In this study, ZTA (3Y-TZP/Al2O3) ceramic composites with added SrO sintering aid from SrCO3 and Sr(NO3)2 precursors were prepared by means of pressureless sintering and hot isostatic pressing sintering (HIPing). The microstructure and mechanical properties of the ZTA ceramic composites with added SrCO3 and Sr(NO3)2 were examined, respectively. It was found that SrO incorporation inhibited grain growth and induced the in situ formation of SrAl12O19 platelets. As the SrO content increased, the fracture toughness of the ceramic composites improved; additionally, the hardness and flexural strength initially increased and then decreased. Compared to ZTA ceramics with SrCO3 addition, the samples with Sr(NO3)2 had finer grains with a more uniform platelet distribution. ZTA ceramic composites with the addition of Sr(NO3)2 exhibited a maximum hardness, four-point flexural strength, and fracture toughness of 18.46 GPa, 887 MPa, and 6.97 MPa m1/2, respectively.
X-ray computed tomography (XCT) was utilized to perform quantitative and qualitative characterizations of aqueous-oxygen corrosion evolution in SiCf/SiC composites under pre-and post-oxidation conditions. The results indicate that the SiC matrix formed with the precursor impregnation and pyrolysis (PIP) method is located mainly in the inter-bundle region, which experiences significant oxidation after 160 hours of oxidation. This oxidation results in the formation of SiO2 that fills the inter-bundle pores, leading to a decrease in porosity from an initial 10.9 % to 6.8 %. The interconnected inter-bundle pore network facilitates the ingress of oxygen, resulting in corrosion damage that is initiated preferentially at pore periphery regions. Progressive aqueous-oxygen corrosion leads to pore channel narrowing with surface smoothening, accompanied by the formation of vesicular porosity along the specimen periphery. A connected sheet-like and layered oxide skeleton structure forms finally because of the corrosion of matrix in the inter-bundle region.
An innovative electrodeposition method was developed to fabricate Ni-ZnO composite coatings on high-carbon stainless steel substrates for industrial cutting applications. In this study, key deposition parameters including current density (ranging from 2 to 8 A/dm2), bath pH (optimally maintained at 10), temperature (45 degrees C), and stirring rate (250 rpm) were systematically optimized to enhance coating properties. The integration of ZnO nanoparticles resulted in a refined microstructure, reducing the average grain size from 0.72 & micro;m to 0.56 & micro;m, while the coating thickness increased from 11.1 & micro;m at lower current levels to 24.1 & micro;m at 8 A/dm2. Under optimal conditions at 6 A/dm2, the deposition efficiency reached approximately 85 %. Electrochemical evaluations demonstrated a substantial improvement in corrosion resistance; charge transfer resistance increased from 452 !c m2 for uncoated substrates to 2 370 !c m2 for pure nickel coatings and further to 5 515 !c m2 for the composite, while corrosion current density was reduced from 30 & micro;A/cm2 to 7.9 & micro;A/cm2. Mechanical testing revealed that the composite coating exhibited a hardness of 4.8 GPa and a Young's modulus of 88 GPa, in contrast to 2.9 GPa and 52 GPa for pure nickel layers. Additionally, abrasion tests indicated a decrease in weight loss from 66 mg to 27 mg over a 35 km sliding distance. Overall, the findings confirm that the strategic incorporation of ZnO nanoparticles significantly enhances both the structural integrity and protective capability of the coating, offering a robust and cost-effective solution for prolonging the service life of industrial components. These promising results pave the way forward.
Silicon carbide (SiC) ceramics are a novel packaging material that has demonstrated significant potential in the field of electronic packaging in recent years. In this study, SiC composite ceramics were prepared using a pressureless liquid-phase sintering method with Al2O3-Y2O3-MgO-BN as sintering additives. The influence of the BN content on the thermal properties of SiC composite ceramics was investigated, with the aim of exploring the performance advantages of SiC composite ceramics in packaging applications. The results indicate that the main crystalline phase of all samples is 6H-SiC, with a relatively uniform grain size distribution ranging between 0-2 lm. The sample with a mass ratio of 90%SiC:2%Al2O3:3%Y2O3:2%MgO:3%BN (labeled as M2B3) exhibited a hardness of 340.22 N/mm2, thermal expansion coefficient of 3.35 & times; 10-6 K-1, dielectric constant of e = 486.211, and dielectric loss of tan d = 0.507. These properties meet the requirements for high hardness, low dielectric loss, and well-matched thermal expansion coefficient, making SiC composite ceramics a promising candidate for next-generation high-performance electronic packaging materials.
To assess the influence of surface conditioners, i.e. hydrofluoric acid (HFA), Er: YAG laser, and Radachlorin-activated low-level laser therapy (LLLT), on the contact angle (CA), surface topography, and shear bond strength (SBS) of lithium disilicate ceramics (LDC) and resin-based ceramics (RBC). RBC Lava Ultimate (Group A) and IPS Emax (Group B) were used to obtain forty-five discs in each case. Each group was further divided into subgroups based on the conditioning protocol used. Group 1: HFA, Group 2: Er: YAG laser, and Group 3: LLLT (RD). CA (n =2) and surface topography analysis (n =3) were performed using a goniometer and scanning electron microscope. Resin cement was built on ten discs from each group, followed by the evaluation of the SBS by means of a universal testing apparatus. A one-way ANOVA and Tukey test were utilized to conduct a comparative analysis of CA and bond strength values. The lowest CA was exhibited by Group 1A (HFA + LDC) with the highest bond strength. Whereas Group 3B (RDLLLT+RBC) presented the highest CA and lowest SBS. The Er: YAG laser can be considered as a suitable alternative to HFA for enhancing the contact angle and bond integrity of adhesive cement. LDC and RBC exhibited comparable contact angle and bond strength outcomes, except in the hydrofluoric acid group.
