Preparation method of high purity and densified tungsten-titanium metal

Abstract

A preparation method of high purity and densified tungsten-titanium metal which mixes titanium metal powder and tungsten metal powder together; adds metallic nitrates (such as nickel nitrate) as combustion improvers; then taking into the account of the characteristics of metal nitrate, which is soluble in alcohols to form a liquidous precursor, adds metal powder to mix together thoroughly, so that the sintering agent is expected to be colloid and uniformly spread among the tungsten-titanium metal powder. The preparation method significantly reduces the ratio of the combustion improver during the preparation of the high purity and densified tungsten-titanium target material.

Claims

1. A preparation method of high purity and densified tungsten-titanium metal which includes the following steps of: (1) mixing a tungsten-titanium metal powder with a nickel nitrate and/or iron nitrate powder to form a powder mixture; (2) mixing the powder mixture with a solvent to form a powder mixture slurry; (3) applying a ball mill process to the powder mixture slurry to produce a uniform slurry mixture; (4) baking, heating and screening the uniform slurry mixture to form a uniform powder mixture; (5) pressing the uniform powder mixture into a circular molded body which is sintered by a high-temperature heat treatment to form a tungsten-titanium metal target, where the tungsten-titanium metal target is made of tungsten-titanium metal with a relative density >99% and a purity level of >99%, and wherein the nickel nitrate and/or iron nitrate accounts for 0.4% in volume of the powder mixture.

2. The preparation method of high purity and densified tungsten-titanium metal as claimed in claim 1, wherein the solvent is an organic solvent.

3. The preparation method of high purity and densified tungsten-titanium metal as claimed in claim 2, wherein the solvent is ethanol.

4. The preparation method of high purity and densified tungsten-titanium metal as claimed in claim 1, wherein a heating temperature in Step 4 is at least 200 C. or higher.

5. The preparation method of high purity and densified tungsten-titanium metal as claimed in claim 1, wherein a sintering temperature of the high-temperature heat treatment in Step 5 is at least 1200 C. or higher.

6. The preparation method of high purity and densified tungsten-titanium metal as claimed in claim 1, wherein a screen used in the screening in Step 4 is a 320-mesh screen.

7. The preparation method of high purity and densified tungsten-titanium metal as claimed in claim 1, wherein the tungsten-titanium metal target is made of tungsten-titanium metal with a grain size of 1 to 3 micrometers, nickel content not greater than 230 ppm, and carbon content not greater than 40 ppm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is the step-by-step schematic diagram of the preparation method of high purity and densified tungsten-titanium metal of the present invention;

(2) FIG. 2 is an enlarged diagram of the tungsten-titanium metal target of an embodiment of the preparation method of high purity and densified tungsten-titanium metal of the present invention; and

(3) FIG. 3 is a correlation diagram of impact of nickel nitrate on tungsten-titanium metal by volume of nickel nitrate added.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) The technical characteristics of the present invention is explained further by the detailed description given herein below by way of embodiments so that the technical characteristics, advantages, and the effect of the present invention become more fully understood to those skilled in the art to which the present invention described in the patent specification.

(5) Please refer to FIG. 1. As illustrated in FIG. 1, FIG. 1 is the step-by-step schematic diagram of the preparation method of high purity and densified tungsten-titanium metal of the present invention which includes the following steps: Step(1) S110: Mix tungsten-titanium metal powder with one type of metallic nitrates powder to form a powder mixture; Step(2) S120: Mix the powder mixture with a solvent to form powder mixture slurry; Step(3) S130 Apply the ball mill process to the powder mixture slurry to produce a uniform slurry mixture; Step(4) S140: Bake, heat and screen the uniform slurry mixture to form a uniform powder mixture; Step(5) S150: Press the uniform powder mixture into a circular molded body which is sintered by high-temperature heat treatment to form a tungsten-titanium metal target,

(6) wherein the metallic nitrate powder in Step(1) S110 can account for less than 2% in volume of the powder mixture, preferably, the metallic nitrate powder to account for 0.4% in volume of the powder mixture; the materials of metallic nitrate powder can be nickel nitrate, iron nitrate, or copper nitrate; the solvent in Step(2) S120 can be an organic solvent, preferably, ethanol to be the solvent; the heating temperature in Step(4) S140 can be at least 200 C. or higher and the screen used in the screening process can be a 320-mesh screen (hole diameter of 4.875 micrometers); the sintering temperature of high-temperature heat treatment in Step(5) S150 can be at least 1200 C. or higher.

