CN1204223C

CN1204223C - Nano-grade silicon nitride composite material heating body and its production process

Info

Publication number: CN1204223C
Application number: CN 01136305
Authority: CN
Inventors: 刘庆昌
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-10-09
Filing date: 2001-10-09
Publication date: 2005-06-01
Anticipated expiration: 2021-10-09
Also published as: CN1412268A

Abstract

The present invention relates to improvement to a silicon nitride heating body. Nanometer grade silicon nitride fine powder is adopted by the present invention, and common silicon nitride powder is added to reach a modified purpose. Aluminum nitride with expensive price is omitted in the components of a formula, and thereby, a high pressure and high temperature sintering process is converted into a normal pressure and high temperature sintering process. Not only can the cost of the silicon nitride heating body be greatly lowered, but also the quality of the silicon nitride heating body is enhanced. The silicon nitride heating body is favorable for being generalized and popularized. 45 to 82% of silicon nitride of 0.1 to 5 m um, and 14 to 40% of silicon nitride miropowder which is less than 100 nm grade are adopted in the formula, 0.1 to 5% of aluminum oxide and 3.9 to 10% of yttrium oxide additive are matched, and a satisfactory effect is obtained.

Description

Nano-grade silicon nitride composite material heating body and manufacture craft

Technical field

The present invention relates to the electricity is the heating element structure material prescription and the manufacture craft thereof of the energy, particularly with the situation of silicon nitride as the heating element base mateiral.

Technical background

Heating element is applied among the daily living article extremely at large, and powerful heating element also is widely used in industry heating, insulation and heating.The most general structure is to do the structure that the heating element outsourcing forms the combined type heating element with copper material behind the nichrome wire outsourcing insulating material, and this structure heating body is because residual a large amount of gases in the insulant, and the oxidation loss of high temperature resistance silk is serious and the life-span is too short.Even the very tight of insulation layer parcel also can't be solved fast, the flimsy disadvantage of oxidation, and the safety performance that works together is too poor.Used though there is the PTC ceramic heating element to make well heater in recent years, but still do not break away from the technological deficiency of life-span weak point, poor stability.99113534.2 number patent has been announced a kind of silicon nitride heat generating body and preparation method thereof.This heating element is sintered into one ceramic raw materials such as resistance wire and silicon nitride and additive and makes the direet-heating type heating element.Can say that this is one to heater structure design and breaks through greatly, because not only because the high temperature resistant and insulation characterisitic of silicon nitride itself is good, heat conduction is fast, makes indirect type heating element form become the direct type heating element.And because the secluding air source is improved its life-span greatly, safety performance is also improved thereupon.Yet this structure still can't be broken away from and remain in air residual in the sintered compact still there is residual threat in nichrome wire, and its heat conductivility is still not ideal enough, and the too expensive cost that causes of raw material as aluminium nitride raises in addition.It should be noted that especially this proportioning makes the sintering condition of silicon nitride in the complete processing must be at high pressure, high temperature compacted under.Its technological operation complexity, technology difficulty is big, the cost height be that production cost further improves, to such an extent as to have influence on this series products development, popularize.

Summary of the invention

The objective of the invention is further improvement to existing silicon oxide heating element prescription and technology, make it overcome current material cost height, the anti-dissatisfactory defective of loss of heat conduction sealing, make great efforts to make production technique to simplify,, help popularizing and using to reduce cost comprehensively.

