Ultra-low temperature cofired ceramics based on Li_(2)WO_(4)as perspective substrate materials for terahertz frequencies

With the development of low dielectric permittivity materials having an ultra-low sintering temperature,testing their dielectric properties at terahertz frequencies suitable for 6G communication systems and implementation of the fabricated materials in ultra-low temperature cofired ceramics(ULTCC)were the main goals of the research.Lithium tungstate Li_(2)WO_(4)was synthesized by a solid-state reaction and used for the preparation of green tapes and test structures with cofired internal conductive layers,which are destined for substrates of microwave and submillimeter wave circuits.Sintering behavior,thermal effects,and mass changes of the green tapes during heating were studied using a hot-stage microscope,differential thermal analysis,and thermogravimetry.A single-phase composition was revealed for being undoped and doped with AlF3–CaB_(4)O_(7)ceramics.The impact of frequency,temperature,the addition of AlF3–CaB_(4)O_(7)and CuBi_(2)O_(4)dopants,and sintering temperature was the subject of in-depth characterization of dielectric properties in a terahertz region.A glass-free composition,ultra-low sintering temperature of 590–630℃,low roughness of the green tapes,dense microstructure,compatibility with Ag conductors,low and stable dielectric permittivity of 5.0–5.8 in a broad range of 0.2–2 THz,and low dielectric loss of 0.008–0.01 at 1 THz are the main advantages of the developed ULTCC substrates.

Design of Millimeter-Wave Antenna-in-Package(AiP)for 5G NR

For 5G new radio(NR),there are two frequency bands:Frequency Range 1(FR‐1)(low frequency)and Frequency Range 2(FR‐2)(millimeter‐wave frequency).Millimeter‐wave has been officially utilized in mobile applications.The wide bandwidth is the key for the millimeter-wave band.However,higher loss has become the major challenge for the wide use of this frequency range.Antenna array and beamforming technologies have been introduced to resolve the path loss and coverage problems.The key design considerations of the beamforming antenna array are low loss,compact system and small size.Antenna-in-package(AiP)has become the most attractive technology for millimeter-wave front-end system.For the design of AiP,many parameters such as RF transition,material and heat need to be considered and designed properly.The Over‐the‐Air(OTA)testing technology is also very critical for AiP mass production.In this paper,the detail of AiP design and new OTA testing technology are discussed and demonstrated.

Application and Development of LTCC for RFIC

The trend in the radio frequency IC toward further miniaturization and improved performance drives ongoing technology innovation of new substrate and packaging technologies.In this paper,Hardware technology of RF system was reviewed,and the low temperature cofired ceramics(LTCC) technology was stated to be the best choice.Material development and measurement of Dielectric properties of LTCC technology are introduced.The application of passive embedded component was stated for RFIC design.Design of LTCC library will be the next step for RF system design and simulation.

Impact of different kinds of biomass mixtures on combustion performance, interaction and synergistic effects in cofiring of coal and biomass in steam power plants

The cofiring of biomass and coal may be one of the most effective methods to improve energy utilization efficiency and reduce greenhouse gas emissions.This study aims to investigate combustion performance,interaction and synergistic effects in the cofiring of coal and three types of biomass.Blended fuel consisting of coal and three types of biomass such as sawdust,rice husk and solid recovery fuel was selected as the research object.Ultimate and proximate analysis and differential thermogravimetric analysis with heating rates of between 10°C and 40°C/minute are used to analyse combustion characteristics.Simulation of combustion in a 600-MWe steam power plant with a Carolina-type boiler is also carried out with the help of computational fluid dynamic(CFD)analysis to see the effect of the interaction and synergy of the mixed fuel on the performance of the steam generator.The effect on the com-bustion process in the combustion chamber of a steam power plant is also simulated.Based on the analysis of several test results of parameters such as ignition temperature,burnout temperature,calorific value of the fuel mixtures as well as CFD simulation,the results of the study show a strong indication of a positive synergy in mixing some of these biomasses as compared with a fuel mix-ture consisting only of coal and one type of biomass.Practically no power derating of the boiler occurs until the biomass content in the fuel mixture is~30%on a mass basis.The reduction in greenhouse gas emissions also appears significant from the results of the CFD simulation of this study,which is characterized by a decrease in the fraction of CO_(2) in flue gas from 21.5%for coal alone as fuel to 15.9%in the case of cofiring excluding the CO_(2) attributed to the biomass.

