Glass Ceramic Filler Research Articles

Elimination mechanism of voids caused by density differences in high crystallinity alumina/alumina joints bonded with dysprosium aluminum silicate glass ceramic filler

In this work, the Dy2O3-Al2O3-SiO2 (DASN) and Dy2O3-Al2O3-SiO2-TiO2 (DAST) glass fillers were used for joining alumina ceramic. During the cooling process of the alumina/DASN/alumina joints, Dy2Si2O7 and Al2O3 were precipitated simultaneously and gradually grown. As a result, voids were formed due to the poor flowability of the glass ceramic filler and the large density difference between the glass filler and Dy2Si2O7 crystals. On the contrary, the addition of TiO2 altered the sequence of the crystalline phase precipitation during the cooling process. During cooling from the joining temperature (1450 °C) to 1100 °C, only Dy2Si2O7 was formed in the brazing seam. Simultaneously, the flowing glass phase was able to fill the spaces caused by the density differences. When the growth of Dy2Si2O7 phase ceased, the Al2O3 phase began to precipitate. Therefore, the voids caused by density differences can be eliminated in the alumina/DAST/alumina joints with high crystallinity. The optimal flexural strength of alumina/DAST/alumina joints tested at room temperature and 1000 °C reached 350 MPa and 158 MPa, respectively.

Characterization and transport properties of ceramic filler incorporated natural rubber composites

AbstractCrystalline glass–ceramic fillers were prepared from calcium carbonate, silica, alumina, and calcium fluoride by heating and subsequent quenching in cold water. The fillers were incorporated into natural rubber (1,4‐cis‐polyisoprene) and the filled rubber composites were crosslinked with sulfur in the presence of different rubber additives. The unfilled and filled rubber composites were characterized. The transport properties of benzene, toluene, and p‐xylene (BTX) through the rubber composites were studied in terms of sorption, diffusion, permeation, and mass transfer coefficients. The effect of the ceramic fillers on the mechanical, thermal and transport properties were studied. The sorption data at different temperatures were used for calculating activation energy of diffusion, permeation, free energy, and enthalpy of sorption. The BTX remained in the liquid state within the composite matrix as evident from negative ΔS. The diffusion coefficient (D) and mass transfer coefficient (kmtc) of BTX decreased with the increase in filler loading. Accordingly, for the transport of BTX the unfilled rubber showed a D (D × 107 cm2/s) and mass transfer coefficient (kmtc × 104 cm/s) of 5.67/3.97/2.96 and 7.71/7.08/7.04, respectively which decreased to 5.06/2.95/2.57 and 7.53/6.95/6.90, respectively for the composite containing 50 wt.% ceramic filler.

Glass-Ceramic Fillers Based on Zinc Oxide-Silica Systems for Dental Composite Resins: Effect on Mechanical Properties.

The potential of glass ceramics as applicable materials in various fields including fillers for dental restorations is our guide to present a new procedure for improvements of the mechanical properties of dental composites. This work aims to use Zn2SiO4 and SiO2-ZnO nano-materials as fillers to improve the mechanical properties of Bis-GMA/TEGDMA mixed dental resins. Zn2SiO4 and SiO2-ZnO samples were prepared and characterized by using XRD, FE-SEM, EDX, and FT-IR techniques. The XRD pattern of the SiO2-ZnO sample shows that ZnO crystallized in a hexagonal phase, while the SiO2 phase was amorphous. Similarly, the Zn2SiO4 sample crystallized in a rhombohedral crystal system. The prepared samples were used as fillers for the improvement of the mechanical properties of Bis-GMA/TEGDMA mixed dental resins. Five samples of dental composites composed of Bis-GMA/TEGDMA mixed resins were filled with 2, 5, 8, 10, and 15 wt% of SiO2-ZnO, and similarly, five samples were filled with Zn2SiO4 samples (2, 5, 8, 10, and 15 wt%). All of the 10 samples (A1-A10) were characterized by using different techniques including FT-IR, FE-SEM, EDX, and TGA analyses. According to the TGA analysis, all samples were thermally stable up to 200 °C, and the thermal stability increased with the filler percent. Next, the mechanical properties of the samples including the flexural strength (FS), flexural modulus (FM), diameter tensile strength (DTS), and compressive strength (CS) were investigated. The obtained results revealed that the samples filled with 8 wt% of SiO2-ZnO and 10 wt% of Zn2SiO4 had higher FS values of 123.4 and 136.6 MPa, respectively. Moreover, 8 wt% of both fillers displayed higher values of the FM, DTS, and CS parameters. These values were 8.6 GPa, 34.2 MPa, and 183.8 MPa for SiO2-ZnO and 11.3 GPa, 41.2 MPa, and 190.5 MPa for the Zn2SiO4 filler. Inexpensive silica-based materials enhance polymeric mechanics. Silica-metal oxide nanocomposites improve dental composite properties effectively.

