JPH023201A - permanent magnet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a permanent magnet having magnetic anisotropy due to novel mechanical orientation, particularly R (where R is at least one rare earth element including Y). The present invention relates to a permanent magnet made of 1M (at least one transition metal element) and X (at least one group IIIb element).

[Prior art] Permanent magnets are one of the important electrical and electronic materials used in a wide range of fields, from various household electrical appliances to peripheral terminal equipment for large computers, and are becoming more and more compact in recent years. With the demand for higher efficiency, permanent magnets are also required to have increasingly higher performance.

A permanent magnet is a material that generates a magnetic field without supplying electrical energy from the outside, and a material with a large coercive force and a high residual magnetic flux density is suitable, contrary to a high permeability material.

Typical permanent magnets currently in use are Alnico cast magnets, Ba ferrite magnets, and rare earth-transition metal magnets.

In particular, R-C, which is a rare earth-transition metal magnet.

BACKGROUND ART Permanent magnets and R-Fe-B permanent magnets are permanent magnets with extremely high coercive force and energy product, and have been extensively researched and developed because they provide high magnetic performance.

Conventionally, these rare earth-iron (transition metal)-based high-performance anisotropic permanent magnets include the following.

(1) First, JP-A No. 59-48008 states that ``8 to 30% R in atomic percentage (R is at least one kind of rare earth element including Y), 2 to 28% B, and the balance F.
"Permanent magnet characterized by being a magnetically anisotropic sintered body consisting of e.

Moreover, this permanent magnet is manufactured by sintering based on a powder metallurgy method.

In this sintering method, an alloy ingot is produced by melting and casting, then crushed to obtain magnet powder with an appropriate particle size (several μm), kneaded with a binder as a forming aid, and press-formed in a magnetic field. and form a molded body.

The compact is then sintered in argon at a temperature around 1100° C. for 1 hour and then rapidly cooled to room temperature.

After sintering, by heat-treating at a temperature of around 600℃,
Furthermore, the coercive force is improved to make it a permanent magnet.

(2) Also, in Japanese Patent Application Laid-Open No. 59-211549, “
A permanent magnet formed from and bonded together a fine piece of a melt-spun alloy ribbon with a very fine crystalline magnet powder, said alloy being one selected from the group consisting of neodymium, praseodymium, and mitsch metal. In a permanent magnet that is an alloy containing one or more rare earth elements; a transition metal element, iron; and boron, fine particles are held in the desired magnetic shape by an adhesive distributed therebetween, and that the microspheres are magnetically isotropic and that the magnet moldings can be magnetized in any desired direction in a suitable magnetic field to form a bonded magnet; A bonded rare earth-iron magnet characterized in that it has a grain compaction density of at least 80% and a residual magnetic energy product of at least 9 megagauss Oersteds at saturation magnetization.

This permanent magnet is made using a quenched ribbon manufacturing equipment used to manufacture amorphous alloys to produce quenched thin flakes with a thickness of about 30 μm, and then turn the thin flakes into magnets using a resin bonding method. manufactured by the method.

In this resin bonding method using quenched thin strips using the melt spinning method, first, R
-Making a quenched ribbon of Fe-B alloy The obtained ribbon-like ribbon with a thickness of 30 mm is an aggregate of crystals with a diameter of 1000 Å or less, is brittle and easily broken, and the crystal grains are distributed isotropically. Therefore, it is also magnetically isotropic. If this ribbon is crushed to an appropriate particle size, kneaded with resin, and press-molded, 7 tons will be produced.
At a pressure of on/cd ff, it is possible to fill about 85 bodies v1%.

(3) Furthermore, in Japanese Patent Application Laid-open No. 80-100402,
``■ Amorphous or fine particulate materials consisting of iron, neodymium and/or praseodymium, and boron,
A fully densified, anisotropic permanent magnet in the form of fine 1.1 grains, which is made into a magnet by high-temperature consolidation and hot working.

■A magnet is made by high-temperature die-up setting of a material consisting of iron, neodymium and/or praseodymium, and boron, and the resulting magnet is characterized in that the preferred direction of magnetization is parallel to the direction of upset compression. Fine grained anisotropic permanent magnet.

