45 results about "Oxygen precipitation" patented technology

The invention belongs to the technical field of fuel cell non-noble metal catalyst material preparation, and particularly relates to a composite carbon nanofiber catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: firstly, combining metal ions with an organic ligand in an organic solvent at room temperature to successfully prepare a zeolite imidazate framework material (ZIFs); the preparation method comprises the following steps: carrying out primary carbonization on a prepared ZIFs material in an inert atmosphere high-temperature furnace to obtain a metal nitrogen carbon material, then uniformly mixing the metal nitrogen carbon material with a spinning solution, carrying out electrostatic spinning to obtain composite nanofibers, and then carrying out secondary carbonization in an inert atmosphere to finally successfully prepare the composite carbon nanofiber catalyst (MN-CNF). The catalyst has excellent electrocatalytic activity, can effectively improve the efficiency of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), and also has excellent catalytic stability.

Disclosed are a double-coated lithium-rich manganese-based positive electrode material, a preparation method and a use. According to the double-coated lithium-rich manganese-based positive electrode material, the surface of a lithium-rich manganese-based positive electrode material is firstly coated with metal oxide to form a first coating layer, the chemical stability of the oxide is relatively good, and a coated sample structure is not prone to being corroded and damaged; and then the first coating layer is coated with one or more of fluoride, oxide and phosphate to form a second coating layer, wherein the fluoride, oxide and phosphate can enter lattices of the lithium-rich manganese-based positive electrode material and occupy oxygen vacancies to inhibit oxygen precipitation.

The invention relates to a method for controlling BMD of a heavily boron-doped substrate and a lightly boron-doped epitaxial wafer through RTP, which belongs to the technical field of silicon wafer processing, and comprises the following operation steps of: 1, drawing a single crystal by adopting a Czochralski method, and doping Bo metal during crystal drawing; and 2, slicing, grinding and thinning, polishing, cleaning and epitaxy processes are carried out. Step 3, dividing the silicon wafers after completion into three groups A, B and C for annealing treatment; and meanwhile, a group of reference silicon wafers without RTP annealing treatment are manufactured. And 4, carrying out low-temperature heat treatment, wherein the low-temperature treatment is used for promoting nucleation of oxygen precipitation. And 5, performing high-temperature heat treatment which is used for promoting the growth of an oxygen precipitation nucleation center in the silicon wafer body so as to form high-density oxygen precipitation and induced defects thereof in the silicon wafer body. The method improves the yield of silicon wafers, greatly shortens the time consumed in the annealing process in the manufacturing of an integrated circuit, meets the actual requirement for low temperature in the manufacturing process of the integrated circuit, reduces the technological process, and saves the cost.

The invention relates to a silicon wafer defect detection method. The method comprises the following steps: providing a silicon wafer sample with oxygen concentration lower than 9ppma; carrying out first heat treatment on the silicon wafer sample under a first preset condition so as to generate oxygen evolution nucleation in a P-band region, a B-band region and / or an IDP region; performing secondary heat treatment on the silicon wafer sample under a second preset condition to generate oxygen evolution nucleation in a VDP region; performing third-time heat treatment on the silicon wafer sample under a third preset condition, so that oxygen evolution nuclei generated in the first-time heat treatment and the second-time heat treatment grow; and carrying out minority carrier lifetime test on the silicon wafer sample. Through a three-section heat treatment method, the oxygen precipitation amount of a part of crystal characteristic areas is increased, so that crystal characteristic area boundary distinguishing can be clearly carried out on a silicon wafer with the oxygen concentration below 9ppma.

The invention discloses a CZ method semiconductor monocrystalline silicon crystal pulling growth stripe detection method comprising the following steps: before growth stripe detection, determining the interstitial oxygen content and defect type of a monocrystalline silicon sample, carrying out heat treatment on the sample according to the interstitial oxygen content and defect type to generate oxygen precipitate in a silicon wafer, and then etching the sample wafer to enable the oxygen precipitation corrosion pits to appear to form crystal pulling growth stripes. The method is characterized in that different heat treatment methods are adopted for different defect types and different interstitial oxygen contents to form oxygen precipitates, so that crystal pulling growth stripes can be clearly detected.

