Abstract:
A hydrogen storage material analyzer along with its analysis and activation methods, the hydrogen storage material analyzer including a H 2  absorption-desorption cycling tester, a temperature-programmed desorption spectrometer, a specimen holder and a temperature-controlled furnace. With this hydrogen storage material analyzer, a complete set of instruments can be used to implement simultaneously cyclic hydrogenation-dehydrogenation test and thermodynamic desorption analyses, thus improving the working efficiency and analysis accuracy.

Description:
CROSS-REFERENCE TO RELATED U.S. APPLICATIONS 
       [0001]    Not applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT 
       [0003]    Not applicable. 
       REFERENCE TO AN APPENDIX SUBMITTED ON COMPACT DISC 
       [0004]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0005]    1. Field of the Invention 
         [0006]    The present invention relates generally to a hydrogen storage material analyzer, and more particularly to an innovative one which involves hydrogenation degradation analysis and activation methods. 
         [0007]    2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98. 
         [0008]    Hydrogen technology is extensively applied in the fields of the syntheses of methanol and ammonia, hydrogen engine, hydrogen fuel cell and fossil industries. Hydrogen fuel cells are characterized by higher operating efficiency and zero pollution. 
         [0009]    Due to the advantages of hydrogen technologies, the hydrogen storage materials have gained great attention. For instance, the Ti 25 V 35 Cr 40  hydrogen storage alloy with the reversible hydrogen storage capacity of 1.8 wt. % at room temperature is larger than conventional LaNi 5  hydrogen storage alloy (1.2 wt. %). After adding 0.1% carbon, the hydrogen desorption pressure of Ti 25 V 35 Cr 40  is increased, thus enhancing the effective hydrogen desorption capacity at room temperature about 8-20%. As such, this kind of hydrogen storage alloy has a unique potential of commercialization and academic study. 
         [0010]    The hydrogenation reaction of hydrogen storage material is accompanied by reactive heat. Since the hydrogenation is reversible, a lot of hydrogen gas can be stored, with an exothermic reaction during absorption and endothermic reaction during desorption. Hence, the utilization quality of hydrogen storage material is crucial to its absorption and desorption properties. However, irrespective of the performance of hydrogen storage material, ageing and degradation problems will be encountered over time. Said ageing and degradation phenomenon may be caused by intrinsic microstructure change of hydrogen storage material, or loss of absorption/desorption capability due to the surface covered by the extrinsic impurities in the hydrogen source. In the practice, these problems have to be characterized by specifically designed analyzers, therefore, the hydrogen storage material analyzer plays a decisive role in the development of high performance hydrogen storage material. 
         [0011]    The existing hydrogen storage material analyzers are currently categorized into two types: H 2  absorption-desorption cycling testers, and temperature programmed desorption (TPD) spectrometers. The former one is intended for ageing test through cyclic hydrogen absorption-desorption, while the latter one is devoted to the dehydrogenation thermodynamics of hydrogen storage materials. 
         [0012]    The above two hydrogen storage material analyzers along with their technologies are represented by different functions and significance. However, as these two instruments are operated separately, it is difficult to guarantee consistent analyses of hydrogen storage material, and in other words, the samples must be placed on the cyclic hydrogen absorption-desorption tester in the first phase, and then removed and shifted to TPD for analysis and test in the second phase. In such a case, this will lead to not only inefficient analysis, but also error arising from sample removal, thus affecting the final accuracy and quality of analysis and testing. 
         [0013]    Thus, to overcome the aforementioned problems of the prior art, it would be an advancement if the current art can provide an improved design that can significantly increase the accuracy and efficacy of analysis and testing. 
         [0014]    Therefore, the inventor has provided the present invention of practicability after deliberate experimentation and evaluation based on years of experience in the production, development and design of related products. 
       BRIEF SUMMARY OF THE INVENTION 
       [0015]    Based on the unique configuration of the present invention wherein “the hydrogen storage material analyzer along with its analysis and activation methods” mainly comprises: a H 2  absorption-desorption cycling tester, a temperature-programmed desorption spectrometer, a specimen holder and a temperature-controlled furnace, a complete set of instruments can be used to implement simultaneously cycling desorption test, desorption analysis and activation requirements, thus eliminating the problem of removing the samples to another instrument for the intended purposes. Hence, the present invention presents better working efficiency, higher analysis accuracy and quality. 
         [0016]    Although the invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0017]      FIG. 1  is a schematic view of the hydrogen storage material analyzer of the present invention indicating hydrogen supply of the hydrogen cylinder. 