Key of the present invention is to add the nano-grade silicon nitride modification and removes expensive aluminium nitride in the component of heating element.Nano-grade silicon nitride is meant the micro mist material of its granularity less than 100nm.Because its surface energy is strengthened, it is also easy that the intergranular contact area strengthens, grain boundary area is big, diffusion length is short, dissolving is separated out, so technological temperature and pressure when having reduced its sintering widely, and sintered density is improved, the quality of finished product obviously improves.Be again because nano-grade silicon nitride mostly is α-phase Si3N4.Theoretical analysis proves that the crystal grain increase of α-phase helps reducing sintering pressure, realizes normal pressure-sintered silicon nitride moulding, this shortage in prior art just.α-phase nano-grade silicon nitride micro mist add-on too conference causes the bad grasp of shrinkage, does not also meet relatively cheap principle.So the nano-grade silicon nitride that is added is to be no more than 40% for well, then effect is very unobvious very little for its quantity, on a small quantity should be more than 14%.The common silicon nitride powder granularity that is adopted also should could guarantee that the silicon nitride composite material of modification shows tangible performance advantage between 0.1-5 μ m.Common silicon nitride consumption between 45-82%, add modification nano-grade silicon nitride be 14-40%.By experiment the Al that adds 0.1-5% in the silicon nitride base-material of modification ₂O ₃Can improve highly dense sintering effect and good homogeneous grain-size more significantly and improve flexible intensity with the Y2O3 of 3.9-10%.The mean particle size of the aluminium sesquioxide that is added should be less than 5 μ m, and the mean particle size of yttrium oxide should be less than 6 μ m.

Take above component proportioning and tungsten filament to be sintered into one to make silicon nitride heat generating body to simplify operational process of craft greatly, realize low energy, low consumption, high-quality effect.

By the basic raw material that this component ratio range is made into, take following technology to make finished product:

1, the composition by weight by above-described raw material becomes the modification silicon nitride raw material than compatibility, raw material is inserted ethanol, the polyvinyl alcohol (or the two equal compound) that adds a small amount of (below 1%) in the high-strength plastic material container, and put silicon nitride or Al into ₂O ₃Abrading-ball carried out ball milling 3-40 hour, became batch mixing.

2, ball milling is good batch mixing charges in the drying baker of nitrogen, and the oven dry back is removed foreign material and formed base-material.

3, design the metal die of geometrical dimension by product requirement, base-material is inserted mould, simultaneously nichrome wire is pressed location, space geometry position, extrusion forming behind the matched moulds.

4, the moulding fetus is put into sintering oven, use Si ₃N ₄The powder that buries that+BN+MgO powder is formed buries it, after put into to heat up under the condition of stove inflated with nitrogen and be pressurized to 1900 ℃-2100 ℃, pressure 1-5Mp, constant temperature maintenance 1-3 hour.

5, stop to heat up, made it temperature in 60-120 minute after the release to reduce to 600 ℃-800 ℃.

6, after temperature was reduced to 150 ℃, depressurization took out product behind the naturally cooling.

Further specify below in conjunction with embodiment and the objective of the invention is how to realize.

Embodiment

(components by weight percentage) unit: %

Component	A	B	C	D	E	F	G	H
Component	A	B	C	D	E	F	G	H	Silicon nitride (0.1-0.35 μ m)	45	48	55	65	70	75	80	82
Nano-grade silicon nitride (less than 100nm)	40	38	32	23	19	16	15	14	Silicon nitride (0.1-0.35 μ m)	45	48	55	65	70	75	80	82
Nano-grade silicon nitride (less than 100nm)	40	38	32	23	19	16	15	14	Aluminium sesquioxide	5	4.5	4	3.5	3	2	1	0.1
Yttrium oxide	10	9.5	9	8.5	8	7	4	3.9	Aluminium sesquioxide	5	4.5	4	3.5	3	2	1	0.1

Embodiment 1:

Raw material is put into the ethanol or the poly-ethanol of the special-purpose high strength plastics container adding 0.5%-1% weight of ball mill in the ratio of the prescription A in the table 1, putting into abrading-ball (silicon nitride or alchlor material) back ground 3-40 hour, after putting into drying baker again and under nitrogen atmosphere, drying, insert metal die behind the sieve impurity elimination thing, in the matched moulds process tungsten filament is imbedded mixed resin by design requirements, with the pressing machine extrusion forming of 30-50 ton.Blank after the moulding is put into sintering oven and is buried back intensification pressurization under nitrogen atmosphere with burying powder.Concrete intensification pressure process is: be warming up to 1500 ℃-1600 ℃ in 30-60 minute, pressure is enlarged to 1-2Mp, keep being warming up to after 3-10 minute 1800 ℃-1900 ℃, pressure is enlarged under the 2-3Mp, kept 3-10 minute, be warming up to 1900 ℃-2100 ℃ again, pressure reaches 3-5Mp, keeps 1-3 hour.Stop then heating, make temperature drop to 60 ℃-800 ℃ in release 60-120 minute, after continuing then to be cooled to 150 ℃, natural ventilation, be cooled to normal temperature after finished product successfully come out of the stove.

