Research on Fe-based impregnated diamond drill bits strengthened by Nano-NbC and Nano-WC

In order to improve the matrix performance of impregnated diamond drill bit to better meet the drilling needs,the effects of the addition of nano-WC and nano-NbC particles on the matrix material together with the mechanical properties and microstructure of the diamond-matrix composite material of the Fe-based diamond drill bit were studied by using the method of uniform formula design,regression analysis and solution finding.An indoor drilling test was also carried out using the fabricated impregnated diamond drill bit.The results showed that after the addition of nano-NbC and nano-WC,the hardness and flexural strength of the matrix material got improved,as the flexural strength of the diamond composite material increased to 4.29%,the wear-resistance ratio increased to 8.75%,and the tighter the chemical bonding between the diamond and the matrix.This,indicates that the addition of nanoparticles has a positive significance in improving the performance of the diamond composite.The results of the drilling test showed that the mechanical drilling speed of the impregnated diamond drill bit after nanoparticle strengthening is 25.85%higher than that of the conventional drill bit,and the matrix wear was increased by 17.5%.It proves that nanoparticles can improve the drilling performance and efficiency of drill bit.

Influences of oxide content and sintering temperature on microstructures and mechanical properties of intragranular-oxide strengthened iron alloys prepared by spark plasma sintering

How to increase strength without sacrificing ductility has been developed as a key goal in the manufacture of high-performance metals or alloys. Herein, the double-nanophase intragranular yttrium oxide dispersion strengthened iron alloy with high strength and appreciable ductility was fabricated by solution combustion route and subsequent spark plasma sintering, and the influences of yttrium oxide content and sintering temperature on microstructures and mechanical properties were investigated. The results show at the same sintering temperature,with the increase of yttrium oxide content, the relative density of the sintered alloy decreases and the strength increases. For Fe–2wt%Y_(2)O_(3)alloy, as the sintering temperature increases gradually, the compressive strength decreases, while the strain-to-failure increases. The Fe–2wt%Y_(2)O_(3)alloy with 15.5 nm Y_(2)O_(3)particles uniformly distributed into the 147.5 nm iron grain interior sintered at 650℃ presents a high ultimate compressive strength of 1.86 GPa and large strain-to-failure of 29%. The grain boundary strengthening and intragranular second-phase particle dispersion strengthening are the main dominant mechanisms to enhance the mechanical properties of the alloy.

Nano-additive manufacturing of multilevel strengthened aluminum matrix composites

Nanostructured materials are being actively developed,while it remains an open question how to rapidly scale them up to bulk engineering materials for broad industrial applications.This study propose an industrial approach to rapidly fabricate high-strength large-size nanostructured metal matrix composites and attempts to investigate and optimize the deposition process and strengthening mechanism.Here,advanced nanocrystalline aluminum matrix composites(nanoAMCs)were assembled for the first time by a novel nano-additive manufacturing method that was guided by numerical simulations(i.e.the in-flight particle model and the porefree deposition model).The present nanoAMC with a mean grain size<50 nm in matrix exhibited hardness eight times higher than the bulk aluminum and shows the highest hardness among all Al–Al2O3 composites reported to date in the literature,which are the outcome of controlling multiscale strengthening mechanisms from tailoring solution atoms,dislocations,grain boundaries,precipitates,and externally introduced reinforcing particles.The present high-throughput strategy and method can be extended to design and architect advanced coatings or bulk materials in a highly efficient(synthesizing a nanostructured bulk with dimensions of 50×20×4 mm^(3) in 9 min)and highly flexible(regulating the gradient microstructures in bulk)way,which is conducive to industrial production and application.

Stress-rupture measurements of cast magnesium strengthened by in-situ production of ceramic particles

We have introduced a polymer precursor into molten magnesium and then in-situ pyrolyzed to produce castings of metal matrix composites(P-MMCs)containing silicon-carbonitride(SiCNO)ceramic particles.Stress-rupture measurements of as-cast P-MMCs was performed at 350 ℃(0.69TM)to 450 ℃(0.78TM)under dead load condition corresponding to tensile stress of 2.5 MPa to 20 MPa.The time-to-fracture data were analyzed using the classical Monkman–Grant equation.The time-to-fracture is thermally activated and follows a power-law stress exponent exhibiting dislocation creep.Fractography analysis revealed that while pure magnesium appears to fracture by dislocation slip,the P-MMCs fail from the nucleation and growth of voids at the grain boundaries.

