Ceramics Surfaces Research Articles

Study on wetting mechanism of Sn3Sc alloy on silica and sapphire surfaces

To further investigate the wetting mechanism of filler alloys containing active elements on oxide ceramics surfaces, we prepared a new filler alloy (Sn-3at.%Sc filler alloy) containing trace rare earth elements by vacuum melting furnace. Under high vacuum, its wetting behavior on silica and sapphire substrates was studied using a modified sessile drop method. The final contact angles of liquid Sn-3at.%Sc filler alloy on silica and sapphire surfaces are 6.0° and 9.8°, respectively, showing good wetting properties, and exhibiting similar wetting behavior at the same temperature. The same interfacial product Sc2O3 was detected at the interface of Sn-3at.%Sc/silica and Sn-3at.%Sc/sapphire systems. However, thermodynamic and spreading analysis suggests that Sc2O3 is precipitated in different ways at the interface of the two systems. The former is generated by an interfacial reaction, while the latter precipitates during the cooling process. The wettability of the Sn-3at.%Sc/silica system may depend on the interaction between the interface reaction products and residual scandium adsorption at the solid/liquid interface, while the wettability of Sn-3at.%Sc/sapphire system may depend on the adsorption of Sc-O clusters at the interface. These findings provide a theoretical basis and design ideas for further development of tin-based filler alloys and design of new type filler alloys.

YBa2Cu3Oy Superconducting Ceramics Incorporated with Different Types of Oxide Materials as Promising Radiation Shielding Materials: Investigation of The Structure, Morphology, and Ionizing Radiations Shielding Performances.

New series of YBCO ceramics samples doping with different oxides such as SiO2, WO3, Al2O3, and TiO2 were fabricated to study the ionizing radiation shielding properties. The structure and morphology were explored by X-ray diffraction (XRD) and scanning electron microscope (SEM). The shielding properties were investigated experimentally and theoretically to check the validity of the results. The investigated radiation shielding properties include the proton, neutron, and gamma-ray. The XRD results show the orthorhombic structure for all ceramics without any additional peaks related to WO3, SiO2, TiO2, and Al2O3. At the same time, the SEM results appear to have a significant differentiation in the granular behavior of all ceramics surfaces. The incorporation of WO3 to YBCO enhanced the ceramic density, whereas the addition of different oxides reduced the density for ceramic samples. This variation in density changed the radiation shielding results. The sample containing WO3 (YBCO-W) gives us better results in radiation shielding properties for gamma and neutron; the sample having Al2O3 (YBCO-Al) is superior in shielding results for charged particles. Finally, the possibility to use YBCO with various oxides in different ionizing radiation shielding fields can be concluded.

Removal of cadmium in wastewater by sorption on ceramics

The removal of cadmium by ceramics surfaces was investigated to evaluate sorption effectiveness of these materials in residual waters. The effects of solution pH, contact time, metal concentration and dose of sorbet material were studied in batch experiments. Ceramic material was compositionally and morphologically characterized before and after the removal of cadmium by scanning electron microscopy to establish the metal sorption Sorbent material was also tested in residual water with high cadmium content, achieving a 98% removal efficiency.

Achieving highly hydrophobic or hydrophilic HfNx-Ag films surfaces by controlling the existing forms of Ag

Increasing demands for robust hydrophobic or hydrophilic surfaces in harsh conditions such as erosion, abrasion and high temperature, have stimulated the development of intrinsically hydrophobic or hydrophilic ceramics (or metals). Despite tremendous efforts, realizing robust highly hydrophobic or hydrophilic ceramics surfaces using a simple method remains a great challenge. In this letter, we report that HfNx-Ag films with two different existing forms of Ag: (1) Solute Ag and (II) Precipitate Ag, were deposited using co-sputtering system by setting deposition temperature at room temperature (RT) and 400°C, respectively, further achieving highly hydrophobic (water contact angle (WCA)∼120°) or hydrophilic (WCA∼55°) surfaces by controlling the content of solute Ag or precipitate Ag. Solute Ag provides the hydrophobic Ag2O groups with coordinative saturation though surface self-oxidation, which inhibits hydrogen bonding with interfacial water molecules, whereas hydrophilic precipitate Ag acts as Lewis acid, which interacts strongly with water.

