DE1918909C3 - Process for the production of sintered ferrite molded bodies - Google Patents

Description

2. The method according to claim 1, characterized ge ao indicates that the solids concentration in the suspension is about 65 to 50%.

3. The method according to claim I or 2, characterized in that the powder has an amount of

S up to 70 * / «with a grain size of at most as 2 μ 90 to 20% with a grain size of 2 to 5 μ, and maximally 10% with a grain size of S contains up to 20 μ.

4. The method according to claim 1, 2 or 3, characterized by an alkaline suspension, the pH of which is around 10 to 11.

5. The method according to one or more of claims 1 to 4, characterized by the use of sodium silicate and / or Triethylamine as a dispersion aid.

6. The method according to one or more of claims 1 to 5, characterized in that add a protective colloid, such as ammonium alginate, to the suspension at a concentration of about 0.05 until I weight percent is added.

7. The method according to one or more of claims I to 6, characterized in that the cast product is sintered at a temperature higher than 1000 ° C.

8. The method according to one or more of claims 1 to 3, characterized in that a pre-sintered and then pulverized material is used as ferrite powder.

9. The method according to one or more of claims 1 to 3, characterized in that a material pulverized without pre-sintering is used as a powder.

10. The method according to one or more of claims 1 to 3, characterized in that as a powder, a mixture of pre-sintered and then pulverized material as well as material that has been pulverized without pre-sintering is used finds.

The invention relates to a method for Manufacture of sintered ferrite moldings. Such moldings are mainly used

You know depending on gnetischje or ferro properties.

Conventionally, I '^ t-jOrmköxper, z. B. Fenatkerne oiter ceramic capacitors in Trockenpreßverfahrea made of powdery or granular, pre-sintered material. A production of ferrite fittings from kompjiziei * er Shape, cast overall dimensions or small thickness is extremely difficult because of the required molds and presses. Overcoming these difficulties is often associated with unacceptable economic outlay. In addition, dry-pressed ferrite moldings can have differences in density and mechanical properties Have stresses, resulting in poor mechanical or electrical properties.

In addition to the dry pressing process generally used in practice, other manufacturing processes have also become known which are intended to avoid the disadvantages mentioned in part, but not themselves could generally prevail. For example, from the French additional patent 67 873 to patent 1 114 010 a process for the production of ferrite permanent magnets is known, in which the powdery! Starting material water is added so that a doughy mass is produced. This is for the purpose of dehydration using a vacuum and by means of a The pressure ram is pressed into a hollow mold, with a strong magnetic field on the doughy at the same time Mass acts. The body shaped in this way is then further dried and sintered at a suitable temperature.

In a method known from British patent specification 844 706, the ground and mixed starting material is slurried with volatile solvents such as methyl alcohol, the A slurry of synthetic resin dissolved in acetone and wax dissolved in carbon tetrachloride of at least 10 percent by weight added as a binder and the pourable mass obtained poured into molds. However, the high proportion of additives required for adequate mechanical strength has an effect disadvantageous on the electrical and magnetic properties of the moldings.

In the field of ceramic production - unlike in ferrite production - the moldings are conventionally produced using the slip casting process. A suspension is used as a slip denotes powdery ceramic substances. The powders can be clay or a mixture of oxides, carbides and the like. The term "slip casting" denotes the casting of this Slip into a liquid-absorbent form, usually made of plaster of paris, and the penetration of the liquid into the form due to capillary forces. Around It is well known to be able to keep the water content of the slip as low as possible (e.g. "Glas-Email-Keramo-Technik", 19 [1968], pp. 1 to 6) Dispersion aids are used, which can significantly reduce the viscosity of the slip. the However, for various reasons, knowledge gained with regard to clayey and non-clayey ceramics cannot be transferred to the manufacture of ferrite molded bodies. This is particularly due to the fact that it is in production of ceramic moldings practically only on the shape, which is easy to maintain by means of a casting process.

3 4

Men and dimensions and a sufficient mecha- this effective density is, if possible

cysche strength is important, while it should reach 8g / ccm for ferrite.

