102 results about "Spontaneous nucleation" patented technology

The invention relates to the field of directional solidification of alloys, particularly relates to a method for preventing monocrystal blades from having mixed crystal defects. The method is characterized in that in the process of preparing an investment casting mould case for monocrystal blade production, a ceramic fiber insulation block is implanted into the position on a mould case at a blademargin plate at which is easy to have mixed crystal defects, the ceramic fiber insulation block is prefabricated into a U-shaped block according to the shape of the mould case at the blade margin plate, and a U-shaped cavity of the ceramic fiber insulation block contains all mould cases at the blade margin plate. The method disclosed by the invention has the advantages that through using the characteristics that the thermal conductivity of the ceramic fiber insulation block is extremely low, the liquidus temperature TL-isotherm form (see Figure 2) generated when a solidification front reachesthe monocrystal blade margin plate in the process of alloy solidification at the monocrystal blade margin plate is controlled reasonably, so that when the margin plate is close to a directional solidification thermal baffle plate area, the heats are mainly outputted by a monocrystal blade body, and the spontaneous nucleation at the margin plate is avoided, thereby ensuring the smooth growth of monocrystals.

The invention discloses a horizontal growth device and growth method of a phosphorus silicon cadmium mono-crystal, belonging to the technical field of phosphorus silicon cadmium mono-crystal preparation. The device comprises an outer layer quartz tube, an inner layer quartz tube sleeved in the outer layer quartz tube, and a PBN boat-shaped crucible sleeved in the inner layer quartz tube, wherein the PBN boat-shaped crucible comprises a crystal nucleus growth section, a transition section and a mono-crystal growth section which are connected with one another in sequence; a first end part of the crystal nucleus growth section is set to be spire-shaped so as to improve the uniformity of crystal orientation in spontaneous nucleation. By virtue of the design of a double-layer quartz tube, inert gas is introduced between the quartz tubes, so that the problems of tube explosion extremely easily generated in the crystal growth process can be solved, and the stability of a thermal field and the durability of the growth device can be improved. The method is used for preparing the phosphorus silicon cadmium mono-crystal on a horizontal crystal growth furnace with the growth device by using a horizontal gradient freezing method so as to ensure a more stable crystallization process and reduce the defects of parasitic nucleation; the method is beneficial for obtaining a CSP mono-crystal with good mono-crystal performance and complete crystal lattice, and is simple in operation, easy in control and low in cost.

The invention provides a ternary boride metal-ceramic Mo2FeB2 alloy powder block for build-up welding. The ternary boride metal-ceramic Mo2FeB2 alloy powder block is prepared from the following raw materials in parts by weight: 20-38 parts of iron boron, 32-50 parts of molybdenum powder, 7-24 parts of iron powder, 2-4 parts of nano-titanium carbide powder and 2-4 parts of yttrium oxide powder. When the iron boron, the molybdenum powder and the iron powder are used as raw materials for carrying out a metallurgical reaction so as to synthesize Mo2FeB2, an appropriate amount of the nano-titaniumcarbide powder is added; in a process of welding metallurgy, since the melting point of the nano-titanium carbide powder is as high as 3140 DEG C, the nano-titanium carbide powder can be used as a dispersed Mo2FeB2 non-spontaneous nucleation core in liquid metal, and the formed ternary boride Mo2FeB2 is enabled to be distributed in a dispersed way; therefore, the build-up welding metal has excellent high temperature hardness, wear resistance as well as good toughness and crack resistance. The steps are simple, the operation is convenient, and the practicality is high.

The invention belongs to the technical field of chemical control and detection, and particularly relates to a method of regulating isotactic polypropylene (iPP) crystallization behavior and crystal structure. The invention is characterized in that a parallel-plate rheometer is used as a tool, and the crystal structure of polypropylene is regulated by the spontaneous nucleation characteristic of semi-crystalline polymer. The spontaneous nucleation temperature is regulated by precise temperature control of the rheometer so as to obtain isotactic polypropylene with various crystal structures. The method can not only prepare samples for performance tests, but also monitor the crystallization process of isotactic polypropylene, and realize on-line observation of the spontaneous nucleation effect. The method has the advantages of simple operations, precise regulation, and the like, and has wide application prospects in the fields of fine chemical industry and the like.

The invention relates to a method for preparing a REBa2Cu3Ox (REBCO) high-temperature superconducting block material, in particular to a melt texture growth (MTG) method for the REBCO high-temperature superconducting block material. The MTG method for the REBCO high-temperature superconducting block material comprises the following steps of: a) mixing raw materials; b) grinding and calcining to obtain a superconducting material rough blank; c) tabletting; d) firing; and e) cooling to obtain the REBCO high-temperature superconducting block material, namely e1) cooling to buffer temperature, and preserving heat, e2) cooling to growth temperature, and preserving heat, and e3) quenching. By the method, the technical problem that the REBCO high-temperature superconducting block material fails to grow because spontaneous nucleation is generated when temperature is reduced from the maximum temperature to the growth temperature in the conventional MTG method is solved.

