A novel technique for making open-cell Al_2O_3-ZrO_2 ceramic foam with plant seed template

The aim of the present research is to provide a technique for preparing open-cell Al2O3-ZrO2 ceramic foams with uniform cell size.This technique used plant seeds to array templates and centrifugal slip casting to obtain cell struts with high packing density.Aqueous Al2O3-ZrO2 slurries with up to 50 vol.% solid contents were prepared and the rheological characteristic of the slurries was investigated.Consolidation was performed at an acceleration of 2,860 g for 60 min.The effect of the characteristic of plant seeds on the drying behavior of Al2O3-ZrO2 green compact was analyzed.The effects of the solid contents of slurries on segregation phenomena of Al2O3 and ZrO2 particles and green compact uniformity were investigated.The compressive stress-strain curve and deformation behavior of Al2O3-ZrO2 ceramic foams prepared using plant seed template were analyzed.The results showed segregation phenomenon is negligible for highly stable slurry with 50 vol.% solid loading.The prepared cell struts of Al2O3-ZrO2 foams have high green density (61.9% TD), sintered density (99.1% TD) and homogeneous microstructure.When sintered at 1,550 ℃ for 2 h, the cell size of Al2O3-ZrO2 foam is approximately uniform and the diameter is about 1.1 mm.The porosity and compressive strength of sintered products is 66.2% and 5.86 MPa, respectively.

Predicting model on ultimate compressive strength of Al_2O_3-ZrO_2 ceramic foam filter based on BP neural network

In present study, BP neural network model was proposed for the prediction of ultimate compressive strength of Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The inputs of the BP neural network model were the applied load on the epispastic polystyrene template （F）, centrifugal acceleration （v） and sintering temperature （T）, while the only output was the ultimate compressive strength （（7）. According to the registered BP model, the effects of F, v, T on 0 were analyzed. The predicted results agree with the actual data within reasonable experimental error, indicating that the BP model is practically a very useful tool in property prediction and process parameter design of the Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting.

Effects of Interlayer Composition on Bond Strength and Interfacial Microstructure of Green Joined CePO_4-ZrO_2 Ceramics

Effects of interlayer composition on bonding strength and interfacial microstructure of green joined CePO_4-ZrO_2 ceramics were studied. Green bodies of 25%CePO_4/ZrO_2 and ZrO_2 ceramics were joined by using interlayer composed of CePO_4 and ZrO_2 at 1450 ℃ for 120 min without applied pressure.The effects of CePO_4/(CePO_4+ZrO_2) ratio on the bond strength of the joints were investigated. Under the experimental conditions, the grain size of the particles grown in the joint is smaller than those in joined ceramics. The microstructure of the joint is more homogeneous than that of the matrix and without obvious cracks, pores and other defects.

Modeling and analysis of porosity and compressive strength of gradient Al_2O_3-ZrO_2 ceramic lter using BP neural network

BP neural network was used in this study to model the porosity and the compressive strength of a gradient Al2Q-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The influences of the load applied on the epispastic polystyrene template （F）, the centrifugal acceleration （V） and sintering temperature （T） on the porosity （P） and compressive strength （a） of the sintered products were studied by using the registered three-layer BP model. The accuracy of the model was verified by comparing the BP model predicted results with the experimental ones. Results show that the model prediction agrees with the experimental data within a reasonable experimental error, indicating that the three-layer BP network based modeling is effective in predicting both the properties and processing parameters in designing the gradient Al203-ZrO2 ceramic foam filter. The prediction results show that the porosity percentage increases and compressive strength decreases with an increase in the applied load on epispastic polystyrene template. As for the influence of sintering temperature, the porosity percentage decreases monotonically with an increase in sintering temperature, yet the compressive strength first increases and then decreases slightly in a given temperature range. Furthermore, the porosity percentage changes little but the compressive strength first increases and then decreases when the centrifugal acceleration increases.