Alumina joining using magnesium- or calcium-aluminosilicate glass-ceramic filler comprising Si3N4

Alumina joining using magnesium- or calcium-aluminosilicate glass-ceramic filler comprising Si3N4

Joining of alumina using magnesium- or calcium-aluminosilicate glass–ceramic fillers

Magnesium- and calcium-aluminosilicate (MAS and CAS) glass–ceramics were used to join alumina with six different compositions. The fillers were applied onto the alumina by screen-printing, and then joining was performed slightly below and above the filler melting temperature (Tm). The evolution of various intermediate compounds upon heat treatment between the filler itself and at the joining interface was compared. MgAl2O4 and CaO·6Al2O3 was the main crystalline phase presented at the joining interface for the MAS and CAS system, respectively, while more intermediate compounds were observed when only filler was heat-treated. The formation of MgAl2O4 and CaO·6Al2O3 was attributed to the diffusion of Al ions from the alumina base, which is desirable for obtaining a sound joint due to the similar coefficient of thermal expansion to the base alumina. The maximum joint strength of 250 ± 41 and 301 ± 48 MPa was obtained for MAS and CAS filler system, respectively, after joining at T ≥ Tm due to complete interfacial wetting.

Characterization of Wire-Bonding on LDS Materials and HF-PCBs for High-Frequency Applications

Thermosonic wire bonding is a well-established process. However, when working on advanced substrate materials and the associated required metallization processes to realize innovative applications, multiple factors impede the straightforward utilization of the known process. Most prominently, the surface roughness was investigated regarding bond quality in the past. The practical application of wire bonding on difficult-to-bond substrates showed inhomogeneous results regarding this quality characteristic. This study describes investigations on the correlation among the surface roughness, profile peak density and bonding quality of Au wire bonds on thermoplastic and thermoset-based substrates used for high-frequency (HF) applications and other high-end applications. FR4 PCB (printed circuit board flame resitant class 4) were used as references and compared to HF-PCBs based on thermoset substrates with glass fabric and ceramic filler as well as technical thermoplastic materials qualified for laser direct structuring (LDS), namely LCP (liquid crystal polymer), PEEK (polyether ether ketone) and PTFE (polytetrafluoroethylene). These LDS materials for HF applications were metallized using autocatalytic metal deposition to enable three-dimensional structuring, eventually. For that purpose, bond parameters were investigated on the mentioned test substrates and compared with state-of-the-art wire bonding on FR4 substrates as used for HF applications. Due to the challenges of the limited thermal conductivity and softening of such materials under thermal load, the surface temperatures were matched up by thermography and the adaptation of thermal input. Pull tests were carried out to determine the bond quality with regard to surface roughness. Furthermore, strategies to increase reliability by the stitch-on-ball method were successfully applied.

Improved the Comprehensive Properties of Low‐Temperature Co‐Fired Ceramic Composites Based on ZnO–B2O3–Na2O–Al2O3–SiO2 Glass by Introducing AlN Nano particles

ZnO–B2O3–Na2O–Al2O3–SiO2 (ZBNAS) glass/Al2O3/AlN biphasic ceramics are prepared by a standard tape casting process and solid phase sintering. The low‐temperature co‐fired ceramic (LTCC) tapes are sintered at 850 °C for 2 h under a nitrogen atmosphere. The new phase of ZnAl2O4 is formed by the reaction between glass phase and ceramic fillers during the sintering process. The addition of AlN improves the comprehensive properties of the ZBNAS glass/Al2O3 composites. The samples with 30 wt% AlN exhibit a thermal conductivity of 5.48 W m−1 K−1, a low dielectric constant of 2.99 and a dielectric loss of 0.029 at 18 GHz, and a coefficient of thermal expansion (CTE) of 6.98 × 10−6 °C−1. The obtained composite ceramic with good comprehensive performance may be the promising candidates for high‐power devices.

