Ceramic Sheets Research Articles

A neutron beam monitor based on silicon carbide semiconductor coated with 6LiF converter

A neutron beam monitor was developed for the time-of-flight neutron reflectometer (NR) instrument at the China Mianyang Research Reactor (CMRR). The SiC neutron monitor employs a wide-bandgap silicon carbide (SiC) semiconductor detector coated with a 6LiF neutron converter film evaporated on a thin ceramic sheet. Given the relatively large active area [(10 × 10) mm2] and sufficiently thick epitaxial layer (30μm), the monitor can discriminate the gamma background from the signals. Prior to assembling the monitor, the I–V characteristics and alpha responses of the SiC detector were measured. Next, the SiC detector and 6LiF neutron converter were installed in a small aluminum shielding box, and the neutron and gamma responses were measured with an Am–Li neutron source and a 137Cs plus 60Co gamma source, respectively. The fabricated SiC neutron monitor was mounted inside the slit of the NR instrument (after the focusing neutron guide), and the intensity of the transmitted neutron beam was measured. To measure the incident neutron flux, the distinct triton peaks from the 6Li (n, α) T reaction were counted as normalized data for the NR instrument. This paper describes the fabrication details of the SiC neutron monitor, and discusses the preliminary measurements.

Stable cycling of all-solid-state lithium battery with surface amorphized Li1.5Al0.5Ge1.5(PO4)3 electrolyte and lithium anode

The severe instability with lithium (Li) anode of NASICON-structure Li1.5Al0.5Ge1.5(PO4)3 (LAGP) solid-state electrolyte (SSE) greatly hinders its practical applications in the all-solid-state lithium batteries (ASSLBs) with high energy density and safety. In order to alleviate this issue, here we employed an artificial protective layer of LAGP glass on the surface of ceramic LAGP sheet to construct a surface amorphized electrolyte via a spin-coating co-sintering method. AC impedance test and galvanostatic charge-discharge cycling of Li/electrolytes/Li symmetrical cell suggest that enabled by this glass layer, the surface amorphized LAGP can exhibit better compatibility with Li anode. In addition, with a poly(ethylene oxide) polymer electrolyte in the cathode side, at 0.1 C under 60 °C, the LiFePO4/Li ASSLB using surface amorphized LAGP can keep stable for 120 cycles with a retention of 93.6%, which is more than 13 times of the cell using ceramic LAGP (6.9%). The formation mechanisms of unstable interphases in LAGP/Li interface were briefly summarized, and probable reasons behind the good compatibility between and LAGP glass and Li were discussed.

Manufacturing of Ti-10Nb based metal sheets by tape casting

Sheets from Ti alloys like Ti-Nb are attractive as structural and functional components for applications in aerospace, biomedicine or electrochemical devices. Tape casting is a cost-effective production method, which has been widely used for production of ceramic sheets. Ti-Nb alloys are (α + β)-type alloys, which have the potential for replacing established Ti-6Al-4V alloy in specific cases, e.g. due to not containing toxic elements like vanadium. In the present work, tape casting was introduced as novel strategy for production of thin Ti-Nb sheets. Elemental Ti and Nb powders were used for production of Ti-10wt%Nb alloy sheets with a thickness of around 350 µm. Sintering behavior and microstructure were investigated by scanning electron microscopy (SEM), chemical analysis and X-ray diffraction. A homogeneous (α + β)-type alloy with low residual porosity of ca. 1.5 vol% was achieved by sintering at 1300 °C.