Effects of Yttrium Ion on Formation Mechanism of ZrO_2-Y_2O_3 Ceramic Coatings Formed by Plasma Electrolytic Oxidation on Al-12Si Alloy

ZrO2-Y2O3 ceramic coating was produced by plasma electrolytic oxidation （PEO） on ZAlSil2Cu3Ni2 alloy. The microstructure and phase composition of the coating were investigated by SEM and XRD.： The results show that adding an appropriate amount of yttrium ion can improve the growing rate of ceramic coating at different oxidation stages and decrease arc voltage. The thickness of ZrO2-Y2O3 coating is 16 μn thicker than that of ZrO2 coating and the maximum oxidation rate improves by 0.6 μm/min. In addition, the arc voltage decreases from 227 to 172 V. It can be seen that the rate of oxidation firstly increases to some extent and then decreases with the content of yttrium ion increasing. The growth rate reaches the maximum while the content of yttrium ion is 0.05 g-L-1The maximum thickness is 90 μm.Compared to ZrO2 coating, the micropores of ZrO2-Y2O3 coating are less and the ceramic layer is repeatedly deposited by ZrO2 and Y2O3 ceramic particles. Meanwhile, the binding force between coating and substrate is better and the coating is uniform and compact. The ceramic layer is mainly composed of c-Y0.15Zr0.85O1.93□0.07, m-ZrO2, α-Al2O3, ,γ-Al2O3 and Y2O3. It is indicated that ZrO2 has beert fully stabilized by yttrium ion through the formation of solid solution.

Effect of Nano-ZrO_2 on Microstructure and Thermal Shock Behaviour of Al_2O_3/SiC Composite Ceramics Used in Solar Thermal Power

The Al2O3-ZrO2（3Y）-SiC composite ceramics used in solar thermal power were prepared by micrometric Al2O3,nano-ZrO2 and SiC powders under the condition of pressureless sintering.The bulk density and bending strength of samples with 10vol% nano-ZrO2 sintered at 1480℃ were 3.222 g/cm3 and 160.4MPa,respectively.The bending strength of samples after 7 times thermal shock tests （quenching from 1000℃ to 25℃ in air medium） is 132.0MPa,loss rate of bending strength is only 17%.The effect of nano-ZrO2 content on the microstructure and performance of Al2O3-ZrO2（3Y）-SiC composite ceramic was investigated.The experimental results show that the bending strength of samples with above 10vol% nano-ZrO2 content has decreased,because the volume expansion resulting from t-ZrO2 to m-ZrO2 phase transformation is excessive;Adding proper nano-ZrO2 would be contributed to improve the thermal shock resistance of the composite ceramics.The Al2O3-ZrO2（3Y）-SiC composite ceramic has promising potential application in solar thermal power.

Oxidation of O'-SiAlON-ZrO_2 Composite Ceramics

The oxidation kinetics of O'-SiAlON-ZrO2 composite ceramics in the temperature range of 1373-1773K has been studied. The oxidation experiments with powder and plates of O'-SiAlON-ZrO2 composite ceramics in air have been carried out. The overall activation energy of oxidation reaction is 263.69 kJ/mol. The products and structures of O'-SiAlON-ZrO2 oxidation layer have been analysed by XRD (X-ray diffraction), SEM (scanning electron microscope) and AFM (atomic force microscope).

Synthesis of Biodiesel Using ZrO_2 Polycrystalline Ceramic Foam Catalyst in a Tubular Reactor