A novel glass-ceramic with high crystallinity for joining of SiC ceramic

A novel CaO-Al2O3-SiO2-Li2O (CASL) glass-ceramic filler with high crystallinity was used for joining SiC ceramic at 1260 °C for 10 min. The microstructure and interfacial structure of the joint were characterized in detail. The results showed that the anorthite and spodumene-wollastonite eutectic structure were the main products within the joint domain, and the glass-ceramic has a perfectly matched coefficient of thermal expansion with SiC. Besides, the glass-ceramic has a crystallinity of up to 95.9 wt% and remains thermal stability at 1000 °C. The characterization of the interface revealed the liquid glass can infiltrate into SiC grain boundary due to its good compatibility with SiC. The typical microstructure of joint was the SiC substrate/ CaAl2Si2O8 + LiAlSi2O6-CaSiO3 eutectic + glassy phase/the SiC substrate.

Ceramic and glass-ceramic fillers in dental composites - A review

Dental composite fillings are most popular fillings wherein various fillers have been suitably dispersed in a polymerizable resin. Major challenges are to make choice of suitable filler and their distribution in the resin matrix in the development of the dental fillings. Apart from traditional fillers ceramic whiskers, glass fibres, branched fibres and nanoporous powders have also been investigated as fillers in dental composites. Recently, ceramic, and glass-ceramic fillers are attracting attention of the researchers due to their suitable combination of material properties. In the current paper, the prospect of ceramic and glass-ceramics as fillers in fabricating dental composites has been reviewed.

Natural rubber composites containing fillers of sol–gel glasses and glass–ceramics in the CaO–SiO2–P2O5 system

A number of properties of natural rubber-based composites containing fillers of sol–gel glasses and ceramics from the CaO–SiO2–P2O5 system were investigated and compared. Its goals were to evaluate and select more suitable usages in flexible electronics, in particular as substrates and insulating layers in antennas for wireless communications. The fillers were characterized by XRD, SEM, adsorption–texture characteristics and particle size distribution. The composites were characterized by their vulcanization, physico-mechanical, dielectric and dynamic characteristics, as well as their volume resistivity and coefficient of thermal conductivity. The studies revealed that the specific features of the fillers, above all their texture characteristics (specific surface area, presence and amount of micro- and mesopores) have a significant impact upon all studied properties of the composites. The complex evaluation has demonstrated that the composites containing glass–ceramic fillers, especially at 20–50 phr, are more suitable as substrates and insulating layers in flexible antennas for wireless communications.

Joining alumina ceramic by using glass ceramic filler with high crystallinity for high temperature application

Abstract CaO–Al2O3–SiO2–TiO2 glass ceramic filler with high crystallinity was used for joining alumina ceramic. The influence of joining temperature and crystallization treatment on the microstructure and flexural strength of joints was studied. The results demonstrated that a joining temperature higher than the melting temperature of crystals was essential to obtain dense joints. Furthermore, the formation of CaAl2Si2O8 at the alumina/glass filler interface decreased the flexural strength of joints due to the mismatch of coefficient of thermal expansion (CTE) between CaAl2Si2O8 and substrate. The maximum flexural strength of 256 MPa at room temperature was achieved when the joining temperature was 1260 °C. After crystallization treatment, a large number of fine CaTiSiO5 was precipitated in the brazing seam. The flexural strength of joints after crystallization at room temperature was 221 MPa, and increased to 242 MPa at 800 °C. These results can be attributed to the change of CTE value of the brazing seam.

Prevention of Periodontitis by the Addition of a Bactericidal Particulate Glass/Glass-Ceramic to a Dental Resin: A Pilot Study in Dogs

The aim of the study is to evaluate, in a ligature-induced periodontitis model, the efficacy of a commercially available dental resin containing different antimicrobial glass/glass-ceramic additions (0–26 wt.%). It has been proved that a 26 wt.% glass addition to a conventional dental resin matrix does not alter neither its workability nor its adhesion to the surface of teeth; however, it does confer notable antimicrobial properties when tested in vitro. Moreover, in vivo tests in Beagle dogs demonstrated the prevention of bone loss in ligature-induced plaque accumulation around teeth. Particularly, the glass-ceramic filler resin composite has shown excellent antimicrobial control since it displays the same bone loss as that of the negative control. The results obtained in the present investigation have shown that a conventional dental resin containing a fraction of glass/glass-ceramic (≥26 wt.%) can prevent periodontitis, which is considered to be a most serious dental disease.