Forra bodies decisive · on their electrical or borrowed proven »the FeststQfi & enzerttratiori ^ er suspen-

Magnetic properties ankoiwnfc So in sion can have a value of over 50%. as

the additives contained in the fexrites have been found to be particularly advantageous in a range of approximately

the loss factor and the electrical conductivity 65 to 80% exposed at one concentration

influence. On the other hand, sticking without a binder will be less than 50% the time required for casting

presintered ferrite grains because of their normally unacceptably large, which also leads to disadvantages-

only leads to the shape forming the contact surfaces with the ferrite structure obtained,

Failure to apply pressure only so insufficiently io i In order to obtain a slip with this as essential

each other that casting processes of the type mentioned knew the required solids concentration hand-

so far to be able to avoid these disadvantages dry pressing and a uniform distribution

proceedings were not able to displace them. the Femtkömer different diameter to

The invention is based on the object of achieving a, furthermore, is the addition of a water-soluble one Process for the production of sintered ferrite 15 dispersion auxiliaries of the specified type and To develop moldings, the considerably simpler amount required. Below a proportion of is to be carried out as the conventional dry - 0.05 percent by weight is the degree of dispersion to the compression process and any largely arbitrary and single, above a proportion of 1 percent by weight multiple shaping permitted, but electrical or the degree of dispersion decreases again considerably. magnetically the conventionally produced ferrite so it also follows and has become through investigation moldings products of at least equivalent quality are confirmed that delivered within the specified range, the breaking strength of the ferrite moldings

This object is achieved according to the invention is particularly high.

by using the slip casting process, as a particularly useful dispersion adhesive

but with the following conditions: as come sodium silicate and / or triethylamine

_{if the} j ^ g ^ ,,., ^ limits are exceeded

In order to carry out the procedure, the.

When using plaster molds, it is required Conditions required. 40 Hch that the suspension is alkaline, given the shape

A particularly significant meaning comes otherwise would be attacked. As particularly useful the grain size distribution increases. To a ferrite for the implementation of the construction according to the invention To obtain, metal oxides must drive pre-sintered has to maintain a pH value of will; it is difficult to prove this vo sintered mass in 10-11.

To crush particles of less than 2 to 3 μ. 45 The advantages of manufactured according to the invention stems from a substantial part of the previous th Feirit molded bodies are briefly summarized-inapplicability of a slip casting process is that with relatively little Aufdie production of ferrite molded bodies. A grain size distribution suitable for any shape or shape can in particular be there and the molded bodies produced can be achieved in terms of their mechanical properties in that the presintered powder has niches, electrical or magnetic properties in a suitable ratio with fine particles from the same starting materials herm with a grain diameter of less than 2 to conventional processes at least 3 μ, for example unsintered powder, mixed are equivalent, usually even superior,
will. Such a controlled bringing about the

The required grain size distribution given was explained in more detail because of the different nature of the starting points and several exemplary embodiments. It shows
substances not known so far. F i g. 1 the grain size distribution in the case of

It has proven to be particularly advantageous within the use of an inorganic dispersant with a grain size distribution if an exemplary embodiment according to the invention,
the powder an amount of 5 to 70 ⁰ / o with a 60 Fig. 2 the dispersion curve of the particles if grain size of at most 2 μ, 90 to 20% with a water glass is used as a dispersant,
Grain size of 2 to 5μ and a maximum of 10% with Fig. 3 the mechanical strength of the invention

contains a grain size of 5 to 20 μ. appropriate product, if an inorganic dispersant

The solids concentration in the suspension is compared with that of the sionic agent used another essential feature of the invention. In order to obtain usable ferrite moldings produced by means of a conventional process, ducts,

these have an effective density of more than 3 g / ccm. 4 a characteristic curve of the casting time as a function

point. The higher the slip density, the better its quality,

FIGS. 5 and 6 show a distribution curve according to FIG. 1 in a further embodiment,

7 shows the grain size distribution of a Ni-Zn ferrite as a further embodiment,

Fi g. 8 and 9 the slip characteristics of the Ni-Zn ferfit to which an organic dispersant has been added,

10 and 11 the casting characteristics of the materials according to FIG. 8 and 9,

12 to 17 show the particle size distribution when organic dispersants are used in further exemplary embodiments, and FIG

18 shows the grain size distribution for explanation the maximum density.

