Patent Application: US-201414212666-A

Abstract:
liquid anti - oxidants made by mixing specific chemical compositions disclosed herein , followed by thorough stirring so that a homogeneous blend of colloidal - like solutions are obtained . such liquid anti - oxidants are applied to the surface of the carbon - carbon composite that is needed to be protected against oxidation by brushing , dipping , spraying , or other painting techniques , and allowed sufficient time for the anti - oxidants to penetrate into the subsurface region of the composite and to let dry in a dry atmosphere . the coated carbon / carbon composites can be heat treated at a temperature of about approximately 650 to 950 ° c . for a time period of about approximately one to seven hours . the above painting / heat treating processes can be repeated one to three or more times in order to obtain sufficient anti - oxidant char on or below the surface to a certain depth of the composite .

Description:
according to the embodiment ( s ) of the present invention , various views are illustrated in fig1 - 4 and like reference numerals are being used consistently throughout to refer to like and corresponding parts of the invention for all of the various views and figures of the drawing . also , please note that the first digit ( s ) of the reference number for a given item or part of the invention should correspond to the fig . number in which the item or part is first identified . one embodiment of the present technology comprising glass - ceramics based anti - oxidant teaches a novel apparatus and method for treating surfaces for oxidation protection . the details of the invention and various embodiments can be better understood by referring to the figures of the drawing . referring to the figures , a commercial c / c composite was used to test and develop the anti - oxidants disclosed and claimed herein . the composite is made of a 3 - dimensional non - woven fiber architecture which is infiltrated with pyrolytic chemical vapor deposition ( cvd ) carbon matrix material . the density of the composite ranges from 1 . 6 to 1 . 8 g / cm 3 . sample disks of 2 inches in diameter and 1 inch thick cut from as - received brake discs were used for oxidation testing . the design of the anti - oxidants was based on mixing appropriate percentages of glass formers , glass network modifiers , and glass intermediates that were derived from a variety of raw materials after char heat treatments . an anti - oxidant that has been applied to the c / c composite sample can be heat treated or “ charred ” to form a stable glass and crystalline ceramics mixture of coating material . this char process can take place in a controlled nitrogen atmosphere within a furnace heated to approximately 700 ° c . to 900 ° c . this elevated temperature allows for the release of solvent and chemically bonded water , along with other volatile species , from the liquid anti - oxidant mixture and yields a solid char coating . thermal oxidation tests were performed at isothermal temperatures of 650 ° c . and 871 ° c . the two common runway deicers and anti - icing agents that were tested are potassium acetate and calcium chloride . once the 2 inch by 1 inch thick c / c samples have been coated on all surfaces and charred with three char cycles , the samples were then exposed to the catalyst . the samples were completely submerged in the catalyst solution for a total of 30 minutes to allow for proper penetration into the samples surfaces . catalytic oxidation testing was only conducted at an isothermal temperature of 650 ° c . and an atmospheric air flow rate of 5 standard liters per minute ( slpm ). potassium acetate catalyst was applied to the samples by soaking in a catalyst solution of 75 weight percent water and 25 weight percent potassium acetate at 25 ° c . separate testing with calcium chloride was performed by soaking the coated samples in a catalyst solution with 50 weight percent water and 50 weight percent calcium chloride at 50 ° c . after catalysts soaking , samples are dried in an oven at 80 ° c . for at least 8 hours to ensure proper drying of the catalyst in the samples . the char yield of the anti - oxidant is critical to the design for any antioxidant system . following heat treatment process at 900 ° c ., solid that is produced from the liquid anti - oxidants is a mixture of oxide materials known as char . the composition of the char in terms of the percentages of oxides can be calculated theoretically . generally , theoretical char yields and experimental char yields are shown to have significant agreement to within one or two weight percentage points . the individual char compositions of each oxide forming group by weight are 30 - 75 wt % p 2 o 5 , 3 - 25 wt % al 2 o 3 , 0 - 20 wt % k 2 o , 0 - 20 wt % na 2 o , 0 - 20 wt % cao , 0 - 20 % mgo , 0 - 10 wt % sio 2 , and 2 - 25 wt % b 2 o 3 . this composition range was used throughout the design of the antioxidant systems covered in this invention . anti - oxidants can be defined by their individual source chemical formulations or the individual oxide char material content after heat treatment . the oxide char materials which can be produced by a variety of raw chemicals are described by the chemical reactions listed below : in equation 1 , the phosphoric acid ( h3po4 ) brakes down during heat treatment . as a result of the reaction , water ( h2o ) is formed and released , and solid phosphorus oxide ( p2o5 ) remains as a char yield . char yields of each chemical can then be integrated into mixing formulations to produce a total char yield and the associated weight loss for any anti - oxidant solution . for examples , source materials from equation 1 , equation 2 , equation 4 , and equation 11 are possible sources of phosphorus oxide char material after the heat treatment process . source materials from equation 2 and equation 3 are possible sources of aluminum oxide char material . source materials from equations 4 through 8 are possible sources of potassium oxide char material . source materials from equations 10 through 14 are possible sources of sodium oxide char material . source materials from equation 8 through 10 are possible sources of boron oxide char material . source materials from equation 15 and equation 16 are possible sources of calcium oxide char material . after heat treatments , volatiles are released while only stable oxides remain in the final product and react to form a stable mixture of glass - ceramic coating material . the theoretical calculations of weight loss and char yields for each could be used to calculate the amount of source materials needed to design the particular anti - oxidant . the weight percent of each oxide material can be achieved by using many possible source materials as shown in table 2 . column one in this table contains many possible raw chemicals that can be used in the making of the anti - oxidant material and column two contains the possible ranges of each raw material used in this anti - oxidant . the last eight columns represent the percent of each oxide material after the raw material has been charred at elevated temperatures to remove all volatile materials . the volatile materials given off during a char cycle may include water , carbon dioxide , and chlorine gas . the last row in table 2 represents the range of the total percent weight of each oxide in the anti - oxidants disclosed in this invention . the design of anti - oxidants outlined in table 2 is based on a char composition approach . the weight percentages of glass formers , glass network modifiers , and glass intermediates in the anti - oxidant were calculated using weight percent chars of each oxide material yielded from raw chemicals during the char process . the anti - oxidants can be produced either by directly mixing the oxides specified in the last row of table 2 with proper amounts of de - ionized water , or by mixing the raw chemicals specified in columns 1 and 2 in table 3 for yielding the desired oxide chars upon heat treating . after mixing liquid anti - oxidants , fine solid particles are usually present . this is because the amounts of solids and salts used in the formulation are much greater than their solubility limits in the phosphoric acid based liquid . dispersion of these solid particles is helpful to the penetration of the anti - oxidants into cc composites in order for the anti - oxidants to facilitate superior oxidation protection . in order to disperse the solid particles in the liquid anti - oxidants , two methods are used : ( 1 ) adding small amounts , up to 1 % by weight , of surfactants , and / or ( 2 ) blending with high speed , high shear colloidal grinder / mill . examples of surfactants are df - 16 , df - 20 , and cf - 10 supplied by dow chemical company , and silicone surfactants supplied by byk additives and instruments . dow chemical &# 39 ; s df and cf series of surfactants are composed of alcohols , c8 - c10 , ethoxylated propoxylated , and poly ( ethylene oxide ). the silicone surfactants for aqueous solutions supplied by byk additives and instruments , e . g ., byk 346 , are basically a solution of a polyether modified dimethylpolysiloxane in solvents of dipropyleneglycol monomethylether . there are a large number of commercial colloidal grinder / mills that are suitable for mixing and dispersing solid particles in anti - oxidants . the working principle of the colloidal mill is that under the effect of centrifugal force and being run by relatively high speed between the rotating gear and the fixed gear , the liquid and the semi - liquid materials is efficiently emulsified , homogenized , dispersed and mixed during the course of being cut , milled and shocked with high frequency . after colloidal mixing , the anti - oxidant product is extremely well - dispersed . one series of anti - oxidants , designated as sp4c1 through 16 , was designed using the char composition ranges described in table 2 above . considering the anti - oxidant of sp4c1 as an example , as shown in table 3 below , the designed char composition of sp4c1 is p205 33 . 88 %, al2o3 4 . 52 %, k20 2 . 74 %, and b203 2 . 41 % by weights on a basis of 43 . 55 % overall char yield . the anti - oxidant of sp4c - 1 can be produced by mixing the above oxides directly with proper amounts of deionized water , or by mixing the raw chemicals listed in columns 1 and 2 in table 3 . as another example , the anti - oxidant of sp4c5 , as shown in table 4 , can be made by mixing 33 . 88 % of p205 , 4 . 52 % of al203 , 2 . 74 % of k20 , and 2 . 41 % of b203 by weights on a basis of 44 . 04 % overall char yield with proper amount of deionized water . or , alternatively , the anti - oxidant can also be made by mixing the raw chemicals listed in columns 1 and 2 in table 4 . another example is given in table 5 below . the anti - oxidant of sp4c11 can be made by mixing 31 . 98 % of p205 , 4 . 97 % of al2o3 , 2 . 79 % of k20 , and 2 . 92 % of b2o3 by weights on a basis of 42 . 