Fabrication of Biocompatible Potassium Sodium Niobate Piezoelectric Ceramic as an Electroactive Implant.

The discovery of piezoelectricity in natural bone has attracted extensive research in emulating biological electricity for various tissue regeneration. Here, we carried out experiments to build biocompatible potassium sodium niobate (KNN) ceramics. Then, influence substrate surface charges on bovine serum albumin (BSA) protein adsorption and cell proliferation on KNN ceramics surfaces was investigated. KNN ceramics with piezoelectric constant of ~93 pC/N and relative density of ~93% were fabricated. The adsorption of protein on the positive surfaces (Ps) and negative surfaces (Ns) of KNN ceramics with piezoelectric constant of ~93 pC/N showed greater protein adsorption capacity than that on non-polarized surfaces (NPs). Biocompatibility of KNN ceramics was verified through cell culturing and live/dead cell staining of MC3T3. The cells experiment showed enhanced cell growth on the positive surfaces (Ps) and negative surfaces (Ns) compared to non-polarized surfaces (NPs). These results revealed that KNN ceramics had great potential to be used to understand the effect of surface potential on cells processes and would benefit future research in designing piezoelectric materials for tissue regeneration.

Microhardness evaluations of CAD/CAM ceramics irradiated with CO2 or Nd:YAP laser.

The aim of this study was to measure the microhardness values of irradiated computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics surfaces before and after thermal treatment. Sixty CAD/CAM ceramic discs were prepared and grouped by material, i.e. lithium disilicate ceramic (Emax CAD) and zirconia ceramic (Emax ZirCAD). Laser irradiation at the material surface was performed with a carbon dioxide laser at 5 Watt (W) or 10 W power in continuous mode (CW mode), or with a neodymium:yttrium aluminum perovskite (Nd:YAP) laser at 10 W on graphite and non-graphite surfaces. Vickers hardness was tested at 0.3 kgf for lithium disilicate and 1 kgf for zirconia. Emax CAD irradiated with CO2 at 5 W increased microhardness by 6.32 GPa whereas Emax ZirCAD irradiated with Nd:YAP decreased microhardness by 17.46 GPa. CO2 laser effectively increases the microhardness of lithium disilicate ceramics (Emax CAD).

A Novel Conservation Method of Historical Outdoor Ceramics

In this study, a novel conservation method was developed for the protection of historical outdoor ceramics. The historical ceramics from monastery of “San Filippo di Fragala” (Sicily, Italy) were chosen for this study. Polymeric films on the surface of ceramics specimens were formed using Silres BS 16 as a precursor. For the comparison, the material Paraloid B-82, which is already known in the conservation practice, was also used for the formation of protective coatings on historical ceramics. The investigated samples were characterized by SEM, TG, EDX, XRD methods and contact angle measurements. The results obtained showed that ceramic samples were successfully preserved and saturated by Silres BS 16 with forming effective polymeric coatings on ancient ceramics surfaces. Keywords: Ancient ceramics, conservation, Silres BS 16, SEM, TG, contact angle. DOI: http://dx.doi.org/10.5755/j01.ms.21.2.6823

Effect of Pressing Force on the Physical Properties of CaMgTiO<sub>3</sub> Ceramic Prepared by HEBM

CaMgTiO3 ceramics were synthesized by using the high energy ball-milling method (HEBM) at different pressing forces. The raw materials were ball milled for 20 hours and sintered at 1000°C. Ceramics surfaces morphologies and particle sizes were measured using SEM analysis. Archimedes’ method was adapted to obtain their densities and porosities. It was found that pressing forces influenced both morphologies and particle sizes. As pressing forces increased, the particle sizes decreased as shown in SEM observation. However, the particle sizes increased at 200 kN due to agglomerated grain growth. The densities were almost constant with increasing of pressing forces while porosities were reduced.