In the following description, exemplary embodiments of the invention are explained in more detail.

Bet game 1

Fe ₁ O ₈ , ZnO and CuO were mixed in a weight ratio of 6: 2: 2, the mixture was pre-sintered at 900 ° C and then finely comminuted in a ball mill in 10 positions. The result is referred to as powder Mr. 1. The grain size distribution of powder No. i is shown in Table 1 and in Fig. 1. 1 shown as curve 1. Fig. I shows the integrated weight percent as a function of the diameter of the particles.

Powder No. 2 ίο Table 1 is a mixture of Fe * O ,, ZnO and CoO in a weight ratio of 6: 2: 2 that has been crushed but not presintered. The grain size distribution of powder no.2 et also shown in Table 1 and FIG. 1 as curve 2

Table 1 2Μβ5μ S to 20 μ Middle Grain size distribution 90 8th (μ) Particle diameter 0 0 3.2 0.75 1 2 2 100

Table 1 shows that the maximum and minimum diameters of the particles are about 20 and about 2p, respectively. The powders Nos. 1 and 2 Table were mixed ratio shown 2 in the la, and water was added to the mixture afc dispersant to-™ VdajB, the ^ ciAickerdJchte to 75 Ve sized "* ~ ^Α. It was then" water glass into the / To prepare the silt _4,

<ias the slip casting process sas-

ctib dasiSchflckergiiBverfahren ans- "ψαζ if the ¹ PuIvCt Nr 2 m more 'laltenisL

■ 2 became with a ratio like that

Table 2 Mixing ratio and properties

those produced in the slip casting process

materials

M. Mixing ratio in Weight percent C. A. B. 90 ίο Powder No. 1 100 95 10 Powder No. 2 0 5 proportion of of the particles «5 11.8 I ₃ below 2μ (· / «) 2 6.9 The plasticity is properties The plasticity is well, and there were bad, and it no cracks cracks occur easily confesses-the spinning- on. The pouring availability is good is out quickly The surface is leads to kick it ever smooth. The Schlik- but shift casting process gen on. Of the can run Surfaces- will state is not well, the slippery cast can not go out be guided

Table 3 Comparison of properties

Density of products according to the pressing

Volume weight after sintering at 1000 ⁰ C ...

Electrical Properties

e tan of μ _Λ

Dry pressed product (the Pressure is

It / cm ¹ )

2.7 (g / cc) 4.63

420 2.0-10- «

Product manufactured using the slip casting process

2.80 (g / cc) 4.75

450 1.6-10- *

In this table, μ is the initial magnetic permeability and tan δ is the loss factor. The Ta-5 'beauty 3 shows that the density of the products, that the invention was prepared in accordance with slip casting is greater than that of a customary Trok ioßfhlhr- ^ ~ ^w ^ """~ ---

as well as ^^^.

3S the electricsfeenjSgen ^ l ^ n; than the latter. ~ ^ - ^ ---

Wig.1 prefers the Vt

iris the Snspensidnsschidit <d.

", and 2. are in the Vediält-ICS, which in the usual Tiok-It ymtäc: Die Tabe ^ 3

wild. In derTai »elle2 shows,

both products, and äe and.'die dektriscoen Fig »3 ze d F

(that at 60 ° C "over> p

and had no water content) and the proportion of water glass. For comparison, the mechanical one Strength of a dry pressed product also shown.

In Fig. 3, the ordinate axis indicates the flexural strength (kg / cm ² ) and the abscissa axis indicates the proportion of water glass, which ^{varies from 0 to 1 3} / o; the points a, b, c and d show the typical value of the flexural strength in the case of 0.25, 0.5, 0.75 and 1.0% water glass, which was added in percent by weight Ϊ &. The upwardly and downwardly extending H arrow at each point indicates g "of the bending strength, the distribution of the value. G In F i. 3, the point e shows the $ bending strength of the in usually J dry-pressed product, which with a pressure of 1.0 t / cm ² , and the arrow at this point shows: also the distribution of the strength value.

