Thin-walled and large-sized magnesium alloy die castings for passenger car cockpit:Application,materials,and manufacture

In order to effectively reduce energy consumption and increase range mile,new energy vehicles represented by Tesla have greatly aroused the application of integrated magnesium(Mg)alloy die casting technology in automobiles.Previously,the application of Mg alloys in automobiles,especially in automotive cockpit components,is quite extensive,while it has almost disappeared for a period of time due to its relatively high cost,causing a certain degree of information loss in the application technology of Mg alloy parts in automobiles.The rapid development of automotive technology has led to a higher requirement for the automotive components compared with those traditional one.Therefore,whatever the components themselves,or the Mg alloy materials and die casting process have to face an increasing challenge,needing to be upgraded.In addition,owing to its high integration characteristics,the application of Mg alloy die casting technology in large-sized and thin-walled automotive parts has inherent advantages and needs to be expanded urgently.Indeed,it necessitates exploring advance Mg alloys and new product structures and optimizing die casting processes.This article summarizes and analyzes the development status of thin-walled and large-sized die casting Mg alloy parts in passenger car cockpit and corresponding material selection methods,die casting processes as well as mold design techniques.Furthermore,this work will aid researchers in establishing a comprehensive understanding of the manufacture of thin-walled and large-sized die casting Mg alloy parts in automobile cockpit.It will also assist them in developing new Mg alloys with improved comprehensive performance and new processes to meet the high requirements for die casting automotive components.

Retrospect and Prospect of Excitation Systems of Large Size Turbogenerators

This paper briefs the developmental course, manufacturing and applications, as well as future prospect of excitation systems of large size turbogenerators in China, emphatically expounds the advantages of seif-excitation systems with potential source reetifiers and matters needing to be noted during dissemination and application of them.

Preparation of crystalline rare earth carbonates with large particle size from the lixivium of weathered crust elution-deposited rare earth ores

Crystalline rare-earth(RE)carbonates having large particle size were prepared from the lixivium of weathered crust elution-deposited rare-earth ores using the precipitation method with ammonium bicarbonate as the precipitant.Their chemical composition was studied using elemental and thermogravimetric analyses(TGA),and their structure and morphology were characterized using Fourier transform infrared(FTIR)spectroscopy,X-ray diffraction(XRD),and scanning electron microscopy(SEM).The results demonstrate that the crystalline rareearth carbonate is a hydrated basic carbonate or oxycarbonate and not astable intermediate carbonate in the process of thermal decomposition.The particle size of crystalline rare-earth carbonates with large particle size is in the range of 50–200μm.With an RE2O3 content of up to 95wt%,the quality of crystalline rare-earth carbonates is higher compared to the Chinese National Standard(GB/T 28882–2012).The quality of the product is superior to the Chinese National Standard.

Ice Resistance Assessment for a Large Size Vessel Running in a Narrow Ice Channel Behind an Icebreaker

Large size vessels sailing in continuous level ice and broken ice of high concentration are mostly assisted by icebreakers.This is done in order to provide for fast transportation through the North Sea Route and safe operation in extreme ice conditions.Currently,new large size gas and oil carriers and container ships are being designed and built with beams much greater than the beams of existing icebreakers.At the same time,no mathematical description exists for the breaking mechanism of ice channel edges,when such vessels move under icebreaker escort.This paper suggests a simple method for assessment of the ice resistance in the case of a large ship running in an icebreaker channel;the method is based on modification of well-known semi-empirical methods for calculation of the ice resistance to ships in level and broken ice.The main feature of the proposed calculation scheme consists in that different methods are applied to estimate the ice resistance in broken ice and due to breaking of level ice edges.The combination of these methods gives a deliverable ice resistance of a large size vessel moving under icebreaker assistance in a newly made ice channel.In general,proposed method allows to define the speed of a carrier moving in an ice channel behind a modern linear icebreaker and could be applied at the ship design stage and during development of the marine transportation system.The paper also discusses the ways for further refinement of the assessment procedure suggested.