■Magnets are essentially 50-90% on an atomic percent basis
It is formed by plastically deforming an amorphous or fine-grained alloy consisting of iron, 10-50% neodymium and/or praseodymium, and 1-10% boron at high temperatures, and the preferred direction of magnetization is substantially the same as the above deformation. Permanent magnets characterized in that they are perpendicular to the direction of material flow between them.

These magnets are made by processing the ribbon-like quenched ribbon or flake in (2) above into a dense and anisotropic R-Fe-B magnet using a method called a two-step hot pressing method in a vacuum or an inert atmosphere. It's something you get.

In this pressing process, uniaxial pressure is applied, the axis of easy magnetization is oriented parallel to the pressing direction, and the alloy becomes anisotropic.

In addition, the crystal grains of the ribbon-like thin strip produced by the initial melt spinning method are made smaller than the grain size at which they exhibit the maximum coercive force, to avoid coarsening of the crystal grains during the subsequent hot pressing. Allow the particles to grow to the optimum particle size.

(4) Finally, in Japanese Patent Application Laid-open No. 62-276803,
rR (where R is at least one rare earth element including Y) 8 at% to 30 at%, B2 at% to 28 at%
, by melting and casting an alloy consisting of 50 atomic % or less of Co, 15 atomic % or less of A, and the balance being iron and other impurities unavoidable in manufacturing, and then hot working the cast ingot at a temperature of 500 ° C. or higher. A rare earth-iron permanent magnet is disclosed in which the cast alloy is made magnetically anisotropic by making the crystal grains finer and orienting the crystal axes in a specific direction.

[Problems to be Solved by the Invention] The conventional R-Fe-B permanent magnets described in (1) to (4) above have the following drawbacks.

When manufacturing permanent magnets (1), it is essential to turn the alloy into powder, but since R-Fe-B alloys are highly active against oxygen, turning them into powder will cause more intense oxidation. , the oxygen concentration in the sintered body inevitably becomes high.

Also, when molding the powder, a molding aid, such as zinc stearate, must be used, which is removed beforehand during the sintering process; This carbon remains in the form of carbon, which is undesirable because it significantly reduces the magnetic performance of R-Fe-B.

The molded body after press molding with the addition of a molding aid is called a green body, which is extremely brittle and difficult to handle.

Therefore, a major drawback is that it takes a considerable amount of effort to arrange them neatly in the sintering furnace.

Because of these drawbacks, generally speaking, R-Fe-B
Not only does the production of sintered magnets of this type require expensive equipment, but the production method has poor production efficiency, resulting in an increase in the production cost of the magnets. Therefore, it is not possible to take advantage of the advantages of R-Fe-B magnets, which have relatively low raw material costs.

Next, permanent magnets (2) and (3) are manufactured using a vacuum melt spinning device, but this device currently tends to have very low productivity and is expensive.

The permanent magnet (2) is isotropic in principle, so it has a low energy product, and the squareness of the hysteresis loop is also poor, so it is disadvantageous in terms of temperature characteristics and usage.

The method (3) for manufacturing permanent magnets is a unique method of using hot press in two stages, but it cannot be denied that it is inefficient when considering actual mass production.

Furthermore, in this method, at high temperatures, for example, 800''C or higher, the crystal grains become significantly coarsened, resulting in an extremely low coercive force iHc, making it impossible to produce a practical permanent magnet.

The method (4) for manufacturing permanent magnets simplifies the manufacturing process the most because it does not involve a powder process and only requires one step of hot pressing, but in terms of performance it is inferior to (1) to (3). There was a problem that it was slightly inferior.

The present invention is intended to solve the above-mentioned drawbacks of the prior art, particularly the drawback (4) in terms of performance of permanent magnets, and its purpose is to provide a high-performance, low-cost permanent magnet. be.

[Means for Solving the Problems] The permanent magnet of the present invention relates to a rare earth element (1?)-transition metal element (M)-group IIIb element (X) system permanent magnet, and specifically, R (Pr, Nd, Dy, Ce,
At least one rare earth element selected from La, Y, Tb) -M (Fe, Co, Cu, Ag, A
(at least one transition metal selected from u, Ni, and Zr)-X (at least one group IIIb element selected from B, Ga, and AI) as a basic raw material component This permanent magnet is made by excluding the R-rich liquid phase, which is a non-magnetic substance, from the components and concentrating the magnetic phase, and is characterized by having magnetic anisotropy due to mechanical orientation.