           [0018]      FIG. 2  is a schematic view of the present invention wherein the specimen valve is opened to guide hydrogen into the specimen holder. 
           [0019]      FIG. 3  is a sectional view of the specimen holder of the present invention indicating the hydrogen absorption state of the hydrogen storage material. 
           [0020]      FIG. 4  is a schematic view of the hydrogen storage material with hydrogen desorption state of the present invention. 
           [0021]      FIG. 5  is a schematic view of the present invention wherein the mass spectrometer is used for desorption analysis of the hydrogen storage material. 
           [0022]      FIG. 6  is a cycling degradation curve of Ti 25 V 35 Cr 40  hydrogen storage material in a hydrogen test (purity 99.9999%). 
           [0023]      FIG. 7  is a comparison view of TPD spectra of Ti 25 V 35 Cr 40  hydrogen storage material before/after 500 cycles. 
           [0024]      FIG. 8  is a PCI curve of Ti 25 V 35 Cr 40  hydrogen storage material before/after 500 cycles. 
           [0025]      FIG. 9(   a ) shows a XRD diffraction pattern of Ti 25 V 35 Cr 40  hydrogen storage material before/after 500 cycles. 
           [0026]      FIG. 9(   b ) show peaks for Ti-rich precipitate tested in a slow diffraction mode (lo/min). 
           [0027]      FIG. 10  shows hydrogenation degradation curves of the hydrogen storage material of the present invention (purity 99.99%). 
           [0028]      FIG. 11(   a ) shows variation of hydrogen absorption pressures of the hydrogen storage material during the cycles. 
           [0029]      FIG. 11(   b ) shows hydrogen desorption pressure of the hydrogen storage material during the cycles. 
           [0030]      FIG. 12  shows a TPD spectra between activated and poisoned alloys after 150 cycles. 
           [0031]      FIG. 13(   a ) shows TPD-MS spectra of poisoned alloys for N 2 /CO. 
           [0032]      FIG. 13(   b ) shows TPD-MS spectra of poisoned alloys for H 2 . 
           [0033]      FIG. 13(   c ) shows TPD-MS spectra of poisoned alloys for H 2 O. 
           [0034]      FIG. 13(   d ) shows TPD-MS spectra of poisoned alloys for H 2 S. 
           [0035]      FIG. 14  is a schematic view of extrinsic hydrogenation degradation of hydrogen storage material in the present invention. 
           [0036]      FIG. 15  shows a comparison of PCI curves of hydrogen storage material in the condition of activated and re-activated in the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0037]      FIGS. 1-2  depict preferred embodiments of a hydrogen storage material analyzer of the present invention along with analysis and activation method, which, however, are provided for only explanatory objective for patent claims. 
         [0038]    Said hydrogen storage material analyzer A comprising: a H 2  absorption-desorption cycling tester  10 , a temperature-programmed desorption spectrometer  20 , a specimen holder  30  and a temperature-controlled furnace  40 . The specimen holder  30  is used to load the hydrogen storage material  50  (marked in  FIGS. 3 ,  4 ). 
         [0039]    The H 2  absorption-desorption cycling tester  10  includes a hydrogen cylinder  11 , a hydrogen reservoir  12  and a hydrogen pipeline  13 . The first end  131  of the hydrogen pipeline  13  is linked to the hydrogen cylinder  11 , and the second end  132  of the hydrogen pipeline  13  is connected to the specimen holder  30 . The first end  131  of the hydrogen pipeline  13  is fitted with an inlet valve  14  to control the on/off state of hydrogen supply from the hydrogen cylinder  11 . The hydrogen reservoir  12  is linked to the hydrogen pipeline  13  via a bypass flow channel  15 . The second end  132  of the hydrogen pipeline  13  is fitted with a specimen valve  17  to control the connection state between the hydrogen pipeline  13  and specimen holder  30 . Moreover, a first pressure gauge  18  is arranged onto the hydrogen pipeline  13  between the specimen valve  17  and inlet valve  14 . 
         [0040]    The temperature-programmed desorption spectrometer  20  includes a hydrogen desorption channel  21 , a vacuum pump  22  and a mass spectrometer  23 . The hydrogen desorption channel  21  is provided with a first end  211  to link the second end  132  of the hydrogen pipeline  13  of the H 2  absorption-desorption cycling tester  10 . The mass spectrometer  23  is linked to the second end  212  of the hydrogen desorption channel  21 . The mass spectrometer  23  is set in front of the vacuum pump  22 . A second pressure gauge  24  is arranged between the vacuum pump  22  and the first end  211  of the hydrogen desorption channel  21 . 
