Search

In this paper, the YAG powder is prepared by the co-precipitation method. In addition, the sintering aid to aid sintering and the high temperature foaming agent that becomes gas released during the heating process so that the sample has pores, the ball mill mixes the material, and the sample press is extruded. Box-type resistance furnace sintering. Through this process, porous ceramics can be made. Study the effect of sintering aid content, foaming agent type, sintering temperature on the properties of YAG porous materials. The analysis and discussion can lead to the following conclusions: as the content of sintering aid silica in the sample increases, the sintering temperature of the sample decreases. It is best when the ratio of sintering aid alumina to silica is 3:1. The moldability of the sample whose foaming agent is wood chips is worse than that of the sample whose foaming agent is fiber and carbon powder. The ratio of sintering aid alumina to silica is 3:1, and the sintering temperature of the sample with carbon powder as the blowing agent is best when the sintering temperature is 1400 °C.

Yttrium aluminum garnet is abbreviated as YAG, which has many excellent high temperature characteristics. YAG structural materials and functional materials are promising candidates. In this paper, YAG porous ceramic materials with different mechanical properties are prepared by adjusting the parameters of the sintering process to provide reference for the preparation of high-performance porous ceramics. From the experimental results, the following conclusions can be drawn: when the sintering temperature is 1450°C and the holding time is 2h, the YAG gradient porous ceramics have no deformation and shrinkage, have a regular good shape, and have good strength after sintering. The sintering rate was 8 °C/min and carbon emission temperature is 800°C, the structure of the YAG gradient porous material is good, the pores are uniform, and the strength of the sintered sample is high, The porosity is 25.7%, the compressive strength is 8.12MPa.

The effect of forming technology on the properties of quartz sand porous materials were researched with the low grade quartz sand along the Yangtze River via the pressureless sintering method in this paper, which lay technology foundation for researching new heat insulating materials. The wear of ball milling media is investigated through adjusting the ball milling parameter via the weigh methods. The results are shown that the porosity of quartz sand porous materials are decreased with increasing a forming pressure. The porosities of Φ30 and Φ50 materials are decreased with increasing a holding pressure time, however, the porosity decreasing rate of Φ30 is slower than that of Φ50. The porosity of Φ50 is higher than that of Φ30 under same forming conditions. Through optimized the forming conditions, the porosity of sintered Φ50 quartz matrix porous materials reaches 54.52% under the forming pressure for 5MPa and the holding pressure time for 5min.

In this paper, the effect of sintering temperature on the interfacial structure of the composite was investigated and three different formulation groups were used to compare the respective properties. To obtain a composite material with excellent interface, the law between reference number and performance is obtained. Through mixing, molding, sintering, sample preparation, scanning electron microscopic observation, energy spectrometer observation and analysis, the following conclusions can be drawn: As the temperature increases, the density and hardness increase. The sample melts at 1500 °C, and there is no specific data. When the temperature reaches 1450 °C, the density and hardness reach the highest. When the formulation is Fe:Al2O3:SiO2=18:1:1 and the temperature reaches 1450 °C, the properties of the sample materials are optimized. The density is as high as 95% and the hardness reaches 42.9HBW.

YAG materials have a number of unique properties, the application is very extensive. In order to improving the properties of YAG porous materials, the effect of forming processing on the properties of YAG porous ceramics is investigated. Through the results and analysis, the conclusions showed that the porosity of YAG porous ceramics gradually decreased with the molding pressure increases, and the compressive strength of YAG porous ceramics shows a rising trend. The size and number of pores in the microstructure are reduced with increasing the forming pressure, there are inherently many voids in the YAG porous ceramics body at low forming pressures. The porosity of YAG porous ceramic decreases with the increase of dwell time, however, the process of extending from 5 min to 10 min is much faster than the rate of descending from 10 min to 15 min. The size and number of pores in the microstructure are reduced with extending the holding pressure time, which also makes YAG porous ceramics pose the higher mechanical strength. Through the analysis of the results, when the forming pressure is 10MPa, the porosity of YAG porous ceramics is 41.11% and the compressive strength is 5.8MPa, the porosity and compressive strength of YAG porous ceramics is better.