Batch mixing bake out temperature in drying baker that ball milling is good can be controlled in 180 ℃-300 ℃, and pressing machine is that 30-50 ton press is plastic during pressurization.The used proportioning component that buries powder is (ratio of weight and number):

Sl ₃N ₄4-6 part

BN 3-5 part

1 part of MgO

Embodiment 2-8 can be according to prescription B-G formulation ratio raw material, and becomes product with reference to the processes of embodiment 1.

By the heating element that above proportioning raw material complete processing processes, heat-up rate is fast, and strength high toughness is good, and the life-span improves significantly, and because normal pressure-sintered cost declines to a great extent, becomes a kind of desirable heating element that universal prospect is arranged.

Claims

1, a kind of silicon nitride heat generating body, it is characterized in that by drawing lead, the nichrome wire that is connected with lead and forming with the silicon nitride composite material body that nichrome wire is sintered into one the component proportioning of body is (weight percent):

The silicon nitride granularity accounts for 45-82% at 0.1-5 μ m,

Granularity accounts for 14-40% less than 100nm,

Aluminium sesquioxide accounts for 0.1-5%,

Yttrium oxide accounts for 3.9-10%,

2,, it is characterized in that said nichrome wire is a tungsten filament according to the said silicon nitride heat generating body of claim 1.

3, according to the said silicon nitride heat generating body of claim 1, it is characterized in that said aluminium sesquioxide mean particle size should be less than 5 μ m, the yttrium oxide mean particle size is less than 6 μ m.

4, the manufacture craft of silicon nitride heat generating body is characterized in that this technology is by following process operations:

(1) by the said component ratio preparation raw material of claim 1, raw material is inserted in the high strength plastics container, add a spot of (below 1%) ethanol or polyvinyl alcohol and put silicon nitride into or the aluminium sesquioxide abrading-ball, ball milling 3-40 hour,

(2) batch mixing that ball milling is good is inserted drying baker charging under the nitrogen situation, and screen out foreign material after the oven dry and make base-material,

(3) carry out by the geometrical dimension of product design and will sieve the back base-material behind the metal die and insert, simultaneously nichrome wire press the space geometry position and located, extrusion forming behind the matched moulds,

(4) the moulding fetus is put into sintering oven, use Si ₃N ₄Burying that+BN+MgO forms put into stove after powder buries, and heat up under the condition of inflated with nitrogen and be pressurized to 1900 ℃-2100 ℃, pressure 1-5Mp, constant temperature kept 1-3 hour,

(5) stop to heat and release, make it temperature in 60-120 minute and reduce to 60 ℃-800 ℃,

Open fire door when (6) temperature is reduced to 150 ℃, naturally cooling becomes product.

5, according to the said silicon nitride heat generating body manufacture craft of claim 4, it is characterized in that the temperature in drying baker is 180 ℃-300 ℃, the metal die pressurization is the 30-50 ton with pressing machine.

6,, it is characterized in that burying the component proportioning (ratio of weight and number) of powder according to the said silicon nitride heat generating body manufacture craft of claim 4:

Si ₃N ₄: BN: MgO is 4-6: 3-5: 1.

7, according to the said silicon nitride heat generating body manufacture craft of claim 4, it is characterized in that heating up in the pressure sintering process, in 30-60 minute temperature is risen to 1500 ℃-1600 ℃, pressure adds to 1-2Mp, keeps 3-10 minute, continue to be warming up to 1800 ℃-1900 ℃, pressure adds to 2-3Mp, keeps 3-10 minute, is warming up to 1900 ℃-2100 ℃ again, pressure reaches 3-5Mp, keeps 1-3 hour.