S Fig.3 shows that the mechanical strength of the

ψ the slip-cast product is better than that of the dry-pressed product, which was pressed with a pressure of 1 t / cm *, when waterglass is added in 0.25 to 1.0 percent by weight.
I Figs. 2 and 3 show the following: In order to

S sufficient mechanical strength of the Cu-Zn ferrite In order to achieve this with the slip casting process, 0.25 to 1.0 percent by weight of Wasi should be added H will be. In addition to the Cu-Zn-S? Ferrite also all other types of fenites like that

I Cu-Zn ferrite manufactured using the slip casting process || if only the most suitable proportion for water glass according to the quality, the sin-

II tert temperature and the grain size distribution of the Ü ferrites is selected.

I F i g. 4 shows the relationship between the casting

I speed and the slip density in the case of the f Mixture C of Table 2, where water and I 0.5 percent by weight of waterglass as the dispersant I were used. F i g. 4 shows that when the

I slip density ^{falls below 50 c} / o, the casting speed

Idleness (i.e. the speed at which to pour

I of an inch is required) over 120 minutes

I increases what in terms of effective manufacture

; _; and a uniform product is undesirable. Of-

Half the slip density should be kept above 50%

I den.

B e i s ρ i e 1 2

The powder 1 of Example 1 was further crushed by wet vibration for 5 hours, and the powder thus obtained was referred to as powder 3. In the same way as the powder 1 with Aus * - "* g, at 100p ⁰ C and the 2erilmühle during -20 hours 5 as Pjilver.4 r *. These samples are shown in Ta-I C '

As Table 4 shows, the maximum diameter of the particles is 20 μ.

The above-mentioned powders 1, 3 and 4 were mixed as shown in Table 5, and the samples A ', B ', C, D' and E 'were obtained. The slip density and the added proportion of water glass of this Samples A ', B', C, D ', and E' were set to 70 and 0.5 weight percent, respectively, and then were Experiments carried out with the slip casting process.

Mixing ratio in percent by weight B ' C. D ' E ' A ' 15th 15th 100 0 * 5 powder 1 ... 0 85 70 0 0 Powder 3 ... 100 0 15th 0 100 Powder4 ... 0 Contained Share of * ° particle smaller 13.5 11.5 2 0 than 2 μ 16

TfomgröBehverteihmg

OWs 2μ 2 to 5 μ 5 TiIs 20 μ
<· Λ) Middle
DoTcli-
%) P \ tttverä> ... *,
Powder4 i 16
0 81
16 3 2.3
7.0

According to the result of the experiments, could

As samples A ', B', C are slip poured, but in the case of Samples D 'and E', cracks and layers occurred and the slip casting process failed not be carried out.

The above examples show the following:

Ferromagnetic ferrites can be produced in the slip casting process if the maximum size of the ferrite particles of the ferromagnetic ferrite is 20 μ and the particles, the size of which is below about ¹ Z _{10 of} the maximum size, are more than 5 percent by weight if the slip density is more than 50% and when inorganic dispersants such as water glass are used. When the slip-cast ferromagnetic ferrites are sintered, the product obtained shows electrical properties better than those of the conventionally dry-pressed ferrites.

As mentioned above, in the slip casting method of the ferrite core, water glass is used as a dispersant; however, the main components of water glass are Na ₂ O and SiO ₂ , and therefore the electromagnetic properties are sometimes adversely affected by the addition of the dispersant according to the materials constituting the ferrite.

On the other hand, in the case of fenites, raw materials such as. B. metal oxides, a low plasticity, and therefore the grain size should
carefully controlled as mentioned above
if the slip casting process has been carried out

otherwise it cannot be carried out ^ beshl .- ^ -.
the splitting process and ^ the ^ additional means
be sought. "1 ^""?. ^

In order to transfer the aforementioned brobles to JS
the Schlickergußverfalu'enrrleic ""

can and around the
the ferrites too
Alginate the ferrite ....____
nat acts as a protective
medium and as a binder ^

«5 organic binders like r
can be turned.