YAG materials have a number of unique properties, the application is very extensive, the burn is due to the temperature is too high or the residence time at high temperatures is caused. The undercurrent is the sintering temperature is too low or the holding time is not enough, resulting in product performance is too low or too small shrinkage. In this paper, the effect of sintering temperature on properties of YAG porous ceramics was investigated. The results showed that the firing temperature of the ingredients will be different and cause the same sintering process and sintering additives content of different samples burned. The increase in the content of SiO2 in the furnish with the sintering aid tends to occur. the effect of temperature on the mechanical properties of the samples after sintering was significant, so the raw materials include 60wt%YAG, 10wt% CaO, 10wt% SiO2 and 20wt% soluble starch, the molding process in 20MPa pressure 10min, the sintering at 1500°C for 2h, the sample porosity is 42.2%, the compressive strength is 5.8MPa, the outside shape is keep intact and the better pore microstructure is shown.

The YAM coatings on the ZrB2 composites surface were prepared by co-precipitation technique and with Al (NO3)3 and Y(NO3)3 solutions acting as precursor. The effect of matrix surface treating conditions, dipping times and calcination temperature was investigated. Phase compostion, coating morphology and interface between matrix and coating were analyzed by XRD and SEM. The results indicated that the YAM coating was formed after calcined at 1250°C in vaccum. The thickness of coating was increased with the dipping times, the smoothest coating was obtained by two dipping times, and matrix surface coarsing was beneficial for improving the adhension between matrix and coating. The ablative teste was evaluated at 2000°C by oxy-acetylene flame, the ablative properties was obviously improved by coating compared with uncoated composites.

A high-performance quartz sand insulation brick was prepared by using low grade quartz sand under different sintering process conditions. The optimum sintering process conditions were obtained by analyzing the relationship between microstructure and sintering process. Through the compounding, pulping, forming, drying and sintering processes, and the performance test of the porous brick, the following conclusions can be drawn, the comprehensive performance in all aspects, the porosity is similar, the preferred high compressive strength conditions, in order to get a best The bonding point, brick body sintering temperature of 1150 °C, porosity of 74.56%, compressive strength of 2.1 MPa of porous brick, and the pores are smooth, more uniform distribution. With the prolonging of the holding time, the porosity of the porous brick is reduced, and the performance is 1h, the porosity is 77.22% and the compressive strength is 2.05 MPa. When the raw material ratio is 60% quartz sand, 30wt% kaolin, calcium carbonate 9.6wt%, foaming agent 0.4wt%, water ratio 0.9 holding time at 1h sintering at 1150°C can get better porosity and compressive strength of the insulation brick. The porous material was sintered at 1150 °C, the content of foaming agent was 0.2wt%, the ratio of water to material was 0.9, and the compressive pressure and porosity were the better.

YAG has many excellent features and therefore has a wide range of applications. Preparation and properties of YAG porous ceramics via the casting method is investigated. Through analysis and discussion, the following conclusions can be obtained. With the increase of the content of foaming agent, in the foaming process of the slurry, bubbles generated by the foaming agent and water are gradually increased, the more pores are left in the body after casting, and when the blowing agent is too much, excessive bubbles are generated, which can lead to a very low strength of the green body and can not be formed and operated later. As the ratio of water to material increases, the porosity of the porous material increases. This is because when the blowing agent is constant, the amount of water required for foaming is constant, and the amount of foam generated is also constant. When the content of foaming agent and the ratio of water to material is both 1, the porosity and compressive strength is better.