Development of a large nanocrystalline soft magnetic alloy core with highμ'_(p)Qf products for CSNS-Ⅱ

A waterproof nanocrystalline soft magnetic alloy core with a size of O.D.850 mm×I.D.316 mm×H.25 mm for radio frequency acceleration was successfully developed by winding 18μm 1k107b MA ribbons.Theμ'_(p)Qf products reached 7.5,10,and 12 GHz at 1,3,and 5 MHz,respectively.Theμ'_(p)Qf products of the MA core(O.D.250 mm×I.D.100 mm×H.25 mm)manufactured using a 13μm MA ribbon further increased by 30%.Detailed improvements on the MA core manufacture process are discussed herein.Continuous high-power tests on the new MA cores demonstrated its good performance of waterproofness,particularly its stability of highμ'_(p)Qf products.The MA core with highμ'pQf product and large size can operate under a high average RF power,high electric field,and in deionized water,which will be used in the China Spallation Neutron Source PhaseⅡ(CSNS-Ⅱ).

Spray deposition for making large size billet with swing atomizer

The movement mode of the atomizer is a very important parameter during spray deposition process,which has direct influence on the size and surface texture of the billets. To resolve the problem of manufacturing large size billets,a method of spray deposition by the atomizer with off-center swing was put forward. The atomizer was driven by the alternating current servomotor to swing within 7° at varying speed. The influence of the atomizer parameters,such as translation of the atomizer,swing angle of the atomizer,substrate falling speed and spraying pressure,on the spray deposition was studied. The optimized parameters of the spray deposition process were obtained. The results show that the large size billets with uniform surface quality can be made through adjusting swing frequency and angle of the atomizer,offset distance of the atomizer and inclined angle of the substrate; the valid spray area will decrease and the dimension of top surface will reduce when pressure is less than 0.4 MPa within certain spray distance; meantime,the moving time and cooling time of the droplets are extended,which will lead to loose structure and bad densification. When the pressure,the swing angle and the eccentric offset of the atomization equal 0.5 MPa,7° and 60 mm,respectively,large size billets with fine texture and diameter of 500 mm can be produced.

A STATISTICAL INVESTIGATION OF FATIGUE CRACK INITIATION AND GROWTH PROCESS BASED UPON A LARGE SAMPLE SIZE EXPERIMENT

After finishing 102 replicate constant amplitude crack initiation and growth tests on Ly12-CZ aluminum alloy plate, a statistical investigation of the fatigue crack initiation and growth process is conducted in this paper. According to the post-mortem fractographic examination by scanning electron microscopy (SEM), some qualitative observations of the spacial correlation among fatigue striations are developed to reveal the statistical nature of material intrinsic inhomogeneity during the crack growth process. From the test data, an engineering division between crack initiation and growth is defined as the upper limit of small crack. The distributions of crack initiation life N-i, growth life N, and the statistical characteristics of crack growth rate da/dN are also investigated. It is hoped that the work will provide a solid test basis for the study of probabilistic fatigue, probabilistic fracture mechanics, fatigue reliability and its engineering applications.

Holistic Approaches for Renovation of Large Housing Areas in Japan

Social imbalance and obsolescence of the built environment has emerged in large sized housing estates in metropolises. In particular, the requirement of such planned housing areas has not matched public service provided by the infrastructure. On not only physical but also social aspect of local communities of this kind of housing area have a lot of problems while it also has a lot of good characteristics. A representative one is that age of the tenants is rising very swiftly and it makes the local community imbalanced. Nowadays many countries including Japan have tackled problems concerning housing estates constructed during the mass housing era and try to search for ways to reactivate so-called new town areas by utilisation of existing environmental resources such as building stock and ample green open space. In Japan many elemental technologies have been developed in order to utilise existing building stock. However, how to combine these technologies and new holistic methods for reactivation are still underdeveloped. Therefore, it is very important to fred these ways and to make a comprehensive plan for rehabilitation of these areas. The first purpose of our study is to develop and clarify how to organise and integrate many kinds of elemental techniques and the holistic measures for the improvement of both social and physical environment in suburban mass housing estates. Subsequently we try to reorganise proper relations between human settlements and the various service provision for those regions. Our last focus is put on searching for new ways to raise the value of existing housing environment. Our conclusion intends to indicate important of the master plan and its execution, where mass housing estates progress for the physical and social improvement.

