Automatic Damage Detection of Engineering Ceramics Ground Surface Based on Texture Analysis

Ground textures seriously interfere with the exact identification of grinding damage. The common nondestructive testing techniques for engineering ceramics are limited by their difficulty and cost. Therefore, this paper proposes a global image reconstruction scheme in ground texture surface using Fourier transform (FT). The lines associated with high-energy frequency components in the spectrum that represent ground texture information can be detected by Hough transform (HT), and the corresponding high-energy frequency components are set to zero. Then the spectrum image is back-transformed into the spatial domain image with inverse Fourier transform (IFT). In the reconstructed image, the main ground texture information has been removed, whereas the surface defects information is preserved. Finally, Canny edge detection is used to extract damage image in the reconstructed image. The experimental results of damage detection for the ground texture surfaces of engineering ceramics have shown that the proposed method is effective.

MECHANOCHEMICAL POLISHING OF ENGINEERING CERAMICS

Polishing ceramics with a bonded diamond abrasive and fine-grain soft abrasives wascarried out. The different material removeal mechanism of the two kinds of abrasives was pointedout through teh measurement of the material removal rate vs. polishing time and polishing speedrespectively. XPS examination proved that a mechanochemical reaction took place when polishingSialon, a kind of non-oxide ceramics ,with the CrObonded abrasives disc.

RESEARCH OF MACHINING SURFACE QUALITY OF ENGINEERING CERAMICS

Surface quality is an important sublect in the study of machining technology. Because thesurface quality of the ceramic parts has direct effect on their life and reliability, to improve the reliability of structural ceramic parts is an urgent problem which needs to be solved for their furtherwidespread. The authors have done a systematic investigation in the macrostate, geometrical to-pography, surface roughness, deteriorative layer, residual stress and phase change of the machiningsurface of engineering ceramic zirconia and sialon ceramics. Some findings and conclusions of im-portant referential value have been obtained.

Enhancing energy storage efficiency in lead-free dielectric ceramics through relaxor and lattice strain engineering

Dielectric capacitors with high power density and fast charge-discharge speed play an essential role in the development of pulsed power systems.The increased demands for miniaturization and practicality of pulsed power equipment also necessitate the development of dielectric materials that possess high energy density while maintaining ultrahigh efficiency(η).In particular,ultrahigh efficiency signifies minimal energy loss,which is essential for practical applications but challenging to effectively mitigate.Here,we demonstrate a strategy of incorporating heterovalent elements into Ba(Zr_(0.1)Ti_(0.9))O_(3),which contributes to achieving relaxor ferroelectric ceramics and reducing lattice strain,thereby improving the comprehensive energy storage performance.Finally,optimal energy storage performance is attained in 0.85Ba(Zr_(0.1)Ti_(0.9))O_(3)-0.15Bi(Zn_(2/3)Ta_(1/3))O_(3)(BZT-0.15BiZnTa),with an ultrahighηof 97.37%at 440 kV/cm(an advanced level in the lead-free ceramics)and an excellent recoverable energy storage density(Wrec)of 3.74 J/cm^(3).Notably,the BZT-0.15BiZnTa ceramics also exhibit exceptional temperature stability,maintaining fluctuations in Wrec within∼10%andηconsistently exceeding 90% across the wide temperature range of−55℃ to 160℃,and under a high electric field of 250 kV/cm.All these features demonstrate that the relaxor and lattice strain engineering strategies have been successful in achieving high-performance lead-free ceramics,paving the way for designing high-efficiency dielectric capacitors with a wide temperature range.

Preparation of CePO_4-coated zirconia ceramics and their mechanical behavior

Tetragonal ZrO2-3 mol% Y2O3 （3Y-TZP） coated with CePO4 was synthesized by a co-precipitation method and the effects of CePO4 content and sintering temperature on its mechanical properties were investigated. The microstructure and phase composition of the products were characterized using scanning and transmission electron microscopy as well as X-ray diffraction, respectively. The machinability index of CePO4-coated zirconia was calculated to be 1.05 when the CePO4 content is 25 wt.%. The sample hardness, bending strength and fracture toughness are 7.08 GPa, 457.85 MPa and 9.75 MPa m1/2, respectively, when the sintering temperature is 1400°C. The results show that as-prepared CePO4-coated 3Y-TZP ceramics are highly suitable biomaterials for dental applications and are expected to be used in a com-puter-aided design and computer-aided manufacturing （CAD/CAM） system to make dental crowns or bridge prostheses in a one-step sinter-ing process.