The sintering methods of quartz sand porous ceramics were researched with the low grade quartz sand along the Yangtze River via the vacuum sintering method in this paper, which lay technology foundation for researching new heat insulating materials. The quartz porous ceramics is obtained with the high performance cost, the quartz porous ceramics is sintered at 1050°C via the vacuum conditions, the density of ceramics is 1.267g/cm3, the porosity is 51.6%, the compressive strength is 3.184MPa, the porous ceramics show the homogeneous distribution micro-pore and good shape. The density and the compressive strength of prepared ceramics via the vacuum sintering both are higher than that of prepared ceramics via the atmosphere sintering, however, the porosity is shown the opposite results.

Zirconium diboride is widely applied because of some excellent performances. The oxidation kinetics of ZrB2-YAG-Al2O3 composite materials were researched, which helps to improve the performance of ultra-high-temperature composite materials. The results show the oxidation weight gain is decreased with increasing the content of YAG-Al2O3 and the molar ratio of Al2O3. The oxidation weight gain is increased with prolonging the oxidation time under 1300°Cæ, the oxidation weight gain ratio is decreased with prolonging the oxidation time. The effecting tendency of oxidation weight gain is not abvious with varying the contend of YAG-Al2O3 upon 1300°Cæ, however, the effecting tendency of oxidation weight gain is very abvious with varying the molar ratio of Al2O3.

The composite ZrB2 powder coated A12O3-Y2O3 prepared by co-precipitation method were densified via the spark plasma sintering (SPS) and then researched the oxidation resistance at high temperature. ZrB2 powder must have the better dispersibility during the coating processing for obtaining the better coating effect. Effect of dispersant on the dispersibility of ZrB2 powder in the liquid is researched in this paper, the results show ZrB2 powder have the better dispersibility as the dispersant for PMAA and the content for 2vol%, which lay foundation for synthsising the better coating effect coated A12O3-Y2O3-ZrB2 composite powder.

Cermet materials is a important new engineering materials with the advantages of ceramics and metal materials. The Al2O3/Al cermet materials is prepared via the powder metallurgy method, the effect of sintering technology on properties of Al2O3/Al cermet materials is researched in this paper, which lay the base for preparing the high performance cermet materials. The results are shown through the study, the denstity of cermet is increased with an increasing moliding pressure, the sample density is 2.084g/cm3 as the pressure for 40MPa and the sintering temperature at 600¡æ, the density is higher, that is to say it is highest performance, the distribution of aluminum and alumina is most uniform. When the sintering temperature is higher, howerver, the molding pressure is lower, the lower density of the sample is shown, the aluminum is easier to overflow the surface of the sample.

Zirconium diboride (ZrB2) ceramics with high melting point, high hardness, good electrical and thermal conductivity, good neutron control and other characteristics, can be widely used in high-temperature structural ceramics, composite materials, electrode materials. In order to improve ZrB2 difficult densification and high-temperature oxidation, the properties of coated Al (OH)3-Y(OH)3/ZrB2 composite powders prepared by co-precipitation method were investigated in this paper, The conclusions are shown that the effect of coated composite powders is getting worse with the accelerated titration rates. the coating effect will be worse with the increasing reaction time. When the concentration of mixed solution is lower, the coated effect is better. When the synthesis condition is that the titration rate of 10ml/min, and the reaction time was 1h, mixed solution ion concentration of Y3+=0.119mol/L and Al3+=0.231mol/L, the coated effect of composite powders is better.

Pore gradient material has obvious uneven, making the material porosity, pore size and strength changes with the thickness of the material exhibits a special distribution, pore gradient material is therefore in the chemical industry, environmental protection, metallurgy, food, biotechnology and other industries widely used, it is a very promising new material. In this paper, low-grade quartz sand as the main raw material, by adding auxiliary ingredients, using foam deposition method, the pore graded material were prepared. Through experimental results and analysis, the conclusions can be obtained, quartz pore gradient material body after sintering at 1300¡æ posing obvious gradient structure. When the ratio of water to 1.4 and 1.5, the sample can be observed that there is a clear gradient structure. Considering the combination of price, quality quartz pore gradient material should be water feed ratio of 1.4, the sintering temperature is 1300 ¡æ more appropriate, the porosity of prepared quartz graded materials was 32.45%.

