- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
SUBSTRATE INTEGRATED WAVEGUIDE FILTER WITH IMPROVED STOPBAND PERFORMANCE USING LTCC TECHNOLOGY
摘要： A novel multi-layer third-order substrate integrated waveguide (SIW) bandpass ?lter with improved lower stopband performance is proposed. TE201-mode in folded-SIW cavity is utilized to implement negative cross coupling, and the TE101-mode is taken as a non-resonating node (NRN) for implementing bypass coupling. A circular aperture etched on the middle metal layer is used to realize coupling between source and the second SIW cavity. Then, three transmission zeros located below the passband can be obtained to improve stopband attenuation. Meanwhile, better spurious suppression performance above passband is achieved. A ?lter sample is designed and fabricated with multi-layer low-temperature co-?red ceramic (LTCC) technology. The measured S-parameters agree well with the simulated ones, with its predicted good performance.
关键词： transmission zeros,low-temperature co-?red ceramic (LTCC),Substrate integrated waveguide (SIW),bandpass ?lter,stopband performance
更新于2025-09-11 14:15:04
-
Preparation of high-porosity Al2O3 ceramic foams via selective laser sintering of Al2O3 poly-hollow microspheres
摘要： In this paper, high-porosity Al2O3 ceramic foams called Al2O3 PHM ceramics were fabricated through selective laser sintering (SLS) via Al2O3 poly-hollow microspheres (Al2O3 PHMs). SLS parameters were optimized by an orthogonal experiment as laser power = 6 W, scanning speed = 1800 mm/s, and scanning space = 0.15 mm. The effect of sintering temperature on microstructure, shrinkage, porosity, phase composition, mechanical properties and pore size distribution of Al2O3 PHM ceramics were investigated. When sintering temperature increased, Al2O3 PHM ceramics contained only Al2O3 phase and were gradually densified. With the raise of sintering temperature, the porosity of Al2O3 PHM ceramics decreased gradually from 77.09% to 72.41%, but shrinkage in H direction and compressive strength of Al2O3 PHM ceramics increased from 6.63% and 0.18 MPa to 13.10% and 0.72 MPa, respectively. Sintering temperature had little effect on pore size distribution of Al2O3 PHM ceramics, which only declined from 24.2 to 21.4 μm with the increase of sintering temperature from 1600 to 1650 °C. This method can not only directly prepare ceramic foams with complex shapes, but also control properties of ceramic foams. It provides a simple preparation method for many kinds of ceramic foams with complex structure and high porosity by using PHMs with different composition.
关键词： Selective laser sintering,Porosity,Poly-hollow microsphere,Ceramic foams,Mechanical properties
更新于2025-09-11 14:15:04
-
[IEEE 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Atlanta, GA, USA (2019.7.7-2019.7.12)] 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Grounded Coplanar Waveguide-Fed Millimeter Wave Volumetric Pyramidal Horn on LTCC
摘要： There is a strong interest to implement antenna-in-package (AiP) systems for a variety of applications such as imaging, beamforming, integrated transceivers, and radars. Substrate integrated horn antennas are valuable AiP candidates due to their small form factor, ease of integration, and high gain. Alternatively, a volumetric packaging approach can significantly reduce the antenna’s form factor and enhance the gain. For the first time, in this paper, we present a 94 GHz low temperature cofired ceramic (LTCC) integrated volumetric pyramidal horn antenna. Using a vertical LTCC approach, a GCPW-fed single horn antenna was designed. Results show that the antenna operates from 91.6 GHz to 95.6 GHz for S11 <10 dB, with a realized gain of 8.7 dBi.
关键词： Antenna in Package,Low Temperature Co-fired Ceramic (LTCC),Volumetric Horn Antenna,94 GHz
更新于2025-09-11 14:15:04
-
[IEEE 2019 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM) - Hong Kong, China (2019.7.8-2019.7.12)] 2019 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM) - Determination of Noise Index of Piezoelectric Ceramic Drive System Based on Coupled Electro-mechanical Model
摘要： Piezoelectric ceramic （PZT） driver is a key component in PZT micro-displacement systems, and the noise index determines the accuracy of the output displacement of the PTZ actuator. In fast steering mirror（FSM） systems, the response of noise in a mechanical system is bound to affect resolution of the system. This paper analyzes the PZT driver system from the perspective of coupled electro-mechanical. By establishing a mathematical model of the coupled electro-mechanical system, we determine the energy of the output noise of the drive system in the mechanical system and the transfer of the electrical noise energy on the electromechanical system actuator. It is then determined that the power consumption of the PTZ actuator is mainly composed of two parts: the energy used to drive the deformation of the system and the dissipation of heat due to structural damping. The noise index of the PTZ driver system is 192.3dB when the accuracy of the output displacement is 1 nm through the energy conversion. The method is universal to be applied to determine the system noise index in various mechatronic systems, as well as to more complex mechanical systems.