The above-mentioned procedures ^ ._ _.
on the basis of "examples toi individual!

9 10

Example 3 weight percent ammonium alginate mixed so that 7 shows the grain size distribution of a Ni slip density of 76 percent by weight. That Zn ferrite powder, which consists of 4% Ni, 33% Fe ₂ O ₃ , mixture was stirred for 2 hours.

50 ° / d ZnF & iO ₄ , 2 ° / o CuO and 11 ° / o MgO zuijam- The properties of this slip were fol-

sets. The raw materials were finished in 24 hours:

Finely divided in a ball mill and not pre-_. ", _,. , ...

_s j _ntert ^{6 6} Specific weight 2.45

The raw materials prepared in this way were given a relative viscosity ... ..... 7.35

0.4 percent by weight triethylamine and 0.15 Ge pH. ..... ;; .... 10.20

The relative viscosity is defined as follows: Relative viscosity = -—

Outflow time of the swallower Outflow time of distilled water · specific gravity of the slip

The F i g. 8 and 9 show the relationship between the added amount of triethylamine or ammonium alginate and the outflow viscosity and the PH value.

In Fig. 8 the proportion of ammonium alginate to be added is included as a parameter and FIG. 8th shows that the pH concentration depends more or less on the proportion of triethylamine and the viscosity of the slip can be influenced by the proportion of triethylamine when the proportion of ammonium aiginate is low.

In Fig. 9, the proportion of triethylamine is included as a parameter, and the viscosity of the slip is influenced by the amount of ammonium alginate when the amount of triethylamine is low.

In the F i g. 8 and 9, the preferred range of viscosity required for the slip casting process is below the dashed line.

When carrying out the slip casting process, it is necessary to adjust the state of the slip accordingly the size and thickness of the pressed product.

It is therefore difficult to determine which slip properties are generally desired are, however, it was possible to go through the slip casting process if the slip was a suitable one Spinnability and excellent flowability has in the in Figs. 8 and 9 of properties.

FIGS. 10 and 11 are the diagrams corresponding to FIG Casting speed and dry flexural strength show when the proportions of triethylamine and ammonium alginate are changed.

In Fig. 10 is the proportion of ammonium alginate included as parameters and in FIG. Il the proportion of Tnäthyianiin.

In FIG. 11, the casting speed can be controlled by the proportion of ammonium alginate, it is possible to determine the mold strength (kg / cm ⁸ ) by means of its proportion. " ^x

:. If, however, Amfflomom-Aigaiat ddei'triäthylanan is added individually to produce the slip the dispersion is insufficient and the flowability is poor, tt & d dfet & chlicker karm not kfflSäretf be used, he

et become

^ g'tina Triäthyhunm widen, Hst the dispersion uneiäes every dispersion

the slip cannot be used at all if the proportion is above 2 to 3 percent by weight lies.

In any case, when performing the By using the slip casting process, the desired slip can be obtained by selecting and using the correct proportion of each of the two ingredients.

A ferrite core was produced under the above-mentioned conditions and ^{sintered at 1200 °} C. for 2 hours. The electromagnetic properties of the ferrite core are shown in Table 6.

For comparison, the properties of a conventionally dry pressed and sintered core and that of another example according to the invention in which an inorganic dispersant how water glass was used is also included in Table 6.

Table 6 properties

Bms (Gauss). ffc (Oer) ... β (-10 ⁸ Q-Cm) d (gr / cm ^s ) ..