Cermet while maintaining the excellent properties of ceramic materials, but also have the advantages of a metal material, is an important new engineering materials. In this paper, prepared by calcination of alumina - aluminum metal-ceramic composite material powder, and its characterization as a basis to provide raw materials for preparing high performance metal ceramic material. According to the research, with the calcination temperature is increased, the rate of change gradually increase the weight of aluminum. Calcined at a temperature of 600¡æ, the oxidation of aluminum surface the best. With the firing time increases, the rate of change in the weight of aluminum powder showed an increasing trend. When 8h, oxidation of aluminum surface better. Through this experiment, process optimization can be found in the calcination temperature was 600¡æ, calcination time is 8h, the best coating effect aluminum surface, coating evenly, clean interface, the reaction layer thickness of about 700nm, the prepared package type composite powders the best results.

The technology of quartz pore gradient ceramics were researched with the low grade quartz sand along the Yangtze River via the vacuum sintering method in this paper, which lay technology foundation for exploiting new heat insulating materials. The research results are shown as following, when the ratio of water to raw materials is 1, the shape and pore distribution of pore gradient ceramics is better. The porosity are first increased and then decreased with an increasing the sintering temperature. The suitable sintering temperature is decided at 1100°Cæ, the density is 1.343g/cm3, the porosity is 48.7%, the compressive strength is 7.071MPa, and the pore gradient structure is homogeneous transition zone.

The shell structure YAG composite powders with different volume fraction (15, 20 and 25vol%) micro h-BN have been prepared by co-precipitation process. The bulk composites were performed by pressure sintering at 1600°C under a pressure of 30MPa in vacuum. The mechanical properties (elastic modulus, hardness, and fracture toughness) and relative density of the composites were investigated detailedly. Furthermore, phase composition and microstructure of the composites were analyzed thoroughly by X-ray diffraction, scanning electron microscopy. Meanwhile, good machinability is maintained due to the low hardness of the second phase.

Alumina-zirconia (Al2O3-ZrO2) composite ceramics were prepared by means of cross spraying and hydrothermal method under atmospheric pressure with nanometer powders doped with ZrO2 as the raw material. Then, the prepared powders and ceramics were characterized by SEM, XRD and BET methods. The results showed that combining cross spraying with hydrothermal method under atmospheric pressure could improve the dispersity of the ZrO2 composite ceramics nanopowders, while adding Al2O3 accelerated the low temperature sintering for 3Y-ZrO2 and improved the bending strength, fracture toughness and density of ZrO2 composite ceramics. In addition, through optimization the bending strength and fracture toughnessof the obtained ceramic, were 1,150 MPa and 8.2 MPa∙m1/2 respectively.

YAG is an important advanced structural and functional material. The mechanism of controlling pore microstructure of YAG porous ceramics were investigated in this paper. Through the porosity and SEM result analyzing, the conclusions are shown as follows, the porosity and the pore size of YAG porous ceramics are decreased with increasing the sintering temperature, the pores of YAG porous ceramics show a regular and well-distributed structure as lower sintering temperature, the porosity of YAG porous ceramics is increased with increasing the foaming agent content, but the increasing tendency is few after adding content more 15wt%, when the foaming agent content is less than 15wt%, the big pore is more and the pore microstructure is better. So the sintering temperature at 1500°C for 1 hour and the foaming agent content for 15wt% are better controlling conditions for obtaining better porosity and pore microstructure.

ZrB2 has some excellent high-temperature performance. However, due to it is easily oxidized in the high-temperature air to impact high-temperature strength, which restricts its applied range. To decrease the oxidization and sintering temperature, and improve the strength of ZrB2 at high temperature, in this paper, the prepared composite powders is analyzed with XRD, SEM, EDS and TEM, which proves ZrB2@A12O3-Y2O3 core-shell composite powders are successfully synthesized by co-precipitation method, the synthesis mechanism of ZrB2@A12O3-Y2O3 core-shell composite powders is received through the results discussion.