Sea Urchin Spines as a Model-System for Permeable,Light-Weight Ceramics with Graceful Failure Behavior.Part Ⅱ.Mechanical Behavior of Sea Urchin Spine Inspired Porous Aluminum Oxide Ceramics under Compression

Sea urchin spines were chosen as a model system for biomimetic ceramics obtained using starch-blended slip casting. Porous alumina ceramics with cap-shaped layers with different alternating porosities were found to have superior fracture behavior under bulk compression compared to ceramics with uniform porosity.They fail in a cascading manner,absorbing high amounts of energy during extended compression paths.The porosity variation in an otherwise single phase material mimicks the architectural microstructure design of sea urchin spines of Heterocentrotus mammillatus,which are promising model materials for impact protection.

Three-dimensionally Perforated Calcium Phosphate Ceramics

Porous calcium phosphate ceramics were produced by compression molding using a special mold followed by sintering. The porous calcium phosphate ceramics have three-dimensional and penetrated open pores 380-400μm in diacneter spaced at intervals of 200μm. The layers of the linear penetration pores alternately lay perpendicular to pore direction. The porosity was 59%-65% . The Ca/ P molar ratios of the porous calcium phos phate ceramics range from 1.5 to 1.85. A binder cantaining methyl cellulose was most effective for preparing the powder compact among vinyl acetate, polyvinyl alcohol, starch, stearic acid, methyl cellulose and their mixtures . Stainless steel, polystyrene, nylon and bamboo were used as the long columnar dies for the penetrated open pores. When polystyrene, nylon and bamboo were used as the long columnar male dies, the dies were burned oat during the sintering process. Using stainless steel as the male dies with the removal of the dies before heat treatment resulted in a higher level of densification of the calcium phosphate ceramic.

Effects of Sm Doping to Improve the Thermoelectric Properties of ZnO Ceramics

A series of Sm doped ZnO based thermoelectric materials were prepared by mechanical alloying and spark plasma sintering.The effects of Sm doping on ZnO based thermoelectric materials were systematically studied by means of electrical and thermal properties tests combined with first principles calculations of energy band,density of states and elastic constants.The experimental results show that the substitution of Sm at Zn site could cause the valence band and conduction band moving down,and the 4f orbitals of Sm could contribute to the increase of the density of states near the Fermi level,corresponding to the increase of carrier concentration and electrical conductivity.The substitution of Sm at Zn site could cause the decrease of effective mass and Seebeck coefficient.The substitution of Sm at Zn site could lead to the decrease of Young's modulus and lattice thermal conductivity,which contribute to the decrease of thermal conductivity.Finally,the highest dimensionless thermoelectric figure of merit(ZT)value has been increased to 0.346,which is 3.48 times as pristine ZnO.

Improvement on Performances of Internal Combustion Engine Using the Technology of Ceramic Coating

This paper introduces a new technology of using ceramic coating on piston rings of an internal combustion engine, and the comparison of mechanical efficiency and performances of an actual engine before and after the application of ceramic coating on the piston rings. The experimental results show that the mechanical efficiency and power output are enhanced by 4% and 2.6%, respectively, with fuel consumption reduced by (2.9%.) Further studies on coating processing and coating materials as well as the reliability and durability will be of great significance in the application and popularization of the new technology.

Towards Long-Life Replacement Joint Prostheses - A Surface Engineering Approach

How to improve the wear resistance of bearing surfaces, hereby achieving long life of orthopaedic joint prostheses has long been a technical challenge with much fundamental interest and social and economic impacts. Surface engineering has been emerging as one of the most promising technologies to improve the tribological properties of biomedical materials. A current area of research within the Birmingham Surface Engineering Group has been directed at developing novel surface engineering technologies for biomedical materials towards long-life joint prostheses. Following a brief introduction, the author reports their recent progress in the surface engineering of biomedical materials particular for joint prosthesis. The potential of these innovative surface engineering technologies in enhancing the performance of oral and maxillofacial implants and surgical devices is also discussed.

Outstanding electromechanical performance in piezoelectric ceramics via synergistic effects of defect engineering and domain miniaturization

Piezoelectric ceramics with high mechanical quality factor Q_(m) and large piezoelectric coefficient d_(33) are urgently required for advanced piezoelectric applications.However,obtaining both of these prop-erties simultaneously remains a difficult challenge due to their mutually restrictive relationship.Here 0.5Pb(Ni_(1/3)Nb_(2/3))O_(3)-0.5Pb(Zr_(0.3)Ti_(0.7))O_(3) piezoceramic with tetragonal(T)-rich MPB is designed as a matrix to construct the defect engineering by doping low-valent Mn ions.The strong coupling of defect dipole and T-rich phase can effectively hinder the rotation of P_(s),restrict domain wall motion and improve Q_(m).At the same time,the substituted Mn ions will introduce local random field,destroying the long-range or-dering of ferroelectric domain and reducing domain size.The miniaturized domain structure can increase poling efficiency and inhibit the reduction of d_(33).Guided by this strategy,Q_(m) has increased by more than 10 times and d_(33) has only decreased by about 25%.The optimized electromechanical performance with Q_(m)=822,d_(33)=502 pC/N,k_(p)=0.55 and tanδ=0.0069 can be obtained in the present study.

沥青路面热反射封层材料降温性能与机理研究

热反射型沥青路面封层可有效降低沥青路面温度,从而避免车辙病害。采用中空陶瓷微珠(HCB)和中空玻璃微珠(HGB)两种热反射材料,分别与雾封层和稀浆封层两种预防性养护技术结合,制备沥青路面热反射封层材料。利用扫描电子显微镜(SEM)与X射线衍射(XRD)对两种热反射材料的微观形貌与化学组成进行表征;通过室内降温试验对不同封层形式与不同热反射材料的降温效果进行研究,利用室外降温试验对热反射稀浆封层的降温效果进行研究,并探讨了HCB与HGB在封层中的热反射机理。研究结果表明:SEM与XRD试验显示HCB与HGB微观结构与化学组成使其有利于降低路面温度;室内降温试验表明,含8%HGB的热反射稀浆封层温度可降低2.6℃,含100%HGB热反射雾封层温度可降低1℃,热反射稀浆封层降温效果优于热反射雾封层,并且在相同掺量下,添加HGB的降温效果优于添加HCB;室外降温试验结果表明,相比未掺加热反射材料的稀浆封层,含8%HGB的热反射稀浆封层的降温效果可达5.2℃;相比未加铺热反射稀浆封,含8%HGB的热反射稀浆封层的降温效果达到3.3℃,热反射稀浆封在具备养护功能的同时也可以达到降温效果。研究结果可为公路关键路段的日常预防性养护提供一种可行的车辙病害解决方案。

掺废弃陶瓷纤维增强水泥基复合材料抗冻性能

采用陶瓷粉替代一部分水泥,陶瓷砂替代普通河砂,在水泥基材料中掺入不同体积掺量的聚乙烯醇(Polyvinyl Alcohol,PVA)纤维,制成掺入PVA纤维和陶瓷粉的水泥基复合材料砂浆试件。通过冻融循环试验分析质量损失率、相对动弹性模量的变化,并通过电化学阻抗测试和扫描电子显微镜观察研究砂浆试件的冻融损伤规律。结果表明:陶瓷粉中SiO_(2)和Al_(2)O_(3)含量远大于水泥中相应含量,且粒径小于20μm的颗粒占82.3%,火山灰效应和微集料效应可改善试件的密实度,提升复合材料的抗冻性能;PVA纤维掺量为2.2%,陶瓷粉掺量为30%,冻融循环100次时砂浆试件质量损失率最小,相对动弹性模量最大,连续导电路径电阻最大,冻融损伤程度最小;纤维和基体的接触面是该复合材料抗冻薄弱部位。

单向陶瓷基复合材料循环迟滞模型研究

为了模拟单向陶瓷基复合材料(Ceramic matrix composites, CMCs)在受到疲劳加载时的应力-应变关系,建立不同循环次数、不同疲劳峰值载荷的单向陶瓷基复合材料疲劳迟滞回线理论模型。将加载过程分为4个阶段且脱粘区域由新正向滑移区域、旧正向滑移区域和反向滑移区域组成,卸载过程滑移区域分为新正向滑移区域和反向滑移区域。分析了加载和卸载各个区域纤维轴向应力分布,推导了4个加载阶段和卸载对应的疲劳应力应变关系。预测了单向陶瓷基复合材料在不同峰值应力和不同循环的疲劳迟滞曲线,发现预测结果与文献中实验结果吻合较好。

Designing highly transparent cerium doped Y_(2)O_(3) ceramics with high mechanical and thermal properties for UV-shielding in extreme conditions

Ultraviolet(UV)radiation poses risks to both human health and organics.In response to the urgent demand for UV-shielding across various applications,extensive endeavors have been dedicated to developing UV-shielding materials spanning from wide-bandgap semiconductors to organo-inorganic composite films.However,existing UV shielding materials,though suitable for daily use,cannot meet the demands of extreme conditions.In this work,we incorporated CeO_(2)as a UV absorber into Y_(2)O_(3)transparent ceramics for UV-shielding.The effect of CeO_(2)concentration on the optical,mechanical,and thermal properties of Y_(2)O_(3)ceramics was systematically investigated.These findings indicate that CeO_(2)serves not only as a UV absorber but also as an effective sintering aid for Y_(2)O_(3)transparent ceramics.The 5 at%Ce-doped Y_(2)O_(3)transparent ceramics exhibit the optimal optical quality,with in-line transmittance of~77%at 800 nm.The introduction of Ce shifted the UV cutoff edge of Y_(2)O_(3)transparent ceramics from 250 to 375 nm,which was attributed to the visible band absorption of Ce^(4+).This shift grants UV shielding capabilities to Y_(2)O_(3)transparent ceramics,resulting in 100%shielding for ultraviolet C(UVC,100-280 nm)and ultraviolet B(UVB,280-320 nm)and~95%shielding for ultraviolet A(UVA,320-400 nm).The service stability(optical properties)under various corrosive conditions(acid,alkali,UV irradiation,and high temperature)was investigated,confirming the excellent stability of this transparent ceramic UV-shielding material.A comparison of the performance parameters of transparent ceramics with those of traditional UV shielding materials such as glasses,films,and coatings was conducted.Our work provides innovative design concepts and an effective solution for UVshielding materials for extreme conditions.

箱体型正压式平板负离子抗菌陶瓷膜MBR在城市新鲜垃圾渗滤液处理应用实例

山东某垃圾焚烧厂中产生的新鲜垃圾渗滤液有机物和氨氮浓度高,同时含有多种重金属,属于难处理的废水。本工程采用气浮预处理+两级UASB+A/O+平板式MBR膜过滤+后续深度处理(纳滤+反渗透)工艺。厌氧处理阶段采用投加零价铁来提高处理效果。MBR工艺采用箱体型正压式优化结构,比传统的浸没式结构能提高膜通量和优化操作。MBR膜采用能抑菌杀菌的负离子抗菌平板陶瓷膜,具有膜通量大,缓解膜污染能力强的特点。工程运行表明,出水水质低于≤生活垃圾卫生填埋场污染控制标准≥(GB 16889-2008)表3中的标准要求,即COD≤60 mg/L,BOD_(5)≤20 mg/L,ρ(氨氮)≤8 mg/L,ρ(总氮)≤20 mg/L,ρ(SS)≤2.0 mg/L等。工程投资总成本500万左右。吨水成本将核算后为14.9元。

Achieving ultrahigh electromechanical properties with high TC in PNN-PZT textured ceramics

<001>textured Pb(Ni_(1/3)Nb_(2/3))O_(3)-PbZrO_(3)-PbTiO_(3)(PNN-PZT)ceramics were prepared by templated grain growth(TGG)technique using 0.36PNN-x PZ-(0.64-x)PT(x=0.23,0.25 and 0.27)powder matrix.Optimum template content was derived to achieve the best electromechanical properties of textured ceramics.The piezoelectric coefficient d33=1165 pC/N,Curie temperature T_(C)=197°C,longitudinal mode electrome-chanical coupling factor k33=0.86 and a very large effective piezoelectric strain coefficient d_(33)^(*)=2041 pm/V were simultaneously achieved at the morphotropic phase boundary(MPB)composition(x=0.25)with 3 vol.%BaTiO_(3)(BT)templates.Domain structures of textured ceramics were analyzed in detail to reveal the origin of these high piezoelectric and electromechanical properties.

航空发动机热端部件表面高温陶瓷涂层性能优化

目的 对航空发动机热端部件表面长效防护涂层W-200进行改进,研制高温稳定性更好且不易崩瓷的高温合金表面新型高温陶瓷涂层,解决W-200涂层在部分高温合金表面暴露出的易崩瓷、剥落问题。方法 通过调整膨胀系数、软化温度、析晶温度,来研制新型耐高温玻璃和耐高温填料,并制备新的高温陶瓷涂层浆料。结果 所研制的新型高温陶瓷涂层W-400能够满足在高温合金表面1 150~1 230℃顺利烧结,且具有更大的膨胀系数,可与高温合金基材的膨胀系数更匹配。同时,W-400的析晶温度区间为868~1 213℃,在析晶温度区间,涂层较W-200具有更好的高温稳定性,以及更优的抗热震、抗剥落性能,并可覆盖实际应用的温度范围。结论 新型高温陶瓷涂层W-400解决了目前W-200高温陶瓷涂层在航空发动机高温合金热端部件表面烧结后易崩瓷的问题。根据本项目的研究基础,对未来可研制出能够在其他金属表面1 250~1 400℃顺利烧结的耐温更高的新型高温陶瓷涂层提供了可能性。

工程陶瓷圆弧成形磨削力预测与实验研究

圆弧成形磨削是难加工零件复杂型面的加工方法,对其磨削力的研究有利于改善工程陶瓷的表面质量。基于圆弧砂轮的结构特点及尺寸趋近思想对陶瓷材料圆弧成形磨削力进行预测。通过研究磨粒对工程陶瓷的去除机制,提出建立单颗磨粒滑擦、塑性及脆性去除磨削力模型。基于砂轮磨粒尺寸与分布差异,利用概率统计方法对磨削中不同去除方式的有效磨粒数进行探讨,进而实现圆弧成形磨削力理论模型的构建。最后通过磨削力实验对理论模型进行验证。结果表明:法向磨削力和切向磨削力理论值与实验值平均误差分别为8.793%和9.986%;磨削力随着磨削深度及进给速度的增加而增加,随着砂轮速度的增加而减小。

基于陶瓷基复合材料铠甲的涡轮导叶热防护研究

为了加速推进我国高推重比航空发动机研制进程,突破已有高温合金+气膜冷却架构对涡轮叶片承温能力的限制,以及解决陶瓷基复合材料(CMC)涡轮叶片制造难度过大的问题,本文提出了一种在涡轮导向叶片前缘镶嵌CMC铠甲的热防护方案,并通过多工况下的数值仿真,研究了其与典型气膜冷却相比在流动和传热上的差异。相较于后者,在相同的冷气压比1.03下,采用该CMC铠甲结构可以使得冷气质量流量显著降低58%;同时可以利用CMC铠甲与冷气的共同作用,使前缘区的叶片基体冷却效率由0.50显著提升至0.85;通过研究CMC材料导热系数对其自身温度分布影响,探讨了避免铠甲失效的极限燃气温度,相对保守的结果为2017K。有望通过对CMC材料和铠甲结构的进一步性能优化来满足第五代先进航空发动机的需求。