Strengthened Monitoring of H5 Avian Influenza Viruses in External Environment in Hubei, 2018

The contamination status of H5 avian influenza viruses and distribution of subtypes of H5N1 and H5N6 in poultry-related environment of Hubei areas were investigated.Urban and rural live poultry markets,poultry farms,intensive livestock farms and other monitoring types of 103 counties in 17 cities were selected in Hubei.Wiping samples from cage surface,wiping samples from chopping board,fecal specimens and other environmental samples were collected and tested by real-time RT-PCR using primers and probes of influenza A,avian influenza of H5,N1 and N6 from December 2017 to March 2018.The avian influenza virus positive rate was compared among different monitoring sites,samples,time and regions.Totally,7132 environmental samples were collected in 1634 monitoring points with a positive rate of 2.24%.The positive rate of H5 avian influenza virus was the highest in urban and rural live poultry markets(3.44%,x^2=61.329,P<0.05)in 6 monitoring sites and wiping samples from chopping board(5.46%,x^2=67.072,P<0.05)in 6 sample types.H5N6 avian influenza viruses were detected more in eastern than western Hubei,and H5N6 avian influenza viruses were detected only in Xiangyang city of western Hubei.There were important high-risk places of human infection with H5 avian influenza virus in urban and rural live poultry markets and the poultry slaughtering plants.H5N6 has been the predominant subtype of H5 avian influenza viruses in the eastern and western Hubei and H5N6 avian influenza viruses were still present in a few areas of Hubei.Outbreaks of human H5N1 and H5N6 avian influenza remain at risk in Hubei province.

Influence of nano-scaled dispersed second phase on substructure of deformed dispersion strengthened copper alloy

The deformation behavior of dispersion strengthened copper alloy Cu-Al2O3 was studied by TEM. The results show that nano-scaled dispersed second phase not only increases dislocation density in matrix, but also has an important influence on the dislocation substructure. The presence of fine dispersed Al2 O3 particles results in a uniform and random dislocation distribution in matrix copper and causes the difficulty in formation of dislocation cell structure and the decrease in the amount of cell structure during deformation. Deformation gives rise to much more dislocations and dislocation cells form more difficultly and the decrease in the cell size with the increase of dispersion degree.

Recrystallization in Oxide Dispersion Strengthened Nickelbase Superalloy MA760

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Influence of Y_2O_3 Adding Method on Microstructure and Properties of Al_2O_3 Strengthened Y-TZP

The effects of Y2O3 adding methods （i.e.,co-precipitated and mixed） on the microstructure and properties of alumina-strengthened ytrria-stabilized tetragonal zirconia polycrystal （ASZ） were investigated. CYASZ and MYASZ were made by different adding method of Y2O3,co-precipitated and mixed,respectively. The results show that CYASZ is of uniform microstructure with fine grain size,however,MYASZ is of inhomogeneous microstructure due to the inhomogeneous distribution of ytrria. Comparing with CYASZ,the density and the strength of MYASZ are decreased,but the toughness is changed only a little. Under sliding wear test,the wear resistance of CYASZ is better than that of MYASZ.

The Researches on Performance and Technology of Strengthened Pure Platinum Wire

This paper discusses about the purity of strengthened pure platinum wire and the development method of platinum micro wire, in order to solve the difficulties of low tensile strength, easy to break, and low rate of micro wire. And it contrasts some performance of strengthened pure platinum wire and sponge Pt wire. The researches draw a conclusion that the thermoelectric properties of strengthened pure platinum micro wire was in accordance with national standards and satisfied users' requirements.