Yttrium aluminum garnet (YAG) with a chemical composition of Y3Al5O12 is an important advanced structural and functional material.The preparation conditions were a pH of 9, a titration rate of 10ml/minute and a reaction time of 60 minutes. The analysis shows that the YAG precursor does not have an obvious characteristic crystalline diffraction peak, the characteristic diffraction peak of YAG was found after the calcination of the YAG precursor at 1100¡æ for 1 hour, the characteristic diffraction peak of YAG is strong, which indicates that the YAG crystalline phase is integrated and pure. The pore microstructure of porous YAG ceramics marked differed with an increase in the sintering temperature, the compressure strength of porous YAG ceramics is increased with an increase in the sintering temperature, the compressure strength shows the opposite rule with the prosity, which indicaties the mechanical properties of materials are effacted with the densification effect of materials.

The low grade quartz sands is the main raw material to prepare the unfired porous brick through adjusting the maitenance technology. The compressive strength of brick is higher with the maitenance temperature for 40¡æ. The compressive strength of brick is higher with the longer maitenance time. The high performance brick is prepared via the third technology, the pore of brick is more and uniform, it is bowl shape, that is close pore, which provide the reference for preparing the heat insulating materials. The compressive strength of brick is 1.9MPa, the density is 0.628 g/cm3.

Zirconium diboride (ZrB2) acts as an ultra-high-temperature ceramics, and are applied in over 2000°C environment. With the characterization of strong covalent bonding structure and high melting point, it is difficult to realize sintering. For achieving composites system densification, the transition metals with good wettability and other matching properties, or the second phases ceramics were added as sintering aids, but the bulk materials' application temperature limit and ablating rate resistance were reduced by sintering aids. Among the A12O3-Y2O3 binary phase system, YAM(Y4A12O9) has the highest melting point, chemical and physical compatibility is matched with ZrB2 composites. The YAM coating was prepared on bulk materials surface by co-precipitation routine, the effects of precursor volume fractions and calcining process on coating phases were investigated, and the coating morphology and interface bonding were observed. The aim is to obtain the best protective coating constituents and technology parameters.

ZrB2, YAG and Al2O3 are widely applied because of some excellent performances, but ZrB2 is easily oxidized in the high-temperature air. To make the ZrB2 ceramics obtain better oxidation resistance, high-density ZrB2-YAG-Al2O3 ceramics were prepared. The oxidation mechanism of ZrB2-YAG-Al2O3 ceramics is investigated. When YAG-ZrB2 ceramics are exposed to air at temperatures from 1100°C¡æ to 1600°C¡æ, the weight change rate of YAG-ZrB2 ceramics is fleetly increased, the reacted speed of ZrB2 and O to form B2O3 and ZrO2 is more faster. The quantity of melted B2O3 is increased and carried to the surface, B2O3 is reacted with Al2O3 to form Al18B4O33. Al18B4O33 is melted and coated on the surface of ceramics to form protection layer for the oxidation resistance of ceramics at high temperature, which shows the similar with the influence of reinforcing phase on the oxidation model of ZrB2 based multi-phase ceramics.

ZrB2, YAG and Al2O3 are widely applied because of some excellent performances, but ZrB2 is easily oxidized in the high-temperature air. To make the ZrB2 ceramics obtain better oxidation resistance, high-density ZrB2-YAG-Al2O3 ceramics were prepared. The influences of coated composite powders on the densification and the oxidation resistance of ZrB2-YAG-Al2O3 ceramics were investigated. The 80wt%ZrB2-YAG-Al2O3 multiphase ceramic materials from different composite raw materials with the spark plasma sintering technique were successfully prepared. The densification of ZrB2-YAG-Al2O3 ceramics with Al2O3-Y2O3 composite powder coated is easier than that of ZrB2-YAG-Al2O3 ceramics with YAG-Al2O3 powder mixed. The reaction temperature is lower than the 1100¡æ for synthesizing YAG powders from Al2O3-Y2O3 composite powders. The weight gain are increased with increased the oxidation temperature. B2O3 is reacted with Al2O3 to form Al18B4O33, Al18B4O33 is melted and coated on the surface of ceramics to form a protective layer for the oxidation resistance of ceramics at high temperature. The oxidation weight gain of ZrB2-YAG-Al2O3 ceramic with Al2O3-Y2O3 composite powder coated is lower than that of ZrB2-YAG-Al2O3 ceramic with YAG-Al2O3 powder mixed.