The invention relates to the field of alloy directional solidification, in particular to a method for preventing a mixed crystal defect of a single crystal blade based on the laser heating technology. When a mold shell for single crystal blade production is prepared, on a back layer, slurry coating is independently carried out on a blade margin plate through slurry containing titanium diboride, and other mold shell preparation processes are not changed. In the directional solidification procedure of the single crystal blade, the position, where the mixed crystal defect is likely to occur and the margin plate is located, of the mold shell of the single crystal blade is subjected to laser heating, and by means of the effective absorption of the mold shell for laser energy, the margin plate of the single crystal blade is in a local heat preservation state. By means of the characteristics of high concentration and fast heating of the laser heating energy, the temperature of the margin plate is reasonably controlled when alloy of the margin plate of the single crystal blade is solidified, the situation that the margin plate is in a local supercooling state when close to a directional solidification thermal baffle region, then spontaneous nucleation occurs and the mixed crystal defect is caused is avoided, and thus smooth growth of single crystal is guaranteed.

The invention provides a method for growing thallium bromide monocrystal by spontaneous nucleation, comprising the following steps of: 1) filling a thallium bromide material into a cylindrical ampoule with diameter of 8 to 15mm, vacuumizing, sealing, and processing one end of the ampoule into a cone with the cone angle between 15 and 45 degrees; 2) placing the ampoule into a vertical tube furnace with the conical end towards the bottom of the furnace, heating the vertical tube furnace to enable the temperature of the thallium bromide material in the conical tip not to be lower than the melting point of thallium bromide, raising the temperature from the conical tip upward to the inside of a top area of the thallium bromide material with the temperature gradient between 1.0 and 1.5 DEG C/mm, and then, insulating; 3) reducing the temperature of the tube furnace to between 450 and 460 DEG C at the speed between 1 and 5 DEG C/h; and 4) cooling the ampoule to room temperature along with the furnace. Because a heater and the ampoule are not required to be moved, the invention saves the complicated mechanical transmission device, simplifies the technology and reduces cost. The ampoule and the heater are both fixed, the temperature field is stable, heat inside the crystal and molten mass is uniformly distributed, a convex growth interface can be easily acquired, and the thallium bromide with good integrity and considerable size can be grown.

The invention relates to a long wave infrared nonlinear CdGa2Se4 crystal as well as a growth method and the use of the crystal. The CdGa2Se4 polycrystal material is synthesized by virtue of a high-temperature solid-phase reaction; the long wave infrared nonlinear CdGa2Se4 crystal is grown by use of a spontaneous nucleation Bridgman-Stockbarger method or an oriented seed crystal assisted Bridgman-Stockbarger method; the frequency doubling effect of the obtained nonlinear optical CdGa2Se4 crystal powder is about three times of that of AgGaS2, and the transparent waveband of the infrared region of the CdGa2Se4 crystal powder is capable of reaching long wave infrared 21 microns; besides, the CdGa2Se4 crystal powder is good in mechanical properties, stable in chemical properties, not prone to deliquescence, and suitable for orientation, cutting and polishing. The long wave infrared nonlinear CdGa2Se4 crystal is applicable to manufacturing infrared nonlinear optical devices.

The invention discloses a seeding mold for growing silicon crystals by using an orientated solidification method and a crystal growing method. The seeding mold is arranged at the internal bottom of a quartz crucible and comprises a seed crystal container and a sealing liquid container, wherein the sealing liquid container consists of cavities connected to the periphery of the seed crystal container and is used for accommodating a sealing substance; and the seed crystal container is provided with a first cavity for accommodating seed crystals. A method for growing monocrystalline silicon/similar monocrystalline silicon by adopting the seeding mold comprises the following steps of: arranging or setting the seeding mold at the bottom of the quartz crucible; arranging the sealing substance and the seed crystals in the sealing liquid container and the seed crystal container respectively; putting a silicon raw material into the quartz crucible; and growing monocrystals/similar monocrystals by adopting orientated solidification. By adopting the seeding mold and the crystal growing method, the problem of placement of the seed crystals can be solved without changing the structures of the conventional orientated solidification and quartz crucible, dislocation of the seed crystals in the seeding process is eliminated, and the spontaneous nucleation phenomenon of melt from the bottom wallface of the crucible is avoided. The seeding mold has low cost and is easy to process.