High-aspect ratio mechanical microdrilling process for a microhole array of nitride ceramics

In semiconductor industry, wafer testing requires a microhole array constructed by high-density holes below ϕ 100 μm for stabilizing the microprobe used in conduction testing. This study conducted mechanical microdrilling experiments of a nitride ceramic sheet to investigate the effects of drilling parameters on quality characteristics of the microhole drilled. Fabrications of a high-aspect ratio microhole must be implemented by segmented machining. A center pilot hole was first made and then drilled the microhole by a two-segment process. Drilling factors analyzed in this study included depth of the center pilot hole, depth ratio of the hole segments, and machining parameters of cutting speed (spindle rotation rate), tool feed rate, and step in peck drilling in the microdrilling. Because both diameter and position of the microhole affect the functionality of hole array directly, this is a multi-objective problem. This study proposes a new decision method for deriving the optimal parameter level set in the multi-object problem based on the level effects obtained from Taguchi’s analyses. In addition, this study used a scanning electron microscopy (SEM) to observe the influences of drilling stroke on flank wear of the microdrill. This study implemented two series experiments of ϕ 69 μm and ϕ 55 μm with aspect ratios of 15.36 and 11.64, respectively. Experimental results indicate that applying the optimal parameter level set derived in ϕ 55 μm experiment could obtain excellent performances after the drilling stroke of 384 mm, 600 holes drilled. The microdrills have fulfilled a high use efficiency.

Quality investigation of alumina ceramic laser cutting based on vapor-to-melt ratio

In order to reveal the relationship between vapor-to-melt ratio and processing quality in pulsed laser cutting of alumina ceramic sheets, experiments are carried out to obtain variations of the vapor-to-melt ratio with laser power, scanning speed, and thickness of ceramic sheet. By the morphological observation and analysis, the influence of the vapor-to-melt ratio on cutting quality is summarized. It is found that the vapor-to-melt ratio is increased with the increase of laser power, while it is decreased with the increase of scanning speed and the increase of sheet thickness. A good processing quality with suitable kerfs' width, better uniformity, and smaller roughness is obtained at a relatively large value of vapor-to-melt ratio. However, the excessive vapor-to-melt ratio will cause the deterioration of cutting stability and quality. Therefore, to meet the requirement, the vapor-to-melt ratio is controlled at around 0.1 to get 250 μm of average kerfs' width and Ra less than 3.2 μm of uniform kerfs. It reveals that the vapor-to-melt ratio is more intuitive to reflect the connection between the forms of material removal and cutting quality in laser processing, which provides an important theoretical and experimental support in the field of precision laser cutting on alumina ceramic sheets.In order to reveal the relationship between vapor-to-melt ratio and processing quality in pulsed laser cutting of alumina ceramic sheets, experiments are carried out to obtain variations of the vapor-to-melt ratio with laser power, scanning speed, and thickness of ceramic sheet. By the morphological observation and analysis, the influence of the vapor-to-melt ratio on cutting quality is summarized. It is found that the vapor-to-melt ratio is increased with the increase of laser power, while it is decreased with the increase of scanning speed and the increase of sheet thickness. A good processing quality with suitable kerfs' width, better uniformity, and smaller roughness is obtained at a relatively large value of vapor-to-melt ratio. However, the excessive vapor-to-melt ratio will cause the deterioration of cutting stability and quality. Therefore, to meet the requirement, the vapor-to-melt ratio is controlled at around 0.1 to get 250 μm of average kerfs' width and Ra less than 3.2 μm of uniform kerfs. It...

Stacked dielectric patch resonator antenna with wide bandwidth and flat gain

A stacked dielectric patch resonator antenna with wide bandwidth and flat gain is proposed. For this design, two thin ceramic sheets with high permittivity are introduced to operate as approximate magnetic walls. Incorporated with another ground plane, two resonant modes can be excited to form a wide bandwidth, and a flat gain is also achieved within the band. Measured results demonstrate that the antenna obtains an impedance bandwidth of 18.2% and an average gain of 7.2 dBi.

