
Titanium dioxide - 80 g
Active carbon - 40 g
Argon -1 Ipm
Ammonia - 6 Ipm
Arc Current - 300 A
Load voltage - 50 V
Time - 20 min
The product was found to be titanium carbonitride (TiCN) from the XRD analysis. No peak for titanium dioxide or sub-oxides was observed, suggesting complete conversion of TiO2 to TiCN.
EXAMPLE -2
A homogenous mixture of TiO2 and activated carbon was taken as charge and the experiment was carried out as described in Example - 1. Charge composition was same as Example - 1, but the power condition was varied by changing arc current from 300 A to 350 A. Duration of the experiment was changed from 20 minutes to 15 minutes. The experimental conditions are as follows
Titanium dioxide - 80 g
Active carbon - 40 g
Argon -1 Ipm
Ammonia - 6 Ipm
Arc Current - 350 A
Load voltage - 50 V
Time -15min
The XRD analysis confirmed the product to be carbonitride (TiCN). The presence of f titanium dioxide or sub-oxides was not observed.
EXAMPLE -3
A homogenous mixture of TiO2 and activated carbon was taken as charge and the experiment was carried out as described in Example-1. Quantity of charge was varied from 80 g of TiOa to 100 g TiO2 and active carbon from 40 g to 50 g. The experimental conditions are as follows
Titanium dioxide -100 g
Active carbon - 50 g
Argon -1 Ipm
Ammonia - 8 Ipm
Arc Current - 300 A
Load voltage - 60 V
Time - 20 min
The product was found to be titanium carbide (TiCN) from the XRD analysis. Here again, TiO2 and tiatanium sub-oxides peaks were not observed in the XRD pattern.
EXAMPLE -4
A homogenous mixture of TiO2 and activated carbon was taken as charge and the experiment was carried out as described in Example-1. However, a mixture argon and nitrogen was taken as plasma forming gas and nitriding gas. The experimental conditions are as follows
Titanium dioxide - 80 g
Active carbon - 45 g
Argon -1 Ipm
Nitrogen - 6 Ipm
Arc Current - 300 A
Load voltage - 55 V
Time -15min
The XRD analysis reveals the product to be titanium nitride (TiCN) without any peak of TiO2 and tiatanium sub-oxides.
Advantages:
The main advantages of the present inventions are
1. The process uses relatively low cost extended/expanded arc thermal
plasma formed by arcing between graphite electrodes compared to the
expensive DC torches and RF thermal plasma.
2. The reaction time is greatly reduced (several hours in case of conventional
resistance heated furnace to few minutes in the present case) when a
mixture of oxide of titanium and a carbon containing material is treated in
plasma.

We claim
1) A process for the preparation of titanium carbonitride (TiCN) in thermal
plasma; the said process comprising the steps of:
a) preparing a mixture of oxide of titanium and carbonaceous material,
and introducing it to a hearth of reactor having two electrodes, the
first electrode, preferably a cathode and the second one preferably
an anode,
b) injecting the plasma forming gas to the above said reactants in step
(a) through the axial hole of the first electrode into the space
between the first and second electrode,
c) striking the plasma arc in between the above said two electrodes
followed by extending or expanding the plasma arc in the hearth by
the movement of the two electrodes,
d) carrying out the above said reaction, at a temperature of 1500-
1800°C, at a current of 30-40A, at a load voltage of 45-65V, for a
time period of 10-25 minutes to obtain the desired product.

2) A process as claimed in claim 1, wherein the reactor used is a graphite
crucible.
3) A process as claimed in claim 1, wherein the nitrogen-containing plasma
forming gas used is selected from a mixture of argon and ammonia, and
argon and nitrogen.
4) A process as claimed in claim 3, wherein the ratio of argon to nitrogen
containing gas is in the range of 1:6 to 1:8
5) A process as claimed in claim 1, wherein the ratio of titanium dioxide to
active carbon used is in the range of 2:1 to 2:1.5.
6) A process as claimed in claim 1, wherein the current used is in the range
of 300-350A.
7) A process as claimed in claim 1, wherein the loaded voltage used is in the
range of 50-60V.
8) A process as claimed in claim 1, wherein the time period used is in the
range of 15-20 minutes.
9) A process for the preparation of titanium carbonitride (TCN) in thermal plasma, substantially as herein described with reference to examples and drawings accompanying this specification.

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Patent Number

271187

Indian Patent Application Number

763/DEL/2006

PG Journal Number

07/2016

Publication Date

12-Feb-2016

Grant Date

08-Feb-2016

Date of Filing

22-Mar-2006

Name of Patentee

COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH

Applicant Address

ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI - 110 001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	SAROJ KUMR SINGH	REGIONAL RESEARCH LABORATORY BHUBANESWAR-751013.

PCT International Classification Number

C04B 35/56

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA