2007_IJHE_Mg2Ni+Ce,Al

NEMA NU 2-2007P ERFORMANCEM EASUREMENTS OF P OSITRON E MISSION T OMOGRAPHS--`,`,````,``,,,`,,,,``,,````,``-`-`,,`,,`,`,,`---NEMA Standards Publication NU 2-2007Performance Measurements of Positron Emission TomographsPublished by:National Electrical Manufacturers Association1300 N. 17th Street, Suite 1752Rosslyn, VA 22209© Copyright 2007 by the National Electrical Manufacturers Association. All rights including translation into other languages, reserved under the Universal Copyright Convention, the Berne Convention for the Protection of Literary and Artistic Works, and the International and Pan American Copyright Conventions.NU 2-2007Page iiNOTICE AND DISCLAIMERThe information in this publication was considered technically sound by the consensus of persons engaged in the development and approval of the document at the time it was developed.Consensus does not necessarily mean that there is unanimous agreement among every person participating in the development of this document.The National Electrical Manufacturers Association (NEMA) standards and guideline publications, of which the document contained herein is one, are developed through a voluntary consensus standards development process. This process brings together volunteers and/or seeks out the views of persons who have an interest in the topic covered by this publication. While NEMA administers the process and establishes rules to promote fairness in the development of consensus, it does not write the document and it does not independently test, evaluate, or verify the accuracy or completeness of any information or the soundness of any judgments contained in its standards and guideline publications.NEMA disclaims liability for any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, application, or reliance on this document. NEMA disclaims and makes no guaranty or warranty, express or implied, as to the accuracy or completeness of any information published herein, and disclaims and makes no warranty that the information in this document will fulfill any of your particular purposes or needs. NEMA does not undertake to guarantee the performance of any individual manufacturer or seller’s products or services by virtue of this standard or guide.In publishing and making this document available, NEMA is not undertaking to render professional or other services for or on behalf of any person or entity, nor is NEMA undertaking to perform any duty owed by any person or entity to someone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances.Information and other standards on the topic covered by this publication may be available from other sources, which the user may wish to consult for additional views or information not covered by this publication.NEMA has no power, nor does it undertake to police or enforce compliance with the contents of this document. NEMA does not certify, test, or inspect products, designs, or installations for safety or health purposes. Any certification or other statement of compliance with any health or safety–related information in this document shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement.NU 2-2007Page iCONTENTSForeword (iii)Section 1DEFINITIONS, SYMBOLS, AND REFERENCED PUBLICATIONS (1)1.1Definitions (1)1.2Standard Symbols (1)1.3REFERENCED PUBLICATIONS (3)Section 2GENERAL (4)2.1Purpose (4)2.2Purview (4)2.3Units of Measure (5)2.4Consistency (5)2.5Equivalency (6)Section 3SPATIAL RESOLUTION (7)3.1General (7)3.2Purpose (7)3.3Method (7)3.3.1Symbols (7)3.3.2Radionuclide (7)3.3.3Source Distribution (7)3.3.4Data Collection (8)3.3.5Data Processing (8)3.4Analysis (8)3.5Report (9)Section 4SCATTER FRACTION, COUNT LOSSES, AND RANDOMS MEASUREMENT (11)4.1General (11)4.2Purpose (11)4.3Method (11)4.3.1Symbols (12)4.3.2Radionuclide (12)4.3.3Source distribution (12)4.3.4Data collection (12)4.3.5Data processing (13)4.4Analysis (13)4.4.1Analysis with Randoms Estimate (14)4.4.2Alternative Analysis with No Randoms Estimate (16)4.5Report (17)4.5.1Count rate plot (17)4.5.2Peak count values (17)4.5.3System scatter fraction (18)Section 5SENSITIVITY (19)5.1General (19)5.2Purpose (19)5.3Method (19)5.3.1Symbols (19)5.3.2Radionuclide (19)5.3.3Source distribution (20)5.3.4Data Collection (20)5.4Calculations and Analysis (20)5.4.1System Sensitivity (20)5.4.2Axial Sensitivity Profile (20)5.5Report (21)NU 2-2007Page iiSection 6ACCURACY: CORRECTIONS FOR COUNT LOSSES AND RANDOMS (23)6.1General (23)6.2Purpose (23)6.3Method (23)6.3.1Symbols (23)6.3.2Radionuclide (23)6.3.3Source Distribution (23)6.3.4Data Collection (24)6.3.5Data Processing (24)6.4Analysis (24)6.5Report (25)Section 7IMAGE QUALITY, ACCURACY OF ATTENUATION, AND SCATTER CORRECTIONS (26)7.1General (26)7.2Purpose (26)7.3Method (26)7.3.1Symbols (26)7.3.2Radionuclide (26)7.3.3Source Distribution (27)7.3.4Data Collection (27)7.3.5Data Processing (28)7.4Analysis (28)7.4.1Image Quality (28)7.4.2Accuracy of Attenuation and Scatter Corrections (29)7.5Report (29)NU 2-2007Page iiiForewordReason for ChangesThe regulations regarding the maintenance of standards by NEMA requires that the standards be reviewed and, if necessary, updated every five years. This standards publication was developed by the Coincidence Imaging Task Force chartered by the Nuclear Standards and Regulatory Committee. Committee approval of the standard does not necessarily imply that all committee members voted for its approval or participated in its development. At the time it was approved, the task force was composed of the following members:Amy Perkins - Philips Medical Systems, Philadelphia, PACharles Stearns - GE Healthcare, Waukesha, WIJames Chapman - Siemens Medical Solutions, Hoffman Estates, ILJeffrey Kolthammer - Philips Medical Systems, Cleveland, OHJohn J. Williams - GE Healthcare, Waukesha, WIMichael Casey - Siemens Medical Solutions, Knoxville, TNIn the preparation of this Standards Publication, input of users and other interested parties has been sought and evaluated. Inquiries, comments, and proposed or recommended revisions should be submitted to the concerned NEMA product Section by contacting the:Vice President, Engineering DepartmentNational Electrical Manufacturers Association1300 North 17th Street, Suite 1752Virginia22209Rosslyn,The Major Changes to TestsThe dominant reason for changes is to improve the inclusion of cameras with intrinsically radioactive components. The philosophy of these changes is discussed inJournal of Nuclear Medicine, vol. 45, no. 5, 2004. Watson CC, Casey ME, Eriksson L, Mulnix T, Adams D and Bendriem B. “NEMA NU 2 Performance Tests for Scanners with IntrinsicRadioactivity.” pp. 822-826.The affected tests are:Section 4: Count Losses and Randoms. An alternate measurement method,applicable to devices with intrinsic radioactivity, has been introduced.Section 5: Sensitivity. Requirements relating to source strength and counting losseshave been refined, and the option to measure using randoms correction added.Additionally, Spatial Resolution (section 3) has been expanded to include the measurement and reporting of source position.Appendix A has been deleted.NU 2-2007Page ivScopeThe philosophy and rationale of the standards measurements, and illustrative examples of the analysis and results, are presented inJournal of Nuclear Medicine, vol. 43, no. 10, 2002. Daube-Witherspoon ME, Karp JS, Casey ME, DiFilippo FP, Hines H, Meuhllehner G, Simcic V, Stearns CW, Adam L-E, Kohlmyer S and Sossi V. “PET Performance Measurements Using the NEMA NU 2-2001 Standard.” pp. 1398-1409. The standards committee has attempted to specify methods that can be performed on all currently available positron emission tomographs. These include single and multiple slice, discrete and continuous detector, time-of-flight instruments, multi-planar and volume reconstruction models, and dedicated positron emission tomographs as well as other coincidence-capable imaging systems. Wherever possible, future developments that could be readily anticipated were taken into account. The committee has not specified methods that may be particularly appropriate for evaluating time-of-flight instruments, pending further evaluation of those instruments by the clinical and scientific communities.NU 2-2007Page 1Section 1DEFINITIONS, SYMBOLS, AND REFERENCED PUBLICATIONS1.1 DEFINITIONSaxial field-of-view (FOV): The maximum length parallel to the long axis of a positron emission tomograph along which the instrument generates transaxial tomographic images.prompt counts: Coincidence events acquired in the standard coincidence window of a positron emission tomograph. Prompt counts include true, scattered, and random coincidence events.sinogram: A two dimensional projection space representation of a transaxial image where one dimension refers to radial distance from the center, and the second dimension refers to projection angle.transverse field-of-view (FOV): The maximum diameter circular region perpendicular to the long axis of a positron emission tomograph within which objects might be imaged.test phantom: Components for each measurement are defined in the description of that measurement.1.2 STANDARDSYMBOLSSymbolic expressions for certain quantities are used throughout this standards publication. Symbols that use any one of the standard subscripts to further specify a basic quantity are identified by the subscript string xxx. All quantities expressed as a function of some independent variable shall be symbolically represented as Q(x), where x is a lower case letter representing the variable as defined in the related text.Only those symbols that are used in multiple sections of the standard are listed in this section. Symbols that are only used in one section are described in that section.counts(C xxx): The number of coincidence events:a. C ROI – events in a planar region of interestb. C TOT– total number of eventsc. C m– maximum number of eventsd. C r+s– random plus scatter event counte. C L– event count at left edge of projection area of interestf. C R– event count at right edge of projection area of interestg. C H– counts in a hot region of interesth. C B– counts in a background region of interesti. C C– counts in a cold region of interestradioactivity (A xxx): A nuclear decay rate in units of megaBecquerels, i.e., in units of 1 million disintegrations per second, and optionally expressed in units of milliCuries, i.e., in units of 37 million disintegrations per second:a. A0– initial radioactivity at T0b. A ave,j– average radioactivity for j th acquisitionc. A cal – radioactivity at time T calThe initial radioactivity at the beginning T0of an acquisition shall be found using the activity A cal as recorded in the dose calibrator or well counter at time T cal according to: --` , ` , ` ` ` ` , ` ` , , , ` , , , , ` ` , , ` ` ` ` , ` ` -` -` , , ` , , ` , ` , , ` ---NU 2-2007 Page 2⎟⎟⎠⎞⎜⎜⎝⎛−=2ln TT T exp A A 2/10cal cal 0Where: T 1/2 is the half-life of the radioisotope.The average radioactivity for a particular acquisition shall be found using the activity, A 0, at the beginning of the acquisition, the half-life of the radionuclide, T 1/2, and the duration of the acquisition, T acq , according to:⎪⎭⎪⎬⎫⎪⎩⎪⎨⎧⎟⎟⎠⎞⎜⎜⎝⎛−−⎟⎟⎠⎞⎜⎜⎝⎛=2ln T T exp 1T T 2ln A A 2/1acq acq2/10aveThe initial radioactivity A j shall be determined by the dose calibrator or well counter activity measure A cal , decay corrected to the starting time, T j of the j th acquisition, using the following equation:⎟⎟⎠⎞⎜⎜⎝⎛−=2ln TT T exp A A 2/1jcal cal jradioactivity concentration (a xxx ): A nuclear decay rate per unit volume in units of megaBecquerels per milliliter, i.e., in units of 1 million decays per second per milliliter, and optionally expressed in units of milliCuries per milliliter, i.e., in units of 37 million decays per second per milliliter:a. a t,peak – radioactivity concentration at peak true event rateb. a eff – effective average activity concentration of a line source in a solid cylinderc. a H – radioactivity concentration in a hot sphered. a B – radioactivity concentration in the backgrounde. a NEC,peak – radioactivity concentration at the peak NECR rateThe radioactivity concentration of a quantity of radioactivity distributed uniformly through a volume V shall be found by dividing the activity, A xxx , by the volume V within which the activity is uniformly distributed, according to:⎟⎟⎠⎞⎜⎜⎝⎛=V A a xxx xxxThe average radioactivity concentration is thus⎟⎟⎠⎞⎜⎜⎝⎛=V A a ave aveNote that in computing the effective radioactivity concentration, a eff , the volume to be used is the volume of the solid cylinder, not the volume of its line source insert.radioisotopic half-life (T 1/2): The interval of time during which half of the nuclei of a radionuclide are likely to decay. For the isotope 18F, the half-life is 6588 seconds (or 109.8 minutes or 1.830 hours).rate (R xxx ): A coincidence event rate measured in events per second, defined as the coincidence counts divided by the time interval T acq :a. R ROI – rate in a planar region of interestb. R TOT – total event ratec. R Extr – potential event rate (no losses)d. R t – true event rate--`,`,````,``,,,`,,,,``,,````,``-`-`,,`,,`,`,,`---NU 2-2007Page 3e. R s– scatter event ratef. R r– random event rateg. R t,peak– true event rate where R t saturatesh. R NEC– noise equivalent count ratei. R NEC,peak– peak noise equivalent count ratej. R CORR– decay-corrected count ratetime(T xxx): A time measured in seconds:a. T1/2– a time interval of one half-lifeb. T acq– duration of an acquisitionc. T j– starting time of acquisition jd. T cal– time of well counter measuremente. T T,E– the total time interval of transmission and emission acquisitionsvolume (V): A physical volume measured in milliliters.PUBLICATIONS1.3 REFERENCEDJournal of Nuclear Medicine, vol. 43, no. 10, 2002. Daube-Witherspoon ME, Karp JS, Casey ME, DiFilippo FP, Hines H, Meuhllehner G, Simcic V, Stearns CW, Adam L-E, Kohlmyer S and Sossi V. “PET Performance Measurements Using the NEMA NU 2-2001 Standard,” pp. 1398-1409.Journal of Nuclear Medicine, vol. 28, no. 11, 1987. Daube-Witherspoon ME and Muehllehner G. “Treatment of axial data in three-dimensional PET.” pp. 1717-1724.IEEE Transactions on Nuclear Science, vol. 37, no. 2, 1990. Strother SC, Casey ME and Hoffman EJ. “Measuring PET Scanner Sensitivity: Relating Countrates to Image Signal-to-Noise Ratios using Noise Equivalent Countrates.” pp. 783-788Journal of Nuclear Medicine, vol. 45, no. 5, 2004. Watson CC, Casey ME, Eriksson L, Mulnix T, Adams D and Bendriem B. “NEMA NU 2 Performance Tests for Scanners with Intrinsic Radioactivity.” pp. 822-826.NU 2-2007Page 4Section 2GENERAL2.1 PURPOSEThe intent of this standards publication is to specify procedures for evaluating performance of positron emission tomographs. The resulting standardized measurements can be cited by manufacturers to specify the guaranteed performance levels of their tomographs. As these measures become available throughout the industry, potential customers may compare the performance of tomographs from various manufacturers. The standard measurement procedures can be used by customers for acceptance-testing of tomographs before and after installation of the equipment.In defining this standard, language referring to levels of standard such as “Class Standard” versus “performance Standard” or “typical values” versus “meet or exceed” has been avoided. Determining the frequency of sampling of systems for each test is left to the manufacturer. Because both the difficulty of performing the various measurements and the accuracy of each test’s results vary, the decision of quoting a result as a typical or met/exceeded value is also left to the manufacturer. Thus for each result quoted, it should be specified that:• The measured value is assured to meet or exceed the specified value, or• The specification is typical of system performance.2.2 PURVIEWIt is assumed that every system to be tested under this standard is able to create sinograms and transverse slice images, define and manipulate two-dimensional regions of interest with circular and rectangular boundaries, and extract such parameters as coincidence event counts detected within specified intervals of time. The system is also assumed to have transverse fields of view suitable for human subjects. For all of the procedures, except for the Image Quality test, the scanner must have an accessible diameter of at least 260 millimeters. The test phantom for all of the procedures, except for the Image Quality test, is 70.0 cm in length and is suitable for performing measurements in all slices of tomographs with an axial field of view of less than 65 cm. The Image Quality test, which requires a different test phantom, can only be performed on a scanner with an accessible diameter of at least 350 millimeters. While this precludes the performance of the Image Quality test on some brain-only scanners, it is important to note that the Image Quality test is designed to emulate whole-body imaging performance, and therefore is not appropriate for a brain-only tomograph.The intent of this standard is to provide a set of measurements that permit the comparison of positron emission tomograph performance. Though it may be useful to have tests tailored to specific tasks or patient geometries, such additional tests do not add substantial value in the comparison of systems. The range of tests in this standard is not intended to restrict or discourage alternative tests.A specific example would be the NU 2-1994 Scatter Fraction and Count Rate test. The source geometry in this test is a better approximation to the human brain than the 70 cm source length in the current standard. However, for the purposes of general comparison, a system that performs better on the method in this standard will also be better on the geometry-specific test. A comprehensive comparison in different geometries is a valid topic for the research literature, but is not suitable for a test standard that may be applied to a production environment.The measurements described in this standards publication have been designed with a primary focus on whole body imaging for oncologic applications. As such, these measurements may not accurately represent the performance of a positron emission tomograph in brain imaging applications. These specifications represent a subset of measurements that define the performance of positron emission tomographs. Furthermore, the scope of this standard is limited to measurement of the performance of the positron emission tomograph component of multi-modality imaging systems.NU 2-2007Page 52.3 UNITS OF MEASURESystème International d’Unités (SI) units shall be used in all reports of positron emission tomograph performance measurements. Customary units such as milliCuries may be optionally reported as auxiliary values in parenthetical statements with the standard specifications for individual performance reports. 2.4 CONSISTENCYAll measurements must be performed without altering any of the instrument’s parameters that are mutually exclusive, unless otherwise directed for a particular measurement. These include, but are not limited to, the following parameters: energy discrimination windows (including the utilization of multiple energy windows in photopeak-Compton imaging modes), coincidence timing window(s), pulse integration time, reconstruction algorithm with associated parameters, pixel size, slice thickness, axial acceptance angle, and axial averaging or smoothing. If multiple operating modes are supported by the instrument, the operating mode used for each measurement shall be clearly specified.For instruments with movable detector elements the detector positions and trajectories shall be those recommended by the manufacturer and shall remain the same for all acquisitions. These motions include, but are not limited to, the detector separation distance, orbit trajectory around the patient to produce a full tomographic data set, and motions to increase sampling such as detector wobble or table displacements. The reconstruction algorithm, with its associated parameters, matrix, and pixel size shall be that recommended by the manufacturer and shall remain fixed for all of the NEMA measurements of tomograph performance unless otherwise directed for a particular measurement.Most systems organize the raw measurements into parallel projection matrices corresponding to transverse slices before performing a 2-D tomographic image reconstruction. This can lead to errors in positioning depending on the axial acceptance angle, particularly in the axial direction, as the radial distance from the center increases. Some systems can change the axial acceptance angle by adjusting the septa shielding, while others specify the angle in software. For systems that acquire and reconstruct 3-D measurements, it is assumed that the volume imaged can be oriented into transaxial slices for data analysis. The acceptance angle shall be that recommended by the manufacturer and shall remain fixed for all of the NEMA measurements of tomograph performance.Some measurements explicitly require volumetric data to be resorted into transverse sinograms using the single-slice rebinning method, as described in Daube-Witherspoon, M.E. and Muehllehner, G., “Treatment of axial data in three-dimensional PET,” Journal of Nuclear Medicine 28:1717-1724, 1987, for all other measurements, the manufacturer’s recommended treatment of volumetric data shall be used. The energy window or windows used for these measurements must be specified. If multiple windows are used in a photopeak-Compton imaging mode, that mode shall also be specified. These window settings shall be those recommended by the manufacturer and shall remain fixed during all of the NEMA measurements of a tomograph’s performance.Each measurement procedure specifies the method of source support, whether the source is to be suspended in the field of view or supported by some means. For those measurements in which the source is to be supported, the source shall be placed on the patient table.Unless specified otherwise in the description of a particular measurement, phantom positioning instructions carry a nominal tolerance of 5 mm in both the transaxial and the axial directions.NU 2-2007Page 62.5 EQUIVALENCY18F is specified for all of the tests. For some measurements, substitution of another radionuclide, such as 68Ga, can lead to significantly different results due to such factors as positron range and activity calibration. If, for quality assurance or other purposes, a manufacturer employs measurement methods other than those prescribed, the manufacturer shall demonstrate traceability between the methods prescribed for the measurement and those employed for testing.It is assumed that the dose calibrator or well counter used for these measurements has been calibrated using either a National Institute of Standards and Technology reference source, or one whose activity has been closely related or traceable to a reference source.NU 2-2007Page 7Section 3SPATIAL RESOLUTION3.1 GENERALThe spatial resolution of a system represents its ability to distinguish between two points after image reconstruction. The measurement is performed by imaging point sources in air, and then reconstructing images with no smoothing or apodization. Although this does not represent the condition of imaging a subject in which tissue scatter and a limited number of acquired events require the use of a smooth reconstruction filter, the measured spatial resolution provides a best-case comparison among scanners, indicating the highest achievable performance.3.2 PURPOSEThe purpose of this measurement is to characterize the widths of the reconstructed image point spread functions (PSF) of compact radioactive sources. The width of the spread function is measured by its full width at half-maximum amplitude (FWHM) and full width at tenth-maximum amplitude (FWTM).3.3 METHODFor all systems, the spatial resolution shall be measured in the transverse slice in two directions (e.g. radially and tangentially). In addition, an axial resolution also shall be measured.The transverse field-of-view and image matrix size determine the pixel size in the transverse slice. In order to measure the width of the point spread function as accurately as can practically be achieved, its FWHM should span at least three pixels. The pixel size should be made no more than one-third of the expected FWHM in all three dimensions during reconstruction and should be indicated as a condition for the spatial resolution measurement.3.3.1 SymbolsResolution (RES) — The measurement of the size of the reconstructed image of a point source. Resolution is specified as the full width at half maximum (FWHM) or full width at tenth maximum (FWTM) of the point source response.3.3.2 RadionuclideThe radionuclide for this measurement shall be 18F, with an activity less than that at which either the percent dead time losses exceed 5% or the random coincidence rate exceeds 5% of the total event rate.3.3.3 SourceDistributionThe point shall consist of a small quantity of concentrated activity inside a glass capillary with an inside diameter of 1 mm or less and an outside diameter of less than 2 mm. The axial extent of the activity in the capillary shall be less than 1 mm.The sources shall be fixed parallel to the long axis of the tomograph and located at 6 points as follows:• In the axial direction, along planes(1) at the center of the axial FOV and(2) one-fourth of the axial FOV from the center of the FOV.NU 2-2007Page 8• In the transverse direction the source shall be positioned(1) 1 cm vertically from the center (to represent the center of the FOV, but positioned toavoid any possible inconsistent results at the very center of the FOV),(2) at x=0 and y=10 cm, and(3) at x=10 cm and y=0.The source arrangement is shown diagrammatically in Figure 3-1.(2) at1/4FOV(1) atFOVcenterFigure 3-1POSITIONS OF SOURCE FOR RESOLUTION MEASUREMENT3.3.4 DataCollectionMeasurements shall be collected at all six positions specified above. At least one hundred thousand counts shall be acquired in each response function. Measurements can be taken with multiple sources. Finer sample size may be selected than typically used in clinical studies.3.3.5 Data ProcessingReconstruction by filtered backprojection with no smoothing or apodization shall be employed for all spatial resolution data.3.4 ANALYSISThe spatial resolution (FWHM and FWTM) of the point source response function in all three directions shall be determined by forming one-dimensional response functions, along profiles through the image volume in three orthogonal directions, through the peak of the distribution. The width of the response functions in the two directions at right angles to the direction of measurement shall be approximately two times the FWHM.。

Preparation and electrochemical characterization of Mg2Ni alloys with di erent crystallinitiesHiroshi Inoue,Shinya Hazui,Shinji Nohara and Chiaki Iwakura*Department of Applied Chemistry,College of Engineering,Osaka Prefecture University,Sakai,1-1Gakuen-cho,Osaka599-8531,Japan(Received24January1997;in revised form21July1997)AbstractÐMg2Ni alloys with di erent crystallinities were prepared by mechanical alloying(MA),followed by a subsequent heat treatment and their charge±discharge characteristics in(6M KOH+1M LiOH) aqueous solution were measured at30and708C.At both temperatures,charge±discharge characteristics of the Mg2Ni prepared by MA came close to those of the Mg2Ni alloy prepared by induction melting(IM), with an increase in heat-treating period at4008C.The presented approach was believed to be very e ective for the preparation of hydrogen storage alloys whose constituent metals have large di erences in melting points.#1998Elsevier Science Ltd.All rights reserved.Key words:nickel±metal hydride battery,hydrogen storage alloy,Mg2Ni,mechanical alloying,heat treat-ment.INTRODUCTIONAlthough Mg-based hydrogen storage alloys are very attractive materials for energy conversion,it has been thought that they are di cult to practi-cally utilize because their equilibrium hydrogen pressures are extremely low[1].Moreover,some skillful techniques are required for the preparation of the Mg-based alloys with a melting method since the di erence in melting point between Mg and Ni is about8008C.MA is an alloying method at at-mospheric temperature and pressure without melt-ing constituent metals where a great amount of alloy powders can be produced.The alloy compo-sition is simply controlled and metastable alloys which do not appear in phase-diagrams can be pro-duced by MA.Recently,the preparation of Mg-based alloys by MA has been tried to decrease their high operation temperature in a chemical hydrogen-absorption and desorption system[1±4]and several researchers have succeeded in the preparation of Mg-based alloys at a much lower temperature than 2508C.Concerning the operation in an electrochem-ical system,on the other hand,Lei et al.reported that amorphous Mg-based alloys prepared by MA showed a high discharge capacity[5].It was reported by some groups that the surface modi®-cation of Mg-based alloys with graphite or Ni by ball-milling by MA was very e ective for improving their charge±discharge characteristics[6,7].In con-trast,the discharge capacity of crystalline Mg2Ni alloy prepared by IM,which was negligibly small at 308C,increased by one order by raising the operat-ing temperature to708C[8].Moreover,the surface modi®cation of the crystalline Mg2Ni alloy by ball-milling improved,pronouncedly,the kinetics of hydrogen absorption and desorption at room temperature[7,9].In the present work,the combination of MA and the subsequent heat treatment is investigated with the intention of preparing,under a mild condition, Mg2Ni alloys which have electrochemical character-istics similar to those of crystalline Mg2Ni alloys prepared by IM.To our knowledge,such an approach has never been reported except for crys-talline LaNi5[10].EXPERIMENTALThe preparation of Mg2Ni alloy by MA was car-ried out by ball-milling a mixture(total mass of Electrochimica Acta,Vol.43,Nos.14±15,pp.2221±2224,1998#1998Elsevier Science Ltd.All rights reservedPrinted in Great Britain0013±4686/98$19.00+0.00PII:S0013-4686(97)10111-6*Author to whom correspondence should be addressed.E-mail:iwakura@chem.osakafu-u.ac.jp22211g)of Mg powder (less than 125m m)and Ni pow-der (less than 100mesh)in a stainless vessel at a rotating speed of 190rpm under Ar atmosphere for 7days.For comparison,an Mg 2Ni alloy prepared by IM was also used in this work.Its composition,determined by ICP,was 46.21wt%Mg,53.62wt%Ni,0.11wt%Al and 0.06wt%Si.Al and Si are contamination from a high frequency induction fur-nace.Experimental procedures,including the prep-aration of negative electrodes,and apparatus used were quite the same as those described in our pre-vious papers [6,8].In charge±discharge cycle tests,each negative electrode was charged for 24h at 50mA g À1and discharged to À0.6V vs Hg/HgO at the same current density.After every charging,the circuit was opened for 10min.The temperature was kept at 308C.Thermogravimetry (TG)and di erential thermal analysis (DTA)were carried out using a thermogra-vimetric and di erential thermal analyzer (Rigaku,CN807)in the temperature ranges between room temperature and 5008C under N 2atmosphere.Heat treatment of the Mg 2Ni alloy prepared by MA was carried out at 4008C for di erent periods in vacuo .The composition of the surface and cross section of the Mg 2Ni alloy powders prepared by MA was evaluated by electron probe microanalysis (EPMA)using a ®eld emission scanning electron microscope (Hitachi,S-4500)equipped with a microanalyzing system (Kevex Sigma).RESULTS AND DISCUSSIONThermal characteristics of Mg 2Ni alloy prepared byMA DTA and TG curves for the Mg 2Ni alloy pre-pared by MA are shown in Fig.1.An exothermic peak was observed at about 3608C on the DTA curve,while any change in mass was not observed on a TG curve.This is thought to be mainly at-tributable to the crystallization of the amorphous Mg 2Ni alloy prepared by MA,as suggested by Lei et al.[11].Judging from Fig.1,heating at a tem-perature over 3608C was found to be necessary for the preparation of the crystalline Mg 2Ni alloy and,therefore,in the present work,the heat treatment of the Mg 2Ni alloy prepared by MA was carried out at 4008C.E ect of heat treatment on crystallographic characteristics of Mg 2Ni alloy prepared by MA Figure 2shows X-ray di raction patterns for Mg 2Ni alloys heat-treated at 4008C for di erent periods,together with those for Mg 2Ni alloy pre-pared by IM.As can be seen from Fig.2(a),three broad peaks were observed at about 378,408andFig.1.DTA and TG curves of Mg 2Ni alloy prepared byMAFig.2.X-ray di raction patterns for Mg 2Ni alloys prepared by MA with the subsequent heat treatment at 4008C for 0h (a),2h (b),4h (c),24h (d)and IM (e)H.Inoue et al.2222458in the X-ray di raction pattern of the Mg 2Ni alloy prepared by MA without heat treatment.The di raction peaks are assigned to those of the Mg 2Ni alloy by comparison with the di raction pattern for the Mg 2Ni alloy prepared by IM,as shown in Fig.2(e),and the number and sharpness of the di raction peaks were quite di erent from those in Fig.2(a),suggesting the production of theamorphous Mg 2Ni alloy.It was con®rmed by EPMA that the surface and inside of the Mg 2Ni alloy powder prepared by MA had an Mg/Ni ratio of around 2uniformly,suggesting that alloying pro-ceeded over the whole of the Mg 2Ni alloy samples.The sharpness of the di raction peaks for the Mg 2Ni alloy prepared by MA increased with increasing heat-treating period.The X-raydi rac-Fig.3.Charge±discharge curves at 308C of Mg 2Ni nega-tive electrodes prepared by MA with the subsequent heat treatment at 4008C for 0h (a)and 24h (b)and IM(c).The 2nd charge and discharge curves in Fig.3(c)are superimposed on the 1stonesFig.4.Discharge capacities at 308C as a function of cycle number for Mg 2Ni alloys prepared by MA with the sub-sequent heat treatment at 4008C for 0h (w ),2h .(),4h (q ),24h (Q )and IM (r)Fig.5.Charge±discharge curves at 708C of Mg 2Ni nega-tive electrodes prepared by MA with the subsequent heat treatment at 4008C for 0h (a)and 24h (b)and IM (c).Q 1and Q 2show the quantity of electricity for the desorption of hydrogen absorbed in Mg 2Ni alloy and the oxidation of Ni,respectivelyFig.6.Discharge capacities at 708C as a function of cycle number for Mg 2Ni alloys prepared by MA with the sub-sequent heat treatment at 4008C for 0h (w ),2h (.),4h (q ),24h (Q )and IM (r )Mg 2Ni alloys;preparation and characterization 2223tion pattern of the long-term annealed Mg2Ni alloy approached that for the alloy prepared by IM,as can be seen from Fig.2,indicating that Mg2Ni alloys prepared by both methods have similar crys-tallinity.Judging from these results,the crystallinity of the Mg2Ni alloy can be controlled by changing the heat-treating period at the considered tempera-ture.E ect of heat treatment on charge±discharge characteristics at308C of Mg2Ni alloy prepared byMACharge±discharge curves at308C of Mg2Ni alloy prepared by MA with the subsequent heat treat-ment(4008C,0and24h)are shown in Fig.3, together with those of the Mg2Ni alloy prepared by IM.As can be seen from Fig.3,both charge and discharge capacities(1st cycle)for the Mg2Ni alloy prepared by IM were low,but the charge capacity of the Mg2Ni alloy prepared by MA greatly increased up to ca.500mA h gÀ1even at308C, leading to the increase in discharge capacity.The Mg2Ni alloy prepared by MA with a subsequent heat treatment at4008C for24h resembles one pre-pared by IM closely in charge±discharge behavior. Figure4shows discharge capacities at308C as a function of cycle number for the Mg2Ni alloys pre-pared by IM and MA with and without the sub-sequent heat treatment.The discharge capacities for the Mg2Ni alloy prepared by MA decreased with an increase in heat-treating period or an increase in crystallinity of the Mg2Ni alloy and approached those for the Mg2Ni alloy prepared by IM.The amorphous structure of the Mg2Ni alloy formed by MA seems to unstabilize hydrogen in it,causing the increase in discharge capacity at308C.E ect of heat treatment on charge±discharge characteristics at708C of Mg2Ni alloy prepared byMACharge±discharge curves at708C of the Mg2Ni alloy prepared by MA with the subsequent heat treatment(4008C,0and24h)are shown in Fig.5, together with those of the Mg2Ni alloy prepared by IM.In any case,the charge capacity at the2nd cycle was higher than that at the1st cycle in con-trast with the case at308C.On the other hand,the discharge capacity at the2nd cycle decreased except for the Mg2Ni prepared by IM.As can be seen from Fig.5,the discharge reac-tion proceeded in two steps which consisted of the oxidation of hydrogen absorbed in the alloy and the subsequent oxidation of Ni substrate and/or Ni powder.In analogy with our previous paper[8],the net discharge capacity for the Mg2Ni negative elec-trodes was obtained by subtracting the quantity of electricity consumed for the oxidation of Ni sub-strate and/or powder from the gross discharge ca-pacity of the Mg2Ni negative electrodes.Figure6shows the net discharge capacities as a function of cycle number for the Mg2Ni alloys pre-pared by IM and MA with and without the sub-sequent heat treatment.The discharge capacity for the Mg2Ni alloy prepared by IM had a maximum at the2nd cycle,as has been reported previously[8], while that for the other Mg2Ni alloys decreased monotonously with an increase in cycle number. However,the discharge capacities came close to those for the Mg2Ni alloy prepared by IM with an increase in heat-treating period,indicating clearly the increase in crystallinity of the alloy.The optim-ization of the conditions for the heat treatment must lead to the same charge±discharge character-istics as those of the Mg2Ni alloy prepared by IM. In this way,the Mg2Ni alloy similar to crystalline Mg2Ni prepared by IM in crystallographic and elec-trochemical characteristics could be prepared by MA and the subsequent heat treatment.Such an approach is believed to be successfully applied to other hydrogen storage alloys,which are very di -cult to prepare by IM because of the large di er-ence in melting point of the constituent metals.ACKNOWLEDGEMENTSThis work was partly supported by Grants-in-Aid for Scienti®c Research on Priority Areas of ``Electrochemistry of Ordered Interfaces''(No. 09237257)and Scienti®c Research(B)(No. 09555273)from the Ministry of Education,Science, Sports and Culture of Japan.The authors wish to express their thanks to The Kansai Research Foundation for Technology Promotion for®nancial support of this work and to Santoku Metal Industry Co.,for the preparation of the Mg2Ni alloy by induction melting.REFERENCES1.L.Zaluski,A.Zaluska and J.O.Stro m-Olsen,J.p.217,245(1995).2.E.Ivanov,J.Mater.Syn.Process.1,405(1993).3.S.Orimo,H.Fujii and T.Yoshino,J.Alloys Comp.217,287(1995).4.M.Terzieva,M.Khrussanova,P.Peshev and D.Radev,Int.J.Hydrogen Energy20,53(1995).5.Y.-Q.Lei,Y.-M.Wu,Q.-M.Yang,J.Wu and Q.-D.Wang,Z.Phys.Chem.183,379(1994).6.C.Iwakura,S.Nohara,H.Inoue and Y.Fukumoto,mun.,1996,1831.7.T.Kohno,S.Tsuruta and M.Kanda,J.Electrochim.Acta143,1198(1996).8.C.Iwakura,S.Hazui and H.Inoue,Electrochim.Acta41,471(1996).9.S.Nohara,H.Inoue,Y.Fukumoto and C.Iwakura,J.Alloys Comp.252,116(1997).10.H.Sakaguchi,T.Sugioka and G.-Y.Adachi,Chem.Lett.,1995,561.11.Q.-M.Yang,Y.-Q.Lei,C.-P.Chen,J.Wu and Q.-D.Wang,Z.Phys.Chem.183,141(1994).H.Inoue et al. 2224。

Pr替代La对La2Mg2Ni系A2B7型电极合金微观结构及循环稳定性的影响3张羊换1,2,赵栋梁1,任慧平2,郭世海1,祁　焱1,王新林1(1.钢铁研究总院功能材料研究所,北京100081;2.内蒙古科技大学材料与冶金学院,内蒙古包头014010)摘　要:　为了改善La2Mg2Ni系A2B7型电极合金的电化学循环稳定性,用Pr部分替代合金中的La,并用熔体快淬技术制备了La0.75-x Pr x Mg0.25Ni3.2Co0.2Al0.1 (x=0、0.1、0.2、0.3、0.4)电极合金。

用XRD、SEM、TEM分析了铸态及快淬态合金的微观结构,测试了铸态及快淬态合金的电化学循环稳定性,研究了Pr替代La对合金微观结构及循环稳定性的影响,探讨了合金电极在电化学循环过程中的失效机理。

结果表明,铸态及快淬态合金均具有多相结构,包括2个主相(La, Mg)Ni3及LaNi5和一个残余相LaNi2。

Pr替代La 使(La,Mg)Ni3明显增加而LaNi5减少。

电化学测试的结果表明,合金的循环稳定性随Pr替代量的增加而增加。

导致合金电极失效的主要原因是电极表面被电解液剧烈腐蚀以及合金电极在电化学循环过程中的粉化。

关键词:　A2B7型电极合金;Pr替代La;快淬;微观结构;循环稳定性中图分类号:　T G139.7文献标识码:A 文章编号:100129731(2010)03204882051　引　言自1990年小型Ni/M H电池问世以来,在短短的几年时间内,在激烈竞争的电池市场中占有了重要的地位。

然而,在最近几年,由于锂离子电池的迅猛发展,Ni/M H电池受到了巨大的冲击和挑战。

一方面是由于与Ni/M H电池相比,锂离子电池具有更高的质量(或体积)能量密度,另一方面,在现有技术条件下生产的Ni/M H电池在价格上又无法与铅酸电池抗衡,这就使Ni/M H电池的广泛应用受到了限制。

因此,研究一种低成本高性能的新型电极材料已迫在眉睫。

《超晶格A2B7型La-Ce-Y-Ni-Mn-Al储氢合金的设计与性能研究》篇一一、引言随着人们对能源危机和环境问题的认识不断加深，寻求可替代传统能源的清洁能源成为科学研究的重要方向。

其中，储氢合金作为一种能够储存大量氢气的重要材料，其研究和应用得到了广泛关注。

本篇论文旨在探讨一种新型的A2B7型超晶格La-Ce-Y-Ni-Mn-Al储氢合金的设计及其性能研究。

我们将详细讨论合金的设计理念、合成过程、性能特点及其在新能源技术中的应用。

二、合金设计超晶格A2B7型La-Ce-Y-Ni-Mn-Al储氢合金的设计基于对现有储氢材料性能的深入理解，以及通过元素替代和结构调整来优化其性能的策略。

我们选择了La、Ce、Y作为主要的稀土元素，这些元素在储氢过程中具有较高的活性。

同时，Ni、Mn、Al的加入能够提供良好的结构稳定性和电子特性。

我们设计的合金由两种主要元素组分构成，即A组分和B组分。

A组分主要由稀土元素La、Ce和Y组成，这些元素具有较大的储氢容量和良好的热力学性能。

B组分则主要由过渡金属元素Ni、Mn和Al组成，它们提供了良好的结构支撑和电子传导性。

这种设计既保证了储氢的容量，又提高了合金的稳定性。

三、合成过程合成超晶格A2B7型La-Ce-Y-Ni-Mn-Al储氢合金的过程主要包括原料准备、熔炼、淬火和退火等步骤。

首先，将选定的元素按照设计比例混合成原料，然后在高温下进行熔炼，使元素充分混合并形成均匀的液态合金。

接着进行淬火处理，使液态合金迅速冷却形成固溶体。

最后，通过退火处理来改善合金的微观结构和性能。

四、性能特点本论文主要研究的新型超晶格A2B7型La-Ce-Y-Ni-Mn-Al储氢合金在以下几个方面表现出了良好的性能：首先，本合金的储氢容量大。

由于其具有丰富的活性位点和优秀的晶格结构，能够吸附更多的氢气。

其次，该合金的稳定性好。

其组成元素之间的相互作用以及独特的超晶格结构使得合金在充放电过程中具有较好的稳定性。

《超晶格A2B7型La-Ce-Y-Ni-Mn-Al储氢合金的设计与性能研究》篇一一、引言随着能源需求的不断增长和环保意识的日益增强，新型储氢材料的研究与应用成为了当今科学研究的热点。

超晶格A2B7型储氢合金因其优异的储氢性能和良好的稳定性，在能源存储和转换领域具有巨大的应用潜力。

本文以La-Ce-Y-Ni-Mn-Al为研究对象，设计并研究其超晶格A2B7型储氢合金的性能，为新型储氢材料的研究与应用提供理论支持。

二、材料设计1. 合金成分设计La-Ce-Y-Ni-Mn-Al超晶格A2B7型储氢合金的成分设计主要基于各元素的物理化学性质及相互间的相互作用。

设计过程中，充分考虑了各元素的电子结构、原子半径、化学稳定性等因素，以达到最佳的储氢性能。

2. 合成与制备采用高温固相法合成La-Ce-Y-Ni-Mn-Al超晶格A2B7型储氢合金。

在合成过程中，严格控制反应温度、反应时间、原料配比等参数，以确保获得理想的合金结构和性能。

三、性能研究1. 结构分析通过X射线衍射（XRD）等手段对La-Ce-Y-Ni-Mn-Al超晶格A2B7型储氢合金的晶体结构进行分析，确定其晶体类型、晶格常数等参数。