Yttrium aluminium garnet (YAG) possesses many good properties, and usually uesd as sintering additives for silicon carbide ceramics. The YAG precursor solution was preformed by the coprecipitation process, then 8wt% prepared precursor solution was added and uesed as binder for samples' green bodies dry mould pressing. The dried pressed samples were directly sintered at 1850¡æ under vaccum atmosphere, and the precursor Al2O3-Y2O3 could be formed YAG during sintering process. The oxidation resistance property was performed at 1500¡æ in air. Bulk density and porosity were about 2.42g/cm3 and 24.98% respectively, and three-point bonding strength was up to 90MPa. Phase composition of sintered specimen was determined by X-ray diffraction and fracture morphology was detected by scanning electron microscope (SEM). The results showed that the as-fabricated porous SiC ceramics exhlibted excellent oxidation resistance abilities, its oxidation resistance improvement was benefited from silicon carbide particle coated with a compact YAG layer. The relationship between microstructure and properties was analyzed, and the finally formed phase composition was discussed.

ZrB2 has some excellent physical performance and chemical stability, it has been widely applied in a lot of fields. In order to improve disadvantages of ZrB2 that the sintering densification of ZrB2 is too difficult, and it is easy oxidized at high temperature, in this paper, the sintering character of coated A12O3-Y2O3/ZrB2 composite powder materials via spark plasma sintering were investigated. Al2O3-Y2O3/ZrB2 composite powders were prepared by a co-precipitation methods. When the pH is 9, the encapsulted structure of A1(OH)3-Y(OH)3/ZrB2 composite powders is the best. By analyzing the ZrB2 surface status with TEM, the A12O3-Y2O3/ZrB2 composite powders were prepared under the calcining conditions of 600°C¡æ in argon. The high density ZrB2-YAG multi-phase ceramics are prepared via spark splama sintering, which indicate the raw materials adding A12O3-Y2O3 help for the densification of ZrB2 ceramics.

In order to lay raw materials foundation for increasing the performance of insulating brick with the low grade quartz sand along the Yangtze River, the quartz porous ceramic materials was researched in this paper. The results show the porosity of the porous quartz ceramics decreased with an increase in the sintering temperature. The pore is like the bowl shape, and the pore is closed pore, which is help to improve the heat insulation property of quartz porous ceramics. The CaSiO4 is produced in the ceramics after sintering processing. The shape is better, and the microstructure is circular and symmetrical pore, which is help to improve the mechanical property of quartz porous ceramics.

Porous quartz ceramics were produced using river sand from the Yangtze River in China as the raw material by the use of sponge absorption methods. We found that sintering conditions clearly affected the porous structure and other properties. With increasing sintering temperature, the microstructure of the samples changed accordingly and the density increased while the porosity decreased, the micropore edges gradually became smooth. The density of the porous quartz ceramics increased at a holding time of up to 60 min but the porosity decreased. Optimum sintering of the porous quartz ceramics was obtained at 1 100 °C over 60 min as determined by an analysis of the performance–price ratio of the porous quartz ceramics, the density is 1.25 g cm–3, the porosity is 49.5 %, the outside shape is regular, the micropore structure is smooth.