关键词： Piezoelectric ceramic driver,coupled electro-mechanical,noise index
更新于2025-09-11 14:15:04
-
Transparent Urethane Siloxane Hybrid Material for Flexible Cover Window with Ceramic-like Strength, yet Polymer-like Modulus
摘要： Any transition toward an era of flexible electronics will have to overcome mechanical limitations of materials. Specifically, the attainment of both strength and flexibility, which are generally mutually exclusive, is required including glass-like wear resistance, plastic-like compliance and a high level of strain. Here, we fabricate a urethane-methacrylate siloxane hybrid material (UMSH). It is found that the UMSH, with molecule-level hybridization of urethane linkage and methacrylate-siloxane co-networks, demonstrates ceramic-like high strength (574 MPa), yet polymer-like low modulus (8.42 GPa), and even high strain (6.3%) at fracture with excellent optical transparency. This combination of high strength, flexibility and optical transparency indicates that this is a suitable material for glass substitution and can be used as a transparent flexible cover window for foldable display.
关键词： ceramic-like strength,polymer-like modulus,Flexible cover window,molecular hybridization,urethane-methacrylate siloxane hybrid
更新于2025-09-11 14:15:04
-
Computational design of microstructures of textured ferroelectric ceramics by phase field simulation
摘要： Grain-oriented microstructure evolutions of ferroelectric ceramics were analyzed using phase field simulations. In templated grain growth, the coarsening behavior of the template particle was investigated in detail. Although a large grain boundary energy was set in the lateral direction along the casting plane, the template particle grew mainly in the vertical direction and gradually converted from a needle-like to rectangular grain. We demonstrated a critical interval of template particles for the preparation of highly textured ceramics. Therefore, different microstructures with high degrees of texture could be fabricated by adjusting and controlling the template size and fraction. Complementary experiments were guided by the computational design. Dense ferroelectric ceramics with high degrees of texture were obtained.
关键词： Templated grain growth,Ferroelectric ceramic,Textured ceramic,Computer simulation
更新于2025-09-10 09:29:36
-
Experimental investigations on super-smooth polishing of strontium titanate based ceramics substrates
摘要： Strontium titanate (SrTiO3) is a new type of multi-function electronic ceramic material. SrTiO3 ceramic substrates with a high dielectric constant can be obtained by non-pressurised sintering using ultrathin blanks, which result in the characteristics of thin, soft, brittle and warped. So that SrTiO3 ceramics substrates need to be polished to improve surface quality and dimensional precision before application. In this research, polish experiments with various processing parameters on the surface roughness, the material removal rate and the surface morphologies of SrTiO3 ceramic substrates were conducted. The results show that the SrTiO3 ceramic substrate with a highest quality surface was obtained in the condition: employing a brown polyurethane pad to polish the substrates at a polishing velocity of 45 r/min. Meanwhile, the slurry flow rate, the concentration of the polishing slurry and the polishing pressure were 20 ml/min, 4 wt% and 15.043 kPa, respectively, which rates with an overall and a partial surface roughness of Ra 0.01 μm and Ra 4 nm, respectively. While some new micro-scratches were generated on the surface of the SrTiO3 ceramics substrate in the polishing process because the embedding and scratching of abrasive particle led to expose the inherent pores and grain boundaries.
