Effect of 3 mol% Yttria Stabilized Zirconia Addition on Structural and Mechanical Properties of Alumina-Zirconia Composites

Alumina-Zirconia (Al2O3-ZrO2) composites especially Zirconia Toughened Alumina (ZTA) shows better mechanical properties over alumina. Al2O3-ZrO2 composites were prepared by powder compaction method varying 3 mol% yttria stabilized zirconia (3Y-ZrO2) content from 0 to 20 vol% using small amount of MgO as sintering aid. The composites were sintered for two hours in air at 1580°C. At this temperature maximum density was achieved 99.31% of theoretical density for composite containing 20 vol% 3Y-ZrO2. Density measurement of sintered composites was carried out using Archimedes’s method. Hardness and fracture toughness measurement was carried out using Vickers indentation. Phase content and t-ZrO2 retention were detected by means of X-ray diffraction (XRD). Microstructure of the composites and grain size of alumina and zirconia was determined by Scanning Electron Microscopic (SEM) analysis. Maximum microhardness (17.46 GPa) was achieved for composite containing 5 vol% ZrO2 and maximum flexural strength (684.32 MPa) and fracture toughness (10.33 MPam0.5) was achieved for composite containing 20 vol% of 3Y-ZrO2. The aim of the present work is to investigate the optimum 3Y-ZrO2 content for obtaining maximum density, microhardness, flexural strength and fracture toughness of Al2O3-ZrO2 composites.

Impact-abrasive Wear Behavior of ZTA and NbC Reinforced Fe60 Matrix Composites

The impact-abrasive wear behavior of ZTA(zirconia toughened alumina)particle(ZTAp)and NbC particle(NbCp)reinforced Fe60 matrix composites(ZTAp-NbCp/Fe60)were investigated.Specimens of pure Fe60 matrix material,NbCp reinforced Fe60 composite(NbCp/Fe60)and ZTAp-NbCp/Fe60 with different contents of ZTAp were prepared through vacuum sintering and tested on an MLD-10B Impact Wear Rig.As revealed by the results,NbCp could strengthen Fe60 matrix,and had fine grain strengthening effect on Fe60matrix.When the mass fraction of ZTAp was 5%-15%,the impact-abrasive wear performance of ZTAp-NbCp/Fe60 composites was better than that of Fe60 and NbCp/Fe60.When the mass fraction was 15%,the ZTApNbCp/Fe60 had the best performance.ZTAp could weaken the impact and wear effect of abrasive particles on the composite and protect the matrix.Cracks occured at the interface and at defects in the ZTAp.The former leaded to ZTAp shedding,while the latter leaded to ZTAp fracturing.In both cases,the performance of the composite material would decrease.

Mechanical Properties of a new Dental all-ceramic Material-zirconia Toughened Nanometer-ceramic Composite

目的 :口腔全瓷修复体以其独特优越性受到医患青睐 ,但脆性问题一直限制其应用范围及使用可靠性。本研究旨在研制用于玻璃渗透全瓷修复的纳米氧化锆增韧陶瓷并全面检测评价其力学性能。方法 :采用化学共沉淀与球磨相结合的方法合成纳米氧化锆增韧陶瓷 (α -Al2 O3 /nZrO2 ceramicspowder ,W) ,扫描电镜评价陶瓷材料的粉体形态特征及粒度分布。预制氧化锆含量不同的陶瓷粉体 (5wt% ,10wt% ,15wt%and 2 0wt% ) ,采用粉浆涂塑技术将材料制成标准试件 ,并在不同温度下 (12 0 0～ 16 0 0℃ )烧结成型 ,用三点弯曲法及单边刀口梁法检测材料试件的抗弯强度和断裂韧性。结果 :1)α -Al2 O3 /nZrO2 材料粉体粒度分布范围大致为 0 .0 2～ 3.0 μm ,其中超细粉体 (低于 0 .1μm)占 2 0 % ;2 )不同烧结温度组试件的力学强度有显著差异 (P <0 .0 5 ) ,14 5 0℃和 16 0 0℃组高于12 0 0℃组 ;3)相同烧结温度下不同氧化锆含量组材料强度有显著差异 ,一定范围内氧化锆含量增高有助于材料的增韧增强。结论 :本研究所研制的纳米氧化锆增韧陶瓷材料组分配比及微观特征能增韧增强材料 。

Effect of Universal Primers on the Tensile Bond Strength between Zirconia and Resin Composites

This study aimed to evaluate the effects of universal primers on the tensile bond strength between zirconia and resin composites.Zirconia specimens were divided into five groups based on the surface treatment with the following primers:MP(Monobond Plus),SU(ScotchBond Universal),AZ(AZ Primer),BM(Beauty bond Multi),and BL(Bondmer Lightless).After priming,stainless steel rods were bonded to the zirconia specimens with composite resin.The tensile bond strength test was performed:stored at room temperature for 1 day;stored in distilled water at 37°C for 7 days;and underwent thermal cycling.The BL group demonstrated a significantly higher tensile bond strength than other groups when stored at room temperature for 1 day(p<0.05).The primer that acted via chemical polymerization appeared to be most effective in improving the bond strength between the two materials in this study.

Supramolecular-templated synthesis of mesoporous silica-zirconia nanocomposite

Mesoporous SiO2-ZrO2 nanocomposite was successfully prepared by using supramolecular triblock copolymer as the template through evaporation-induced self-assembly approach. The textural and structural properties were characterized by X-ray diffraction, nitrogen adsorption analysis, and transmission electron microscope. Comparison between pure mesoporous silica and mesoporous silica-zirconia nanocomposite was also presented in this work. The surface area, pore size, and pore volume decreased as the Zr doping in the mesoporous silica framework. But the obtained nanocomposite maintained the cubic Im3m-type mesoporous structure.

Microstructure and properties of composite of stainless steel and partially stabilized zirconia

To fabricate the metal-ceramics multi-layer hollow functionally gradient materials(FGMs) that might meet the requirement of repeated service and long working time of high temperature burners, such as spacecraft engine, the microstructure and properties of composite of stainless steel and partially stabilized zirconia were investigated. Samples of different proportions of stainless steel to partially yttria-stabilized zirconia were fabricated by powder extrusion and sintering method. Shrinkage, relative density, microstructure, micro-Vickers hardness, compression strength, bending strength, fractography morphology and electrical resistivity of sintered samples with different proportions of stainless steel were measured. The results show that threshold of metallic matrix composite(MMC) is approximately equal to 60%(volume fraction) stainless steel. The samples with 0 to 50%(volume fraction) stainless steel indicate ceramic brittleness and non-cutability, and the samples with 70% to 100%(volume fraction) stainless steel indicate metallic plasticity and cutability.

The Development and Characterization of Zirconia-Silica Sand Nanoparticles Composites

The present study aims to develop zirconia-Silica sand nanoparticles composites through powder processing route and to study the physical properties, mechanical properties and microstructure of the composites. Zirconia based silica sand nanoparticles composite with 5, 10, 15 and 20 wt.% were developed through powder processing technique and sintered at 1500 ℃ for two hours. A decreasing trend of green density however an improvement in sintered density was observed. Also the addition of silica sand nanoparticles with 20 wt.% increased the hardness up to 12.45 GPa and microstructures indicated the diffusion mechanism of silica sand nanoparticles into pore sites of the composites.

Effect of ZrO_2-nitrides Composite Powder Addition on Oxidation Resistance of Al_2O_3-C Refractories

Oxidation of carbon is the main problem or Al2O3 - C refractories. ZrO2 - nitrides composite powder was synthesized through carbothermal reduction and nitridation （CRN） of zircon. The effect of ZrO2 - nitrides composite powder addition on oxidation resistance of the Al2O3 - C refractories was investigated by measuring the thickness of oxidation layer. Phase compositions of the Al2O3 - C refractories before and after oxidation were investigated by X-ray diffraction （ XRD ）. Results show that the oxidation resistance of the Al2O3 - C refractories can be obviously improved by adding the synthesized ZrO2 - nitrides composite powder. The formation of mullite and zircon in the oxidation layer results in the densification of oxidation layer, which prevents oxygen diffusion and bnproves the oxidation resistance of the Al2O3 - C refractories.

Mechanical Behaviors of ZrO_2-Al_2O_3 Ceramic Composites with Y_2O_3 as Stabilizer

The ZrO2-Al2O3 ceramic composites were prepared by appropriate techniques with commercial ZrO2 and Al2O3 powders as raw materials and Y2O3 as stabilizer. The results indicate that with the introduction of Al2O3 into the ZrO2 matrix where the quantity of additive Y2O3 is 3.5% (mole fraction), the growth of ZrO2 grains is efficiently inhibited, which helps the ZrO2 grains exist in a metastable tetragonal manner; thus higher strength and toughness are acquired. When the content of alumina is 20% (mass fraction), the bending strength and fracture toughness of the composites are 676.7 MPa and 10 MPa·m1/2 respectively, the mechanical behaviors are close to those prepared with ZrO2 and Al2O3 powders synthesized through wet chemical approach. The mechanical behaviors of the composites are well improved owing to the dispersion toughening of alumina grains and phase transformation toughening of zirconia grains.

Influences of ZrO_2-SiC Composite Powder and Commercial SiC on Properties of Al_2O_3-C Refractories

In order to improve oxidation resistance and ther- mal shock resistance of Al2O3-C refractories, two groups of specimens were prepared with phenolic resin as binder, adding 0, 2 wt% , 4 wt% and 6 wt% commercial SiC or ZrO2-SiC composite powder synthesized from zircon respectively to Al2O3- C refractories, pressing at 200 MPa, drying fully at 250℃, and then carbon embedded firing at 1400℃ for 2 h. Oxidation resistance and thermal shock resistance were researched, phase composition was analyzed by XRD. The results showed that the oxidation of SiC in additives could protect carbon in specimens effectively and thus decreased the mass loss ratio and oxidation area, and improved the oxidation resistance of the specimen. Thermal shock resistance was improved owing to the micro crack toughening of ZrO2 and grain toughening of SiC. In this experiment, the specimens with 6 wt% ZrO2 -SiC composite powder or 6 wt% SiC powder had the best oxidation resistance and thermal shock resistance.

Modeling mechanical behaviors of composites with various ratios of matrixeinclusion properties using movable cellular automaton method

Two classes of composite materials are considered: classical metaleceramic composites with reinforcing hard inclusions as well as hard ceramics matrix with soft gel inclusions. Movable cellular automaton method is used for modeling the mechanical behaviors of such different heterogeneous materials. The method is based on particle approach and may be considered as a kind of discrete element method. The main feature of the method is the use of many-body forces of inter-element interaction within the formalism of simply deformable element approximation. It was shown that the strength of reinforcing particles and the width of particle-binder interphase boundaries had determining influence on the service characteristics of metaleceramic composite. In particular, the increasing of strength of carbide inclusions may lead to significant increase in the strength and ultimate strain of composite material. On the example of porous zirconia ceramics it was shown that the change in the mechanical properties of pore surface leads to the corresponding change in effective elastic modulus and strength limit of the ceramic sample. The less is the pore size, the more is this effect. The increase in the elastic properties of pore surface of ceramics may reduce its fracture energy.

Effect of Al_2O_3-ZrO_2 Composite Powder on Thermal Shock Resistance of ZrO_2 Sizing Nozzles

ZrO2 sizing nozzles with a basic Jormulation were prepared using 45% （by mass, the same hereinafter ） （ Mg, Y） - PSZ aggregate, 55% （ Mg, Y） - PSZ fines and 5% PVA binder. Al2O3 - ZrO2 composite powders （ 3%, 6%, 9% and 12% ） prepared by sol - gel method were added to replace the equal amount of （ Mg, Y） - PSZfines. Effects of Al2O3 - ZrO2 composite powders on physical properties, phase composition and microstructure of the ZrO2 sizing nozzles were studied. The results show that： the performances of the modified sizing nozzles with 3% Al2O3 - ZrO2 composite powder are better than those of the nobles without composite powder used in current production process, and the thermal shock resistance of the ,former nozzles is six times of that of the latter one.

Steady polarization process modelling of noble metal-electrolyte cermet composite electrode

Cermet composites containing mixture of noble metal phase and electrolyte phase are the state-of-the-art electrode materials used for electrochemical sensor and solid oxide fuel cell(SOFC). A steady polarization model was developed. The model was based on electronic and ionic transfer process together with the electrochemical reaction regardless of mass transport in the electrode. The modelling results can help to understand the electrochemistry of cermet composite electrode.

Functionally graded Al_2O_3-ZrO_2 composite prepared by centrifugal slip casting and its mechanical properties

Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thickness.

纤维桩、纳米复合树脂结合氧化锆烤瓷冠修复牙楔状缺损的效果及对龈沟液炎性介质水平、美学评分的影响

目的探究纤维桩、纳米复合树脂结合氧化锆烤瓷冠修复牙楔状缺损的效果及对龈沟液(GCF)炎性介质水平、美学评分的影响。方法选择2018年4月至2021年6月收治的96例牙楔状缺损患者为研究对象,以随机数字表法将其分为对照组和观察组,每组48例。对照组接受金属桩核结合金属烤瓷冠修复,观察组实施纤维桩、纳米复合树脂结合氧化锆烤瓷冠修复。比较两组的修复效果。结果观察组的口腔致病菌检出率低于对照组,修复成功率高于对照组(P<0.05)。修复后,观察组GCF中的神经激肽A(NKA)、组织基质金属蛋白酶抑制剂-1(TIMP-1)、基质金属蛋白酶-9(MMP-9)及白细胞介素-8(IL-8)水平均低于对照组(P<0.05)。修复后,观察组的红色美学指数(PES)、白色美学指数(WES)评分均高于对照组(P<0.05)。修复后,观察组的GCF量及碱性磷酸酶(ALP)、天冬氨酸转氨酶(AST)水平均低于对照组(P<0.05)。结论纤维桩、纳米复合树脂结合氧化锆烤瓷冠修复牙楔状缺损可改善GCF量及GCF中炎性介质、ALP、AST表达,提高修复成功率及美学评分。

纤维桩+复合树脂+氧化锆全瓷冠修复根管治疗后后牙楔状缺损的疗效分析

目的:探究纤维桩+复合树脂+氧化锆全瓷冠修复根管治疗后后牙楔状缺损患者的效果及美观满意度。方法:纳入2022年1月-2023年1月在笔者医院就诊的102例后牙楔状缺损患者,根据患者自主选择意愿分为研究组(n=50)和对照组(n=52),对照组行金属桩核+金属烤瓷冠修复,研究组行纤维桩+复合树脂+氧化锆全瓷冠修复。6个月后,对比两组临床疗效,观察两组牙周健康情况(牙龈指数、菌斑指数、龈沟出血指数),检测牙周炎症[肿瘤坏死因子-α(Tumor necrosis factor-α,TNF-α)、白细胞介素-4(Interleukin-4,IL-4)、白细胞介素-6(Interleukin-6,IL-6)],调查美观满意度[美国公共健康服务标准(United states public health service,USPHS)]和实用度(咀嚼功能、咬合情况、语言功能),比较两组并发症发生情况。结果:治疗后,研究组治疗有效率达92.00%,高于对照组的76.92%(P<0.05);两组牙周健康相关指数及TNF-α、IL-4、IL-6均较治疗前降低,且研究组降低幅度大于对照组(P<0.05);治疗后,研究组牙齿表面形态、色泽协调性、边缘着色满意度均高于对照组(P<0.05),两组咀嚼功能、咬合情况、语言功能均较治疗前提高,但差异无统计学意义(P>0.05);两组并发症发生率比较治疗组低于对照组(P<0.05)。结论:采用纤维桩+复合树脂+氧化锆全瓷冠修复根管治疗后后牙楔状缺损能够减轻炎症反应,提升患者牙周健康,增加美观满意度及实用度,疗效显著,安全性高。

ZrO_(2)增强聚合物先驱体SiCNO复合陶瓷的制备和力学性能

聚合物先驱体陶瓷(polymer-derived ceramics,PDCs)技术具有制造简单、成分可调等优点,为制备新型陶瓷提供了有效途径。然而,由于热解过程中微小分子的逃逸形成孔洞缺陷,先驱体技术制备的无定形聚合物衍生SiCNO陶瓷(PDCs-SiCNO陶瓷)的力学性能较差。为解决上述问题,通过向陶瓷基体添加第二相(颗粒强化)来实现增强先驱体陶瓷。对聚乙烯基硅氮烷(PVSZ)和ZrO_(2)进行先球磨后热解,制备ZrO_(2)颗粒增强PDCs-SiCNO复合陶瓷(PDCs-SiCNOZrO_(2)),研究PDCs-SiCNO-ZrO_(2)复合陶瓷的结构和力学性能。结果表明:引入的ZrO_(2)填料作为增强体嵌入SiCNO陶瓷基体中,不仅能有效降低线收缩率,还能大幅提高PDCs-SiCNO-ZrO_(2)复合陶瓷的力学性能。添加10%(质量分数)ZrO_(2)的PDCs-SiCNO-ZrO_(2)复合陶瓷的弯曲强度和压缩强度分别为197.03 MPa和375.2 MPa,比PDCs-SiCNO陶瓷高出64%和267%,其硬度值最高可达20.92 GPa,断裂韧度达到2.76 MPa·m^(1/2)。适当含量ZrO_(2)的加入有助于提升PDCsSiCNO陶瓷基体的致密化程度,从而提升了PDCs-SiCNO-ZrO_(2)复合陶瓷的力学性能。

二氧化锆全瓷嵌体、钴铬合金烤瓷全冠修复、复合树脂充填修复牙列缺损对牙周指数、致病菌的影响

目的比较分析二氧化锆全瓷嵌体、钴铬合金烤瓷全冠修复、复合树脂充填修复牙列缺损对牙周指数、致病菌的影响。方法选取2020年1月-2022年9月期间在河南省洛阳市第六人民医院接受修复治疗的80例牙列缺损患者。将修复治疗方案作为分组依据,其中选择复合树脂充填修复治疗为A组(n=28)、二氧化锆全瓷嵌体修复为B组(n=27)、钴铬合金烤瓷全冠修复治疗为C组(n=25)。对比不同修复方案临床效果、牙周指数、致病菌情况及患者对修复治疗效果满意度。结果B组、C组治疗有效率高于A组,差异有统计学意义(P<0.05),BC两组修复有效率组间对比差异无统计学意义(P>0.05)。治疗后,B组牙龈出血指数(BI)和牙龈炎症指数(GI)指标均低于C组、A组,而C组低于A组,差异有统计学意义(P<0.05),B组菌斑指数(PLI)指标低于A组,差异有统计学意义(P<0.05),C组与A组PLI指标对比差异无统计学意义(P>0.05)。B组、C组在齿垢密螺旋体、具核酸杆菌、卟啉单胞菌、福赛斯坦纳菌和伴放线嗜血杆菌检出率均低于A组,且B组检出率低于C组,差异有统计学意义(P<0.05),三组中间普氏菌检出率对比差异不显著(P>0.05)。结论在牙列缺损临床修复治疗时,相比复合树脂充填修复而言,选择二氧化锆全瓷嵌体、钴铬合金烤瓷全冠修复效果更为理想,尤其是二氧化锆全瓷嵌体修复能够保护牙周组织,降低龈下致病菌检出率,应用价值显著。

Mechanical properties and structure of zirconia-mullite ceramics prepared by in-situ controlled crystallization of Si-Al-Zr-O amorphous bulk

Zirconia-mullite nano-composite ceramics were fabricated by in-situ controlled crystallization of Si-Al-Zr-O amorphous bulk, which were first treated at 900-1000 ℃ for nucleation, then treated at higher temperature for crystallization to obtain ultra-fine zirconia-mullite composite ceramics. The effects of treating temperature and ZrO2 addition on mechanical properties and microstructure were analyzed. A unique structure in which there are a lot of near equiaxed t-ZrO2 grains and fine yield-cracks has been developed in the samples with 15% zirconia addition treated at 1 150 ℃ . This specific microstructure is much more effective in toughening ceramics matrix and results in the best mechanical properties. The flexural strength and fracture toughness are 520 MPa and 5.13 MPa·m1/2, respectively. Either higher zirconia addition or higher crystallization temperature will produce large size rod-like ZrO2 and mullite grains, which are of negative effect on mechanical properties of this new composite ceramics.