A novel synthesis of highly active and highly stable non-noble-nickel-modified persulfated Al_(2)O_(3)@ZrO_(2) core-shell catalysts for n-pentane isomerization

The non-noble metal modified sulfated zirconia was found easy to deactivate.Herein,highly active and highly stable non-noble core-shell Ni-S_(2)O_(8)^(2−)/Al_(2)O_(3)@ZrO_(2) catalysts(Ni-SA@Z-x,x=Al content in wt%)have been successfully prepared and investigated for n-pentane isomerization.The results showed that the core-shell Ni-SA@Z-30 provided a sustained high isopentane yield(63.1%)with little or no deactivation within 5000 min at a mild reaction pressure of 2.0 MPa,which can be attributed to the following factors:(i)carbon deposition was greatly suppressed by the large pore size and huge pore volume;(ii)the loss of sulfur entities was suppressed because the small and highly dispersed tetragonal ZrO_(2) particles can bond with the S species strongly;(iii)strong Brønsted acidity can be maintained well after the isomerization.The pore structures and acid nature of the core-shell Ni-SA@Z-x are entirely different from those of the normal structure Ni-S_(2)O_(8)^(2−)/ZrO_(2)-Al_(2)O_(3),even though the Al content and the compositions of the individual components are the same.The Al_(2)O_(3)cores endow the catalysts with high internal surface area and high mechanical strength.Meanwhile,the ZrO_(2) shell,which consists of more and smaller tetragonal ZrO_(2) particles because of the large surface area of the Al_(2)O_(3)core,promotes the formation of more stable sulfur species and stronger binding sites.

Large‑Sized High‑Efficiency Fiber Perovskite Solar Cells Fabricated by Automatic Thin‑Film Coating on Curved Surfaces

Perovskite solar cells in a fiber format have great potential for wearable electronics due to their excellent flexibility,efficient light harvesting,and potentially high power conversion efficiency(PCE).However,the fabrication of large-sized fiber perovskite solar cells(FPSCs)while maintaining high efficiency remains a major challenge because of the difficulty in the formation of uniform crystalline perovskite films on highly curved surfaces.Here,we report a scale-up automatic approach for the fabrication of large-sized FPSCs via sequential coating of active layers on fiber substrates and posttreatment of perovskite films.We focus on understanding the perovskite film formation process on fibers and manage to control the film thickness,morphology,and crystallinity by adjusting the coating speed,precursor solution aging time,and posttreatment.As a result,a 20.0-cm-long FPSC with a PCE of 7.63%is achieved,and this length is almost ten times longer than those of the previously reported FPSCs.Our work represents a breakthrough in fabricating large-sized high-efficiency FPSCs,which will ultimately lead to practical applications of FPSCs.

Lightweight and large-scale rGO reinforced SiBCN aerogels with hierarchical cellular structures exposed to high-temperature environments

SiBCN ceramic aerogel is an ideal potential candidate for ultra-high temperature thermal insulation due to its unique microscopic pore structure combined with the excellent thermal stability of SiBCN ce-ramic.Here,reduced graphene oxide(rGO)modified SiBCN aerogels(rGO/SiBCN)were prepared through solvothermal,freeze-casting and pyrolysis,and the dimension of the aerogel is up toΦ130 mm×28 mm.The density of the rGO/SiBCN aerogel is as low as 0.024 g/cm^(3) and the microstructural regulation is achieved by controlling the rGO content in the aerogel.The hierarchical cellular structure endows the aerogel with a high specific surface area(148.6 m^(2)/g)and low thermal conductivity(0.057 W m^(-1) K^(-1)).The 10 mm-thick sample exhibits excellent thermal insulation and ablation resistance,as evidenced by its ability to reduce the temperature from~1100℃to~180℃under the intense heat of a butane flame.Moreover,benefiting from the ultrahigh-temperature stability of SiBCN,the rGO/SiBCN aerogel exhibits good thermal stability up to 1200℃in argon and short-oxidation resistance at 800℃in air.There-fore,the rGO/SiBCN aerogel with superior overall performance could expand its practical application in high-temperature thermal insulation under extreme environments.