Alumina–zirconia composites functionalized with laminin-1 and laminin-5 for dentistry: Effect of protein adsorption on cellular response

The present paper describes a study on laminin interaction with the surface of two alumina–zirconia composites with different percentages of ZrO2, both with submicrometric grain size. As major molecules within the basement membrane (BM), laminins are important protein fragments for epithelial cell adhesion and migration. On the other hand, alumina–zirconia composites are very attractive materials for dental applications due to their esthetic and mechanical properties. X-Ray photoelectron spectroscopy and atomic force microscopy were used to study the adsorption of two types of laminin, laminin-1 (Ln-1) and laminin-5 (Ln-5), onto the ceramics surfaces. The in vitro cell response was determined by intracellular phosphorylation of major kinases. Ceramics samples functionalized with laminins showed better cellular activation than untreated specimens; furthermore, cellular activation was found to be greater for the composite with higher percentage in zirconia when functionalized with Ln-5, whereas the adsorption of Ln-1 resulted in a greater activation for the alumina-rich oxide.

Temperature Dependence of Coercivity Behavior in Fe Films on Fractal Rough Ceramics Surfaces

In this paper we study the anomalous magnetic properties in Fe films on fractal rough α-Al2O3 ceramics surfaces. It is found that the temperature dependence of the coercivity Hc of the Fe films exhibits a peak around a critical temperature Tcrit = 10 K: firstly, Hc increases with the temperature T; then it decreases rapidly as T further increases. The peak of the coercivity goes up with the decrease of the film thickness. It is estimated that, for T < Tcrit, the anomalous coercivity behavior may be resulted from the coupling effect of the spin-glass like states and ferromagnetic phases, for T > Tcrit, the observed coercivity behavior is mainly dominated by the effect of the non-uniform size distribution of the single-domain particles or magnetic clusters. The study shows that the enhancement Hc of the Fe films is strong related to the roughness of the film surfaces induced by the fractal ceramics surfaces. The results are further confirmed by the thermoremanence and vibrating sample magnetometer measurements.

Evaluation of the Influence of the Silane Drying Temperature on the Feldspar and Zirconia-Based Ceramics Surfaces

Ceramics are widespread used in restorative dentistry, mainly due to their aesthetics features. However, adequante bond strenght of this type on restoration to tooth structure spawned several investigations which aim to develop a clinical protocol for ceramic surface treatment. The objective of this study was to evaluate the influence of air temperature on the drying process of silane agent and the adhesion of feldspar and yttrium stabilized zirconia. They were divided into three groups (n=10): control; room temperature dried silane; and silane drying at 70º C. Then, composite resin cylinders were bonded to the samples and taken to a shear test. The results showed that air temperature rise, in silane drying, improved bonding resistance in Y-TZP ceramics, nevertheless in feldspatic ceramics, the bonding resistance was not altered.

Fractal analysis of engineering ceramics ground surface

Traditional methods of roughness characterization cannot properly reflect the differences between metal and engineering ceramics surfaces. Therefore, fractal method is introduced to characterize the engineering ceramics ground surface in this paper. This article compares various methods to calculate profile dimension. By comparison, the variation method is suitable for extracting fractal dimension of engineering ceramics ground surface. The precision of variation method is further improved by modifying the error. In view of engineering ceramics ground surface, we have analyzed the relationship between fractal dimension and traditional roughness parameters, surface texture, surface function and material property using modified variation method.

THE INFLUENCE OF FEED RATE ON SURFACE ROUGHNESS OF TIC–WC CARBIDE AND AL2O3 CERAMICS SAWN-OFF WITH INNER EDGE OF DIAMOND DISC

The paper presents results of measurements of surface roughness of titanium-tungsten carbide (T14K8) and aluminium oxide (Al2O3) ceramics surfaces sawn-off with inner edge of diamond disc. The cutting process was performed by cutting machine “АЛМАЗ-4” with 60/40 grain size disc. The dependence of average roughness Ra of the sawn-off surface on feed speed of the workpiece was established.

A Research on Interfacial Reaction of Brazing Joint of Alumina Ceramics to Metals

Brazing with active filler alloys containing some active elements, which promotes wetting of ceramics surfaces, is one of the most widely methods for joining ceramics to metals. The joints formed by brazing A12O3 to metal by using copper-titanium-nickel (Cu-Ti-Ni) as brazing filler were investigated. The metals/ceramics joints were produced at a vacuum level of 10-2-10-3 Pa at 1273K, using a constant holding time of 10 min. The surfaces were studied both morphologically and structurally using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD). In the brazing process, copper and titanium in the braze alloy form a series of reaction products. The formation of Ti3Cu3O and Ti2Ni at the interface is characteristic of these joints. The estimated free energies of formation of the Ti3Cu3O and Ti2Ni are -119kcal/mol and -245.92 kJ ~-263.78kJ/mol at 1200~1288K respectively. The highly negative values for the free energies of formation suggest that these compounds are thermodynamically stable.