Laser joining of Al2O3 liners with Al2O3–MgO–SiO2 glass-ceramic fillers

The influence of fillers composition on microstructure, the physical and chemical properties of joints is studied. Thermal mismatch between fillers and Al2O3 liners during laser joining process could be effectively reduced with the increase of MgO content. The mutual diffusion and the substitution reaction lead to the formation of the eutectic spinel phase (Mg, Fe)Al2O4. The interfacial atomic diffusion is enhanced by the addition of MgO. The joints corresponding to fillers composed of 70 wt.% Al2O3-15 wt.% MgO-15 wt.% SiO2 have the optimal mechanical performance. The average flexural strength of joints reaches 168 Mpa which is 80% of the Al2O3 liner (200Mpa). The weight loss of the joint interlayer in 10 wt.% HCl (pH = 0.45) for 24 h is 0.62 mg/cm2 which is 0.16 mg/cm2 lower than that of the liner. The softening temperature of joint interlayer exceeds 1500 °C. The reliability of Al2O3-lined joints could be maintained during the sequential process of arc welding for outer steel pipe layers. The corrosion of pipe layers could be effectively avoided.

Effect of TiO2 content on the crystallization behavior and properties of CaO-Al2O3-SiO2 glass ceramic fillers for high temperature joining application

The effects of TiO2 content on the crystallization behavior, microstructure, microhardness, coefficient of thermal expansion (CTE) and softening temperature of CaO-Al2O3-SiO2 glass ceramic fillers were investigated. The results show that the crystallization activation energy (E) firstly decreases and then increases with the TiO2 addition from 10 wt% to 20 wt%. The microstructure and phase composition of glass ceramics importantly depend on the content of TiO2. Low TiO2 content results in formation of Ti-contained crystals (CaTiSiO5) due to phase separation. In contrast, high TiO2 concentrations lead to precipitation of small titanium oxide crystals that act as nuclei, facilitating the development of CaAl2Si2O8. Furthermore, the formation of crystalline phases is beneficial for improving the microhardness and refractoriness of glass ceramics. The CaO-Al2O3-SiO2 glass with 15 wt% TiO2 addition exhibits the highest crystalline volume fraction possibly due to the lowest activation energy of crystallization. As a result, its microhardness and softening temperature can reach as high as 898.2 HV and 1027 °C, respectively. However, its CTE slightly decreases from 7.44 × 10−6/°C to 6.35 × 10−6/°C after crystallization treatment because of the formation of CaTiSiO5.

Polymer-Rich Composite Electrolytes for All-Solid-State Li-S Cells.

Polymer-rich composite electrolytes with lithium bis(fluorosulfonyl)imide/poly(ethylene oxide) (LiFSI/PEO) containing either Li-ion conducting glass ceramic (LICGC) or inorganic Al2O3 fillers are investigated in all-solid-state Li-S cells. In the presence of the fillers, the ionic conductivity of the composite polymer electrolytes (CPEs) does not increase compared to the plain LiFSI/PEO electrolyte at various tested temperatures. The CPE with Al2O3 fillers improves the stability of the Li/electrolyte interface, while the Li-S cell with a LICGC-based CPE delivers high sulfur utilization of 1111 mAh g-1 and areal capacity of 1.14 mAh cm-2. In particular, the cell performance gets further enhanced when combining these two CPEs (Li | Al2O3-CPE/LICGC-CPE | S), reaching a capacity of 518 mAh g-1 and 0.53 mAh cm-2 with Coulombic efficiency higher than 99% at the end of 50 cycles at 70 °C. This study shows that the CPEs can be promising electrolyte candidates to develop safe and high-performance all-solid-state Li-S batteries.