Strong and super tough: Layered ceramic‐polymer composites with bio‐inspired morphology

AbstractBio‐inspired layered ceramic‐polymer composites with high strength and toughness were prepared from sintered aluminum oxide ceramic sheets and cationically curing epoxy resins toughened with poly(ε‐caprolactone) (PCL). The architecture of the composite is inspired by nacre but is arranged on a larger scale. Ceramic sheets with a nominal thickness of 250 μm were assembled into composite plates by adhesive layers with a nominal thickness of 20 μm. Before the manufacturing of the composites, the stress‐strain properties of the polymer component were tailored by the variation in the PCL content between 0 and 39 wt%. For composites with 4 and 15 ceramic layers, the bending strengths achieved 327 MPa and 376 MPa, which are higher than that of pure ceramic sheets. Moreover, composites with 15 ceramic layers show a 16 times higher toughness compared to that of the pure ceramic sheets. The results indicate that the toughness of the layered composites increases significantly with the number of layers. Inspired by the geometrical ratio of the natural sheet composite nacre, we have achieved a similar strength but a 2 times higher toughness than nacre by only adding up to 6 vol% of the polymer.

A dense NASICON sheet prepared by tape-casting and low temperature sintering

Ceramic sheet of Na+ ion-conducting solid electrolyte, Na3Zr2Si2PO12 (NASICON), has been prepared by tape-casting method. Addition of 60Na2O-10Nb2O5-30P2O5 glass as a sintering aid is crucial for fabrication of fully-densified impermeable sheet. Otherwise the gas tightness is not achieved even sintered at 1200 °C. The best preparation condition is 5 or 10 wt% grass-addition with respect to NASICON and sintering at 1000–1100 °C, which is lower by 100–200 °C than the typical densification temperature of NASICON without the additive. A sample with a thickness of 35 μm and total conductivity of 4.4 × 10−4 S cm−1 is obtained by 5 wt% glass addition and sintering at 1100 °C for 4 h.

The tape casting process for manufacturing low‐temperature co‐fired ceramic green sheets: A review

AbstractFor low‐temperature co‐fired ceramic technology, the fabrication of high‐performance green sheet is a critical step because of its effect on subsequent operations such as punching, printing, laminating, and firing. Here, we present an overview of the tape casting process for manufacturing high‐performance low‐temperature co‐fired ceramic green sheets. Previous research is reviewed, and the primary materials for preparing the casting slurry, such as powders, solvents, dispersants, binders, and plasticizers, are systematically described. Their functions, application methods, and action mechanisms are described. Suggestions are made for future research into the tape casting process based on recent results.

Densification behavior and electrical properties of carbon nanotube-Ni nanocomposite films for co-fireable microcircuit electrodes

Nanocomposite thick-film electrodes are investigated for highly integrated microcircuit devices that require retarded densification in order to match potential co-fireable ceramic sheets. In this study, we introduce carbon nanotube (CNT) as an ingredient to retard the densification of the conducting Ni paste while minimizing the decrease in the electrical resistivity of the Ni paste. Well dispersed CNT/Ni pastes containing various amounts of CNT ranging from 1 to 5 wt% were screen-printed on a regular alumina substrate and fired at 800–1200 °C for 1 h in a reducing atmosphere. The retardation effect was evident even with 1 wt% CNT that exhibited late full densification at 1100 °C, which corresponds to the target firing temperature for ceramic sheets. Electrical resistivity was not significantly influenced by the low content of CNT, which corresponds to 3.39 × 10−5 Ω cm when compared to 2.97 × 10−5 Ω cm for pure Ni paste processed at the same temperature of 1100 °C. The results indicate that the Ni-CNT composite thick films are potentially useful as a competitive co-fireable electrode.