Low Self-Affine Exponents of Fractured Glass Ceramics Surfaces

The geometry of postmortem rough fracture surfaces of porous glass ceramics made of sintered glass beads is shown experimentally to be self-affine with an exponent zeta=0.40+/-0.04, remarkably lower than the "universal" value zeta=0.8 frequently measured for many materials. This low value of zeta is similar to that found for sandstone samples of similar microstructure and is also practically independent on the porosity phi in the range investigated (3%< or =phi< or =26%) as well as on the bead diameter d and of the crack growth velocity. In contrast, the roughness amplitude normalized by d increases linearly with phi while it is still independent, within experimental error, of d and of the crack propagation velocity. An interpretation of this variation is suggested in terms of a transition from transgranular to intergranular fracture propagation with no influence, however, on the exponent zeta.

Preparation of Bioactive Nanophase Titania Ceramics by Alkali-Heat Treatment

In this study, alkali-heat treatment in NaOH solution and heat treatment, which could form amorphous sodium titanate on nanophase titania ceramics surface by conditioning the process, was employed to modify the structure and bioactivity of biomedical titania ceramics. After the nanophase titania ceramics was subjected to alkali-heat treatment, thin film X-ray diffraction and scanning electron microscopy results showed the titania ceramics surfaces were covered by porous sodium titanate. In fast calacification solution (FCS), the alkali-heat treated titania ceramics could induce bonelike apatite formation on its surface. Our results showed that induction of apatite-forming ability on titania ceramics could be attained by alkali-heat treatment. So it was an effective way to prepare bioactive titania ceramics by combining sintering and alkali-heat treatment.

Histological Evaluation of an 11-year-old Hydroxyapatite Ceramic Implant in Mandibular Bone

There are no detailed long-term histological studies of hydroxyapatite implanted in human bone tissue. This report is of histological and radiographic examination of a patient with mandibular bone implanted with hydroxyapatite ceramics after cyst ennucleation and a good clinical course for 10 years. The mandibular bone was resected 11 years after the initial operation because of infection. Histology of the retrieved mandibular bone revealed that bone tissue proliferated into interparticular spaces and attached to the hydroxyapatite ceramics surfaces in the non-infected portion and that hydroxyapatite ceramics disappeared with bone destruction in the infected portion. From the histological results, clinical findings, and chronological radiographic findings for 10 years, it was concluded that hydroxyapatite ceramics could maintain their favourable properties as a bone substitute in human bone for a long time.

Electrical characterization of grain boundary decorated SrTiO3 ceramics

The intention of the present work was to investigate the influence of the grain size on the electrical properties of Mn decorated SrTiO 3 ceramics. To obtain different average grain sizes the samples were prepared by variation of the following sintering conditions: form of the green bodies, heating/cooling ramps, sintering atmosphere, sintering time, and sintering temperature. The grain boundaries of the ceramics were decorated with Mn by diffusion from the ceramics surfaces. Impedance analysis techniques in the scope of time and frequency dependence were used for electrical characterization and accelerated life testing (ALT) measurements were performed to characterize the ageing behaviour.

Metallization on piezoelectric ceramics surfaces by synchrotron radiation irradiation

In order to investigate the potential of applying the synchrotron radiation (SR) process to the micromachine field, the irradiation effects on a piezoceramics PZT [Pb(Zr x, Ti 1−x)O 3] were studied. The desorption of O, Ti, Zr atoms from PZT was observed, and the irradiated surface of the sample became lead-rich. These selective desorptions refer to a modification of the ceramics surface into a metallic one. In fact ohmic conductivity was observed on the irradiated surface, whereas no conductivity was obtained on the unirradiated surface. The results obtained in this study are quite interesting from both aspects of desorption mechanism study and application to electrodes formation on piezoelectric devices.

Investigations into the cytotoxicity of titania ceramics surfaces

Investigations into the cytotoxicity of titania ceramics surfaces