Due to some excellent properties of YAG, it is researched and applied widely. The YAG porous ceramics are prepared via the vacuum sintering technology. The results show that a certain relationship is existed between carbon emissions time and increasing temperature speed, increasing temperature speed is faster, carbon emission time is shorter, entire sintering cycle is shorter, which makes porosity similar, but higher compressive strength is shown, therefore, the increasing temperature speed slightly faster is advantageous to the performance of YAG porous ceramics, that is to say the heating rate of 5℃/min. By appearance, porosity, compressive strength performance comparison that carbon emissions at 800℃ is more appropriate, porous ceramic YAG prepared under 1500℃ and 1h shows the white surface, 59.4% porosity and compressive strength of 8.55MPa.

ZrB2 belongs to a class of ceramics defined ultra-high-temperature ceramics with extremely high melting temperatures, but ZrB2 ceramics is difficultly sintered and easily oxidized. To make ZrB2 ceramics possess the high relative density and the better oxidation resistance. The effects of adding phase on the sintering and oxidation resistance mechanism of ZrB2 based high-temperature multi-phase ceramics were investigated. YAG and Al2O3 help for the densification of ZrB2 based ceramics. The oxidation layer thickness of sintered ceramics adding YAG or YAG-Al2O3 phase is thinner than that of sintered pure ZrB2 ceramics under the same oxidation condition, the oxidation layer thickness of sintered ceramics adding YAG-Al2O3 phase is thinner than that of sintered ceramics adding YAG phase, the oxidation layer thickness of sintered ceramics is decreased with an increased Al2O3 content.

The sintering temperature of the quartz sand heat insulating materials were researched thtough the differential analysis of the mixture in this paper. The conclusion show the density of the quartz sand heat insulating brick is increased with increasing sintering temperature, but the porosity of the quartz sand heat insulating materials is opposite discipline curve. The outside shape of the brick body is regular at 1100°C, however, the outside shape of the brick body is irregular at 1150°C, but the porosity of the quartz sand heat insulating materials at 1130°C is lower than that of the quartz sand heat insulating materials at 1100°C. The sintering temperature is higher, the more energy will be consumed. So the better sintering temperature of the quartz sand heat insulating materials is decided at 1100°C through analyzing the performance price ratio of the quartz sand heat insulating materials.

The insulating brick is prepared used low grade quartz sand along the Yangtze River, and the mechanism of porous structure contolment is researched, which lay technological foundation for increasing the performance of insulating brick. The results show the porosity of unfired porous quartz bricks is decreased with increasing the content of quartz sands. When the content of foaming agent is beyond 0.5%, the porosity of unfired porous bricks is increased with increasing the content of foaming agent. When the ratio of materials and water is above 1:1.1, the porosity of unfired porous bricks is decreased with increasing the content of adding water. Through optimizing the technology that using 60% quartz sands, 39% cement, 1% foaming agent and the ratio of materials and water for 1:1.1 are mixed, the unfired porous quartz bricks is produced, the density is 0.628 g/cm3, the porosity is 74.586% and the compression strength is 1.9 MPa, the porous structure of brick is homogeneous distribution, the pore is closed pore.

Zirconium diboride (ZrB2) is difficult to prepare as high-density ceramics, which limits its application. To obtain high-density ZrB2 ceramics for improving its high-temperature properties, ZrB 2 particles were coated with Al2O3—Y 2O3 particles to prepare 20%YAG—ZrB2 ceramics with SPS. The optimum sintering condition is a temperature of 1700°C, a pressure of 20 MPa, and a holding time of 4 min. The relative density of prepared 20%YAG—ZrB2 multi-phase ceramics is 97.2% under optimization sintering technology, which indicate that high density YAG—ZrB 2 multi-phase ceramics are successfully prepared.

ZrB 2 belongs to a class of ceramics defined ultra-high-temperature ceramics with extremely high melting temperatures; however, ZrB 2 ceramics is easily oxidized. To make ZrB 2 ceramics possess the better oxidation resistance in the air at high temperature, in this paper, the effect of surface modification on the properties of YAG– ZrB 2 ceramics were investigated. Fracture toughness of sintered ceramics with coated raw materials is higher than that of sintered ceramics with mixed raw materials under the same phase and phase content conditions. Oxidation layer thickness of sintered ceramics with coated raw materials is thinner than that of sintered ceramics with mixed raw materials. The results indicate that the sintered coated structure ceramics with coated raw materials help to increase the mechanical property and oxidation resistance of YAG– ZrB 2 ceramics.