The invention belongs to the technical field of crystal growing equipment, and relates to a controlled DAST crystal growing device for a spontaneous nucleation process. A growing cylinder is fixedly placed in a water bath cylinder filled with water bath, a silica gel plug is mounted at the opening position of the upper part of the growing cylinder in a sealed manner, and the growing cylinder is filled with DAST crystal growing solutions; an inclined polytetrafluoroethylene plate is placed in the DAST crystal growing solutions; one end of a thin glass tube is formed into a tapered opening structure and vertically penetrates through the silica gel plug; an injector is placed outside the growing cylinder and is connected with the thin glass tube in a sealed manner through a flexible PVC pipe; a thermoelectric couple is mounted at one side of the top part of the water bath cylinder, and the thermoelectric couple is inserted into the water bath; an infrared heating lamp is placed on the outer side wall of the water bath cylinder; a temperature controlled meter is placed outside the water bath cylinder and is in electrical information communication with the thermoelectric couple and the infrared heating lamp; the structure of the device is simple, the usage and the operation are convenient, the effective control of the nucleation number and the position can be realized during the crystal growing, the success rate of the grown crystals is high, and the quality of the crystals is better.

A capacitor (110), wherein the capacitor (110) comprises a capacitor dielectric (112) comprising a dielectric matrix (114) of a first value of permittivity, and a plurality of nanoclusters (116) of a second value of permittivity which is larger than the first value of permittivity which are at least partially embedded in the dielectric matrix (114), wherein the plurality of nanoclusters (116) are formed in the dielectric matrix (114) by spontaneous nucleation.

The invention relates to a method for growing a cerium-doped lanthanum bromide scintillation crystal by using an out-of-phase seed crystal. The seed crystal made of a crystal material of which the structural parameters and symmetry are similar to those of a lanthanum bromide crystal is placed in a nucleation area at the bottom of a quartz crucible, the seed crystal material and lanthanum bromide are not subjected to chemical reaction, and the melting point of the seed crystal material is higher than that of the lanthanum bromide crystal. The crystal is grown by a crucible descending method, two-section temperature control is performed at the melting stage of a raw material to ensure that the upper part is cold and the lower part is hot, the convection effect of a melt is improved, the lanthanum bromide is nucleated on the surface of the seed crystal preferentially in the crucible descending process, the growth direction of the lanthanum bromide is consistent with the crystallographic direction of the seed crystal, and the lanthanum bromide crystal in the required direction is obtained by continuous growth. The method has the advantages that: a stable crystal material in air can be selected as the seed crystal, and the phenomenon that processing and anhydrous operation are difficult to perform when the lanthanum bromide crystal is taken as the seed crystal is avoided; and compared with a seed-crystal-free spontaneous nucleation growth method, the method has the advantage that: the success rate of oriented crystal growth is greatly improved.

The invention discloses a method for quickly growing an REBCO high-temperature superconducting block by stepped slow cooling acceleration, by using a c-axis-oriented NdBCO/YBCO/MgO film as a seed crystal, contacting the ab surface of the film seed crystal with the upper surface of a precursor block, putting the precursor block and the film seed crystal in a growth furnace, and carrying out melt structure growth. The temperature procedure of the growth furnace is as follows: heating from room temperature to 960 DEG C within 5 hours, and keeping the temperature for 3 hours; continuing heating to the maximum temperature Tmax, and keeping the temperature for 1-2 hours; cooling to the initial growth temperature Ts within 15 minutes; and growing the REBCO high-temperature superconducting block according to the stepped slow cooling acceleration growth procedure. The method disclosed by the invention can not generate spontaneous nucleation and second-phase enrichment on the premise of ensuring the induced growth of the seed crystal; and the gradually increasing cooling rate ensures the increasing driving force required by growth.

The invention relates to a method for growing a large-size vanadium sodium iodate crystal by using a hydrothermal method. A Na-containing compound, a V-containing compound and an I-containing compound are used as raw materials in the method for growing the large-size vanadium sodium iodate crystal by using the hydrothermal method; and the crystal is grown in two manners, namely spontaneous nucleation and adoption of a seed crystal. According to the method, successful raw material proportion and growth processes are provided, growth of the massive crystal with a crystal plane is realized, and the maximum size of the crystal exceeds two centimeters.

The invention provides a method of regulating a particle size of a glycine crystal product by a manner of generating seed crystals via spontaneous nucleation. According to the method, a glycine saturated aqueous solution serves as a raw material; the quantity and the particle size of crystal nucleuses in a spontaneous nucleation process are controlled by regulating a nucleation supersaturation degree; and the glycine crystal product is obtained by cooling crystallization of the crystal nucleuses generated by the spontaneous nucleation as the seed crystals. The method particularly comprises the steps of cooling, nucleation induction at a constant temperature, grain growth at the constant temperature and the cooling crystallization. The glycine crystal product in different particle sizes can be prepared by using the method.