Dry press procedure :

565

2400

0.30 100 4.50

According to the invention procedure

organic Dispersant

590 75

2450 0.20 7th 4.55

organic dispersant

670

73

2490

0.25 105 4.55

* - ♦ ⁰

not shown, in table 6 ^ ₀ 'is the = magnetic AntangP permeability, Q is the quality factor, B / ns, d flfÜa in each case the remanent magnetism' d

SSi tive force after saturation, ^ 1st ^ ° eYsp

and d is the density. ^ * · - / ·; - :

The properties shown in the table are those obtained when the slip casting process is carried out when the density of the product is the same

«O that of the dry-pressed, ie .2,4 © tem ³ , and both are sintered at 1200 ° C: *

As can be seen from Table 6, the properties of the product obtained according to the invention are better than that of the conventionally dry-pressed & ,. imd

The products obtained by using organic dispersants are Jtesscär or. '"*"" same as the products that are used when referring to " * organic dispersants (water glass) ι

Example 4

The ferrite powder, which is composed in percent by weight of 12 ¹ V * Nio, 19% ZnO, 65% Fe ^ O ₃ and 4% CuO, was chosen, the raw materials were sufficiently mixed, pressed and pre-sintered at 950 ° C for 2 hours and then finely divided in 20 hours using a ball mill. The grain size distribution of the powder obtained is iriFi ^l g.V2gezeigt. '' ■ '. '■' ■ '''■ ■ ■ /

0.6% triethylamine and 0.1% ammonium alginate were added in percent by weight to the powder prepared above added so that the slip density was 75 percent by weight.

In view of the slip properties in this case, the specific gravity was 2.45 relative viscosity 7.35 and the pH concentration 10.8.

This prepared mixture was subjected to the slip casting process and ^{sintered at 125O 0} C for 2 hours; the electromagnetic properties of this product thus obtained are shown in Table 7.

In Table 7, the properties of the product whose composition is the same as above, and which is obtained by the usual dry press and sintered at 125O ⁰ C for 2 hours, also shown.

Table 7
properties

₀
Bms (Gauss).

Hc (Oe) ....
_e (-10 «Q-cm)
d (g / cm *) ...
ß

Dry pressing process

200
3150

1.0
4830

4.60
180

According to the invention procedure

240
3260

0.8
5080

4.65
175

From Table 7 it can be seen that the fiction, contemporary slip casting process to better own conducts than the usual procedures.

Example 5

The Mn-Mg ferrite was selected, which is composed in percent by weight of 25% MnO, 10% MgO and 65% Fe ₂ O ₃ . The raw materials were sufficiently mixed vorgesmtert over 3 hours at 900 ° C and the resulting mass is finely divided in a ball mill. The particle size distribution of ¹ shown in erihaltenenTpiaiversisl ^ ^ i ^ TS.
* 2äi the flilvteF prepared above m Ge -% & isErAte ¥ ü, 5 V ^ riä ^ & nm with 0.2% Ammoüiüni-Algiriat were added and the whole thing mixed so that dMVlSte ^ ShlitfdidÄ '^ SGSihte

m this
the

This mixture obtained in this way was subjected to the slurry freing; and EAE was then sintered 3 hours at 1400 ⁰ C; his electronic

Table properties (the properties in the microwave region) are shown in Table 8.

The characteristics of the product that one is dealing with conventional dry pressing and sintering for 3 hours at 1400 ° C are also in Table 8 shown.

BarsHe8
properties

Dry press
procedure Slip casting
procedure ι * An M (Gauss)
4π Ms (Gauss)
that means)
E. 2300
2700
300
12.0
3.1 · 10- «
4.42 2490
2920
265
2.9.10- »
4.48
12.3 tan δ
aod (g / cm »)

In Table 8, AnM is the residual magnetic flux density and 4π Ms is the saturation magnetic flux density.

as Δ Η is half the width of the ferromagnetic!) resonance, c the dielectric constant at 9000MHz, tan .5 the loss factor at 9000MHz and d the density (g / cm ^s after sintering.
Table 8 shows that the properties of the

products obtained according to the invention are excellent are.

Example 6

The Mn-Zn ferrite was selected, which is composed in percent by weight of 16% MnO, 14% ZnO and 70% Fe ₂ O ₈ . The raw materials were sufficiently mixed, pre-sintered for 2 hours at 860 ° C., and the resulting mass was finely divided in 32 hours in a ball mill. The particle size distribution of the powder obtained is shown in FIG.