The invention discloses a process for improving oxygen ring defects, and relates to the field of Czochralski single crystal manufacturing, the process comprises the following steps: S1, preparing a single crystal furnace: the single crystal furnace comprises a carbon felt, a quartz crucible, a graphite support, a solution, a heater, a heat shield, a crystal bar, a furnace body shell and an argon pipe; s2, crystal pulling treatment; s3, setting different liquid opening distances to produce crystal bars for small-batch battery verification, and monitoring the OSF generation condition after battery topcon high-temperature diffusion heat treatment; and S4, carrying out an oxygen precipitation heat treatment process and a Cu diffusion process on the material for impurity removal. According to the technology for improving the oxygen ring defect, the position of a heat shield is adjusted, monocrystalline silicon oxidation induced staggered rings are reduced, on the basis of the forming principle of the defect, the V / G value of a solid-liquid interface is controlled to be larger than the critical value of 0.13 mm < 2 > min <-1 > k <-1 > in the production process, and reduction of thermal stress is controlled; higher vacancy concentration can be obtained, dislocation can be reduced, and OSF-ring generation can be avoided.

The present invention provides a positive electrode material and a preparation method therefor, and a lithium ion battery. The positive electrode material comprises an inner core, an oxygen absorption layer, and a passivation layer from inside to outside; the inner core comprises an oxide composed of Ni, Li, a metallic element M, and a non-metallic element Q; the metallic element M comprises at least one of Mg, Al, Zr, Ca, Ti, Sr, Y, Nb, Mo, W, Ta, or Ce; the non-metallic element Q comprises at least one of F, B, P, or Si; the oxygen absorption layer is an unsaturated oxide comprising a cladding element L; the cladding element L comprises at least one of V, Ga, In, Sn, Bi, Ce, Pr, or Sb; the passivation layer is a compound comprising an element F. According to the present invention, by means of functional design of different layered structures for the positive electrode material, the effect of suppressing oxygen precipitation can be achieved.

The invention relates to the technical field of semiconductor processing, in particular to an oxidation induced fault suppression system for a monocrystalline silicon rapid heat treatment process, comprising: an RTP reaction chamber having an outer reaction chamber and a quartz reaction chamber arranged therein; the heating unit is provided with an upper heating unit and a lower heating unit which are respectively positioned at the top and the bottom of the quartz reaction cavity; the gas path structure is provided with an upper-layer process gas pipeline and a lower-layer process gas pipeline which are connected to the interior of the quartz reaction cavity, high-purity argon is introduced into the upper layer, nitrogen-hydrogen mixed gas is injected into the lower layer, and oxygen readsorption is inhibited through gas layering; the in-situ monitoring module is arranged on the lower side of the quartz reaction cavity and is used for monitoring the crystal temperature gradient and the oxygen precipitation density.

The invention belongs to the technical field of semiconductor material processing, and particularly relates to a monocrystalline silicon preparation method for improving forward voltage drop of a power device, the power device and monocrystalline silicon, and the method comprises the following steps: when a monocrystalline silicon rod is drawn by a czochralski method, the growth crystal orientation is 1t by controlling crystal pulling parameters and cooling parameters in an equal-diameter process; 111gt, 111gt; the silicon single crystal rod, the crystal pulling parameters and the cooling parameters are configured as follows: interstitial oxygen precipitation can be inhibited to form silicon dioxide precipitation, so that the volume microdefect density in the grown silicon single crystal is lower than a preset threshold value, and the method provided by the invention inhibits the interstitial oxygen precipitation process by reasonably configuring the crystal pulling parameters and the cooling parameters, so that the yield of the silicon single crystal is improved. According to the present invention, the silicon dioxide deposition formation is reduced, such that the volume micro-defect density in the grown monocrystalline silicon is lower than the preset threshold value, and when the monocrystalline silicon is applied to the ultra-fast recovery diode product, the forward voltage drop value VF can be reduced so as to be within the range of 1.3-1.7 V so as to meet the customer requirements.

The invention relates to the technical field of new energy, in particular to a metal-water battery system capable of storing energy and asynchronously producing hydrogen and oxygen, the metal-water battery system comprises a bifunctional catalyst, an iron deposition / dissolution electrode and an acidic electrolyte, and the metal-water battery system is prepared by the following specific steps: S1, stainless steel such as 304 or 316 is subjected to molten salt electrolysis modification to prepare the bifunctional catalyst, and the bifunctional catalyst has OER and HER catalytic activity; s2, taking the modified stainless steel catalyst as a first anode, taking inert electrodes such as a copper sheet or a titanium sheet as a first cathode, and forming a first electrolysis system with an acidic ferrous sulfate solution; and S3, electrolysis is conducted through the first electrolysis system, oxygen evolution reaction is conducted on the first anode, and metal iron is deposited on the first cathode. According to the metal-water battery system considering energy storage and asynchronous production of hydrogen and oxygen, time-space separation of deposition / dissolution of iron and hydrogen-oxygen precipitation is regulated and controlled through the bifunctional catalyst, and safe energy storage and step-by-step production of hydrogen energy / oxygen are achieved; the method is suitable for renewable energy storage, hydrogen energy preparation and distributed energy supply scenes.

The present invention discloses a perovskite oxide with excess A position and a preparation method and application thereof, belonging to the field of electrocatalysis technology. The molecular formula of the perovskite oxide with excess A position in the present invention is: Sm x SrCo 0.95‑m‑n Fe m Ni n O 3‑δ ; Where, 0≤x≤0.2, 0≤m≤0.95, 0≤n≤0.95, 0

The present invention relates to a preparation method and application of a hydrogen elimination and oxygen evolution electrode, and belongs to the technical field of water electrolysis. The present invention constructs a hydrogen elimination function by plating gold and platinum on the surface of a titanium mesh. The gold layer is first plated on the surface of the Ti mesh, which is beneficial to improving the high-potential oxidation resistance of the Ti mesh. At the same time, the gold plating can further improve the conductivity of the electrode and reduce the interface impedance. The platinum particles dispersed on the surface of the Au layer mainly eliminate hydrogen. Then, iridium oxide is deposited on the surface of gold and platinum, which helps to enhance the IrO x conductivity and improve the oxygen evolution activity of the catalyst.

The present application relates to oxygen precipitation and oxygen reduction electrocatalyst technical field, especially an accordion type carbon supported single atom-cluster catalyst and preparation method and application. The present application first synthesizes a kind of accordion type coordination polymer containing zinc and iron series metal (such as iron, cobalt, nickel), then it is etched using potassium ferricyanide or potassium cobalticyanide;Finally, pyrolysis is carried out under nitrogen atmosphere, forming an accordion type carbon supported single atom-cluster catalyst. The new catalyst has a unique accordion type layered structure, higher specific surface area, more active sites, and the main skeleton nitrogen-doped carbon of the catalyst has good conductivity, which can accelerate the mass transfer and charge transfer process of electrocatalytic reaction. The present application belongs to a new type of bifunctional catalyst, which can catalyze oxygen reduction reaction and drive oxygen precipitation reaction, meet the needs of rechargeable zinc-air battery, and show potential application prospect to replace commercialized noble metal catalyst.

The invention provides an amorphous substance coated positive electrode active material as well as a preparation method and application thereof. In the invention, the amorphous substance is selected from one or more of transition metal silicide, boride, phosphide, sulfide, selenide, carbide, amorphous carbon or amorphous silicon materials. The amorphous substance coating in the invention can form a compact self-healing passivation layer at the interface of the positive electrode material, not only can inhibit oxygen precipitation under high voltage in dynamics, but also can be combined with Li alkali metal to become a mixed conductor of ions and electrons, so that the conduction performance of the electrons and lithium ions is improved, and the interface impedance is reduced. Meanwhile, the surface of the positive electrode material can be uniformly coated by a special coating mode of the amorphous substance, so that side reaction between the positive electrode material and electrolyte is effectively inhibited, a solid electrolyte membrane on the surface of the positive electrode material is stabilized, formation of microcracks in the material is reduced, and the cycling stability is improved.

Methods for detecting oxygen precipitation induced defects during a polishing sequence. The methods are suited for detecting oxygen precipitates in heavily doped boron single crystal silicon wafers or in lightly doped wafers that are COP-free. The methods may involve inspecting a silicon wafer for LLS defects after a thermal anneal followed by a polishing sequence.

The application discloses a chain type pretreatment and efficiency improving equipment for TOPCon cell raw material silicon wafers. The equipment has a heating cavity with a silicon wafer conveying roller, and a temperature sensor and gas inlet and outlet pipelines are arranged in the heating cavity; heating, gas circulation and alarm functions of a central computer control device are provided. The core of the equipment is that the high temperature set in the furnace cavity can be reached, and the stability and uniformity of the temperature in the cavity are ensured; through the high temperature above 1100 DEG C and the oxygen atmosphere, the oxygen precipitation and vacancy defects in the photovoltaic N-type silicon are ablated and repaired, the recombination center in the material body is reduced, the bulk lifetime of the silicon is increased, and thus the cell efficiency is improved; the time required for pretreatment is greatly shortened, and the equipment is favorable for large-scale industrial application.

Methods for detecting oxygen precipitation induced defects during a polishing sequence. The methods are suited for detecting oxygen precipitates in heavily doped boron single crystal silicon wafers or in lightly doped wafers that are COP-free. The methods may involve inspecting a silicon wafer for LLS defects after a thermal anneal followed by a polishing sequence.

Nitrogen-doped CZ silicon crystal ingots and wafers sliced therefrom are disclosed that provide for post epitaxial thermally treated wafers having oxygen precipitate density and size that are substantially uniformly distributed radially and exhibit the lack of a significant edge effect. Methods for producing such CZ silicon crystal ingots are also provided by controlling the pull rate from molten silicon, the temperature gradient and the nitrogen concentration. Methods for simulating the radial bulk micro defect size distribution, radial bulk micro defect density distribution and oxygen precipitation density distribution of post epitaxial thermally treated wafers sliced from nitrogen-doped CZ silicon crystals are also provided.

The invention provides a heating device, a single crystal furnace, a method for improving oxygen precipitation in monocrystalline silicon and monocrystalline silicon. The heating device comprises a plurality of heating pieces arranged around the monocrystalline silicon at intervals, the tops of the heating pieces are connected through a first connecting part, and the bottoms of the heating pieces are connected through a second connecting part; the first connecting part and the second connecting part are both of an annular structure; the heating sheet comprises a first sub-heating part, a second sub-heating part and a third sub-heating part which are sequentially connected from top to bottom, the first sub-heating part is connected with the first connecting part, the third sub-heating part is connected with the second connecting part, and the condition that S1 < 1gt > is met; s2gt; and S3. The heating device is used for heating the monocrystalline silicon in the growth process of the monocrystalline silicon rod, the thermal history of the monocrystalline silicon can be improved, so that primary oxygen precipitation in the monocrystalline silicon is reduced, meanwhile, the monocrystalline silicon can be uniformly heated in the single crystal furnace by controlling the heat transfer area of the heating piece from top to bottom to be gradually reduced, and the quality of the monocrystalline silicon is improved. And the radial uniformity of oxygen precipitation is improved.

The present invention provides a positive electrode precursor material and a preparation method and application thereof. The positive electrode precursor material includes a nickel hydroxide core, a manganese hydroxide layer and a cobalt hydroxide layer from the inside to the outside. In the positive electrode precursor material provided by the present invention, the three elements of nickel, cobalt and manganese are distributed in regions. In the subsequent sintering process for preparing the positive electrode material, the elements diffuse with each other, and a special structure is formed during the diffusion process, which can reduce the structural fragmentation and oxygen precipitation of the material under high voltage, and finally improve the performance of the positive electrode material under high voltage.

The present invention relates to a method for measuring the size of oxygen precipitates in a silicon wafer. The method comprises obtaining the LSE size of defects on the surface of the silicon wafer, dividing the defects into a first defect group and a second defect group based on the LSE size, and calculating the size of the oxygen precipitates in the silicon wafer according to the LSE size. The method for measuring oxygen precipitates of the present invention can quickly and accurately obtain the actual size of the oxygen precipitates on a silicon wafer to be tested containing a large amount of oxygen precipitates, thereby saving time and reducing costs.