关键词： ceramic substrate,material removal rate,strontium titanate,polishing,surface roughness
更新于2025-09-10 09:29:36
-
Effect of calcium oxide doping on the microstructure and optical properties of YAG transparent ceramics
摘要： Yttrium aluminium garnet (YAG, Y3Al5O12) transparent ceramics were fabricated by vacuum sintering the co-precipitated raw powders with calcium oxide (CaO) as the sintering aid. The influence of CaO content on the phase composition, particle size and the morphologies of resultant YAG powders, as well as the microstructural and optical properties of YAG ceramics, was investigated in detail. Our results show that with increasing of CaO additives, the particle size and agglomeration degree of the powders were slightly increased and the grain growth of the ceramics was inhibited. Specifically, the grain size initially decreased dramatically till reaching a minimum value of 1.85 μm with 0.3 at% CaO, then slightly increased. In addition, for YAG ceramics with a high CaO doping level, the existence of liquid phase was observed for the first time and its sintering mechanism was discussed. The excess of CaO causes the formation of grain boundary phases and residual pores, which are detrimental for maintaining higher optical quality of YAG ceramics. We obtained a fully dense and pore-free YAG ceramic with an in-line transmittance of 80.8% at 1100 nm by adopting 0.1 at% level of CaO during sintering of the green bodies at 1780°C for 20 h in vacuum.
关键词： Microstructure evolution,YAG transparent ceramic,Co-precipitation method,CaO additives
更新于2025-09-10 09:29:36
-
Analysis of the damage initiation in a SiC/SiC composite tube from a direct comparison between large-scale numerical simulation and synchrotron X-ray micro-computed tomography
摘要： Damage initiation is an important issue to understand the mechanical behavior of ceramic matrix composites. In the present work, a braided SiC/SiC composite tube was studied by FFT simulation tightly linked with micro-computed tomography (μCT) observations performed during an in situ uniaxial tensile test, which provide both the real microstructure, with a good description of local microstructural geometries, and location of cracks at the onset of damage. The FFT method was proven applicable to tubular structures and efficient to complete the large-scale simulation on a full resolution μCT scan (~6.7 billion voxels) within a short time. The edge effect due to the numerical periodic boundary conditions prescribed on the real and not rigorously periodic microstructure was quantified. The obtained stress field was compared to the cracks detected by the in situ μCT observations of the same composite tube. This one-to-one comparison showed that cracks preferentially initiated at tow interfaces, where sharp edges of macropores are mostly located and generate stress concentrations.
关键词： Damage initiation,FFT simulation,Ceramic matrix composite,In situ tensile test,Tomography,Porosity effect
更新于2025-09-10 09:29:36
-
Cool and photocatalytic yellow ceramic pigments; from lead-tin to Cr doped scheelite pigments
摘要： The historical lead based pigments (XVII-XVIII century), the modern Ni,Sb-rutile (1939) and Pr-zircon (1961) yellow pigments as well as the novel yellow pigments based on Cr-scheelite and Mo-yttrium cerate pigments were synthesised and compared as semiconductors of high NIR reflectance (cool pigments) and with photocatalytic activity. All powders are wide band gap semiconductors (Eg=2.1-3.1 eV) with high NIR reflectance, ranging from 80% for Cr-Scheelite to 86% of Naples yellow, except Ni,Sb-rutile pigment that shows 55%. The low color performance of lead based pigments in alkyd paint and lead-free glazes along with its toxicity, discard these pigments as cool eco-friendly pigments. The Pr-zircon, Cr-scheelite and Mo-yttrium cerate pigments exhibit high NIR reflectance (RNIR=80-83%) and yellow coloration (b*=57.6-45.3) but only Pr-zircon and Cr-scheelite show colour stability in alkyd paint and lead free glaze applications. Regarding to results of Orange II photodegradation test, lead based and Ni,Sb-rutile pigments inhibits the photolysis of the UV irradiation, acting as protecting agents from irradiation. The Mo-cerate shows a slight photocatalytic activity (t1/2 =301 min) and both Cr-scheelite and Pr-zircon pigments show a moderate activity (t1/2 =198 and 184 min respectively). Looking at a possible industrial application, the leaching test shows that the fluorides released by Pr-zircon (16.8 mg/g) as well as the Cr(VI) of Cr-scheelite (6 mg/g) should be treated and controlled. The Cr-scheelite solid solution Ca(CrxW1-x)O4 is stable to x=0.2 but its pigmenting capacity saturates at x=0.1.
关键词： cool pigment,ceramic pigment,environment,photocatalysis
更新于2025-09-10 09:29:36