With the help of the ceramic foam research efforts and preparation techniques, the ZrO2 polycrystalline ceramic foam catalyst was synthesized, and its characteristics, including the crystal structure, the phase composition, the acid–base properties, and the microstructure, were analyzed by XRD, SEM, Py-IR, and BET techniques. The performance of the ZrO2 polycrystalline ceramic foam catalyst in a tubular reactor was investigated via biodiesel synthesis using S. wilsoniana oil and methanol. The effects of reaction conditions(i.e., reaction temperature, reaction pressure, and volume ratio of methanol to S. wilsoniana oil) on transesterification efficiency were investigated, and the reaction conditions were optimized using RSM. The optimum reaction temperature, reaction pressure, and volume ratio of methanol to S. wilsoniana oil were determined to be 290 ℃, 10 MPa, and 4:1, respectively. Under this condition, the FAME content in the product oil reached 98.38%. The performance of the ZrO2 polycrystalline ceramic foam catalyst synthesized in this work for biodiesel synthesis from S. wilsoniana oil with a moisture content of 7.1% and an acid value of 130.697 mg KOH/g was examined, and the FAME content in the product oil was found to be 93% and 97.67%, respectively. The FAME content in the product oil exceeded 97% after five consecutive cycles(12 h per cycle of use) of the catalyst. The proposed catalyst represents a new type of solid catalyst with excellent acid resistance, water resistance, esterification efficiency, and catalytic stability.

Preparation of Al_2O_3-SiO_2-TiO_2-ZrO_2 Composite Ceramic Membranes by Sol-Gel Method

Al 2O 3-SiO 2-TiO 2-ZrO 2 supported membranes were prepar ed by Sol-Gel method. These composite ceramic membranes are level, even and no macro crack. There exist several crystalline phases such as Al 2O 3, TiO 2(a natase), Al 2SiO 5, and ZrO 2 in these membranes. Changing the molar ratio of Al∶Si∶Ti∶Zr,the kinds and content of crystal phases of composite membranes could be different, which may lead to a variety of microstructure of membranes. The surface nanoscale topography and microstructure of membranes were investiga ted by XRD,SEM,AFM,EPMA. The effects of additives and heat treatments on the sur face nanoscale topography and microstructure of composite ceramic membranes were also analyzed.

Structure and Dielectric Properties of Sb_2O_5-Doped ZrO_2-SnO_2-TiO_2 Microwave Ceramics

The microwave dielectric properties of ZrO2-SnO2-TiO2 （ZST） system ceramics were studied as a function of the amount of Sb2O5 dopant. With the addition of 0-0.5% Sb2O5（molar ratio）, the substitution of Ti4^＋ ions with Sb^5＋ ions decreased the sintering temperature and increased the quality factor Q due to the reduction of oxygen vacancies, When the amount of Sb^5＋ increased further （above 0.5%）, Q was decreased by increasing the electron concentration. When the system doped with 0.5% Sb2O5 was sintered at 1 150℃ for 6 h, the relative dielectric constant ε, Qf0, and the temperature coefficient of resonant frequency （TCF） were 38.46, 44 500 GHz, 20.0×10^-6/℃, respectively, at 6 GHz,

Properties of Ultra-low Thermal Expansion LAS Transparent Glass-ceramics Prepared by Spodumene

The glass-ceramics were prepared with the spodumene mineral as the main raw material,and the effects of ZrO_(2)replacing TiO_(2)on the samples were systematically investigated.The results show that the substitution of ZrO_(2)for TiO_(2)is not conductive to precipitate𝛽β-quartz solid solution phase,but can improve the transparency and flexural strength of glass-ceramics.And the glass-ceramic with the highest visible light transmittance(87%)and flexural strength(231.80 MPa)exhibits an ultra-low thermal expansion of-0.028×10^(-7)K^(-1)in the region of 30-700℃.

Microstructure and Oxidation Behavior of ZrB_(2)-SiC Ceramics Fabricated by Tape Casting and Reactive Melt Infiltration