A judicious approach to induce large size growth of hydroxyapatite via applying graphene modified silicon nitride nanowires

Mimicking the structure of natural bone collagen fibers/hydroxyapatite(HA)to synthesize large size of HA for accelerated bone repair remains a challenge.Herein,silicon nitride nanowires(SN)-graphene(GE)was designed by the chemical vapor deposition,forming SN-GE(SG)similar to collagen fibers.Then,the large size HA was assembled onto SG by pulsed electrochemical deposition,the SG/HA(SGH)mimics the collagen fibers/HA structure of bone.The introduction of SG induces HA to large size grow in the form of coral-like.HA can be grown on a large size inextricably with the existence of GE modified layers.On the one hand,the upright GE sheets effectively increases the surface roughness which enhances the nucleation site of HA.On the other hand,the C=O provides chemical bonding and induces HA nucle-ation.Compared with SN/HA(SH),the porosity of SGH decreased by 71%.The average diameter of the SGH is(9.76±0.25)mm.Compared with SH,the diameter of SGH is 22 times larger than the diameter of SH.Indicating that SG induces large size growth of HA.Our work can provide a general strategy for the efficient preparation of biological scaffolds with large size HA that can be used in bone tissue engineering.

Salt-assisted growth and ultrafast photocarrier dynamics of large-sized monolayer ReSe2

Owing to its anisotropic optical and electrical properties,rhenium diselenide(ReSe2)has garnered considerable attention recently as a candidate material for polarization-sensitive photodetectors.However,the direct and controllable synthesis of large-sized ReSe2 with a uniform thickness is still a great challenge.Herein,we have refined the synthesis method to obtain uniform monolayer ReSe2 flakes with a size of up to^106μm on sapphire via an ambient-pressure chemical vapor deposition technique using Na promoter from sodium chloride.Interestingly,optical pump-probe spectroscopy revealed a fast switching from saturable absorption(SA)to absorption enhancement(AE)in subpicosecond time scale,followed by a slower decay induced by exciton recombination.Furthermore,both AE and SA signals exhibited clear angular dependence with a periodicity of 180°,which reflected the dichroism in nonlinear absorption dynamics.In addition,the photocarrier dynamics including free-carrier transport and subpicosecond relaxation due to exciton formation or surface trapping was probed using time resolved terahertz spectroscopy.We believe that our study serves as a reference for atomically controlled synthesis of large-sized ReSe2 and provides useful insights on its optoelectronic properties for novel device applications.

Thermal performance analysis of borehole size effect on geothermal heat exchanger

Thermal performance was the most important factor in the development of borehole heat exchanger utilizing geothermal energy. The thermal performance was affected by many different design parameters, such as configuration type and borehole size of geothermal heat exchanger. These eventually determined the operation and cost efficiency of the geothermal heat exchanger system. The main purpose of this work was to assess the thermal performance of geother^nal heat exchanger with variation of borehole sizes and numbers of U-tubes inside a borehole. For this, a thermal response test rig was established with line-source theory. The thermal response test was performed with in-line variable input heat source. Effective thermal conductivity and thermal resistance were obtained from the measured data. From the measurement, the effective thermal conductivity is found to have similar values for two- pair type （4 U-tubes） and three-pair type （6 U-tubes） borehole heat exchanger systems indicating similar heat transfer ability. Meanwhile, the thermal resistance shows lower value for the three-pair type compared to the two-pair type. Measured data based resistance have lower value compared to computed result from design programs. Overall comparison finds better thermal performance for the three-pair type, however, fluctuating temperature variation indicates complex flow behavior inside the borehole and requires further study on flow characteristics.

Enlarging grain sizes for efficient perovskite solar cells by methylamine chloride assisted recrystallization

The quality of MAPbI3 film prepared by solvent engineering process highly depends on environment and antisolvent control.Here,we provided a simple methylamine chloride(MACl)solution treatment using a two-step process to enlarge the perovskite crystal grain sizes to more than 1 lm.Other than treatment on the film surface,the MACl solution diffuses into the MAPbI_(3) films to assist the recrystallization of small crystal at the bottom of perovskite film.The imitative contact between perovskite and substrate is formed.Meanwhile,the enlargement of grain size and ten times enhancement of crystalline reduce trap-assisted recombination of perovskite films.Thus,the significant improvement of cell efficiency of 20.89%as well as device stability is obtained with the MACl treatment.