结果表明，该合金具有典型的A2B7型超晶格结构，具有良好的晶体稳定性。

2. 储氢性能研究对La-Ce-Y-Ni-Mn-Al超晶格A2B7型储氢合金的储氢性能进行研究，包括储氢容量、吸放氢动力学性能等。

通过电化学测试、热力学分析等手段，研究合金的储氢机制及影响因素。

结果表明，该合金具有较高的储氢容量和良好的吸放氢动力学性能。

3. 循环稳定性研究对La-Ce-Y-Ni-Mn-Al超晶格A2B7型储氢合金的循环稳定性进行研究，通过多次充放电循环测试，观察其性能变化。

结果表明，该合金具有良好的循环稳定性，经过多次循环后仍能保持良好的储氢性能。

四、结果与讨论通过对La-Ce-Y-Ni-Mn-Al超晶格A2B7型储氢合金的设计与性能研究，发现该合金具有优异的储氢性能和良好的稳定性。

低高径比锆基非晶合金试样的室温压缩断裂行为赵威1,孟力凯2,武晓峰2(1.常州机电职业技术学院模具技术系,江苏常州213164;2.辽宁工学院材料与化学工程学院,辽宁锦州121001)摘　要:利用万能试验机及扫描电镜等研究了Zr 41.25Ti 13.75Ni 10Cu 12.5Be 22.5大块非晶合金的室温低高径比压缩变形和断裂行为。

结果表明:Zr 41Ti 14Cu 12.5Ni 10Be 22.5大块非晶合金低高径比试样压缩以弹性变形为主兼有少量塑性变形,表现出加工硬化行为,抗压强度达2031MPa ;试样断裂面与载荷轴线之间的夹角有0°,39°～43°和90°三种类型;其变形、断裂都是以剪切方式进行,呈现出劈裂、剪切和分层三种形式;此非晶合金低高径比试样压缩变形与断裂特征表现出的多样性缘于在该条件下存在着复杂应力场。

关键词:锆基大块非晶合金;低高径比;压缩;断裂中图分类号:TG 14 文献标识码:A 文章编号:100023738(2007)1220062204Compr ession Fr actur e B eha vior of Zr 2based Bulk Metallic G la ss with Low Ratioof H eight to Di a meter at Room Temperatur eZHA O Wei 1,M ENG L i 2ka i 2,W U Xiao 2feng 2(1.Changzhou Mec hanical and Elect rical Pet rochemical Vocational a nd Technology Coll ege ,Changzhou 213164,Chi na ;2.Liaoning Inst it ut e of Technology ,Jinzhou 121001,Chi na)Abst ract :The comp ression deformation and f racture be havior s of Zr 41.25Ti 13.75Ni 10Cu 12.5Be 22.5bulk metallicgla ss with low ratio of height to diameter ha ve been studied by means of Inst ro n Univeral 2Te sting Mac hine (IUTM )a nd scanning electron micro scopy (SEM )at room te mperat ure.The ela stic defor mation was do minated by pla stic defor ma tio n before f racture.Wor k har dening wa s found during the pla stic deformation and f racture st ress reached 2031M Pa.The macrocopic morphology of t he cylinder sample s with low ratio of height to diameter shows the formation of three kinds of f racture surf aces alo ng 0°,39°-43°and 90°a ngle with re spect to the loading direction ,respectively.The f racture surfaces we re formed by shear mode ,which included shear ,longitudinal a nd ho rizontal splitting.The diversit y of def ormation and f ract ure of t he sa mple s of the bulk metallic glass with low ratio of height to dia mete r under co mpre ssion condition reaulted f rom complex str ess fields.K ey w or ds :Zr 2base d bulk metallic gla ss ;low ratio of height to diameter ;comp ressive deformation ;f ract ure0　引　言准确地测量、表征非晶合金的变形行为及力学性能一直是非晶材料工作者追求的目标之一。