Thermo-magnetic field effects on the wave propagation behavior of smart magnetostrictive sandwich nanoplates

In this paper, a three-variable plate model is utilized to explore the wave propagation problem of smart sandwich nanoplates made of a magnetostrictive core and ceramic face sheets while subjected to thermo-magnetic loading. Herein, the magnetostriction effect is considered and controlled via a feedback control system. The nanoplate is supposed to be embedded on a visco-Pasternak elastic substrate. The kinematic relations are derived based on the Kirchhoff plate theory; also, combining these obtained equations with Hamilton’s principle, the local equations of motion are achieved. According to a nonlocal strain gradient theory (NSGT), the small-scale influences are covered precisely by introducing two scale coefficients. Afterwards, the nonlocal governing equations are derived coupling the local equations with those of the NSGT. Applying an analytical solution, the wave frequency and phase velocity of the propagated waves can be gathered solving an eigenvalue problem. On the other hand, accuracy and efficiency of the presented model are verified by setting a comparison between the obtained results with those of previous published researches. Effects of different variants are plotted in some figures and the highlights are discussed in detail.

Simultaneously obtained high permittivity and low loss in 2-2 fluoro-polymer/anti-ferroelectric ceramic composites from interface effect

Interface induced polarization has been proved to have a great impact on dielectric features of 2-2 series composites containing Si-based semi-conducting sheet and polymer layer. In those 2-2 composites, the obviously increased high permittivity of Si-based ceramic sheet was confirmed to be responsible for the measured high permittivity of composites. Interface interaction was found to come from strong electrostatic pull of high polarity polymer layer and induced high polarity of Si-based ceramic sheet. In this work, the similar interface interaction was utilized to obtain the desired promising 2-2 series composite dielectrics made from ultra-high polarity anti-ferroelectric ceramic sheet and high polarity fluoropolymer layer. Based on compositing, the obviously elevated high permittivity detected in polymer layer was found to strongly contribute to tested high permittivity in resulting composites. In this case, interface induced polarization should come from a very large electrostatic pull of ceramic sheet (ultra-high polarity ionic dipoles) and elevated high induced polarity of polymer layer (high polarity covalent dipoles). Dielectric and conductive properties of two designed 2-2 composites have been detailedly researched. Reduced total inborn polarity of ceramic sheet was found to lead to a maintained high permittivity, lowered dielectric loss and decreased conductivity in resulting composite. This work might provide a facile route to obtain the desired composite dielectrics with promising comprehensive electric properties based on interface effect in 2-2 composites.

Dielectric, Piezoelectric, and Vibration Properties of the LiF-Doped (Ba0.95Ca0.05)(Ti0.93Sn0.07)O₃ Lead-Free Piezoceramic Sheets.

By the conventional solid state reaction method, a small amount of lithium fluoride (LiF) was used as the sintering promoter to improve the sintering and piezoelectric characteristics of (Ba0.95Ca0.05)(Ti0.93Sn0.07)O3 (BCTS) lead-free piezoceramic sheets. Using X-ray diffraction (XRD) and a scanning electron microscope (SEM), the inferences of the crystalline and surface microstructures were obtained and analyzed. Then, the impedance analyzer and d33-meter were used to measure the dielectric and piezoelectric characteristics. In this study, the optimum sintering temperature of the BCTS sheets decreased from 1450 °C to 1390 °C due to LiF doping. For the 0.07 wt % LiF-doped BCTS sheets sintered at 1390 °C, the piezoelectric constant (d33) is 413 pC/N, the electric–mechanical coupling coefficient (kp) is 47.5%, the dielectric loss (tan δ) is 3.9%, and the dielectric constant (εr) is 8100, which are all close to or even better than that of the pure undoped BCTS ceramics. The Curie temperature also improved, from 85 °C for pure BCTS to 140 °C for BCTS–0.07 LiF sheets. Furthermore, by using the vibration system and fixing 1.5 g tip mass at the end of the sheets, as the vibration frequency is 20 Hz, the proposed piezoelectric ceramic sheets also reveal a good energy harvesting performance at the maximum output peak voltage of 4.6 V, which is large enough and can be applied in modern low-power electronic products.