The invention relates to the technical field of semiconductor materials, in particular to a heavily-doped silicon single crystal oxygen precipitation detection method which comprises the following steps: S1, pickling a complete silicon wafer; s2, spraying the atomized transition metal salt solution on the surface of the silicon wafer; s3, placing the silicon wafer in a nitrogen atmosphere of 750-900 DEG C, and keeping the temperature constant for 30-60 minutes; s4, cooling the silicon wafer to room temperature at a cooling rate of 10-20 DEG C / s; s5, removing an interference layer on the surface of the silicon wafer; s6, observing the metal decoration pattern on the surface of the silicon wafer to judge the oxygen precipitation concentration; thus, through cooperative control of the temperature and the cooling rate, the metal ions are selectively deposited only at the oxygen precipitation and the induced defects of the oxygen precipitation, so that the concentration of the oxygen precipitation is accurately and reliably revealed; meanwhile, the oxygen precipitation concentration is measured by performing metal decoration on the surface of the complete silicon wafer, so that the influence of artificial damage caused by cutting the sample on the detection result can be avoided, and the accuracy of the oxygen precipitation concentration detection result is remarkably improved.

The invention discloses a device and method for producing hydrogen through wastewater treatment, and belongs to the technical field of wastewater treatment. The device comprises a wastewater pretreatment mechanism, the wastewater pretreatment mechanism comprises a mounting bottom plate, a precipitation bin is fixedly connected to the top of the mounting bottom plate, and a water inlet pipe is arranged on one side of the upper end of the precipitation bin. The invention aims to solve the problems that in the electrolysis process in the prior art, bubbles are attached to the surface of an electrode plate to form a gas film, so that the mass transfer resistance is remarkably increased, and the electrolysis efficiency is reduced, and achieves the technical effects that the two sides of the bipolar electrode are respectively subjected to hydrogen-oxygen precipitation reaction; by combining the bubble guiding micro groove and the auxiliary defoaming design of the vibration motor, the bubble separation speed is remarkably increased, the electrolysis voltage is lower, the hydrogen production energy consumption is reduced, hydrogen and oxygen are collected through the independent cavity and the flow channel respectively, the guiding effect of the micro groove is matched, the gas cross contamination rate is lower, the hydrogen purity is higher, and the device is more convenient to use.

The application relates to the technical field of semiconductor material manufacturing, and discloses an N-type monocrystalline silicon wafer diffusion impurity absorption optimization method, which comprises the following steps: removing surface contaminants and tiny defects by pretreating an N-type monocrystalline silicon wafer; forming an impurity absorption layer on at least one surface of the pretreated N-type monocrystalline silicon wafer; performing diffusion annealing treatment on the N-type monocrystalline silicon wafer with the formed impurity absorption layer, and removing the impurity absorption layer material on the N-type monocrystalline silicon wafer after the diffusion annealing treatment; and completing the N-type monocrystalline silicon wafer diffusion impurity absorption optimization work. The impurity absorption layer formed on the surface of the silicon wafer can effectively capture and fix heavy metal impurities and defects, such as oxygen precipitation and metal precipitation, which may be generated in the subsequent process of the silicon wafer, so as to prevent the impurities and defects from causing adverse effects on the performance of the silicon wafer. The diffusion annealing treatment further promotes the diffusion of the impurities and the impurity absorption capacity of the impurity absorption layer, and ensures the effective removal of the impurities.

The invention discloses a noble metal or an oxide-Co3O4 heterojunction nanoflower thereof as well as a preparation method and application thereof, and belongs to the field of electrocatalysis. The preparation method of the heterojunction nanoflower comprises the following steps: (1) dissolving cobalt salt, precious metal salt and cobalt salt ligand tetracyanoethylene in a solvent to obtain a mixed solution; (2) carrying out solvent heat treatment on the mixed solution, washing and drying to obtain a cobalt ion / noble metal ion-containing nano flower-shaped complex; and (3) carrying out pyrolysis oxidation treatment on the cobalt ion / noble metal ion-containing nano flower-shaped complex. The heterojunction nanoflower is used as an electrocatalyst, and by virtue of a three-dimensional porous flower-shaped structure, a large specific surface area and abundant heterojunction interface active sites, the activity and stability of oxygen evolution reaction (OER) are remarkably improved, so that the efficiency of hydrogen production by electrolysis of water is improved, and a technical guarantee is provided for commercial application of the heterojunction nanoflower; and the preparation method with low cost and high efficiency has strong economic competitiveness and wide market application prospect.