ZrB_(2)-based ceramics typically necessitate high temperature and pressure for sintering,whereas ZrB_(2)-SiC ceramics can be fabricated at 1500℃using the process of reactive melt infiltration with Si.In comparison to the conventional preparation method,reactive synthesis allows for the more facile production of ultra-high temperature ceramics with fine particle size and homogeneous composition.In this work,ZrSi_(2),B4C,and C were used as raw materials to prepare ZrB_(2)-SiC via combination of tape casting and reactive melt infiltration herein referred to as ZBC ceramics.Control sample of ZrB_(2)-SiC was also prepared using ZrB_(2) and SiC as raw materials through an identical process designated as ZS ceramics.Microscopic analysis of both ceramic groups revealed smaller and more uniformly distributed particles of the ZrB_(2) phase in ZBC ceramics compared to the larger particles in ZS ceramics.Both sets of ceramics underwent cyclic oxidation testing in the air at 1600℃for a cumulative duration of 5 cycles,each cycle lasting 2 h.Analysis of the oxidation behavior showed that both ZBC ceramics and ZS ceramics developed a glassy SiO_(2)-ZrO_(2) oxide layer on their surfaces during the oxidation.This layer severed as a barrier against oxygen.In ZBC ceramics,ZrO_(2) is finely distributed in SiO_(2),whereas in ZS ceramics,larger ZrO_(2) particles coexist with glassy SiO_(2).The surface oxide layer of ZBC ceramics maintains a dense structure because the well-dispersed ZrO_(2) increases the viscosity of glassy SiO_(2),preventing its crystallization during the cooling.Conversely,some SiO_(2) in the oxide layer of ZS ceramics may crystallize and form a eutectic with ZrO_(2),leading to the formation of ZrSiO_(4).This leads to cracking of the oxide layer due to differences in thermal expansion coefficients,weakening its barrier effect.An analysis of the oxidation resistance shows that ZBC ceramics exhibit less increase in oxide layer thickness and mass compared to ZS ceramics,suggesting superior oxidation resistance of ZBC ceramics.

Low-firing and temperature stability regulation of tri-rutile MgTa_(2)O_(6)microwave dielectric ceramics

A glass frit containing Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)component was used to explore the low-temperature sintering behaviors and microwave dielectric characteristics of tri-rutile MgTa_(2)O_(6)ceramics in this study.The good low-firing effects are presented due to the high matching relevance between Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass and MgTa_(2)O_(6)ceramics.The pure tri-rutile MgTa_(2)O_(6)structure remains unchanged,and high sintering compactness can also be achieved at 1150℃.We found that the Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass not only greatly improves the low-temperature sintering characteristics of MgTa_(2)O_(6)ceramics but also maintains a high(quality factor(Q)×resonance frequency(f))value while still improving the temperature stability.Typically,great microwave dielectric characteristics when added with 2wt%Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass can be achieved at 1150℃:dielectric constant,ε_(r)=26.1;Q×f=34267 GHz;temperature coefficient of resonance frequency,τ_(f)=-8.7×10^(-6)/℃.

Preparation and Spectral Properties of Er,Na∶CaF_(2) Transparent Ceramics

Er^(3+),Na^(+)co-doped CaF_(2) transparent ceramics with Er^(3+)dopant concentration of 3% and Na^(+) of 0%,0.5%,1.0%,1.5% and 2.0% were fabricated by the vacuum hot pressing method with 16 mm in diameter and 3 mm in thickness.The average grain size of the obtained Er,Na∶CaF_(2) powders varied from 28 nm to 36 nm with the shape of sphere.The effects of Na^(+) doping on the transmittance,microstructure and spectral properties of Er^(3+)∶CaF_(2) transparent ceramics were investigated.The transmittance of all the obtained ceramic samples is above 84%in the wavelength of 1000 nm.The results show that after introducing Na^(+)into Er^(3+)∶CaF_(2) transparent ceramics,charge-neutralized Er^(3+)-Na^(+) structure formed which prevent Er^(3+) from clustering.The emission spectra of Er^(3+) in CaF_(2) transparent ceramics at around 1.5 and 2.7μm could be modulated by adjusting the concentration of Na^(+) and the near-infrared fluorescence lifetime at around 1.5μm increase with the increasing of Na^(+) concentration,reaching a maximum of 56.75 ms.