ZrB2 has some excellent high-temperature performance. However, because it is easily oxidized in the high-temperature air to impact high-temperature strength, its applied range is restricted. To decrease the oxidization and sintering temperature and improve the strength of ZrB2 at high temperature, in this article the prepared composite particles are analyzed with XRD, SEM, EDS, and TEM, which proves that ZrB2@A12O3-Y2O3 core-shell composite particles are successfully synthesized by coprecipitation method.

ZrB2 belongs to a class of ceramics defined ultra-high-temperature ceramics (UHTCs) with extremely high melting temperatures, but ZrB2 ceramics are difficult for densification. To make high relative density and good high-temperature property ZrB2 ceramics, in this article, the effect of YAG content on the property of YAG–ZrB2 multiphase ceramics is investigated. The sintering shrinkage is increasing with the increasing of the YAG content from 10% to 40%. The relative density increases with the increase of the YAG content from 10% to 40%, but the rate of increasing relative density from 10% to 30% is higher than that of 40%. When the content of YAG is higher than 30%, fracture toughness increases a little. The YAG content is more, and the weight gain is less, which shows that the oxidation layer thickness is thinner.

Although ZrB2 has some excellent performances, it is difficult to prepare the high relative-density ZrB2 ceramics, which limits the application of ZrB2 materials. To obtain higher relative-density ZrB2 ceramics for increasing the good oxidation resistance, YAG/ZrB2 multiphase ceramics is prepared with the spark plasma sintering, the sintering mechanism of preparing YAG/ZrB2 multiphase ceramic materials is investigated. Al2O3 reacts with Y2O3 to form YAG above 700°C during the sintering process. YAG is filled and melted the space of ZrB2 particles to bind the ZrB2 particles during reaction and sintering process, which increases the density of YAG/ZrB2 multiphase ceramic materials. The YAG/ZrB2 multiphase ceramic materials was successfully prepared under sintering temperature of 1700°C, holding temperature time for 4 min, and sintering pressure of 20 MPa; the density is 5.63 g/cm3, the relative density is 99.78%.

To obtain the better ZrB2/Al(OH)3–Y(OH)3 core-shell composite particles, ZrB2 particles must be adequately dispersed during the coating process. In this article, the dispersibility of ZrB2 particles in the ZrB2 suspension is investigated via the sedimentation method. Through test and analysis, the dispersibility is rapidly increased with prolonging the ultrasonic dispersion time before 10 minutes. After 30 minutes, the sedimentation grads using ultrasonic dispersion basically reach the sedimentation balance, but the grads using mechanical agitating dispersion does not basically change after 5 minutes. The ultrasonic dispersion is one of more effective ways between ultrasonic and mechanical agitating dispersion, the dispersion time for 10 minutes is chosen in the dispersibility of ZrB2 particles via ultrasonic dispersion.

In order to decrease the oxidization and improve the strength of ZrB2 at high temperature, the surface of ZrB2 was coated with Al(OH)3 and Y(OH)3 to synthesize Al(OH)3-Y(OH)3-ZrB2 composite particles. Through TEM, EPMA and SEM analysis, when pH was about 9, Al(OH)3-Y(OH)3-ZrB2 composite particles were successfully synthesized by co-precipitation methods. The coating layer was about 25 nm, which has compaction and conformability. Dispersibility of coated ZrB2 with Al(OH)3 and Y(OH)3 particles were very good. Synthesis of Al(OH)3-Y(OH)3-ZrB2 composite powder will lay the foundation for preparing high-performance YAG/ZrB2 and Al2O3-YAG/ZrB2 multiphase ceramic materials.