0.6% triethylamine and 0.3% ammonium alginate were added to the powder in percent by weight - 45 and the whole thing was mixed up in such a way that one Adjusted slip density of 75 percent by weight.

With regard to the properties of the slip in this case, the specific weight was 2.40, the relative viscosity 12.0 and the pH concentration 10.2.

The mixture produced above was subjected to the slip casting process and sintered ^{at 1300 ° C. for 3 hours.} Dy. electro-magnetic dia
shafts of:

shown.

on the properties of the sneaker

6 $ Bms (Gauss). .
Br (Gauss) ....:

iaftenadesiBro- .- 'The \ 2G ferrite was chosen, which is in Ge-83W, ^ -_ t ^ gcht ^ qzentea from 47.2% YJft, 4 & t »i '~"

3St " Vi who likes
Γ the quality factor,

residual magnetic flux oerafive force, i'die density (g / cm ^s )

_e \ ~ Attfani, 'the magnet

"Table 9 shows that the properties of the product obtained according to the invention are excellent.

Example 7

The Mn-Zn ferrite was selected, which is composed in percent by weight of 13% MnO, 18 "/" ZnO and 69 · / · Fe ₂ O. The raw materials were mixed, then presintered at 860 ° C for 2 hours, and the obtained mass was finely divided by means of a ball mill in 16 hours. The grain size distribution is shown in FIG. IS shown

The powder prepared above was in percent by weight 0.6% triethylamine and 0.3% ammonium alginate added; the whole was mixed so that the slip density was 73 percent by weight revealed.

With regard to the properties of the slip in this case, the specific weight was 2.40, the relative viscosity 12.0 and the pH concentration 10.5.

The slip was subjected to the slip casting process and sintered ^{at 1360 ° C. for 3 hours}

The electromagnetic properties of the product thus obtained are shown in Table 10.

Table 10 also shows the properties of the product that has the same composition as the product. which has been obtained above by means of the customary dry pressing process and sintering at 1360 ^° C. for 3 hours.

Table 10
properties

Bms (Gauss)
Br (GfSaB) ..
Hc (Oe)

Dry PreB procedure

7800 21

3500 700 0.1 4.9

Slip casting process

8600 20th 3610 720 0.09 4.94

and Sb ^ r!

S "1250 ° C pre-sintered and then used Finely divided up in a ball mill in 20 hours Grain size distribution of the powder prepared above is shown in FIG

The powder prepared above was in percent by weight 0.6% triethylamine and 0.2% ammonium alginate were added and the whole became sufficient mixed in such a way that a slip density of 77 percent by weight resulted.

With regard to the properties of the slip «in this case the specific weight was 2.55, the relative viscosity 9.3 and the pH concentration 11.0. The mixture thus obtained was subjected to the slip casting method subjected and sintered for 5 hours at 1450 ° C. The microwave properties of the The products obtained above are shown in Table 11.

In Table 11 are also the properties of the product indicated that the same composition as the above by means of the usual Trockenpreßveras driving and sintering for 5 hours at 1450 ° C

Tables 30th Dry pressing
procedure Slip casting
procedure 4 «M (Gauss)
35 4jiMs (Gauss)
JH (Oe)
ε 665
880
80
14.1
3.0-10- »
4.93 740
990
55
14.3
2.95 · ΙΟ "»
5.04 tano
d (g / cm ^s )

In Table 11, 4 π M is the residual magnetic flux density and 4 η Ms is the saturation magnetic flux density.

Δ H is the half-width of the microwave range (1000 MHz), ε the dielectric constant and tand the dielectric loss factor and d the density.

Table 11 shows that the properties of the invention obtained product are better than that of the product obtained by the usual method.

In Table 10, μ is the initial magnetic permeability, Bms is the saturation magnetic flux density, Br is the residual magnetic flux density, Hc is the coercive force, and d is the density (g / cm ³ ).

Table 10 shows that the properties of the invention obtained product are excellent.

Example 8

The following explanations relate to YIG magnet material (yittrium iron garnet ferrite).