The present application discloses a silicon wafer and a processing method thereof. The silicon wafer processing method comprises: polishing the silicon wafer to be processed; performing a first annealing treatment on the silicon wafer after the polishing treatment; performing a second annealing treatment on the silicon wafer after the first annealing treatment; wherein the first annealing treatment has a first annealing temperature T1 and a first annealing time t1, and the second annealing treatment has a second annealing temperature T2 and a second annealing time t2, satisfying: T1 ≥ T2, t2 ≥ t1. The present application eliminates the native oxygen precipitation of the silicon wafer by performing two annealing treatments after polishing the silicon wafer, and satisfies: T1 ≥ T2, t2 ≥ t1, thereby ensuring the uniformity of the radial nucleation and growth of oxygen precipitation during the annealing process, reducing the thermal stress effect on the contact position between the silicon wafer and the silicon carbide (SiC) boat teeth during the second annealing treatment, thereby avoiding the generation of slip lines at the contact position.

The application discloses doped tricobalt tetraoxide and a preparation method and application thereof. The doped tricobalt tetraoxide is doped with anions or simultaneously doped with metal cations and anions. The doped tricobalt tetraoxide is prepared by introducing anions and doping, and when metal cations are further introduced, the metal cations and the doped anions play a synergistic doping effect. The anions and the metal cations are uniformly doped in lithium cobaltate prepared by taking the doped tricobalt tetraoxide as a precursor, the structure stability of the lithium cobaltate in a charging and discharging process is improved on the basis of effectively reducing oxygen precipitation of the lithium cobaltate, the cycle stability of the lithium cobaltate at high voltage is effectively improved, and the preparation method of the doped tricobalt tetraoxide can ensure that the structure and electrochemical performance of the prepared doped tricobalt tetraoxide are stable and the efficiency is high.

The invention belongs to the technical field of all-vanadium liquid flow battery electrodes, and discloses a hollow core-shell nanosphere composite graphite felt for vanadium batteries and a preparation method thereof, comprising the following steps: graphite felt pretreatment; silica sol preparation; titanium dioxide@silicon dioxide sol preparation; metal oxide@titanium dioxide@silicon dioxide core-shell nanosphere preparation; composite graphite felt electrode preparation; and hollow core-shell nanospheres are synthesized layer by layer through self-assembly by a sol-gel method, the structure is stable, the effective active area is increased, and by compounding a plurality of oxygen evolution inhibitors, the amount of oxygen released in the positive electrode electrolyte is effectively reduced compared with a single inhibitor, the oxygen evolution side reaction is inhibited, the utilization rate of the electrolyte is improved, and the energy loss caused by the side reaction during battery operation is reduced.

The application discloses a fast-charging layered lithium-rich positive electrode material and a preparation method and application thereof, and is characterized in that the preparation method of the fast-charging layered lithium-rich positive electrode material is a specific Ti element doping modification Li2RuO3 preparation method, Ti-O strong bonds are used to play a role in stabilizing a lattice structure and inhibiting oxygen precipitation, and more importantly, through accurate control of a doping process, optimization and activation of a lithium ion two-dimensional diffusion channel are realized, a lithium ion migration energy barrier is significantly reduced, and thus a kinetic obstacle of fast charging is essentially solved. The prepared material shows a charge capacity retention rate far higher than that of a conventional modified Li2RuO3 material under a 10C (6 minutes) super-high rate charging condition. While realizing 10C fast charging, the material still maintains a high reversible specific capacity, and shows excellent capacity retention rate and structural integrity in a long-term high-rate cycle test, and overcomes the difficulty that fast charging usually accelerates material degradation.

According to the silicon wafer and the forming method of the silicon wafer, the silicon wafer is used for epitaxial growth of a large-scale integrated circuit of a semiconductor device and / or homogeneous and heterogeneous semiconductor materials, the BMD ring is formed in the edge area of the silicon wafer, the BMD ring is located on the inner side of the slippage defect, the BMD ring can effectively pin movement of the slippage defect, and therefore the stability of the silicon wafer is improved. Therefore, the slippage defect on the edge of the silicon wafer is prevented from spreading from the edge of the silicon wafer to the center of the silicon wafer. The pinning effect of the BMD on the slippage defect is related to the density and size of the BMD, and further, when the density of the BMD is larger than E + 8ea / cm < 3 > and the diameter of oxygen precipitation in the BMD is 20-200 nm, the slippage defect is blocked, weakened or even completely not invaded into a silicon wafer by the high-density BMD.