High interfacial-energy heterostructure facilitates large-sized lithium nucleation and rapid Li+desolvation process

High interfacial energy Li^(0)-electrolyte interface contributes to larger Li^(0) nucleation embryos and a more stable interface,so the interfacial energy is essential for highly reversible Li^(0) deposition/stripping.Herein,a high interfacial-energy artificial solid electrolyte interphase(SEI)with rich LiF embedded in lithiated poly-2-acrylamido-2-methylpropane sulfonic acid(PAMPS-Li)network is designed to realize favorable Li^(0) nucleation and rapid desolvation of Li+simultaneously.The Li-F bonds in LiF(001)exhibit stronger ion-dipole interactions with Li atoms,offering higher interfacial energies.When the growth surface energy and total interfacial energy of Li^(0) are balanced,the high interfacial energy SEI with abundant LiF can promote the formation of larger Li^(0) nucleation embryos.In addition,the PAMPS-Li with immobilized anions presents weaker interaction with Li^(0) and possesses higher polymer-Li interfacial energy,and its amide and sulfonic acid groups exhibit higher binding energies with Li^(+).Therefore,PAMPS-Li can easily promote the Li+to escape from the solvent sheath and weaken the desolvation energy barrier.The highly reversible Li^(0) deposition behavior with restricted side reactions is achieved based on the synergistic modification of high interfacial energy SEI with heterostructure.Most importantly,lifespan of multi-layered Li^(0) pouch cell(330 Wh kg-1)with a low N/P ratio(1.67)is over 100 cycles,verifying its potential practical application.

BASIC HYDRODYNAMICS CHARACTERISTICS OF CAVITY SPIRAL FLOW IN A LARGE SIZE LEVEL PIPE

Based on the observation of a model test and in combination with some theoretical analysis, the researches of some basic hydrodynamics characteristics of cavity spiral flow in a large size level pipe with a shaft-inlet is presented in the paper, which include the basic flow pattern, formation condition of the cavity spiral flow, discharge Q, cavity diameter d0, wall pressure coefficient Cpw, velocity distribution, total energy dissipation rate η etc. The results show that the basic flow patterns can be divided into three zones according to the variations in amount of ventilation Ф, cavity diameter d0 and gas pressure p0 within cavity spiral flow when the upstream and downstream water level changes and that the basic hydrodynamics characteristics change with the flow pattern and have the different behaviour.

Experimental and numerical research on squat silo and large size horizontal warehouse during quasi-steady-state storage

Traditional method to prevent stored grain from deterioration is to control grain temperature.A three dimensional(3-D)numerical model was established to study the temperature variation in outdoor squat silo and large size horizontal warehouse at quasi-steady-state.In this research,porous media model and solar radiation model were adopted.Numerical and experimental results showed that grain temperature was influenced by temperature of wall,height of grain and the distance between grain and the wall.Temperature changes dramatically at the top layer of grain heap due to solar radiation and heat convection at air layer.Temperature of grain close to wall increased with the increasing of ambient temperature.The model established in this research is suitable for predicting grain temperature in outdoor squat silo and large size horizontal warehouse.

Preparation of large size ZTA ceramics with eccentric circle shape by microwave sintering

Ultra-large zirconia toughened alumina (ZTA,mass ratio of Al2O3 and ZrO2 is 78∶22) ceramics with eccentric circle shape were successfully sintered by microwave sintering with a multi-mode cavity at 2.45 GHz.The dimension of ZTA ceramics (green body) is 165 mm (outer diameter) × 25 mm (thickness).The optimized sintering temperature of microwave sintering is about 1500 ℃ for 30 min,and the total sintering time is about 4 h which is much shorter than that of conventional sintering.An auxiliary-heating insulation device was designed based on the principle of local caloric compensation to guarantee the intact sintered samples.With the increasing of sintering temperature,more and more microwave energy is absorbed within the entire sample,volumetric densification performs,and phases shift from m-ZrO2 phase to t-ZrO2 phase and cause Al2O3 grain growth.