67 % overall char yield with proper amount of deionized water . or , alternatively , the anti - oxidant can also be made by mixing the raw chemicals listed in columns 1 and 2 in table 5 . experimental results from the 650 ° c . oxidation tests of cc samples coated with anti - oxidants sp4c1 through 15 are shown in fig1 . two commercial materials , designated as “ p38 commercial ” and “ bfg patent ”, are also plotted in the figure for comparison with the sp4c series of anti - oxidants . the oxidation weight losses of cc coated with these commercial materials are greater than 3 % after 25 hours of oxidation at 650 ° c . comparing with the sp4c series of anti - oxidants , it is found that the sp4c series of materials are far better than the commercial materials ; with the best oxidation time for 3 % weight loss as high as 130 hours ( sp4c - c ). another series of anti - oxidants , designated as sp4c3 - 1 through 12 , was also designed using the char composition ranges described in table 2 above . considering the anti - oxidant of sp4c3 - 1 as an example , as shown in table 6 below , the designed char composition of sp4c1 is p205 35 . 68 %, al2o3 3 . 53 %, k20 4 . 14 %, and b203 3 . 48 % by weights on a basis of 46 . 84 % overall char yield . this anti - oxidant can be produced by mixing the above oxides directly with proper amount of de - ionized water . or , alternatively , the anti - oxidant can also be made by mixing the raw chemicals listed in columns 1 and 2 in table 6 . another example is given in table 7 . the anti - oxidant of sp4c3 - 5 can be made by directly mixing 35 . 50 % of p205 , 3 . 51 % of al203 , 4 . 84 % of k20 , and 2 . 93 % of b203 by weights on a basis of 46 . 78 % overall char yield with proper amount of deionized water . or , alternatively , the anti - oxidant can also be made by mixing the raw chemicals listed in columns 1 and 2 in table 7 . another example is given in table 7 . the anti - oxidant of sp4c3 - 5 can be made by directly mixing 33 . 01 % of p205 , 4 . 24 % of al2o3 , 4 . 08 % of k20 , and 3 . 95 % of b203 by weights on a basis of 45 . 27 % overall char yield with proper amount of deionized water . or , alternatively , the anti - oxidant can also be made by mixing the raw chemicals listed in columns 1 and 2 in table 7 . experimental results from the 650 ° c . oxidation tests of cc samples coated with anti - oxidants sp4c3 - 1 through 12 are shown in fig2 . two groups of commercial materials , designated as “ p38 commercial ” and “ bfg patent ”, are also plotted in the figure for comparison with the sp4c3 series of anti - oxidants . the oxidation weight losses of cc coated with these commercial materials are greater than 3 % after 25 hours of oxidation at 650 ° c . comparing with the sp4c3 series of anti - oxidants , it is found that the sp4c3 series of materials are far better than the commercial materials ; with the best oxidation time for 3 % weight loss as high as 130 hours ( sp4c - c ). the performance of sp4c3 series of anti - oxidants are also evaluated with 871 ° c . ( 1600 ° f .) oxidation tests . the results of sp4c3 - 1 through 12 tests are shown in fig3 . one commercial material , designated as “ p38 commercial ”, is also plotted in the figure for comparison with the sp4c3 series of anti - oxidants . the oxidation weight loss of cc coated with this commercial material is greater than 3 % after 2 hours of oxidation at 871 ° c . comparing with the sp4c3 series of anti - oxidants , it is found that the sp4c3 series of materials are far better than the commercial materials ; with the best oxidation time for 3 % weight loss well in excess of 20 hours ( sp4c3 - 4 ). catalytic oxidation tests at 650 ° c . with potassium formate were conducted to evaluate the catalytic oxidation protection of the anti - oxidants of this invention . fig4 compares commercially available antioxidants ( p38 and p39 ) to the sp4c anti - oxidants when exposed to potassium formate catalyst . commercially available p38 and p39 materials have substantially worse catalytic oxidation protection when compared to the sp4c - based anti - oxidants . the results show that sp4c - corner observed two percent weight loss in 75 hours at 650 ° c . where p38 material observed two percent weight loss in 10 hours at 650 ° c . the sp4c series anti - oxidants have proved to be more resistant to catalytic oxidation than commercially available materials . the various glass - ceramics based antioxidant examples shown above illustrate a novel oxidation protection . a user of the present technology may choose any of the above implementation , or an equivalent thereof , depending upon the desired application . in this regard , it is recognized that various forms of the subject technology could be utilized without departing from the spirit and scope of the present invention . as is evident from the foregoing description , certain aspects of the present invention are not limited by the particular details of the examples illustrated herein , and it is therefore contemplated that other modifications and applications , or equivalents thereof , will occur to those skilled in the art . it is accordingly intended that the claims shall cover all such modifications and applications that do not depart from the sprit and scope of the present invention . tatarzicki , y ., webb , r ., 1992 , “ friction and wear of aircraft brakes ,” asm handbook , vol . 18 , pp . 582 - 587 . blau , p ., 2001 , “ compositions , functions , and testing of friction brake materials and their additives ,” ornl / tm - 2001 / 64 , metals and ceramic division , oak ridge , tenn . mcallister , l ., 1989 , “ barrier coating and penetrant providing oxidation protection for carbon - carbon materials ” u . s . pat . no . 4 , 837 , 073 . barmak , k ., 1939 , “ reaction kinetics in progresses of nucleation and growth ,” vol . 135 , pp . 416 & amp ; 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