Fifteen-year mortality and prognostic factors in patients with dilated cardiomyopathy:persistent standardized application of drug therapy and strengthened management may bring about encouraging change in an aging society

BACKGROUND There is scarce data on the long-term mortality and associated prognostic factors in patients with dilated car-diomyopathy(DCM).The study aimed to investigate the all-cause mortality up to 15 years(mean 7.9±5.7 years)in such patients,and the independent prognostic factors influencing their long-term mortality.METHODS One hundred and sixty-six consecutive patients with DCM were prospectively enrolled from 2002 to 2003.The mean age of patients was 59.5±10.4 years,and approximately 57%were male.They were followed up by telephone or outpa-tient visit at least every three months until 2019 or all-cause death occurred.Predictors of mortality were identified using mul-tivariate logistic regression analysis.RESULTS During the 15 years of follow-up,five patients were lost to follow-up,and the complete data records of 161 patients were included in the analysis.Patients were treated with angiotensin-converting-enzyme inhibitors(ACEI)or angiotensin-recept-or blocker(ARB),β-blockers,mineralocorticoid receptor antagonist(MRA),diuretics and digitalis from 2002 to 2004,and main-tained at the maximum tolerated doses between 2004 and 2019.Our safety targets to maintain heart rate and blood pressure at 60-80 beats/min and 90-120/60-80 mmHg,respectively.All-cause mortality in the first five years was 55.9%.The independent risk factors for the 5-year mortality were age≥70 years old(OR=5.45,P=0.006),systolic blood pressure(SBP)>120 mmHg(OR=3.63,P=0.004),6-minute walk distance(6MWD)<450 m(OR=3.84,P=0.001).15-year all-cause mortality was 65.8%.The inde-pendent risk factors for 15-year mortality were age≥70 years old(OR=16.07,P=0.009),LVEF≤35%(OR=5.69,P=0.003),and SBP>120 mmHg(OR=9.56,P<0.001).CONCLUSIONS This study was the first to demonstrate the 15-year survival rate of 34%in DCM patients.The DCM patients’first five-year all-cause mortality decreased significantly after continuous standardized treatment and intensive management.The mortality then plateaued in the following 10 years.Age≥70 years,LVEF≤35%,and SBP>120 mmHg were independent predict-ors of 15-year all-cause mortality.

Small-angle neutron scattering study on the stability of oxide nanoparticles in long-term thermally aged 9Cr-oxide dispersion strengthened steel

A 9 Cr-oxide dispersion strengthened(ODS)steel was thermally aged at 873 K for up to 5000 h.The size distribution and chemical composition of the dispersed oxide nanoparticles were analyzed by small-angle neutron scattering under a magnetic field.Combined with transmission electron microscopy,Vickers micro-hardness tests and electron backscattered diffraction measurements,all the results showed that the thermal treatment had little or no effect on the size distributions and volume fractions of the oxide nanoparticles in the ferromagnetic matrix,which suggested excellent thermal stability of the 9 Cr-ODS steel.

Heat treatment/property relationships for solid-solution strengthened superalloys

Solid-solution strengthened superalloys are widely used because they possess excellent levels of high temperature strength and environmental resistance in combination with ease of fabrication.This latter factor is of utmost importance since it is a primary economic determinant.From a metal producer’s point of view,it determines the viable range of product forms that can be offered to the marketplace.From a user’s point of view,it determines the viable range of manufacturing processes that can be used to make the final product.For both the producer and user,an alloy’s heat treatment and property response is a central issue for defining fabricability.The areas of interest are typically quite fundamental and include such phenomena as recrystallization and grain growth,critical strain effects,relief of residual stresses,and cooling rate effects.In heat resisting alloys,these phenomena often involve subtle complexities due to the precipitation of carbides and,in some cases,the precipitation of intermetallic phases. This paper will deal with these complexities,providing relevant data and concrete examples wherever possible.The information presented should enable the proper selection of heat treatment practices for solid-solution strengthened superalloys.