         [0041]    An integrated joint  60  is used to couple the second end  132  of the hydrogen pipeline  13  of the H 2  absorption-desorption cycling tester  10  with the first end  211  of the hydrogen desorption channel  21  of the temperature-programmed desorption spectrometer  20 . Moreover, the integrated joint  60  is provided with a joint valve  61  to control the connection state of the hydrogen pipeline  13  and hydrogen desorption channel  21 . 
         [0042]    Furthermore, the temperature-controlled furnace  40  is used for temperature control of the specimen holder  30 , while the specimen holder  30  is provided with a specimen space  31  (see FIG.  3 ) to load the hydrogen storage material  50 . 
         [0043]    Based on the above-specified structural configuration, the analysis and activation methods for the hydrogen storage material analyzer A are described below: 
         [0044]    First, automatic cycling absorption and desorption methods of the present invention are briefed below: 
         [0045]    The structural configuration of the hydrogen storage material analyzer A of the present invention is shown in  FIG. 1 , wherein the system framework is composed of electronic control unit, hydrogen pipeline and temperature-controlled furnace. Said electronic control unit comprises a personal computer, signal input/output interface card, relay control interface card and electromagnetic valve assembly. As for the hydrogen storage material analyzer A of the present invention, the cyclic absorption and desorption steps are described as follows: 
         [0046]    a. The electromagnetic valve assembly is controlled by a program, and the electromagnetic valve is used to activate the working gas flow (5 kg/cm 2 ) to the designated actuator chamber of pneumatic valve, enabling automatic hydrogen charging and discharge for hydrogen storage material. 
         [0047]    b. Take hydrogen-charging process as a example: the reaction temperature of the hydrogen storage material is controlled at a constant temperature (e.g.: 30 degrees C.). When the inlet valve  14  is opened by a computer, hydrogen H 2  starts to enter into the hydrogen reservoir  12  (see  FIG. 1 ), and the pressure reading is sent back to the computer. When the H 2  pressure conforms to the setting value, the inlet valve  14  is shut down immediately (see  FIG. 2 , represented by blacking), then the specimen valve  17  is opened, allowing hydrogen H 2  to enter into the specimen holder  30 , so that hydrogen storage material  50  (e.g.: hydrogen storage alloy) in the specimen holder  30  starts to absorb hydrogen (see  FIG. 3 ). 
         [0048]    c. When the pressure reading drops over time, the hydrogen storage material  50  starts to absorb hydrogen, during which the kinetics curve is recorded by the computer, and the hydrogen absorption of hydrogen storage material  50  (wt. %) is calculated by the pressure difference. After the absorption reaction is equilibrated, the joint valve  61  of the integrated joint  60  is opened to discharge hydrogen stored in the hydrogen storage alloy (see  FIG. 4 ), thus finishing a cycle of absorption and desorption of hydrogen storage material  50 . 
         [0049]    Additionally, the cyclic hydrogenation-dehydrogenation performance of hydrogen storage material  50  can be measured and monitored by a program-controlled process. 
         [0050]    The analysis and activation methods of the hydrogen storage material of the present invention are described below: 
         [0051]    1. Intrinsic hydrogenation degradation: 
         [0052]    Through programmed operation of on/off for the valves in the H 2  absorption-desorption cycling tester  10  and temperature-programmed desorption spectrometer  20 , hydrogenation degradation of Ti 25 V 35 Cr 40  hydrogen storage material are observed after 500 cycles of absorption and desorption using 6N hydrogen as shown in  FIG. 6 , the degradation is about 16.5%. The hydrogenation degradation mechanism of common alloy is divided into intrinsic and extrinsic degradation. To further analyze 16.5% hydrogenation degradation of Ti 25 V 35 Cr 40  hydrogen storage material, extrinsic degradation must be firstly considered; after 500 cycles of test, long-lasting dehydrogenation at room temperature is conducted, allowing the hydrogen storage material to be as β hydride within the specimen holder  30 . The TPD spectrum in this state is shown in  FIG. 7 , wherein the TPD curve of β hydride before/after cycling differs little, thus demonstrating that the extrinsic factors to degrade hydrogen storage material are eliminated. 