Ultra-high polarity ceramics induced extrinsic high permittivity of polymers contributing to high permittivity of 2–2 series composites

Induced polarization at interface has been confirmed to have significant impact on the dielectric properties of 2–2 series composites bearing Si-based semi-conductor sheet and polymer layer. By compositing, the significantly elevated high permittivity in Si-based semi-conductor sheet should be responsible for the obtained high permittivity in composites. In that case, interface interaction could include two aspects namely a strong electrostatic force from high polarity polymeric layer and a newborn high polarity induced in Si-based ceramic sheet. In this work, this class of interface induced polarization was successfully extended into another 2–2 series composite system made up of ultra-high polarity ceramic sheet and high polarity polymer layer. By compositing, the greatly improved high permittivity in high polarity polymer layer was confirmed to strongly contribute to the high permittivity achieved in composites. In this case, interface interaction should consist of a rather large electrostatic force from ultra-high polarity ceramic sheet with ionic crystal structure and an enhanced high polarity induced in polymer layer based on a large polarizability of high polarity covalent dipoles in polymer. The dielectric and conductive properties of four designed 2–2 series composites and their components have been detailedly investigated. Increasing of polymer inborn polarity would lead to a significant elevating of polymer overall polarity in composite. Decline of inherent polarities in two components would result in a mild improving of polymer total polarity in composite. Introducing of non-polarity polymeric layer would give rise to a hardly unaltered polymer overall polarity in composite. The best 2–2 composite could possess a permittivity of ∼463 at 100 Hz 25.7 times of the original permittivity of polymer in it. This work might offer a facile route for achieving the promising composite dielectrics by constructing the 2–2 series samples from two high polarity components.

A novel strategy to increase separated electron–hole dipoles in commercial Si based solar panel to assist photovoltaic effect

Interface induced polarization has been found to have a significant impact on dielectric properties of 2-2 type polymer composites bearing Si based semi-conducting ceramic sheets. Inherent overall polarity of polymer layers in 2-2 composites has been verified to be closely connected with interface effect and achieved permittivity in composites. In present work, conducting performances of monocrystalline Si sheets coated by varied high polarity material layers were deeply researched. The positive results inspired us to propose a novel strategy to improve separated electron–hole dipoles in commercial Si based solar cell panel for assisting photovoltaic effect, based on strong interface induced polarization. Conducting features of solar panels coated by two different high polarity polymer layers were detected to be greatly elevated compared with solar panel standalone, thanks to interface induced polarization between panel and polymer. Polymer coating with higher polarity would lead to more separated electron–hole dipole pairs in solar panel contributing to higher conductivity of panel. Valid synergy of interface effect and photovoltaic effect was based on their unidirectional traits of electron transfer. Dielectric properties of solar panels in composites further confirmed that strategy. This work might provide a facile route to prepare promising Si based solar panels with higher photoelectric conversion efficiency by enhancing interface induced polarization between panel and polymer coating.

Micro-channel formation on NiCuZn ferrite green sheets prepared by hot embossing

Abstract Preparing micro-channels for LTCC using hot embossing technology has become increasingly important. Hot embossing has been applied to fuel-cells, bio-medical devices and sensors. This study focuses on the organic vehicle composition, hot-embossing temperature, pressure and ceramic green sheet thickness effects on embossed green sheet micro-channel resolution. The results show that (1) the hot-embossing pressure mainly affects the micro-channel depth. The hot-embossing temperature predominantly affects the micro-channel depth and width. (2) Green sheets with plasticizer/binder (P/B) = 3/7 exhibited higher stiffness and lower ultimate tensile fracture strain leading to better embossed micro-channel resolution; (3) the embossed micro-channel resolution increased and the number of cracks in the green sheet decreased with increasing green sheet thickness.