Further examples

In addition to the above, slip ic was made using different! Kinds of materials produced that had different kinds of grain size distributions, and the slip casting process could be carried out excellently.

In the following Table 12 are examples of the manufactured Schlickers stated.

Triethylamine and ammonium alginate were added, and the desired density of the slurry has been received.

The specified ratios are all weight percentages.

is

Tabel Yl Slip
density
{*! ») Ammoniu y-
Origin
CIo) Triethyl
amine
(· / *) 80
65
50 Mn-Zn ferrite
Mn-Mg ferrite
YIG magnet
material 0.6
0.2
0.4 0.8
0.8
0.4

The plasticity of the oxide materials is determined by the composition of the raw materials or the manufacturing process changed..

Different types of factors exist that affect plasticity. If an organic Dispersant is used, it is necessary to have a predetermined proportion of colloidal particles contained in the powder; therefore, it is difficult to increase the plasticity, so that the implementation of the Slip casting process seems impossible. If inorganic dispersants as in Examples 1 and 2 are used, on the other hand, an important factor is that the materials correctly selected, which are suitable for adjusting the grain size distribution; which Any dispersant, d. H. which uses organic or inorganic dispersants Should be, it is necessary to keep the grain size distribution of the oxide material close to the most compact state to choose.

The fact is, however, that in order to attain the most compact state, it is necessary to finely divide the mixture into powder, and that additives are required.

Fig. 18 shows an example showing the range of Grain size distribution indicates the most compact state when the maximum diameter of the Particle is 10 μ (the area is shown by the hatching); it's very difficult that Select grain size distribution close to the most compact state, as it is from in the Fig. 7, 17 and 12 to 16 shown grain size distribution is obvious.

In order to eliminate the difficulty of the particle size distribution, an additive is required which has the property of a colloid.

When the above-mentioned inorganic dispersant is used, it is necessary to use the above-mentioned inorganic dispersant
size distribution as above mvthnt j_
len. The additive which has a colloidal property is generally referred to as a protective colloid, and this should preferably have the properties of a dispersant, a binder and a lubricant.

Various tests have shown that ammonium Al ^ nat sufficiently ι. "Possesses characteristics mentioned above.

On the other hand, it is possible to easily perform the slip casting process of oxide powders having various specific weights with various kinds of grain size distributions by taking into account the molecular weight of ammonium alginate, the degree of polymerization, the degree of substitution and the proportion of the ammonium alginate to be added
In addition, ammonium alginate is an organic

ao nic material, and it is completely broken down by sintering; therefore it is not possible that the electromagnetic properties of the ferrite are deteriorated.

If lignin, fumaric acid, tannic acid, gallic acid,

»5 starch, dextrin, polyethylene glycol or the like, the organic Materials are used and have similar properties to ammonium aiginate, it is possible to obtain an excellent slip and carry out the slip casting process.

Triethylamine (C ₆ H ₁₅ N) is a liquid which is alkaline, has the taste of ammonia and which is an organic dispersant that can control the pH concentration of the slip up to above 12.

If triethylamine together with an organic protective colloid, such as. B. ammonium alginate. is used, it is possible to give the oxide powder, which has a low plasticity such as ferrite, an excellent one To impart slip density so that the slip casting process can be carried out easily can.

When pyridine, polyvinylamine, piperidine, tetra methyl ammonium hydroxide, ethylamine, propyl amine, amylamine and butylamine as organic!

Dispersants are used that have the same properties as triethylamine, it is possible borrowed to perform the slip casting process properly.

In addition 8 sheets of drawings

509 624 / 1C

Claims (1)

^ for the production of sintered " te »Fenit shape body pi, gefceito drawing dat-ch dfe Anwenihjng dö ScUifskergußverfah- -tens, but with the following conditions: the solids concentration in the suspension * is more than 50 ⁰ Ze _1, the grain diameter of the particles amounts to a maximum of 20 ^lx * μ, with at least S weight percent of the particles have a "Durchmesrser which is less than ¹ Z ₁₀ of the ^ g 0.0 £ and at most! Weight percent ^ water towels, more organic and few. or inorganic nKh