         [0053]    Hydrogenation degradation of Ti 25 V 35 Cr 40  hydrogen storage material after 500 cycles of test is caused by intrinsic factors as indicated by the variation of PCI (Pressure-Composition-Isotherm) curve in  FIG. 8 . Maximum hydrogen absorption of hydrogen storage material drops from 3.52 wt. % to 3.23 wt. %, with a degradation about 8.2%, and the hydrogen pressure within the specimen holder  30  rises. Besides, it is found from XRD diffraction experiment that (see  FIG. 9 ), for the hydrogen storage material after 500 cycles of test, the diffraction angle shifts towards a higher angle, showing the reduction of lattice constant, and accounting for the rising flat pressure of absorption. Meanwhile, minor diffraction peak (see  FIG. 9 ) occurs nearby 2θ=38.5° and 40°, and is assigned as Ti-rich precipitate. As the radius of titanium, vanadium and chrome is 0.145, 0.132 and 0.125 nm, respectively, the formation of this precipitate will lead to reduction of both titanium concentration within Ti 25 V 35 Cr 40  matrix and Ti 25 V 35 Cr 40  lattice constant. 
         [0054]    2. Extrinsic hydrogenation degradation: 
         [0055]    Extrinsic hydrogenation degradation is tested by taking 5N hydrogen as gas source or by adding toxic microelement CO, H 2 S, CO 2 , H 2 O, etc, and then the degradation of Ti 25 V 35 Cr 40  alloy reacting with hydrogen source of lower purity is observed. The resulting findings are shown in  FIG. 10 , wherein after 33 cycles of tests, serious hydrogenation degradation of Ti 25 V 35 Cr 40  hydrogen storage material occurs (down from 1.6 wt. % to 0 wt. %). 
         [0056]    To understand the reason of degradation, the cycling hydrogenation properties including the hydrogen absorption/desorption pressure as function of cycle are monitored shown in  FIG. 11 . It is found that, the hydrogen absorption stops gradually over time, showing that serious degradation of hydrogen storage material occurs or hydrogen desorption is disabled due to obstruction. On the other hand, as shown in  FIG. 12 , it is observed from degraded alloy&#39;s TPD spectrum (TPD spectrum is generated by the second pressure gauge  24  of temperature-programmed desorption spectrometer  20 ) that, there is not any dehydrogenation signal from room temperature to 160° C., but there are two dehydrogenation peaks at about 210° C. and 300° C., representing dehydrogenation of titanium alloy&#39;s δ→β and β→α hydride. As the former one&#39;s, appropriate dehydrogenation temperature is room temperature and it can be seen that poisoning of hydrogen storage alloy may occur in such case. Thus, loss of hydrogen absorption/desorption capability is attributed to the surface of hydrogen storage material covered by impurities in the hydrogen source. Moreover, it is proved that dehydrogenation temperature ofpoisoned Ti 25 V 35 Cr 40  is 160° C. Hence, re-activation temperature ofpoisoned hydrogen storage material should be set above this temperature. 
         [0057]    Toxic substance is originated from impurities from hydrogen source, impeding the formation of hydride by reacting hydrogen with alloy. Referring also to  FIG. 13 , it is found from TPD-MS spectra (this signal is generated by mass spectrometer of temperature-programmed desorption spectrometer), with the temperature rise of hydrogen storage material, some substances, such as: H 2 , H 2  O, CO, O 2  and H 2  S, are desorbed from the surface. It is clear that hydrogenation poisoning of hydrogen storage material is caused from the alloy surface covered by toxic substance (see  FIG. 14 ), thus reducing greatly the hydrogenation capability of hydrogen storage material. Meanwhile, dissociation temperature of TPD-MS spectra is defined as the dehydrogenation temperature of poisoned hydrogen storage material, and re-activation temperature of poisoned hydrogen storage material will be above this temperature. After temperature programmed dehydrogenation, a PCI curve (see  FIG. 15 ) of the degraded hydrogen storage material is observed, showing that the flat pressure and maximum absorption, etc, are the same with original alloy. Thus, it is judged that hydrogenation degradation of the hydrogen storage material is not derived from the change of microstructure. 
         [0058]    3. Re-activation of hydrogen storage material: (see  FIG. 5 ) 
         [0059]    After extrinsic hydrogenation degradation of the hydrogen storage material is confirmed, it is required to shut down the inlet valve  14  for the first end  131  of the hydrogen pipeline  13 , and open the joint valve  61  for the first end  211  of the hydrogen desorption channel  21 , then start the temperature-controlled furnace  40  to heat up the specimen holder  30 . Moreover, the heating temperature is controlled over a dehydrogenation temperature, e.g.: 160° C., so as to dispel toxic substances covered on the surface of the hydrogen storage material. Next, the vacuum pump  22  of the temperature-programmed desorption spectrometer  20  is started to discharge the toxic substances for reactivation of the hydrogen storage material.