Monolithic piezoceramic actuators with a twist

Designing artificial structures with heterogeneous elements and manipulating their interface coupling ways usually bring in synthetic neo-nature to functional devices.For piezoceramic devices,the deformation response refers to a variety of extensional,contractional,or shear modes of crystals,and also relies on boundary conditions from morphology design.However,to pursue fundamental torsion actuation in an integrated piezoceramic component is still a long-term tough task due to nil twist mode limited by microscopic crystal mirror symmetry.Herein,we demonstrate a design of cofired monolithic actuators to originally overcome this obstacle.The prototype device is composed of two sets of stacked actuation subunits that work on artificially reverse face shear modes,and their chiral stiffness couplings will synergistically contribute to synthetic twist outputs at a broad bandwidth.Finite element simulation reveals twist displacements are highly tunable by manipulating the geometrical dimensions.Transverse deflection measurements manifest the stable and sizeable linear actuation response to applied electric fields(around 3.7μm under 40 V at 1 Hz).Importantly,the design actually introduces a more general route to enable arbitrary modes and actuation states in integrated piezoceramic components.

Combining solar power with coal-fired power plants,or cofiring natural gas

Coal-fired power operators continue to look for ways to increase the efficiency and extend the working lives of their plants by improving operational flexibility and reducing environmental impact.Two possible options are explored here:combining solar energy with coal-fired power generation,and cofiring natural gas in coal-fired plants.Both techniques show potential.Depending on the individual circumstances,both can increase the flexibility of a power plant whilst reducing its emissions.In some cases,plant costs could also be reduced.Clearly,any solar-based system is limited geographically to locations that receive consistently high levels of solar radiation.Similarly,although many coal-fired plants already burn limited amounts of gas alongside their coal feed,for cofiring at a significant level,a reliable,affordable supply of natural gas is needed.This is not the case everywhere.But for each technology,there are niche and mainstream locations where the criteria can be met.The need for good solar radiation means that the uptake of coal-solar hybrids will be limited.Cofiring natural gas has wider potential:currently,the largest near-term market appears to be for application to existing coal-fired plants in the USA.However,where gas is available and affordable,potential markets also exist in some other countries.

Low-fired Y-type hexagonal ferrite for hyper frequency applications

Y-type hexagonal ferrite with planar magnetocrystalline anisotropy has ultrahigh cut-off frequency up to GHz and excellent magnetic properties in hyper frequency range,so that is regarded as the most suitable material in correpongding inductive devices and components.The technology of low temperature cofired ceramics for surface-mounted multilayer chip components needs ferrite to be sintered well under 900℃to avoid the melting and diffusion of Ag inner electrode during the cofiring process.To lower the sintering temperature of Y-type hexagonal ferrite,there are several methods,(1)using nano-sized starting powders,(2)substitution by low-melting elements,(3)adding sintering additives,and(4)introducing lattice defect.In this paper,the effects of different methods on the sintering behavior and the magnetic properties were discussed in detail.

Evaluation of trace element mobilization and control under different fluidized bed combustion scenarios

As consequence of its relatively abundant reserves compared to other energy sources,coal will continue to be widely employed in power plants.To reduce coal’s negative impact on the environment,new approaches have been evaluated and adopted by various countries in recent years to minimize CO_(2) emissions.Initial developments focused on the selection of new fuels(such as biomass fuels)to combine with coal to reduce emissions from coal combustion,whereas subsequent approaches aimed at implementing new processes for CO_(2) capture and storage,such as oxy-fuel combustion.In addition,coal combustion is one of the main anthropogenic sources of trace elements(TE)emitted to the atmosphere.The increasing knowledge acquired as to the impact of these pollutants in the environment has led to more restricted emission standards for some of these elements and to increased research on the technologies and pathways to control these emissions.This article reviews the main factors involved in TE capture by comparing results obtained for Hg and other TEs under different control scenarios.Both the effect of novel combustion processes and the potential of different pollution control techniques toward these pollutants are discussed.