Furthermore, specifically, 12 to 25% R2 in atomic percentage
65 to 85% M and 3 to 10% ~
The permanent magnet as described above is made by concentrating a magnetic phase consisting of particles of 87% M and 3 to 10% X, and has magnetic anisotropy due to mechanical orientation, and further has a crystal grain size. is 0.311 m to 150 μm, and the ratio of the R-rich phase is 10% or less (excluding 0%).

Also, in terms of atomic percentage, 12 to 25% Pr, 85 to 8
5% Pe and 3-10% B are used as basic raw material components, and the R-rich liquid phase, which is a non-magnetic substance, is excluded from the basic components, and 10-18% P'',72- It is made by concentrating a magnetic phase of 87% Fe and 3 to 10% B, with a crystal grain size of 0.3 μm to 1504 and a Pr-rich phase ratio of 10.
% (excluding 0%) of magnetic anisotropy due to mechanical orientation.

[Function] The present inventors evaluated a large number of R-Fe-B based cast alloys and found that a high coercive force can be obtained by applying appropriate heat treatment to the Pr-Fe-B based alloy, and further, Based on this alloy, the present invention was achieved as a result of research into the effects of mechanical orientation treatment using hot pressing and the effects of additive elements on improving magnetic properties.

That is, in the present invention, R is Pr, Nd, Dy, Ce, La,
At least one rare earth element selected from Y, Tb, and M is Pe, Co, Cu, Ag, Au, Ni
, R-M-X is at least one transition metal element selected from Zr, and X is at least one IIIb group element selected from B, Ga, and AI.
In this method, a magnet with high performance comparable to conventional methods can be obtained using a method of casting, hot pressing, and heat treatment, which does not include powder processes, for alloys of the present invention.

In the present invention, FIGS. 2(a)-(
The permanent magnet of the present invention is manufactured by following the process shown in C). The initial R-M-X is converted from the basic ingredients of the raw material to the liquid phase of R-rich, which is a non-magnetic substance, at a concentration of 750 to 1050.
By thermal processing such as hot pressing at a temperature of ℃, the ferromagnetic phase particles are extruded outward as shown in Figure 2 (b), the ferromagnetic phase particles increase, and only the particle phase becomes fine and oriented, increasing the magnetic properties of the magnet. It is something.

In addition, when manufacturing magnets, RFe is used as a ferromagnetic material.
B (atomic ratio), RFe B2 14
11.7 82.4 5.9 (atomic percentage)
When there is a large amount of R, the R-rich phase acts as a non-magnetic substance, and when there is a large amount of B, the B-rich phase acts as a non-magnetic substance.

In the present invention, the R-rich phase is made non-magnetic by blending a relatively large amount of R from the beginning, but when B is present in a large amount, the B-rich phase is made non-magnetic as well.

Next, the reasons for limiting R, M, and X of the basic raw material components in the present invention will be described.

R: 12-25% If it is less than 12%, the amount of R-rich phase will be small and it will be easy to crack, making hot working difficult. Moreover, if it exceeds 25%, the amount of the non-magnetic phase increases too much and the concentration of the magnetic phase becomes insufficient, resulting in a decrease in performance, so it was determined as described above.

M: 65-85% If it exceeds 85%, the amount of R-rich phase will be small and hot working will be difficult, and if it is less than 65%, the amount of non-magnetic phase will increase too much and the concentration of magnetic phase will be insufficient, resulting in poor performance. was determined as above.

X: 3 to 10% If it is less than 3%, the amount of magnetic phase will be too small and high performance will not be obtained. Moreover, if it exceeds 10%, the amount of non-magnetic phase increases and hot working becomes difficult, so it was determined as above.

As a result of applying the raw material basic components specified above to the present invention, the resulting component values are R: 10 to 18%, M
Near: 2 to 87%, X: 3 to 10% is a composition range in which high magnetic properties can be obtained.

In addition, in the present invention, the crystal grain size is 0.3 μm to 15 μm.
Although it is limited to the range of 0-, the reason for this will be described.

A crystal grain size of 0.3- is said to be the critical grain size of single magnetic domain grains. That is, when the particle size becomes smaller than 0.3-,
The separation curve is the same as that of the permanent magnet (3) in the conventional method described above, and the magnetization is poor.