Penetration resistance of Al_(2)O_(3) ceramic-ultra-high molecular weight polyethylene(UHMWPE)composite armor:Experimental and numerical investigations

To enhance the protective performance of ceramic composite armor,ballistic penetration experiments were conducted on Al_(2)O_(3) ceramic-ultra-high molecular weight polyethylene(UHMWPE)composite armor with different thickness configurations.The damage and failure modes of hard projectiles and ceramic-fiber composite targets were analyzed.The recovered projectiles and ceramic fragments were sieved and weighed at multiple stages,revealing a positive correlation between the degree of fragmentation of the projectiles and ceramics and the overall ballistic resistance of the composite targets.Numerical simulations were performed using the LS-DYNA finite element software,and the simulation results showed high consistency with the experimental results,confirming the validity of the material parameters.The results indicate that the projectile heads primarily exhibited crushing and abrasive fragmentation.Larger projectile fragments mainly resulted from tensile and shear stress-induced failure.The failure modes of the composite targets included the formation of ceramic cones and radial cracks under high-velocity impacts.The UHMWPE laminated plates exhibited interlayer separation caused by tensile waves,permanent plastic deformation of the rear surface bulging,and perforation failure primarily due to shear forces.Through extended numerical simulations,while maintaining the same areal density and configuration of9 mm Al_(2)O_(3) ceramic+12 mm UHMWPE laminated composite armor,the thickness configurations of the Al_(2)O_(3) ceramic and UHMWPE laminated backplates were varied,and various thicknesses of UHMWPE laminates were simulated as the cover layer for the ceramic panels.The simulation results indicated that the composite armor configuration of 10 mm Al_(2)O_(3) ceramic+8 mm UHMWPE composite armor increased energy absorption by13.48%.When altering the cover layer thickness,a 4 mm UHMWPE+9 mm Al_(2)O_(3)+8 mm UHMWPE composite armor demonstrated a 27.11%improvement in energy absorption,showing a relatively significant enhancement.

Physics-embedded machine learning search for Sm-doped PMN-PT piezoelectric ceramics with high performance

Pb(Mg_(1/3)Nb_(2/3))O_(3)–PbTiO_(3)(PMN-PT)piezoelectric ceramics have excellent piezoelectric properties and are used in a wide range of applications.Adjusting the solid solution ratios of PMN/PT and different concentrations of elemental doping are the main methods to modulate their piezoelectric coefficients.The combination of these controllable conditions leads to an exponential increase of possible compositions in ceramics,which makes it not easy to extend the sample data by additional experimental or theoretical calculations.In this paper,a physics-embedded machine learning method is proposed to overcome the difficulties in obtaining piezoelectric coefficients and Curie temperatures of Sm-doped PMN-PT ceramics with different components.In contrast to all-data-driven model,physics-embedded machine learning is able to learn nonlinear variation rules based on small datasets through potential correlation between ferroelectric properties.Based on the model outputs,the positions of morphotropic phase boundary(MPB)with different Sm doping amounts are explored.We also find the components with the best piezoelectric property and comprehensive performance.Moreover,we set up a database according to the obtained results,through which we can quickly find the optimal components of Sm-doped PMN-PT ceramics according to our specific needs.

超高真空环境下TC4钛合金和ZrO_(2)陶瓷的出气性能研究

内衬超薄壁真空腔体是离子加速器真空系统的核心元件,为了获得超高真空环境,对内衬材料的出气性能有较高要求。基于新型双通道出气率实验装置,完成了TC4钛合金和ZrO_(2)陶瓷在常温抽气、不同烘烤温度及烘烤结束后不同温度下的出气率实验;通过数值拟合方法获得了材料在不同加热温度下的出气率表达式;搭建了钛合金内衬超薄壁真空腔体压力实验装置,通过实验和仿真对比分析了不同工况下的压力分布。结果表明,烘烤温度越高,最终出气率越低,250℃烘烤时出气率较150℃时降低了约21%。经过高温烘烤后,当材料温度从50℃升高至210℃时,两种材料的出气率呈指数增加趋势,但钛合金的出气率低于陶瓷的出气率。常温抽气和烘烤过程中真空腔体压力梯度较小,对其进行升温时中间位置压力变化幅度较大,当温度为100℃,中间位置压力从初始值1.41×10^(-9)Pa升高至4.51×10^(-9)Pa;压力仿真结果和实验结果一致,平均相对偏差为6.86%。以上结果填补了钛合金和陶瓷出气率数据库,能够预测及评估真空腔体不同工况下的极限压力,为超高、极高真空获取提供数据支撑。

