CVD law produces the BCl₃ in boracic fiber process reclaim the research of recycle

Preface of Recycling1 of 　 of Boron Trichloride of 　 of Keywords 　 Boron Fiber is in process of production of CVD boracic fiber, utilization rate of raw material BCl3 has 20% only normally, and the BCl3 of the others is regarded as waste gas to eliminate reative cell. If do not adopt any reclaiming measure, produce place of 1kg boracic fiber to need BCl3 to will be as high as 75kg, only this raw material will be occupied go the 2/3 of cost of boracic fiber production. This shows, reclaim recycle reative cell eliminates the BCl3 in tail gas, reduce boracic fibrous to produce cost substantially, drive the development of boracic composite material and project application will advantageously. 2 experiments process and result are analysed 2.

The low temperature of 1 　 BCl3 reclaims the boracic fiber that takes B4C coat is connect the gas mixture of H2 and BCl3 two boracic reative cell respectively, the boracic deposit that displacement gives heats in resistor the diameter is made an appointment with 12.

On the silk end the tungsten of 7 μ M, form boracic fiber. Besmearing Fu is indoor, the odd gas that uses the 2nd boracic deposit room and new the firedamp that introduce (CH4) gas, coating of B4C of the deposit on the boracic fiber that continues to heating, form the boracic fiber that takes B4C coat finally. To pure BCl3, its boiling point is 12.

4 ℃ , use glacial water to be able to become BCl3 gas condensation the liquid normally. However, the gas after reaction is wait for the gas mixture that make by BCl3, H2 and resultant HCl. To the aleatoric constituent of gas mixture, because the cent of this gas constituent is pressed,drop, condensing temperature also will be reduced subsequently, polarity element HCl is contained in gas mixture especially, the condensation of BCl3 becomes more difficult, must be in that is to say far fall under the temperature of BCl3 boiling point, the BCl3 in the waste gas after ability will react possibly departs and condensation reclaims. The mechanical refrigeration form that this experiment chooses 3 foreign companies of Japanese to produce ark serves as MDF-2136 ultralow temperature reclaim the microtherm source of 3 chloridize boron, temperature of job of this equipment lowest can be amounted to - 135 ℃ , among them - 80 ～ - Duan Ke carries out the temperature of 135 ℃ to accuse automatically lukewarm. Because working space is large, can run for long continuously wait for a characteristic, this equipment special the low temperature that applies to the BCl3 when batch produces boracic fiber reclaims. As a result of CH4 of besmear Fu room introduce, the gas after reaction may contain other product, make reclaim the problem becomes complex, the BCl3 quantity of besmear Fu room is very few, accordingly, this experiment reclaims only the BCl3 in tail gas of boracic deposit room, reclaim temperature is - 80 ℃ . 2.

When the BCl3 after the analysis of the 2 BCl3 after reclaiming reclaims is contacted with air below normal temperature, still have the taste of a kind of disgust besides producing spontaneous combustion phenomenon. When using its deposit boracic fiber, start hard, although start, the fiber strength that deposit gives is extremely weak also. Via gas phase infra-red and spectral analysis makes clear, primitive BCl3 spectral line has the BCl3 that contains spontaneous combustion material and deposit boracic fibrous to differ apparently, refer to a graph 1 with the graph 2. Graph the gas phase of the 1 BCl3 that contains spontaneous combustion material is infra-red and spectral Fig.

1 　 IR Spectrum Of BCl3 Including Pyrophorus pursues the gas phase of 2 primitive BCl3 is infra-red and spectral Fig.

Because 　 of 2 　 IR Spectrum Of Primary BCl3 is deposit introduce when boracic fiber have BCl3 and H2 only two kinds of gas, because this divides HCl of normal reaction resultant (in - 80 ℃ reclaim below temperature, boiling point is - the HCl of 85 ℃ collects no less than coming) outside, certainly still a kind of boiling point can produce the material of spontaneous combustion phenomenon higher, utmost of this kind of material is boracic hydrogen compound (boracic alkyl of a general designation) . According to data introduction boracic alkyl series has [1] : Aeriform B2H6, liquid B4H10, B5H9, B5H11, B6H10, solid B10H14. Among them Yi Peng alkyl (B2H6) in air not spontaneous combustion, and because boiling point is inferior (- 92.

5 ℃ ) , in - 80 ℃ reclaim the liquid won't become below temperature and in interfuse BCl3, reason eliminates the possibility that B2H6 exists. Fourth boracic alkyl (B4H10) boiling point is 18 ℃ , approach the boiling point at BCl3 very much (12.