Further, if the crystal grain size exceeds 150 μm, the coercive force obtained even after hot working becomes lower than 4 KOe of a ferrite magnet, making it impractical, so this setting was made.

Furthermore, as shown in FIG. 3, which will be described later, the less the nonmagnetic R-rich phase is, the higher the 4πIs (solid line) is. As the R-rich phase increases, 4π1s decreases, so in consideration of practicality, 10x or less is desirable. However, 0
%, the coercive force will be lost, so it was set at more than 0% and less than 10% (weight).

Next, examples of the present invention will be described.

[Example] [Example 1] A process diagram of the manufacturing method according to the present invention is shown in FIG.

First, according to the manufacturing process shown in FIG. 1, Pr Fe B CL11 was prepared using an induction heating furnace in an argon atmosphere.
An alloy having a composition of 7 7B, 5 5 1.5 was melted and then cast.

At this time, rare earth, iron, and copper raw materials with a purity of 99.9% were used, and boron was ferroboron.

Next, this cast ingot was placed in an argon atmosphere for 100 min.
Hot pressing was carried out at 0° C. with a processing degree of 80%.

The press pressure at this time was 0.2 to 0.8 ton/cd, and the strain rate was 10-3 to 10-'/sec.

Thereafter, it was annealed at 1000° C. for 24 hours, cut and polished, and its magnetic properties were determined.

The magnetic properties and other characteristic values of this magnet were used as a comparative example to compare the sintered permanent magnet (Nd
PeB) and (3) are shown in Table 1 together with the values for the permanent magnet (Nd13FcB).

82.6 4.4 All magnetic properties are B- at a maximum applied magnetic field of 25 kOe.
H) Measured using a racer.

As shown in Table 1, it is clear that the magnet of the present invention is not inferior in magnetic performance but superior in magnetization compared to the conventional permanent magnets (1) and (3).

Cast magnets containing copper are also effective in increasing coercive force and improving orientation.

Table 1 The conventional sintered permanent magnet (1) is 0. The carbon content and porosity are different, and the crystal grain size is different from the conventional permanent magnet (3), and the magnetization is excellent.

Next, the operation of the magnet of the present invention will be described.

FIG. 2 is a detailed explanatory diagram of the present invention.

In Fig. 2, 1 is Pr2Fe14B phase particle, 2 is α
-Fe phase, 3 is an R-rich phase, and 4 is an R-rich liquid phase.

In the present invention, the permanent magnet of the present invention is manufactured by following the process shown in FIG.

FIG. 2(a) shows the state of the main phase when the Pr re B Cu raw material table 17 7B, 5 5 1.5 gold is melted and cast to form a cast ingot, and as shown in the figure, Pr2Fe1
The 4B phase particles 1 contain a small amount of a-Pe phase 2. The space between the Pr2Fe14B phase particles 1 is filled with a non-magnetic P rich phase 3.

FIG. 2(b) shows the state during hot pressing, and at a temperature of 800 to 1050°C, the R-rich phase 3 melts into an R-rich liquid phase 4, and this liquid phase 4 is The α-Pe phase 2, which is expelled and pushed outward by the pressure applied from the outside such as hot pressing, diffuses and disappears, and the Pr2Fe14B phase particles 1 are refined during the hot pressing and the crystal main axis The direction is oriented in a certain direction.

Figure 2 (c) shows the state of the magnet, where the R-rich phase 3 that seeped out has been cut off, and the magnet is made up of fine P2Fe14B phase particles 1 oriented. Use the center part.

The space between the Pr2Pet4B phase particles 1 is filled with the R-rich phase 3, iron, and copper, but the amount is much smaller than that of the cast ingot, and the magnetic phase Pr2Fe14B phase particles 1 are much larger than the initial raw material composition. It is clear that it is concentrated.

FIG. 3 shows a relationship between the R-rich phase content of the magnet, 4πIs, and iHc. Also, in Fig. 4, Prt7Pe
78.5 5 1.5 Two direction curves parallel and perpendicular to the press are shown when 4πI-H of a magnet with a composition of B Cu is pressed.

Figure 3 shows that the less the nonmagnetic R-rich phase is, the more 4πIs
(solid line) indicates an increase.