制备条件对Pt-S_2O_8^(2-)/ZrO_2-Al_2O_3异构化催化性能的影响

为了考察复合载体固体超强酸催化剂的异构化性能,以正戊烷异构化为探针反应,考察了焙烧温度、Al2O3质量分数、浸渍溶液(NH4)2S2O8的浓度、Pt质量分数、活化温度等制备条件对Pt-S_2O_8^(2-)/ZrO_2-Al_2O_3异构化催化活性的影响,并采用XRD、BET、FT-IR、TG-DTA、NH3-TPD等手段对催化剂进行了表征。结果表明,当Al2O3质量分数2.5%、Pt质量分数0.10%、0.75 mol/L(NH4)2S2O8溶液浸渍、650℃焙烧、300℃活化时,Pt-S_2O_8^(2-)/ZrO_2-Al_2O_3催化剂的异构化催化活性最高。在240℃、2.0 MPa,氢气/正戊烷的摩尔比为4,质量空速为1.0 h-1的反应条件下,该催化剂上正戊烷异构化反应的异戊烷产率为60.2%。

980nm激发下Ho^(3+)/Yb^(3+)共掺杂ZrO_2-ZnO粉末的上转换发光特性

通过固相反应法制备了Ho3+/Yb3+共掺杂ZrO2-ZnO粉末样品,重点报道了Ho3+/Yb3+共掺杂ZrO2-ZnO粉末样品在980nm激发下的上转换发光现象。在常温下测试得到的发射光谱显示3个发射峰,中心波长依次为540,671和762nm,分别对应Ho3+的5S2/5F4→5I8,5F5→5I8,5S2/5F4→5I7或5I4→5I8跃迁过程。稀土离子的掺杂浓度明显影响样品的上转换发光特性,当Ho3+浓度确定的情况下,随着Yb3+含量增大,红光强度和绿光强度先减小后增大,近红外光却先增大后减小,而绿光强度与红光强度的比值一直减小。当Yb2O3含量为4.7mol%时,随着Ho3+含量增大,各波段荧光强度均减小,而绿光强度与红光强度的比值基本不变。双对数曲线显示3个波长的上转换发光的发射过程均为双光子过程,对样品的上转换发光机制做了详细的说明。XRD显示样品的均匀性良好。

Tribological properties of nanostructured Al_2O_3-40%TiO_2 multiphase ceramic particles reinforced Ni-based alloy composite coatings

The Ni-based alloy composite coatings reinforced by nanostructured Al2O3-40%TiO2 multiphase ceramic particles were prepared on the surface of 7005 aluminum alloy by plasma spray technology. The microstructure and tribological properties of the composite coatings were researched. The results show that the composite coatings mainly consist of γ-Ni, α-Al2O3, γ-Al2O3 and rutile-TiO2 etc, and exhibit lower friction coefficients and wear losses than the Ni-based alloy coatings at different loads and speeds. The composite coating bears low contact stress at 3 N and its wear mechanism is micro-cutting wear. As loads increase to 6-12 N, the contact stress is higher than the elastic limit stress of worn surface, and the wear mechanisms change into multi-plastic deformation wear, micro-brittle fracture wear and abrasive wear. With the increase of speeds, the contact temperature of worn surface increases. The composite coating experiences multi-plastic deformation wear, fatigue wear and adhesive wear.