Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Reexamination Certificate
2000-05-04
2002-12-24
Group, Karl (Department: 1255)
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
C501S015000, C501S017000, C501S018000, C501S032000, C501S061000, C501S062000, C501S075000, C501S076000
Reexamination Certificate
active
06498116
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to localized thermal processing of glazed ceramics and other brittle and low thermal conductivity materials. More particularly, this invention relates to coating and filler materials for use in such processing, the coating materials having coefficients of thermal expansion of less than about 8×10
−6
/° C. and glass transition temperatures of less than about 400° C., and the filler materials having coefficients of thermal expansion of about 0.5×10
−6
/° C.
BACKGROUND OF THE INVENTION
Vitreous coating materials, commonly referred to as glazes or enamels, are used on many ceramics and other brittle and low thermal conductivity materials for aesthetic and functional purposes. Ceramic whitewares are coated with glazes for decorative and sanitary purposes. Conductive glazes are used on ceramic electrical insulators to remove charges. Glazes are also used in ceramic electronic packages for hermetic sealing and bonding. Enameled cast iron is coated with porcelain enamels for decorative and functional purposes.
Glazed ceramic manufacturing processes often yield a certain percentage of product that have surface defects. These defects can detract from the appearance of the article and create functional problems that render the article unusable. Consequently, methods have been developed for repairing certain types of surface defects in glazed ceramics. One such repair method involves enlarging the hole by drilling, filling the hole with a glaze material similar to the original, and re-firing the entire part at maximum temperatures near 1200° C. for many hours. Unfortunately, new flaws may initiate at secondary sites during re-firing, thus, frustrating the repair efforts. Moreover, this method is expensive, energy intensive, and time consuming.
Another repair method considered for use in repairing glazed ceramics is laser welding. Laser welding methods typically employ a carbon dioxide (CO
2
) laser operating at a wavelength of 10.6 &mgr;m. Such lasers are used because they are stable and capable of delivering high, readily absorbed output power such that temperatures of 1800° C.-1900° C. over a few square millimeter area can be rapidly achieved to fuse refractory materials within a few seconds. The rapid heating can also produce undesirable cracking within and near the irradiated region due to the brittle and low thermal conductive nature of ceramics which permit high thermal gradients and high stresses to develop.
Laser induced thermal stress problems have been addressed in U.S. Pat. No. 5,427,825 which discloses a method for localized glazing of ceramics that maintains a non-destructive level of thermal stresses within the irradiated region by appropriate control of the laser's energy. This is accomplished by applying a fusing radiant energy to a fusion zone on the surface of the glazed ceramic article and annealing the fusion zone by applying annealing radiant energy to an annealing zone on the surface of the article which encompasses the fusion zone. The annealing radiant energy limits the thermal stress to a level during cooling which is less than the fracturing stress of the ceramic material, so that cooling can be accomplished without inducing cracks in the surface.
The glazes coating the ceramics described in U.S. Pat. No. 5,427,825 typically have melting temperatures near 1200° C., and coefficients of thermal expansion of 6-7×10
−6
/° C. The engineering of these two parameters has been found to be critical in laser fusion performance, particularly in laser sealing of vitreous coatings over brittle substrates. The high melting temperature requires the absorption of considerable energy to fuse the coating to the substrate. Consequently, the non-destructively high thermal gradients and the thermal expansions in the range noted, can still increase thermally-induced strains beyond critical limits, thus resulting in permanent damage to the coating and the substrate.
Accordingly, coating materials are needed which have coefficients of thermal expansion and glass transition temperatures sufficiently lowered to a point where the strain induced by a rapid change in temperature during localized thermal processing, remains below the elastic strain limit. There is also a need for filler materials that can be used for repairing deep defects via localized thermal processing.
SUMMARY OF THE INVENTION
The present invention relates to coating and filler materials for localized thermal processing of glazed ceramics and other brittle and low thermal conductivity materials. The coating materials comprise oxide compositions that exhibit coefficients of thermal expansion which are less than about 8×10
−6
/° C. and glass transition temperatures which are less than about 400° C. The filler materials comprise particulate oxide materials which do not substantially react during localized thermal processing of glazed ceramics and other brittle and low thermal conductivity materials.
The coating and filler materials are useable together as a composite material for repairing cavities having depths greater than about 2 mm.
REFERENCES:
patent: 3848104 (1974-11-01), Locke
patent: 4135038 (1979-01-01), Takami et al.
patent: 4369348 (1983-01-01), Stetson et al.
patent: 4405722 (1983-09-01), Kokubu et al.
patent: 4420569 (1983-12-01), Tick
patent: 4562332 (1985-12-01), Walter et al.
patent: 4710479 (1987-12-01), Yamanaka et al.
patent: 4996172 (1991-02-01), Beall et al.
patent: 5071795 (1991-12-01), Beall et al.
patent: 5075261 (1991-12-01), Yamanaka
patent: 5089446 (1992-02-01), Cornelius et al.
patent: 5122484 (1992-06-01), Beall et al.
patent: 5266094 (1993-11-01), Johansson et al.
patent: 5328874 (1994-07-01), Beall et al.
patent: 5330940 (1994-07-01), Aitken et al.
patent: 5393482 (1995-02-01), Benda et al.
patent: 5427825 (1995-06-01), Murnick
patent: 5468694 (1995-11-01), Taguchi et al.
patent: 5508489 (1996-04-01), Benda et al.
patent: 5510300 (1996-04-01), Lim et al.
patent: 5514360 (1996-05-01), Sleight et al.
patent: 5529960 (1996-06-01), Aitken et al.
patent: 5529961 (1996-06-01), Aitken et al.
patent: 5564272 (1996-10-01), Warner et al.
patent: 5595583 (1997-01-01), Murnick
patent: 5733828 (1998-03-01), Usui et al.
patent: 5762675 (1998-06-01), Malmqvist et al.
patent: 5916832 (1999-06-01), Tanabe et al.
patent: 5919720 (1999-07-01), Sleight et al.
patent: 5976999 (1999-11-01), Evans et al.
patent: 6183716 (2001-02-01), Sleight et al.
patent: 6187700 (2001-02-01), Merkel
Colaizzi James
Lehman Richard Long
Li Jie
Murnick Daniel Ely
Umezu Yuya
Duane Morris LLP
Group Karl
Rutgers, the State University
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