The invention relates to a preparing method of large diameter yttrium barium copper oxide superconducting single domain blocks, which belongs to the preparing technical field of superconducting ceramic. The invention provides a method for growing large-size and high-temperature superconducting single domain blocks through improved top-seeded melt texture. The method adopts large-size samarium barium copper oxide (Sm-Ba-Cu-O) seed crystal and an yttrium barium copper oxide (Y-Ba-Cu-O) preforming green body which is prepared according to defined chemical mixtures, the former is laid on the top of the latter, and melt texture growth method is performed in a high-temperature condition. The method overcomes the problem that spontaneous nucleation is easy to occur during the process of melt texture growth of small-size seed crystal, and effectively realizes the growth of large-size high-temperature yttrium barium copper oxide superconducting single domain blocks through a top-seeded melt texture method.

The invention provides a growth method of a graphene single crystal, and the method comprises the following steps: growing graphene on a substrate through chemical vapor deposition, and introducing anoxidizing gas in the growth process. The invention also provides the graphene single crystal formed by the method. According to the growth method, continuous spontaneous nucleation in the graphene growth process is inhibited as an entry point, and the formation of metastable nuclei in the graphene growth process is destroyed by continuously introducing a trace amount of the oxidizing gas for continuous passivation. According to the method, on the basis that the quality of the graphene is not influenced, the uniformity of the size of the domain region of the graphene is remarkably improved, and then the performance of the graphene in the aspects of electric conduction, heat conduction, mechanical strength and the like can be effectively improved.

The invention relates to an RbZn2BO3Cl2 nonlinear optical crystal, preparation and application. The crystal does not have a symmetric center, belongs to a trigonal crystal system, has a space group ofR32, and has the cell parameters of: a=4.9698angstrom, b=4.9698angstrom, c= 27.178angstrom, alpha=beta=90degree, and gamma=120degree. A single crystal can be obtained in a self-flux system by a spontaneous nucleation method; a high temperature solid phase synthesis method is employed to obtain solid powder; high temperature melt spontaneous crystallization process growth is carried out to obtainlaminar and transparent single crystal without wrappage, the obtained crystal has wide light-transmitting wave band, and has high transmittance at 300-2000nm, and the ultraviolet cut-off edge is lessthan 200nm; powder frequency-doubling effect test shows that the crystal can achieve phase matching and the frequency-doubling effect is equivalent to that of KBe2BO3F2 crystal; the crystal has the advantages of high hardness, good mechanical properties, difficult fragmentation and deliquescence, easy processing and preservation, etc.; and the crystal can be used for preparation of nonlinear optical devices.

The invention discloses a preparation method of a pagoda-shaped large-size REBCO (RE-Ba-Cu-O) high-temperature superconductor block. The preparation method comprises the following steps of: taking a c-axis oriented NdBCO/YBCO (Yttrium Barium Copper Oxide)/MgO film as a seed crystal, enabling an ab surface of the film seed crystal to be in contact with the upper surface of a precursor block, and putting the pagoda-shaped precursor block and the film seed crystal in a growth furnace to carry out fusion structure growth. The invention also discloses the pagoda-shaped large-size REBCO high-temperature superconductor block, which is a pagoda-shaped single-domain block and is free of weak connection of crystal boundaries. The preparation method of the pagoda-shaped large-size high-temperature superconductor block has the advantages that no spontaneous nucleation is generated due to application of an accelerated cooling method, the growth speed is high, and no seed crystal block needs to grow in advance, and can be used for growth of various REBCO high-temperature superconductor blocks and doping growth REBCO blocks. In addition, the preparation method is simple, easy to operate and is available in repeatability and controllability.

The invention provides a method for inversely growing REBCO block. The method comprises the following steps: preparing powder of an RE123 phase and powder of an RE211 phase; preparing an embedded seed precursor: uniformly mixing the powder of the RE123 phase and the powder of the RE211 phase in a ratio of RE123 + 30mol% RE211 + (0.3-0.5) wt% CeO2, pressing to form a cylindrical precursor, and in the pressing process, horizontally and fixedly embedding seed crystal into a central area of the upper surface of the precursor to form the embedded seed precursor; inverting the embedded seed precursor on the surface of an unpolished MgO substrate, and growing the REBCO block in a growing furnace through the fusion texture method. By the method, liquid loss of the precursor can be effectively inhibited, component deviation and spontaneous nucleation can be reduced, pollution can be prevented, stress can be reduced, and thus preparation of the REBCO block is facilitated.