LDO DesignKe-Horng Chen NCTU ECE 2007 SpringLOW DROP-OUT REGULATORS‡Low-power-consumption LDO have been developed to increase the lifetime of battery effectively„„ „When the LDO is implemented in CMOS technologies, the low-ground-current feature is an advantage to portable applications These circuits operate under lower voltage condition High current efficiency become necessary to maximize the lifetime of the battery低功率混合晶片設計實驗室 LAB 8022Characteristic‡ Block Level Description –„ „ „ „ „ „ „Start-up circuit Reference Protection circuit Current sense element Error amplifier (EA) Pass element Feedback network低功率混合晶片設計實驗室 LAB 8023Vdrop −out = I Load RonSpecifications‡ ‡ ‡ ‡ ‡ ‡ ‡ ‡ ‡Line − regulation =ΔVo ΔVS ΔVo Ro − pass = ΔI L 1 + AβDrop-out voltage Line regulation Load regulation Tolerance over temperature Output voltage variation resulting from transient load-current step Output capacitor and ESR range Quiescent current flow Maximum load current Input/output voltage rangeLoad − regulation = TC =1 ∂Vo 1 ΔVTC ≈ Vo ∂Temp Vo ΔTemp Vo Vref[ΔVTC ,ref + ΔVTC ,Vos ] = ΔVtr = Vo ΔTempI load − max Δt + ΔVesr Co + Cb Vo (max) − Vo (min) VoAccuracysystem =Vo − min ≤ ΔVLNR + ΔVLDR + ΔVTC + ΔVtr + Vrefrence Vrefrence = Vref + ΔVTCref + ΔVLNRref ± Vos低功率混合晶片設計實驗室 LAB 802Vo Vref≤ Vo − max4System Design Considerations‡Enhance performance of LDO regulators for battery powered electronic„ „ „Low quiescent current flow for increase battery life Low voltage operation High output current Stability Maximum output current Regulating performance AC Analysis Transient Analysis低功率混合晶片設計實驗室 LAB 802 5‡The intrinsic issues in design :„ „ „‡Analysis„ „System Model under Loading ConditionsVinVref+ -gmagmpRo-passRoaCparR2 Vfb Vout Resr Co Cb RL ILAR1低功率混合晶片設計實驗室 LAB 8026Frequency ResponseR1 Vref ⎡ ⎣1 + sRoa C par ⎤ ⎦ [ R1 + R2 ] 1 + sResr Co 1 || Z = RX || sCo sCb =| Av |= × = s 2 RX R esr Co Cb + s [ RX + Resr ] Co + sRX Cb + 1 RX [1 + sResr Co ] V fb g ma Roa g mp Z„ „RX = Ro − pass ( R1 + R2 )„If Co Z≈Cb(Typical condition) RX [1 + sResr Co ] Resr )Cb ]„[1 + s( RX + Resr )Co ] ⋅ [1 + s( RXRo − passgma and gmp refer to the transconductance of the amplifier and the pass element respectively Roa is the output resistance of the amplifier Cpar refers to the parasitic capacitance introduced by the pass element Z is the impedance seen at VoutR1 + R2(Especially at high current)低功率混合晶片設計實驗室 LAB 802 7⇒ RX ≈ Ro − passFrequency Response (cont’d)1 P 1 ≈‡‡ ‡‡‡In a conventional LDO, ESR of output capacitor generates this zero to guarantee phase margin better than 45 degrees The ESR is not properly specified and varies with temperature The high-frequency bypass capacitors placed in parallel with the output capacitor form a pole further decrease the phase margin Ceramic capacitors are cheaper than tantalum capacitors, but ESR of ceramic capacitors typically less than 50mΩ ESR increases the overshoot drastically if large resistors are used低功率混合晶片設計實驗室 LAB 8022π Ro − pass Co 2π Resr Cb 2π Roa C par 2π Resr CoP2 P3P2 ≈ 1 P3 ≈ 1 Z1 ≈ 1P1 Z18Design Challenge‡The worst-case stability condition arises when the phase margin is at its lowest point (UGF goes high)„This happens when the load-current is at its peak value‡ ‡P1 increases at a faster rate than the gain of the system decrease The type and value of the output capacitor determine the location of P1, P2, and Z1P 1 =1 2π Ro − pass Co∝ λ Io ∝ Io 1 1 ∝ λ Io IoGain = g mp Ro − pass ∝ I o ×低功率混合晶片設計實驗室 LAB 8029Parasitic Pole Requirements‡‡The parasitic pole of the system can be identified as P3 and the internal poles of the error amplifier „ Requirement：parasitic pole must be greater than UGF „ Ensuring that P3 is at high frequencies is an especially difficult task to undertake in a low current environment The pole is defined by„ „The large parasitic capacitance (Cpar) resulting from a large pass device The output resistance of the amplifier (Roa)‡Low quiescent current and frequency design issues have conflicting requirements that necessitate compromises低功率混合晶片設計實驗室 LAB 80210低功率混合晶片設計實驗室LAB 80212Typical LDO Transient Response to a Load-current Step∆t 1∆t 3∆V t r _m a x ∆V 2∆t 2∆t 4∆V 3∆V 4V out I Load,minI Load,maxAdjust the threshold voltage by using a double gate MOS device‡The voltage at the floating gate (Vg), assuming that the source is grounded, is dictated byVg =‡V1C1 V2C2 + Ctotal Ctotal⎡ ⎣Ctotal is C1 + C2 + Cg ⎤ ⎦Vth1 is the effective threshold voltage of terminal one and Vth is the threshold voltage seen at the floating gateVthCtotal V2C2 − Vth1 = C1 C1‡If C1=C2=8Cg, V2=1.0V, and Vth=0.7V then„Yield a lower effective threshold voltage Vth1=0.49V‡Disadvantage: generate Vnbias and Vpbias低功率混合晶片設計實驗室 LAB 802Connect to the gate of the 21 pass devicesSlew-Rate Enhancement Circuits for CMOS Low-Dropout RegulatorsProposed Proposedanalog analogdriver driverusing usingSRE SREcircuit circuit‡Design problem„Large gate capacitance of power transistor degrades the loop-gain bandwidth and slew rate at the gate drive of the LDO A voltage buffer/driver can be inserted between the error amp. and the power transistor It is difficult to realize a good voltage buffer to meet the 低功率混合晶片設計實驗室 22 requirementsLAB 802‡Solution„ „Design considerations of proposed analog driver‡Proposed block diagram‡Rincon-Mora’s proposed„低功率混合晶片設計實驗室 LAB 802Need low threshold device and forward bulk-biasing23Current detection SRE circuitsSensing circuit Drive circuit‡Principle of operation„Static state‡‡ ‡„Transient state‡ ‡Md4 and Md5 both operation in saturation region, their drain currents equal to I1 and I2, and I2<I1 Md4 operates in the triode region such that node n1 pull up The drive transistor Mp is off Input positive voltage step, leading to I2 increase and node n1 pull down The drive transistor Mp is onn1低功率混合晶片設計實驗室 LAB 80224Simulation result‡The simulation results of ac responses of the core amplifier with and without the SRE circuit driving a load capacitance of 470pF„The SRE circuit does not affect the ac responses of the core amplifier低功率混合晶片設計實驗室 LAB 80225Experiment results‡It does not have significant transient overshoot even if the load capacitance is changed by more than two times„The SRE circuit is properly shut down before and end of the slewing periods„470-pF load„ 1-nF load低功率混合晶片設計實驗室 LAB 802 26Experiment results27.3%43X 44X低功率混合晶片設計實驗室 LAB 80227Experiment results‡The load transient response of the LDO is improved by 2.3 times with 50mA output-current change低功率混合晶片設計實驗室 LAB 80228Current Efficient Buffer‡The increase in current in the buffer stage aids the circuit„„By pushing the parasitic pole at its output (P3) to higher frequencies And by increasing the current available for slew-rate conditions‡Thus, the biasing conditions for the case of zero load-current can be designed to utilize a minimum amount of current„Which yields maximum current efficiency and prolonged battery life低功率混合晶片設計實驗室 LAB 802 29Frequency Response‡‡Low load current： λ I Load 1 P ≈ ≈ 1 2π Ro − pass Co 2π Co g mnpn I bias P3no −load −current ≈ = ≥ UGFmin 2π C par 2π Vt C par High load current：??Av ≈ Aamp g mp Ro − pass ∝ I Load I Load = 1 I Load低功率混合晶片設計實驗室 LAB 80230I Load=high I Load=Low低功率混合晶片設計實驗室LAB 802低功率混合晶片設計實驗室LAB 80237Current BoostingThe ability to shut off M po is not degraded since the forward bias voltage is a function of load-currentAt low load-currents I boost is low and V sb is close to zero At high load-current , I boost and V sb increase thereby decreasing the threshold voltage and increasing the effective gate drive of the output PMOS device39低功率混合晶片設計實驗室LAB 802低功率混合晶片設計實驗室LAB 80240Load RegulationThe load regulation performance is determined by the open-loop gain of the systemUnfortunately, the dc gain is limited by the frequency response of the regulatorThe UGF , in particular, is determined by The maximum allowable response timeThe frequency range where the parasitic poles of the system reside , such as the internal poles of the error amplifier 1o pass LDR o rego ol R V R I A β−−==+低功率混合晶片設計實驗室LAB 80241Pole/Zero Pair GenerationAdd a pole/zero pairFor a given unity gain frequency (UGF), the upper limit of the open-loop gain can be increased by manipulating the frequency response as depicted by trace BThe basic idea is for the gain to drop quickly as the frequency increases so that a larger dc gain is possibleRegulation is improved while keeping the UGF away from parasitic polesThe fact that P 2and Z 1track each other can be used to optimize the design-20db -40db-40db-20db-20dbA=Basic System B=Adjusted SystemBApole/zero pair17dBLoad regulation performance improved from approximatelyA 1A 2inputof the mirror45V satV satV satVec-satVg sVsd-sat2V beV beNPN DarlingtonNPNPNPNMOSPMOSout out out out out低功率混合晶片設計實驗室LAB 80248Pass Device (cont ’d)Use schottky diode|V SB | increase |V tp | decreaseCan use lower V in to drive M poProblem:During drop-out condition, M ps and M po are in different regions of operations. (V sd are different )低功率混合晶片設計實驗室LAB 802Small 0.5~1.0uAV be loop。