Since 4πIs decreases as the R-rich phase increases, it is understood that 10% or less is desirable in consideration of practicality.

Figure 4 shows a typical hot pressed Pr-Fe-B-Cu
Two types of magnet demagnetization curves are shown: easy magnetization direction and difficult magnetization direction.

From FIG. 4, the easy magnetization direction is parallel to the pressing direction. From the separation curve in the direction of easy magnetization, this magnet is nt
It is considered to have a coercive force mechanism of +ceation type.

It can be seen that although the anisotropy direction is the same as that of the conventional permanent magnet (2), the coercive force mechanism is different.

[Example 2] Similarly to Example 1, PI7+7Pe7 was produced using an induction heating furnace in an argon atmosphere according to the manufacturing process shown in FIG.
An alloy having a composition of °B4 was melted and then cast.

At this time, similar to Example 1, rare earth and iron raw materials with a purity of 99.9% were used, and boron was ferroboron.

Next, this cast ingot was placed in an argon atmosphere for 100 min.
Hot pressing was carried out at 0° C. with a processing degree of 80%.

The press pressure at this time was 0.2 to 0.8 ton/ej, and the strain rate was 10-3 to 10-'/see.

After cutting and polishing, the magnetic properties were measured and 1000
After a heat treatment of 24 hours of annealing at .degree. C., the magnetic properties were measured again.

Table 2 shows the magnetic properties before and after annealing, and Table 3 shows the various characteristic values after annealing. Furthermore, Figure 5 shows the demagnetization curve of the cast ingot (1) and the demagnetization curve of the magnet after annealing (2).
) is shown.

As shown in Table 2 and Table 3, the raw material composition is PrtyFe79B 4
The magnet composition is Pr re B and the magnetic phase is concentrated 14.8 80.3 4.9 . The magnetic properties showed good results, and it is clear that the magnetic properties are further improved by annealing, especially as shown in Table 2 and FIG.

Furthermore, under the same manufacturing conditions, the PrQ of the cast ingot was
Alternatively, when B111 was changed, the characteristic values of the finished magnet showed changes as shown in FIGS. 6 and 7.

FIGS. 6 and 7 show the composition dependence of hot-pressed magnets, and the measurement directions of the magnetic properties are all parallel to the pressing direction. Furthermore, (BH) max (MGOe) increases significantly, indicating that anisotropy has been achieved.

[Example 3] An alloy having the composition Pr12Nd5Pe79B 5.5 Cut, 5 was melted and cast in the same manner as in Examples 1 and 2 to produce a cast ingot.

Next, this cast ingot was heated to 100% in an argon atmosphere.
At 0°C, the strain rate is lo-3 to 10-'/sec,
Hot pressing was performed at a processing degree of 80%.

After this, after annealing at 1000°C for 24 hours,
Cutting, polishing and composition '9.5 Nd4 Fe80.IB6.1'
A 0.3 magnet was obtained and the magnetic properties of this magnet were measured.

The magnetic properties and other characteristic values of this magnet are shown in Table 4.

As shown in Table 4, it is clear that even if the composition is changed as described above, the magnetic properties are excellent.

Table 4 Table 5 Alloy composition [Example 4] Alloys having the compositions shown in Table 5 were melted and cast in the same manner as in Examples 1 to 3. The same raw materials were also used.

Next, these cast ingots were hot pressed in an argon atmosphere, annealed, cut and polished, and their magnetic properties were measured. Table 6 shows the composition of the magnets, and Table 7 shows the various property values of the magnets.

Table 6 Composition of magnet [Example 5] An alloy having the composition Pr15Nc12Fe7B, 5 B5Cut, 5 was melted and cast in the same manner as in Examples 1 to 4.

The same raw materials were also used.

Next, this cast ingot was processed at 900 to 1000°C by a hot working method as shown in Table 8.

Next, it was annealed at 1000° C. for 24 hours, cut and polished, and its magnetic properties were measured.

Table 9 shows the composition of this magnet, and Table 10 shows the magnetic property values.

Hot press as shown in Tables 8 to 10.

It is clear that the characteristic values are improved in both rolling and extrusion processing methods.