4 ℃ ) , it is a kind of volatile liquid, its steam can be in air spontaneous combustion, have the taste of disgust. According to these character, can decide spontaneous combustion of air of the contact below the BCl3 normal temperature after reclaiming may be to contain B4H10 be caused by. Come to compare B4H10 element to measure bigger boracic alkyl at whether can still having, because lack the data of this kind of boracic alkyl,still conclude hard. But the addition that measures along with the element according to the boiling point of boracic alkyl and elevatory character, can decide the BCl3 after reclaiming is contacting open fight between factions with air below normal temperature is not from this kind boracic alkyl is caused. It is in order to stand by the B5H9 of B4H10 now exemple, its boiling point already lifted 64.

8 ℃ , although reclaim,the BCl3 after contains B5H9, also won't become vapour below normal temperature. 2.

3 fourth boracic alkyl (B4H10) the B4H10 in the BCl3 after purify reclaims, its boiling point (18 ℃ ) the boiling point with BCl3 (12.

4 ℃ ) very adjacent, depart very hard with common method, especially B4H10 noxiousness is big, contact air spontaneous combustion, bring a lot of inconvenience to the operation. Because how is this found,eliminate B4H10 safely, handily to become crucial place. According to document [1] introduce, normally cent is boracic alkyl stability (BnHn+4) and flabby finalize the design (BnHn+6) two kinds, among them B2H6 is stability model, b4H10 is not stable model. B4H10 is putting the simplest B2H6 in the itself in letting off Cheng can be decomposed gradually and making boracic hydrogen compound, the chemical character that B2H6 of this that is to say has also is the chemical character of B4H10 likewise. Accordingly, we but have the aid of the concerned chemistry knowledge at B2H6, depart B4H10 from inside BCl3 and eliminate. A chemical character of B2H6 can produce severe reaction with Cl2 namely, generate BCl3 and HCl, its chemistry equation is: B2H6+6Cl2 → 2BCl3+6HCl also should produce following reaction with manage B4H10 and Cl2: 　 of B4H10+11Cl2 → 4BCl3+10HCl reacts resultant is the material that we need, and HCl because boiling point (- 85 ℃ ) low, the water that use ice won't condensation. Because this uses this law eliminate,B4H10 should be a kind of better method. Graph 3 it is the unit plan that eliminates B4H10 through coming with Cl2 reaction, connect the BCl3 that contains B4H10 by flowmeter pilot and Cl2 reative cell respectively, bottle of amortize of classics of the gas after reaction enters condenser, be collected into BCl3 by glacial water condensation finally inside Yu Gang bottle. Graph the device 1 Cl2 that reaction of 3 　 Cl2 eliminates B4H10; 2 H2SO4; 3 amortize bottle; 4 reclaiming BCl3; Bath of water of 5 constant temperature; 6 flowmeter; 7 reative cell; 8 amortize bottle; 9 filter ball; Condenser of 10 ice water; 11 receive bottle; Fig of 12 ice cube. The discharge size of the BCl3 that 　 of 3 　 The Apparatus Of Eliminating B4H10 With Cl2 shares reaction and Cl2 is not invariable, the principle that follow is: Be in above all given below BCl3 circumstance, need to adjust accordingly only Cl2 discharge, the gas after making react does not produce spontaneous combustion phenomenon; Contain the Cl2 of excessive to prevent to handle the BCl3 after next, in ensure the gas after reaction not below the premise of spontaneous combustion, should control Cl2 discharge to come as far as possible the smallest. Can figure according to corporeal structural formula the liquid density that gives B4H10 uprights at B2H6 (0.

47g/cm3) with BCl3(1.

Between 43g/cm3) , the B4H10 in the BCl3 after reclaiming namely is to be in BCl3 fluid face to go up actually, once BCl3 is mixed,accordingly Cl2 does not react in mixing chamber (not calorific) , make clear to B4H10 already was contained no longer in the rest BCl3, cl2 processing stops. the BCl3 that after Cl2 reacts, collects and the rest 3 chloridize boron undertakes rectification is handled, via gas phase infra-red spectrum is analysed, get the spectral line that agrees with primitive BCl3, if pursue,4 are shown. With its deposit takes the boracic fiber of carbonization boracic coating, function is normal, among them tensile strength is high person can amount to 3600MPa. Graph the gas phase of BCl3 rectify makings that Cl2 of the 4 courses after reclaiming handles is infra-red and spectral Fig. 　 of conclusion of 4 　 IR Spectrum Of Rectifying BCl3 Treatedwith Cl2 After Retrieval3 (serial production takes 1) in process of B4C coating boracic fiber, because fourth boracic alkyl is contained in BCl3,the BCl3 after reclaiming and air contact produce spontaneous combustion phenomenon is (B4H10) be caused by. (2) adopts the method that reacts with Cl2 and B4H10, solved the spontaneous combustion problem of the BCl3 after reclaiming, after classics rectify extract, when using its deposit boracic fiber, with primitive BCl3 deposit fiber function agrees, among them tensile strength is high person can amount to 3600MPa. CNC Milling CNC Machining