Development of multilayer imprint process for solid oxide fuel cells

Solid oxide fuel cells (SOFCs) are fuel cells made of ceramics. To increase the SOFC energy density, we developed an SOFC with a wavy electrolyte layer. As a wavy electrolyte has a larger reaction surface area than a flat electrolyte, a higher energy density could be obtained. Our proposed process is named micro-powder imprint (µPI) with a multilayer imprint process that is useful for fabricating a microscale pattern on a ceramic sheet such as an SOFC electrolyte layer. µPI is based on nanoimprint lithography; therefore, it also exhibits the same advantages of high resolution and mass productivity. The starting material for µPI is a compound sheet containing ceramic powder and binder materials consisting of thermoplastic resin. In this study, two different sheets were stacked into one sheet as a multilayer sheet for the µPI process to form a wavy compound sheet. As the initial state of the stacked sheet, including the mechanical properties of each layer, affects the final wavy shape, we changed the material composition. As a result, the SOFCs unit cell with a wavy electrolyte was fabricated. Note that the anode layer was formed at the same time. After adding the cathode layer, we succeeded in preparing a complete cell for testing power generation.

Pilot-scale test of industrial wastewater treatment by UASB and MBR using a ceramic flat sheet membrane for water reuse

Abstract A pilot plant was studied to investigate a new method for reclaiming wastewater from the industrial area of Jurong, producing high quality water from it for industrial reuse. The new process used an up-flow anaerobic sludge blanket (UASB) and a membrane bioreactor (MBR) with a submerged ceramic flat sheet membrane. The feedwater from the chamber with the industrial wastewater was high in chemical oxygen demand (COD), which varied between 644 and 2,380 mg L–1 and had a pH range of 6.7–7.1. The MBR process was operated in series at a flux of 18–25 Lm–2 h–1 for 100 days. The average COD and the biological oxygen demand of products of the above system were 155 and 9 mg L–1, respectively. The results of this study indicated that a UASB-ceramic MBR process was capable of stably producing high quality water for industrial reuse from industrial wastewater.

Tape casting and characterization of Li2.08TiO3-LiF glass free LTCC for microwave applications

Li2.08TiO3-LiF Glass-free Low temperature co-fired ceramic (LTCC) green tapes were prepared by tape casing technique. The rheology of the slurry was characterized using rheometer. The slurry exhibited pseudoplastic behavior. The sintering kinetics of the green tape was investigated using heating microscope. The sintering activation energy was determined to be ∼173kJ/mol. The green tape could be densified at 900°C/2h. Microwave dielectric properties of the sintered tape were characterized in a split-post dielectric resonator using a network analyzer. The ceramic sheet with thickness of 0.11mm demonstrated good microwave dielectric properties: εr=22.4 and Q×f=35,490GHz. The cross sectional microstructure of the cofired multilayer stack was observed by scanning electron microscopy (SEM). The green tape demonstrated good chemical and shrinkage compatibilities with Ag electrode during sintering process. The thermal expansion coefficient and thermal conductivity of the ceramic is 22.4ppm/∘C and 4.75Wm−1K −1, respectively.

Splitting of glass and SiC ceramic sheets using controlled fracture technique with elliptic microwave spot

This paper presents an alternative splitting method of both thick glass (transparent material) and Sic ceramic (non-transparent) sheets without causing removal of material based on controlled fracture technique with elliptic microwave spot. This method is called as MISM (Microwave Induced Split Method) for short. First, the fact of that 2.45GHz microwave could volumetrically heat 10-mm thickness NaCa glass and Sic ceramic sheets is theoretically proved. Then MISM physical model and corresponding apparatus is developed. Simulating of distribution of power loss density of microwave spot in the physical model is performed. Simulating results shows that an elliptic volumetrically heating microwave spot is obtained, which is testified by measured temperature distribution on the input and output surface of sheet. NaCa glass sheets with max thickness of 4mm and Sic sheets with max thickness of 3mm are both split without causing removal of material. The split line is straight. The split procedure is as same as the procedure of controlled fracture technique with laser spot. The sub-processes of split were related with the movement of three parts of elliptic microwave spot.