Table 7 Various properties of the magnet Table 8 Table 9 Composition of the magnet Table 10 Various properties of the magnet [Example 5] Invention magnet manufactured in Example 1 and conventional magnet (sintering method)
were processed into the same composition (Nd1.Fe77B5) and the same shape, and placed in a constant temperature/humidity chamber at 40° C. and 95% to examine changes in weight. The results are shown in FIG.

As shown in FIG. 8, it is clear that the magnet of the present invention has less weight change and lower oxygen concentration in the magnet than the conventional magnet (sintered method). This is a major difference from conventional magnets.

From the above examples, R is Pr, Nd, Dy, Ce, La
, Y, and Tb, and M is Pa, Co, Cu, Ag, old, Au,
A permanent magnet whose basic raw material is at least one transition metal element selected from Zr, where X is at least one Group IIIb element selected from B, Ga, and AI, has a high coercive force. It is made anisotropic by heat treatment such as hot pressing, and the maximum (BH) max is 43.
It is clear that it can reach as much as 6MGOe.

[Effects of the Invention] As described above, the permanent magnet of the present invention has the following effects.

(1) The manufacturing process is simple, so the cost is low.

(2) Since the 02a degree in the magnet is low, it has little activity against oxygen and can improve weather resistance.

(3) Good machinability has the effect of reducing costs.

(4) Compared to magnets produced by conventional sintering methods, processing man-hours and production equipment investment can be significantly reduced.

(5) Compared to magnets made by conventional melt spinning method,
It is possible to create high-performance, low-cost magnets.

[Brief explanation of the drawing]

Figure 1 is a manufacturing process diagram of the R-Fe-B magnet of the present invention, Figure 2 is an explanatory diagram showing the action of the present invention, and Figure 3 is a diagram showing the R-Fe-B magnet of the present invention.
Figure 4 is an illustration of the relationship between rich phase content, 4πIs, and iHc. Figure 4 is an explanatory diagram of the press parallel and perpendicular two-way curves when 4πI-H of a magnet is hot-pressed. Figure 5 is the relationship between the rich phase content and 4πIs and iHc. An explanatory diagram showing the magnetic curve and the demagnetization curve of the magnet after annealing, FIGS. 6 and 7 are relationship diagrams with the characteristic values of the magnet when Prff1 or Bi is changed, respectively,
FIG. 8 is a weight change diagram between the magnet of the present invention and a conventional sintered magnet. In the figure, 1: Pr2Pe14B phase particles, 2: a
-Fe phase, 3: R-rich phase, 4: R-rich liquid phase. Fig. 3 RrjcMn@Shodo (wt%) Fig. 4

Claims (5)

[Claims] (1) R (where R is at least one rare earth element including Y), M (at least one transition metal element), and X (at least one group IIIb element)
seed) as the basic raw material component, excluding the non-magnetic R-rich liquid phase from the basic component, and concentrating the magnetic phase,
A permanent magnet characterized by having magnetic anisotropy due to mechanical orientation. (2) R is at least one rare earth element selected from Pr, Nd, Dy, Ce, La, Y, and Tb; M
is at least one transition metal element selected from Fe, Co, Cu, Ag, Au, Ni, and Zr, and X is B
, Ga, and Al.
The permanent magnet according to claim 1, characterized in that it is made of a IIIb group element. (3) 12 to 25% of R, 65 to 85% of M, and 3 to 10% of and 10-18% R, 72-87% M, 3-1 atomic percentage
3. The permanent magnet according to claim 2, wherein the permanent magnet is made by concentrating a magnetic phase consisting of 0% X particles and has magnetic anisotropy due to mechanical orientation. (4) Claim 3, wherein the crystal grain size is 0.3 μm to 150 μm and the ratio of R-rich phase is 10% or less (excluding 0%).
Permanent magnet as described. (5) 12-25% Pr in atomic percentage, 65-85%
Fe and 3 to 10% B are the basic ingredients of the raw material, and the R-rich liquid phase, which is a non-magnetic substance, is excluded from the basic ingredients, and 10 to 18% Pr and 72 to 87% Fe are made by atomic percentage. ,
It is made by concentrating 3 to 10% B magnetic phase, and the crystal grain size is 0.
．． A permanent magnet having a diameter of 3 μm to 150 μm, an R-rich phase ratio of 10% or less (not including 0%), and having magnetic anisotropy due to mechanical orientation.