Joining technology—A challenge for the use of SiC components in HTRs

The availability of suitable joining technologies is paramount to the further advancement of ceramic components and their use in HTRs. Among other joining technologies, a modified brazing technology using a laser beam for heating the components to be joined has been developed at TU Dresden.The laser-induced heating behavior of the ceramic material is determined by the interactions between the material and the laser beam. This was shown in two different silicon carbide materials (SSiC and SiCf-reinforced ceramic material) using a diode laser with wavelengths 808nm and 940nm.The laser-based technique was illustrated by three different examples: sealing of monolithic SiC with a pin configuration for fuel claddings, sealing of SiC heat pipes with a length of 1m, and demonstration of the transferability of the laser technique to fiber-reinforced components by means of a SiCf/SiCN material.Because the covalent bonding of SiC does not allow conventional welding, much research has been devoted to developing alternative filler systems. Glass or glass–ceramic fillers enable the tailoring of properties such as CTE and viscosity. Glasses are thermally stable up to their glass transition temperatures. It was shown that the crystallization of the yttrium aluminosilicate glass composition of the present work allows it to be used at 1050°C without any significant changes occurring in braze tightness. For the SiC heat pipes with sodium as the working fluid, a sodium-resistant metal braze consisting of Ni–Ti–Si was formed. The long-term resistance of this filler to sodium at 800°C was proven. The results demonstrate the possibility of using the laser-based joining technique for the joining of different SiC materials as well as for different brazing materials.

Crystallization Behavior of Glass Ceramic Filler During Joining Process

Crystallization Behavior of Glass Ceramic Filler During Joining Process

Laser-supported joining of SiC-fiber/SiCN ceramic matrix composites fabricated by precursor infiltration

Abstract SiC-fiber/SiCN ceramic matrix composites were manufactured by means of polymer infiltration and pyrolysis. The fiber preform was made by slurry infiltration and winding using a computer-controlled winding module. Multiple infiltration steps using a Si–C–N precursor were included to increase the density. The influence of the sintering conditions on the microstructure of the CMC was demonstrated. Pipe sections made of the CMC materials were joined using a laser-supported heating technology with an Y–Al–Si–O glass–ceramic filler. The thermal response of the CMC components was controlled by the anisotropic thermal conductivity. Fast heating by laser beam was achieved for elements rotating in the direction of the fiber winding. SEM micrographs of the joints showed the good wettability of the CMC by the glass–ceramic filler. Nearly defect-free joints were obtained using a nitrogen process atmosphere. The laser-supported technology was shown to be promising for the joining of CMC components.

Y2O3–Al2O3–SiO2-based glass-ceramic fillers for the laser-supported joining of SiC

Abstract Four glass-ceramic filler compositions within the Y 2 O 3 –Al 2 O 3 –SiO 2 system were tested for their suitability in laser-supported joining of SiC materials. The compositions differed in terms of their primary crystallization behavior. Joint zone microstructures were investigated and joint tightness was determined using helium leak rate measurements after joining and subsequent annealing at 900 °C and 1050 °C. Yttria- and silica-rich compositions showed a partial crystallization of yttrium silicates during the short laser processing. Subsequent heat treatment effected further crystallization toward equilibrium conditions. Despite the strong change in the degree of crystallization no reduction of the tightness was observed for the best compositions; after 500 h annealing at 1050 °C tightness values of less than 10 −8 mbar l s −1 were measured. These results demonstrate the potential of the investigated filler system for high temperature stable hermetic sealing. At the same time the creation of homogeneously structured joints from glass-ceramic fillers using a laser-supported technology needs the understanding of the crystallization kinetics.

Synthesis and characterisation of dental composite materials reinforced with fluoroapatite–mullite glass–ceramic particles

Glass–ceramic filler particles containing various amounts of fluoroapatite–mullite crystalline phases were synthesised using SiO2–Al2O3–P2O5–CaF2–CaO system as the base glass formulation. Different additives were used to promote crystallisation in this system. Composite samples were prepared by incorporating the silane treated glass–ceramic particles into the Bis-GMA/TEGDMA (60∶40 mass ratio) epoxy matrix. Structural and microstructural characterisations were conducted using Fourier transform infrared spectroscopy, X-ray diffractometry and scanning electron microscopy (SEM). The mechanical properties of the light cured samples were examined by measuring flexural and diametral tensile strength, as well as conducting Vickers microhardness test. Results obtained in this study showed strong dependence of the flexural strength on the composition of the filler particles. Diametral tensile strength and microhardness values demonstrated lesser sensitivity to the filler composition. Microstructural examination of the samples by SEM revealed particle pull-out, debonding and crack deflection as the major energy consuming mechanisms in the fracture process.