Research on Purification of Domestic Sewage by Artificially Strengthened Ecological Filter Bed in North China

Artificially strengthened filter bed is an innovative wastewater treatment technology based on the coupling of eco-contact oxidation filters and artificial wetlands purification mechanism.By small scale laboratory equipment,the effects of cascade aeration,filter type,filter clogging and other ecological factors on the operation effect of artificial filter bed were studied.As indicated by the results,the pretreatment of cascade aeration had obvious effect and could satisfy the oxygen requirements of artificially strengthened ecological filter bed.Through the analysis on the purification results of volcanic and gravel filter,the effluent quality of volcanic filter was better than that of gravel filter.With the advantages of low operations costs and good effluent quality,the artificially strengthened ecological filter bed has great value to be popularized in North China.

Research progress on preparation technology of oxide dispersion strengthened steel for nuclear energy

Nuclear energy is a low-carbon,safe,efficient,and sustainable clean energy.The new generation of nuclear energy systems operate in harsher environments under higher working temperatures and irradiation doses,while traditional nuclear power materials cannot meet the requirements.The development of high-performance nuclear power materials is a key factor for promoting the development of nuclear energy.Oxide dispersion strengthened(ODS)steel contains a high number density of dispersed nano-oxides and defect sinks and exhibits excellent high temperature creep performance and irradiation swelling resistance.Therefore,ODS steel has been considered as one of the most promising candidate materials for fourth-generation nuclear fission reactor cladding tubes and nuclear fusion reactor blankets.The preparation process significantly influences microstructure of ODS steel.This paper reviews the development and perspective of several preparation processes of ODS steel,including the powder metallurgy process,improved powder metallurgy process,liquid metal forming process,hybrid process,and additive forging.This paper also summarizes and analyzes the relationship between microstructures and the preparation process.After comprehensive consideration,the powder metallurgy process is still the best preparation process for ODS steel.Combining the advantages and disadvantages of the above preparation processes,the trend applied additive forging for extreme manufacturing of large ODS steel components is discussed with the goal of providing a reference for the application and development of ODS steel in nuclear energy.

China's Science Gradually Strengthened

In order to ensure the steady development of our science, the Chinese government has continuously increased input in the last ten years. Information from the State Statistics Bureau shows that by the end of 1994, the national institutions and enterprises boasted 18.659 million technical experts, 4.3 times the number in 1978, or 1258 technical experts every ten thousand people, redoubling that of 1978. The whole country has 5860 independent scientific research and development (R & D) institutions,

Market presence in China Strengthened Network Growth and Dual-Chinese-Hub Strategy

In the end of 2007, Air China Limited (hereinafter "Air China") and Shanghai Airlines, formally joined Star Alliance at a ceremony held in the new Terminal Three at Beijing Capital International Airport. With the addition of the two Chinese airlines, Star Alliance now has 19 member carriers operating 17,000 daily flights to 897 destinations in 160 countries.……

IPR Protection Would be Strengthened during the Intertextile Shanghai Home Textiles

Asia’s top home textile trade fair, Intertextile Shanghai Home Textiles returns to the Shanghai New International Expo Centre on 25–27 August 2009. With more than 700 confirmed exhibitors, the show will feature home

Disbond detection with piezoelectric wafer active sensors in RC structures strengthened with FRP composite overlays

The capability of embedded piezoelectric wafer active sensors (PWAS) to perform in-situ nondestructive evaluation (NDE) for structural health monitoring (SHM) of reinforced concrete (RC) structures strengthened with fiber reinforced polymer (FRP) composite overlays is explored. First, the disbond detection method were developed on coupon specimens consisting of concrete blocks covered with an FRP composite layer. It was found that the prescnce of a disbond crack drastically changes the electromecbanical (E/M) impedance spectrum measured at the PWAS terminals. The spectral changes depend on the distance between the PWAS and the crack tip. Second, large scale experiments were conducted on a RC beam strengthened with carbon fiber reinforced polymer (CFRP) composite overlay. The beam was subject to an acccleratcd fatigue load regime in a three-point bending configuration up to a total of807,415 cycles. During these fatigue tests, the CFRP overlay experienced disbonding beginning at about 500,000 cycles. The PWAS were able to detect the disbonding before it could be reliably seen by visual inspection. Good correlation between the PWAS readings and the position and extent of disbond damage was observed. These preliminary results demonstrate the potential of PWAS technology for SHM of RC structures strengthened with FRP composite ovcrlays.