(7) The present invention takes into the account of the characteristics of metal nitrate, which helps capillary action and dissolution mechanism to take place and improves the condition that tungsten-titanium metal powder in liquid phase and solid phase is difficult to mix uniformly, in order to obtain a high purity and densified tungsten-titanium metal target. The tungsten-titanium metal target is made of tungsten-titanium metal with a relative density >99%, a purity level of >99%, a grain size of 1 to 3 micrometers, nickel content not greater than 230 ppm, and carbon content not greater than 40 ppm.

(8) Please refer to FIG. 2. FIG. 2 is an enlarged diagram of the tungsten-titanium metal target of an embodiment of the preparation method of high purity and densified tungsten-titanium metal of the present invention. Nickel nitrate is used as one of the metallic nitrate powder in the embodiment. As shown in the diagram, tungsten-titanium metal can have better relative density by adding nickel nitrate. Please refer to FIG. 3. FIG. 3 is a correlation diagram of impact of nickel nitrate on tungsten-titanium metal by volume of nickel nitrate added. The vertical axis is the relative density of tungsten-titanium metal; the horizontal axis shows the percentage of the metallic nitrate powder in volume accounting for the powder mixture. The metallic nitrate powder used in the embodiment is nickel nitrate, as shown in the diagram. When the volume of nickel nitrate added to the powder mixture increases to 0.4 vol %, the relative density of the tungsten-titanium metal target increases from 72% to higher than 99%. After the sintering process of a high-temperature heat treatment (at a temperature of about 1400 C.), the purity of tungsten-titanium metal target is listed in the table below:

(9) TABLE-US-00001 Element W Ti Ni C Concentration wt % wt % ppm ppm WTi target 90.3 9.95 230 40,
and the enlarged diagram of the tungsten-titanium metal target is shown in FIG. 2. Nickel nitrate is used as one of the metallic nitrate powder in the embodiment. However, the present invention is not limited to this material only. Both nickel nitrate and iron nitrate can achieve the aforementioned effect of the embodiment. When metallic nitrate powder is used as a combustion improver, adding a small amount of nickel nitrate or iron nitrate can achieve the effect of lowering the melting point partially and will not form a proeutectic phase, whereas the effect produced by using copper nitrate is lesser.

(10) Please refer to Step(3) of the preparation method of high purity and densified tungsten-titanium metal of the present invention, wherein the ball mill process can be categorized into dry type and wet type. The dry type ball milling uses a method of smashing and grinding directly; add a proper ratio of grinding beads and powder and apply the centrifugal force to rotate and shake the ball milling container; powder undergoes the process of cold welding, shaping, and cracking repeatedly as the result from bombardment among grinding beads, and the effect of refining powder can be achieved, whereas the wet type ball milling treats the powder of solid phase, which is to be processed, as a solute to be added into a suitable solvent at a proper ratio to produce a suspension liquid; apply force of collision and cutting repeatedly by the motion of mixing and smashing to crack and break apart powder in the solvent, so that the powder is uniformly micronized.

(11) Please refer to Step(5) of the preparation method of high purity and densified tungsten-titanium metal of the present invention, wherein sintering is a process to make metal particles to form a solid mass of material by controlling the process temperature. During the sintering process, the boundary of particles is formed first, resulting in the recrystallization of particles; the high temperature increases the surface formability of metal and establishes a layer of mesh structure of liquid that can improve the nature of mutual mechanical locking and can eliminate all gas dissolved in metal at such a high temperature; the duration of sintering process is about 20 to 40 minutes; during the sintering process, in order to prevent metallic powder from being in contact with atmosphere and becoming oxidized, nitrogen or reducing gas is used to prevent metallic powder from forming an oxidized layer under extreme heat.

(12) The present invention illustrates a method to mix titanium metal powder and tungsten metal powder together; add metallic nitrates (nickel nitrate, iron nitrate, or copper nitrate) as combustion improvers; then taking into the account of the characteristics of metal nitrate, which is soluble in alcohols to form a liquidous precursor, add metal powder to mix together thoroughly, so that the sintering agent is expected to be colloid and uniformly spread among the tungsten-titanium metal powder; the preparation method significantly reduces the ratio of the combustion improver during the preparation of the high purity and densified tungsten-titanium target material thus to improve the thin film quality.

(13) The aforementioned embodiments are chosen and described in order to explain the technological concepts and characteristics of the present invention and are not intended to limit the scope of the present invention in any way. Individuals skilled in the art to can, without departing from the spirit and scope of the present invention, utilize the invention for various modifications as suitable for specific applications. Therefore, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.